Several types of pumps are especially useful for pumping liquids and other fluids with minimal back-flow and that are amenable to miniaturization. An example is a gear pump, another example is a piston pump, and a third example is a variation of a gear pump in which the rotary pumping members have lobes that interdigitate with each other. Gear pumps and related pumps have experienced substantial acceptance in the art due to their comparatively small size, quiet operation, reliability, and cleanliness of operation with respect to the fluid being pumped. Gear pumps and related pumps also are advantageous for pumping fluids while keeping the fluids isolated from the external environment. This latter benefit has been further enhanced with the advent of magnetically coupled pump-drive mechanisms that have eliminated leak-prone hydraulic seals that otherwise would be required around pump-drive shafts.
Gear pumps have been adapted for use in many applications, including applications requiring extremely accurate delivery of a fluid to a point of use. Consequently, these pumps are widely used in medical devices and scientific instrumentation. Developments in many other areas of technology have generated new venues for accurate pumps and related fluid-delivery systems. Such applications include, for example, delivery of liquids in any of various automotive applications.
Automotive applications are demanding from technical, reliability, and environmental viewpoints. Technical demands include spatial constraints, ease of assembly and repair, and efficacy. Reliability demands include requirements for high durability, vibration-resistance, leak-resistance, maintenance of hydraulic prime, and long service life. Environmental demands include internal and external corrosion resistance, and ability to operate over a wide temperature range.
Most moving parts of gear pumps and related types of pumps, as summarized above, are naturally subject to wear. If allowed to progress excessively, wear can degrade the operational accuracy, reliability, and/or usability of the pump. Consequences of wear can be reduced in some instances by performing preventative maintenance of the pump, which can include replacement of parts that have experienced at least a threshold amount of wear. Scheduled preventative maintenance can be an important aspect of prolonging the usable life of the pump. Also, in a given population of pumps, especially pumps experiencing hard use, it is natural for at least a few to require an unscheduled maintenance or repair activity to keep them running or running properly.
A maintenance activity on a conventional gear-pump head, for example, typically requires at least: (1) disconnection and removal of the pump assembly from its hydraulic circuit in the host system, (2) disconnection of the pump assembly from electrical power, (3) removal of the pump from the host system, and (4) disassembly of the pump head to gain access to the moving parts (e.g., the gears) inside. These tasks can be difficult to perform even under the best of conditions, such as in a repair facility manned by skilled personnel, and are particularly difficult to perform in the field or on location. For example, the culprit pump may be: (a) situated in a substantially inaccessible location in the host system, (b) difficult to disconnect hydraulically, electrically, and/or mechanically from the host system, (c) difficult to keep clean once opened, and/or (d) constructed such that the subject parts are easily lost or damaged during the maintenance activity.
Alternatively to removing and disassembling the pump head in the field, conventional field maintenance of the pump may involve simply disconnecting and detaching the pump assembly from the host system and replacing the pump with a new one. This approach can be unacceptably expensive because the entire pump assembly is replaced even though only a part of it actually needs replacement. This approach does not usually save much time because the pump assembly must be entirely disconnected and removed, followed by mounting and connecting the replacement pump.
An exemplary “in the field” use of a gear pump or related type of pump is in or on a motor vehicle. As noted above, automotive applications are inherently “extreme duty” applications for pumps at least in part because of the mobility of the vehicle. Motion of the vehicle subjects the pump to large amounts of vibration and possibly other physical impacts, and mobility allows the vehicle to be in any of a wide variety of environmental circumstances and physical locations (including remote locations). Consequently, maintenance or repair of the pump may need to be performed on location under very difficult conditions. In other words, “in the field” could be substantially anywhere accessible by the vehicle.
The useful life of a motor vehicle is usually longer than the usable life of most pumping elements. Also, the performance demands imposed on gear pumps and related types of pumps mounted on motor vehicles are progressively becoming more severe, which results in progressively greater loads being applied to the pumping elements. Increasing the load increases wear. Therefore, it is more probable that such a pump will be the subject of at least one maintenance activity performed in the field.
As in motor-vehicle applications, many other applications of gear pumps and related types of pumps are characterized by progressively increased performance demands imposed on the pump, difficulty of access to the pump for maintenance activity, difficulty of shutting down the host system for the time needed to perform the maintenance activity, and difficulty of performing the maintenance activity on location. An example increased performance demand is higher pump-outlet pressure, which typically causes more rapid wear of certain parts and surfaces inside the pump-head.
Therefore, there is a need for pumps and pump heads that are more easily and quickly serviced or otherwise subjected to an activity involving opening up the pump head on location, such as in the field. There is also a need for pumps and pump heads that allow simplified replacement of wearing or worn components without having to replace the entire pump.