Gripper device and hoisting device for a trash rake cleaner, trash rake cleaner and method therefor

Abstract

A gripper device comprises a gripper with a gripper arm rotatable around a rotation axis such that the gripper is movable between an open end position and a closed end position, and a hoisting device connected to the gripper and comprising a first cable and a second cable which are each connected with their one outer end to the gripper and are each connected with their other outer end to respectively a first and second hoisting means for raising and lowering the gripper with the cables, wherein each hoisting means is, driven by a separate drive, wherein a controller transmits the same control signal to both drives for the purpose of raising or lowering the gripper, and each drive comprises a motor with internal slippage or a slippage coupling so that synchronous running of the hoisting means is automatically realized.

Claims

1. A gripper device for a trash rake cleaner, comprising: a gripper with a gripper arm rotatable around a rotation axis such that the gripper is movable between an open end position and a closed end position; and a hoisting device connected to the gripper and comprising a first cable and a second cable which are each connected with a corresponding first outer end to the gripper and are each connected with a corresponding second outer end to respectively a first and second hoisting means for raising and lowering the gripper with the cables, wherein the first cable is attached to the gripper arm at a position of a first point of engagement and the second cable is attached to the gripper arm at a position of a second point of engagement, wherein the points of engagement are provided on either side of the rotation axis such that upward movement of the first cable relative to the second cable carries the gripper to the open end position and upward movement of the second cable relative to the first cable carries the gripper to the closed end position, wherein a first tensioning force in the first cable produces a first moment arm relative to the rotation axis, and a second tensioning force in the second cable produces a second moment arm relative to the rotation axis, the first moment arm having a greater length than the second moment arm when the gripper is in the open end position, and the first moment arm having a shorter length than the second moment arm when the gripper is in the closed end position, characterized in that the first hoisting means is driven by a first drive, and the second hoisting means is driven by a second drive that is different from the first drive, the gripper device further comprising a controller connected to the drives for controlling the drives by transmitting a control signal with the controller, wherein the controller has a hoisting mode in which the controller is configured to transmit the same hoisting control signal to both drives, and in response to receiving the hoisting control signal, both drives act at the same time to raise or lower the gripper, and wherein the controller has a gripper mode in which the controller is configured to transmit, to one of the drives and not to the other of the drives, a gripper control signal, and in response to receiving the gripper control signal, the one drive opens or closes the gripper while the other drive remains inactive, the controller comprising a switch for switching between the hoisting mode and the gripper mode, the first drive comprising a first motor, the second drive comprising a second motor that is different from the first motor, the first and second motors configured to generate slippage in response to a difference in forces between the first and second cables coupled to the first and second motors, respectively, and to restore an equilibrium of forces between the first and second cables.

2. The gripper device as claimed in claim 1, wherein the drives are suitable to each bear at least 50% of a combined load.

3. The gripper device as claimed in claim 1, wherein the hoisting device further comprises a slippage coupling.

4. The gripper device as claimed in claim 1, wherein the gripper is mounted on a frame which is also provided with one or more redirecting means for redirecting the cables, wherein each cable is guided from the respective hoisting means along the one or more redirecting means to the gripper arm.

5. The gripper device as claimed in claim 1, wherein the gripper comprises at least one stop for bounding the movement of the gripper arm.

6. The gripper device as claimed in claim 1, wherein the rotation axis is provided outside a vertical plane midway between the cables.

7. The gripper device as claimed in claim 1, wherein the distance from the rotation axis to the first point of engagement differs from the distance from the rotation axis to the second point of engagement.

8. The gripper device as claimed in claim 1, wherein the rotation axis is arranged above a line connecting the first point of engagement to the second point of engagement.

9. The gripper device as claimed in claim 1, wherein each hoisting means comprises a drum, and wherein the drums are arranged above or next to one another.

10. The gripper device as claimed in claim 1, wherein each hoisting means comprises a drum of the same diameter.

11. The gripper device as claimed in claim 1, wherein the cables have a length of at least 20 meters.

12. A gripper device for a trash rake cleaner, comprising a gripper with a gripper arm which is rotatable around a rotation axis such that the gripper is movable between an open end position and a closed end position; a hoisting device connected to the gripper and comprising a first hoisting means, a second hoisting means and a cable, the cable comprising a first cable part which comprises a first outer end of the cable and a second cable part which comprises a second outer end of the cable, wherein the first outer end is connected to the first hoisting means and the second outer end is connected to the second hoisting means; and a redirecting means which is connected fixedly to the rotation axis and around which the cable extends for the purpose of raising and lowering the gripper arm by simultaneously respectively hoisting and lowering the first cable part and the second cable part, carrying the gripper arm to the open end position by hoisting the first cable part relative to the second cable part and carrying the gripper arm to the closed end position by hoisting the second cable part relative to the first cable part, wherein a first tensioning force in the first cable part produces a first moment arm relative to the rotation axis, and a second tensioning force in the second cable part produces a second moment arm relative to the rotation axis, the first moment arm having a greater length than the second moment arm when the gripper is in the open end position, and the first moment arm having a shorter length than the second moment arm when the gripper is in the closed end position.

13. The gripper device as claimed in claim 12, wherein the gripper arm in the open end position is rotated through more than 90 degrees relative to the closed end position.

14. The gripper device as claimed in claim 12, wherein the redirecting means has a plurality of substantially straight sides, wherein in any case two sides have an unequal length.

15. A hoisting device for a trash rake cleaner, comprising a first cable and a second cable which are each connected with a corresponding first outer end to a load carrier and which are each connected with a corresponding second outer end to respectively a first and second hoisting means for the purpose of raising and lowering the load carrier with the cables, wherein the first hoisting means is driven by a first drive, and the second hoisting means is driven by a second drive that is different from the first drive, the hoisting device further comprising one or two variable frequency drive controllers connected to the drives for controlling the drives by transmitting a control signal with the controller, wherein the controller has a hoisting mode in which the controller is configured to send the same hoisting control signal to both drives, and in response to receiving the hoisting control signal, both drives act at the same time to raise or lower the load carrier, the first drive comprising a first motor, the second drive comprising a second motor that is different from the first motor, the first and second motors configured to generate slippage in response to a difference in forces between the first and second cables coupled to the first and second motors, respectively, and to restore an equilibrium of forces between the first and second cables during the hoisting mode.

16. A trash rake cleaner comprising the gripper device as claimed in claim 1.

17. A trash rake cleaner comprising the gripper device as claimed in claim 12.

18. A trash rake cleaner comprising the hoisting device as claimed in claim 15.

19. A method for raising and lowering, and opening and closing a gripper for a trash rake cleaner as claimed in claim 1, comprising: rotating the gripper arm around the rotation axis for the purpose of opening the gripper by moving the first cable upward relative to the second cable; rotating the gripper arm around the rotation axis for the purpose of closing the gripper by moving the first cable downward relative to the second cable; raising the gripper by moving both cables upward; and lowering the gripper by moving both cables downward.

Description

(1) Further advantages, features and details of the invention are elucidated on the basis of preferred embodiments thereof, wherein reference is made to the accompanying figures.

(2) FIG. 1 is a perspective view of the gripper device according to the invention;

(3) FIG. 2 is a side view of the device of FIG. 1;

(4) FIG. 3 is a perspective view of the gripper arm of the device;

(5) FIG. 4A is a side view of the gripper device in the closed end position;

(6) FIG. 4B is a side view of the gripper device in the opened end position;

(7) FIGS. 5A-5C show a block diagram of the control of the device according to FIGS. 1-4;

(8) FIG. 6 shows an optional mechanism for detecting a slack cable;

(9) FIG. 7 is a perspective view of an alternative gripper device according to the invention;

(10) FIG. 8 is a second perspective view of the alternative gripper device;

(11) FIG. 9 is a side view of the alternative gripper device; and

(12) FIGS. 10-12 are side views of the alternative gripper device in an open, a semi-open and a closed state.

(13) Gripper device 2 (FIG. 1) comprises hoisting device 4 and gripper 6. Hoisting device 4 comprises asynchronous electric motors 8 (FIGS. 1 and 2) which drive drums 10 in rotation. First cables 12 run over drums 10. Hoisting device 4 further comprises two electric motors 14 of the same type as motors 8. Motors 14 drive drums 16 for the purpose of hoisting or lowering cables 18.

(14) Gripper 6 comprises a movable gripper arm 20 and a fixed gripper arm 22. Movable gripper arm 20 comprises a tilting arm 29 with an opening 24 (FIG. 3) for receiving shaft 25 so that gripper arm 20 can rotate around this shaft. Also provided in tilting arm 29 are openings 26 and 28 to which respective cables 12 and 18 are attached. The distance from opening 26 to opening 24 for the rotation axis is d1, the distance from opening 28 to opening 24 is d2. Gripper arm 20 is provided with teeth 30 at a mutual distance such that they fit between the bars of a trash rake for cleaning.

(15) The gripper comprises a frame 32 (FIGS. 4A, 4B) relative to which the gripper arm 20 can rotate around its rotation axis 25. Provided on the upper side of frame 32 are sheaves 34 which redirect cables 12, 18. The parts of cables 12, 18 located above frame 32 hereby extend substantially vertically in the direction of hoisting means 4, while the cable parts between sheaves 34 and points of engagement 26, 28 lie at an angle relative to the vertical direction. This angle depends only on the position of the gripper arm relative to the frame and not on the height position of the gripper arm relative to the hoisting means. In the shown embodiment gripper arm 20 is mounted on frame 32 with its rotation axis outside the centre line V running midway between cables 12 and cables 18.

(16) As shown in the figures, the distance between the cables is smaller close to redirecting rollers 34 than the distance between points of engagement 26, 28 of the cables on tilting arm 29.

(17) In the closed end position (FIG. 4A) the moment arm R.sub.1 of the tensioning force on cables 18 is greater than the moment arm R.sub.2 of the tensioning force on cables 12. In the shown embodiment the ratio R.sub.1:R.sub.2 is 3:2. There is hereby a net moment of force on gripper arm 20 which holds the teeth 30 against fixed gripper arm 22. Girder 38 moreover presses against stop 40 so that the force with which the gripper is pressed shut is partially absorbed by girder 38 and stop 40. If during hoisting or lowering a greater force is exerted on cable 18 than on cable 12, the moment of force which presses the gripper arm shut is then increased. If a (slightly) greater force is exerted on cable 12 than on cable 18, this difference in forces will then be compensated by the difference in length of the moment arm on either side of the rotation axis. The gripper arm therefore always remains closed. Owing to the heavier load the corresponding motor 8 will generate slippage so that it will begin to run more slowly and the equilibrium of forces will be restored.

(18) In the opened end position (FIG. 4B) the moment arm R.sub.2 on the side of cable 12 is greater than the moment arm R.sub.1 on the side of cable 18. In the shown embodiment the ratio R.sub.1:R.sub.2 is 2:3. This results in a net moment of force which holds gripper arm 20 in the opened end position. A girder arranged on tilting arm 29 is pressed here against a stop 36 of frame 32.

(19) When during raising or lowering of gripper arm 20 a greater force is exerted on cable 12 and on cable 18, this will then increase the moment of force so that the gripper arm is held in its open end position. If a greater force is exerted on cable 18 than on cable 12, this difference will then be compensated by the difference in the length of the corresponding moment arm. Before this difference in moment arm can be overcome, the equilibrium of forces will be restored by the slippage in electric motor 14 or a slippage coupling arranged here.

(20) The control of gripper device 2 comprises a frequency control 36 (FIGS. 5A-5C). For raising or lowering of the gripper (FIG. 5A) the frequency control is operatively connected to motors 8 and motors 14. The motors each receive the same control signal from frequency control 36.

(21) The controller is switchable to a mode in which only motor 14 receives the control signal (FIG. 5B). Only cable 18 is hereby hoisted or payed out, whereby the gripper respectively closes or opens. Additionally or alternatively, a switching position is provided in which a control signal is transmitted only to motor 8 (FIG. 5C). Only cable 12 is hoisted or payed out as a result, whereby the gripper respectively opens or closes.

(22) An example of the control of device 2 for cleaning a trash rake will be described hereinbelow. Gripper 6 is initially situated a certain distance above the trash rake with the gripper arm in the opened end position. The controller is switched to the mode as according to FIG. 5A and frequency control 36 generates a control signal so that the two pairs of motors 8, 14 cause the drums to rotate so that gripper 6 is lowered. When gripper 6 has moved down to the trash rake for cleaning, teeth 30 protrude through the bars of the trash rake. Gripper 6 is then closed. For this purpose the controller is switched to the mode according to FIG. 5C in which motors 14 receive a control signal to hoist the cable 18. After closing, the controller is switched to the mode according to FIG. 5A and gripper 6 is raised. Should an unequal distribution of the load occur here, the slippage in motors 8, 14 will then prevent non-synchronous running thereof. Because the moment arm holding the gripper arm 20 pressed against stop 22 is greater than the moment arm for opening thereof, differences in forces can be compensated to a certain extent without the gripper 6 opening here.

(23) The gripper device is preferably situated on a mobile carriage or other displaceable construction so that the whole gripper can be displaced to a waste collection location in order to there unload the scooped-up material by opening the gripper.

(24) Gripper device 2 optionally comprises a detection system 40 for detection of a slack cable (FIG. 6). Detection system 40 comprises two redirecting rollers 42, 44 along which cables 18 and 12 are guided. When cable 12 is tensioned by the presence of weight W.sub.1, it exerts a force F.sub.1 on redirecting roller 44 in horizontal direction. This force can be measured with a first sensor (not shown). Weight W.sub.2 similarly provides for a tensioning force in cable 18, whereby a horizontal force F.sub.2 is exerted on redirecting roller 42 by cable 18. A second sensor is provided here for measuring the force. On the basis of the forces measured by the sensors a controller of gripper device 2 can activate an alarm, switch off motors 8 or activate another safety system. The second sensor for instance measures a sudden increase in force, which means that cable 12 (or one of the group of cables 12) has snapped. In that case the first sensor will measure a decrease in force. One sensor can be provided instead of sensors on either side.

(25) An alternative gripper device comprises gripper 106 (FIGS. 7 and 8). Gripper 106 comprises a movable gripper arm 120 and a fixed gripper arm 122. Movable gripper arm 120 can rotate around shaft 125. Gripper 106 further comprises redirecting means 127 which are fixedly connected to shaft 125. The hoisting means of gripper 106 correspond largely to the hoisting means of gripper 6 of FIG. 1. In gripper 106 however a cable loop leading round redirecting means 127 is provided instead of engaging points on either side of rotation axis 125. A first cable parts 112, which comprises the one outer end of the cable, is attached to a first drum. A second cable part 118, which comprises the other outer end of the cable, is attached to a second run.

(26) Gripper 106 comprises a frame 132. Redirecting rollers 134 are provided (FIGS. 8 and 9) on the upper part of frame 132 for the purpose of guiding cable parts 112, 118 in the direction of redirecting means 127.

(27) In the shown embodiment redirecting means 127 takes the form of an isosceles triangle, the corner points which are rounded. The redirecting means is mounted on the shaft close to one of its equal angles. It is noted that other shapes and/or mounting points are also possible according to the invention. In the shown embodiment the base of the isosceles triangle is shorter than the two sides of equal length.

(28) In an opened end position movable gripper arm 120 and fixed gripper arm 122 are situated at an angle of about 180 degrees relative to each other (FIG. 10). The short side of the triangular redirecting means 127 is then located on the underside so that the loop of cable 112, 118 runs over this short side. The length of moment arm R1 for opening gripper arm 120 is clearly greater here than the length of moment arm R2 for closing the gripper arm. Gripper 106 comprises a stop (not shown) for preventing the gripper arm rotating even further as a result of the force in cable 112. The position of FIG. 10 is hereby an end position of gripper 106.

(29) FIG. 11 shows a position of gripper arm 120 between the opened end position and the closed end position. In this position a long side of triangular redirecting means 127 is situated on the underside so that cable loop 112, 118 engages on this long side. In this situation the length of moment arm R1 for opening is also greater than the length of moment arm R2 for closing. With simultaneous operation of the hoisting means the gripper arm will thus move from the intermediate position of FIG. 11 to the end position of FIG. 10.

(30) If however the gripper is brought into the closed end position (FIG. 12) by lowering of cable part 112 relative to cable part 118, the moment arm R1 is then smaller than the moment arm R2. This is caused by tilting of triangular redirecting means 127, the short side of which is now situated on the upper side. The cable loop therefore engages on the rounded top of triangle 127. When gripper arm 120 is thus in the closed end position, with simultaneous operation of the motors the gripper arm 120 will then tend to remain in the closed position.

(31) The invention is by no means limited to the above described preferred embodiments thereof. The rights sought are defined by the following claims, within the scope of which many modifications can be envisaged. The invention can thus find application with gripper arms which are moved vertically, but also with gripper arms which operate to some extent at an angle.