CABLE CARRIED LIFTING DEVICE, E.G. FOR PICKING UP LYING METAL PLATES FROM A PLATE RACK

Abstract: In factories and workshops it is difficult to take out lying metal plates from a shelf system, but the invention provides for a crane cable carried implement suitable for that use. The implement has a gripping frame (16) provided with suckers (18) for seizing the plate member (10) and with a rear, upstanding carrier arm (20, 54) topwise suspended in a crane cable (14, 26). The carrier arm is displaceable or pivotable over the gripping frame (16) by means of an air cylinder (32, 64) controlled by a level sensor (36, 68) on the frame. With manual support the implement can be introduced into a rack case for engaging the upper plate member (10) therein while the carrier arm (20, 54) assumes a vertical position just outside the front of the rack. When lifted slightly by the crane cable (14) the implement will assume an inclined position, whereby the level sensor (36) actuates the cylinder (32, 64) to displace or pivot the carrier arm inwardly over the gripping frame. Thereby the implement with the seized plate member will be forced outwardly from the rack, and the implement will adjust itself into a horizontal position of the carried plate member, which can then be moved for delivery to a desired receiver surface.

Description: Cable carried lifting device, e.g. for picking up lying metal plates from a plate rack. The present invention relates to a hoisting cable carried lifting device, mainly for picking up plate members from from a plate rack. For this application, but also for other applications, the problem exists that the lifting device should be brought into a carrier connection with the goods to be lifted in a position which is located entirely or mainly outside the hori¬ zontal position of the vertical hoist cable, which, by the taking out of articles from a rack, cannot be brought to initially assume a position just above the point of gravity of the article to be picked up, i.e. the load will be pronounced unbalanced relative the hoist cable. Lifting devices have previously been proposed, by which there is provided above a gripping part a hori¬ zontal carrier part, along which it is possible to dis¬ place a suspension eye for the hoist cable, such that it is thereby achievable that the load is substantially balanced, all according to the location of its point of gravity. Such a device, however, will for natural reasons be exploitable for the taking out of plate mem¬ bers from plate racks, where it is impossible to have the suspension eye located way in above the middle of a plate member underneath an overlying rack shelf. The purpose of the invention is to provide a lift¬ ing device which is advantageous for the said particular use, but also generally advantageous. The device or implement according to the invention has a basically horizontal gripping portion, by way of example a frame having lower suction cups for engaging a plate member to be lifted out of a plate rack, this gripping portion at its rear end having an upstanding carrier arm, which is topwise provided with means for its connection with a hoist cable, and which is pivotal- ly or displaceably connected with the gripping portion such that its upper end is movable forwardly over the gripping portion, servo controlled adjustment means being arranged between the gripping portion and the carrier arm for adjusting the positioning of the upper end of the carrier arm, said adjustment means being operatively connected with a controlling level sensor mounted on the gripping portion and adapted to affect, via a control unit, the adjustment means to move the upper end of the carrier arm inwardly over or outwardly from the gripping portion all according to this portion being inclined to one side or the other, in such a man¬ ner that the end of the carrier arm by this movement will approach the location at which the carrier portion will be suspended in a substantially horizontal or balanced position of eguilibriu . At the initial lifting, where the gripping portion is located mainly inside the rack and is cable suspended at its rear edge, the gripping portion as lifted at the rear edge will of course assume an inclined position, but with the described arrangement the adjustment means will hereby force the upper end of the carrier arm in¬ wardly towards the rack, as this will be the natural direction of displacement for achieving a balanced posi¬ tion. If the plate to be gripped is located in an upper, upwardly open section of the rack the said displacement may proceed until the balanced condition has been reached, but normally the plate will lye underneath another shelf in the rack, whereby the said displacement will be excluded. However, by the forced movement of the carrier arm, whether pivoted or displaced, a first important effect will be obtained, viz. that the carrier arm will be forced against an upper front side edge of the rack or against the front edge of an overlying plate pack, such that by this movement or action of the arm the gripping portion will be forced outwardly of the rack, during a phase, in which the lifted plate at its innermost edge will still rest against the underlying plate, as the lifted plate assumes an inclined position. Hereby the work of drawing out the plate is facilitated considerab¬ ly, as at least initially it will go on fully automati¬ cally, until an eguilibrium is achieved with the plate carried freely. Later during the drawing out of the plate the upper end of the carrier arm will be brought closer to the center of gravity of the carried load, whereby the load will approach a balanced condition, such that the inner end of the load exerts a weakened pressure against the underlying plate in the rack. Hereby a further manual withdrawal of the gripping portion will be facilitated, and soon the situation will be reached that the gripping portion with its carried load has been drawn out so far that it will become balanced owing to the concurrent inward displacement of the end of the carrier arm, and the carried load, then, will assume a substantially horizontal, slightly lifted position, such that it is liberated from the underlying plate, whereby it is easy to carry out the last part of the retraction from the rack. Thereafter the system may be raised and conveyed further, with the gripping portion located in a well controlled horizontal position, e.g. for delivery of a gripped metal plate member to a receiver table. After such a delivery the gripping portion will assume a position inclined to the other side, but the level sensor will then correspondingly cause the end of the carrier arm to be moved so far outwardly that an eguilibrium is reestablished, now with the unloaded gripping portion assuming a horizontal position. The carrier arm, which may optionally be embodied as an elongated carrier frame, may be pivotally con¬ nected with the rear edge of the gripping portion, but preferably it is arranged as an upstanding arm member, which, by means of a driving motor or cylinder, is dis- placeable relative to the gripping portion without being tilted. It is to be remarked that from FR 2,470,079 it is known to make use of a level sensor for controlling a plurality of hoisting cables in order to adjust a slant¬ ing load into a horizontal position, but this is not of particular relevance for the invention. In the following the invention is described in more detail with reference to the drawings, in which:- Fig. 1 is a perspective view of a lifting device according to the invention, shown next to a plate rack, Fig. 2-4 are side views illustration the operation of the device, Fig. 5 is a diagram of a control system belonging to the device. Fig. 6 is a perspective view of a modified embodi¬ ment of the device, Fig. 7 is a detailed view of a part thereof, and Fig. 8 is a perspective view of a preferred embodi¬ ment of the device. In Fig. 1 is shown a storage rack 2 having side portions 4 and shelves 6, on which piles or packs 8 of plate members 10 are placed, e.g. metal plates to be worked in a workshop. Outside the rack a lifting device 12 is shown suspended in a crane cable 14 and consisting of a horizontal carrier frame 16, provided with lower suction cups 18, and a frame member 20, which is up¬ standing from the rear end of the carrier frame and is pivotally connected therewith, through pivot bearings 22, the top part of the frame member 20 having connector means 24 for Y-shaped sub portions 26 of the crane cable At the middle of the frame portion 20 there is rigidly mounted a projecting arm 28, which at its outer end is pivotally connected with a piston rod 30 of an upstanding cylinder 32, the lower end of which is pi¬ votally connected with a rigid portion 34 of the carrier or gripping frame 16. When the cylinder 32 is actuated the arm 28 is swung upwardly and forwardly by a concur¬ rent forward pivoting of the cylinder, whereby the frame portion 20 is swung inwardly over the carrier frame 16. On this frame, e.g. near the cylinder 32, there is mounted a level sensor housing 36 holding a level sensor that controls the actuation of the cylinder, as ex¬ plained in more detail in the following. It is here presupposed that the cylinder 32 viewed from the suspension means 24 forms a counterweight rela¬ tive to the forwardly projecting part of the carrier frame to the effect that the latter, in a freely sus¬ pended condition of the device, will assume a horizontal position when the frame portion 20 assumes a vertical position, which will only be a question of a suitable balancing. Therefore, by means of a crane or a crab the operator may introduce the horizontal gripping frame 16 into any desired rack compartment between the side por¬ tions 4 and thereafter lower the device until the suc¬ tion cups 18 engage the top side of the plate member 10 to be gripped. As indicated in Fig. 2 it should be pre¬ ferred that the frame portion 20 is hereby located imme¬ diately next to the front plane of the rack, such that the outer end of this frame portion projects horizontal¬ ly outwardly past the side portions 4 of the rack. Cor¬ respondingly the crane cable 14 will be located just outside the front of the rack. Once the suction cups 10 have been brought into holding engagement with the plate 10 the crane cable 14 is raised somewhat, whereby the gripping frame 16 as shown in Fig. 2 will be brought to assume a slightly inclined position. This inclination is sensed by the said level sensor, which will thus cause the cylinder 32 to be actuated for forcing the piston rod 30 upwardly. As mentioned, the frame portion 20 is hereby forced to pivot inwardly over the carrier frame 16, and as shown in full lines in Fig. 3 this will result in the carrier frame 16 being drawn out of the rack, as the upper end of the frame portion 20 will engage the front edge of the rack sides 4. As shown in dotted lines this with¬ drawal may be brought still further, and optionally the crane cable may be slightly further raised. As the device with the gripped plate member 10 is gradually drawn out the suspension means 24, relatively, are moved correspondingly forwardly, until they reach a location just overhead the new, common center of gravity of the device and the plate member, and when this happens the gripping frame 16 will be swung to a horizontal posi¬ tion, whereby the level sensor will stop its actuation of the cylinder 32 and cause it to be blocked in the attained position. This position, which can be e.g. as shown in Fig. 4, allows for a free retraction of the remaining part of the device and the carried plate member from the rack and thereafter for a well controlled movement of the plate member to a desired loading place, where the plate member can be lowered and released in its horizontal position. When thereafter the device 12 is lifted from the released plate member this lifting will immediately result in a tilting of the device to the opposite side, viz. a tilting down of the left end of the device, Fig. 4. Also this is detected by the level sensor, which will thereby actuate the cylinder 32 in the opposite direc¬ tion, that is for retraction of the piston rod 30 and thus gradually for raising the frame member 20 until the initial eguilibrium is reestablished, with the frame member 20 vertically upstanding and the carrier frame projecting horizontally. The said level sensor housing 36 is also shown in Fig. 5, which illustrates a practical embodiment based on the use of compressed air. The housing contains an arched level tube 38 holding a steel ball 40, which, at either end of the tube, can cooperate with an actuator pin 42 of a switch over valve 44, all of well known design. The valves 44 serve to operate respective pri¬ mary control valves 46 for feeding compressed air to the respective ends of the cylinder 32, and for closing and venting the opposed cylinder chambers. The valves are fed with compressed air from a source 48 through respec¬ tive pressure regulators 50 and check valves 52. The operation of this unit should not be discussed in more detail at this place, as for relevant experts it will be clear that the unit will act as an automatic control unit for achieving that the gripping frame 12, when tilted to one side or the other, will be returned into a stabilized horizontal position. When the plate 10 is unloaded and the device there¬ after tilts to the other side, the left hand level valve 44 will be actuated to cause a return tilting of the device to its balanced normal position. It has already been mentioned that the upstanding carrier arm may be mounted displaceably rather than pivotably, and in practice this can even be preferred. The principle is illustrated in Fig. 6, where the car¬ rier arm designated 54 is rigidly mounted on a slide block 56, which is slidable mounted on a pair of steel shafts 58 extending between opposed end blocks 60 and 62 on the carrier frame 12. The rear block 62 carries a lying, rearwardly projecting working cylinder 64 having a piston rod 66, which projects through a hole in the block 62 and is rigidly connected with the sliding block 56. The level sensor is mounted in a box 68. The operation of the device shown in Fig. 6 will be identical with that already described, except that the carrier arm 54 will be displaced rather than pivoted. For the discussed forced withdrawal from the rack the arm will cooperate with the front edge of the overlying rack shelf. At least in principle it will be a possibility that the carrier arm be mounted on the block 56 in a cross displaceable system thereon, such that the carrier arm is laterally displaceable, manually or automatically, for reestablishing lateral equilibrium, should the load hang down at one side. In Fig. 7 is illustrated another design of the level sensor. The two control valves are each associated with a pendulum arm having a lower weight body, and preferably there is mounted, under each weight body, a damping plate depending into an underlying oil bath for damping the pendulum movements, so that undesired fluc¬ tuations in the control function will not arise. In Fig. 8 is shown a preferred embodiment, which corresponds to Fig. 6 except that the cylinder 64 may here be replaced by a gear motor contained in a housing 70 and driving a screw spindle 72, which replaces the piston rod 66 in Fig. 6 for moving the carrier arm 54. However, it would still be possible and even preferable to also here use a pneumatic cylinder in lieu of the gear motor, as the block 56 may be mounted on a slide that is reciprocally drivable by means of an underlying air cylinder. With the use of a displaceable carrier arm 54 this arm should not necessarily be particularly highly up¬ standing from the carrier frame 16; the crane cable may even be secured directly to the block 56. As illustrated in Fig. 8 it is highly advantageous to incorporate the gripping and lifting device in a local transport system between a specific plate working machine and an associated storage rack for the plates. The system here shown comprises a swivel crane that will provide for a particularly easy handling. Here the lift¬ ing device is provided with a handle making it easy for the operator to orient the plate correctly for delivery to the machine table.

Claims: C L A I M S : 1. A hoist cable carried lifting device for carry¬ ing an initially unbalanced load, primarily for crane operated removal of lying metal plates from plate racks in factories and workshops, comprising a gripping por¬ tion projecting laterally from an upstanding carrier member and being operable to grip the relevant load, while the top of the carrier member is adapted for con¬ nection with a hoist cable and, moreover, is displace¬ able for changing the location of the cable suspension point relative to the gripping portion, characterized in that the carrier member (20,54) is length displaceably or pivotally connected with the gripping portion (16) , power operated means (32,64) being interposed between these elements for effecting such displacement or pivot¬ ing, and that the gripping portion (16) is provided with a level sensor (36,68), which is operatively connected with said power operated means in a manner such that the power operated means will be actuated in response to an occurring slanting of the gripping portion so as to effect mutual displacement or pivoting between the grip¬ ping portion and the carrier member, until the gripping member by the associated power driven, relative movement of the suspension point has been brought into a freely suspended, horizontal position. 2. A lifting device according to claim 2, charac¬ terized in that the carrier member (54) is mounted per¬ manently upstanding on the gripping portion (16) , with a foot portion (56) secured in a displaceable manner to guiding means (58) on the gripping portion and with driving means such as a screw spindle or a working cylinder (64) arranged for controlled displacement of the carrier member towards the balanced position. 3. A lifting device according to claim 1, charac¬ terized in that it is prebalanced to assume the position in which the gripping portion (16) is projecting for introduction into the plate rack. 4. A lifting device according to claim 1, charac¬ terized in that the carrier member (20) is broader than the gripping portion (16) . 5. A lifting device according to claim 1, charac¬ terized in that the carrier member is a narrow, rod shaped member (54) , which projects upwardly sufficient¬ ly, e.g. through 1/2 m or more, to be operable to engage the front edge of an overlying rack shelf or of plate members resting thereon, when used for carrying out a plate member from an underlying rack shelf. 6. A lifting device according to claim 1, charac¬ terized in that it constitutes a part of a local trans¬ port system, e.g. also comprising a swivel crane , pro¬ vided between a receiver position and a plate rack de¬ dicated thereto.

Inventors: JENSEN ANTON BRANDI, JENSEN, ANTON, BRANDI
Applicants: JENSEN ANTON BRANDI, JENSEN, ANTON, BRANDI
Application year: 1991
Main classification: B66C1
IPC codes: B66C1