Patent Document

BACKGROUND OF THE INVENTION 
     This invention relates to couplers for connecting two shafts together for the purpose of transferring rotational motion from one shaft to the other. The coupler has particular application in the agricultural irrigation field where irrigation pipeline support towers have centrally located drive motors for propelling wheels located at the ends of the towers. The motor&#39;s gear box is connected to worm drives at the wheels by drive shafts. Drive couplers are used to connect the drive shaft to both the motor gear box and the worm drives. Of course couplers could also be used in other applications where two generally aligned but spaced shafts have to be connected such that rotational motion of one shaft is transferred to the other. Additionally, it is quite often desirable that the coupler be able to tolerate some degree of misalignment between the shafts. Misalignment usually takes the form of the shafts not being parallel to one another. 
     The invention is particularly concerned with situations where the ends of the shafts remote from the coupler have to be fixed in position prior to installing the coupler. Accordingly, the shafts have no axial movement and perhaps little or no transverse movement available with the result that the coupler has to be installed generally between and/or around the pre-installed shafts. 
     Prior art couplers of the above type are known as split couplers and have what might be described as a built-up construction wherein a plurality of arms are placed about the end of a shaft and bolted together. The arms extend beyond the end of the shaft where they intersect with the arms of the opposite shaft or some intervening third part in some sort of engagement. Sometimes a rubber connecting block is involved to accommodate misalignment but this leads to problems with the rubber block adding lots of torsional movement called wind-up, with attendant backlash problems. In addition to wind-up, a major problem with the built-up construction is the high number of components and the large number of fasteners required. The high part count adds to cost and installation time. 
     SUMMARY OF THE INVENTION 
     The present invention concerns a coupler for transmitting rotational motion from one shaft to an adjacent but spaced shaft. A primary object of the invention is a coupler whose installation can be completed after that of the shafts and with a minimal number of parts. 
     Another object of the invention is a coupler of the type described which can accommodate misalignment of the shafts. 
     A further object of the invention is a coupler that reduces lost torsional movement or wind-up. 
     These and other objects which may become apparent in the following specification are realized by a coupler for connecting first and second shafts. The coupler has first and second connector elements attached to the ends of the respective shafts. The connector elements each include a plurality of splines defining grooves therebetween. One set of splines is internal and the other external such that the splines of one connector element fit into the grooves of the other connector element to interlock the connector elements in rotationally-driving relation. A sill is attached to the second connector element and defines a pocket into which an end portion of the second shaft can be placed by means of a non-axial relative movement between the sill and second shaft. A clamp member is engageable with the sill to enclose the end portion of the second shaft and fix the shaft in rotationally-driving relation with the second connector element. The clamp has a lug which fits into a slot formed in an end wall of the second connector element. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevation view of a portion of the drive system of an agricultural irrigation machine, showing three of the couplers of the present invention. 
     FIG. 2 is an enlarged side elevation view of the coupler assembly, showing the clamp both in phantom and solid lines to illustrate its installation procedure. 
     FIG. 3 is a section taken along line  3 — 3  of FIG.  2 . 
     FIG. 4 is a side elevation view of a wear pad. 
     FIG. 5 is a side elevation view of a connector element in the form of a male cross piece. 
     FIG. 6 is an end elevation view of the cross piece of FIG.  5 . 
     FIG. 7 is a top plan view of a connector element in the form of a female body. 
     FIG. 8 is an end elevation view of the female body. 
     FIG. 9 is a side elevation view of a clamp. 
     FIG. 10 is an end elevation view of the clamp. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates the drive coupler  10  of the present invention as applied to the propulsion system of a support tower for an agricultural irrigation machine. That system includes an electric motor  12  mounted near the center of the tower and coupled to a gear box  14 . The gear box has two output shafts  16 , one on each side of the box. Each output shaft  16  is connected by a coupler  10  to a square drive shaft  18 . The drive shafts  18  extend to the ends of the tower where they are connected by a coupler  10  to an input shaft  20  of a wheel box  22  (only one of a tower&#39;s two wheel boxes in seen is FIG.  1 ). The wheel box  22  includes a worm gear  24  driving a hub  26  to which a wheel (not shown) is attached. 
     FIGS. 2 and 3 show the assembly of the coupler  10 . Generally, the coupler comprises first and second connector elements  28  and  30  in the form of a male cross piece and a female body member. The first connector element  28  fits on the end of the square drive shaft  18  while the second connector element  30  is fastened to the input shaft  20 . The cross piece fits within the body member in interlocking engagement as will be explained below. The first and second connector elements are preferably die-cast aluminum, although other materials and fabrication methods are possible. 
     Turning now to FIGS. 5 and 6, details of the first connector element  28  will be described. Element  28  has a body  32  including four walls  34  and a circular stop or flange  36  at one end. As seen in FIG. 6, the stop  36  has a diameter larger than the outside perimeter of the walls  34 . The walls  34  define a central socket  38 . The socket extends through the stop  36  but is closed off at the opposite end by an end wall  39 . The socket is sized and shaped to receive the drive shaft  18  therein. Thus, in the illustrated embodiment the socket matches the square cross section of the drive shaft. The body  32  is retained on the shaft by a cross pin  40  (FIG. 3) which extends through aligned holes  42  in two of the walls  34  and an aligned opening in the end of the shaft  18 . Alternately the body  32  could be fixed to the shaft by staking, swaging, set screw or other suitable method. 
     Extending from the body  32  are four splines  44 . Each spline has a root  46  located at a corner of the intersecting walls  34 . The spline extends radially to a distal or free end  48 , giving the element a cross shape when viewed endwise as in FIG.  6 . FIG. 5 illustrates that each spline extends axially from the stop  36  to a taper or relief  50  at the opposite end of the body. The clearances between the mating parts of the coupler, together with the taper  50 , permit the coupler to run with a slight misalignment between the shafts. The design shown has been found to tolerate between three and five degrees angularity between the shafts. The splines  44  define a groove or channel  52  between them. 
     Details of the second connector element  30  can be seen in FIGS. 7 and 8. This connector element includes a cylindrical housing  54  having an open end at  56  and a closed end at wall  58 . The wall has an aperture  60  therethrough with a semi-circular bottom edge  62  and an angled top edge  64 . The housing  54  defines a cavity into which four internal splines  66  (FIG. 3) extend. The splines  66  have an anchor portion  68  and a wear pad or cushion  70 . The splines include a root  72  at the anchor and a free end  74  on the pad. Details of the wear pad  70  will be described below. 
     The second connector element  30  further includes a sill  76  integrally formed on the wall  58  on the side opposite the housing  54 . The sill terminates at a ledge  78  which has a central depression forming a pocket  80 . The pocket aligns with and conforms to the shape of the bottom edge  62  of the aperture  60 . A bore  82  extends through the ledge  78  at the base of the pocket  80 . 
     A clamp  84  is shown in FIGS. 9 and 10. The clamp has a body  86  with flat bottom surfaces  88  engageable with the ledge  78  of sill  76 . One edge of surfaces  88  is beveled as at  90  to facilitate installation of the clamp. A central, semi-circular groove  92  extends through the body. Just above the groove, on one side of the body is an upwardly angled lug  94 . The lug has a semi-circular cutout on its underside. The cutout is aligned with the groove  92 . The angle of the lug matches the angled top edge  64  of the aperture  60 . A bore  96  extends through the body of the clamp for receiving a retention bolt  98  (FIG.  2 ). Bolt  98  also extends through a hole in the input shaft  20  and through the bore  82  in the sill. It is held in place by a nut  104 . 
     The wear pads or cushions  70  are shown in FIGS. 3 and 4. Each pad has a pair of legs  100  which define a channel  102  in the shape of the anchor  68 . Thus, the pads  70  slide lengthwise onto an anchor  68  as best seen in FIG.  3 . The pads are preferably made of urethane having a Shore D 75 durometer. The pads leave a space between them which is just wide enough to accept a spline  44  of the cross piece  28  in a snug fit. Similarly, the channels  52  have a size and shape that receives the splines  66  in interlocking engagement. 
     The use, operation and function of the coupler are as follows. A common situation encountered in assembly of drive couplers is the need to assemble a portion of the drive train in between two components of the drive train which are already fixed in position. In terms of the drive system of FIG. 1, such a situation would arise when the gear box  14  and wheel box  22  are mounted first and the drive shaft  18  has to be inserted between them. The drive coupler  10  permits this to be done through the following assembly sequence. Two of the first connector elements  28  are attached to the ends of the drive shaft  18  by inserting the shaft into the socket  38  and placing the cross pin  40  through holes  42 . This locks the cross pieces  28  on the shaft  18 . 
     Two of the second connector elements  30  are prepared by sliding a wear pad  70  onto each of the anchors  68 . The second connector elements are then placed over the first connector elements such that the cross piece  28  fits into the housing  54  with the splines of one element engaging the grooves of the other as best seen in FIG.  3 . That is, splines  66  of housing  54  fit into the grooves  52  of the cross piece  28  and the splines  44  of the cross piece fit into the spaces between the pads  70 . The stop  36  of the cross piece  28  will engage the pads  70  to prevent them from working off of the anchors  68 . 
     With the first and second connector elements  28  and  30  interlocking with one another and attached to the ends of the drive shaft  18 , the assembly can be placed between the gear box  14  and wheel box  22 . Considering the coupler near the wheel box, the shaft  18  is lifted transversely to shaft  20  so that shaft  20  settles into the pocket  80  of the sill  76 . Then the shaft  20  is rotated so its bore aligns with the bore  82  in sill  76 . Next the clamp  84  is placed over shaft  20 . This is done by first tipping the clamp as shown in phantom in FIG.  2 . Tipping the clamp allows the lug  94  to clear the top edge  64  of aperture  60 . The clamp is then rotated as indicated by the arrow in FIG.  2 . As the clamp rotates it can also slide (to the right in FIG. 2) to fully seat the lug  94  in the aperture  60  in an interference fit. Bevel  90  provides clearance from the ledge  78  as this movement proceeds. Once the groove  92  of the clamp engages the shaft  20 , the retention bolt  98  is placed through bore  82 , shaft  20  and bore  96 . Tightening the nut  104  locks the second connector element  30  onto shaft  20 . The clamp and sill fit tightly about shaft  20 . The clearance for the bolt  98  in bores  82  and  96  is minimized so that the bolt is not subjected to backlash that could otherwise lead to premature fatigue failure of the bolt. 
     It will be understood that in cases where shaft  18  has sufficient flexibility it may be possible to connect a coupler at one end of the shaft  18  first and then finish the connection at the other end. Alternately, both ends of the shaft  18  could be lifted into place and clamped onto their respective adjoining shafts simultaneously. The important point is the couplers  10  allow the shaft  18  to be lifted into position even though the axial position of shafts  16  and  20  is essentially fixed. Some axial adjustment of the length of the drive train is afforded by varying the depth to which the cross piece  28  extends into the housing  54 . 
     One of the advantages of the coupler of the present invention is the single bolt locking method. Only bolt  98  is required to lock the clamp  84  on the sill. This reduces the number of parts and allows for relatively quick installation of the coupler. 
     While a preferred form of the invention has been shown and described, it will be realized that alterations and modifications may be made thereto without departing from the scope of the following claims.

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