RIBBON ACTUATED ELEVATOR

Abstract: A lifting device for a conveyor system having multiple sections, which deliver work pieces to tool stations. The elevator has flat narrow ribbons (28A, 28B) for providing vertical movement to the work pieces. The flat narrow ribbons may be perforated to provide a timing belt. The ribbons have parallel faces or are positioned parallel to each other with respect to their flat surfaces. The elevator or hoist includes an upper carriage (10) and a spaced lower end effector (22) for carrying the workpiece, with the ribbons extending diagonally, each at one leg of a loop thereof between the upper carriage and the end effector and forming a triangle and having a pulley (42) at its apex and arranged to roll the pulley at the apex if the ribbon were to begin to swing whereby to prevent such swinging movement. The ribbons are looped around pulleys (42A, 42B) on top of the end effector, at the apex of a ribbon triangle, which pulleys then are damped using magnetic hysteresis. The ribbon take up (38) is tensioned with a continually rotating magnetic hysteresis drum (36).

Description: RIBBON ACTUATED ELEVATOR CROSS-REFERENCE TO RELATED APPLICATIONS Priority is claimed from the U.S. Provisional Application, entitled, RIBBON ACTUATED ELEVATOR, filed on August 12, 1998, Serial No. 60/096,274. FIELD OF THE INVENTION Background of the Invention In the process of manufacturing products in clean environments, it is often the case that work-in-process transports are ceiling-mounted. Such transports can comprise monorail guided vehicles or conveyors. These function as transport means between the processing tools or storage devices. Since the processing tools and storage devices have work entry ports at different elevations from the floor, it becomes necessary to interface these ports to the transport devices for the purpose of transferring work-in-process between them. The transfer process is usually a combination of horizontal and vertical motions, whereby the transfer device, or interface device carries the work-in-process from transport to tool or vice versa. A desirable feature of these interface devices is that they be ceiling mounted (to save floor space), and occupy an area of minimum footprint when projected on the floor. It is also desirable that these devices do not permanently block areas of the process tools or storage bins that normally are called their face plane, and may hold operator interface, or control devices. Generalized industry solutions currently embody these features by combining transport vehicles with a hoist device into one and the same equipment. The hoist device runs on monorails and carries in its bottom gripper (end effector) the work-in-process. When such a vehicle is stopped at a tool or storage device it is accurately positioned over a port to such devices, comprising a horizontally mounted adapter, onto which the work-in-process needs to be lowered accurately. Such a hoist device is complex of necessity since it must position itself automatically over many such port adapters in sequence, each being at an arbitrary location. Summary of the Invention It is therefore a general object of the present invention to provide a simple and rapid means for raising and lowering the work-in-process. Another object is to provide a device of the type described in which a plurality of ribbons are used to raise and lower the end effector or bottom gripper. It is a further object of the present invention to provide a device of the type described in which magnetic hysteresis damped pulleys are used to reduce the end effector sway induced by the rotation of the pulley. It is an additional object of the present invention to provided a hysteresis tensioning wheel for winding up the ribbon which raises and lowers the bottom gripper. It is yet a further object of the present invention to provide a means for assuring accurate placement of the bottom gripper with respect to the work holder, and a homing means is used for this purpose. It is still a further object of the present invention to provide for high tool utilization, a self buffered transport, i.e., transport of work in process lots takes place during the processing of other lots and the transport system is (a) buffered and (b) a storage system at the same time. To carry out this object the transport system cannot be both (a) tool interface (hoist) and (b) transport (because then hoist-vehicles would accumulate on the line, causing line jams and incur high costs with the high number of them; each is complex and expensive). Therefore, the principle of dedicated hoists as provided by the present invention together with the self buffering conveyor comprise an economical solution for equipment cost and process efficiency. In contrast to the prior art, the present invention limits the service number of tools and their port devices to a relatively few, making it simpler to position over the port devices of the tools before lowering its work load. The main difference conceptually being that the current invention is used predominantly to interface a transport system to the tool port devices and therefore it does not function as a primary transport device. This makes it less costly to manufacture. Other differences from current devices are in the method of accomplishing a relatively stable, smooth and accurate positioning of the work in process onto the tool port devices. Generally, other designs utilize wire and pulley means to lower the work load from the ceiling track (similar to a crane), or may utilize wide ribbons that are positioned at angles to each other. In each case, however, active sensing and feedback to the motorized lowering or raising procedure is employed to accomplish accurate positioning onto the tool interface device. The advantages and benefits of the present invention are: 1. For high tool utilization a self buffered transport is desirable (i.e., transport of work in process lots takes place during the processing of other lots; the transport system is (a) buffered, (b) a storage system at the same time); 2. To maintain the above principle the transport system cannot be both (a) tool interface (hoist), (b) transport (because then hoist- vehicles would accumulate on the line, causing line jams and incur high costs with the large number of them; each is complex and expensive); and 3. Therefore: The principle of dedicated hoists (as in this invention) together with the self buffering conveyor comprise a most economical solution for equipment cost and process efficiency. Description of the Drawings The means by which the foregoing objects and features of invention are achieved are pointed out in the claims forming the concluding portion of the specification. The invention, both as to its organization and manner of operation, may be further understood by reference to the following description taken in connection with the following drawings. FIG. 1 is an isometric view of the carriage, end effector and ribbons. FIG. 2 is a schematic view showing the carriage moving toward the conveyor. FIG. 3 is a schematic view showing the carriage directly above the conveyor. FIG. 4 is a schematic view showing the carriage moving away from the conveyor toward the work station and carrying the work piece. FIG. 5 is a schematic view showing the work piece lowered into the tool stations FIG. 6 is a schematic view showing the carriage out of the way with the work piece at the tool station. FIG. 7 is a side view of the arrangement of the present invention showing the end effector in a lowered position. FIG. 8 is an end view of the arrangement shown in FIG. 7. FIG. 9 is a schematic side view of the end effector showing one of the ribbons on one side of the effector. FIG. 10 is a schematic side view of the end effector showing the other of the ribbons on the same side of the effector as FIG. 9. FIG. 10A is a schematic side view of the spooling wheel. FIG. 11 is a schematic side view of the arrangement showing both ribbons on one side and the triangles created by each ribbon. FIG. 12 is a schematic partial sectional view of the end effector. FIG. 13 is an isometric view of the bottom of the end effector showing the plate of the work carrier. FIG. 14 is an isometric view of the plate of the work carrier and a homing projection. FIG. 15 is a top view of the structure shown in FIG. 14. FIG. 16 is a view of the ribbon showing the holes in it. Description of the Preferred Embodiments The current invention employs narrow flat ribbons and pulleys, aligned parallel with each other and the ribbons running straight and diagonally in a vertical plane. The parallel ribbons provide stability in the direction parallel with their plane, while in the direction orthogonal to that, the system is damped by the use of magnetic hysteresis. Such a device can function as a damper against swing in the direction parallel to the tool face since in that direction the end effector is suspended by a ribbon where two ends of a ribbon (near the ceiling) and the hysteresis damped pulley on the end effector (near the bottom) form a triangle. The two points of the triangle at the top being fixed with the apex of the triangle (near the bottom) would be allowed to swing and impart a rolling motion to the hysteresis pulley in the process. The layout is described below. As shown in FIG. 1 there is a motorized carriage 10 having an end effector or bottom gripper 22 suspended therefrom by ribbons or belts 28A, 28B. There are four belts which support and also raise and lower the bottom gripper 22. The belts include two belts 28A, one on each side of the end effector 22, and two belts 28B, one on each side of the end effector. This is shown in FIGS. 1 and 8, and will be described in further detail below. The belts 28A, 28B may have timing openings therein as shown in FIG. 16 As shown in FIGS. 2-6, the motorized carriage 10 at ceiling level 12 runs on a relatively short set of two rails 14 in the direction parallel with the tool face plane. This movement allows the device to be positioned above the transport 18 (a conveyor in most cases - reference is made to the Middlesex patents, such as U.S. Pat. No. 4,793,262), on which the work-in-process 24 is brought to the tool. The device then lowers its end effector 22 to pick up the work-in-process 24 from the conveyor 18. After pick up, the device moves parallel with the tool face plane until it is directly over the tool interface device 26. At that point it stops. Either while moving, or after it stopped, the work-in-process 24 is lowered onto the tool interface device 26 via the unspooling of the two sets of ribbons 28A and 28B in the vertical direction. FIG. 2 shows the carriage moving toward the conveyor. In FIG. 3 the carriage is in position directly above the conveyor. The carriage then moves away from the conveyor toward the work station and carrying the work piece (FIG. 4). In FIG. 5 the work piece is lowered into the tool station. FIG. 6 shows the carriage away from the work station with the work piece at the tool station. There are two ribbons 28A, one on each side of the end effector, and two ribbons 28B, one at each end of the end effector so that, as shown in isometric FIG. 1, the end effector is supported at four locations by the ribbons. As shown in FIGS. 7, 8 and 9-11, the ribbons 28A each include a fixed end 30A (onto the carriage device) and a spooling end 32A. Each of the ribbons 28B includes a fixed end 30B (onto the carriage device) and a spooling end 32B. The spooling ends 32A and 32B are driven vertically by an electronically controlled motor (not shown) having a shaft 34 and four hysteresis tensioning wheels 36 (only one being shown), one for each of the ribbons 28. Thus, there is one hysteresis tensioning wheel 36 for each of the four ribbons. The ribbons 28A and 28B may have perforations 30 to allow accurate positioning via spooling wheels 38 ( of which there are also four, with only one being shown) with cogs 40 in it as shown in FIG. 10A. The ribbons 28A and 28B trace a path starting with their fixed ends 30A and 30B, going downwardly and looping around magnetic hysteresis damped pulleys 42A and 42B, respectively, located on top of the end effector 22. There are idler wheels 43. Thereafter, the ribbons 28 return upwardly to the spooling wheels 38. After the spooling wheels 38, the ribbons 28 are wound onto the pre-tensioned wheels 36, taking up the slack. Tensioning is done with the magnetic hysteresis wheels 36 that are continually driven by the electric motor. The hysteresis tensioning devices can be made, for example, similar to the structure disclosed in U.S. Patent No. 4,793,262, which disclosure is hereby incorporated by reference. The bottom of the end effector 22 holds the work-in-process 24, while the top carriage holds the spools 38 for the return of the ribbons to the top. With this arrangement the spooling motor in the top carriage device 10 lowers the end effector 22 and the attached work-in-process 24 onto the tool interface. The end effector 22 is limited in movement towards the tool face due to the stiffness of the ribbons in that direction. At the same time, it is damped in the orthogonal direction via magnetic hysteresis devices included in the hubs of the spools 42A and 42B on top of the end effector 22. [These can also be made similar to the devices in the '262 patent.] Any sway of the end effector will induce rotation of the pulleys or wheels 42. Although some minimal swing of the end effector 22 is allowed, it is well damped in both directions. Additional stiffness of the system is provided in the direction of the carriage travel via the diagonal return of the ribbons 28. Further stiffness of the system may be accomplished by forming the ribbons 28 into an arched cross section as in a measuring tape. This would provide a curved cross section to the ribbons. The end effector 22 of the device is completely passive in the means of picking a work-in-process 24 from the transport or the tool interface 26. The work in progress is carried by a work piece holder having a top plate 44, provided with homing notches 48 so that the position of the plate is accurate with respect to the end effector 22 each time the end effector picks up a work piece. The bottom of the end effector has two rails or ledges 46 which support the ends of the plate when the work piece is being moved. However, when a work piece is to be picked up, it is already supported by the plate 44. The end effector 22 is placed at an elevation so that it can move to be directly above the work piece and between the bottom of the end effector 22 and the ledges 46, as indicated in FIG. 13. Then, the end effector 22 is raised slightly and the suitably shaped homing pieces 50 guide the grooves or notches into proper position. The homing pieces 50 have tapered ends 52 which have inclined sides 54 so that when this action takes place the plate is guided onto the homing pieces and thus accurately positioned. Thus, as the end effector 22 is raised gradually it is guided into two required notches 48 of the work-in-process carrier via three dimensionally wedge shaped homing pieces 50 arranged to be 180 degrees opposed to each other. It will now be apparent to those skilled in the art that other embodiments, improvements, details and uses can be made consistent with the letter and spirit of the foregoing disclosure and within the scope of this patent, which is limited only by the following claims, construed in accordance with the patent law, including the doctrine of equivalents.

Claims: CLAIMS 1. A lifting device for a conveyor system having multiple sections, which deliver work pieces to tool stations, comprising: a vertically and horizontally positioned vertical elevator for transferring work pieces from conveyor system sections to tool stations, said elevator having flat narrow ribbons for providing vertical movement to the work pieces. 2. A device as defined in claim 1 wherein said flat narrow ribbons are perforated to provide a timing belt. 3. A device as defined in claim 1 wherein the ribbons have parallel faces or are positioned parallel to each other with respect to their flat surfaces. 4. A device as defined in claim 1, further comprising an upper carriage and a spaced lower end effector for carrying the workpiece, said ribbons extending diagonally, each at one leg of a loop thereof between the upper carriage and the end effector and forming a triangle and having a pulley at its apex and arranged to roll the pulley at the apex if the ribbon were to begin to swing whereby to prevent such swinging movement. 5. A device as defined in claim 4 wherein the ribbons are looped around pulleys on top of the end effector, at the apex of a ribbon triangle, which pulleys then are damped using magnetic hysteresis. 6. A device as defined in claim 4 where the ribbon take up is tensioned with a continually rotating magnetic hysteresis drum. 7. The interface device as in claim 4 where the end effector is passive and possesses the three dimensionally shaped triangle pieces for leading the pickup move into position. 8. The device as in claim 4 where the ribbon actuators are shaped into having an arched cross section. 9. A conveying and tool station arrangement, comprising: a conveyor system arranged to be hung from a ceiling for delivering work pieces to tool stations; and a vertically and horizontally positioned vertical elevator for transferring work pieces from conveyor system sections to tool stations, said elevator having flat narrow ribbons for providing vertical movement to the work pieces; said elevator incluidng an upper carriage and a spaced lower end effector for carrying the workpiece, said ribbons extending diagonally, each at one leg of a loop thereof between the upper carriage and the end effector and forming a triangle and having means to prevent swinging of the ribbon; and said elevator acting as a self buffering transport so that the transport system is buffered and acts as a storage system at the same time, whereby the elevators are dedicated to only act as hoists.

Inventors: HORN GEORGE W, HORN, GEORGE, W.
Applicants: HORN GEORGE W, MIDDLESEX GENERAL IND INC, HORN, GEORGE, W., MIDDLESEX GENERAL INDUSTRIES, INC.
Application year: 1999
Main classification: B66C13
IPC codes: B66C13, B66D1