Earth-working machine

Abstract: The machine, e.g. an excavator comprises coupling 18 for releasably connecting tools 19 to an articulated arm 13. The coupling includes a first coupling members 16 supported on the arm 13, a second coupling member 17 provided on each of the tools 19, a locking member 38 provided on the first coupling member 16 and movable between lock and release positions, a spring 39 arranged between the first coupling member 16 and the locking member 38 for urging the locking member 38 into the lock position, and a hydraulically operated release mechanism 34 provided on the first coupling member 16 for moving the locking member 38 into the release position in opposition to the force of the spring 39. Hydraulic fluid at a pressure relief pressure level is applied through a first non-return valve 59 to release the locking member 38 and permit detachment of one tool 19 and attachment of another tool 19; the pressurized hydraulic fluid is then released through a second non-return valve to return the locking member 38 into the lock position, thereby retaining the newly attached tool 19 under pressure of the spring 39.

Description: This invention relates to an earth-working machine of the kind used, for example, for excavating, digging, rock-drilling and hammering operations and equipped with exchangeable tools appropriate for such work. More specifically, the invention is concerned with connecting a said tool to a tool support of the machine or disconnecting the tool therefrom, the operation involving moving a first coupling member provided on the tool support into or out of engagement with a second coupling member provided on the tool. The invention is also concerned with a locking member for securing the coupling members in the engaged position, the locking member being movable between lock and release positions. US-A-4, 136, 792 describes a quick-attachment device for a lifting tractor having controls provided at an operator seat for effecting movement of a first coupling member pivoted to a lifting arm which is in turn pivoted to the support structure constituted by the tractor. The controls enable the first coupling member to be moved into engagement with a second coupling member provided on a tool to be connected to the lifting arm, the movement terminating when the first coupling member abuts a stop on the second coupling member. At that stage a locking member, being a spring-loaded pin provided on the first coupling member, registers with a hole in the second coupling member and is urged thereinto by the spring, the locking member thereby attaining a lock position. The pin can be withdrawn from the lock position into a release position by a cam provided on the first coupling member. The cam can only be operated manually. Thus the locking member cannot be moved into the release position by means of the controls and the operator has to leave the tractor when it becomes necessary to disconnect the tool from the lifting arm. This is a particular disadvantage when there is a need to exchange one tool for another. The invention claimed herein overcomes that difficulty in that it makes it possible to operate the locking member entirely by means of controls provided on the support structure. EP-A-0 273 828 describes a machine being a mechanical shovel having an arm to which an excavating tool is connectable by means of a coupling securable in the engaged position by a locking member movable between lock and release positions by a first double-acting hydraulic motor having two hydraulic flow lines each acting as a feed or return line depending on the direction in which the motor is actuated. The coupling is engageable and disengageable by means of a second hydraulic motor having two hydraulic flow lines each acting as a feed or return line depending on the direction in which the second motor is actuated. Pressure for moving the locking member into the lock position is producable both by a spring and by a hydraulic connection between one of the lines of the first hydraulic motor and one of the lines of the second hydraulic motor. Pressure for moving the locking member into the release position is producable by a hydraulic connection of the other one of the lines of the first hydraulic motor with a manually operable pump providable in a cabin of the machine. Thus EP-A-0 273 828 requires a hand pump in the cabin of the machine and a hydraulic line between that pump and the first coupling member. This does not facilitate the installation of the coupling arrangement in existing machines. The invention claimed herein overcomes that disadvantage by simplifying the connections between the first and second hydraulic motors as well as simplifying the connection between the hydraulic motors and the controls provided on the support structure. EP-A-0 184 282 describes a quick-release hitch for attaching a tool to the arm of a hydraulic excavator. The hitch comprises a coupling securable in the engaged position by a locking member movable between lock and release positions by a first double-acting hydraulic motor having two hydraulic flow lines each acting as a feed or return line depending on the direction in which the motor is actuated. The coupling is engageable and disengageable by a second hydraulic motor having two hydraulic flow lines each acting as a feed or return line depending on the direction in which the second motor is actuated. A solenoid-operated reversing valve is operable for moving the locking member into the lock position by connecting the one line of the second motor for feed to the one line of the first motor while connecting the other line of the first motor for return to the other line of the second motor, or moving the locking member into the release position by connecting the one line of the second motor for feed to the other line of the first motor while connecting the one line of the first motor for return to the other line of the second motor. The one line of the second motor includes a non-return valve permitting flow only toward the reversing valve, and the other line of the second motor includes a non-return valve permitting flow only away from the reversing valve. The arrangement of non-return valves is said to prevent depressurisation of the hitch hydraulic means in case of leakage. Thus EP-A-0 184 282 requires a double-acting motor for moving the locking member between the lock and release positions as well as a reversing valve in addition to the non-return valves. This arrangement is so complex that it does not facilitate the installation of the coupling arrangement in existing machines. The invention claimed herein overcomes that disadvantage by simplifying the connection between the first and second hydraulic motors. An example of a machine according to this invention will now be described with reference to the accompanying drawings wherein: Fig 1 is an elevation of the machine. Fig 2 is an enlarged detail of Fig 1 and shows the coupling of the machine in the fully engaged condition. Fig 3 is a section on the line III-III in Fig 2. Fig 4 is a view on the line IV-IV in Fig 2. Fig 5 is a further enlarged detail of Fig 2 and shows a part of the coupling in a partly engaged condition. Figs 6,7 and 8 show different stages in process of engaging the coupling. Fig 9 is a diagram of a hydraulic system for operating the coupling and also shows an associated part of the machine. General Arrangement Referring to Fig 1 the excavating machine comprises a chassis 10, an operator cab 11 and a boom 12 pivotally connected at one end to the chassis 10 and supporting a pivoted arm 13 at its other end. The boom 12 and arm 13 lie in a common plane and can be operated, i.e. raised, lowered, extended or contracted within said plane and relative to the chassis 10 by linear hydraulic motors 14,15. At the free or rear end of the arm 13 there is provided a first member 16 of a coupling 18 for connecting a bucket 19 to the arm 13, a second member 17 of the coupling being provided on the bucket itself. The coupling member 16 has one end connected to the free end of the arm 13 by a front pivot 20 and another end connected in succession by a rear pivot 21, a link 22, a pivot 23 and a rod 24 to a hydraulic motor 25 comprising a piston 26 and a cylinder 27 mounted on the arm 13 by a pivot 28. The arrangement is such that operation of the motor 25 pivots the coupling member 16 about the pivot 20. The cab 11 includes an operating lever 28 for operating the motors 14,15 and an operating lever 29 for operating the motor 25. The drawing shows the bucket 19 as connected to the arm 13 by the coupling 18. The Coupling Referring to Figs 2 and 4, the coupling 18 is described with reference to mutually perpendicular directions X,Y,Z wherein the directions X and Z lie in the common plane of the boom and arm 12,13. The terms "front" and "rear" are used for aspects of the coupling respectively near to and remote from the cab 11. The terms "forward" and "rearwards" are used to indicate movement in directions respectively toward and away from the cab 11. The coupling member 16 comprises a pair of side plates 30 which contain the pivots 20,21 and which are secured to a base plate 31 which lies in the directions X,Y. The base plate 31 includes a front hook 32 and a rear hook 33 both secured to what is regarded as the underside of this plate. The hooks 32,33 are spaced apart in the direction X. The member 16 further includes an hydraulic motor 34 comprising a cylinder 35 and a piston 36 provided at the other or upper side of the plate 31. The motor 34 is positioned intermediate between the hooks 32,33 and so that the axis, 34Z, of the cylinder 35 lies in the direction Z. The piston 36 has secured thereto a circular cross-section pin 37 projecting in the direction of the axis 34Z through the plate 31 to the underside thereof and provided at its end remote from the piston 36 with a head 38 of larger diameter than the pin 37. The piston 36 is urged upwardly by Bellville springs 39 (Fig 2) so as to bias the head 38 towards the plate 31 into a retracted position. Introduction of hydraulic pressure into the cylinder 35 above the piston 37 urges the latter downwards in opposition to the force of the springs 39 so as to move the head 38 away from the plate 31 into an extended position. The coupling member 17 which, as mentioned, is secured to the bucket 19, comprises a plate 40 having a front aperture 41, a rear aperture 42, and an intermediate aperture or key hole slot 43, respectively dimensioned for the free passage through the plate 40 of the front hook 32, the rear hook 33 and the head 38. The key hole slot 43 comprises a part 44 wide enough for the passage therethrough of the head 44, and a part 45 whose width is such that it can accommodate the pin 37 but that it does not permit the passage of the head 44. The front hook 32 and adjacent parts of the plates 31, 40 are dimensioned to satisfy a specific manoeuvre of engaging the hook 32 with the plate 40 as a preliminary to passing the head 38 and rear hook 33 through the apertures 42,43. This manoeuvre, which is described later hereinbelow, is a particularly useful way of operating the coupling 18. To this end the front hook 32 (Fig 5) comprises a foot 46 connected at one end or heel 46A to the plate 31 by a stem 47 and provided at the other end or toe 46B with an end surface 48 extending between upper and lower edges 48A,48B which lie in the direction Y and which are spaced apart obliquely in the directions X and Z such that the upper edge 48A lies rearward of the edge 48B. An acute angle 48C between the surface 48 and the plate 31 is preferably about 45 degrees. The foot 46 is spaced from the plate 31 by a distance 46A which is slightly greater than the thickness of the plate 40. Further, the plate 31 has an abutment formed by a front edge 30A being an edge extending at the underside of this plate in the direction Y parallel to the edge 48B of the foot 48 and approximately in alignment with the edge 48B in the direction Z. The edge 30A is intended for support of the plate 31 on the plate 40 during operation. The aperture 41 of the plate 40 has a width 41X in the direction X less than the width, 46X, of the foot 46. Further, the aperture 41 has a front end surface 41A which defines, at the underside of the plate 40, an edge 41B extending in the direction Y and defining an abutment about which the surface 48 of the foot 46 can pivot in operation. The Coupling Manoeuvre Connecting the bucket to the machine is performed by a manoeuvre comprising the following steps: 1. Moving the machine relative to the bucket so that the coupling member 16 is situated above the coupling member 17 of the bucket as standing on the ground. This position is easily achieved by the operator operating the motors 14, 15. 2. Moving the head 38 into the extended position by operating the motor 34. This is more specifically described later hereinbelow with reference to the hydraulic system. 3. Operating the motor 25 to move the member 16 into a position in which the toe 46B of the hook 32 points toward the aperture 41 of the plate 40. 4. Operating the motors 14,15 to lower the member 16 so that the toe 46B enters into the aperture 41, this movement being terminated by the edge 30A abutting the plate 40 (Fig 6). 5. Operating the motor 25 to tilt the member 16 forwards thereby to engage the surface 48 of the hook 32 with the edge 41B of the aperture 41 (Figs 5,6). During this movement the hook 32 describes an arc 32A about the pivot 20. Since the bucket 19 rests on the ground, this arcuate movement of the hook may need to be accompanied by a corresponding raising of the arm by operation of the motors 14,15 to compensate for the downward component of the arcuate movement. Also, it will be noted that the forward component of the arcuate movement causes the bucket to slide along the ground in a forward sense. The resistance of the bucket to such sliding assists in the engagement of the hook 32 with the aperture 41. 6. Continue operation of the motor 25 thereby to fully pass the hook 32 through the aperture 41 (Fig 7). At this stage, the plate 31 lies fully on the plate 40 and the head 38 has passed through the large part 43 of the aperture 44. It will be clear from Figs 5 and 6 that the co-operation between the edge 30A and the plate 40, the co-operation between the surface 48 and the edge 41B, and the relative lengths of the distances 41X,46X, all ensure a smooth passage of the hook 32 through the aperture 41 and also ensure that the head 38 is aligned with the large part 43 of the aperture 44 as the plate 31 is lowered on the plate 40. 7. Continue operation of the motor 25 thereby to tilt the plate 31 obliquely forwards and upwards so that the bucket 19 is raised from the ground and tends to slide backwards under gravity, this movement being terminated by engagement between the stem 47 of the hook 32 and the surface 41A of the aperture 41 (Fig 8). In this position the rear hook 33 engages the rear aperture 42 and the rod 37 engages the narrow part 45 of the slot 43. 8. Retracting the head 38 by operation of the motor 34 thereby to clamp the plate 40 to the plate 31 and secure the bucket 19 to the member 16 by the springs 39. The hooks 32,33 now serves the purpose of preventing rotation of the bucket 19 about the axis of the rod 37. The operation of the motor 34 necessary for steps 2 and 8 of the above manoeuvre will now be described as part of the description of the hydraulic control system. The Hydraulic Control System Referring to Figs 1 and 9, hydraulic pressure is supplied by a pump 50 through a valve group 51 to the motors 14,15 in a manner known per se and therefore not illustrated. Regarding the motor 25, the pump supply is connected by a circuit 50A to a reversing valve 52 forming part of the group 51 and operable by the lever 29 for introducing the supply through lines 53,54 to the respective ends of the cylinder 27 for pivoting the coupling member 16 forwards or rearwards. The pump supply is connected through a pressure relief valve 53A to drain so that when the piston 26 reaches the end of its stroke the pressure in the supply line 53 or 54, as the case may be, rises to the relief pressure. The line 54 is also connected by a feed line 55 through a control valve 56 to the motor 34. The valve 56 comprises a valve member 57 containing a first non-return valve 59 arranged to permit flow only toward the motor 34 and a second non-return valve 62 arranged to permit flow only away from the motor 34. The valve 56 is operated by a solenoid 63 arranged in an electric circuit 64 controlled by a normally open switch 65 mounted on the lever 29 (Fig 1) for actuation by the operator when seated in the cab 11. The normal position of the valve 56, i.e. the position the member 57 has when the switch 65 is open, is such that a spring urges the member 57 into a position in which the motor 34 is connected to the line 55 through the non-return valve 62 so that the cylinder 35 can drain under the action of the springs 39 on the piston 36 and the head 38 is held in the retracted position. If the switch 65 is closed, the solenoid 63 moves the member 57 into a position in which the motor 34 is connected to the line 55 through the non-return valve 59 so that pressure in the line 55 can act on the motor 34 to extend the head 38. Referring to step 2 of the coupling manoeuvre, since the springs 39 have to be powerful enough to hold the bucket 19 firmly on the member 1, a correspondingly high hydraulic pressure is needed for compressing the springs 39 when the head 38 is to be extended. To this purpose use is made of the highest pressure available on the machine viz. the relief pressure of the valve 53A. More specifically, step 2 of the coupling manoeuvre comprises two actions. The one action comprises operating the lever 29 to tilt the member 16 forwards to the fullest extent permitted by the cylinder 27 as shown in Fig 9. On abutment of the piston 26 with the one end of the cylinder 27 the hydraulic pressure rises to the maximum permitted by the relief valve 53A. The other action comprises closing the switch 65 to connect this maximum pressure to the motor 34 to extend the head 38. As can be seen in Fig 1, the valve 56 is mounted on the arm 13 adjacent to the motor 25. By using the motor 25 for providing the pressure for the motor 34, there is avoided the need for providing an additional valve in the group 51 (Fig 1) and an additional high pressure line along the boom 12 and arm 13 to the member 16. This greatly facilitates the installation of the coupling 18 in existing machines. Regarding step 8 of the coupling manoeuvre, it will be clear that simply allowing the switch 65 to return to its normally open position connects the motor 34 to the line 55 through the non-return valve 62. If the pressure in the line 55 should rise to maximum during ordinary operation of the machine, then the valve 62 prevents accidental operation of the motor 34. In this way there is provided a fail-safe retention of the bucket 19 on the member 16. When the bucket 19 is to be disengaged from the member 16, the motor 25 is operated to move the member 16 into a position wherein the plates 30,40 are inclined obliquely rearward and upward. Thereafter the switch 65 is closed with the consequence that the head 38 is extended and the bucket is freed to slide forward and downward and pivot about the hook 32 into a position free of the member 16.

Claims: An earth-working machine comprising: a support structure (10), a tool support (13) provided on the support structure (10) and movable relative thereto, a first coupling member (16) provided on the tool support and movable relative thereto, a tool (19), a second coupling member (17) provided on the tool (19) and adapted for engagement by and disengagement from the first coupling member (16), first operating means (28,29) provided on the support structure (10) for effecting movement of the first coupling member for said engagement and disengagement, a locking member (38) provided on the first coupling member (16) and being moveable between lock and release positions for locking the second coupling member (17) in the engaged condition or releasing it therefrom, a spring (39) for urging the locking member (38) into one of the lock and release positions, and second operating means (56) for effecting movement of the locking member (38) into the other of the lock and release positions, characterized in that the second operating means (56) comprise : electro-magnetic means (63) mounted on the tool support (13) and adapted for effecting movement of the locking member (38) in opposition to the force of the spring (39), and an electric switch (65) provided on the support structure (10) and adapted (64) for the electric operation of the electro-magnetic means (63). A machine according to claim 1 comprising: a first hydraulic motor (34) for moving the locking member (38) in opposition to the force of the spring (39), a second hydraulic motor (25) for moving the first coupling member (16) between operational positions, a hydraulic circuit (50A) for operating the second hydraulic motor (25), a single hydraulic flow line (55) connected between the first hydraulic motor (34) and the circuit (50A), a first non-return valve (59) connectable in the flow line (55) so as to permit flow only in the direction toward the first hydraulic motor (34) thereby to move the locking member (38) in opposition to the force of the spring (39), a second non-return valve (57) connectable in the flow line (55) so as to permit flow only in the direction away from the first hydraulic motor (34) thereby to permit movement of the locking member (38) under the force of the spring (39), and operating means (63) for connecting either the first (59) or the second non-return valve (57) in the flow line (55). A machine according to claim 1 or claim 2 comprising an operating lever (29) provided on the support structure (10) and connected for moving the first coupling member (16) relative to the support structure (10), and wherein said electric switch (65) is mounted on the lever (29).

Inventors: AUBREY MARTIN JAMES, AUBREY, MARTIN JAMES
Applicants: SWIFT HITCH LTD, SWIFT HITCH LIMITED
Application year: 1991
Main classification: E02F3
IPC codes: E02F3