FIELD

[0001 ] The present invention relates to motors that use a compressed gas as a driving fluid to drive the motor, and more particularly but not exclusively to air motors that receive compressed air to drive the motor.

BACKGROUND

[0002] Air motors are known to have a number of working chambers to which compressed gas is delivered to drive pistons at least partly enclosing the working chambers. Valve mechanisms co-ordinate the delivery of compressed air sequentially to the chambers, as well as provide for exhausting air from the chambers, to cause reciprocati on of the pistons. Typically the pistons are connected by a single shaft, with the pistons reciprocating along the axis of the shaft. An example of such an air motor is described in International Patent Application

PCT/AU2010/000226.

[0003] A further apparatus, such as a pump, is connected to the abovementioned shaft so as to be driven by the abovementioned air motor.

[0004] A disadvantage of known air motors, such as the air motors discussed above, is that they make inefficient use of the driving fluid (compressed air).

OBJECT

[0005] It is the object of the present invention to overcome or substantially ameliorate at least one of the above disadvantages.

SUMMARY

[0006] There is disclosed herein a motor that is driven by a compressed fluid, the motor including:

a first working chamber;

a first piston at least aiding in enclosing the first chamber; a second working chamber;

a second piston at least aiding in enclosing the second chamber;

a compressed fluid inlet;

an exhaust fluid outlet;

ducting and a valve assembly connecting the chambers, inlet and outlet so that the fluid is allowed to enter and leave the chambers to move the pistons; and wherein

the valve assembly enables passage of the fluid between the two chambers.

[0007] Preferably, the valve assemblies is configured to sequentially connect each the chambers to the air inlet and air outlet, with the chambers being connected to enable the fluid to be transferred therebetween before one of the chambers is connected to the inlet.

[0008] Preferably, the motor further includes a controller to control operation of the val ve assembly.

[0009] Preferably, the valve assembly is a primary valve assembly, and the controller is a pilot valve assembly.

[0010] Preferably, the primary valve assembly includes a movable valve member having a plurality of passages, and a plurality of ports surrounding the valve member, with the passages in the movable valve member connecting the ports to provide for the flow of the fluid through the valve assembly.

[001 1 ] Preferably, the ports include a plurality of ports connected to the inlet, a plurality of ports connected to the outlet, and a plurality of ports connecting the chambers, with the valve member being moved to sequentially connect the chambers to the inlet and outlet, and to connect the chambers.

[0012] Preferably, the motor includes:

a base;

a piston rod mounted in the base and coupling the piston so that the pistons move in unison; and

a valve cavity within which the movable valve member is located. [0013] Preferably, the movable valve member has a longitudinal axis, with passages being located at longitudinally spaced locations along the movable valve member.

[0014] Preferably, the ports are located, relative to said longitudinal axis, at longitudinally spaced positions.

[0015] Preferably, the motor is configured to receive compressed air as the driving fluid. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] A preferred form of the present invention will now be described by way of example only with reference to the accompanying drawings wherein:

[0017] Figure 1 is a schematic sectioned top plan of an air motor; and

[0018] Figure 2 is a series of schematic side elevations of a primary valve employed in the air motor of Figure 1, with the movable valve member in positions A, B, C and D.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0019] In the accompanying drawings there is schematically depicted an air motor 10. The air motor 10 receives compressed air in order to be driven. The air motor 10 includes a central val ve assembly 1 1 including a base 12. Preferably the base 12 is of a unitary construction, that is it is formed of a single piece. The base 12 has opposite side faces 13 to which there are sealingly attached caps (covers) 14 that, in co-operation with flexible diaphragms 15 provide working chambers 16 and 17. Each of the diaphragms 15 has secured to it a piston 18, with pistons 18 being connected by a piston rod (connecting member) 19 so that the pistons 18 reciprocate linearly in unison along the longitudinal axis 20 of the piston rod 19. To aid in securing each diaphragm 15 to its associated piston 18 there is provided a clamp member 21. The piston rod 19 extends through passage 48. The axis 20 is also the longitudinal axis of the passage 48.

[0020] Each diaphragm 15 has a portion abutting the adjacent piston 18 that effectively forms part of the piston 18. [0021 ] The faces 13 are generally parallel but spaced along the axis 20 and generally

perpendicular thereto.

[0022] A pilot valve 51 is located in the base 12 and includes a first cavity 22 with a

longitudinal axis 23 (generally parallel to the axis 20), within which there is located a movable valve member 24. Also located in the base 12 is a primary valve 52 that includes a second cavity 25 within which there is located a movable valve member 26.

[0023] Extending between the member 24 and surfaces of the base 12, surrounding the member, are seals 27.

[0024] The cavity 25 has a longitudinal axis 28 along which the member 26 moves, with the axis 28 being generally parallel to the axis 20.

[0025] The base 12 includes inlet ducting 50, exhaust (outlet) ducting 29, and intermediate ducting 30. The inlet ducting 50 communicates with an inlet port member 31 providing a threaded passage 32 that would typically be threadably engaged with a high pressure hose via which compressed air is delivered to the motor 10. The ducting 29 communicates with a threaded outlet passage 33, of the outlet port member 31 , that would be typically attached to a muffler and via which exhaust air gas exits the motor 10. The intermediate ducting 30 connects the first chamber 22 with the second chamber 25.

[0026] Fourth ducting 34 and 54 respectively connect the chambers 16 and 17 with the second chamber 25.

[0027] As seen in Figure 1 , the valve member 24 projects beyond the base 12 so as to extend into each of the chambers 16 and 17.

[0028] In operation of the above described air motor 10, compressed air is deli vered to the passage 32 from where it is delivered to the chamber 22. Air is simultaneously delivered to the chamber 25 from passage 32 for delivery to the chamber 17 (with reference to Figure 1 ). At this time, compressed air is also delivered from cavity 22 to the chamber 25 via ducting 30 and 42 to apply pressure to the end face 35 of the member 26 so that compressed air is delivered to chamber 17. The compressed air in the chamber 17 forces the piston 18 in the direction 36. As the pistons 18 are connected by the rod 19, ultimately the piston 18 of the chamber 16 engages the end of the valve member 24 and forces it in the direction 36. In this configuration compressed air is then redirected to the chamber 16 to cause movement of the piston rod 18 in a direction opposite the direction 36. Simultaneously air is directed via valve member 24 away from the end face 35 of valve cavity 25 to the exhaust ducting 29 through valve chamber 22, while air is being directed into the cavity so as to apply pressure to the end face 37 to force the valve member 26 in a direction opposite the direction 36 so that the compressed air from passage 28 is now delivered to the chamber 16. This movement of the valve member 26 also alternately connects the chambers 16 and 17 to the exhaust ducting 29. In particular when compressed air is being delivered to the chamber 16, the chamber 17 is connected to the exhaust ducting 29. However when the chamber 17 receives compressed air, the chamber 16 is connected to the exhaust ducting 29. Accordingly, the valves 51 and 52 are operated to alternately connect the chambers 16 and 17 to the inlet passage 32 and the exhaust passage 33.

[0029] The valve 52 includes a sleeve 55 located in the chamber 25, and within which the valve member 26 is slidably located. Seals 56 sealingly connect the sleeve 55 and member 26.

[0030] The sleeve 55 has ports 61 to 68 which are arranged as follows:

ports 61 and 64 communicate with the ducting 34;

ports 65 and 68 communicate with the ducting 54;

ports 62 and 67 communicate with the ducting 29; and

ports 63 and 66 communicate with the ducting 50.

[0031 ] Accordingly the ports 61 and 64 provide for the flow of the compressed air to and from chambers 16, the ports 65 and 68 provide for the flow of compressed air to and from the chamber 17, the ports 62 and 67 provide the exhaust of air from the chambers 16 and 17, while the ports 63 and 66 provide for the delivery of compressed air to the chambers 16 and 17.

[0032] The seals 72 connect the member 26 and sleeve 55.

[0033] The sleeve 55 may also be a plurality of spacers (rings) located between the seals 56, with the seals 56 connecting the member 26 and base 12. The ports 61 to 68 would be annular with respect to the axis 38. [0034] Figure 2 shows the sequence of movements of the movable valve member 26, from the position at which the valve member 26 is located when the chamber 16 has reached its maximum volume, that is the piston 18 associated therewith has reached its maximum travel.

[0035] When the above has occurred, the valve member 24 is moved to the left (with reference to Figure 1). Upon doing so compressed air is delivered to the chamber 25, in particular compressed air engages the end face 35 of the member 26 to drive the member 26 in the direction 36.

[0036] As the member 26 (position A) initiates movement in the direction 36, the passage 69 of the member 26 will move from connecting ports 63 and 64, to a position at which it connects parts 64 and 65. Simultaneously the passage 71 will move from connecting parts 67 and 68. Compressed air that was previously in the chamber 16 will be at least partly exhausted into the chamber 17 via parts 63 and 64 (position B). Further movement of the member 26 in the direction 36 will isolate the chamber 16 from the chamber 17, while connecting the chamber 17 to a supply of compressed air by connecting the ports 65 and 66 with passage 69.

Simultaneously the passage 70 of the member 26 connects the port 61 , 62 so that the chamber 16 is allowed to exhaust (position C).

[0037] The pilot valve 51 can be replaced with an actuator, such as a servo motor or an electrically operated linear actuator, that is coupled to the member 26 and operated to cause the movement thereof as discussed above.

[0038] The movement and speed at which the member 26 moves between the positions A, B, C and D is governed by the air flow rate provided by the valve 51.

[0039] However once the piston 18, associated with the chamber 17, is at its maximum position in the direction 36, that is the chamber 17 at its maximum volume, piston 18 will have engaged the member 24 and driven it to a position displaced from the position shown in Figure 1, that is a position displaced to the right (position D). Once this occurs compressed air is then delivered to the chamber 25 adjacent the end face 37 to drive the member 26 in a direction opposite direction 36. As this occurs again the ports 64 and 65 are connected so that compressed air in the chamber 17 can be transferred to the chamber 16, and then subsequently the chamber 16 and 17 isolated with the chamber 17 then connected to the port 67, and the chamber 16 connected to the port 63. That is chamber 17 is able to exhaust, and chamber 16 receiving compressed air.

[0040] The passages 69, 70 and 71 are annular with their central axis, the axis 38. The passages 69, 70 and 71 are located at spaced positions along the axis 38, with the ports 61 to 68 also located at spaced positions longitudinally relative to the axis 38.

[0041 ] The base 12 includes a fifth ducting 38 that extends between the opposite faces 13.

[0042] Each cap 14 is sealingly connected to its associated adjacent face 13 by means of a seal 39. Each seal 39 includes an annular portion 40 that slidably engages the piston rod 19, as well as having a weakened portion 41 that is aligned with the ducting 38. There is also ducting (depressions) 42 that provide for the ducting of air to be located adjacent the faces 35 and 37 when the valve member 26 is to be moved. Holes 45 and 49 alternately provide for the valve member 24 to extend therethrough, along with aligning with ducting 34 to provide for air flow to and from chambers 16 and 17. On the side of chamber 17, hole 45 provides the air flow while hole 49 allows the valve member 24 to extend therethrough. On the side of chamber 16, hole 49 provides the air flow while hole 45 allows the valve member 24 to extend therethrough.

[0043] The base 12 has faces 46 that are engaged by the member 31. The faces 46 are generally perpendicular to the faces 13 and are therefore generally parallel to the axis 20.

[0044] The ducting 30, 34 38, 50 and 54 can be formed through the faces 13 and 46.

[0045] In the above described preferred embodiment rather than totally exhausting the compressed air from the chambers 16 and 17, at least part of the compressed air is transferred to the other chamber to aid in driving the pistons 18. Accordingly less compressed air is used to operate the motor 10.