DESCRIPTION
. Field of the Invention
The present invention relates to a pump-motor combination for converting hydraulic energy to mechanical energy and vice versa.
Background of the Invention
Application of the pump-motor combination can be manifold. However, the design according to the present invention is intended for application for the purpose of cooling of the peripheral body of the electric motors of heavy duty agricultural harvesting equipment by pumping metered quantity of coolant on heat emitting surfaces.
WO 02/08611 A2 provides a hydrostatic system comprising a hydraulic variable displacement pump and a hydraulic motor connected thereto.
US 2008/0085802 Al provides a drive assembly for an operating unit of an agricultural implement/machine having a clutch with an input mechanically and drivingly connected to a drive engine. A hydraulic pump is mechanically and drivingly connected to the output of the clutch. A hydraulic motor is hydraulically connected to the hydraulic pump and is mechanically and drivingly connected to the second input of a summarizing gear unit.
EP 0819854 A2 discloses a motor-driven hydraulic pump for use in motor vehicles and a driving coupler used therein.

However, none of the prior art systems provides a compact gear pump and motor combination onto agro-based self-propelled sprayer combines. The function of such combination unit thereon is towards cooling the windings of the electric wheel motor drive system.
It is an object of the present invention to provide a compact design exhibiting excellent results, viz.,
• Facilitates elimination of separate prime movers to run the hydraulic pump and the motor
• To achieve overall space compactness
• Balanced force-torque balance between pump and motor units
• Ease of controlling the pump outlet
• To achieve cost effectiveness
• Facilitates optimum oil flow path connectivity
• Maintains overall fuel efficiency with respect to targetted specific performance parameters
Summary of the Invention
The object of the invention is achieved by a pump-motor combination comprising a housing fitted with end covers having an oil inlet and an oil outlet in which all four gears are encased. Two drive gears are coupled with each other with tang coupling arrangement. All four gears are journalied inside the housing and are driven by external pressurized oil supply. All gears are made up of high alloy case-hardened steel material and the housing is made up of aluminium. Different types of seals are used to prevent occurrence of any undue internal/external leakages.
Accordingly, the present invention provides a pump-motor combination for converting hydraulic energy to mechanical energy and vice versa, said combination comprising: a housing; two pairs of gears located within the said housing; gears of motor held between two pairs of bush; and

a spacer and shaft seal separating the pump and the motor. The ends of the housing are closed by two end covers. The housing is made of aluminium. The ends of said housing are closed by two end covers. The pump and the motor are combined for compact design. The shaft seal is used for avoiding mixing of oil whenever two different oils are used in the pump and motor sections and for maintaining the pressure balance between the two oil chambers. The gear pump is built around fixed clearance concept. Both the gear pump and the gear motors are optimally housed within a single casing. Critically designed seals are employed in both motor and pump sections of the unit for eliminating any internal/external leakages.
Brief Description of the Accompanying Drawings
Figure 1 is a schematic cross-section of a thermoelectrically cooled helmet according to the present invention;
Figure 2 is a schematic representation of fluid flow in the pump-motor combination according to the invention;
Figure 3 is an exploded view of the pump-motor combination according to the invention.
Detailed Description of the Invention
The combined device according to the invention lies in a combination of a gear pump and a gear motor, wherein both said pump and motor are assembled in a common housing. For such assembly, two sets of gears are provided, one set being used in the motor unit, while the other set being used in the pump unit. All the four gears are of identical gear profile including the "PCD" (Pitch Circle Diameter) thereof, so that the gear pair of each set rolls in relation to each other without slip. Further, addendum, i.e. radial distance between the pitch circle of the gear pairs and the top land

(within which the gear sets are accommodated), as well as the number of teeth of all the four gears are same. That apart, gear pairs of said two sets for the pump unit and the motor unit are adapted to be in engagement with each other in pressure sealing manner with a - view to transport fluid between the gear teeth, so operatively engaged, from the inlets to the outlets of the motor and pump units respectively. One further important aspect lies in providing tang coupling (drive engagement mechanism) to couple the two shafts of the respective gear sets of the motor unit and the pump unit.
With reference to Figures 1 and 2 of the drawings, there is shown a gear pump and gear motor combination which enables conversion of hydraulic energy to mechanical energy and vice versa. In order to obtain this energy conversion, the pump-motor combination is designed mainly to include two sets of gears (1, 2) used in motor unit which converts hydraulic energy to mechanical energy and other set of gears (3, 4) used in pump unit which converts mechanical energy to hydraulic energy. All the four gears (1, 2, 3, 4) have identical gear profile including pitch circle diameter, addendum, number of teeth, etc. Gears 1, 2 and gears 3, 4 are in engagement with each other in a pressure sealing manner so as to transport fluid between the teeth from the inlet (A, a) to the outlet (B, b) in motor and pump arrangement respectively. The pump drive gear (3) and the motor drive gear (1) are coupled with each other by tang coupling arrangement as shown in Figure 1. All the gears are placed in the housing (5). A shaft seal (12) is used in between the pump and the motor in order to avoid mixing of oil whenever two different oils are used in the pump and motor sections and to maintain the pressure balance between the two oil chambers.
The motor drive gear (1) is coupled with drive gear of the pump (3) to transfer torque. The motor driven gear (2) drives along with the motor drive gear (1). The pump drive gear (3) receives torque/mechanical power from

the motor drive gear and rotates to create necessary pumping action. The pump driven gear (4) drives along with the pump drive gear (3). All components of both pump and motor are assembled in a common housing (5). After assembly of the motor components, the housing is covered with a motor cover (6). After assembly of the pump components, the housing is covered with a pump cover (7). A bush assembly (8) acts as a bearing support and as floating pressure balancing unit. Seals (9) facilitate creation of oil tight boundary around high oil pressure zones, A liner (10) acts as a bearing support for the rotating gear shafts. Shaft seal (12) helps to eliminate transfer of oil from motor to pump and vice versa.
Initially, pressurized oil impinges onto the gear motor inlet with the help of an external pumping unit. This oil drives the gears of the motor thus converting hydraulic energy into mechanical energy/torque. Since the motor drive shaft is coupled with the pump drive shaft, the mechanical energy/ torque is transferred to the pump. Thus, the hydraulic motor acts as a prime mover for the hydraulic gear pump. When the gears of the pump are rotated, necessary and sufficient vacuum is created at the pump inlet side and it draws oil from the reservoir and transfers the same to the pump outlet with high volumetric efficiency. This pump outlet oil carries out the intended task of cooling the heat-emitting surfaces of the equipment.
The motor section receives the required oil supply from an external hydraulic gear pump. The motor, in turn, is responsible for the operation of another in-built gear pump.
Increased overall fuel efficiency is achieved by eliminating separate prime movers for both pump and motor and by employing fixed clearance concept for gear pump. It is evident that instead of having two separate drive arrangements ensuring independent drive to the motor and pump, the combined pump-motor unit will result in reduced power and consequently reduced effective fuel consumption ensuring high fuel efficiency. The internal

forces occurring onto both pump and motor sections complement each other and the net resultant force assists in holding the unit onto the designated mounting plate.

WE CLAIM :
1. A pump-motor combination for converting hydraulic energy to
mechanical energy and vice versa, said combination comprising:
a housing (5);
two pairs of gears located within the said housing (5), one pair being used in the motor unit and the second pair being used in the pump unit; gears of motor (1, 2) held between two pairs of bush (8); and a spacer (11) and shaft seal (12) separating the pump and the motor.
2. A pump-motor combination as claimed in claim 1, wherein the ends of said housing (5) are closed by two end covers (6, 7).
3. A pump-motor combination as claimed in claims 1 or 2, wherein the said housing is made of aluminium.
4. A pump-motor combination as claimed in claims 1 to 3, wherein the ends of said housing (5) are closed by two end covers (6, 7).
5. A pump-motor combination as claimed in claims 1 to 4, wherein the pump and the motor are combined for compact design.
6. A pump-motor combination as claimed in claims 1 to 5, wherein the shaft seal (12) is used for avoiding mixing of oil whenever two different oils are used in the pump and motor sections and for maintaining the pressure balance between the two oil chambers.
7. A pump-motor combination as claimed in claims 1 to 6, wherein the .gear pump is built around fixed clearance concept.

8. A pump-motor combination as claimed in claims 1 to 7, wherein both the gear pump and the gear motors are optimally housed within a single casing.
9. A pump-motor combination as claimed in claims 1 to 8, wherein critically designed seals are employed in both motor and pump sections of the unit for eliminating any internal/external leakages.
10. A pump-motor combination as claimed in claims 1 to 9, wherein all the four gears possess identical gear profile, so that the gear pair of-each set rolls in relation to each other without slip.
11. A pump-motor combination as claimed in claims 1 to 10, wherein the radial distance between the pitch circle of the four gear pairs and the top land within which the gear sets are accommodated as well as the number of teeth of all four gears are same.
12. A pump-motor combination as claimed in claims 1 to 11, wherein tang coupling as drive engagement mechanism is provided to couple the two
• shafts of the respective gear sets of the motor unit and the pump unit.