GB2242886A - Backhoe - Google Patents

Abstract

A backhoe comprises a swivel deck, a driver's section mounted on the swivel deck, and a boom assembly provided in a region laterally of the driver's section. The boom assembly includes a boom connected to the swivel deck, a horizontal offset mechanism connected to the boom, a bucket arm connected to the offset mechanism, and a bucket connected to a forward end of the bucket arm. The boom assembly is switch able between a folded position contained within a swivel deck region and an unfolded, working position extending from the swivel deck region. A posture of the boom assembly is detected by means of a plurality of angle sensors, and is stored in a memory upon change from the working position to the folded position. The stored posture data is used for reinstating at least one component of the boom assembly in a previous position upon return from the folded position to the working position. Preferably, an offset sensor signal is stored when changing from working to folding modes and used to reinstate the offset mechanism in its previous position upon return for the folding to the working mode. <IMAGE>

Description

BACKHOE The present invention relates to a backhoe as described in the

preamble of claim 1.

With this type of backhoe, typically, earth dug forwardly of the backhoe may be transported to the bed of a truck standing rearwardly of the backhoe, for example, by freely turning the swivel deck. The turning movement is possible as long as a space is secured therefor, with the boom assembly folded to a position contained substantially within a region of the swivel deck. In carrying out this operation in a narrow space, it is necessary to repeat a control for unfolding the boom assembly to a position projecting from the swivel deck region, and a control for folding the boom assembly to the position contained within the swivel deck region. With the conventional backhoe, the series of control operations are inefficient, involving manual switching of valves to control a boom cylinder, a bucket cylinder, an arm cylinder and an offset cylinder acting as devices for driving the boom assembly.

An object of the present invention is to provide a backhoe of the type described above, which allows the boom assembly to be moved between the contained position and working position accurately and efficiently.

a 1 The above object is fulfilled, according to the present invention, by a backhoe of the type described above and having the features set out in the characterizing portion of claim 1.

With this construction, when a change is made from the working mode, e.g. an operation to break and scoop earth, to the folding mode, a current offset position data of at least one component of the boom assembly, e.g. the offset mechanism, obtained through the posture detecting means is stored in the storage. Then, the folding mode becomes operative to fold and horizontally swing the boom assembly. The boom assembly is unfolded again to unload contents of the bucket. Thereafter, the boom assembly is folded again and swung toward the digging site. To return to the previous working mode, the boom assembly is reinstated in the previous positional relationship on the basis of the position data stored in the storage.

Consequently, the operability of the boom assembly is improved remarkably in an operation repeatedly using the folding mode.

In a preferred embodiment of the present invention, the storage has a capacity for storing a plurality of data, i.e. position data for a plurality of postures. One of the position data may be selected for reinstating a desired posture upon return from the 1 folding mode to the working mode. To avoid complication of the system, only the position data of the most significant component of the boom assembly may be stored. In the case of a backhoe having the bucket arm, and hence the bucket, capable of being offset transversely of the boom to enhance freedom of bucket operating positions, the offset mechanism usually has different amounts of offset for operating the bucket and for containing the bucket embodiment of the invention, therefore, In one an offset sensor is provided for detecting the amount of offset.

The offset amount is stored when changing from the working mode to the folding mode, and is read when returning to the working mode, thereby automatically reinstating the offset mechanism in a previous offset position. Such an automatic return to the offset position alone will greatly facilitate repeated operations of loading, swivelling, unloading and swivelling.

Further, it is possible to control the boom assembly in a way to maintain an opening plane of the bucket substantially level during a transition from the working mode to the folding mode. This feature will provide a convenience of the bucket holding earth without spilling it.

In order that the present invention may be more t fully understood, an embodiment will hereinafter with reference to the drawings.

be described In the drawings:- Fig. 1 is a side view of the backhoe, Fig. 2 is a plan view of a boom assembly, Fig. 3 is a side view showing the boom assembly in a contained position, Fig. 4 is a plan view showing the boom assembly in the contained position, Fig. 5 is a block diagram of a control system for the backhoe, Figs. 6 to operations, and Figs. 14A and 14B are schematic views showing a definition of danger zones.

The backhoe shown in Fig. 1 comprises acrawler track frame 2 having a bulldozer blade 1, and a swivel deck 4 rotatably mounted on the track frame 2. The swivel deck 4 carries a driver's section 3, an engine E and a boom assembly 5.

The boom assembly 5 includes a boom 6 forming a basic component thereof. The boom 6 has an end pivotally supported at a position of the swivel deck 4 laterally of. the driver's section 3, and is vertically swingable by a boom cylinder Cl. As shown in Fig. 2, the. boom 6 includes a proximal member 6a acting as a 13 are flowcharts of control a main stay, a distal member 6b and an offset mechanism. The offset mechanism includes an intermediate member 6c connecting the distal member 6b to the proximal member 6a to be swingable about a vertical axis. More particularly, a link 7 extends parallel to the intermediate member 6c between the proximal member 6a and distal member 6b, and is pivotally connected to link attaching arms 7a and 7b supported by the proximal member 6a and distal member 6b, respectively.

The link attaching arms 7a and 7b, link 7 and intermediate member 6c constitute a parallelogram link offset mechanism. With this construction, an offset cylinder C4 causes the distal boom member 6b to make a substantially parallel movement in a transverse direction relative to the proximal boom member 6a. As a result, a bucket arm 8 connected to the distal boom member 6b makes a parallel movement, i. e. becomes offset, transversely of the proximal boom member 6a. The bucket arm 8 is vertically swingable relative to the proximal boom member 6a by an arm cylinder C2. The bucket arm 8 carries a bucket 9 attached to a distal end thereof to be vertically swingable by a bucket cylinder C3.

With this construction, the bucket arm 6 or bucket 9 may be offset laterally of the vehicle to engage in a groove digging operation along an outer 9 lateral edge of the track frame 2. The entire boom assembly 5 may be contained within a turning locus of the swivel deck 4 by outwardly offsetting the bucket arm 8, raising the boom 6, and folding the arm 8 and bucket 9. In this state, as shown in Fig. 3 and as schematically shown in Fig. 4, the boom 6, arm 8 and bucket 9 are retracted towards the swivel deck 4, with the bucket 9 lying laterally of the boom 6 opposite the driver's section 3. This state allows a turning movement in a narrow space, and is called herein a small turn containment state.

The boom assembly 5 and swivel deck 4 are controllable by a control device 10 provided in the driver's section. The control device 10 includes a pair of right and left control levers 10a and 10b rockable crosswise, i.e. back and forth and sideways, and an offset lever 10c.

Fig. 5 shows a block diagram of a control system for the backhoe according to the present invention.

As seen, the control system includes a first sensor S1 and a third sensor S3 which are potentiometers for detecting control positions of one of the control levers 10a longitudinally and transversely of the swivel deck 4, and a second sensor S2 and a fifth S5 which are potentiometers for detecting positions of the other control lever 10b sensor control it longitudinally and transversely of the swivel deck 4. Control states of the offset lever 10c is detected by a fourth sensor S4. Detection signals from these sensors are input to a control unit 11 formed essentially of a microcomputer.

The control system further includes a boom valve V1 connected to the boom cylinder Cl, an arm valve V2 connected to the arm cylinder C2, a bucket valve V3 connected to the bucket cylinder C3, an offset valve V4 connected to the offset cylinder C4, and a swivel valve V5 connected to a swivel motor M, each of these valves being an electromagnetic proportional c.ontrol valve. The control unit 11 controls valve drive circuits D1-D5 connected to the boom valve V1, arm valve V2, bucket valve V3, offset valve V4 and swivel valve V5, respectively. When the control lever 10a is manually operated longitudinally of the swivel deck 4, for example, the control unit 11 outputs a signal to the valve drive circuit D1 based on a detection result provided by the first sensor S1 and various control modes, thereby operating the boom valve V1. As a result, the boom cylinder Cl is operated, basically, in a direction and at a speed corresponding to a control position of the control lever 10a. Similarly, when the control lever 10a is manually operated sideways, the control unit 11 outputs a signal to the 1 valve drive circuit D3 based on a detection result provided by the third sensor S3 and various control modes, thereby operating the bucket valve V3. As a result, the bucket cylinder C3 is operated, basically, in a direction and at a speed corresponding to a control position of the control lever 10a. When the control lever 10b is manually operated longitudinally of the swivel deck 4, the control unit 11 outputs a signal to the valve drive circuit D2 based on a detection result provided by the second sensor S2 and various control modes, thereby operating V1. As a result, the arm cylinder C2 the arm valve is operated, basically, in a direction and at a speed corresponding to a control position of the control lever 10b. When the control lever 10b is manually operated sideways. the control unit 11 outputs a signal to the valve drive circuit D5 based on a detection result provided by the fifth sensor S5 and various control modes, thereby operating the swivel valve V5. As a result, the swivel motor M is operated in a direction and at a speed corresponding to a control position of the control lever 10b. An operation of the offset lever 10c is input to the control unit 11 in a similar way, and the control unit 11, in response to the input signal, switches the offset valve V4 through the valve control circuit D4 to operate the offset cylinder C4 -B- 1 in a desired manner. As will be described in detail later, the control unit 11 checks whether or not actions of the cylinders based on the operations of the various levers are desirable from the safety and functional points of view, for example. Undesirable control commands are cancelled or altered.

Fig 1 shows various sensors provided to input the posture of the boom assembly 5, i.e. positions of the members constituting the boom assembly 5, to the control unit 11. Specifically, a boom angle sensor P1 is mounted at a proximal end of the boom cylinder Cl for detecting a swing angle of the boom 6 with respect to the swivel deck 4. An arm angle sensor P2 is mounted at a distal end of the boom 6 for detecting a swing angle of the bucket arm 8 with respect to the boom 6. A bucket angle sensor P3 is mounted on a link 12 operatively connecting the bucket cylinder C3 to the bucket 9 for detecting a swing angle of the bucket 9 with respect to the arm 8, a swing angle of the link 12 with respect to the arm 8 being detected as a bucket angle. Further, an offset sensor P4 is mounted on the boom 6 for detecting a swing angle of the intermediate boom member 6c with respect to the proximal boom member 6a in order to obtain an offset amount including a direction of offset of the bucket 9 with respect to the proximal boom member 6a. These -g- A sensors preferably comprise rotary type potentiometers. As shown in Fig. 5, outputs of the sensors Pl-P4 are input to the control unit 11. As a result, the control unit 11 recognizes the posture of the boom assembly 5.

The control system further includes a danger avert mode switch S9, a fold mode switch S6, an offset return switch S7 and a levelling mode switch S8 acting as control mode switches for operation of the boom assembly 5 which are all connected to the control unit 11. As will be described in detail later, the danger avert mode is intended to avert such dangers as the bucket making an abnormal approach to the driver's automatically working deck 4 hereinbefore section 3 as a result of flexion or offset control of the boom assembly 5. The danger avert mode normally is turned on. The fold mode is intended to return the boom assembly position extending forwardly of the swivel to the small turn containment state noted The offset return means automatic reinstatement, which is effected when returning the boom assembly 5 from the small turn containment state to the working position, of the bucket 9 in an offset position in. which the bucket 9 lay before the

The levelling mode is for arm 8 when automatically containment flexing the it operation.

boom 6 and f rom a i I 1 containing the boom assembly 5, to maintain an opening plane of the bucket 9 substantially level.

A sequence of controlling the backhoe, particularly the boom assembly, according to the present invention will be described next. The following description contains the terms "scooping direction" and "dumping direction" to define operating directions of the angle forming components of the boom assembly 5. The "scooping direction" means a direction in which the bucket is guided to break and pick up earth. The "dumping direction" means a direction in which the bucket is guided to throw out a load.

When the backhoe is started, the program shown in Fig. 6 is started for the control unit 11. After checking parameters and initializing variables, various processes are carried out in a time- sharing mode. That is, various processes are carried out in the form of interrupt actions taking place at predetermined intervals of time. Such interrupt processes include a main process, a process of signal input from the potentiometers, a process of input from the various control mode switches, a display process for a control panel, and a process of output to the valve drivers. In the main process, amounts of operation of various drive devices of the backhoe are L determined according to the various control modes. In the sensor signal input process, signals from the potentiometers acting as the sensors are accepted and converted into forms for use in the main process. In the process of input from the control mode switches, signals from the switches for setting control modes are accepted and converted into the forms used in the main process and necessary preparations are made. When, for example setting of the fold mode switch is confirmed, an amount of offset detected at that time is stored in a predetermined RAM area.. In the display process. all data displayed on the control panel provided in the driver's section are controlled. In the process of output to the valve drivers, control signals are applied to appropriate valve drivers in accordance with amounts of cylinder operation determined and stored in the main process.

The main process will particularly be described hereinafter.

Referring started, a control mode prepared in the process of input from the control mode switches is accepted at step #10. Next, a data of input from a control lever or the like prepared in the sensor signal input process are accepted at step #15. An amount of valve operation is computed from this data at step #20. The to Fig. 7, when the main process is A 1 result of this computation is written into a predetermined RAM area at step #25. Further, joint angle data of the boom, bucket arm and bucket prepared in the sensor signal input process and representing the posture of the boom assembly are accepted at step #30. In the subsequent steps, various control modes are checked; step #40 checks whether the offset control mode is set or not and, if executed to call a subroutine for Similarly, steps #50, #60 and #70 control mode, fold control mode if these S it is, step #45 the offset control check the levelling and offset return control mode and, modes are. set, corresponding subroutines are called at steps #55, #65 and #75.

Subsequently, a cushion control process and a danger avert process are carried out at steps #80 and #90. In the course of these control mode routines and processing routines, the amount of valve operation is renewed as necessary. The amount of valve operation written at this time forms a basis for producing a control signal for application to a valve driver in the valve driver output process which is a separate interrupt routine. In response to this signal, the valve driver applies an appropriate current to the associated valve, thereby ultimately to drive the corresponding cylinder.

a The subroutines called in the main process will be described next.

Fig. 8 shows a flowchart of the offset control. After the direction of offset is checked at step #110, a proper value is taken from an offset control table at step #120 in accordance with the data on the offset lever control stored in the predetermined RAM area. Then an amount of control used in the valve driver associated with the offset cylinder is computed and written at step #130.

Fig. 9 shows a flowchart of the levelling control. Firstly, at steps #210, #220 and #230, actual bucket, bucket arm and boom angles are computed from the data prepared in the sensor signal process.

At step #240, a bucket angle relative to the vehicle body is derived from these angles, and a deviation: f from a reference angle for levelling the opening plane of the bucket is computed. An absolute value of this deviation is compared with an allowance value: dA at step #250. If the deviation is within a range of allowance, the bucket control is omitted (step #260).

Otherwise, a control gain corresponding to the detected bucket angle is determined at step #270. An amount of bucket control is derived from the control gain and deviation: f at step #280, and is written into a predetermined RAN area at step #290.

1 Fig. 10 shows a flowchart of the containment fold control. In this routine, checking is made step #305 as to presence of a command for lowering the boom or movement of the arm in the dumping direction. If such a command is present, the program jumps to step #395 for cancelling the fold control immediately. This means stopping the fold control in progress on a decision that an operation traversing the fold control has manipulates a control lever to lower the boom actuate the bucket arm in the dumping direction.

or at of occurred when the operator or if the answer is "NO" at step #305, the program moves to step #310 to set the amount of boom control to a maximum value in the upward direction, and the amount of bucket arm control to' a maximum value in the scooping direction. Next, a height of the bucket from the ground is computed at step #315. If the height exceeds 1m, steps #320 to #350 are executed to set an amount of offset control. If not, the offset control is dangerous and, control is not set an amount of offset is compared with determine whether therefore, an amount of offset for the fold control. In setting control, firstly, an offset angle a target value at step #320 to the offset effected rightward or leftward. exceeds the target value, a A control should be If the offset angle rightward offset is required. Then, the amount of offset control is set to a maximum value rightward at step #325, and an offset direction flag is set to right at step #330. If the offset angle is less than the target value, a leftward offset is required. Then, the amount of offset control is set to a maximum value leftward at step #340, and the offset direction flag is set to left at step #350.

Subsequently, step #360 is executed to check if the boom is in position for containment, i.e. if the boom angle is at its maximum. If the answer is in the affirmative, the amount of boom control is set to zero at step #365. Similarly, step #370 is executed to check if the bucket arm is in position containment maximum.

for i.e. if the bucket arm angle is at its If the answer is in the affirmative, the amount of arm control is set to zero at step #375.

Next, whether the offset control is completed or not is checked at step #380. The rightward offset control is completed if the offset angle is less than the target value. The leftward offset control is completed if the offset angle is greater than the target value. If the offset control is found completed, the amount of offset control is rewritten into zero at step #385. Then, at step #390, whether the boom assembly is in the contained position or not it i is determined by checking if the amount of offset control, the amount of boom control and the amount of bucket arm control are all set to zero. If the boom assembly is in the contained position, step #395 is executed to cancel the fold control command and the levelling control command started with the fold control.

Fig. 11 shows a flowchart of the offset return control. In this routine, a change of the fold mode switch from OFF to ON is confirmed in the process of input from the various control mode switches. Upon this confirmation, a detected offset value, i.e. an offset value of the boom assembly before containment, is read from the predetermined RAM area at step #410. This previous offset value read is compared with a currently detected offset value at bucket must be moved rightward previously offset position, the step #420. If the to return to the amount of offset control is set to the maximum value rightward at step #430. If the bucket must be moved leftward, the amount of offset control is set to the maximum value leftward at step #440. The offset return control is completed when the detected offset value equals the previous offset value (step #440). Then the offset return control is cancelled at step #450.

Though not particularly described herein, it i A possible to provide a plurality of areas for storing offset values at a folding time, and a switch for selecting one of these values, which is read at step #410. This will enable the bucket, after a folding operation, to be reinstated in a desired offset position. It is also possible to store not only the offset position or positions but the boom angle, arm angle and bucket angle. Then, the boom assembly may be reinstated in the posture that the boom assembly took prior to a folding operation.

Figs. 12A and 12B show a flowchart of the cushion control. Shocks may conveniently be damped by reducing piston speed the closer to stroke ends in driving the boom cylinder, arm cylinder and offset cylinder used for the boom assembly. The cushion control is intended primarily for controlling the respective cylinders such that the moving speed of the pistons are reduced in the vicinity of stroke ends.

The boom cylinder is checked first. If the boom cylinder is driven in a stroke end region and in a direction to raise the boom (steps #500 and #505), a distance to the stroke end is computed from a detected boom angle, and a predetermined optimal value for boom control is derived from the result of computation (step #510). This optimal value is determined so that the operating speed is increased in proportion to the it distance from the stroke end, for example. The value thus derived is used in rewriting the amount of boom control at step #515. The bucket arm cylinder is checked next. If the bucket arm cylinder is driven in a stroke end region and in the scooping direction (steps #520 and #525), a distance to the stroke end is computed from a detected bucket arm angle, and predetermined optimal value for bucket arm control the scooping direction is derived from the result computation (step #530). The value thus derived a in of i S used in rewriting the amount of bucket arm control at step #535. Then the bucket arm cylinder is checked with respect to the dumping direction. If the bucket arm cylinder is driven in a stroke end region and in the dumping direction (steps #540 and #545), a distance to the stroke end is computed from a detected bucket arm angle, and a predetermined optimal value for bucket arm control in the dumping direction is derived from the result of computation (step #550). The value thus derived is used in rewriting the amount of bucket arm control at step #555. Similarly, steps #560 to #595 are executed to effect the cushion control of the offset cylinder in stroke end regions for rightward offset movement and leftward offset movement, respectively. This control sequence corresponds to that of the arm cylinder, and its 4 description is not repeated here.

Subsequently, a cushion control is carried out for the offset cylinder C4. This control decelerates the movement of the offset cylinder C4 adjacent a target position in order to stop the cylinder at the target position accurately. When the bucket is moved leftward by means of the offset mechanism, the bucket, under the force of inertia or the like, could overrun the target position. In some cases, the bucket could contact the driver's section to present a serious danger. To avoid such a situation, the decelerating process is effected during leftward movement of the bucket.

The concept of danger zones defined around the driver's section will now be described with reference to Figs. 14A and 14B.

Fig. 14A shows the danger zones around the backhoe. A first front danger line FL1 is set forwardly of the driver's section, and a second front danger line FL2 is set forwardly of the first front danger line FL1. A first side danger line SL1 is set to the righthand side of the driver's section, and a second side danger line SL2 is set outwardly of the first side danger line SL1. The danger zones defined by the front danger lines are intended to prevent the bucket from approaching the driver's section from the J1 1 front. The danger zones defined by the lines are intended to prevent the approaching the driver's section from side. Further, as shown in Fig. 14B, a for the boom angle is additionally set forwardl- of the driver's section to the upward movement of the boom when in the angular range: Z formed by lines VL1 and VL2.

Reverting the cushion control, the sequence beginning at step #600 is a decelerating process to avoid danger in controlling the offset mechanism. This operation is carried out in order to minimize the possibility of the offset cylinder C4 causing the bucket to move further leftward from a set position during folding of the boom assembly.

First, checking is made at step #600 whether the offset mechanism is moving leftward or not. Only when the answer is in the affirmative, the program moves to step #610 to check if the fold control is in progress. When the fold control is in progress, step #620 is executed to check if the bucket lies inwardly of the second side danger line SL2. Only if it does, a deviation from a target value is derived from a current 6ffset position and a predetermined offset target position, the latter being an offset position to which the boom assembly is folded, and the side danger bucket from the righthand limiting zone in a space Conditions are set the boom lies 9 deviation is used as a parameter for determining an amount of deceleration offset control (step #630). The amount of offset control thus determined is used to rewrite the stored amount of offset control at step #640.

If step #610 finds that the fold control is off, step #650 is executed to check if the bucket lies inwardly of the second side danger line SL2 and the bucket arm lies inwardly of the second front danger line FL2. Only when they do, a deviation from a target value is derived as noted above, which is used as a parameter for determining an amount of deceleration offset control (step #630). The amount of offset control thus determined is used to rewrite the stored amount of offset control at step #640. if the above conditions are not met, the cushion control is terminated without rewriting the stored amount of offset control.

The danger avert control will be described next with reference to the flowchart of Fig. 13. This control is also effected in relation to the danger zones shown in Figs. 14A and 14B. With the type of backhoe according to the present invention, an upward swing of the boom and a swing in the scooping direction of the bucket arm cause the bucket to move from front towards the driver's section, and an offset Z movement of thebucket involves movement of the bucket from a righthand side position towards the driver's section. The danger avert control, therefore, prohibits the upward swing of the boom and the swing in the scooping direction of the bucket arm in the front danger zone, and the leftward offset movement in the side danger zone. Further, to ensure the danger avert control, a deceleration zone is defined outwardly of the second front danger line FL2 for cylinders in accordance with distances of the boom and arm to the danger zone.

In the danger avert control, when commands for operating the boom assembly are given by manual operation of the control levers 10a and 10b and offset lever 10c, posture of the boom assembly, i.e. positions and moving directions of the components of the boom assembly, are computed from detection data regarding the boom angle, arm angle and offset amount then available. When these positions and directions are problematic, amounts of operation of corresponding cylinders are reduced or, if necessary, rewritten into zero. For example, if the bucket lies inwardly of the second side danger line SL2 and the arm inwardly of the first front danger line FL1, the leftward offset movement is cancelled. If the bucket lies inwardly of slowing down operation of the corresponding 4 the first side danger line SL1 and the arm inwardly of the second front danger line FL2, the swing of the arm in the scooping direction is cancelled. If the bucket lies inwardly of the first side danger line SL1, the arm inwardly of the second front danger line FL2, and the boom angle within the angular range between the lines U1 and VL2, the upward swing of the boom also is cancelled. If the bucket lies inwardly of the second side danger line SL2 and the arm inwardly of the second front danger line FL2, whether the boom and bucket lie in the deceleration zone, i.e. the distance to the danger zone, is computed and a decelerating process is carried out accordingly.

Specifically, in the routine shown in Fig. 13, checking is made at step #700 whether the bucket lies inwardly of the second side danger line SL2. If not, this routine is terminated since the danger avert control is not required. If the bucket lies inwardly of the second side danger line SL2, step #705 is executed to check whether the bucket arm lies inwardly of the second front danger line FL2. If the bucket arm lies outwardly of the second front danger line FL2, the concept of the deceleration zone noted hereinbefore is introduced. Thus, at step #710, the amount of bucket arm control is derived, as necessary, from the distance, with the current boom angle, of the it i i i bucket arm to the danger zone, and the amount of boom control from the distance, with the current bucket arm angle, of the boom to the danger zone. At step #715, the respective amounts of control are rewritten into the values determined above. If the bucket arm inwardly of the second front danger line operations of the bucket, bucket arm and boom lies FL2, are cancelled in the following sequence, as necessary.

depending on the positions thereof.

First, if the bucket arm lies inwardly of the (step #720) and the progress (step #725), is rewritten into zero (steps #730 and #735). Thus, the offset control set before commencement of this routine is cancelled.

Next, if the bucket lies inwardly of the first side danger line SM (step #740) and the bucket arm is moving in the scooping direction (step #745), the amount of arm control is rewritten into zero (steps #750 and #755). Thus, the bucket arm control set before commencement of this routine is cancelled.

Finally, if the boom angle is within the angular range defined by lines VL5 and U6 (step #760), the bucket lies inwardly of the first side danger line SL1 (step #765) and the boom is being raised (step #770), the amount of boom control is rewritten into zero first front danger line FL1 leftward offset control is in the amount of offset control i 1 4 (steps #775 and #7380. Thus, the bucket arm control set before commencement of this routine is cancelled.

The above process cancels the control resulting in the boom assembly, particularly the bucket, approaching the driver's section to a dangerous extent.

In this way, the amount of control initially set through the control lever 10a or 10b or offset lever 10c is reduced or cancelled, as necessary, through the routine of cushion control or danger avert control. The resulting final value is used in the output process noted hereinbefore, thereby to actuate the valve drivers and hence the cylinders. With such a method, priority is given to the amount of cylinder control derived from a subsequent processing routine. Depending on the boom assembly construction and cylinder strokes, the amount of deceleration control computed in the danger avert control routine could exceed the amount of control computed in the preceding cushion control routine, for example. To avoid such an inconvenience, a condition may be set to data rewriting so that a value is not replaceable by a greater value.

it I 1

Claims (4)

1. We claim:

   A backhoe comprising; a swivel deck, a driver's section mounted on said swivel deck, a boom assembly provided in a region laterally of said driver's section, said boom assembly including a boom vertically swingably connected to said swivel deck, an offset mechanism connected to said boom for horizontal offset movement relative to said boom, a bucket arm vertically swingably connected to said offset mechanism, and a bucket vertically swingably connected to a forward end of said bucket arm, boom assembly drive means for driving the components of said boom assembly, posture detecting means for detecting posture of said boom assembly, said posture detecting means including a boom angle sensor for detecting a swing angle of said boom, an offset sensor for detecting an offset amount of said offset mechanism transversely of said bucket detecting a bucket angle said bucket, control through said A arm, a bucket arm angle sensor for swing angle of said bucket arm, and a sensor for detecting a swing angle of and means for controlling said boom assembly boom assembly drive means, j k k characterized in that. said control means has a folding mode for folding said boom assembly into a position substantially contained within a region of said swivel deck, and an unfolding, working mode for extending said boom assembly position, that from said swivel deck region to a working said control means includes a storage for storing data received from said posture detecting means with a change from said working mode to said folding mode, and that said control means has a function to reinstate at least one component of said boom assembly in a previous position in accordance with the data stored in said storage upon return from said folding mode to said working mode.
2. 2. A backhoe as claimed in claim 1, characterized in that said storage has a capacity for storing a plurality of data, and that means is provided for selecting one of the plurality of data, at least one component of said boom assembly being reinstated in the previous position in accordance with the selected one of the data.
3. 3. A backhoe as t claimed in claim 1 or 2, 1 characterized in that said control means is operable to input data from said offset sensor to said storage when changing from said working mode to said folding mode, and to reinstate said offset mechanism in a previous offset position upon return from said folding mode to said working mode.
4. 4. A backhoe as claimed in any one of claims 1 to 3, characterized in that said control means is operable to control said boom assembly drive means for maintaining an opening plane of said bucket substantially level during a transition from said working mode to said folding mode.

   A Published 1991 at The Patent Office. Concept House. Cardifr Road. Newport. Gweni NP9 I RH. Further copies may be obtained from Sales Branch. Unit 6. Nine Mile Point. Cuinfelinfach. Cross Key Newport. NPI 71a. Printed by Multiplex techniques Itd. St M2rY Cnky. Rent.