Pump mounts are gearboxes that are designed to power hydraulic pumps. These gearboxes have one input and provisions for mounting one to four pumps on the output side (Fig. 4.30). Mounts are available with or without clutches, and different gear ratios are available. When an internal combustion engine is the prime mover, it is desirable to run the engine at a speed that will give maximum torque output, typically around 2000 rpm for a diesel engine. It may be desirable to run the pump at a higher speed to produce a higher output flow. Selecting a pump mount with a 1:1.25 gear ratio will convert a 2000 rpm input speed to a 2500 rpm pump drive speed.
Many mobile applications require a number of circuits on an individual machine. Separate pumps for each circuit can be provided with a number of combinations. Suppose the requirement is to provide four pumps on the machine. A single pump could be mounted on each mount of the four-pump mount shown in Fig. 4.30, or we might use a two-pump mount with a single pump on one mount and a three-pump multiple on the second mount. A designer typically considers several options before finalizing the design. In addition to the functional requirements, cost, space, and weight (on mobile machines) are key factors.
It is possible to drive some pumps with a belt drive. Belt drives place a radial load on the pump bearings. Manufacturers list an allowable radial load for their pumps, and this load should not be exceeded.
