Abstract:
The invention relates to lifting gear having a drive unit ( 2 ), a drive shaft ( 3 ), which has a drive flange ( 4 ) fixable thereon and can be driven by the drive unit ( 2 ), and a cable drum ( 5 ) that can be connected to the drive flange by means of a coupling, said coupling comprising at least one coupling element ( 10 ) engaging in a recess ( 11 ) in the drive flange ( 4 ) and in a hole ( 12 ) in the cable drum ( 5 ) to transmit torque. In order to equip a lifting gear having a drive unit comprising a motor and a gearbox with a coupling, which ensures simple assembly with a simple and space-saving design, according to the invention the coupling element ( 10 ) is movable and fixable radially from an assembly position into an operating position, in which the coupling element ( 10 ) connects the drive flange ( 4 ) to the cable drum ( 5 ) in a driveable manner.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority benefits of International Application No. PCT/EP2008/053193, filed on Mar. 18, 2008, and also of German Patent No. 10 2007 014 505.7, filed Mar. 27, 2007, which are hereby incorporated herein by reference in their entireties. 
     BACKGROUND OF THE INVENTION 
     The invention relates to a lifting gear having a drive unit, a drive shaft which can be driven by the drive unit and has a drive flange which can be fixed thereon, and a cable drum which can be connected to the drive flange via a coupling. 
     Lifting gears which are formed as cable pulls comprise a substantially cylindrical cable drum which is mounted in a rotatable manner in a frame. The cable drum is driven with the aid of a transmission motor, wherein the output shaft of the transmission is coupled in a rotationally fixed manner to the cable drum. In order to compensate for production tolerances, alignment errors and deformations of the cable drum generally equipped with a so-called “3-point bearing”, which can lead to warping in the drive, it is known in practice to dispose a coupling between the output shaft and the cable drum, which coupling can accommodate these alignment errors. 
     DE 298 16 675 U1 discloses a coupling for lifting units to transmit the moment of a driven transmission shaft to a cable drum, having a coupling hub which is disposed on one end of the transmission shaft, and a coupling housing which is closed by inner and outer covers and is disposed on the coupling hub. Disposed in the coupling housing and the coupling hub are cylindrical and oppositely disposed recesses, in which barrel rollers for the transmission of force from the coupling housing to the coupling hub are disposed in a positive-locking manner. 
     SUMMARY OF THE INVENTION 
     The present invention equips a lifting gear having a drive unit, which consists of a motor and a transmission, with a coupling which ensures simple assembly in a simple and space-saving construction. 
     In accordance with an aspect of the invention, in the case of a lifting gear having a drive unit, a drive shaft which can be driven by the drive unit and has a drive flange which can be fixed thereon, and a cable drum which can be connected to the drive flange via a coupling, wherein the coupling includes at least one coupling element which engages in each case into a recess in the drive flange and into a bore in the cable drum in order to transmit torque, a simple and space-saving construction and simple assembly are achieved by virtue of the fact that the coupling element can be moved radially from an assembly position and can be fixed in the operating position, in which the coupling element drivingly connects the drive flange and the cable drum together. This displacement movement of the coupling element permits a particularly simple positive-locking connection of the components which are to be coupled. The coupling is constructed in a particularly simple manner and is cost-effective. During assembly, the coupling element also renders it possible initially to connect the drive flange to the drive shaft and then to push the cable drum over the drive flange and to connect it at this site to the coupling element. The coupling element can be reached particularly easily from the outside and in the radial direction. The entire assembly procedure can thus be performed simply and cost-effectively. It is also readily possible to dismantle the cable drum by releasing the coupling elements. 
     A compact construction is achieved by virtue of the fact that in the assembly position the coupling element is located completely in the recess of the drive flange. 
     A particularly secure operating state and captive securing of the coupling element are provided by virtue of the fact that in the operating position the coupling element is held in the recess by the cable drum itself. In this case, in the operating position the shoulder lies against the inner surface of the cable drum. This is particularly important for accident-prevention in the case of lifting gears which are normally disposed above the operators. 
     In one embodiment the coupling element includes a drum-side, outer driving cam and a flange-side, inner driving cam which adjoins it, the outer driving cam has an outer diameter which is smaller than an outer diameter of the inner driving cam and the coupling element has a shoulder in the region of the transition between the inner driving cam and the outer driving cam. 
     The coupling element can be moved from the assembly position radially outwards into the operating position in a particularly convenient manner, if the coupling element is formed as a sleeve having a central and radially aligned channel, into which a screw for adjusting the sleeve can be screwed. The adjustment can thus be performed simply from the outside and in the radial direction, from which the coupling is easily accessible. Instead of the screw, it is also possible to use other securing elements. 
     A simple way of securing the coupling element in the operating position is achieved by virtue of the fact that in the operating position the screw is supported with its tip on a base of the recess of the drive flange, which recess is formed in the manner of a blind hole. 
     The installation size of the coupling is minimised by virtue of the fact that in the operating position the screw protrudes with its head only slightly, such as less than the cable guide or than the wall thickness of the cable drum from the surface of the cable drum. 
     A favourable and uniform transmission of torque is achieved by virtue of the fact that several, such as three, coupling elements are disposed along the periphery of the drive flange. Three coupling elements may be provided, whereby the number of components and also the costs can be minimised whilst at the same time achieving a reliable torque transmission. 
     These and other objects, advantages and features of this invention will become apparent upon review of the following specification in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side sectional view of a schematic construction of a lifting gear; 
         FIG. 2  is a sectional view of the coupling region of a lifting gear in accordance with the invention; and 
         FIG. 3  is a partial-section front view of the cable drum with the drive flange. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  schematically illustrates the construction of a lifting gear  1  which is formed as a cable pull. The lifting gear  1  comprises essentially a drive unit  2 , which consists of a motor and a transmission, a drive shaft  3  which is driven by the drive unit  2  and has a drive flange  4  fixed thereon, and a cable drum  5  which is connected in a rotationally fixed manner to the drive flange  4  and onto which or from which a cable  6 , which is only indicated, can be wound or unwound. In this case, the disk-shaped drive flange  4  has an outer diameter which is smaller than the inner diameter of the cable drum  5  in its end region, and is inserted laterally into the cable drum  5  so as to be flush therewith. 
     As shown in  FIG. 1 , the cable drum  5  is equipped with a so-called “3-point bearing”, in which the cable drum  5  is mounted via two bearings  7   a ,  7   b  on the side of the drive shaft  3  and is mounted via a bearing  8  on the side of a drum pin  9  lying opposite the drive shaft  3 . It is also possible to support the cable drum  5  directly via a bearing, whose outer ring lies against the inner side of the cable drum  5 . 
     Since, as a result of manufacturing and assembly tolerances and deformations under load, these bearings  7   a ,  7   b  and  8  are not always to be disposed in practice precisely aligned in a line, restraint stresses are caused in the mounted components, namely in the drive shaft  3  and/or in the drive flange  4  of the cable drum  5 . In order to avoid these undesired stresses which cannot be accurately calculated and which occur in addition to a useful load which acts as a cable pull force S, a coupling is provided which transmits the torque of the drive shaft  3  to the cable drum  5  in such a manner as to compensate for angles and lengths, as illustrated in  FIG. 2 . 
       FIG. 2  illustrates a sectional view of the coupling region of a lifting gear  1  in accordance with the invention. The coupling is disposed between the drive flange  4  and the cable drum  5 , whereas for its part the drive flange  4  is connected in a rotationally fixed manner to the drive shaft  3 . Of course, it is also possible to dispose a coupling between the drive shaft  3  and the drive flange  4 , wherein in this case it is necessary for the drive flange  4  to be connected in a rotationally fixed manner to the cable drum  5 . As a third embodiment of the coupling it is possible to accomplish the transmission of torque both from the drive shaft  3  to the drive flange  4  and also from the drive flange  4  to the cable drum  5  by means of a coupling. 
     As illustrated in  FIG. 2 , the coupling includes at least one coupling element  10  which rests in a recess  11  of the drive flange  4 . Two coupling elements  10  are illustrated by virtue of the selected angular section. The upper coupling element  10  is located in an attachment position and is disposed in a positive-locking manner between the drive flange  4  and the cable drum  5  which are to be coupled together. In contrast, the lower coupling element  10  is located in a rest position, in which it is located completely in the recess  11  of the drive flange  4  and thus does not couple the drive flange  4  and the cable drum  5  together. 
     Each coupling element  10  is sleeve-shaped and comprises at both ends driving cams  10   a ,  10   b  which face radially outwards and inwards and which engage into corresponding recesses  11  of the drive flange  4  and bores  12  of the cable drum  5  in order to transmit the torque. 
     Since the coupling elements  10  are subject to a considerable shear stress by virtue of the torque transmitted between the drive flange  4  and the cable drum  5 , the coupling elements  10  may be made of steel. 
       FIG. 2  also illustrates that the coupling element  10  is formed in a sleeve-like manner and consists substantially of the outer driving cam  10   a , the inner driving cam  10   b  and a central channel  10   c  which extends through the entire coupling element  10  and thus the outer driving cam  10   a  and the inner driving cam  10   b . The outer driving cam  10   a  is annular and has a smaller outer diameter a than the likewise annular, inner driving cam  10   b  with its outer diameter A. As a consequence, the coupling element  10  acquires a stepped outer shape having an annular and planar shoulder  10   d  in the region of the transition from the inner driving cam  10   b  to the outer driving cam  10   a . The central channel  10   c  comprises on its inner end an internal thread for the screw  13 . The screw  13  is supported with its head  13   a  on an outer, annular bearing surface  10   e  of the outer driving cam  10   a . In the attached state, this bearing surface  10   e  is located in the region of the outer surface of the cable drum  5  and protrudes only slightly. In the illustrated embodiment, the head  13   a  of the screw  13  does not protrude further than the thickness of the cable drum  5 , in any event not further than an annular cable guide  15  disposed on the cable drum  5 . 
       FIG. 2  illustrates the upper coupling element  10  in its operating position, in which the coupling element  10  is pushed outwards to a stop position in the recess  11 . In the associated assembly position, no screw  13  is initially located in the channel  10   c , which is provided with an internal thread, and the coupling element  10  rests, displaced inwardly, on the base  11   a  of the blind hole-like and cylindrical recess  11 , whose inner diameter is slightly larger, in order to permit a displacement in the longitudinal direction of the coupling element  10  but at the same time to ensure transmission of torque. For example, a transition fit may be used in this case. The length l of the coupling element  10  is less than or equal to the length L of the recess  11 , so that in the assembly position of the coupling element  10 , the outer driving cam  10   a  does not protrude from the recess  11  and thus the outer periphery of the drive flange  4 . Therefore, in the assembly position of the coupling element  10  it is possible within the scope of the assembly of the lifting gear  1  to push the cable drum  5  onto the drive flange  4 . In this case, the bores  12  in the cable drum  5  are aligned with the outer driving cams  10   a  of the coupling elements  10 , so that subsequent to the attachment of the cable drum  5  to the drive flange  4  the screw  13  can be screwed into the channel  10   c , until the tip  13   b  of the screw  13  impinges upon the base  11   a  of the recess. A further turning of the screw  13  ensures that the tip  13   b  of the screw  13  is supported on the base  11   a  and the coupling element  10  moves with its outer driving cam  10   a  outwards from the drive flange  4  and enters the bore  12  of the cable drum  5 , until at the end the shoulder  10   d  lies against the inner surface  5   a  of the cable drum  5 . An attachment piece for a tool is also provided on the outer driving cam  10   a , in order to secure the coupling element  10  when tightening the screw  13 . The corresponding tools and attachment pieces are of the commercially available type, e.g. hexagon flat. In the operating position, the attachment piece protrudes from the cable drum  5 . Therefore, the torque is transmitted directly from the drive flange  4  via the coupling element  10  to the cable drum  5 . The screw  13  secures the coupling element  10  only in its operating position and does not lie in the flux of force of the torque transmission. It has been demonstrated that the operating forces keep the coupling element  10  in the operating position. 
     In order to be able to compensate for a longitudinal offset between the cable drum  5  and the drive flange  4 , in the case of the illustrated exemplified embodiment the bores  12  for receiving the outer driving cams  10   a  are formed with a larger diameter from the outer periphery of the outer driving cams  10   a  and are thus formed in the axial and radial direction of the cable drum  5  to be larger than the corresponding driving cams  10   a  which are to be received. A gap  14  which is produced by reason of this formation and which is in the range of about 0.2 to 1.00 mm, for example 0.8 mm, is evident in  FIG. 2 . 
       FIG. 2  illustrates how an angular offset between the longitudinal axes of the cable drum  5  and the drive flange  4  and/or the drive shaft  3  can be compensated for. For this purpose, the drive flange  4  or the inner side of the cable drum  5  is curved. 
     A coupling which is formed in this manner is characterised by virtue of the fact that it is constructed in a simple manner and with a small installation size ensures that any manufacturing and assembly tolerances which occur are reliably compensated for. High torques can also be transmitted. 
       FIG. 3  illustrates a front view partially in section of the cable drum  5  with the drive flange  5  and it is thus apparent that three bores  12 , three recesses  11  and three coupling elements  10  are provided distributed uniformly on the periphery. This provides a sufficient level of stability.