Abstract:
A tensioning device ( 32 ) for tensioning at least two, substantially length-invariant belts ( 18, 24 ) includes a first belt ( 18 ) guided about a first axis (A), which repeatedly guides an adjusting movement in an adjustment direction substantially orthogonal to the axial direction of the first axis (A). In addition, the first belt ( 18 ) and a second belt ( 24 ) are guided about a common second axis (B), whereby the tensioning directions (V 18 , V 24 ) of the first belt ( 18 ) and of the second belt ( 24 ) in a region of the second axis (B) forms a varying angle of between 0° and 180°. The second axis (B) is associated with a spring unit ( 40 ), which prestresses in the sense of the tensioning of the first belt ( 18 ) and the second belt ( 24 ) and which, upon an adjusting movement of the first axis (A), permits a compensating movement of the second axis (B) from the plane covered by the axial direction of the second axis (B) with the tensioning directions (V 18 , V 24 ) of the first belt ( 18 ) and of the second belt ( 24 ), respectively, before initiating of the adjusting movement.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a device for tensioning at least two essentially length-invariant belts, whereby a first belt is guided around a first axis, which repeatedly performs an adjustment movement in an adjustment direction that runs orthogonally to the axial direction of the first axis, and whereby the first belt and a second belt are guided about a common second axis, whereby the tensioning directions of the first belt and of the second belt, in the region of the second axis, form a varying angle of between 0° and 180°.  
           [0002]    In connection with the present invention, when the teaching “essentially length-invariant belts” is used, what is meant is that the belts practically cannot be reacted by means of a change in length from an outer force acting on them, as is the case, for example, with common polyurethane belts. Of course, it is clear, however, that this type of length-invariant, or rigid material, has a known elasticity. This insignificant elasticity, however, does not contradict the fact that in the frame of the present invention, the belts are essentially length-invariant.  
           [0003]    In addition, when the teaching is that a belt is “guided around an axis”, it should also be understand that the belt is guided about a belt pulley, or a pinion, which is rotatably attached on a rigid axis, or rigidly attached on a rotatably shaft. It is also contemplated, however, that the belt is guided about a plurality of correlated axes, for example, based on common movement.  
           [0004]    Finally, regarding the tensioning directions of the first and second belts, it is to be understood that what is meant is the positive direction of the respective tensioning forces which these belts exert on the second axis.  
           [0005]    These types of lifting-transverse units, as are disclosed, for example, in DE 30 12 355 A1 and DE 196 03 554 A1, serve in a conveyance system for work pieces, or work piece carriers, to stop work pieces, or work piece carriers, transported on a first conveying track, to lift the work pieces or work piece carriers from the conveyor means of the first conveyor track, and to transfer the work pieces or work piece carriers to a second conveyor track that is mostly orthogonal to the first conveyor track. The lifting-transverse unit includes a lifting unit with integrated lift apparatus, for example, a pneumatic cylinder, and one or more guide rods. With a positioning element of the force apparatus, for example, the piston rod of the pneumatic cylinder, and the guide rods, a lifting plate is rigidly connected, on which a plurality of axes for supporting guide pulleys for tensioning belts are provided. These axes together form “a first axis” in the sense of the present invention. By means of the tensioning belts, the work piece, or the work piece carrier, is transported after lifting from the first conveyor track to the second conveyor track. For driving the tensioning belts, these are guided about a further axis, about which also a drive belt is guided, which, in turn, is driven by a geared motor or the like.  
           [0006]    With the lifting-transverse unit HQ2/S, also the lifting movement is made with the common axis of the tensioning belts and drive belts, so that as a result, this lifting movement indeed does not change the tensioning or stretching of the tensioning belts, rather the tensioning of the drive belts. Therefore, a tensioning device in the form of tension rollers are provided, which, upon the assembly of the entire device, are adjusted. The change in length on the belts is therefore not equalized; that is, the tensioning is different depending on the stroke adjustment. Upon use of an addition, spring-loaded tension roller, the belt tension can be held constant.  
           [0007]    In addition, a further lifting-transverse unit of Bosch GmbH is known, namely, the lifting-transverse unit HQ1/O. With this unit, the drive belt is formed from a loop of polyurethane so that it can reacted to the lifting movement as well as the manufacturing and assembly tolerances by means of an elastic elongation or extension, that is, by means of a change in length.  
         SUMMARY OF THE INVENTION  
         [0008]    In contrast, the problem addressed by the present invention is to provide a tensioning device, in particular, for a device for transposition of work pieces, or work piece carriers, which, despite fixed assembly of a drive motor of the belts also with the use of essentially length-invariant belts, makes possible that the tensioning of the belt, also in tensioning of the adjustment movement of the first belt, is essentially not changed.  
           [0009]    This problem is resolved according to the present invention by a tensioning device of initially described type, in which the second axis is associated with a spring unit, which biases in the sense of the tensioning of the first belt and the second belt and which, upon an adjustment movement of the second axis, permits a compensating movement of the second axis from the plane extending through the axial direction of the second axis with the tensioning directions of the first belt and the second belt, respectively, before beginning of the positioning or adjusting movement. By means of the inventive compensation movement, the distance of the first axis from the second axis as well as the distance of the second axis from the drive axis of the second belt can be maintained essentially constant. In consideration of the length-invariance of the belts, this leads to the result that the tensioning of the belts can be maintained essentially constant. Then, only when the displacement of the second axis brings up a change of the tensioning force of the spring unit, also an insignificant change of the tensioning of the belt is provided. The change of the tensioning force of the spring unit, for example, can be minimally maintained by means of the use of a biased spiral spring, be it a compression spring or a spiral tension spring, or a gas spring with comparatively thinner piston rods, with reference to the entire diameter of the piston.  
           [0010]    A further advantage of the invention is to be seen in the simplification of the construction of the tensioning device, and thus, the entire transposition device, thereby achieving that the use of an additional tension roller can be eliminated.  
           [0011]    In a further embodiment of the invention, it is proposed that the first axis (or the plurality of first axes) is supported on an adjustable belt relative to a base unit, and that the second axis (or the plurality of second axes) is supported on a holder, which is guided displaceably on the belt relative to this, whereby the spring unit is braced on one end on the belt and on the other end on the holder. This makes possible a particularly compact and space-saving construction not only of the tensioning device, rather the entire transpositioning unit. Basically, however, it is also possible to guidably support the support on the drive axis of the second belt, or the housing of the drive motor for the second belt or alternatively, on the base unit.  
           [0012]    For a simple and cost-effective construction, it can be provided that a base plate of the tensioning device and/or the support that is attachable, or attached, to the belt is made from a sheet, preferably a metal sheet. In particular, the base plate and/or the support can be formed as a punched or cut (for example, by means of a laser) and, as desired, bent sheet part.  
           [0013]    For facilitating of changing out of the first and second belts, it can be provided that at least one bearing of the second axis is formed as recess open on one side. In normal operation, therefore, the dropping out of the second axis from this bearing by means of the tensioning of the first belt and/or by means of the tensioning of the second belt can be prevented, and this is done in a simple manner by corresponding orientation of the open side of the recess. In particular, at least one of the areas of contact of the recess are oriented such that, in consideration of the positive direction of the tensioning force of the respectively observed belt (i.e., the tensioning direction of the belt), it operates as a directional projection for the second axis in the recess.  
           [0014]    For realizing the guiding of the second axis relative to the frame, at least one ribbed guide can be provided on either the base plate or holder, and on a respective other part, support or base plate, and coordinated guide recess can be provided. In particular, with the sheet metal manufacture of the base plate and/or holder, the at least one ribbed guide can be made by bending of a sheet bar. Already in the simplest case, in which the compensating movement of the second axis exists in a pivoting movement about the drive axis of the second belt, this compensating movement cannot be realizable by means of a simple, linear guide, without the danger of a canting or other type of blocking of the support on the base plate. For simplification of the form of the guide means, ribbed guides and guide recess, it is therefore proposed that the ribbed guide runs substantially orthogonally to the tensioning direction of the second belt before beginning of the adjusting movement, and that the guide recess is measured with reference to the dimension size of ribbed guide therein that the support is pivotable about an axis running substantially parallel to the second axis.  
           [0015]    The belts preferably can have an insert made from a tension-proof material for achieving of the length-invariance, for example, an insert made from tension-proof glass fiber material, tension-proof plastic fibers, or metal, in particular, steel wires. Not only, however, can these materials improve the length-invariant construction, but also the construction of the belts as toothed belts can improve the durability of the belts as well as the precision of the movement of the first belt.  
           [0016]    For facilitating assembly and/or disassembly of the first and second belts, the tensioning device is proposed as a whole, however also the base plate and/or the support can be individual parts of the tensioning device. It is also contemplated that on the base plate and/or the holder, a supporting spindle for holding the spiral spring is provided and/or that on the base plate and/or the holder, at least one stop for limiting the relative movement between the base plate and support is provided.  
           [0017]    In order to provide that the tensioning force of all belts is substantially the same size, it is proposed in another embodiment that the point of impact of the spring unit on the support relative to the position of the second axis is selected in consideration of the tensioning directions of the first belt and the second belt and corresponding to the number of first belts and the number of second belts. After assembly of the tensioning device as well as the belt, a stationary state is utilized, in which the tensioning of the first belt exerts a moment of rotation, which is oppositely directed relative to the moment of rotation exerted on the support from the tensioning of the second belt, but which is of the same total size as the moment of rotation exerted on the support from the tensioning of the second belt. Should all of the belt be operated with essentially the same tensioning force, then the lever arm of the conversion of the tensioning force of all belts of one observed type (first belts or second belts) originating from a situation with only a single one of such belts must be selected to be inversely proportional to the number of belts of this type. With a tensioning device for two first belts and one second belt, the lever arm of the first belts, then, must be selected to be half as big as the lever arm of the second belt.  
           [0018]    According to a further point of view, the present invention relates further to a device for transpositioning work pieces or work piece carriers with a tensioning device according to the present invention.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    [0019]FIG. 1 is a perspective view of a positioning device that is equipped with a tensioning device according to the present invention;  
         [0020]    [0020]FIG. 2 is a schematic side view of the support of the inventive tensioning device for explanation of the force acting on this holder; and  
         [0021]    [0021]FIG. 3 is a schematic illustration of the running of the first and second belts for explanation of the basic functioning principles of the inventive tensioning device.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    In FIG. 1, the inventive transpositioning device, in whole, is designated with reference numeral  10 . These types of transpositioning devices are known in the state of the art, and therefore, will not be described here in great detail. The transpositioning device  10  serves for transferring or transpositioning work pieces, or work piece carriers, from a first conveyor track T 1  onto a second conveyor track T 2 . The transport belts of the first conveyor belt T 1  are shown in FIG. 1 in dash-dot representation and those of the second conveyor track T 2  are indicated in dot-dash lines as well.  
         [0023]    The transpositioning device  10  includes a lifting plate  12 , which, by means of a lifting device  14 , for example, a pneumatic cylinder, can be shifted, in particular, lifted and lowered. In this manner, the work pieces or work piece carriers can be brought out of contact with the transport bands of the first conveyor track T 1 . On the lifting plate  12 , guide rollers  16  are rotatably mounted about axes A 1  and A 2 , whereby the axial directions of these axes A 1  and A 2  run substantially parallel to the direction of course of the transport bands of the first conveyor track T 1 . Adjustment belts  18  are lead about these guide rollers  16 , which, after the lifting of the work pieces or the work piece carriers from the first conveyor track T 1 , are drive, in order to move the work piece or work piece carrier transverse to the direction of course of the transport bands of the first conveyor track T 1 , and thereby bringing them into contact with the transport bands of the second conveyor track T 2 . The axes A 1  and A 2  form together a first axis A in the sense of the present invention.  
         [0024]    For driving the adjusting belts  18 , these belts are guided about pinions, which are rotatably supported on an Axis B, or which are non-rotatably connected with a rotatably shaft B. On this axis or shaft B, a further pinion  22  is arranged, about which a drive belt  24  is guided. The drive belt  24  can be driven by means of a drive unit, for example, a geared motor, not shown in FIG. 1. The geared motor can be activated or deactivated by a control unit, which receives corresponding sensor signals from suitable sensors regarding the position of the work pieces or work piece carriers, and process these signals according to a provided algorithm.  
         [0025]    Since, according to FIG. 1, the back and forth running strands  18   a  and  18   b  of the adjusting belt  18 , or  24   a  and  24   b  of the drive belt  24 , run substantially parallel to one another, their course of direction corresponds generally also to the positive direction of the respective tensioning force of the belt  18  or  24  (i.e., the tensioning direction V 18  or V 24 ; see FIG. 3).  
         [0026]    It should be noted that the adjusting belt  18  and the drive belt  24  preferably are formed as toothed belts with glass fiber inserts. In this manner, the desired precision of control of the movement of the adjusting belt  18  can be achieved. In addition, the belts, essentially length-invariant, belts, have a high durability.  
         [0027]    In addition, the lifting device  14  is fixedly connected via a base plate  26  with a higher assembly (not shown in FIG. 1). Further, one recognized in FIG. 1 the adjusting element  28  of a force apparatus of the lifting device  14 , as well as two guide rods  30 , which serve to guide the lifting plate  12  in the adjusting direction S.  
         [0028]    The common axis B to the belts  18  and  24  is supported in a tensioning device  32 , whose construction and function will be explained in detail below:  
         [0029]    The tensioning device  32  includes a base plate  34 , which is connected with the lifting plate  12  via the guide rods  30 . The base plate  34  is manufactured as a stamped or cut (for example, by means of a laser) and bent metal sheet part. In particular, the base plate  34  includes three clips, which are bent out of the plane of the sheet according to the orientation shown in FIG. 1, specifically two ribbed guides  36  and a holding bar  38  for a compression spring  40 . In addition, the tensioning device  32  includes a support  42 , in which the axis B is supported. The support  42  is likewise manufactured as a stamped or cut and bent sheet part. In particular both the transverse ends  42  having the bearing recesses  44  for the axis B are bent downwardly from the plane of the sheet, according to the orientation shown in FIG. 1. In the base bar  42   b  of the support  42 , two guide recess  46  are formed, which are traveled over by the ribbed guides  36  of the base plate  34 . The compression spring  40  braces on one end on the base plate  34  and on the other end on the support  42 , and thereby tensions the adjusting belt  18  as well as the drive belt  24 , as will be described below in greater detail. The relative movement of the base plate  34  and the support  42  are limited by means of a stop  38   a.    
         [0030]    For explanation of the force acting on the support  42 , reference will now be made to the schematic side view of the support  42  illustrated in FIG. 2:  
         [0031]    As previously noted, the spring  40  impels the support  42  downwardly with a force F 42 . As a result of this force F 42 , the adjusting belts  18  are tensioned, which produced the counter force F 18  acting on the axis B. The force F 18  leads to a moment of rotation M 1  and the pivoting axis D (M 1 =F 18 ×L 1 ). This moment of rotation M 1  is compensated in the stationary state by a corresponding counter moment M 2 , which originates from the tensioning force F 24  of the drive belts  24  (M 2 =F 24 ×L 2 ). The corresponding counter force is exercised on the support  42  by means of the ribbed guides  36  of the guide plate  34 . One can easily see in this connection that it does not depend on the accurate position of the ribbed guides  36  or the guide recesses  46  in the plane of the base leg  42   b  of the support.  
         [0032]    The embodiment shown in FIG. 1 has two adjusting belts  18  and a drive belt  24 . In order to also enable in this case a varying number of adjusting belts  18  and drive belts  24 , in which all of the belts  18  and  24  are tensioned with substantially the same force, the lengths L 1  and L 2  of the lever arms of the tensioning forces F 18  and F 24  and the number of the respective belt type should be inversely proportional to one another. With a tensioning device  32  for two adjusting belts  18  and one drive belt, as illustrated in FIG. 1, the length L 1  of the lever arm of the adjusting belt  18  should be selected, then, to be half as large as the length L 2  of the lever arm of the drive belt  24 . It should be noted that this ratio is not realized in the illustration according to FIG. 2.  
         [0033]    In addition, the bearing recess  44 , in which the axis B is supported, is formed to be open on one side. Nevertheless, the axis B is securely held in this bearing recess  44 , since neither the tensioning force F 18  of the adjusting belt  18  nor the tensioning force F 24  of the drive belt  24  has a component outside of this recess  44 . In the embodiment shown in the figures, the adjusting belts  18  and the drive belts  24  run substantially orthogonally to one another.  
         [0034]    If the transpositioning device  10  is to be operated, in order to lift up a work piece or a work piece carrier from the conveyor bands of the conveyor track T 1 , that is, the lifting device  14  is extended in order to lift the lifting plate  12 , also the axis B is lifted, based on the length-invariance of the adjusting belt  18 . Since the drive axis C of the drive belt  24  is fixedly arranged, and also the drive belt  24  l formed to be substantially length-invariant, the axis B guides a circular movement K about the drive axis C, in the simplest case, sketched in FIG. 3, upon lifting of the lifting plate  12 .  
         [0035]    About the axis B, also in practice, this movement makes it possible first to take up the entire tensioning device  32 , or more accurately, its base plate  34 , via the guide rods from the lifting plate  12 . In addition, the ribbed guides  36  and the guide recesses  35  make possible a linear compensating movement in the adjusting direction S. Finally, the guide recesses  46  in comparison with the cross section of the ribbed guides  36  are dimensioned or oversized such that the support  42  can not only move linearly upwardly or downwardly along the ribbed guides  36 , but also can pivot about the axis D, without the danger of canting or blocking of the ribbed guides  35  in the guide recesses  46 . Essential to this pivoting movement is that it has a component that runs orthogonally to the adjusting direction S. The linear and pivoting compensating movement leads to a change of the tensioning of the spring  40 .  
         [0036]    The circular movement K, then, is approximated through a superimposition of a linear drag movement (in adjusting direction S), as well as a linear (in adjusting direction S) and a pivoting (about the axis D) compensating movement. In this manner, the length of the belts  18  and  24  do not need to be changed upon the lifting movement H of the lifting plate  12 . Merely the tensioning of the belts  18  and  24  changes in the amount in which also the spring force of the spring  40  varies. This spring force change, however, is based on the fact that it is generated only from the compensating movement, not, however, from the entire movement of the base plate  34  of the tensioning device  32 , and can be minimized further to this purpose by use of a biased spring without further.  
         [0037]    It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.  
         [0038]    While the invention has been illustrated and described herein as a tensioning device and transpositioning device with the tensioning device, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.  
         [0039]    Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.