WO2017079792A1

WO2017079792A1 - A piston and cylinder system

Info

Publication number: WO2017079792A1
Application number: PCT/AU2016/051068
Authority: WO
Inventors: Noel Hughes; Leonardo LAFORGIA
Original assignee: Elite Attachments Australia Pty Ltd
Priority date: 2015-11-09
Filing date: 2016-11-08
Publication date: 2017-05-18

Abstract

A piston and cylinder system (10), the cylinder (12) including a closed end (14) and an open end (16). The piston (18) is movable in an axial direction within the cylinder (12) between a fully extended position and a fully retracted position. The piston (18) and cylinder (12) define first and second chambers (20), (22) within the cylinder (12), (20), with the first chamber (20) defined between a cylinder closed end wall (24) at the closed end (14) of the cylinder (12), a cylinder sidewall (26) and the piston (18). The second chamber (22) is defined between a cylinder open end wall (30) at the open end (16) of the cylinder (12), the cylinder side wall (26) and the piston (18). A first fluid supply port (34) is provided for supplying fluid to the first chamber (20) to facilitate movement of the piston (18) towards the fully extended position; and a second supply port (36) is provided for supplying fluid to the second chamber (22) to facilitate movement of the piston (18) towards the fully retracted position. A biasing means (38) is provided at least partially within the cylinder (12) and biases the piston (18) towards the fully extended position.

Description

A PISTON AND CYLINDER SYSTEM

Introduction

[0001 ] The present invention relates to a piston and cylinder system. More particularly, the invention relates to a hydraulic piston and cylinder system inside a fully automatic hydraulic quick hitch and will hereinafter be generally described in this context.

Background of Invention

[0002] Hydraulic piston and cylinder systems are utilised in a myriad of applications. In some applications the piston and cylinder system is utilised as an actuator arrangement, or at least part of an actuator arrangement. As such, hydraulic fluid may be fed under pressure into the cylinder on one side of the piston in order to move the piston in a desired axial direction relative to the cylinder, so as to obtain a desired output from the system.

[0003] In many applications, hydraulic fluid may be selectively fed into the cylinder on either side of the piston, such that pressurised hydraulic fluid fed on one side of the piston moves the piston in one axial direction, and pressurised hydraulic fluid fed into the cylinder on the other side of the piston moves the piston in the opposite axial direction. The amount of fluid pressure required to move the piston will depend on the particular application.

[0004] In some applications, it would be desirable to bias the piston away from one or both of a fully retracted position within the cylinder and a fully extended position within the cylinder in the event of, for example, a loss of hydraulic fluid pressure. In this regard, an unintended loss of hydraulic pressure is highly undesirable, especially in the context of operator safety issues and possible damage to equipment and machines. Unintended pressure losses may be due to any number of factors, such as wear and tear causing gradual degradation of the cylinder seals, wear of the sliding surfaces of the cylinder internals, or any other interruption to the pressurised hydraulic fluid supply - although the net effect is the same - the hydraulic system is rendered temporarily inoperable until the problem is rectified. [0005] It would therefore be desirable to provide a way of addressing any sudden and unexpected loss of hydraulic fluid pressure from a piston and cylinder system.

[0006] It would also be desirable to provide a piston and cylinder system in which the piston is biased away from one or both of a fully retracted position within the cylinder and a fully extended position within the cylinder in the event of a loss of hydraulic fluid pressure. It would be further desirable to do so in a way that is less complicated in design, and less likely to be damaged, than current conventional systems.

Summary of Invention

[0007] According to a broad aspect of the present invention, there is provided a piston and cylinder system. The system includes a cylinder, the cylinder including a closed end and an open end. A piston is movable in an axial direction within the cylinder between a fully extended position and a fully retracted position. The piston and cylinder define first and second chambers within the cylinder. The first chamber is defined between a cylinder closed end wall at the closed end of the cylinder, a cylinder sidewall and the piston. The second chamber is defined between a cylinder open end wall at the open end of the cylinder, the cylinder side wall and the piston. The system further includes a first fluid supply port for supplying fluid to the first chamber to facilitate movement of the piston towards the fully extended position; and a second supply port for supplying fluid to the second chamber to facilitate movement of the piston towards the fully retracted position. The system also includes a biasing means provided at least partially within the cylinder and biasing the piston towards the fully extended position.

[0008] It is envisaged that, in use, the first fluid supply port supplies hydraulic fluid to the first chamber; and the second fluid supply port supplies hydraulic fluid to the second chamber. As such, the system is hydraulically operable.

[0009] In one preferred embodiment, the biasing means includes a compression spring. In such an embodiment, the compression spring may extend through the cylinder from a first spring seat provided on or associated with the closed end wall of the cylinder, and a second spring seat movable with the piston. [0010] The first spring seat may include a stem extending axially from the closed end wall of the cylinder through the cylinder, with the spring located about the stem.

[001 1 ] In one embodiment, the piston includes a piston bore for receiving the biasing means.

[0012] In a preferred embodiment, the piston includes a connecting arm mounted to the piston, and extending from the cylinder open end wall, with the connecting arm including a connecting arm bore for receiving the spring. Such an arrangement can, in at least some arrangements, be considered as a type of hydraulically operated actuator, with the connecting arm providing a mechanical output for the system.

[0013] The second spring seat may be provided within a closed end of the connecting arm bore. In such an arrangement, the connecting arm bore may be aligned, such as coaxially aligned, with the piston bore.

[0014] The first chamber is preferably fluidly connected to both the connecting arm bore and the piston bore.

[0015] The provision of a biasing means is desirable, because it may be utilised as a failsafe mechanism to limit movement of the piston to the fully retracted position (or at least bias the piston away from the fully retracted position) in the event of a fluid supply failure through the first supply port to the first chamber.

[0016] The applicant also contemplates embodiments of the system including a second biasing means. The second biasing means may be provided for, in use, biasing the piston away from the fully extended position. In this way, the second biasing means may also be utilised as a failsafe mechanism - to limit movement of the piston to the fully extended position (or at least bias the piston away from the fully extended position) in the event of a fluid supply failure through the second supply port to the second chamber.

[0017] Some embodiments contemplated by the applicant provide a second biasing means in the second chamber. In such arrangements, the second biasing means may include a compression spring provided between the piston and a seat provided on the open end wall. [0018] Other embodiments of the system utilise a second biasing means provided externally of the second chamber. In one such embodiment, a cam is pivotably mounted about a mount axis to an external mount, with the cylinder sidewall proximate the closed end of the cylinder pivotably mounted to the cam about a cylinder pivot axis. The mount axis is spaced from the cylinder pivot axis. A cam biasing means is mounted to the cam about the mount axis. The cam mounted biasing means biases the closed end of the cylinder towards a failsafe position (or inoperative position). The arrangement is such, that pivoting of the cam displaces the closed end of the cylinder axially and radially away from the failsafe (or inoperative) position. In one preferred form, the cam biasing means includes a torsion spring mounted about the mount axis.

[0019] Another embodiment of the system utilises a second biasing means externally of the second chamber, a compression spring is mounted into the head end of the cylinder to provide constant force on the front cylinder connection pin to bias the cylinder arrangement forward providing a failsafe position for the cylinder over the front entry yoke of the coupler.

[0020] The applicant envisages the piston and cylinder system being utilised in a coupler having a body portion and a pair of jaws, such as used to connect to respective pins of a tool, for example, a digging bucket. The coupler may be provided on the arm of a utility vehicle, such as an excavator or digger. One advantage of such an application is that the piston and cylinder arrangement may be utilised to provide a failsafe locking arrangement for locking the coupler to each tool pin, thereby avoiding the potentially dangerous situation of the coupler becoming detached from one or both of the pins in the event that the supply of fluid through either of the first or second fluid supply ports is inadvertently interrupted. With a failure in the hydraulic fluid system the internal spring in the piston and cylinder is designed to hold the rear sliding jaw in position against the rear attachment pin. The internal spring inside the cylinder is not designed to support large loads from the bucket or attachment as is typically the case in other couplers out in the market place. The spring is a light control spring with the only purpose to support the rear sliding jaw. Brief Description of Drawings

[0021 ] It will be convenient to hereinafter describe preferred embodiments of the invention with reference to the accompanying drawings. The particularity of the drawings is to be understood as not limiting the preceding broad description of the invention.

[0022] Figure 1 is a side view of a piston and cylinder system with the piston shown in the fully extended position relative to the cylinder.

[0023] Figure 2 is a side view of the piston and cylinder system shown in Figure 1 , with the piston shown in another position relative to the cylinder when compared to that of Figure 1 .

[0024] Figure 3 is a side view of the piston and cylinder system shown in Figure 1 , with the piston shown in yet another position relative to the cylinder.

[0025] Figure 4 is a side view of the piston and cylinder system shown in Figure 1 , with the piston shown in the fully retracted position relative to the cylinder.

[0026] Figure 5 is a side view of the piston and cylinder system shown in Figure 1 , when incorporated into a coupler.

[0027] Figure 6 is another side view of a piston and cylinder system shown in

Figure 5, when incorporated into the coupler.

[0028] Figure 7 is a side view of a piston and cylinder system according to a second embodiment of the present invention shown in the fully extended position.

[0029] Figure 8 is a side view of the piston and cylinder system shown in Figure 7, with the piston shown in another position relative to the cylinder when compared to that of Figure 7.

[0030] Figure 9 is a side view of the piston and cylinder system shown in Figure 7, with the piston shown in the fully retracted position relative to the cylinder. [0031 ] Figure 10 is a side view of the piston and cylinder system shown in Figure

7 shown in the fully retracted position, according to the second embodiment of the present invention when incorporated into another coupler.

[0032] Figure 1 1 is a side view of the piston and cylinder system shown in Figure

7, shown in another position according to the second embodiment of the present invention when incorporated into the same coupler.

[0033] Figure 12 is a side view of a piston and cylinder system according to a third embodiment of the present invention shown in the fully extended position.

[0034] Figure 13 is a side view of the piston and cylinder system shown in Figure

12, with the piston shown in another position relative to the cylinder when compared to that of Figure 12.

[0035] Figure 14 is a side view of the piston and cylinder system shown in Figure

12, with the piston shown in the fully retracted position when compared with that of Figure 12.

[0036] Figure 15 is an exploded view of the secondary biasing system shown on the back end (or right-hand end) of the piston and cylinder system shown in Figure 12.

[0037] Figure 16 is a side view of the piston and cylinder system shown in Figure

12, with the piston shown in another position relative to the cylinder, and when incorporated into another coupler.

[0038] Figure 17 is a side view of the piston and cylinder system shown in Figure

12, shown in the fully retracted position according to the third embodiment of the present invention when incorporated into the coupler shown in Figure 16.

[0039] Figure 18 is a free body diagram of the internal spring inside the piston and cylinder relative to the coupler, bucket and load.

[0040] Figure 19 is a diagram of a bucket attached to a coupler showing the internal compression spring separated from the piston and cylinder. [0041 ] Figure 20 is a diagram of the bucket shown in Figure 19 when attached to the coupler, with the coupler also shown attached to digger arms.

[0042] Figure 21 is a diagram similar to that shown in Figure 20, and additionally showing magnified portions of the arrangement of the whole setup.

Detailed Description

[0043] Referring to the embodiment shown in Figures 1 to 6, there is illustrated a piston and cylinder system 10. The system 10 includes a cylinder 12. The cylinder 12 includes a closed end 14 and an open end 16. A piston 18 is movable in an axial direction within the cylinder 12 between a fully extended position shown in Figure 1 , and a fully retracted position shown in Figure 4.

[0044] The piston 18 and cylinder 12 define first and second chambers 20, 22, respectively, within the cylinder 12.

[0045] The first chamber 20 is defined between a cylinder closed end wall 24 at the closed end 14 of the cylinder 12, a cylinder sidewall 26 and the surface 28 of the piston 18. The second chamber 22 is defined between a cylinder open end wall 30 at the open end 16 of the cylinder 12, the cylinder side wall 26 and the surface 32 of the piston 18.

[0046] The closed end of the cylinder 14 may include a pinned attachment point

(shown) 15 or bolted attachment point to connect to the coupler body 64.

[0047] A first fluid supply port (indicated diagrammatically as item 34) is provided for supplying fluid in the form of a hydraulic fluid to the first chamber 20 to facilitate movement of the piston 18 in the direction X1 towards the fully extended position (as shown in Figure 1 ).

[0048] A second supply port (indicated diagrammatically as item 36) is provided for supplying fluid in the form of a hydraulic fluid to the second chamber 22 to facilitate movement of the piston 18 in the direction X2 towards the fully retracted position (shown in Figure 4 ).

[0049] An operator control would be provided for separately controlling the flow of hydraulic fluid through the ports 34, 36 via a bolt on external pilot operated check valve 31 .

[0050] A biasing means in the form of a coiled compression spring 38 is provided.

It can be seen that the spring 38 is substantially fully enclosed within the cylinder 12 in Figure 4, but only partially within the cylinder 12 in Figures 1 , 2, 3, 5, and 6. The spring 38 biases the piston 18 from the fully retracted position towards the fully extended position. The spring 38 extends axially through the cylinder 12 from a first spring seat 40 provided on the closed end wall 24 of the cylinder 12, and a second spring seat 42 movable with the piston 18.

[0051 ] The first spring seat 40 includes a stem 44 extending axially from the closed end wall 24 through the cylinder 12, with the spring 38 located about the stem 44.

[0052] The piston 18 includes a piston bore 46 for receiving the spring 38 there through.

[0053] The piston 18 includes a connecting arm 48 mounted to and for movement with the piston 18. The connecting arm 48 may be connected via attachment point 50 through an aperture 49 in the open end wall 30 to a moving, slider 52. In the illustrated embodiment of Figures 5 and 6, the connecting arm 48 is connected to the slider 52 of a coupler 54 (to be discussed more fully below). The connecting arm 48 extends through an aperture 49 from the cylinder open end wall 30. The connecting arm 48 includes a bore 56 for receiving the spring 38. The bore 56 is coaxially aligned with the piston bore 46. It can be seen that the second spring seat 42 is provided within a closed end 58 of the bore 56.

[0054] The system 10 can be considered as a hydraulic actuator arrangement (or at least a part thereof) for generating a movement of the slider 52 to desired operating positions, when required. It is to be appreciated that the relative dimensions of the illustrated embodiment(s) can be altered to suit a specific application.

[0055] It is to be appreciated that the first chamber 20 is fluidly connected to both the connecting arm bore 56 and the piston bore 46.

[0056] The provision of spring 38 is desirable because it may be utilised as a failsafe mechanism to bias the piston 18 away from the fully retracted position in the event of a fluid supply failure through the first supply port 34 to the first chamber 20. Furthermore, being internally mounted, it does so in a way that reduces the opportunity for the spring 38 to sustain damage or be compromised by dirt or debris, which may occur if the spring 38 was externally mounted to the system 10.

[0057] In this illustrated embodiment a second biasing means is also provided within the second chamber 22, in the form of a coiled compression spring 60. The spring is seated on the inner surface 62 of the open end wall 30 and at the other end against the surface 63 of a sliding spring retainer plate 65. In the event of a fluid supply failure use, the spring 60 biases the piston 18 away from the fully extended position. In this way, the spring 60 may also be utilised as a failsafe mechanism - to bias the piston 18 away from the fully extended position in the event of a fluid supply failure. The spring 60 is compressed in the position Figure 1 and this can only occur when the cylinder is functioning normally. In the event of a fluid supply failure the spring 60 will bias the piston 18 away from the fully extended position as shown in Figure 2. The spring 60 is not compressed in the system operating positions shown in Figures 2 to 5 and so is exerting no bias on the piston 18 when the piston is in these positions.

[0058] The applicant envisages the piston and cylinder system 10 being utilised in the application illustrated in Figures 5 and 6, wherein it is incorporated into the coupler 54. The coupler 54 has a body portion 64, (to which the cylinder 12 is securely mounted) through an attachment pin 17 connecting pin aperture 19 to the front of the coupler body 68 connecting into a pair of jaws to capture the attachment pins 72 and 74. As previously stated, the connecting arm 48 is connected to a slider 52 of the coupler 54 via a pin 70. The slider 52 is movable relative to the coupler 54 by the piston 18 and connector arm 48 in response to a change in hydraulic fluid pressure supplied though the ports 34, 36. Movement of the slider 52 allows for connection or disconnection of the coupler 54 to the pins 72, 74 of a digging tool (not shown) provided on the arm of a vehicle such as an excavator or digger. The provision of springs 38, 60 in such an application is highly desirable from a safety point of view when the coupler 54 is connected to the pins 72, 74. This is because it prevents inadvertent release of the pins 72, 74 in the event that the supply of pressurised hydraulic fluid in chamber 20 fails. This is because the springs 38, 60 bias axial displacement of the connecting arm 48 and piston 18 relative to the cylinder 12 (in the absence of hydraulic pressure overcoming the spring forces), thereby retaining the slider in a safely locked position with both pins 72, 74.

[0059] Control of the hydraulic system would typically be by an operator seated within the cabin of the vehicle.

[0060] It is to be appreciated that the dimensions of the system 10, the operating pressure of the hydraulic fluid supplied to each of the chambers 20, 22, and the dimensions of the springs 38, 60 may each be selected to suit a specific application.

[0061 ] A second embodiment of the piston and cylinder system 1 10 is illustrated in

Figures 7 to 1 1 . Many features of the system 1 10 are similar or the same as features of the system 10 illustrated in Figures 1 to 6. Therefore, like features illustrated in Figures 7 to 1 1 are provided with the prefix ".

[0062] The system 1 10 includes a cylinder 1 12 having a closed end 1 14 and an open end 1 16. Piston 1 18 is movable in an axial direction within the cylinder 1 12 between a fully extended position (shown in Figure 7) and a fully retracted position (shown in Figure 9).

[0063] As with the embodiment illustrated in Figures 1 to 6, the piston 1 18 and cylinder 1 12 define first and second chambers 120, 122, respectively, within the cylinder 1 12. The first chamber 120 is defined between a cylinder closed end wall 124 at the closed end 1 14 of the cylinder 1 12, a cylinder sidewall 126 and the surface 128 of piston 1 18. The second chamber 122 is defined between a cylinder open end wall 130 at the open end 1 16 of the cylinder 1 12, the cylinder side wall 126 and the surface 132 of piston [0064] The system 1 10 also includes a first fluid supply port (diagrammatically indicated as item 134) for supplying fluid in the form of hydraulic fluid to the first chamber 120. In doing so (and presuming the fluid pressure is greater in the first chamber 120 compared to that in the second chamber 122) the piston 1 18 will move towards the fully extended position of Figure 7.

[0065] A second supply port (diagrammatically indicated as item 136) is provided for suppling fluid in the form of hydraulic fluid to the second chamber 122. This facilitates movement of the piston 1 18 towards the fully retracted position shown in Figure 9, presuming of course that the fluid pressure in chamber 122 is greater than that in chamber 120. The supply of fluid to the chambers 120, 122 via the bolt on check valve arrangement 131 would be separately controlled via an operator control, typically from the cabin of an associated vehicle.

[0066] A biasing means in the form of a coiled compression spring 138 is provided. The spring 1 38 biases the piston 1 18 towards the fully extended position. The spring 138 extends axially through the cylinder 1 12 from a first spring seat 140 provided on the closed end wall 124 of the cylinder 1 12, and a second spring seat (to be discussed below) movable with the piston 1 18.

[0067] The first spring seat 140 includes a stem 144 extending axially through the cylinder 1 12 from the closed end wall 124. The spring 138 is located about the stem 144.

[0068] The piston is provided with a bore 146 for receiving the spring 138 there through.

[0069] A connecting arm 148 is mounted to and extends from the piston 1 18 through an aperture 149 provided the open end wall 130. The connecting arm 148 includes a bore 156 for receiving the spring 138. The second spring seat 142 is provided within the closed end 158 of the connecting arm bore 156. The system 1 10 can be considered as a hydraulic actuator arrangement (or at least a part thereof) for generating a movement of the connecting arm 148 to desired operating positions, when required.

[0070] The first chamber 120 is fluidly connected to the connecting arm bore 156 and to the piston bore 146. [0071 ] As stated previously with regard to the embodiment illustrated in Figures 1 to 6, the provision of spring 138 is desirable, particularly if utilised as a failsafe mechanism to bias the piston 1 18 away from the fully retracted position in the event of a (pressurised) fluid supply failure through the first supply port 134 to the first chamber 120.

[0072] The system 1 10 also includes a second biasing means. However, unlike the second biasing means (in the form of internal compression spring 60) shown in embodiment Figures 1 to 6, the second biasing means shown in Figures 7 to 1 1 is a torsion spring 160 mounted external to the cylinder 1 12 (rather than within the cylinder 1 12). The spring 160 is provided as a failsafe mechanism to lock the front attachment pin 174 in the event of a fluid supply failure.

[0073] A cam 161 is provided to capture the front attachment pin 174 in the event of fluid supply failure. The cam 161 is pivotably mounted about a mount axis 163 to an external mount 165 provided on a the front body portion 164 of a coupler 154. The cylinder sidewall 126 proximate the closed end 1 14 of the cylinder 1 12 is pivotably mounted to the cam 161 about a cylinder pivot axis 167. The mount axis 163 is spaced from the cylinder pivot axis 167. The torsion spring 160 is mounted to the cam 161 about the mount axis 163. The torsion spring biases the closed end 1 14 of the cylinder 1 12 and cam 161 towards the failsafe position shown in Figure 1 1 . The arrangement is such, that pivoting of the cam 161 displaces the closed end of the cylinder axially X2 and radially Y2 away from the failsafe position (that is from the arrangement shown in Figure 1 1 to that shown in Figure 10). The distances X2 and Y2 are typically only a few millimetres, and can be seen when comparing Figure 10 with Figure 1 1 .

[0074] The piston and cylinder system 1 10 is shown in Figures 10 and 1 1 when incorporated into a second coupler embodiment. As with the arrangement shown in Figures 1 to 6, the applicant envisages the system 1 10 may be incorporated into the coupler 154 having body portion 164, a slider 152, and a cam 161 connecting into a pair of jaws 166 and 168. This may be used to connect to respective pins 172, 174 of a tool, for example, a digging bucket, with the coupler 154 provided on the arm of a utility vehicle, such as an excavator or digger.

[0075] The connecting arm 148 is connected to a slider 152 of the coupler 154 via a pin 170. The slider 152 is movable relative to the coupler 154 by the piston 1 18 and connector arm 148 in response to a change in hydraulic fluid pressure supplied though the ports 134, 136. Movement of the slider 152 allows for connection or disconnection of the coupler 154 to the pin 172 (but not to the pin 174) of a digging tool (not shown) provided on the arm of a vehicle such as an excavator or digger. Disconnection of pin 174 is achieved by pivoting of the cam 161 so as to axially and radially displace the closed end 1 14 of the cylinder 1 12 away from the failsafe position shown in Figure 1 1 to that shown in Figure 10.

[0076] The provision of springs 138, 160 in system 1 10 is highly desirable from a safety point of view when the coupler 154 is connected to the pins 172, 174. This is because it prevents inadvertent release of the pins 172, 174 in the event that the supply of pressurised hydraulic fluid to the cylinder 1 12 fails. This is because the springs 138, 160 bias the system 1 10 into a failsafe position in the event of inadvertent loss of fluid pressure.

[0077] A third embodiment of the piston and cylinder system 210 is illustrated in

Figures 12 to 17. Many features of the system 210 are similar or the same as features of the system 10 illustrated in Figures 1 to 6 and system 1 10 illustrated in Figures 7 to 1 1 . Therefore, like features illustrated in Figures 12 to 1 7 are provided with the prefix "2".

[0078] The system 210 includes a cylinder 212 having a closed end 214 and an open end 216. Piston 218 is movable in an axial direction within the cylinder 212 between a fully extended position (shown in Figure 12) and a fully retracted position (shown in Figure 14).

[0079] As with the embodiment illustrated in Figures 1 to 6, the piston 218 and cylinder 212 define first and second chambers 220, 222, respectively, within the cylinder 212. The first chamber 220 is defined between a cylinder closed end wall 224 at the closed end 214 of the cylinder 212, a cylinder sidewall 226 and the surface 228 of piston 218. The second chamber 222 is defined between a cylinder open end wall 230 at the open end 216 of the cylinder 212, the cylinder side wall 226 and the surface 232 of piston 218.

[0080] The system 210 also includes a first fluid supply port (diagrammatically indicated as item 234) for supplying fluid in the form of hydraulic fluid to the first chamber 220. In doing so (and presuming the fluid pressure is greater in the first chamber 220 compared to that in the second chamber 222) the piston 218 will move towards the fully extended position of Figure 12.

[0081 ] A second supply port (diagrammatically indicated as item 236) is provided for suppling fluid in the form of hydraulic fluid to the second chamber 222. This facilitates movement of the piston 218 towards the fully retracted position shown in Figure 14, presuming of course that the fluid pressure in chamber 222 is greater than that in chamber 220. The supply of fluid to the chambers 220, 222 via the bolt on check valve arrangement 231 would be separately controlled via an operator control, typically from the cabin of an associated vehicle.

[0082] A biasing means in the form of a coiled compression spring 238 is provided. The spring 238 biases the piston 218 towards the fully extended position. The spring 238 extends axially through the cylinder 212 from a first spring seat 240 provided on the closed end wall 224 of the cylinder 212, and a second spring seat (to be discussed below) movable with the piston 218.

[0083] The first spring seat 240 includes a stem 244 extending axially through the cylinder 212 from the closed end wall 224. The spring 238 is located about the stem 244.

[0084] The piston is provided with a bore 246 for receiving the spring 238 there through.

[0085] A connecting arm 248 is mounted to and extends from the piston 218 through an aperture 249 provided in the open end wall 230. The connecting arm 248 includes a bore 256 for receiving the spring 238. The second spring seat 242 is provided within the closed end 258 of the connecting arm bore 256. The system 210 can be considered as a hydraulic actuator arrangement (or at least a part thereof) for generating a movement of the connecting arm 248 to desired operating positions, when required.

[0086] The first chamber 220 is fluidly connected to the connecting arm bore 256 and to the piston bore 246. [0087] As stated previously with regard to the embodiment illustrated in Figures 1 to 6, the provision of spring 238 is desirable, particularly if utilised as a failsafe mechanism to bias the piston 218 away from the fully retracted position in the event of a (pressurised) fluid supply failure through the first supply port 234 to the first chamber 220.

[0088] The system 210 also includes a second biasing means. However, unlike the second biasing means (in the form of internal compression spring 60) shown in embodiment Figures 1 to 6, the second biasing means shown in Figures 12 to 1 7 is a compression spring 260 behind the closed end 214 of the cylinder 212 (rather than within the cylinder 212). The spring 260 is provided as a failsafe mechanism, locking the front attachment pin 274 in the event of a fluid supply failure.

[0089] A spring housing 215 and connection pin seat 276 are provided. The attachment pin 217 is captive between the spring housing 215 and the connection pin seat 276. The compression spring 260 is seated on the inner surface 263 of the connection pin seat 276 and against the inner spring seat surface 219 of the end cap 277. In use, the compression spring 260 biases the closed cylinder end 214 and spring housing 215 towards the failsafe position shown in Figure 16. In this way, the spring 260 may also be utilised as a failsafe mechanism locking the front attachment pin 274. The arrangement is such, that when the cylinder 210 is nearing the fully retracted position (Figure 17) and the slider 252 reaches the end of its travel in the guide slot, the spring housing 215 is displaced away from the failsafe position shown in Figure 1 6 to that shown in Figure 17. In this position the compression spring 260 is nearly fully compressed between the pin seat 276 and the spring housing 215.

[0090] The applicant envisages the piston and cylinder system 210 being incorporated into the body portion 264 of the coupler 254. This may be used to connect to respective pins 272, 274 of a tool, for example, a digging bucket, with the coupler 254 provided on the arm of a utility vehicle, such as an excavator or digger.

[0091 ] The cylinder 212 is securely mounted to the body portion 264 through an attachment pin 217 connecting pin aperture 219 to the front of the coupler body 268. The connecting arm 248 is securely connected to the slider 252 through attachment pin 270. The slider 252 is movable relative to the coupler 254 by the piston 218 and connector arm 248 in response to a change in hydraulic fluid pressure supplied though the ports 234, 236. Movement of the slider 252 allows for connection or disconnection of the coupler 254 to the pin 272 (but not to the pin 274) of a digging tool (not shown) provided on the arm of a vehicle such as an excavator or digger. Disconnection of pin 274 is achieved by movement of the cylinder 212 and spring housing 215 away from the failsafe position shown in Figure 16 to that shown in Figure 17 by hydraulic fluid pressure supplied through ports 236 into chamber 222.

[0092] The provision of springs 238, 260 in system 210 is highly desirable from a safety point of view when the coupler 254 is connected to the pins 272, 274. This is because it prevents inadvertent release of the pins 272, 274 in the event that the supply of pressurised hydraulic fluid to the cylinder 212 fails This is because the springs 238, 260 bias the system 210 into a failsafe position in the event of inadvertent loss of fluid pressure.

[0093] The piston and cylinder system 10/1 10/210 of the present invention advantageously provides a way of addressing any sudden and unexpected loss of hydraulic fluid pressure from a piston and cylinder system.

[0094] Moreover, the system 10/1 10/210 is advantageously designed such that the piston is biased away from at least the fully retracted position and, in some embodiments also from the fully extended position, in the event of a loss of hydraulic fluid pressure. Moreover, it does so with at least some or all of the biasing componentry located within the system, meaning that it is less likely to be damaged, even when operating in harsh working environments. It is also considered that the system 10/1 10/210 is of a less complicated design than conventional systems, and so therefore potentially more cost effective to manufacture, assemble, maintain, repair and replace when necessary. It is also potentially less likely to fail because it avoids the complicated designs of conventional arrangements.

[0095] Finally, it is to be understood that various alterations, modifications and/or additions may be introduced into the construction and arrangement of the parts previously described without departing from the spirit or ambit of this invention.

[0096] Future patent applications may be filed in Australia or overseas on the basis of or claiming priority from the present application. It is to be understood that the following provisional claims are provided by way of example only, and are not intended to limit the scope of what may be claimed in any such future application. Features may be added to or omitted from the provisional claims at a later date so as to further define or re-define the invention or inventions.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS

1 . A piston and cylinder system:

the cylinder including a closed end and an open end;

the piston movable in an axial direction within the cylinder between a fully extended position and a fully retracted position;

the piston and cylinder defining first and second chambers within the cylinder, with the first chamber defined between a cylinder closed end wall at the closed end of the cylinder, a cylinder sidewall and the piston; and the second chamber defined between a cylinder open end wall at the open end of the cylinder, the cylinder side wall and the piston;

a first fluid supply port for supplying fluid to the first chamber to facilitate movement of the piston towards the fully extended position; and a second supply port for supplying fluid to the second chamber to facilitate movement of the piston towards the fully retracted position; and

a biasing means provided at least partially within the cylinder and biasing the piston towards the fully extended position.

2. A piston and cylinder system according to claim 1 , wherein, in use, the first fluid supply port supplies hydraulic fluid to the first chamber; and the second fluid supply port supplies hydraulic fluid to the second chamber.

3. A piston and cylinder system according to claim 1 or 2, wherein the biasing means including a compression spring.

4. A piston and cylinder system according to claim 3, wherein the compression spring extends axially through the cylinder between a first spring seat provided on the closed end wall of the cylinder and a second spring seat associated with the piston.

5. A piston and cylinder system according to claim 4, wherein the first spring seat includes a stem extending axially from the closed end wall of the cylinder through the cylinder, with the spring located about the stem.

6. A piston and cylinder system according any one of claims 3, 4 or 5, the piston including a piston bore for receiving the spring.

7. A piston and cylinder system according to any one of claims 4 to 6, the piston including a connecting arm mounted to the piston, and extending from the cylinder open end wall, the connecting arm including a connecting arm bore for receiving the spring, and the second spring seat provided within a closed end of the connecting arm bore.

8. A piston and cylinder system according to claim 7, the connecting arm bore aligned with the piston bore.

9. A piston and cylinder system according to claim 7 or 8, wherein the first chamber is fluidly connected to the connecting arm bore and the piston bore.

10. A piston and cylinder system according to any one of the preceding claims, wherein the biasing means is provided as a failsafe mechanism to bias the piston away from the fully retracted position in the event of a fluid supply failure through the first supply port to the first chamber.

1 1 . A piston and cylinder system according to any one of the preceding claims, including a second biasing means, the second biasing means provided for, in use, biasing the piston away from the fully extended position.

12. A piston and cylinder system according to claim 1 1 , wherein the second biasing means is provided as a failsafe mechanism to bias the piston away from the fully extended position in the event of a fluid supply failure through the second supply port to the second chamber.

13. A piston and cylinder system according to claim 1 1 or 12, wherein the second biasing means is provided in the second chamber.

14. A piston and cylinder system according to any one of claims 1 1 to 13, wherein the second biasing means includes a compression spring provided between the piston and a seat provided on the open end wall.

15. A piston and cylinder system according to claim 1 1 or 12, including a cam pivotably mounted about a mount axis to an external mount; and wherein the cylinder sidewall proximate the closed end of the cylinder is pivotably mounted to the cam about a cylinder pivot axis, with the mount axis spaced from the cylinder pivot axis.

16. A piston and cylinder system according to claim 15, wherein the second biasing means is mounted to the cam about the mount axis and biases the closed end of the cylinder towards a failsafe position.

17. A piston and cylinder system according to claim 16, wherein pivoting of the cam displaces the closed end of the cylinder axially and radially away from the failsafe position.

18. A piston and cylinder system according to any one of claims 15 to 17, wherein the second biasing means includes a torsion spring.

19. A piston and cylinder system according to any one of claims 1 to 10, including a second biasing means, wherein the second biasing means includes a compression spring provided in a spring housing, the spring housing mounted to an external surface of the cylinder.

20. A piston and cylinder system according to claim 19, wherein the compression spring biases the spring housing and cylinder towards a failsafe position, whereby inadvertent release of a front attachment pin from an associated coupler is prevented.

21 . A piston and cylinder system according to any one of the preceding claims, when incorporated into a coupler having a body portion and a pair of pin connection jaws.

22. A piston and cylinder system according to claim 21 , wherein the pair of twin lock hitches is used to connect to respective pins of a tool, such as a digging bucket.

23. A piston and cylinder system according to claim 21 or 22, wherein the coupler is provided on an arm of a utility vehicle, such as an excavator or digger.