Operation control mechanism of lifting apparatus

Abstract: A lifting apparatus including a chassis (1) having front and rear ends, and a drive unit (64) for moving the chassis in forward or rearward directions. A turntable (5) is mounted on the chassis (1) for horizontal turning movement between front and rear positions. Boom assembly (10) is mounted on the turntable and has a bucket (11) mounted adjacent the free end thereof. An operating mechanism (16) including an operator-actuated driving member (20, 120) is mounted on the bucket (11) for controlling the forward and rearward traveling direction of the chassis (1). The driving member (20, 120) is movable in opposite first and second directions relative to the boom assembly (10) for respectively causing forward and rearward travel of the chassis (1) when the turntable (5) is in the front position. A reversing arrangement (27, 28, 30, 135) reverses the controlling direction of the driving member (20, 120) when the turntable (5) is in the rear position so that movement of the driving member (20, 120) in the first and second directions relative to the boom assembly (10) respectively causes backward and forward travel of the chassis (1).

Description: The present invention relates to a lifting apparatus for use, for example, in constructing buildings, repairing highways, painting and the like at elevated locations in order to load operators or materials on a bucket attached thereto, and particularly to an operation control mechanism of the lifting apparatus capable of controlling the drive of a chassis of the lifting apparatus forward or backward in the same direction as the bucket is directed irrespective of the positional relationship between a turntable and the chassis. There has been employed a lifting apparatus capable of raising or lowering an elevator or a bucket for assembling, painting and repairing at elevated locations such as a highway or building construction, wherein the operator or the material is loaded on or unloaded from the bucket or the elevator. The lifting apparatus of this type is classified as a boom-type, scissors-type, X-type and the like. It is common to any type of such lifting apparatus that a control apparatus is installed in the bucket for controlling a chassis of the lifting apparatus. The operator on the bucket operates the control apparatus provided inside the bucket so that the lifting apparatus can perform various operations whereby the bucket can be raised to the height required for the working. There have been employed in many cases a lever-type or joystick type mechanism in which the lever is pushed or pulled for turning on or off the switch so that a three-directional valve is switched for supplying oil under pressure. The three-directional valve is controlled to control the supply of oil under pressure to each part of the lifting apparatus and the adjustment of the amount of oil under pressure. The lifting apparatus of this kind has an advantage that scaffolds can be omitted which enhances the convenient workability but a disadvantage that the operator is liable to involve unexpected accident at the time of operating the lifting apparatus. Particularly, in the typically used boom-type lifiting apparatus, the turntable mounted on the chassis can be turned horizontally 360° relative to the chassis. In view of such mechanism, the operator is liable to be involved in an accident at the time of driving the chassis forward or backward. For instance, if the turntable is directed forward relative to the chassis, the chassis can move forward by pushing a lever forward. However, the lever to be pushed in forward direction or pulled in backward direction can be controlled with keeping the relation between the chassis and the turntable or the bucket but without any relation between the pushing or pulling direction of the lever and the direction of the turntable or the bucket. That is, the direction where the driving lever pushed or pulled is not at all related with the chassis direction where the turntable or the bucket is turned. Accordingly, when the chassis is traveled forward or backward while the turntable is turned 180° relative to the chassis, i.e. in the rearward direction of the chassis and hence opposite to the normal forward direction, the operator feels a reverse driving feeling, i.e. as if he drove the chassis backward. That is, if the lever is pushed, i.e. in the forward direction of the bucket, the chassis travels forward while the turntable is directed to the rear side of the chassis. That is, the operator feels as if he drove the chassis backward. Accordingly, the operator must operate in a feeling reversed to the ordinary driving feeling. Furthermore, in such a case, i.e. at the state where the turntable is turned 180°, an accident is more liable to occur. For example, if a beam or other building approaches the back of the operator in this case, a collision or the like is liable to occur which can be very dangerous. That is, there is a case that the operator pushes the lever forward for driving the turntable and the chassis forward in the normal driving mode in the direction of the boom. However, if the turntable on the chassis is turned backward relative to the chassis, then the chassis travels forward (i.e., opposite the direction of the boom). As a result, there may occur an accident in that the operator may be caught in the space between the bucket and a beam or building. To minimize the chance of an accident resulting in injury or death, it is preferable to indicate the position of the turntable relative to the chassis on an indication panel of the control apparatus. However, the operator frequently overlooks the indication on the panel during the operation and realizes the mistake of the operation only when involved in an accident. Although the structure having the turntable capable of turning through a full horizontal rotation relative to the chassis is very convenient in working operations such as repairing and painting at elevated locations, it is very dangerous to drive the chassis forward while the turntable is directed to the rear of the chassis since the operator feels as if he is driving the chassis backward. The reader will be further enlightened as to the nature of the prior art by reference to the disclosures in U.S. 3,584,705 and U.S. 4,066,143. The features common to the present invention and U.S. 3,584,705 are presented in the precharacterising clause of claim 1. The present invention provides a lifting apparatus in accordance with claim 1. It is an object of the present invention to provide an operation control mechanism of a lifting apparatus capable of directing the drive control lever in a direction toward the travelling direction of the chassis at all times. As a result, the operator's driving feeling is always constant irrespective of the direction of the turntable relative to the chassis. Consequently, accidents resulting in injury or death caused by the reverse driving feeling of the operator can be prevented. It is an object of the present invention to provide an operation control mechanism capable of turning the operating means in the horizontal direction, and turning the operating means so as to compensate for the turning angle detected by a detector disposed between the chassis and the turntable. With this mechanism, the chassis travel direction and the operating lever movement direction are always kept in parallel with one another. A lifting apparatus constructed in accordance with the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a perspective view showing a lifting apparatus employing an operation control mechanism according to a first embodiment of the present invention; Figs. 2(A) and 2(B) explain the operation of the lifting apparatus; Fig. 3 is an enlarged perspective view showing a bucket and a portion adjacent to the bucket in Fig. 1; Fig. 4 is an enlarged perspective view showing a relationship between a chassis and a turntable, respectively constituents of the lifting apparatus in Fig. 1; Fig. 5 is a cross-sectional view showing a synchronising mechanism of the lifting apparatus; Fig. 6 is an exploded perspective view of Fig. 5, in which a part of the synchronising mechanism in Fig. 5 is omitted; Fig. 7 is a block diagram showing a control system of the lifting apparatus; and Fig. 8 is a view showing the operation of the synchronising mechanism. The lifting apparatus comprises: a movable chassis 1 having front and rear wheels 2 and 3 supported on the chassis at the right and left sides, a turning shaft (described later) protruding from the central upper surface of the chassis 1, a cylindrical skirt 4 for covering the turning shaft and a turntable 5 placed on the skirt 4 to turn horizontally through a full revolution and housing an engine and a generator for producing oil under pressure and the like. The lifting apparatus further comprises a pair of triangular shaft supporting members 6 fixed to the upper surface of the turntable 5, a long lower boom 7 which is hollow inside and square in cross-section and pivotally mounted at the lower end thereof on the apexes of the triangles of the shaft supporting members 6 by a horizontal pivot pin 8. The lower boom 7 swingable vertically up and down about the pin 8, and a long upper boom 9 which is square in cross-section and telescopically slidably inserted into an opening defined in the upper portion of the lower boom 7. A boom assembly 10, is composed of the lower and upper booms 7 and 9, is telescopically extensible in the longitudinal direction thereof by a hydraulic cylinder (not shown) provided therein. A square boxed type bucket 11 is connected to the tip end of the upper boom 9 by a pivot pin 12. A correction hydraulic cylinder 13 is interposed between the upper boom 9 and the bucket 11 for correcting the posture of the bucket relative to the upper boom 9 so as to maintain the bucket horizontal. A hydraulic cylinder 14 is interposed between the turntable 5 and the lower boom 7 for inclining the lower boom 7 relative to the turntable 5. The lower boom 7 and the hydraulic cylinder 14 are connected with each other by a pivot pin 15. The bucket 11 is formed of round pipes welded with each other and is of skeletal construction. A metal net covers the lower portion of the bucket 11 for preventing the operator or materials from falling out. An operation mechanism 16 is attached to the inside of the bucket 11 for operating the lifting apparatus. The bucket 11 and the portion adjacent to the bucket 11 are illustrated in Fig. 3. The bucket 11 is made of a combination of metal pipes and a steel plate and shaped like a bird cage. An upper portion of the bucket 11 is opened and a lower portion of the bucket 11 is formed of the steel plate for preventing the operator and the materials from falling therefrom. An operating mechanism 16 is provided inside the bucket 11 and an electric circuit is incorporated in the operating mechanism 16 for controlling a fluid system and an electrical system. Protruding from a top panel of the operating mechanism 16 is a driving lever 120 for controlling forward or backward travelling of the chassis 1 and a steering lever 121 for controlling right or left turning of the chassis 1. Other operation means, e.g. those for inclining or telescopically moving the boom assembly 10 are conventional and are omitted. A protruding turning shaft 125 is ring shaped and has a shaft supporting hole opening vertically at the central portion thereof, into which a main shaft (not shown) attached to the lower surface of the turntable 5 is inserted by way of bearings and the like interposed between the shaft supporting hole and the main shaft. The driving lever 120 is held by a rotary panel 122 which is disposed on an upper surface of the operating mechanism 16 and is rotatable horizontally, while the steering lever 121 is held by a rotary panel 123 which is disposed on the upper surface of the operating mechanism 16 and is rotatable horizontally. The turning shaft 125 on the chassis is described in more detail with reference to Fig. 4. The ring shaped turning shaft 125 for holding the turntable 5 protrudes from the chassis 1 and has a detection hole 126 defined by a vertical opening at the centre of the shaft 125. A groove 127 extends diametrically through the detection hole 126 for enabling synchronisation between the rotary panels 122 and 123 and the turntable 5. There is fixed inside the skirt 4 a rotary encoder 128 which is rotatable together with the turntable 5 and detects the horizontal rotary angle relative to the chassis 1. A detection shaft 129 rotatably protrudes from the rotary encoder 128 and is inserted into the detection hole 126 while a pin 130 protrudes from both sides of the detection shaft 129 and is engaged in the groove 127 to prevent relative rotation between the detection hole 126 and the detection shaft 129. The synchronous mechanism 135 provided inside the operation mechanism 16 will be described in more detail with reference to Fig. 5. The synchronising mechanism 135 of the driving lever 120 and the rotary panel 122 is explained hereinafter. However, the explanation of the arrangement of the synchronising mechanism of the steering lever 121 and the rotary panel 123 will be omitted since the arrangement of the synchronising mechanism of the driving lever 120 is the same as that of the steering lever 121. A middle housing panel 137 is provided in parallel with but under the top or cover panel 136, and the two holding legs 138 are fixed to the upper surface of the middle panel 137 at a given interval. An intermediate plate 139 is fixedly placed on the upper surface of the holding legs 138 and positioned between the cover panel 136 and the middle panel 137. A circular opening 140 is defined at a central portion of the intermediate plate 139 and a bearing 141 is provided around the opening 140. A substantially cup shaped holding body 142 is rotatably placed on the upper surface of the bearing 141. The upper end of the holding body 142 protrudes through an opening 143 defined in the cover panel 136, and the rotary panel 122 is fixed to the upper end of the body 142. The opening 143 is closed by the rotary panel 122 to prevent rain or wind from entering the operation mechanism 16. The rotary panel 122 has a switch 144 fixed thereto from which switch 144 the driving lever 120 protrudes. The holding body 142 has an opening 145 in the centre of its bottom and a cylindrical body 146 is connected to the bottom of the opening 145 by way of the bearing 141 and the hole 140 so that the cylindrical body 146 can rotate together with the holding body 142. A slip ring is provided at the side of the cylindrical body 146. The slip ring is electrically connected with the switch 144 by a cable 147. An electric force collector 148 contacts the outer circumference of the slip ring. A rotary encoder 149 is fixed between the two holding legs 138 and has a detection shaft 150 engaged with the lower portion of the cylindrical body 146. A gear 151 having a large diameter is fixed to a lower circumference of the holding body 142 and meshes with a gear 152 having a small diameter at the outer circumference thereof. The gear 152 can be driven by a stepper motor 153 fixed to an intermediate plate 139. A principle portion of the synchronising mechanism 135 is illustrated in Fig. 6. A control circuit for driving the synchronising mechanism 135 will be described with reference to Fig. 7. An output of the rotary encoder 128 is supplied to an angle detecting circuit 160 which electrically converts the output of the rotary encoder 128 into an angle signal which is supplied to each comparator 161 and 162. Outputs of the comparators 161 and 162 are supplied to drivers 163 and 164 respectively. An output of the driver 163 is supplied to a stepper motor 153 of the synchronising mechanism 135. An output of the driver 164 is supplied to a stepper motor 153' for driving a synchronising mechanism 135' of the steering lever 121. An output of the rotary encoder 149 provided at the synchronising mechanism 135 of the driving lever 120 is supplied to the comparator 161 as a correction signal. An output of the rotary encoder 149' provided at the synchronising mechanism 135 of the steering lever 121 is supplied to the comparator 162 as a correction signal. The operation of the control mechanism according to the embodiment of the present invention will be described hereinafter with reference to Fig. 8 which exemplifies the case where the turntable 5 is horizontally turned clockwise 360° about the chassis 1. When the turntable 5 is turned relative to the chassis 1, the detection shaft 129 is rotated relative to the turntable 5 since the detection shaft 129 is connected to the chassis 1 so that the rotary encoder 128 fixed to the turntable 5 detects the rotary angle. The output detected by the rotary encoder 128 is supplied to the angle detector 160. The angle detector 160 judges the rotary angle, i.e. an angular interval between the turntable and the chassis which stays at the position (J) in Fig. 8 and provides a turning angle signal as a control signal which is supplied to the comparator 161 and 162. The comparators 161 and 162 supply the turning angle signal to the drivers 163 and 164 for driving the stepper motors 153 and 153'. The rotary motions of the stepper motors 153 and 153' are transmitted to the gears 152. The gears 151 having the large diameter meshing with the gears 152 are rotated when the gears 152 are rotated. Since the gears 151 and the holding bodies 142 are supported by the bearings 141, the gears 151, the holding bodies 142, the cylindrical bodies 146 and the rotary panels 122 and 123 are rotated at the same time. At the time when the holding body 142 is rotated, the rotary encoder 149 and 149' connected to the respective cylindrical body 146 detects the rotary angle and supplies it to the respective comparator 161 and 162 as a feedback signal. Accordingly, the stepper motors 153 and 153' are driven for the angle corresponding to the angular interval between the turntable and the chassis. Hence, the rotary angle of the holding body 142, the cylindrical body 146, and the rotary panels 122 and 123 accords with the angular interval between the turntable 5 and the chassis 1. In the state where the turntable is turned 45° in the direction of R-1 as illustrated at (K) in Fig. 8 , the rotary panels 122 and 123 each turn 45° in the directions of S-1 and T-1 respectively. Accordingly, the operation directions of the driving lever 120 provided at the rotary panel 122 are kept in parallel with front and rear directions of the chassis 1. Furthermore, the steering lever 121 provided at the rotary panel 123 rotates to be right angled relative to the front and rear directions of the chassis 1. Accordingly, the chassis 1 moves forward or backward in the direction where the driving lever 120 is respectivley pushed away from or pulled toward the operator. When the steering lever 121 is pushed rightward or leftward at the rotary panel 123, the chassis 1 can be turned in the direction where the steering lever 121 is pushed. Furthermore, even if the turntable 5 is turned 360° in the direction of R-2, R-3, R-4, R-5, R-6, R-7 and R-8, the rotary panels 122, 123 rotate in the directions of S-2, T-2, S-3, T-3 .... following the turning of the turntable 5 so that the directions where the driving lever 120 and the steering lever 121 are pushed are always respectively kept parallel with and at a right angle relative to the chassis 1 front/rear movement direction. Particularly, in the case where the operation mechanism 16 is turned 180°, i.e. in opposite direction relative to the chassis 1 at the position denoted (N) in Fig.2 , the rotary panel 122 is also turned 180° so that the direction where the driving lever 120 is pushed is also turned 180°. Accordingly, if the driving lever 120 is pushed forward at the state denoted at (N) in Fig.8 where the turntable is positioned in opposite direction relative to the normal front of the chassis 1, the chassis 1 travels backward (right in Fig. 8) whereby the direction where the driving lever 120 is pushed completely accords with the travel direction of the chassis 1. Consequently, the driving and steering levers provided at the operation mechanism 16 follow so as to be operated in the same direction as the direction where the bucket 11 is directed. As a result, the drivers orientation feeling is kept constant irrespective of the position of the turntable 5 relative to the chassis 1. With the arrangement of the operation control mechanism, the operation control mechanism is always directed in the same direction even if the turntable is turned in any direction relative to the chassis so that the chassis can travel or turned in the direction where the driving lever or the steering lever is pushed. Accordingly, the operator is free from the judgement of the direction to control the operation mechanism. The operator need not consider the direction of turning of the turntable relative to the chassis and does not feel any malaise. As a result, the operator does not erroneously operate the lifting apparatus, namely, wrongly pushes the driving lever at the time when the bucket approaches a beam or building. It is therefore possible to prevent the operator from being involved in the accident resulting in injury or death.

Claims: A lifting apparatus comprising: a movable chassis (1) having front and rear ends, and a drive unit (64) for moving the chassis (1) in both forward and rearward directions; a turntable (5) mounted on the chassis (1) to turn about a vertical axis through an angle of substantially 180 degrees between front and rear positions; an elevatable boom assembly (10) mounted on the turntable for horizontal turning movement relative to the chassis (1), the boom assembly (10) extending toward the front of the chassis (1) when the turntable (5) is in a front position and towards the rear of the chassis when the chassis is in a rear position, a bucket structure (11) mounted on a free end of the boom assembly (10), the bucket structure (11) being adapted to support an operator; an operating mechanism (16) including operator-actuated driving means (120) mounted on the bucket structure (11) for controlling the forward and rearward travelling direction of the chassis (1), said driving means (120) being movable in opposite first and second directions relative to the boom assembly (10) to cause forward travel of the chassis (1) when moved in the first direction and rearward travel of the chassis (1) when moved in the second direction when the turntable (5) is in said front position, and characterised in that the boom assembly is extendible and in that there is provided reversing means (135) for reversing the controlling direction of the driving means (120) when the turntable (5) is in said rear position so that movement of the driving means (120) in said first direction causes the chassis (1) to travel in the rearward direction and movement of the driving means in the second direction causes the chassis (1) to travel in the forward direction, wherein said reversing means includes support means (141) mounting said driving means (120) for substantially horizontal rotation relative to the bucket structure (11), and control means proportionally responsive to the horizontal angular movement of the turntable (5) and wherein the control means includes a synchronised drive (153) for turning the support means (142) in synchronisation with the turning of the turntable (5). An apparatus according to claim 1, wherein the reversing means includes position detecting means (129, 160) for detecting the angular position of the turntable (5) relative to the chassis (1) for transmitting a signal for controlling the synchronised drive (153). An apparatus according to claim 1, wherein the driving means comprises a movably-operated lever (120) movable from a middle position in opposite directions toward said first and second positions. Apparatus according to claim 1 including steering means (121) for controlling the turning direction of the chassis (1) and wherein the reversing means also controls the steering means (121) relative to the boom assembly (10) so that both the driving means (120) and the steering means (121) are movable in the same direction relative to the intended travel direction of the chassis when the boom assembly is in either of the front or the rear position. Apparatus according to claim 1 comprising rotary holding means (122, 142, 151, 146, 123) for permitting the driving means (120) and the steering means (121) to turn horizontally relative to the boom assembly (10), and position comparison means for receiving a signal from detecting means (128, 149) and driving the synchronised drive so that both the driving means (120) and steering means (121) are not turned horizontally relative to the chassis irrespective of the angular position of the turntable.

Inventors: KISHI MITSUHIRO, KISHI, MITSUHIRO, KISHI, MITSUHIRO, C/O JAPANIC CORPORATION
Applicants: JAPANIC CORP, JAPANIC CORPORATION
Application year: 1991
Main classification: B66F11
IPC codes: B66F11