Arrangement for securing an implement to a lifting arm

The invention concerns an arrangement for the securing of an implement to a lifting arm, particularly to a front loader, where the implement and the lifting arm can be fastened to each other by a movable locking bar, which can be moved between a locking position and an unlocking position, and can be brought from the locking position into the unlocking position by a remotely actuated hydraulic cylinder. It is proposed that the locking bar can be arrested automatically in the unlocking position, with it then being possible for the hydraulic cylinder to be deactivated. The locking bar is located such that it can be brought into the locking position from its arrested position by moving the implement by another remotely actuated hydraulic cylinder such that the locking bar engages the lifting arm and is moved to a non-arrested position from where it is automatically biased back into its locking position. Furthermore, it is proposed that the hydraulic actuator for effecting movement of the locking bar be connected with an accumulator.

FIELD OF THE INVENTION

The invention concerns an arrangement for securing an implement to a boom or lifting arm, particularly a front loader, where the implement and the lifting arm can be fastened to each other by a movable locking bar that can be moved between a locking position and an unlocking position and can be brought from the locking position into the unlocking position by a motor actuated by external force.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 5,466,113 describes an arrangement for securing an implement to a lifting arm, that includes a locking bar that can be moved manually between a locking position, in which it retains the implement at the lifting arm, and an unlocking position, in which it releases the implement. In the unlocking position, the locking bar can be arrested by pivoting it in a first direction between initial and arresting positions about a locking axis. After the attachment of an implement, it is brought into the locking position automatically by pivoting the implement under hydraulic power towards the lifting boom until the locking bar is engaged by the lifting boom and pivoted back to its initial position. However, due to the manual operation of the locking bar, the operator must move to the implement in order to unlock the locking bar. In this publication, a motorized movement of the locking bar into the unlocking position is also proposed. However, it is not disclosed how the locking bar is retained or arrested in the unlocking position in such a configuration, nor how it is to be brought back into the locking position.

Another known lifting arm arrangement is disclosed in FR 2 776 316 A. In this patent, a locking bar is moved by a hydraulic motor in order to secure an implement. To unlock the implement, a key or switch push button is actuated on a handgrip in the region of the operator's station, so that the hydraulic motor is supplied with fluid and brings the locking bar into the unlocking position. Indeed, in order to lock an implement, a further actuation of a key is necessary in order to end the supply of fluid to the hydraulic motor and to bring the locking bar into the locking position. Hence, this solution is also not operator friendly.

The problem underlying the invention is seen in the need to provide an ergonomically favorable arrangement for securing an implement on a lifting arm in which the aforementioned disadvantages have been eliminated.

SUMMARY OF THE INVENTION

According to the present invention, there is provided an improved arrangement for securing an implement on a lifting arm.

An object of the invention is to provide a locking bar arrangement which can be remotely released and then automatically moved to an arrested position.

It is proposed that the locking bar be brought from the locking position into the unlocking position by a motor actuated by external force in order to be able to remove the implement from the lifting arm. The locking bar is arrested in the unlocking position automatically, that is, without any manual effort by the operator, and the motor again deactivated, so that it does not oppose a return movement of the locking bar into the locking position. After the attachment of an implement (another or the same implement) the locking bar is again brought into the locking position by a movement of the implement relative to the lifting arm, particularly a pivoting movement.

In this way, the operator need perform only one unlocking of the implement in order to be able to remove it from the lifting arm. After the attachment of the implement, it is again secured without the need for the operator to perform a locking by depressing a key or the like.

The implement can be secured to the lifting arm in a manner known in itself by pivoting it relative to the lifting arm by means of a hydraulic cylinder. Here the locking bar interacts with the lifting arm and reaches the locking position automatically.

Although it would be conceivable to use an electric or pneumatic motor as an externally powered motor, the use of a hydraulic motor is preferred, in particular a hydraulic cylinder. Regardless of its type, the motor is appropriately controlled by a valve that can be remotely actuated from the operating position of the operator.

Lifting arm arrangements, in particular front end loaders, are attached, as a rule, to agricultural tractors so as to be removable and are connected through a series of lines with the on-board hydraulic system of the agricultural tractor. As a rule, the valves for the control of the hydraulic cylinders of the lifting arm are located on the agricultural tractor. Therefore, only a limited number of lines are available, which furthermore carry hydraulic pressure only when one of the hydraulic cylinders of the lifting arm is actuated. Independent of this fact, there is a need for pressurized hydraulic fluid for the activation of the motor actuated by external force in order to be able to bring the locking bar into the unlocking position at any desired time. According to a second viewpoint of the invention, therefore, an accumulator is provided for the supply of the externally powered motor. Thereby, one or more of the lines leading to the agricultural tractor is supplied with pressure and makes available a pressure sufficient to unlock the locking bar at any time and independent of the immediate position of the lifting arm.

The accumulator is preferably filled when it is separated from the externally powered motor. Then it is connected with the hydraulic cylinder used to move the implement. When the hydraulic cylinder is supplied with pressure and moves the implement in the direction leading to the locking, so that the locking bar reaches the locking position from the unlocking position, the accumulator is also filled. Thereby, sufficient pressure is available in order to unlock the implement again later. Alternatively or in addition, the accumulator can also be connected with another chamber of the aforementioned hydraulic cylinder or any other desired hydraulic cylinder, in order to fill it.

The externally powered motor must be brought into its rest position before an implement can be retained in a detent. Therefore, an obvious solution is to connect it with a chamber of the hydraulic cylinder which then carries no pressure-particularly over an overflow valve—when the hydraulic cylinder moves the latter in order to move the implement in the direction leading to the locking. Without remotely controlled valves and automatically thereby one after the other, the remotely powered motor will be brought into its rest position and then the locking bar retained in a detent.

Most appropriately, the locking bar is preloaded by a spring into its locking position. Thereby, an externally powered double acting motor can be eliminated that would be necessary to move the locking bar and a corresponding circuit configuration.

A lengthwise slot can be used for arresting the locking bar in the unlocking position, as it is known from DE 43 27 942 C. The lengthwise slot has a section of narrower slot width and a section of wider slot width. The locking bar can be moved relative to the lengthwise slot. A stop of the locking bar has a dimension that is greater than the narrower slot width, but is smaller than the wider slot width. If the locking bar is drawn transverse to the direction of the lengthwise slot out of the locking position into the unlocking position, then the stop moves out of the lengthwise slot and is moved along beside the lengthwise slot, by the force of a second spring. In particular, the stop is rotated. After the externally powered motor is deactivated, the stop comes into contact with the section of the lengthwise slot with the smaller dimensions; there it is arrested in the unlocking position. After the reattachment of an implement, it is conditioned by the movement of the lifting gear, at which time the locking bar makes contact with another element, and is again brought to the section of the lengthwise slot with wider slot width. There, the locking bar is moved by the spring into the detent position.

A second spring, that brings the locking bar into a position in the unlocking position in which it is arrested, can also be applied to any other desired arrangement for the arresting of the locking bar. In place of a spring, a weight or a further motor actuated by external force can be used to arrest the locking bar in the unlocking position.

There are ranges of lifting height in which an activation of the externally powered motor for the unlocking of the locking bar is not useful. In such regions of lifting height, a corresponding input from the operator is appropriately ignored in order to reduce the danger of accidents. In a preferred embodiment, in a range of positions of the lifting arm, in which the input for the releasing of the implement is ignored, can be defined by the operator. For this purpose, numerical inputs can be provided, or the lifting arm is brought into a position that is then stored in memory following a corresponding input. Several such regions may also be defined. A sensor detects the position of the lifting arm and a control arrangement comprising the sensor, the push-button switch, and the valve, which is connected to the sensor for the control of the motor and activates the valve only in the regions of position of the lifting arm that are permitted.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A lifting arm or device10shown inFIG. 1is attached to the front side of an agricultural tractor that is only fragmentarily indicated. The lifting arm or device10includes a mast12that is shown and that engages in a bearing14a lifting boom16that is reinforced due to its double-armed configuration by means of a transverse tube18. An implement20, here shown as a bucket, but which may be, for example, an earth scoop, a manure fork, a bale fork or a pallet fork, is connected so as to be movable and easily replaced, to the front end of the lifting boom16by means of a positioning arrangement30, described below, and an implement holder32. In order to raise the implement20, the lifting boom16is pivoted about the bearing14by hydraulic motors26. In order to reposition the inclination of the implement20, a further hydraulic motor28engages with one end the repositioning arrangement30and with its other end the lifting boom16. The repositioning arrangement30acts upon the implement holder32, to which the implement20is connected directly, and is composed generally of first and second pivot arms34and36, respectively, that are connected to each other in a joint, where the hydraulic motor28engages the joint44. The implement holder32is supported in bearings38and the first pivot arm34is supported in bearings40on the lifting boom16, free to pivot. The second pivot arm36is connected to the implement holder32, free to pivot, in a bearing46. The number call-out48identifies a locking bar that is explained in greater detail below. In the upper section of the implement holder32, a hook50and a pin52are provided that bring the implement20into engagement with the lifting arm or device10.

According toFIG. 2, the implement holder32is composed on its underside by a transverse bar54extending over the entire width, and by walls56, in each case arranged in pairs, that are penetrated by the end sections of the transverse bar54and are welded to it.

Two brackets58project radially and parallel to each other from the side of the transverse bar54facing the implement20and contain openings60that are aligned with each other. The openings60are used to engage pin-shaped locking segments or parts64formed by respective end regions of the locking bar48, by means of which the implement20is fastened to the implement holder32and with it to the lifting arm or device10. On the side facing the implement holder32, the implement20is also provided with brackets with such openings, although not shown, that can be brought into alignment with each other and through which the locking segments64of the locking bar48can be inserted.

The double walls56on each side of the holder32carry in their upper corner region the pins52that engage the hooks50. Below and offset to the rear from the pins52are the bearings46, and in the right lower end region of the holder32are the bearings38for the connection to the lifting boom16(seeFIG. 3). Beyond that, in each of the walls56, located at the left inFIG. 2, are two lengthwise slots66machined in transverse alignment with each other and whose centerline is located on a circular arc about the center of the openings60. The lengthwise slot66, of the inward or right one of the left pair of walls56inFIG. 2, is provided with an approximately constant slot width over its length. The lengthwise slot66, of the outward or left one of the left pair of walls56inFIG. 2, is provided in a lower section with a narrow slot width and in an upper section with a wider slot width.

The locking bar48is manufactured from steel rod and has the general shape of a “J”, with a first, long leg68, a second, short leg70, and a handgrip72that bridges a gap between these two legs.

Between the handgrip72and the end region defining a right locking part64, the first, long leg68is bent at two places in opposite directions through approximately 30° and is constantly guided with the locking part64in the opening60of the inner bracket58on the right side. The section of the long leg68, located opposite the locking part64and offset radially from it, extends through both lengthwise slots66and carries a stop76formed as a sleeve that extends only halfway to the left and the right of the outer wall56in the locking position of the locking bar48, as shown inFIG. 2. The length of the section of the stop76that extends into the space between the two walls56corresponds generally to the repositioning path of the locking bar48for the locking or unlocking of the implement20. The outside diameter of this stop76is smaller than the wider slot width, but is larger then the narrower slot width of the outer lengthwise slot66. Inside, or to the right of the inner left wall as seen inFIG. 2, the long leg68is surrounded concentrically by a spring78, which is in contact under a preload on the one hand with a disk80fastened to the long leg68and at its other end with a disk82that is in sliding contact with the wall56, where the diameter of the disk82is larger than the width of the lengthwise slot66in its widest section.

The handgrip72is perpendicular to, and has opposite ends respectively joined to, the long and short legs68and70of the bar48and is located outside the outer, left wall56so as to be easily accessible to an operator.

The short leg70extends parallel to the long leg68in its region up to the bend forming the junction between the handgrip and short leg70, and extends through the openings60of the left side and corresponding aligned bores74in the left walls56. Guides in the form of sleeves may be fixed to the walls56in surrounding relationship to the short leg70if necessary or desired. The short leg70is also provided with an end section that includes a locking segment64which is constantly guided in the opening60of each left bracket58.

The spring78is configured as a helical compression spring and assembled and loaded in such a way that it constantly forces the locking bar48to the right, as viewed inFIG. 2, so that the locking segments64extend through all brackets58.

In addition, a remotely operable hydraulic motor90, here shown in the form of a single-acting hydraulic cylinder, is provided with its cylinder extending in the longitudinal direction of, and being fastened to, the transverse bar54. The piston of the hydraulic motor90is connected with a sleeve92that encloses the long leg68of the locking bar48in the vicinity to the left of the right pair of brackets58, shown inFIG. 2. The sleeve92is arranged near a right surface of a disk94that is rigidly connected to the long leg68. The piston of the hydraulic motor90is arranged to shift the sleeve92to the left from the rest position, shown inFIG. 2. In this way, there is a possibility of bringing the locking bar48under remote control into an unlocking position. A further spring96is arranged between the rod end of the cylinder and the piston of the hydraulic motor90, which biases or preloads the piston in the direction of the head end of the cylinder; that is, it endeavors to shift the piston rod, and hence, the sleeve92to the right, as viewed inFIG. 2.

As seen inFIG. 2, it is clear that the locking bar48can be grasped manually at the handgrip72and shifted to the left against the force of the spring78, so that both locking segments64can be drawn out of each of the right brackets58of each pair of brackets58so as to free the space between both brackets58of each pair of brackets58for taking up or freeing the associated bracket on the back side of the implement20, and thereby unlocking or freeing the implement20from the implement holder32. During this manual operation, the sleeve92slides on the long leg68of the locking bar48, and the piston of the hydraulic motor90remains stationary.

InFIG. 3, the outer left wall56of the implement holder32has been removed for the sake of clarity. As can be seen inFIG. 3, a second spring84interacts with the locking bar48. Specifically, the spring84has one end fastened to the inner left wall56and its other end fastened to a rocker or lever86that is pivotally attached to the inner wall56so as to pivot freely about an axis of rotation extending parallel to the transverse bar54. The long leg68of the locking bar48penetrates an opening88in the rocker86. In this way, the spring84draws the long leg68downward or clockwise, as viewed inFIG. 3, as soon as the stop76has been drawn out of the lengthwise slot66, so that the long leg68reaches the narrower-width region of the lengthwise slot66. The stop76thus abuts the outer left wall56and arrests the locking bar48from moving from its unlocking position. Accordingly, the arrested locking bar48may be released during manual actuation.

If the implement holder32is to be prepared to take up an implement20, the locking bar48can also be drawn manually outward into the unlocking position, as described above, where it is drawn by the second spring84in a clockwise direction about the axis extending through the opening60, as seen inFIG. 3, so that the stop76is moved on the outside of the left outer wall56into the region of the narrower slot width of the lengthwise slot66.

Thereby, the spring78is further compressed or loaded and the locking bar48is retained in the unlocked position. Following this, the implement20can be taken up and raised by the pin or pins52and the hook or hooks50, so that each bracket on the back side of the implement20respectively reaches between one of the pair of brackets58on the transverse bar54and all openings60are aligned with each other. Finally the implement20is tilted towards the lifting boom16by actuation of the hydraulic motor28so that the stop76is brought into contact with the lifting boom16, and together with the long leg68, is pivoted into the region of the wider slot width of the elongate slot66. Once it has reached that point, the stop76enters the slot66with the loaded spring78, then acting to shift the entire locking bar48to the right, as seen inFIG. 2, so as to once again cause the two locking segments64to penetrate all brackets and secure the implement20to the holder32.

On the other hand, for the unlocking or freeing of the implement20, the hydraulic motor90can also be activated from the operator's station on the agricultural tractor so that its piston brings the sleeve92into contact with the disk94and shifts the disk94, together with the entire locking bar48, to the left. The locking segments64free the brackets of the implement20. Since the stroke of the piston of the hydraulic motor90is sufficiently large to extract the stop76from the lengthwise slot66of the outer wall56, this frees the locking bar48to be rotated by the action of the second spring84so as to place the inner end of the stop76in alignment with the narrow part of the elongate slot66, thereby arresting the locking bar in its unlocking position. At first, the hydraulic motor90remains supplied with pressurized fluid. Following this, the implement20can be separated from the implement holder32by resting the implement20on the ground and rotating the holder32so as to disengage the pins52from the hooks50by actuation of the further hydraulic cylinder28. Once the implement20is detached, the cylinder28may be actuated to once again bring the long leg68of the locking bar48into contact with the boom16so as to cause the bar to rotate and dispose the stop76in alignment with the wide part of the elongate slot66. The hydraulic motor90then is returned to its rest position by the action of the springs78and96. It would also be conceivable to omit the spring96and to bring the hydraulic motor90into its rest position just by the action of the spring78.

In another embodiment, the stroke of the hydraulic motor90can be selected in such a way that it is not adequate to extract the stop76from the lengthwise slot66of the outer wall. The hydraulic motor90remains in this position or is moved again into the rest position in order to expose the piston of the hydraulic motor only for a short time to the environmental influences. Therefore, in this embodiment the locking bar48is not arrested in the unlocking position. However, if a new implement is to be attached, the hydraulic motor90can extract the stop76out of the lengthwise slot66of the outer wall56later, for example, before or during the tilting movement of the implement20for the locking, so that the locking bar48is retained in a detent in the unlocking position. It would also be conceivable to extend the hydraulic motor90only so far that it permits the attachment of the implement, but does not permit it to be locked in place. Subsequently,the implement is locked in place by disconnecting fluid pressure from the hydraulic motor90such that the springs78and96shift the locking bar48to its locking position and the hydraulic motor90to its rest position.

The coupling arrangement composed of the sleeve92and the disk94between the motor90and the locking bar48,makes it possible to actuate the locking bar48by the motor90and independent thereof manually. The spring78permits the use of the coupling arrangement on a single-acting hydraulic cylinder as a hydraulic motor90.

FIG. 4shows a hydraulic circuit diagram on the basis of which the control of the hydraulic motor90shall be explained below. The further hydraulic cylinder28, used to reposition the inclination of the implement20, is a double-acting cylinder whose piston chamber100and piston rod chamber102can be connected by appropriate lines, not shown, with the operating hydraulic system of the agricultural tractor. The valves for the control of the hydraulic cylinder28as well as a valve for the control of the single-acting hydraulic cylinder26are located on the agricultural tractor. Hence, three removable hydraulic lines lead to the lifting arm or device10. The elements shown inFIG. 4are all arranged on the lifting arm or device10. Furthermore, a removable electric connection is provided between the agricultural tractor and the lifting arm or device10for the control of a solenoid or electro-magnetically controlled switching valve106.

When the piston rod chamber102is supplied with pressurized fluid, the implement20, together with the implement holder32, rotate in the clockwise direction about the bearing38, as seen inFIG. 1(to the rear against the direction of operation of the agricultural tractor). If the piston chamber100is supplied with pressurized fluid, the implement rotates analogously to the front for unloading. In each case, whichever of the chambers100and102that is not supplied with pressurized fluid is connected by the valves provided on the agricultural tractor with a tank to contain the excess hydraulic fluid.

The piston rod chamber102is connected, over a check valve104and an electro-magnetically controlled switching valve106, with an accumulator108. If the switching valve106is in the rest position shown inFIG. 4, hydraulic fluid flows over the check valve104into the accumulator108, as soon as the pressure in the piston rod chamber102is higher, by a certain pressure difference than the pressure existing in the accumulator108. Upon the pivoting of the implement20to the rear, which leads to the locking bar48being pivoted from its unlocked arrested position from where it is biased into the locking position, the piston of the hydraulic actuator28bottoms out and the pressurized fluid goes to fill the accumulator108. It would also be conceivable to connect the accumulator108over a further check valve with the piston chamber100of the further hydraulic cylinder28.

The piston chamber of the hydraulic motor90is connected, in the rest position of the switching valve106, over a check valve116with the piston chamber100of the hydraulic cylinder28and thereby with the tank. Thereby, the hydraulic motor90is not supplied with pressurized fluid so that it moves to the rest position, shown inFIG. 2, when the piston chamber100is not under pressure, which is the case when the implement20is tilted towards the lifting boom16so as to release the bar48for locking the implement to the holder32. If subsequently, the pressure in the piston chamber100again rises, then the check valve116prevents a pressure increase in the piston chamber of the hydraulic motor90.

By means of a push-button switch112, that is attached to a handgrip114of a control handle that is located at the operator's platform on the agricultural tractor for the control of the hydraulic cylinders26and28, an electric current may be coupled over an electrical control unit118for actuating the switching valve106for movement into its operating position in which the accumulator108is connected with the piston chamber of the hydraulic motor90. Thereby, the hydraulic motor90is extended and the locking bar48is moved into its unlocking position, from where it is rotated by the second spring84into its position where it is arrested by the stop76. Then the electrical control unit118automatically acts to terminate the flow of current to the switching valve106whereupon the valve106returns again into the rest position, so that the hydraulic motor90is connected over the switching valve106and the check valve116with the piston chamber100. The hydraulic motor90remains supplied with pressurized fluid until the pressure in the piston chamber100drops off. Furthermore, the accumulator108is connected over a relief valve110with the piston rod chamber102, whose purpose consists of draining excess hydraulic fluid from the accumulator108into the tank when the switching valve106is in its operating position, and hence the accumulator108is connected only with the hydraulic motor90. It could also be possible to omit the relief valve110.

Furthermore, the electrical control unit118is connected with a height sensor120that is attached to the mast12and that detects the pivot angle of the lifting boom16about the bearing14(seeFIG. 1). The height sensor120may be, for example, a potentiometer or an incremental angle transmitter which generates a signal relating to the relative angular disposition of the lifting boom16to the mast12and transmits this signal to the control unit118. Angular regions are stored in memory in the electrical control unit118, in which an actuation of the push-button switch112is ignored. Thereby, an activation of the hydraulic motor90can be prevented at inappropriate positions of the lifting boom16, for example, if it is raised very far. The angular regions, in which the push-button switch112is ignored, can be permanently programmed or provided as input by the operator, particularly in the form of numerical values or in the form of inputs of push-button actuation or the like when the lifting boom16is in a position in which a corresponding angular region begins or ends.

A further latch position sensor122(seeFIG. 2) interacts with the locking part64and detects whether it is in its locking position. In case the hydraulic motor90is not supplied with pressurized fluid, but the piston100of the further hydraulic cylinder28has been supplied with pressurized fluid and the locking part64should therefore be in its locking position, but the latch position sensor122does not detect it, the operator is supplied with a corresponding acoustic or visual warning signal, here shown as a light123. The latch position sensor122can be in the form of a mechanical or magnetic switch or a light barrier to detect the locking part64. The sensors120and122and the application of their signals must be accorded independent inventive significance.

Thereby, the switching arrangement of the hydraulic motor90makes it possible to activate the hydraulic motor90and to bring the locking bar48into its unlocking position and to arrest it there. Following this, the implement20can be deposited on the ground or any other desired deposit surface and subsequently another or the same implement20can be taken up and raised. Following this, the implement20can be tilted relative to the lifting boom16by means of the hydraulic motor28, so that the hydraulic motor90is no longer supplied with pressurized fluid and is brought by the spring96into its rest position as shown inFIG. 2. Shortly thereafter, the stop76comes into contact with the lifting boom16and is pivoted into the region of the wider slot width. Once it reaches there, the spring78brings the locking bar48into the locking position. Simultaneously, the accumulator108is again filled. Accordingly, the securing of the implement20does not require the activation of any hydraulic device any more, making unnecessary the actuation of a key or switch push button.