Patent Publication Number: US-6988715-B2

Title: Hoisting device

Description:
BACKGROUND OF THE INVENTION 
   The invention concerns a hoisting device with a drive unit consisting of a motor and a transmission, a drive shaft which can be driven by the drive unit, with a drive flange which can be secured to it, and a cable drum which can be connected to the drive flange, wherein the torque of the drive shaft can be transmitted to the cable drum across a coupling. 
   Hoisting devices configured as a cable string basically comprise cylindrical cable drums, which are mounted so as to turn in a frame. The cable drum is driven by means of a gear motor, the output shaft of the transmission being coupled torsion-free to the cable drum. In order to equalize the manufacturing tolerances and alignment errors of the cable drum, which is generally outfitted with a so-called “three-point bearing”, such as might lead to strains in the drive system, it is known from practice how to arrange a coupling between the output shaft and the cable drum in a manner that can take up these alignment errors. 
   In the so-called Zapex coupling, the coupling is fashioned as a toothed coupling, which comprises a pinion joined torsion-free to the output shaft and a toothed rim meshing with this pinion and secured to the drive flange of the cable drum. 
   Furthermore, the so-called TGL coupling is known, in which a flange secured torsion-free to the output shaft engages by one or more driving lugs with recesses in an end wall of the cable drum. 
   Both coupling mechanisms have become quite common in practice, although they have the drawback that they are relatively costly for mass-produced lifting mechanisms with relatively low drum torque and furthermore they cannot be used with small drum diameters, for space considerations owing to their size. 
   DE 298 16 675 U1 discloses a coupling for lifting mechanisms for transmitting the torque of a driven transmission shaft to a cable drum, with a coupling hub arranged at one end of the transmission shaft and with a coupling housing arranged on the coupling hub and enclosed by inner and outer covers. The coupling housing and the coupling hub are form-fitted together by circular gearings formed on the coupling housing and the coupling hub, and in the bores formed by the two circular gearings there are arranged barrel rollers to transmit the force. 
   SUMMARY OF THE INVENTION 
   Starting with this, the task of the invention is to furnish a hoisting device of the kind mentioned above with a coupling of simple and space-saving construction, ensuring a coupling of the cable drum to the drive shaft while equalizing the alignment errors. 
   The solution to this problem is characterized according to the invention in that the coupling segments extend outside the drive cams, essentially between the drive flange and the cable drum. 
   Due to the invented configuration of the coupling as coupling segments to be arranged in form-fitting manner and thereby transmitting the torque between the engaging structural parts, it is possible to configure the clutch with simple construction and cost benefits. 
   Furthermore, the possibility exists of arranging the clutch in various locations, namely, between the drive flange and the cable drum and/or between the drive shaft and the drive flange. 
   When arranging the coupling element between the drive flange and the cable drum, the drive shaft and the drive flange must then be joined together torsion-free, in order to be able to transmit the torque of the drive shaft via the coupling to the cable drum. 
   The torque transmission of the structural parts coupled together occurs, in one practical embodiment of the invention, in that the coupling element has drive cams pointing radially inward and outward on both sides, each of which engage with corresponding recesses in the two adjoining structural parts being coupled together for the torque transmission. 
   According to the invention, at least one coupling element forming the coupling is constructed to consist of individual coupling segments. The construction from individual coupling segments enables the equalization of manufacturing tolerances in a simple manner. 
   The coupling segments for the placement between the drive flange and the cable drum preferably have pieces forming bearing surfaces extending in two dimensions from the drive cams. In this way, it is possible to mount the cable drum onto the drive flange by means of the pieces of the coupling segments. 
   In one embodiment of the invention, the individual coupling segments extend around the drive cams on both sides, i.e., in the circumferential direction of the drive flange. 
   Advantageously, the individual coupling segments extend in a circular arc between the drive flange and the cable drum. 
   According to a first embodiment for the configuration of the coupling segments, individual coupling segments are joined together by elastic connectors, so that a single coupling segment is formed consisting of several coupling segments, which can be fabricated and assembled in an especially simple and economical manner. 
   A second embodiment for the configuration of the coupling segments proposes that individual coupling segments can be coupled together by means of molded-on projections and correspondingly fashioned seats. The projections and seats can be configured so as to enable either an interlocking coupling or also a pure form-fitting coupling of the individual coupling segments to each other. 
   In a third embodiment of the invention, the coupling element finally consists of individual coupling segments arranged at a distance from each other. 
   In order to assure a uniform transmission of torque, on the one hand, and reduce the mechanical loads on the individual coupling segments, on the other hand, the invention proposes that each coupling segment have drive cams pointing radially outward on both sides, which engage in corresponding recesses of the two adjoining structural parts being coupled together to transmit the torque. Advantageously, the drive cams are arranged on the coupling segments pointing radially outward and inward, directly opposite each other. 
   Since the drive cams essentially determining the torque transmission are subjected to intense shear stress, according to a preferred embodiment of the invention it is proposed that the drive cams consist at least partially of a harder material than the rest of the coupling element and preferably contain a shear-resistant core. 
   A length mismatch between the cable drum and the drive shaft can be equalized according to the invention in that the recesses to accommodate the drive cams of at least one of the structural parts being coupled together are configured to be larger, looking in the axial direction of the cable drum than the corresponding drive cams being accommodated. 
   Furthermore, in order to equalize an angle mismatch between the lengthwise axis of the cable drum and the drive shaft, the invention proposes that at least one bearing surface of the coupling element at one of the structural parts being coupled together and/or at least one bearing surface of a structural part being coupled at the coupling element be made convex or outwardly arched. 
   Finally, the invention proposes that the at least one coupling element consist at least partly of an elastic material, especially a plastic material. The elasticity of the material enables an additional equalization of possible stresses, and additional dampening properties can be achieved by an appropriate choice of material, in order to lessen the impact loading of the cable tension on the drive shaft. 
   Additional features and benefits of the invention will be evident from the corresponding drawing, which represents different sample embodiments of a hoisting device according to the invention, merely as examples. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a sectional view taken lengthwise through the construction of a hoisting device according to the invention; 
       FIG. 2   a  is a partial sectional view taken lengthwise through the coupling region of a hoisting device according to the invention; 
       FIG. 2   b  is a view of detail IIb of  FIG. 2   a,  but showing an alternative configuration; 
       FIG. 3  is a sectional view taken along line III—III of  FIG. 2 ; 
       FIG. 4  is a partial sectional view taken along line IV—IV of  FIG. 2 ; 
       FIG. 5   a  is a top view of a coupling element according to a first embodiment of the invention; 
       FIG. 5   b  is the same view as  FIG. 5   a,  but showing a second embodiment of a coupling element according to the invention; 
       FIG. 5   c  is the same view as  FIG. 5   a,  but showing a third embodiment of a coupling element according to the invention, and 
       FIG. 6  is a sectional view taken along line VI—VI of  FIG. 3 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  shows schematically the construction of a hoisting device configured as a cable pull. The hoisting device essentially comprises a drive unit  1 , consisting of a motor and a transmission, a drive shaft  2  which can be driven by the drive unit  1 , with drive flange  3  which can be secured to it, as well as a cable drum  4  which can be connected torsion-free to the drive flange  3 , on which the cable  5 , shown only schematically, can be wound up or paid out. 
   As is evident from  FIG. 1 , the cable drum  4  is outfitted with a so-called “three-point bearing”, in which the cable drum  4  is mounted by means of two bearings  6   a ,  6   b  at the ends of the drive shaft  2  and one bearing  7  at a drum journal  8  opposite the drive shaft  2 . 
   Since, in practice, these bearings  6   a ,  6   b  and  7  cannot be arranged in exact alignment due to manufacturing and setup tolerances and deformations under load, secondary bearing stresses occur in the mounted parts, namely, in the drive shaft  2  and/or in the drive flange  3  of the cable drum  4 . In order to avoid these unwanted and hard to predict stresses, which arise in addition to a payload acting as the cable tension force S, a coupling is provided, which transmits the torque of the drive shaft  2  to the cable drum  4  with angular movement and length equalization, as represented in  FIG. 2   a.    
   In the embodiment represented in  FIG. 2   a , the coupling is arranged between the drive flange  3  and the cable drum  4 , while the drive flange  3  for its part is joined torsion-free to the drive shaft  2 . Of course, it is also possible to arrange the coupling between drive shaft  2  and the drive flange  3 , but in this case it is necessary for the drive flange  3  to be joined torsion-free to the cable drum  4 . As a third embodiment of the coupling, the possibility exists of accomplishing the torque transmission both from the drive shaft  2  to the drive flange  3  and from the drive flange  3  to the cable drum  4  by means of a single coupling. 
   As is evident from the section view of  FIG. 3 , the coupling arranged between the drive flange  3  and the cable drum  4  consists of a coupling element  9  having several individual coupling segments  9   a,  which is arranged essentially form-fitting between the two structural parts  3 ,  4  being coupled together. The precise construction of the coupling element  9  and the coupling segments  9   a  will be described hereafter with  FIGS. 5   a  through  5   c.    
     FIG. 3  shows, furthermore, that each coupling segment  9   a  of the coupling element  9  has drive cams  10  pointing radially inward and outward on both sides, which engage with corresponding recesses  11  of the drive flange  3  and the cable drum  4  in order to transmit the torque. In the sample embodiments depicted, the drive cams  10  are always arranged directly opposite each other on the coupling segments  9   a  and pointing radially inward and outward. Of course, it is also possible to arrange the drive cams  10  of both sides of a coupling segment  9   a  staggered from each other on a coupling segment  9   a.    
   The coupling elements  9   a  extend in a circular arc in the space between the drive shaft  3  and the cable drum  4 , and they broaden out two-dimensionally in the peripheral direction around the drive cams  10  on both sides, in order to form pieces  9   c  producing bearing surfaces  9   b , on which the cable drum  4  rests. 
   The pictures of  FIG. 5   a  through  5   c,  finally, show three embodiments for configuring the coupling elements  9  made from individual coupling segments  9   a . In the first embodiment shown in  FIG. 5   a , the coupling element  9  is fashioned almost as a single piece, while the individual coupling segments  9   a  are joined together by elastic connectors  12 . 
   In the second embodiment per  FIG. 5   b , each coupling segment  9   a  has molded-on projections  13  and seats  14  formed corresponding to the projections  13 , by which individual coupling segments  9   a  can be coupled together. While the sample embodiment depicted represents an interlocking coupling, the projections  13  and seats  14  can also be made rectangular, for example, so that they are not interlocking, but only engage with each other essentially by form fitting. 
   The coupling element  9  of the third embodiment represented in  FIG. 5   c  consists of individual coupling segments  9   a  arranged at a distance from each other. These three variants depicted enable a length adjustment between the individual drive cams  10  and the corresponding seats  11  and, thus, a uniform distribution of the cable tension force S among the individual coupling segments  9   a.    
   Since the coupling segments  9   a  are exposed to a strong shear strain in the region of the drive cams  10  transmitting the torque to the other part, it is advantageous to configure the drive cams  10  at least partly from a harder material than the rest of the coupling element  9 . 
   According to  FIG. 6 , for this purpose the drive cams  10  contain a shear-resistant core  10   a,  which can be made of metal, for example; the remaining coupling segment  9   a  is then made from plastic. Fundamentally, it is also possible to use castable metals, such as bronze alloys, for the coupling elements  9 . The shear-resistant core  10   a  can then be omitted. 
   These shear-resistant cores have the function of ensuring a secure torque transmission between the structural parts coupled together in event of failure of the drive cams  10 —due to abrasion, for example—until the defective coupling element  9  or coupling segment  9   a  is replaced. 
   In order to be able to equalize a length mismatch between the cable drum  4  and the drive flange  3 , the recesses  11  to accommodate the drive cams  10  of the coupling segments  9   a  are fashioned in the sample embodiment depicted as lengthwise grooves  11   a  and, thus, are larger in the axial direction of the cable drum  4  than the corresponding drive cams  10  being accommodated. A gap  15  arising as a result of this configuration is noticeable especially in  FIG. 2   a , while  FIG. 4  shows the configuration of a lengthwise groove  11   a.    
     FIGS. 2   a  and  2   b  show how an angle mismatch between the lengthwise axes of the cable drum  4  and the drive flange  3  and/or the drive shaft  2  can be equalized. For this, according to  FIG. 2   a , a bearing surface  9   b  of the coupling element  9  is formed convex and outwardly arched at a bearing surface  3   a  of the mating drive flange  3 . 
   In the alternative embodiment of  FIG. 2   b , the convex arching is formed at the bearing surface  3   a  of the drive flange  3 . The corresponding convex archings of the bearing surfaces are indicated by the radius of convexity R in  FIGS. 2   a  and  2   b.    
   A coupling fashioned in this way is distinguished by simple construction and it enables a good equalization of resulting manufacturing and setup tolerances with compact size. 
   Changes and modifications in the specifically described embodiments can be carried out without departing from the principles of the invention which is intended to be limited only by the scope of the appended claims, as interpreted according to the principles of patent law including the doctrine of equivalents.