trw hydraulic pump pricelist

White House Products Ltd. is proud to be a leading Ross hydraulics supplier. When you’re looking for Ross hydraulic motors, you can find them in our catalog, whether you need an orbital motor or hydraulic torqmotor. Officially known as TRW Ross, the brand is now part of Parker-Hannifin’s Hydraulic Pump/Motor Division.

Parker is known for a range of engineering products in hydraulics and other technologies, including pneumatics, process control, and fluid and gas handling, which are used in industrial, aerospace, and mobile equipment applications. The company was founded in 1917 and specializes in a wide range of motion and control technologies.

Ross motors and other products are produced at a 260,000-square-foot plant in Greenville, TN and in Germany. The Greenville facility was purchased by Parker in 1993, it had originally opened in 1972 as part of the TRW Ross Gear Division. A range of low-speed, high-torque motors and hydrostatic steering components are manufactured there.

Typically featuring an internal trochoidal gear design, a high-torque hydraulic orbital motor effectively converts hydraulic fluid power into mechanical rotary motion in a system. A distributor valve directs the fluid as it moves through the chamber. Orbital motors are designed to generate high rotational torque which is directly proportional to the pressure exerted by the load and the motor displacement.

We stock commonly used Parker supersessions of Ross hydraulics components and will even help match parts with your application. Customers trust our repair service as well. If there’s a replacement motor you are looking for, browse our inventory and log in to make your purchase or view pricing, or call +44 (0) 1475 742500 for more information.

Knowing how to right-size an electric motor for your hydraulic pump can help reduce energy consumption and increase operational efficiency. The key is to ensure the pump motor is operating at peak continuous load. But how can you know how much power is needed?

Before you can choose the correct electric motor, you must know how much horsepower (Hp) is required to drive the pump shaft. Generally, this is calculated by multiplying the flow capacity in gallons per minute (GPM) by the pressure in pounds per square inch (PSI). You then divide the resulting number by 1714 times the efficiency of the pump, for a formula that looks like this:

If you’re not sure how efficient your hydraulic pump is, it is advisable to use a common efficiency of about 85% (Multiplying 1714 x 0.85 = 1460 or 1500 if you round up). This work-around simplifies the formula to:

The above formula works in most applications with one notable exception: If the operating pressure of a pump is very low, the overall efficiency will be much lower than 85%. That’s because overall efficiency is equal to mechanical efficiency (internal mechanical friction) plus volumetric efficiency.

Internal friction is generally a fixed value, but volumetric efficiency changes depending on the pressure used. Low-pressure pumps have high volumetric efficiency because they are less susceptible to internal leakage. However, as the pressure goes up and internal fluids pass over work surfaces such as pistons, port plates, and lubrication points, the volumetric efficiency goes down and the amount of torque required to turn the pump for developing pressure goes up.

This variance makes it very important to know the efficiency of your pump if you’re using it at low pressure! Calculations that do not take low pressure into account will lead to a failed design.

If you calculate 20 GPM @ 300 PSI with an assumed overall efficiency of 89%, you would probably select a 5 Hp electric motor. However, if you calculate the same 20 GPM @ 300 PSI with the actual overall efficiency of 50%, you would know that you should be using a 7.5 Hp motor. In this example, making an assumption about the efficiency of your pump could result in installing a motor that is too large, driving up your overall operating cost.

There are many contributors to the overall efficiency of a hydraulic pump, and it pays to be as accurate as possible when choosing a motor. A best practice for proper sizing is to use published data from the pump vendor that shows actual input torque vs. pressure or overall efficiency vs pressure. Note that efficiency is also affected by RPM.

Identifying a right-sized motor for your hydraulic pump does not always ensure you are using the most efficient motor. Be sure to read Part 2 of this post to learn how RMS loading and Hp limiting can help you scale down the size of your electric motor to save money while maximizing efficiency.

Various embodiments of a motor/pump unit are described herein. In particular, the embodiments described herein relate to an improved motor/pump unit for a power-steering arrangement in a motor vehicle.

A motor/pump unit comprising a housing, a hydraulic pump unit with a pump module, and a motor unit with a drive motor is shown in DE 203 02 534 U1, and corresponding US 2006/039804 which published on Feb. 23, 2006. In a motor/pump unit of this type, the outer surfaces, in particular of the outer housing surrounding the motor and pump units, emit sound outwards. Furthermore, in conventional motor/pump units without special sound-absorbing and sound-damping measures, the structure-borne sound generated by the motor and pump units is passed on through the connected components into the passenger compartment and is emitted there as sound transmitted by air. The connected components may also be stimulated to natural vibrations which again leads to the emission of air-borne sound.

In DE 203 15 224 U1, and corresponding US 2005/0053487 which published on Mar. 10, 2005, to reduce the noise development in a hydraulic system with a motor/pump unit, it is proposed to couple at least a portion of the motor/pump unit to the outer housing via a damping bearing which can be realized only at a relatively high cost.

The present application describes various embodiments of a motor/pump unit with a simplified possibility for efficiently reducing the noise development.

One embodiment of the motor/pump unit includes a housing, a hydraulic pump unit with a pump module, and a motor unit with a drive motor. The motor/pump unit further comprises at least one damping element which is provided between the pump unit and a portion of the housing to decouple the noise of the pump unit. The damping element provides for a damping of the vibrations of the pump unit, which occurs as the sound source. In this way, an interruption to the propagation of sound is provided close to the source.

Other advantages of the motor/pump unit will become apparent to those skilled in the art from the following detailed description, when read in light of the accompanying drawings.

In the Figures, a motor/pump unit 10 is shown for a power-steering arrangement in a motor vehicle, the structure of which is very similar to that of the motor/pump unit shown in DE 203 02 534 U1, which is incorporated herein by reference. The motor/pump unit 10 comprises a pump unit 12 with a pump module 14 and a motor unit 16 with a drive motor (not shown). The pump unit 12 and the motor unit 16 are accommodated in a shared outer housing 18, the pump unit 12 and the motor unit 16 being separated from each other by a flange 20. In the illustrated example embodiment, the outer housing 18 is formed as one piece, but it may also be divided, e.g. into a housing for the pump unit 12, a housing for the motor unit 16 and possibly an intermediate housing arranged between the pump unit 12 and the motor unit 16. The upper end side of the housing 18 is closed by a cover 22.

The end sides of the pump module 14 are closed by two covers 24, 26 which are screwed to each other. The pump module 14 is arranged in a resonator chamber which is bounded radially by a section 28 of the outer housing 18 and which surrounds the pump module 14 in a ring shape. The cover 22 of the housing 18 is therefore designated below as the resonator cover 22. The resonator cover 22 can be ascribed both to the outer housing 18 and to the pump unit 12.

The axial fixing of the pump module 14 in the housing 18 takes place by means of an elastically deformable spring element 30, which is inserted between the cover 24 of the pump module 14 and the resonator cover 22. The spring element 30 is corrugated (not illustrated) and is held in a matching recess of the cover 24, in order to prevent a lateral slippage. The spring element 30 presses the pump module 14 against the flange 20 and thus provides for an axial bracing of the pump module 14 in the housing 18. Positioning pins 32, which engage into corresponding recesses of the respectively opposite component, are provided on the pump module 14 (or alternatively on the flange 20) for correct positioning and fastening, particularly with respect to a rotation of the pump module 14 relative to the flange 20.

The coupling of the drive motor to the pump, which is formed in the pump module 14, takes place by means of a coupling 34 which connects a motor shaft 36 of the drive motor with a drive shaft 38 of the pump.

Various measures are described below which serve to decouple the noise of the pump from the outer housing 18 of the motor/pump unit 10. According to the actual requirements (which depend particularly on the frequency of the vibrations caused by the pump), the measures can be provided individually or in any desired combination.

A damping element 40 is provided between the lower cover 26 of the pump module 14 and the flange 20. The damping element 40 is constructed as a sheet metal part which is coated on both sides with an elastomer, but a coating only on one side or a component with an elastomer layer arranged between two sheet metal layers is also possible. Through this, a noise decoupling of the pump module 14 from the flange 20 is achieved, and hence also from the outer housing 18, particularly from the part of the housing 18 which surrounds the drive motor. The damping element 40 also serves as a sealing element for sealing the pump module 14 with respect to the flange 20. Furthermore, the damping element 40 may also undertake the separation of the high pressure zone from the low pressure zone of the pump unit 12. The construction of the lower cover 26 and/or of the opposite flange 20 is simplified if the damping element 40 is constructed as a flat seal. In this case, in fact no grooves have to be worked in for additional sealing elements. The flat seal may possibly be provided with corrugations in order to optimize the sealing capability.

As a further measure to prevent the transfer of vibrations from the pump module 14 to the flange 20, the positioning pins 32 are coated with elastomer or are covered with a shrink tube.

A noise uncoupling of the pump module 14 from the resonator cover 22 is achieved in that an elastomer spring is used as spring element 30, which secures the pump module 14 axially.

The drive shaft 38 of the pump and the motor shaft 36 of the drive motor are preferably connected with each other by means of an Oldham coupling 34 made of steel, which is held together in the centre by a vibration-damping elastomer element 48. Alternatively, a plastic coupling, e.g. made of PEEK, may be provided. In addition to steel or plastic couplings, steel/plastic or steel/elastomer couplings are also possible.

In accordance with the provisions of the patent statutes, the principle and mode of operation of the motor/pump unit have been explained and illustrated in its preferred embodiment. However, it must be understood that the motor/pump unit described herein may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.