GB1598311A

GB1598311A - Hydraulic pump or motor

Info

Publication number: GB1598311A
Application number: GB3503977A
Authority: GB
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1977-08-20
Filing date: 1977-08-20
Publication date: 1981-09-16

Description

(54) HYDRAULIC PUMP OR MOTOR (71) We, LUCAS INDUSTRIES LI MITED, a British company of Great King Street, Birmingham B19 2XF do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to a hydraulic pump or motor, hereinafter to be referred to simply as a hydraulic machine.

There is a demand for equipment having low magnetic permeability, for use, for example, in mine sweeping applications.

However. the normal requirement is for hydraulic machines to be used in such equipment to have a magnetic permeability ot less than 1.05 It. It is now desired to produce a hydraulic machine having a very much lower magnetic permeability, i.e. less than 1.005 It The Applicants expected to be able to use stainless steel in the construction of a hydraulic machine having a magnetic permeability of 1.005 It since certain stainless steel alloys have this low magnetic permeability. However, in practice they were surprised to find that the properties of the stainless steel alloy are rather unstable after machining and annealing with the result that the permeability tends to rise to unacceptable levels.

An object of the present invention is to provide a hydraulic machine which can be manufactured in quantity consistently to have the desired very low magnetic permeability.

According to the present invention, there is provided a hydraulic machine (as defined herein) wherein the parts of the machine are formed from material having a sufficiently low magnetic permeability that the overall magnetic permeability of the machine is less than 1.005 u, characterised in that the materials are substantially non-ferrous materials and bearing surfaces are coated with a relatively hard bearing material such as chromium.

The hydraulic machine may be a swash plate pump or motor comprising a cylinder block, pistons slidable in the cylinder block, a cam surface and slippers engaged with the pistons and abutting against a cam plate, the surface of the cam plate against which the slippers engage and the cylinder wall engaging surfaces of the pistons being coated with said hard bearing material.

Preferably, the cylinder block is of bronze and a housing of the machine is formed of aluminium alloy.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawing which is an axial section through a hydraulic motor according to one embodiment of the present invention.

Referring to the drawing, the motor comprises aluminium alloy housing parts 1, 2 and 3 secured together by cupro nickel studs and bolts 4 a suitable material for the bolts and studs 4 is Hidrax Special Wrought (Alloy Code 13A) having a composition of 2.04-4.0% aluminium, 0.5-2.5% iron, 13.016.0% nickel, 0.1-0.5% manganese and the balance being copper. Within the housing, there is provided a cylinder block 5 formed of a high strength bronze (e.g. Hidurel 5 Alloy Code Cast 3F containing 1.8-2% nickel, 0.3-0.5% silicon and the remainder being copper). The cylinder block 5 is keyed to a shaft 6 formed of high strength cupro nickel (e.g. Hidurax Special Wrought Alloy Code 13A) provided with chromed bearing areas adjacent aluminium bronze bearing bushes 7. The cylinder block 5 is provided with a separate ported bearing plate 8 which bears against a stationary port plate 9.The plates 8 and 9 are formed of the same material as the remainder of the cylinder block 5 but the bearing surface, i.e. the surface engaged by the bearing plate 9, of the port plate 6 is chromed. Cylinder bores 10 are aligned with the ports in the ported bearing plate 8 and a seal 11 prevents escape of fluid from each cylinder wall 10 between the plate 8 and the remainder of the cylinder block 5. Each seal 11 comprises an annular sealing member 12 which is urged into engagement with the bearing plate 8 by means of a spring 13 acting between a fixed and a slidable cup member 14 and 15 respectively. The members 12, 14 and 15 are formed of high strength cupro nickel (in this embodiment the Hidurax Special cupro nickel alloy mentioned hereinabove) whilst the spring 13 is formed of a beryllium copper alloy.Slidable in the cylinder bores 10 are respective pistons 16 formed of high strength cupro nickel (in this embodiment Hidurax Special as mentioned above) with chromed bearing areas. The pistons 16 engage in respective slippers 17 formed of aluminium bronze. The slippers 17 engage against a fixed cam plate 18 formed of high strength bronze (in this embodiment Hidurel 5 as mentioned above) provided with a chromed bearing surface against which the slippers 17 engage. The slippers 17 are located in an auxiliary cam plate 19 formed of aluminium alloy having a hard anodised surface. A retainer plate 20 for retaining the auxiliary cam plate 19 in position is formed of aluminium bronze alloy. An end cap 21 through which the shaft 6 passes to extend externally of the housing is formed of high strength bronze (in this embodiment the Hidurel 5 alloy mentioned hereinbefore).All of the fixing studs, bolts, dowels, etc, are formed of the same material as the studs and bolts 4.

The above-described motor has a magnetic permeability of 1.004 Ft.

In use, the motor operates in a manner well known in the art for swash plate type motors. Hydraulic fluid under pressure is supplied to one of two kidney shaped ports in the port plate 9 whilst the other port in the plate 9 is connected to a low pressure side of the supply circuit. The reaction of the piston under pressure against the inclined cam surface 18 through the intermediary of the slippers 17 causes rotation of the cylinder block and thus rotation of the shaft 6 so that the pistons 16 are successively connected with the high pressure port and the low pressure port. The precise manner in which this occurs is well known in the art and will not be described herein in any further detail since it forms no part of the present invention.

WHAT WE CLAIM IS: 1. A hydraulic machine (as defined herein) wherein the parts of the machine are formed from material having sufficiently low magnetic permeability that the overall magnetic permeability of the machine is less than 1.005cm, characterised in that the materials are substantially non-ferrous materials and bearing surfaces are coated with a relatively hard bearing material such as chromium.

2. A hydraulic machine as claimed in claim 1, in the form of a swash plate pump or motor comprising a cylinder block, pistons slidable in the cylinder block, a cam surface and slippers engaged with the pistons and abutting against a cam plate, the surface of the cam plate against which the slippers engage and the cylinder wall engaging surfaces of the pistons being coated with said hard bearing material.

3. A hydraulic machine as claimed in claim 2, wherein the cylinder block is of bronze and a housing of the pump or motor is formed of aluminium alloy.

5. A hydraulic machine substantially as hereinbefore described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

surface engaged by the bearing plate 9, of the port plate 6 is chromed. Cylinder bores 10 are aligned with the ports in the ported bearing plate 8 and a seal 11 prevents escape of fluid from each cylinder wall 10 between the plate 8 and the remainder of the cylinder block 5. Each seal 11 comprises an annular sealing member 12 which is urged into engagement with the bearing plate 8 by means of a spring 13 acting between a fixed and a slidable cup member 14 and 15 respectively. The members 12, 14 and 15 are formed of high strength cupro nickel (in this embodiment the Hidurax Special cupro nickel alloy mentioned hereinabove) whilst the spring 13 is formed of a beryllium copper alloy.Slidable in the cylinder bores 10 are respective pistons 16 formed of high strength cupro nickel (in this embodiment Hidurax Special as mentioned above) with chromed bearing areas. The pistons 16 engage in respective slippers 17 formed of aluminium bronze. The slippers 17 engage against a fixed cam plate 18 formed of high strength bronze (in this embodiment Hidurel 5 as mentioned above) provided with a chromed bearing surface against which the slippers 17 engage. The slippers 17 are located in an auxiliary cam plate 19 formed of aluminium alloy having a hard anodised surface. A retainer plate 20 for retaining the auxiliary cam plate 19 in position is formed of aluminium bronze alloy. An end cap 21 through which the shaft 6 passes to extend externally of the housing is formed of high strength bronze (in this embodiment the Hidurel 5 alloy mentioned hereinbefore).All of the fixing studs, bolts, dowels, etc, are formed of the same material as the studs and bolts 4.

The above-described motor has a magnetic permeability of 1.004 Ft.

In use, the motor operates in a manner well known in the art for swash plate type motors. Hydraulic fluid under pressure is supplied to one of two kidney shaped ports in the port plate 9 whilst the other port in the plate 9 is connected to a low pressure side of the supply circuit. The reaction of the piston under pressure against the inclined cam surface 18 through the intermediary of the slippers 17 causes rotation of the cylinder block and thus rotation of the shaft 6 so that the pistons 16 are successively connected with the high pressure port and the low pressure port. The precise manner in which this occurs is well known in the art and will not be described herein in any further detail since it forms no part of the present invention.

WHAT WE CLAIM IS:

1. A hydraulic machine (as defined herein) wherein the parts of the machine are formed from material having sufficiently low magnetic permeability that the overall magnetic permeability of the machine is less than 1.005cm, characterised in that the materials are substantially non-ferrous materials and bearing surfaces are coated with a relatively hard bearing material such as chromium.

2. A hydraulic machine as claimed in claim 1, in the form of a swash plate pump or motor comprising a cylinder block, pistons slidable in the cylinder block, a cam surface and slippers engaged with the pistons and abutting against a cam plate, the surface of the cam plate against which the slippers engage and the cylinder wall engaging surfaces of the pistons being coated with said hard bearing material.

3. A hydraulic machine as claimed in claim 2, wherein the cylinder block is of bronze and a housing of the pump or motor is formed of aluminium alloy.

5. A hydraulic machine substantially as hereinbefore described with reference to the accompanying drawing.