radial hydraulic pump free sample

Pumps are mechanical devices used to create fluid flow. There are many different kinds of pumps, from a basic hand pump to vacuum pumps. Many pumps are identified by what they do, for example, boiler feed pumps, pressure washer pumps, and windshield washer pumps, and the intended application is a useful attribute for narrowing down pumps meant for specific applications. This article looks at a particular type of piston pump, the radial piston pump.

Piston pumps are durable and relatively simple devices. A basic piston pump is made up of a piston, a chamber, and two valves. The pump operates by driving the piston down into the chamber, thereby compressing the media inside. In a hydraulic pump, this is some sort of fluid, often water or oil. Once the pressure of the fluid exceeds that of the outlet valve spring, the compressed media goes through the open outlet valve. When the piston is drawn back up, it opens the inlet valve and closes the outlet valve, thereby utilizing suction to draw in new media for compression.

Although somewhat expensive, piston pumps are among the most efficient types of pumps. They have an excellent pressure rating (as high as 10,000 psi), but their design makes them susceptible to contaminants. They provide an excellent solution for many high-pressure hydraulic oil pumping applications. Hydraulic Pumps are any of a class of positive displacement machines used in fluid power applications to provide hydraulic flow to fluid-powered devices such as cylinders, rams, motors, and other devices.

A radial piston pump is a type of hydraulic piston pump. The working pistons extend in a radial direction symmetrically around the shaft, marking the main difference beween them and another piston pump, the axial piston pump, which has axially rotating pistons.

Radial piston pumps arrange a series of pistons radially in a cylindrical block around a rotor hub. The block consists of a pintle, a cylinder barrel with pistons, and a rotor. The pintle directs the fluid in and out of the cylinder. The rotor, mounted eccentrically in the pump housing, forces the pistons in and out of cylinders as it rotates, which cause hydraulic fluid to be sucked into the cylinder cavity and then be discharged from it. Inlets and outlets for the pump are located in a valve in a central hub. Each piston is connected to inlet port when it starts extending while it is connected to the outlet port when start retracting.

An alternative design places inlets and outlets around the perimeter of the pump housing. Radial piston pumps can be purchased as fixed- or variable-displacement models. In the variable-displacement version, the eccentricity of the rotor in the pump housing is altered to decrease or increase the stroke of the pistons.

They have many advantages, such as high efficiency, high-pressure capability up to 1,000 bar or 14000 psi, low flow and pressure ripple, low noise level, very high load at the lowest speed, and high reliability. A disadvantage is that they are bigger than axial pumps, because of the bigger radial dimensions, and so cannot always be used in applications with space constraints.

The hydrostatically balanced parts of radial piston pumps make it possible to use them with various hydraulic fluids such as mineral oil, biodegradable oil, HFC (water-glycol), HFD (synthetic ester), HFA (oil in water), and cutting emulsion. Radial pumps are used for machine tools, such as the displacement of cutting emulsion, and as a supply for hydraulic equipment like cylinders. They are also used in high-pressure units (HPU) for overload protection, and for test rigs.

The automotive sector uses them for automatic transmission and hydraulic suspension control in upper-class cars. Radial piston pumps are also used in plastic- and powder injection molding and wind energy.

This guide provides a basic understanding of radial piston pumps. To find out more about other types of pumps, read our guide here. For more information on related products, consult our other product guides or visit the Thomas Supplier Discovery Platform to locate potential sources or view details on specific products.

A radial piston pump is a form of hydraulic pump. The working pistons extend in a radial direction symmetrically around the drive shaft, in contrast to the axial piston pump.

When filling the workspace of the pumping pistons from "inside" (e.g., over a hollow shaft) it is called an inside impinged (but outside braced) radial piston pump (picture 1). If the workspace is filled from "outside" it"s called an outside impinged radial piston pump (but inside braced) (picture 2).

The outer ring for bracing of the pumping pistons is in eccentric position to the hollow shaft in the center. This eccentricity determines the stroke of the pumping piston.

The piston starts in the inner dead center (IDC) with suction process. After a rotation angle of 180° it is finished and the workspace of the piston is filled with the moved medium. The piston is now in the outer dead center (ODC). From this point on the piston displaces the previously sucked medium in the pressure channel of the pump.

A disadvantage is the bigger radial dimensions in comparison to the axial piston pump, but it could be compensated with the shorter construction in axial direction.

Due to the hydrostatically balanced parts it is possible to use the pump with various hydraulic fluids like mineral oil, biodegradable oil, HFA (oil in water), HFC (water-glycol), HFD (synthetic ester) or cutting emulsion. That implies the following main applications for a radial piston pump:

"Variable Stroke Radial Piston Pump", T.S. Patriot State Engineering Manual, Massachusetts Maritime Academy, 1996, pp. 234–241, retrieved 14 September 2022

Hydraulic pumps are mechanisms in hydraulic systems that move hydraulic fluid from point to point initiating the production of hydraulic power. Hydraulic pumps are sometimes incorrectly referred to as “hydrolic” pumps.

They are an important device overall in the hydraulics field, a special kind of power transmission which controls the energy which moving fluids transmit while under pressure and change into mechanical energy. Other kinds of pumps utilized to transmit hydraulic fluids could also be referred to as hydraulic pumps. There is a wide range of contexts in which hydraulic systems are applied, hence they are very important in many commercial, industrial, and consumer utilities.

“Power transmission” alludes to the complete procedure of technologically changing energy into a beneficial form for practical applications. Mechanical power, electrical power, and fluid power are the three major branches that make up the power transmission field. Fluid power covers the usage of moving gas and moving fluids for the transmission of power. Hydraulics are then considered as a sub category of fluid power that focuses on fluid use in opposition to gas use. The other fluid power field is known as pneumatics and it’s focused on the storage and release of energy with compressed gas.

"Pascal"s Law" applies to confined liquids. Thus, in order for liquids to act hydraulically, they must be contained within a system. A hydraulic power pack or hydraulic power unit is a confined mechanical system that utilizes liquid hydraulically. Despite the fact that specific operating systems vary, all hydraulic power units share the same basic components. A reservoir, valves, a piping/tubing system, a pump, and actuators are examples of these components. Similarly, despite their versatility and adaptability, these mechanisms work together in related operating processes at the heart of all hydraulic power packs.

The hydraulic reservoir"s function is to hold a volume of liquid, transfer heat from the system, permit solid pollutants to settle, and aid in releasing moisture and air from the liquid.

Mechanical energy is changed to hydraulic energy by the hydraulic pump. This is accomplished through the movement of liquid, which serves as the transmission medium. All hydraulic pumps operate on the same basic principle of dispensing fluid volume against a resistive load or pressure.

Hydraulic valves are utilized to start, stop, and direct liquid flow in a system. Hydraulic valves are made of spools or poppets and can be actuated hydraulically, pneumatically, manually, electrically, or mechanically.

The end result of Pascal"s law is hydraulic actuators. This is the point at which hydraulic energy is transformed back to mechanical energy. This can be accomplished by using a hydraulic cylinder to transform hydraulic energy into linear movement and work or a hydraulic motor to transform hydraulic energy into rotational motion and work. Hydraulic motors and hydraulic cylinders, like hydraulic pumps, have various subtypes, each meant for specific design use.

The essence of hydraulics can be found in a fundamental physical fact: fluids are incompressible. (As a result, fluids more closely resemble solids than compressible gasses) The incompressible essence of fluid allows it to transfer force and speed very efficiently. This fact is summed up by a variant of "Pascal"s Principle," which states that virtually all pressure enforced on any part of a fluid is transferred to every other part of the fluid. This scientific principle states, in other words, that pressure applied to a fluid transmits equally in all directions.

Furthermore, the force transferred through a fluid has the ability to multiply as it moves. In a slightly more abstract sense, because fluids are incompressible, pressurized fluids should keep a consistent pressure just as they move. Pressure is defined mathematically as a force acting per particular area unit (P = F/A). A simplified version of this equation shows that force is the product of area and pressure (F = P x A). Thus, by varying the size or area of various parts inside a hydraulic system, the force acting inside the pump can be adjusted accordingly (to either greater or lesser). The need for pressure to remain constant is what causes force and area to mirror each other (on the basis of either shrinking or growing). A hydraulic system with a piston five times larger than a second piston can demonstrate this force-area relationship. When a force (e.g., 50lbs) is exerted on the smaller piston, it is multiplied by five (e.g., 250 lbs) and transmitted to the larger piston via the hydraulic system.

Hydraulics is built on fluids’ chemical properties and the physical relationship between pressure, area, and force. Overall, hydraulic applications allow human operators to generate and exert immense mechanical force with little to no physical effort. Within hydraulic systems, both oil and water are used to transmit power. The use of oil, on the other hand, is far more common, owing in part to its extremely incompressible nature.

Pressure relief valves prevent excess pressure by regulating the actuators’ output and redirecting liquid back to the reservoir when necessary. Directional control valves are used to change the size and direction of hydraulic fluid flow.

While hydraulic power transmission is remarkably useful in a wide range of professional applications, relying solely on one type of power transmission is generally unwise. On the contrary, the most efficient strategy is to combine a wide range of power transmissions (pneumatic, hydraulic, mechanical, and electrical). As a result, hydraulic systems must be carefully embedded into an overall power transmission strategy for the specific commercial application. It is necessary to invest in locating trustworthy and skilled hydraulic manufacturers/suppliers who can aid in the development and implementation of an overall hydraulic strategy.

The intended use of a hydraulic pump must be considered when selecting a specific type. This is significant because some pumps may only perform one function, whereas others allow for greater flexibility.

The pump"s material composition must also be considered in the application context. The cylinders, pistons, and gears are frequently made of long-lasting materials like aluminum, stainless steel, or steel that can withstand the continuous wear of repeated pumping. The materials must be able to withstand not only the process but also the hydraulic fluids. Composite fluids frequently contain oils, polyalkylene glycols, esters, butanol, and corrosion inhibitors (though water is used in some instances). The operating temperature, flash point, and viscosity of these fluids differ.

In addition to material, manufacturers must compare hydraulic pump operating specifications to make sure that intended utilization does not exceed pump abilities. The many variables in hydraulic pump functionality include maximum operating pressure, continuous operating pressure, horsepower, operating speed, power source, pump weight, and maximum fluid flow. Standard measurements like length, rod extension, and diameter should be compared as well. Because hydraulic pumps are used in lifts, cranes, motors, and other heavy machinery, they must meet strict operating specifications.

It is critical to recall that the overall power generated by any hydraulic drive system is influenced by various inefficiencies that must be considered in order to get the most out of the system. The presence of air bubbles within a hydraulic drive, for example, is known for changing the direction of the energy flow inside the system (since energy is wasted on the way to the actuators on bubble compression). Using a hydraulic drive system requires identifying shortfalls and selecting the best parts to mitigate their effects. A hydraulic pump is the "generator" side of a hydraulic system that initiates the hydraulic procedure (as opposed to the "actuator" side that completes the hydraulic procedure). Regardless of disparities, all hydraulic pumps are responsible for displacing liquid volume and transporting it to the actuator(s) from the reservoir via the tubing system. Some form of internal combustion system typically powers pumps.

While the operation of hydraulic pumps is normally the same, these mechanisms can be split into basic categories. There are two types of hydraulic pumps to consider: gear pumps and piston pumps. Radial and axial piston pumps are types of piston pumps. Axial pumps produce linear motion, whereas radial pumps can produce rotary motion. The gear pump category is further subdivided into external gear pumps and internal gear pumps.

Each type of hydraulic pump, regardless of piston or gear, is either double-action or single-action. Single-action pumps can only pull, push, or lift in one direction, while double-action pumps can pull, push, or lift in multiple directions.

Vane pumps are positive displacement pumps that maintain a constant flow rate under varying pressures. It is a pump that self-primes. It is referred to as a "vane pump" because the effect of the vane pressurizes the liquid.

This pump has a variable number of vanes mounted onto a rotor that rotates within the cavity. These vanes may be variable in length and tensioned to maintain contact with the wall while the pump draws power. The pump also features a pressure relief valve, which prevents pressure rise inside the pump from damaging it.

Internal gear pumps and external gear pumps are the two main types of hydraulic gear pumps. Pumps with external gears have two spur gears, the spurs of which are all externally arranged. Internal gear pumps also feature two spur gears, and the spurs of both gears are internally arranged, with one gear spinning around inside the other.

Both types of gear pumps deliver a consistent amount of liquid with each spinning of the gears. Hydraulic gear pumps are popular due to their versatility, effectiveness, and fairly simple design. Furthermore, because they are obtainable in a variety of configurations, they can be used in a wide range of consumer, industrial, and commercial product contexts.

Hydraulic ram pumps are cyclic machines that use water power, also referred to as hydropower, to transport water to a higher level than its original source. This hydraulic pump type is powered solely by the momentum of moving or falling water.

Ram pumps are a common type of hydraulic pump, especially among other types of hydraulic water pumps. Hydraulic ram pumps are utilized to move the water in the waste management, agricultural, sewage, plumbing, manufacturing, and engineering industries, though only about ten percent of the water utilized to run the pump gets to the planned end point.

Despite this disadvantage, using hydropower instead of an external energy source to power this kind of pump makes it a prominent choice in developing countries where the availability of the fuel and electricity required to energize motorized pumps is limited. The use of hydropower also reduces energy consumption for industrial factories and plants significantly. Having only two moving parts is another advantage of the hydraulic ram, making installation fairly simple in areas with free falling or flowing water. The water amount and the rate at which it falls have an important effect on the pump"s success. It is critical to keep this in mind when choosing a location for a pump and a water source. Length, size, diameter, minimum and maximum flow rates, and speed of operation are all important factors to consider.

Hydraulic water pumps are machines that move water from one location to another. Because water pumps are used in so many different applications, there are numerous hydraulic water pump variations.

Water pumps are useful in a variety of situations. Hydraulic pumps can be used to direct water where it is needed in industry, where water is often an ingredient in an industrial process or product. Water pumps are essential in supplying water to people in homes, particularly in rural residences that are not linked to a large sewage circuit. Water pumps are required in commercial settings to transport water to the upper floors of high rise buildings. Hydraulic water pumps in all of these situations could be powered by fuel, electricity, or even by hand, as is the situation with hydraulic hand pumps.

Water pumps in developed economies are typically automated and powered by electricity. Alternative pumping tools are frequently used in developing economies where dependable and cost effective sources of electricity and fuel are scarce. Hydraulic ram pumps, for example, can deliver water to remote locations without the use of electricity or fuel. These pumps rely solely on a moving stream of water’s force and a properly configured number of valves, tubes, and compression chambers.

Electric hydraulic pumps are hydraulic liquid transmission machines that use electricity to operate. They are frequently used to transfer hydraulic liquid from a reservoir to an actuator, like a hydraulic cylinder. These actuation mechanisms are an essential component of a wide range of hydraulic machinery.

There are several different types of hydraulic pumps, but the defining feature of each type is the use of pressurized fluids to accomplish a job. The natural characteristics of water, for example, are harnessed in the particular instance of hydraulic water pumps to transport water from one location to another. Hydraulic gear pumps and hydraulic piston pumps work in the same way to help actuate the motion of a piston in a mechanical system.

Despite the fact that there are numerous varieties of each of these pump mechanisms, all of them are powered by electricity. In such instances, an electric current flows through the motor, which turns impellers or other devices inside the pump system to create pressure differences; these differential pressure levels enable fluids to flow through the pump. Pump systems of this type can be utilized to direct hydraulic liquid to industrial machines such as commercial equipment like elevators or excavators.

Hydraulic hand pumps are fluid transmission machines that utilize the mechanical force generated by a manually operated actuator. A manually operated actuator could be a lever, a toggle, a handle, or any of a variety of other parts. Hydraulic hand pumps are utilized for hydraulic fluid distribution, water pumping, and various other applications.

Hydraulic hand pumps may be utilized for a variety of tasks, including hydraulic liquid direction to circuits in helicopters and other aircraft, instrument calibration, and piston actuation in hydraulic cylinders. Hydraulic hand pumps of this type use manual power to put hydraulic fluids under pressure. They can be utilized to test the pressure in a variety of devices such as hoses, pipes, valves, sprinklers, and heat exchangers systems. Hand pumps are extraordinarily simple to use.

Each hydraulic hand pump has a lever or other actuation handle linked to the pump that, when pulled and pushed, causes the hydraulic liquid in the pump"s system to be depressurized or pressurized. This action, in the instance of a hydraulic machine, provides power to the devices to which the pump is attached. The actuation of a water pump causes the liquid to be pulled from its source and transferred to another location. Hydraulic hand pumps will remain relevant as long as hydraulics are used in the commerce industry, owing to their simplicity and easy usage.

12V hydraulic pumps are hydraulic power devices that operate on 12 volts DC supplied by a battery or motor. These are specially designed processes that, like all hydraulic pumps, are applied in commercial, industrial, and consumer places to convert kinetic energy into beneficial mechanical energy through pressurized viscous liquids. This converted energy is put to use in a variety of industries.

Hydraulic pumps are commonly used to pull, push, and lift heavy loads in motorized and vehicle machines. Hydraulic water pumps may also be powered by 12V batteries and are used to move water out of or into the desired location. These electric hydraulic pumps are common since they run on small batteries, allowing for ease of portability. Such portability is sometimes required in waste removal systems and vehiclies. In addition to portable and compact models, options include variable amp hour productions, rechargeable battery pumps, and variable weights.

While non rechargeable alkaline 12V hydraulic pumps are used, rechargeable ones are much more common because they enable a continuous flow. More considerations include minimum discharge flow, maximum discharge pressure, discharge size, and inlet size. As 12V batteries are able to pump up to 150 feet from the ground, it is imperative to choose the right pump for a given use.

Air hydraulic pumps are hydraulic power devices that use compressed air to stimulate a pump mechanism, generating useful energy from a pressurized liquid. These devices are also known as pneumatic hydraulic pumps and are applied in a variety of industries to assist in the lifting of heavy loads and transportation of materials with minimal initial force.

Air pumps, like all hydraulic pumps, begin with the same components. The hydraulic liquids, which are typically oil or water-based composites, require the use of a reservoir. The fluid is moved from the storage tank to the hydraulic cylinder via hoses or tubes connected to this reservoir. The hydraulic cylinder houses a piston system and two valves. A hydraulic fluid intake valve allows hydraulic liquid to enter and then traps it by closing. The discharge valve is the point at which the high pressure fluid stream is released. Air hydraulic pumps have a linked air cylinder in addition to the hydraulic cylinder enclosing one end of the piston.

The protruding end of the piston is acted upon by a compressed air compressor or air in the cylinder. When the air cylinder is empty, a spring system in the hydraulic cylinder pushes the piston out. This makes a vacuum, which sucks fluid from the reservoir into the hydraulic cylinder. When the air compressor is under pressure, it engages the piston and pushes it deeper into the hydraulic cylinder and compresses the liquids. This pumping action is repeated until the hydraulic cylinder pressure is high enough to forcibly push fluid out through the discharge check valve. In some instances, this is connected to a nozzle and hoses, with the important part being the pressurized stream. Other uses apply the energy of this stream to pull, lift, and push heavy loads.

Hydraulic piston pumps transfer hydraulic liquids through a cylinder using plunger-like equipment to successfully raise the pressure for a machine, enabling it to pull, lift, and push heavy loads. This type of hydraulic pump is the power source for heavy-duty machines like excavators, backhoes, loaders, diggers, and cranes. Piston pumps are used in a variety of industries, including automotive, aeronautics, power generation, military, marine, and manufacturing, to mention a few.

Hydraulic piston pumps are common due to their capability to enhance energy usage productivity. A hydraulic hand pump energized by a hand or foot pedal can convert a force of 4.5 pounds into a load-moving force of 100 pounds. Electric hydraulic pumps can attain pressure reaching 4,000 PSI. Because capacities vary so much, the desired usage pump must be carefully considered. Several other factors must also be considered. Standard and custom configurations of operating speeds, task-specific power sources, pump weights, and maximum fluid flows are widely available. Measurements such as rod extension length, diameter, width, and height should also be considered, particularly when a hydraulic piston pump is to be installed in place of a current hydraulic piston pump.

Hydraulic clutch pumps are mechanisms that include a clutch assembly and a pump that enables the user to apply the necessary pressure to disengage or engage the clutch mechanism. Hydraulic clutches are crafted to either link two shafts and lock them together to rotate at the same speed or detach the shafts and allow them to rotate at different speeds as needed to decelerate or shift gears.

Hydraulic pumps change hydraulic energy to mechanical energy. Hydraulic pumps are particularly designed machines utilized in commercial, industrial, and residential areas to generate useful energy from different viscous liquids pressurization. Hydraulic pumps are exceptionally simple yet effective machines for moving fluids. "Hydraulic" is actually often misspelled as "Hydralic". Hydraulic pumps depend on the energy provided by hydraulic cylinders to power different machines and mechanisms.

There are several different types of hydraulic pumps, and all hydraulic pumps can be split into two primary categories. The first category includes hydraulic pumps that function without the assistance of auxiliary power sources such as electric motors and gas. These hydraulic pump types can use the kinetic energy of a fluid to transfer it from one location to another. These pumps are commonly called ram pumps. Hydraulic hand pumps are never regarded as ram pumps, despite the fact that their operating principles are similar.

The construction, excavation, automotive manufacturing, agriculture, manufacturing, and defense contracting industries are just a few examples of operations that apply hydraulics power in normal, daily procedures. Since hydraulics usage is so prevalent, hydraulic pumps are unsurprisingly used in a wide range of machines and industries. Pumps serve the same basic function in all contexts where hydraulic machinery is used: they transport hydraulic fluid from one location to another in order to generate hydraulic energy and pressure (together with the actuators).

Elevators, automotive brakes, automotive lifts, cranes, airplane flaps, shock absorbers, log splitters, motorboat steering systems, garage jacks and other products use hydraulic pumps. The most common application of hydraulic pumps in construction sites is in big hydraulic machines and different types of "off-highway" equipment such as excavators, dumpers, diggers, and so on. Hydraulic systems are used in other settings, such as offshore work areas and factories, to power heavy machinery, cut and bend material, move heavy equipment, and so on.

Fluid’s incompressible nature in hydraulic systems allows an operator to make and apply mechanical power in an effective and efficient way. Practically all force created in a hydraulic system is applied to the intended target.

Because of the relationship between area, pressure, and force (F = P x A), modifying the force of a hydraulic system is as simple as changing the size of its components.

Hydraulic systems can transfer energy on an equal level with many mechanical and electrical systems while being significantly simpler in general. A hydraulic system, for example, can easily generate linear motion. On the contrary, most electrical and mechanical power systems need an intermediate mechanical step to convert rotational motion to linear motion.

Hydraulic systems are typically smaller than their mechanical and electrical counterparts while producing equivalents amounts of power, providing the benefit of saving physical space.

Hydraulic systems can be used in a wide range of physical settings due to their basic design (a pump attached to actuators via some kind of piping system). Hydraulic systems could also be utilized in environments where electrical systems would be impractical (for example underwater).

By removing electrical safety hazards, using hydraulic systems instead of electrical power transmission improves relative safety (for example explosions, electric shock).

The amount of power that hydraulic pumps can generate is a significant, distinct advantage. In certain cases, a hydraulic pump could generate ten times the power of an electrical counterpart. Some hydraulic pumps (for example, piston pumps) cost more than the ordinary hydraulic component. These drawbacks, however, can be mitigated by the pump"s power and efficiency. Despite their relatively high cost, piston pumps are treasured for their strength and capability to transmit very viscous fluids.

Handling hydraulic liquids is messy, and repairing leaks in a hydraulic pump can be difficult. Hydraulic liquid that leaks in hot areas may catch fire. Hydraulic lines that burst may cause serious injuries. Hydraulic liquids are corrosive as well, though some are less so than others. Hydraulic systems need frequent and intense maintenance. Parts with a high factor of precision are frequently required in systems. If the power is very high and the pipeline cannot handle the power transferred by the liquid, the high pressure received by the liquid may also cause work accidents.

Even though hydraulic systems are less complex than electrical or mechanical systems, they are still complex systems that should be handled with caution. Avoiding physical contact with hydraulic systems is an essential safety precaution when engaging with them. Even when a hydraulic machine is not in use, active liquid pressure within the system can be a hazard.

Inadequate pumps can cause mechanical failure in the place of work that can have serious and costly consequences. Although pump failure has historically been unpredictable, new diagnostic technology continues to improve on detecting methods that previously relied solely on vibration signals. Measuring discharge pressures enables manufacturers to forecast pump wear more accurately. Discharge sensors are simple to integrate into existing systems, increasing the hydraulic pump"s safety and versatility.

Hydraulic pumps are devices in hydraulic systems that move hydraulic fluid from point to point, initiating hydraulic power production. They are an important device overall in the hydraulics field, a special kind of power transmission that controls the energy which moving fluids transmit while under pressure and change into mechanical energy. Hydraulic pumps are divided into two categories namely gear pumps and piston pumps. Radial and axial piston pumps are types of piston pumps. Axial pumps produce linear motion, whereas radial pumps can produce rotary motion. The construction, excavation, automotive manufacturing, agriculture, manufacturing, and defense contracting industries are just a few examples of operations that apply hydraulics power in normal, daily procedures.

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In prior art there is known a radial piston hydraulic motor design in which a cam ring is connected to a box frame. The cam ring is a wave-shaped structure, and pistons connected to a non-revolving piston frame can be pressed one after another against the inner surface of the wave-shaped structure. Some of the pistons are in a working phase and some of them in a return phase. The supply of oil into the piston frame is regulated through a distributor valve, which revolves with the box frame. The piston frame is connected with the central non-revolving central shaft.

This application discloses a radial piston hydraulic motor design in which a neutral position valve, i.e. a free rotation valve, is integrated inside a radial piston hydraulic motor. Said free rotation valve enables the hydraulic motor to be disengaged for free rotation and again engaged for operation. In that connection, a separate free rotation valve outside the hydraulic motor is not needed.

In accordance with the invention, the valve is constructed in the frame of the radial piston hydraulic motor itself and, in the embodiment shown in the figures, in the central shaft thereof. The central shaft includes a spindle cavity for a separate movable spindle. In accordance with the invention, a spring is provided at the end of the spindle placed in the spindle cavity, so that control pressure can be passed to the end of the spindle. When control pressure is passed to the end of the spindle, said spindle can be moved to different positions in the spindle cavity. One position provides a neutral state in accordance with the invention, in which state the inlet line and the return line of working pressure are blocked and in which state the springs connected with the pistons have pressed the pistons to the bottom position, so that the piston rollers connected to the pistons are spaced from the wave-shaped cam ring.

In the most general embodiment of the invention, the free rotation valve including a spindle in accordance with the invention can be generally used in a radial piston hydraulic motor that includes a piston frame, a central shaft, a box frame and a distributor valve. The invention can relate to a radial piston hydraulic motor in which the box frame is rotated or to a radial piston hydraulic motor in which the box frame is in a fixed position and the central shaft is rotated. In accordance with the invention, the spindle blocks the pressure lines in a free rotation situation and in the arrangement in accordance with the invention, in a free rotation situation, both the working phase passages and the return phase passages leading from the pistons are connected in series with one another and, advantageously, said series connection is additionally in hydraulic fluid communication with the box frame. Thus, by means of the valve in accordance with the invention and by operating it, the working pressure line and the return pressure line are blocked in a free rotation situation. In accordance with the invention, said blocking takes place inside the radial piston hydraulic motor by operating the spindle of the neutral position valve placed in the radial piston hydraulic motor so that its shoulders block the inlet line of working pressure and its return line, i.e. outlet line in a free rotation situation. The lines are also called passages.

The radial piston hydraulic motor and the method in the control of the radial piston hydraulic motor according to the invention are characterized by what is stated in the claims.

FIG. 2 shows the radial piston hydraulic motor in accordance with the invention at the stage where the motor is engaged to drive. The illustration is a sectional view.

FIG. 5A shows a second embodiment of the spindle in a position in which no control pressure has been passed to a passage C and in which a spring keeps the spindle in a position in which the radial piston hydraulic motor drives.

FIG. 5B shows a stage in which control pressure has been passed into the passage C and the radial piston hydraulic motor is in a free rotation situation.

If there is no control pressure in a passage C, a radial piston hydraulic motor 100 is in a free rotation state. In that connection, a spindle 19 is in an extreme position on the left by the action of a spring 21, so that both an inlet line, i.e. a pressure passage B, and a return passage A of working pressure are blocked and pistons 13 a 1, 13 a 2. . . are at the bottom, with the result that a box frame 10 of the radial piston hydraulic motor 100 can be rotated freely by external force, i.e. the radial piston hydraulic motor 100 is, so to speak, freely rotatable. The passages can also be called lines.

FIG. 1 shows the radial piston hydraulic motor 100 in accordance with the invention in a free rotation situation. The main parts of the radial piston hydraulic motor 100 in accordance with the invention are described based on FIG. 1. The radial piston hydraulic motor 100 illustrated in the figure is shown as a longitudinal sectional view. The radial piston hydraulic motor 100 includes a box frame 10. A cam ring 11 revolving with the revolving box frame 10 is connected to said revolving box frame. A non-revolving piston frame 12 includes the pistons 13 a 1, 13 a 2. . . , each piston 13 a 1, 13 a 2including a press wheel or a press roller 14 a 1, 14 a 2. . . , which can be pressed by means of the pressure of a hydraulic fluid, such as hydraulic oil, against an inner surface 11′ of the cam ring 11. The cam ring 11 is a wave-shaped structure, so that when the piston 13 a 1, 13 a 2. . . with its press wheel 14 a 1, 14 a 2. . . is pressed with force against the cam ring 11, the press wheel conforms to the shape of the cam ring and thus rotates, with a desired force, the cam ring 11 and the box frame 10 associated therewith and further, for example, a wheel of a vehicle or another object to the driven.

The figure shows a bearing 15 and a bearing 16 by means of which the box frame 10 is arranged to rotate with respect to a central shaft 17. The central shaft 17 is a non-revolving shaft. A distributor valve 18 is connected to the box frame 10 and rotates therewith. The distributor valve 18 includes bores 23 from one frontal face thereof to another and further to the pistons 13 a 1, 13 a 2. . . , to the cylinder spaces of the pistons, through passages 22 situated in the piston frame 12, which passages allow working pressure to be transferred, as desired, from the passage B to the piston 13 a 1, 13 a 2. . . which is in the working phase at each particular time and through which distributor valve 18 a hydraulic fluid, such as hydraulic oil, can be passed from the pistons 13 a 1, 13 a 2. . . which are in the return phase to return circulation and to the return passage A. The device arrangement comprises a so-called free rotation valve 50. The control spindle 19 of the free rotation valve 50 in accordance with the invention is placed in a spindle cavity 20 in the centre of the central shaft 17. The control spindle 19 includes shoulder portions t1, t2, t3, t4and axial portions p1, p2, p3, p4of a smaller cross-section between them. Around the axial portion p4there is a spring 21, the spindle 19 being moved against the force of said spring by means of a pressure provided at the end of the spindle from the control pressure passage C. A passage 22 leads from each piston 13 a 1, 13 a 2. . . to the distributor valve 18 and further in connection with the distributor valve 18 there are passages 23 opening into an annular groove 24 asituated on the outer surface of the shaft 17. In the figure, the pressure passages are denoted with the letters B and D and the return passages are denoted with the letters E and A. The passage E is connected with an axial passage F which is connected with a passage G opening into the end of the spindle cavity 20. The passage E is a radial passage and it also opens at its end into the spindle cavity 20. Between the passages B and D there is a wall 25, a so-called partition wall. The passages B and D open into the spindle cavity 20. When the shoulder t2of the spindle 19 is at the wall 25, the passages A and B are, so to speak, blocked with respect to each other, i.e. flow communication between them is prevented and the box frame 10 of the radial piston hydraulic motor 100 can be rotated freely. In that connection, springs U1, U2. . . have pressed the press wheels 14 a 1, 14 a 2of the pistons 13 a 1, 13 a 2. . . to the bottom position, so that the press wheels 14 a 1, 14 a 2. . . are spaced from the cam ring 11. The passages D and E and the inlet passages and return passages 23 of the distributor valve 18 then communicate in series with one another. The shoulder t3of the spindle 19 prevents the space between the shoulders t2and t3from being in communication with the return passage A. The shoulder t2prevents communication with the pressure line B. The passages 23 of the distributor valve 18 are in communication with one another through the spindle cavity 20 at the area between the shoulders t2and t3, so that oil can flow from below the pistons 13 a 1, 13 a 2. . . while assisted by the springs U1, U2. . . through the passages D, E, F, G, a space H and a passage J into a box K, so that the press wheels 14 a 1, 14 a 2. . . of the pistons 13 a 1, 13 a 2. . . separate from the cam ring 11 and the box frame 10 of the radial piston hydraulic motor 100 can be rotated freely.

When the spindle 19 is moved in the direction indicated by the arrow L1in the figure by means of the pressure of a hydraulic fluid, such as oil, passed into the passage C against the spring force of the spring 21, the shoulder t2of the spindle 19 is moved to a position in which the shoulder t2is at the partition wall 26 and the pressure passage B is in communication with the oil passages of the working side of the distributor valve 18, and the oulets of the distributor valve 18 are further connected to the outlet passage A. In that connection, the pressure side B and the outlet side A are connected with each other through the distributor valve 18 and the pistons 13 a 1, 13 a 2. . . The passages 23 of the distributor valve 18 provided for the pistons 13 a 1, 13 a 2. . . which are in the working phase open into the annular groove 24 aand the passages 23 of the distributor valve 18 provided for the pistons 13 a 1, 13 a 2. . . which are in the return phase open into a second annular groove 24 b. The passage C includes a plug 30 and a through-hole 31 in it for a hydraulic fluid. The plug 30 keeps the spindle 19 in the spindle cavity 20.

The inlet passages 23 of the distributor valve 18 open into the passage D situated in the shaft 17 and the return passages 23 thereof open into the passage E situated in the shaft 17. The passages D and E open into the spindle cavity 20. The axial passage F is connected with the passage E and the passage G, which extends radially in the shaft 17 and opens into the end area of the spindle cavity 20, is connected with the axial passage F. The return passage A opens into the spindle cavity 20 at the area between the passages E and G. From the interior space K of the box 10 there is the passage J in the shaft 17, which passage J opens into the spindle cavity 20 at the end area thereof. The spindle 19 includes the shoulders t1, t2, t3and t4, advantageously shoulders of circular cross-section, and the smaller-diameter spindle portions p1, p2, p3, p4between them, the cross-section of said spindle portions being advantageously circular. The spring 21 is situated around the portion p4between the shoulder t4and the end of the spindle cavity 20. The passage B includes an end passage portion which extends radially in the shaft 17 and opens into the spindle cavity 20. The partition wall 25 is placed between it and the radially extending passage D. Between the passage E, which extends radially in the shaft 17 and opens into the spindle cavity 20, and the passage D there is also the partition wall 26.

In the device arrangement, in the drive state of the motor, the shoulder t2of the spindle 19 is at the partition wall 26, so that the pressure passage B of the radial piston hydraulic motor 100 communicates, through the space 20 between the shoulders t1and t2, with the passage D, the passages 23 of the distributor valve 18 and with the pistons 13 a 1, 13 a 2. . . which are in the working phase. The return passages 23 of the distributor valve 18 and the pistons 13 a 1, 13 a 2. . . which are in the return phase communicate with the return passage A between the passage E and the shoulders t2and t3via the spindle cavity 20 of the spindle 19. In the free running state when the motor 100 does not drive, the springs U1, U2. . . press the pistons 13 a 1, 13 a 2. . . to the bottom position, so that the pressure lines A and B are blocked and the working phase and return phase passages 23 of the distributor valve 18 communicate with one another through the passages D and E and the spindle cavity 20 at the area between the shoulders t2and t3of the spindle 19.

When the pistons 13 a 1, 13 a 2. . . and the piston rollers 14 a 1, 14 a 2. . . are moving towards the cam ring 11, a pressure is generated inside the box frame 10 because of the throttling action of a normal hose line f leading from the interior space K of the box 10 to a tank T. The pressure of the interior space K of the box 10 also acts through the passage J on the end of the spindle 19 at the side of the spring 21, and on the shoulder t4. In that connection, the speed of movement of the spindle 19 to the right (arrow L1) slows down because of the pressure force acting on the shoulder t4such that high pressure peaks are not produced at any stage in the interior space K of the box 10. The passage J is a radial passage situated in the shaft 17 and it opens into the interior space K of the box 10 and into the end of the spindle cavity 20.

When the piston rollers 14 a 1, 14 a 2. . . have reached the cam ring 11, the radial piston hydraulic motor 100 is in a normal drive state. The shoulder t2of the spindle 19 separates the pressure lines B and A as well as the passages D and E from one another. Oil flows from the passage B through the line D to the distributor valve 18 and further under the pistons 13 a 1, 13 a 2. . . In the return phase of the pistons 13 a 1, 13 a 2. . . (at that time, the pistons 13 a 1, 13 a 2. . . move towards the centre of the radial piston hydraulic motor 100), oil is passed from below the pistons 13 a 1, 13 a 2. . . through the distributor valve 18 to the passage E and further to the line A. The spindle 19 is in a position in which the radial passage E opens into the space between the shoulders t3and t4, so that pressure has access from the line E only into the passages F and G and into the space between the shoulders t3and t4in the spindle cavity 20. The shoulder t4prevents pressure communication with the passage J and with the interior space K of the box 10.

When the control pressure is removed from the line C, the spindle 19 starts to return to the left by means of the spring 21. When the spindle 19 is completely on the left (FIG. 1), oil is able to flow from under the pistons 13 a 1, 13 a 2. . . through the distributor valve 18 and the passages D and E to the passages F and G and further through the end space H of the spindle cavity 20 and through the passage J to the interior space K of the box 10, from where there is the box line f leading to the tank T. There is the same pressure above and below the pistons 13 a 1, 13 a 2. . . , so that the free rotation springs U1, U2. . . and the cam ring 11 (when revolving) are needed to press the pistons 13 a 1, 13 a 2. . . to their bottom position. When all pistons 13 a 1, 13 a 2. . . are in the bottom position, the motor can be rotated freely. When the direction of rotation of the radial piston hydraulic motor 100 is changed, a higher-pressure working pressure is passed to the passage A, so that a lower-pressure return line is formed by the passage B. The operation of the radial piston hydraulic motor 100 is otherwise the same.

FIGS. 5A and 5B show a second embodiment of the spindle 19 of the invention, the operation mode being different in the embodiment. When no control pressure is passed into the passage C, the spindle 19 is kept by means of the spring 21 in a position in which a drive situation is realized, and when control pressure is passed into the passage C, the spindle 19 is moved against the spring force of the spring 21 to a position in which a neutral position situation is realized. In the phase of FIG. 5A, no control pressure has been passed into the passage C and the spindle 19 is in a position in which a drive situation is realized, and in the illustration of FIG. 5B, control pressure has been passed into the passage C and the spindle 19 has been moved to a position in which the shoulders t1and t2block the pressure lines A and B and the radial piston hydraulic motor 100 is freely rotatable, i.e. in a free rotation state.

A free rotation valve 50 built inside the radial piston hydraulic motor 100 is used in the method for control of the radial piston hydraulic motor in accordance with the invention. The free rotation valve 50 comprises the spindle 19, which is moved in the spindle cavity 20. In accordance with the invention, the radial piston hydraulic motor 100 is controlled such that the shoulders t1and t2of the spindle 19 in the free rotation situation block the inlet and outlet passages A and B of the working pressure, so that in the free rotation situation the pistons 13 a 1, 13 a 2. . . and the press rollers 14 a 1, 14 a 2. . . associated with them are pressed by means of the springs U1, U2. . . to the bottom position and out of contact with the cam ring 11. The radial piston hydraulic motor 100 can then be rotated freely.

Furthermore, in the method in accordance with the invention, the passages of the distributor valve 18 leading to the pistons 13 a 1, 13 a 2. . . which are in the working phase and the passages of the distributor valve 18 leading from the pistons 13 a 1, 13 a 2. . . which are in the return phase are connected in series in the free rotation situation and, in addition, said system of passages connected in series is connected to the interior space K of the box frame 10. In the method in accordance with the invention, control of the radial piston hydraulic motor 100 takes place by linearly moving the spindle 19 placed in the spindle cavity 20 of the central shaft 17.

The operation shown in FIGS. 5A and 5B can also be accomplished by the design of FIGS. 1–3 such that the spring 21 is moved to the left end of the spindle 19 shown in FIG. 1 and, correspondingly, an external control pressure is passed to the right end of the spindle 19 shown in FIG. 1. In that case, the right-hand end of the spindle 19 must be provided with an additional shoulder t for receiving pressure and a line C for supplying control pressure. When the control pressure is now passed to the right side of the additional shoulder t, the radial piston hydraulic motor 100 is disengaged to rotate freely. Without said control pressure for the right end of the spindle 19, the radial piston hydraulic motor 100 is in the normal drive state while the spring 21 in this embodiment moves the spindle 19 to the right (arrow L1) to one extreme position of the spindle 19.

In this application, control pressure, advantageously the pressure of a hydraulic fluid, such as hydraulic oil, passed to the passage C is used for moving the spindle 19. The spindle 19 can also be moved by means of an actuator, for example, an electric motor. Within the scope of the invention, it is possible to replace the spring 21 at the end of the spindle 19, for example, with an air spring.

Check that the pump shaft is rotating. Even though coupling guards and C-face mounts can make this difficult to confirm, it is important to establish if your pump shaft is rotating. If it isn’t, this could be an indication of a more severe issue, and this should be investigated immediately.

Check the oil level. This one tends to be the more obvious check, as it is often one of the only factors inspected before the pump is changed. The oil level should be three inches above the pump suction. Otherwise, a vortex can form in the reservoir, allowing air into the pump.

What does the pump sound like when it is operating normally? Vane pumps generally are quieter than piston and gear pumps. If the pump has a high-pitched whining sound, it most likely is cavitating. If it has a knocking sound, like marbles rattling around, then aeration is the likely cause.

Cavitation is the formation and collapse of air cavities in the liquid. When the pump cannot get the total volume of oil it needs, cavitation occurs. Hydraulic oil contains approximately nine percent dissolved air. When the pump does not receive adequate oil volume at its suction port, high vacuum pressure occurs.

This dissolved air is pulled out of the oil on the suction side and then collapses or implodes on the pressure side. The implosions produce a very steady, high-pitched sound. As the air bubbles collapse, the inside of the pump is damaged.

While cavitation is a devastating development, with proper preventative maintenance practices and a quality monitoring system, early detection and deterrence remain attainable goals. UE System’s UltraTrak 850S CD pump cavitation sensor is a Smart Analog Sensor designed and optimized to detect cavitation on pumps earlier by measuring the ultrasound produced as cavitation starts to develop early-onset bubbles in the pump. By continuously monitoring the impact caused by cavitation, the system provides a simple, single value to trend and alert when cavitation is occurring.

The oil viscosity is too high. Low oil temperature increases the oil viscosity, making it harder for the oil to reach the pump. Most hydraulic systems should not be started with the oil any colder than 40°F and should not be put under load until the oil is at least 70°F.

Many reservoirs do not have heaters, particularly in the South. Even when heaters are available, they are often disconnected. While the damage may not be immediate, if a pump is continually started up when the oil is too cold, the pump will fail prematurely.

The suction filter or strainer is contaminated. A strainer is typically 74 or 149 microns in size and is used to keep “large” particles out of the pump. The strainer may be located inside or outside the reservoir. Strainers located inside the reservoir are out of sight and out of mind. Many times, maintenance personnel are not even aware that there is a strainer in the reservoir.

The suction strainer should be removed from the line or reservoir and cleaned a minimum of once a year. Years ago, a plant sought out help to troubleshoot a system that had already had five pumps changed within a single week. Upon closer inspection, it was discovered that the breather cap was missing, allowing dirty air to flow directly into the reservoir.

A check of the hydraulic schematic showed a strainer in the suction line inside the tank. When the strainer was removed, a shop rag was found wrapped around the screen mesh. Apparently, someone had used the rag to plug the breather cap opening, and it had then fallen into the tank. Contamination can come from a variety of different sources, so it pays to be vigilant and responsible with our practices and reliability measures.

The electric motor is driving the hydraulic pump at a speed that is higher than the pump’s rating. All pumps have a recommended maximum drive speed. If the speed is too high, a higher volume of oil will be needed at the suction port.

Due to the size of the suction port, adequate oil cannot fill the suction cavity in the pump, resulting in cavitation. Although this rarely happens, some pumps are rated at a maximum drive speed of 1,200 revolutions per minute (RPM), while others have a maximum speed of 3,600 RPM. The drive speed should be checked any time a pump is replaced with a different brand or model.

Every one of these devastating causes of cavitation threatens to cause major, irreversible damage to your equipment. Therefore, it’s not only critical to have proper, proactive practices in place, but also a monitoring system that can continuously protect your valuable assets, such as UE System’s UltraTrak 850S CD pump cavitation senor. These sensors regularly monitor the health of your pumps and alert you immediately if cavitation symptoms are present, allowing you to take corrective action before it’s too late.

Aeration is sometimes known as pseudo cavitation because air is entering the pump suction cavity. However, the causes of aeration are entirely different than that of cavitation. While cavitation pulls air out of the oil, aeration is the result of outside air entering the pump’s suction line.

Several factors can cause aeration, including an air leak in the suction line. This could be in the form of a loose connection, a cracked line, or an improper fitting seal. One method of finding the leak is to squirt oil around the suction line fittings. The fluid will be momentarily drawn into the suction line, and the knocking sound inside the pump will stop for a short period of time once the airflow path is found.

A bad shaft seal can also cause aeration if the system is supplied by one or more fixed displacement pumps. Oil that bypasses inside a fixed displacement pump is ported back to the suction port. If the shaft seal is worn or damaged, air can flow through the seal and into the pump’s suction cavity.

As mentioned previously, if the oil level is too low, oil can enter the suction line and flow into the pump. Therefore, always check the oil level with all cylinders in the retracted position.

If a new pump is installed and pressure will not build, the shaft may be rotating in the wrong direction. Some gear pumps can be rotated in either direction, but most have an arrow on the housing indicating the direction of rotation, as depicted in Figure 2.

Pump rotation should always be viewed from the shaft end. If the pump is rotated in the wrong direction, adequate fluid will not fill the suction port due to the pump’s internal design.

A fixed displacement pump delivers a constant volume of oil for a given shaft speed. A relief valve must be included downstream of the pump to limit the maximum pressure in the system.

After the visual and sound checks are made, the next step is to determine whether you have a volume or pressure problem. If the pressure will not build to the desired level, isolate the pump and relief valve from the system. This can be done by closing a valve, plugging the line downstream, or blocking the relief valve. If the pressure builds when this is done, there is a component downstream of the isolation point that is bypassing. If the pressure does not build up, the pump or relief valve is bad.

If the system is operating at a slower speed, a volume problem exists. Pumps wear over time, which results in less oil being delivered. While a flow meter can be installed in the pump’s outlet line, this is not always practical, as the proper fittings and adapters may not be available. To determine if the pump is badly worn and bypassing, first check the current to the electric motor. If possible, this test should be made when the pump is new to establish a reference. Electric motor horsepower is relative to the hydraulic horsepower required by the system.

For example, if a 50-GPM pump is used and the maximum pressure is 1,500 psi, a 50-hp motor will be required. If the pump is delivering less oil than when it was new, the current to drive the pump will drop. A 230-volt, 50-hp motor has an average full load rating of 130 amps. If the amperage is considerably lower, the pump is most likely bypassing and should be changed.

Figure 4.To isolate a fixed displacement pump and relief valve from the system, close a valve or plug the line downstream (left). If pressure builds, a component downstream of the isolation point is bypassing (right).

The most common type of variable displacement pump is the pressure-compensating design. The compensator setting limits the maximum pressure at the pump’s outlet port. The pump should be isolated as described for the fixed displacement pump.

If pressure does not build up, the relief valve or pump compensator may be bad. Prior to checking either component, perform the necessary lockout procedures and verify that the pressure at the outlet port is zero psi. The relief valve and compensator can then be taken apart and checked for contamination, wear, and broken springs.

Install a flow meter in the case drain line and check the flow rate. Most variable displacement pumps bypass one to three percent of the maximum pump volume through the case drain line. If the flow rate reaches 10 percent, the pump should be changed. Permanently installing a flow meter in the case drain line is an excellent reliability and troubleshooting tool.

Ensure the compensator is 200 psi above the maximum load pressure. If set too low, the compensator spool will shift and start reducing the pump volume when the system is calling for maximum volume.

Performing these recommended tests should help you make good decisions about the condition of your pumps or the cause of pump failures. If you change a pump, have a reason for changing it. Don’t just do it because you have a spare one in stock.

Conduct a reliability assessment on each of your hydraulic systems so when an issue occurs, you will have current pressure and temperature readings to consult.

Al Smiley is the president of GPM Hydraulic Consulting