Abstract:
A parallel indexer having a housing, an input shaft rotatably mounted in said housing, an output shaft rotatably mounted in said housing and extending exteriorly thereof, said input shaft and output shaft being arranged parallel to each other, said output shaft having a driven surface which mounts the plurality of roller gear drives thereon, and which are driven by at least one cam mounted upon the input shaft, said driven surface being normally fixed to the output shaft, and having a torque limiter arranged intermediate thereof and which when excessive torque is encountered, provides for disengagement between the driven surface and the output shaft, to disconnect the output for the parallel indexer.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to an internal overload clutch assembly which permits rotation between a rotating member and a rotatable member during normal operation, but which disconnects the rotating and rotatable members from each other when a maximum torque is exceeded. 
     In order to couple and uncouple drive shafts from driven shafts, a variety of styles of torque overload clutches or couplings have been developed. While prior art developments in torque overload clutches has been extensive, they can be generally described according to their construction and operation. Many of these clutch or coupling devices are in the category of flexible couplings which provide transmission of the driving, rotational, or torque force from a drive shaft to the intended driven shaft, but which are capable of disconnection when a binding force creates an excessive torque causing significantly reduced turning of a mechanical operator on a work component. In certain cases, the flexible couplings are provided with safety features which prevent excessive torque forces on the driven shaft from damaging the drive means and/or its prime mover. Many of the safety devices employed in flexible couplings include magnetically activated torque coupler devices as shown, for example, in U.S. Pat. No. 2,771,171. Another variety of magnetic coupling-clutch devices is shown in U.S. Pat. Nos. 3,221,389 and 3,339,819 which use mechanical elements that engage/disengage relative to one another, together with permanent magnets. Further types of magnetic torque limiting devices used in low force operating mechanisms, such as phonograph record players or sound recorders, are shown in U.S. Pat. Nos. 1,136,739 and 2,300,778. Other types of magnetic couplers include those which have spring biasing to determine the degree of force necessary for disengaging the coupling as shown in U.S. Pat. No. 3,053,365. Other forms of connectors which have utilized permanent magnet designs for output shaft  31  can rotate relative to each other. The forward portion  53  of the hub  41  has an increased diameter to form a larger front surface  55 . A series of holes  57  are formed in the hub&#39;s front surface  55 . 
     In addition to magnetic coupler designs, various mechanical coupling devices, using ball detent couplings for holding driving and driven parts together until separated by excessive torque are shown in U.S. Pat. Nos. 3,701,404, 3,680,673, 3,893,553, 3,981,382, 3,979,925, 3,942,238, 3,927,537, 3,930,382 and 3,866,728. Some mechanical coupling devices employ ball-bearing type means as the coupling/uncoupling element such as shown in U.S. Pat. Nos. 1,833,164, 3,722,644 and 3,774,738. Other types of power transmitting mechanisms having flexible couplings therein are shown in U.S. Pat. Nos. 1,541,489, 1,566,553, 2,818,712, 3,050,965, 3,148,499, 3,942,337, 4,006,608 and 4,046,237. 
     Along With the aforementioned categories, there is yet another category which has been developed by inventors employed by the assignee of the present invention. In U.S. Pat. Nos. 4,174,621 and 4,373,923, this particular type of mechanical torque limiting overload coupling/clutching device has been disclosed. In both of these patents, an improved overload torque coupler/clutch device has been developed in which suspended ball detents are used to interconnect rotating and rotatable members during normal operation, but upon encountering an excessive torque force on the rotatable member, suspended ball detents are shifted against a resilient spring out of seating engagement to disconnect the rotating and rotatable members. This improved style of torque limiting overload coupling minimizes rotational back lash or looseness, while maintaining precision operation of the rotatable member. In addition, a more precise and consistent de-coupling of the assembly is provided when a trip torque is encountered, and significant damage to the ball detents has been minimized. Such torque limiting overload coupling devices have been particularly useful in conjunction with cam indexing systems such as shown in U.S. Pat. No. 3,817,116, for example, which is also assigned to the same assignee of the present invention. The construction and operation of such cam operation systems include the use of radially mounted cam followers which are indexed by specifically designed multi-ribbed cams. The cam surfaces engage cam followers mounted on a hub to provide accurate positioning, while allowing clearance between adjacent cam followers. Mechanical torque limiting overload couplings which have been employed in conjunction with such cam indexing systems, have been operated as separate components, separate from, but operative with such systems. Thus, a typical set up would include a cam index system, with or without a separate speed reducer, and also a separately mounted torque limiting overload coupling which is mounted outside the housing of the cam index system, but which couples/uncouples the output driven shaft or flange thereof, to connect and disconnect the drive shaft or prime mover when an excessive torque is encountered. 
     In certain industries, however, it is necessary to expose all of the aforementioned mechanical components and driving systems to daily cleaning. This subjects the operating machine components to unnecessary exposure to moisture and deterioration, even though stainless steel may be used in the construction thereof. This has created a need for a self enclosed torque limiting clutch assembly which is contained in the same housing as the indexing system or prime mover. While it may appear at first sight that this would not require extensive engineering design and improvement in view of the highly developed nature of the prior art in this field, in actual fact; however, the development of the present invention did not come easily. Numerous designs were conceived and tested, some including magnetic coupler devices, but were unsuccessful. After much development and testing the internal overload clutch assembly of U.S. Pat. No. 4,828,095, which is also assigned to the same assignee of the present invention and which is incorporated herein by reference, was developed. The overload clutch assembly of that patent, however, was developed for use with a right angle indexer. There, however, is a need for an internal overload clutch assembly which can be used in parallel shaft indexers. 
     BRIEF SUMMARY OF THE INVENTION 
     This invention contemplates the parallel indexer having a housing, an input shaft rotatably mounted in said housing, an output shaft rotatably mounted in said housing and extending exteriorly thereof, said input shaft and output shaft being arranged parallel to each other, said output shaft having a driven surface which mounts the plurality of roller gear drives thereon, and which are driven by at least one cam mounted upon the input shaft, said driven surface being normally fixed to the output shaft, and having a torque limiter arranged intermediate thereof and which when excessive torque is encountered, provides for disengagement between the driven surface and the output shaft, to disconnect the output for the parallel indexer. 
     The principal object of this invention is to provide a parallel indexer, having an input shaft and output shaft that are arranged parallel to each other during the operation of the indexer. 
     Another object of this invention is to provide a torque limiter operatively associated within the output shaft, and which provides for disengagement when excessive torque is encountered, thereby discontinuing the rotations of the output shaft, notwithstanding the continued operations of the input drive. 
     These and other objects will become more apparent to those skilled in the art upon reviewing the subject matter of this invention, in light of the description of the preferred embodiment, in view of the drawings. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is a perspective view of a parallel shaft indexer which includes an internal overload assembly of the present invention. 
     FIG. 2 is a side elevational view, partly in section, showing the combined prime mover/internal overload assembly construction of the present invention as taken along lines  2 — 2  of FIG. 1; 
     FIG. 3 is a cross-sectional view of the indexer taken along line  2 — 2  of FIG. 1; and 
     FIG. 4 is an exploded perspective view of the internal overload assembly of the present invention. 
    
    
     Corresponding reference numerals will be used throughout the several figures of the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The following detailed description illustrates the invention by way of example and not by way of limitation. This description will clearly enable one skilled in the art to make and use the invention, and describes what we presently believe to be the best mode of carrying out the invention. 
     A parallel indexer  1  is shown generally in FIG.  1 . The indexer  1  includes a housing  3  having a front face  5  and a back face  7 . An input shaft  11  extends rearwardly from back face  7  to be connected to a prime mover (not shown), such as an electrical motor, which rotates the input shaft  11 . The input shaft  11  is rotatably journaled in front and rear bearing assemblies  13 ,  14  which, in turn are mounted in front and rear bushings  16  and  17 . A pair of cams  21  are mounted on the input shaft  11  within the housing  3 . The cams  21  are spaced apart by a spacer  23  which is integral with the shaft  11 . The cams  21  are rotationally fixed to the input shaft  11  to rotate with the shaft as the shaft  11  is rotated by the prime mover. 
     A torque limiter housing  29  is mounted to the housing front face  5 . An output shaft  31  extends from the housing back face  7 , through the housing  3  and the torque limiter housing  29  to extend out the front  33  of the torque limiter housing  29 . The output is rotatably journaled in rear bearing assembly  35  mounted in the back face  7  of the housing  3  and a front bearing assembly  37  mounted in the front  33  of the torque limiter housing  29 . The output shaft  31  has a first portion  39  which is journaled in the back bearing assembly  35  and extends the width of the housing  3 . In the torque limiter housing  29 , the output shaft  31  is stepped at  31   a,    31   b,  and  31   c  to form sections of increasing diameter. Externally of the torque limiter housing  29 , the output shaft  31  is stepped down as at  31   d  to be a similar diameter as the first section  39 . 
     A hub  41  is mounted on the output shaft first section  39 . The hub  41  includes a sleeve  43  from which three plates  45 ,  46 , and  47  extend. The plates  45 - 47  each have a series of holes  49  extending around the periphery of the plates. The holes  49  of the plates  45 - 47  are aligned with each other. Rollers  51  are mounted between plates  45  and  46  and between plates  46  and  47 . The rollers  51  are rotatably mounted on rods  52  which extend through the aligned holes  49  of the plates  45 - 47 . The input and output shafts  11  and  31  are positioned relative to each other so that the cams  21  extend into the space between the plates  45 - 47  so that the cams  21  will engage the rollers  51  as the cams are turned by the rotating action of the input shaft. When the cams  21  do engage the rollers  51 , the rollers  51  are pushed by the cams  21  to cause the hub  41  to rotate about its axis. The hub sleeve  43  is not fixed to the output shaft first section  39 , and, as will be discussed below, the hub  41  and output shaft  31  can rotate relative to each other. The forward portion  53  of the hub  41  has an increased diameter to form a larger front surface  55 . A series of holes  57  are formed in the hub&#39;s front surface  55 . 
     A torque limiter  61  is contained within the torque limiter housing  29 . The torque limiter  61  is fully enclosed in the housing  3  and the torque limiter housing  29 . Thus, the indexer  1  can be used in environments in which exposed limiters cannot be used, such as environments in which the limiters would require extensive cleaning to remain operational or to continue to be used for a specific purpose. 
     The torque limiter includes a drive plate  63  which is positioned about the output shaft portion  31   a  to be adjacent with the hub front surface  55 . The drive plate  63  includes a series of pin holes  65  which extend through the plate. The pin holes  65  of the drive plate are alignable with the holes  57  in the front surface  55  of the hub  41 . Pins  67  are passed through the drive plate pin holes  65  and into the hub holes  57  to rotationally fix the drive plate  63  relative to the hub  41 . Thus, as the hub  41  is rotated by the cams  21 , the drive plate  63  will also rotate. The drive plate  63  also includes a series of seats or detents  69  around the periphery of the plate. The seats  69  are preferably radially extending in plan and semi-circular in cross-section. The seats  69  are not regularly spaced about the drive plate  63 . 
     A driven plate  71  is positioned adjacent the drive plate  63  around the output shaft section  31   a.  The driven plate  71  includes a series of pin holes  73  which accept pins or dowels  75 . The pins  75  extend into holes  77  in the rear face  79  of the output shaft section  31   b.  The drive plate  71  also includes a plurality of slots  81  which extend radially inwardly from the outer edge of the driven plate. The driven plate slots  81  are not evenly spaced about the edge of the driven plate  71 . However, the drive plate seats  69  and the driven plate slots  81  are alignable with each other. Thus, for each driven plate slot  81 , there is a corresponding drive plate seat  69 . A roller  83  is received in each driven plate slot  81 . The driven plate  71  has a circumferential slot  85  which receives a lock ring  87  or the like to hold the rollers  83  in the driven plate slots  81 . The rollers  83  are sized, such that they are also seated in the drive plate seats  69 . The engagement of the rollers  83  with the drive plate  63  is such that, as the drive plate  63  is rotated, the drive plate  63  will rotate the driven plate  71 . Because the driven plate  71  is rotationally fixed to the output shaft  31 , the rotation of the driven plate  71  by the drive plate  63  will cause the output shaft to rotate. 
     A switch flange  91  is positioned about the output shaft section  31   b.  The switch flange  91  and the driven plate  71  each form seats  93  and  94  on which a thrust washer  97  and a thrust bearing  99  are positioned. A compression ring  101  is mounted around the output shaft section  31   b.  The compression ring  101  includes a plurality of posts  103  on which spiral springs  105  are mounted. The springs  105  press against the switch flange  91 . Three adjusting screws  107  extend through openings  109  in the front face of the output shaft section  31   c  to engage the compression ring  101 . The screws  107  can be adjusted to alter the load force applied by the springs  105  on the switch flange  91 . 
     In operation, the input shaft  11  and cams  21  are rotated by the prime mover. The rollers (or followers)  51  on the hub  41  are engaged by the cams  21 , and the rotation of the cams causes the hub  41  to incrementally rotate about the output shaft first section  39 . The drive plate  63  of the torque limiter  61  is fixed to the hub  41 , and hence rotates about the output shaft  31  with the hub  41 . The driven plate  71  is separate from the drive plate  63  and its rollers  83  engage the seats  69  of the drive plate  63 . The compression load of the springs  105  load the switch flange  91 , which in turn loads the thrust washers  97  and thrust bearings  99 . This force is applied directly to the rollers  83  keeping them in the drive plate seats  69 . Thus, the driven plate  71 , and hence the output shaft  31 , is rotated by the drive plate  63 . When a set torque is exceeded, the rollers  83  will overcome the force of the springs  105 , and will become disengaged from the drive plate seats  69 . Thus, the driven plate  71  and the drive plate  63  will be disengaged from each other. When this occurs, the driven plate  71  and the output shaft  31  will cease to rotate. However, the input shaft  11 , the cams  21 , and the hub  41  will continue to rotate. 
     The compression load of the springs  105  determines the torque capacity of the limiter or clutch  61 . As noted above, the load of the springs  105  (and hence the torque capacity of the limiter) can be set or adjusted by turning the adjusting screws  107  in equal increments. As the adjusting screws  107  move, the compression ring  101  moves axially along the output shaft  31 . The springs  105  are trapped between the compression ring  101  and the switch flange  91 . Therefore, the movement of the compression ring  101  (due to adjustment of the screws  107 ) changes the spring load, and thus the torque capacity of the unit. 
     The indexer  1  also includes a switch assembly  111  which is responsive to movement of the switch flange  91 . The switch assembly cab be in electrical communication with the prime mover, and when activated, causes the prime mover to be turned off. When the torque limit of the unit is exceeded, the driven plate rollers  83  will come out of the drive plate seats  69  to disengage the driven plate  71  from the drive plate  63 . When this occurs, the rollers  83  will move axially in the driven plate slots  81 . The rollers  83  are adjacent the switch flange  91 , and the movement of the rollers, as they become disengaged from the drive plate seats  69 , will cause the switch flange  91  to move axially away from the drive plate  63 . The change in position of the switch flange  91  will cause the switch assembly  111  to activate, and the prime mover will cease operations. 
     As noted above, the driven plate slots  81  and the drive plate seats  69  are irregularly spaced around the driven plate  71  and the drive plate  63 , respectively. Thus, when the drive plate  63  and driven plate  71  are disengaged from each other by a torque overload condition, it will require a full revolution of the drive plate  63  before the drive plate  63  and driven plate  71  are again engaged with each other. The limiter will automatically be reset when the driven plate rollers  83  are again received in the drive plate seats  69 . 
     As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. For example, the spiral springs  105  can be replaced with other types of resilient members which will apply a load to the rollers  83 . For example, a spring washer could be used. Even an annular foam ring could be used, as long as the foam is resilient. Balls could be used in place of the rollers. The drive plate  63  could be integrally formed with the hub  41 . Similarly, the driven plate could be integrally formed with the output shaft  31 . These examples are merely illustrative.