Abstract:
An elastomer coupling ( 20 ) including an outer member ( 40 ) including a leading contact face ( 38 ), and an elastomer component ( 30 ) including a driving elastomer contact face ( 41 ) opposing and adapted for operable unbonded contact with said leading contact face ( 38 ), the driving elastomer contact face ( 41 ) including a thin polyurethane coating ( 50 ). In another aspect, the elastomer coupling ( 20 ) has an elastomer member ( 30 ) preferably having a plurality of parallel-sided bonded lugs (47) having thin elastomer driving and following skins ( 46, 46′ ) received in preferable line fit relationship in a plurality of parallel-sided recesses ( 44 ) formed in a preferably plastic outer member ( 40 ) for transmitting torques, accommodating slight parallel and angular misaligninents, and isolating vibrations thereof.

Description:
FIELD OF THE INVENTION 
     The invention relates to torsional couplings. More particularly, the present invention is directed to an elastomer coupling for use in a drive train. 
     BACKGROUND OF THE INVENTION 
     Elastomer drive couplings are transmission devices that connect between a driving member and a driven member, such as in a drive train, to provide misalignment accommodation, torque carrying capability and appropriate stiffness for vibration isolation. Couplings are used, for example, in a drive train between an engine and a unit to be rotated, such as a compressor. The torsional stiffness of the coupling is designed to minimize torsional vibrations that may cause damage to the drive train components. 
     Examples of prior art couplings can be found in U.S. Pat. No. 2,444,904 to Worley, U.S. Pat. No. 2,504,750 to Strachovsky, U.S. Pat. No. 4,050,266 to Bergman, U.S. Pat. No. 3,321,935 to Wildhaber, U.S. Pat. No. 3,183,684 to Zeidler, U.S. Pat. No. 4,240,763 to Moore, U.S. Pat. No. 4,913,671 to Gavriles and U.S. Pat. No. 5,435,784 to Mark. 
     Certain ones of these prior art couplings have general deficiencies in performance and/or durability. For example, in the spider coupling described in the &#39;784 Mark patent, the rubber blocks  24  are not bonded to the inner member lugs  22 , thus they do not effectively transfer loads to the outer member drive ring  10 . Further, the rubber blocks  24  will have the tendency to abrade against the drive ring&#39;s trapezoidal openings  14  due to slight angular and/or parallel misalignment. As a result, the drive train including the Mark&#39;s &#39;784 device must be torn down periodically in order to replace the rubber blocks  24 . Accordingly there has been a long felt, and unmet need for a coupling capable of transmitting large torques, accommodating misalignments and which exhibits extended durability such that replacement intervals are decreased. 
     SUMMARY OF THE INVENTION 
     The present invention provides an elastomer coupling which includes a rigid outer member and an elastomer component cooperative therewith which exhibits excellent durability. The durability improvement is provided by adhering a thin polyurethane coating on an elastomer contact face of the elastomer component. According to the invention, the coupling includes an outer member having a leading contact face, an elastomer component including a driving elastomer contact face, where the elastomer contact face includes a thin polyurethane coating. 
     In a preferred aspect, the elastomer component includes a rigid inner member having a plurality of radially directed rigid spokes including thin elastomer bonded skins, thus forming a plurality of bonded lugs. Each of the lugs preferably includes parallel surfaces formed thereon. The outer member, which is preferably plastic, includes a plurality of radial recesses formed therein, each including a leading contact face and an opposing trailing contact face. The plurality of bonded lugs are received, preferably in a line fit relationship within the recesses thereby accommodating slight angular and parallel misalignments, yet providing the ability to carry significant torque loads. The inventors herein determined that the durability of the skins on the bonded lugs is dramatically improved by adding the polyurethane coating. Moreover, the coating has the benefit of minimizing lubrication throw-off, such as is experienced on prior art couplings utilizing grease or oil lubrication. 
     In accordance with another aspect of the invention, an elastomer coupling is provided which comprises an outer member including a thin flange radially extending from a thicker central section, the thicker central section including a plurality of recesses formed therein each having leading and trailing contact faces, each of said plurality of recesses having a thickness dimension, and an elastomer component having an inner member with a hub including a radially peripheral surface and a plurality of radially directed spokes emanating therefrom, the spokes including preferably parallel surfaces formed thereon, driving and following thin elastomer skins of substantially constant thickness bonded to said parallel surfaces thus forming a plurality of bonded lugs each including driving and following contact faces and having a thickness dimension being substantially equal to said comparable dimension of the recesses such that the plurality of bonded lugs are preferably received in said plurality of recesses in close (line) fit relationship, and preferably a friction reducing polyurethane coating applied at least to the contact surfaces of the plurality of bonded lugs. 
     In accordance with another aspect, a coupling is provided which comprises an outer member including a thin flange radially extending from a thicker central section, said central section including a plurality of recesses formed radially therein each having preferably parallel leading and trailing contact faces, each said recess having a thickness dimension, and a bonded component including an inner member having a hub including a radially peripheral surface and a plurality of radially directed spokes emanating therefrom, the spokes preferably including parallel surfaces formed thereon, driving and following thin elastomer skins of preferably substantially constant thickness bonded to the parallel surfaces, thus forming a plurality of bonded lugs having a thickness dimension being preferably substantially equal to the thickness dimension of the recesses such that the plurality of bonded lugs are received in the plurality of recesses in preferable close (line) fit relationship. 
     In accordance with another aspect of the invention, a method is provided for improving the durability of an elastomer coupling, comprising the steps of providing a first member including a first contact face, providing an elastomer component including an elastomer contact face opposing and adapted for operable contact and movement relative to the first contact face, and applying a thin polyurethane coating to said elastomer contact face. Preferably, the coating is applied over a suitable adhesive and processed according to a method prescribed herein. 
     The coupling advantageously provides improved durability as compared to prior art couplings. 
     Moreover, the coupling advantageously provides high torque carrying capacity while exhibiting light weight. 
     Moreover, the coupling advantageously provides minimal debris throw-off during rotation. 
     The above-mentioned and further features, advantages, and characteristics of the present invention will become apparent from the accompanying descriptions of the preferred embodiments and attached drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will become better understood by reference to the description that follows, in conjunction with the appended drawings, in which: 
     FIG. 1 is a frontal view of an elastomer coupling in accordance with the present invention; 
     FIG. 2 is a sectioned side view of the coupling of FIG. 1 taken along line  2 — 2 ; 
     FIG. 3 is a frontal view of the elastomer component in accordance with the present invention; 
     FIG. 4 is a sectioned side view of the elastomer component of FIG. 3 taken along line  4 — 4 ; 
     FIG. 5 is a sectioned end view of a bonded lug of the elastomer component of FIG. 3 taken along line  5 — 5 ; 
     FIG. 6 is a frontal view of the inner member in accordance with the present invention; 
     FIG. 7 is a sectioned side view of the inner member of FIG. 6 taken along the line  7 — 7 ; 
     FIG. 8 is a frontal view of the outer member in accordance with the present invention; and 
     FIG. 9 is a sectioned side view of the outer member of FIG. 8 taken along line  9 — 9 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An elastomeric coupling  20  according to the invention is first illustrated in FIGS. 1 and 2. This type of coupling  20 , generally referred to as a spider coupling, provides a very high torsional stiffness, generally in excess of about 100,000 lbf-in./radian (11,300 N-m/radian). The coupling  20  in accordance with the present invention includes an outer member  40  and an elastomer component  30  inserted in close (line) fit relationship therein. Preferably, the elastomer component  30  is coated to extend its durability, as will be described later herein. As best shown in FIGS. 1-2 and  8 - 9 , the rigid outer member  40  preferably includes a thin flange  42  extending radially outward from a thicker central section  36  and to preferably intersect an outer circumferential rim  33 . The central section  36  includes a plurality of equally-spaced recesses  44 , each extending in a radial direction and preferably including substantially parallel leading  38  and trailing  38 ′ contact faces. A plurality of radially extending tapered stiffening ribs  31  extend radially from the central section  36  and thinning down towards the outer rim  33  and provide enhanced rigidity to the preferably plastic outer member  40 . 
     The central section  36  also includes radially extending recess ribs  39  upon which the contact faces  38 ,  38 ′ are formed, tangentially extending recess ribs  43 , and an inner rim  45  which completely surrounds the recesses  44 . Each tangentially extending recess rib  43  attaches between respective ones of the at the inboard ends of radially extending recess ribs  39  to stiffen same. Likewise, the inner cylindrical rim  45  attaches to each of the radially extending recess ribs  39  at their outboard ends to add additional strength. Thin planar ribs  51  provide additional structural radial support between the tangential rib  43 , radial ribs  39  and inner rim  45 , further strengthening the outer member  40  adjacent to the recesses  44 . In an outer member  40  also includes a plurality of blind attachment holes  60  around the outer rim  33  for securing to the drive train component (not shown). Blind holes  60  provide for ease of assembly of attachment bolts (not shown). The recesses  44  preferably includes a pocket cross dimension t 2  which is substantially equal to the lug thickness t 1  of the bonded lug  47  (FIG. 5) such that a preferable close fit is accomplished. The preferred close fit that is accomplished is a conventional line-to-line fit well known in the relevant art. The line fit is desired to minimize backlash in the coupling as zero torque is encountered. 
     A line fit relationship means that the dimensions of the lugs  47  are such that in the theoretical case, the lug faces  41 ,  41 ′ are just in contact with the recess faces  38 ,  38 ′. However, it should be understood that, in reality, tolerance stack ups may provide for a very slight gap or a very slight squeeze fit. The preferable material for the manufacture of the outer member  40  is plastic, such as RYNITE  530  manufactured by Dupont. This dramatically minimizes the weight of the coupling. It should be understood that reducing the rotational inertia of the drive line is desirable. However, other suitable plastic materials could be used as well. A smooth finish on the leading and trailing edges  38 ,  38 ′ is most desirable. As discussed hereinbefore, the faces  41 ,  41 ′ are preferably parallel and the recess faces  38 ,  38 ′ are also preferably parallel. This ensures that during torque transmission, that radial forces are minimized to the plastic outer member  40  which may be detrimental to its durability. 
     As best shown in FIGS. 3-7, the elastomer component  30  preferably includes a rigid, preferably cast iron, inner member  32  having a cylindrical hub  34  including a radially peripheral surface  35  and axially cored-out portions  54 . Cored-out portions  54  reduce the weight of the hub  34 . A plurality of thin, equally-spaced, radially directed rigid spokes  37  emanate from the hub  34 . A central axial through bore  55  is provided for attachment to a drive shaft (not shown). Generous radii  57  are applied at the base of each spoke  37  to reduce stress concentrations. Moreover, steps  59  are provided for ensuring a generous skin of elastomer on the axial edges  53  of spokes  37 . Holes  65  may be included for orientation in the mold during bonding. Elastomer  49 , such as a natural rubber, a natural rubber blend or other suitable elastomer material, is integrally bonded to leading and trailing spoke surfaces  48 ,  48 ′ of the spokes  37  of inner member  32  as best shown in FIGS. 3-5. This forms the plurality of bonded lugs  47 . The leading contact faces  41  of the elastomer component  30  cooperate with the leading contact faces  38  of the outer member  40  to carry the torque T. 
     Preferably the elastomer  49  used in the elastomer component  30  exhibits a durometer of between about 45 and 75 durometer, Shore A, and more preferably about 56-60 Shore A. During the vulcanization/bonding operation, a plurality of elastomer skins  46 ,  46 ′ of substantially constant thickness t 3  are vulcanized bonded to the leading and trailing surfaces  48 ,  48 ′ via a transfer or injection molding operation. Moreover, the elastomer  49  at the axial edges of spokes  37  is also preferably bonded to the spokes  37 . Additionally, a thin tangential skin  52  of elastomer  49  is preferably also bonded to the radially peripheral surface  35  of the inner member  32 . The tangential skin  52  interconnects the elastomer skins  46  and  46 ′ bonded to the leading and trailing surfaces  48  and  48 ′ of spokes  37 . The overall thickness of the bonded lugs  47  is designated t 1 . The thickness of each lug is substantially constant. Notably, the width w of the bonded lugs  47  are at least 2 times their thickness t 1 . This provides substantial load carrying area such that the elastomer skin  46  or spoke  37  is not overstressed. 
     By way of example, and not to be considered limiting, the thickness of the driving and following skins  46 ,  46 ′ are between 0.04 inch (1.02 mm) and 0.2 inch (5.08 mm) and most preferably about 0.125 inch (3.18 mm). The bonded component  30  includes an axial through bore  55  which interconnects to a power transmission shaft (not shown). Axially extending broached key way  58  accepts key (not shown) to prevent rotation of the bonded elastomer component  30  relative to the drive shaft (not shown). Two threaded holes  56  and  56 ′ which are radially formed in the hub  34  after the bonding operation accept set screws (not shown) to secure the component  30  to the shaft (not shown). The threaded holes intersect the keyway  58  so that the set screws are permitted to pass through the holes until the ends of the screws contact the key. In this way, the key is maintained in the keyway during use of the coupling. 
     Applied to and adhered at least on the driving elastomer contact face  41  of the plurality of driving elastomer skins  46  on lugs  47 , and more preferably on all elastomer contact surfaces  41 ,  41 ′ of elastomer  49 , is a friction-reducing thin polyurethane coating  50 . This polyurethane coating  50  is preferably applied over a suitable adhesive applied to the driving and following elastomer contact faces  41 ,  41 ′. By way of example, and not to be considered limiting, the preferable coating is a CHEMGLAZE® Z320A/B system which is a two-component, high performance polyurethane slip coating available from Lord Corporation of Erie, Pa. The coating is preferably applied over a halogenated polyolefin containing adhesive, such as CHEMLOK® 252X High Performance One-Coat Adhesive, also available from Lord Corporation. First, the exposed elastomer surfaces of the elastomer component  30  are solvent wiped, such as with Methyl Ethyl Ketone (MEK) and allowed to dry. Next, CHEMLOK® 252X is sprayed onto the elastomer component  30  at approximately 0.5 mils (0.0127 mm) dry film thickness. The elastomer component  30  is then oven cured for 5 minutes at approximately 300 degrees F. (148 degrees C.). A spray coating of polyurethane coating CHEMGLAZE® Z320A/B is then applied to the primed components  30  at approximately 1.2 mils (0.0305 mm) dry film thickness. Finally, the coated component  30  is oven cured for an additional 10 minutes at 300 degrees F. (148 degrees C.). It was determined by the inventors that coating the driving elastomer contact face  41  of the elastomer component  30  with this polyurethane coating dramatically enhanced its durability. The coating is found to be particularly effective in the spider coupling  20  in accordance with another aspect of the invention. Moreover, the use of the coating appears to be particularly advantageous when the elastomer component  30  is used with a plastic outer member  40 . 
     The invention has been described in terms of preferred method steps and structure, however, the particular examples given are meant to be illustrative and not limiting. Substitutions and equivalents as will occur to those skilled in the art are included within the scope of the invention as defined by the following claims.