Abstract:
Guide rollers for upward-acting track guided doors are formed of dual durometer plastic materials wherein a hub portion of the guide roller is formed of a relatively hard moldable plastic material having a durometer of about Rockwell R 120. A tire or tread is preferably molded over the hub and is characterized by a thermoplastic elastomer material, such as urethane, having a durometer of about 70 to 90 Shore A. A circumferential recess may be formed in the rim of the roller hub to receive a tread which is not molded over the full extent of the rim. The tire or tread may have an arcuate thin-walled, a somewhat elliptical or a circular segment shape in cross section. The guide roller provides for quiet long-lasting operation in guiding upward-acting sectional and one-piece garage doors and the like.

Description:
FIELD OF THE INVENTION 
     The present invention pertains to a dual durometer roller type guide member for use with upward-acting track guided garage doors and the like. 
     BACKGROUND OF THE INVENTION 
     Upward-acting track guided sectional and one piece garage doors are typically supported and guided for movement between their closed and open positions by plural roller type guide members which are mounted on the door side edges and which engage and traverse along opposed guide tracks. Such guide tracks are typically formed as somewhat channel shaped members which are manufactured of formed metal plate. Moreover, conventional roller type guide members are characterized by formed metal rollers mounted on metal shafts. These metal on metal guide structures for upward-acting residential garage doors and other types of doors tend to generate a substantial amount of noise during opening and closing movement of the door and also on occasions when substantial and variable wind loads act on the door. Such roller guide member generated noise is objectionable in most door installations and it is desirable to eliminate such noise and to provide for long lasting, low friction, vibration free and quiet operation of such doors. It is to these ends that the present invention has been developed. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved track guided door including roller guide members which are quiet and reliable in operation. 
     In accordance with one important aspect of the invention, an upward-acting track guided door is provided with roller guide members disposed in opposed guide tracks and which guide members are each provided with an elastomer tire or tread, respectively, to provide quiet, reliable operation when the door is moved between open and closed positions and when the door may be subject to deflection due to wind loads and the like while in the closed position, in particular. The roller guide members are preferably formed of dual durometer plastic construction including a thermoplastic hub over which is molded a thermoplastic elastomer outer layer forming the so-called tread or tire portion which is of a softer or lower durometer than the hub portion. The roller guide members are preferably formed by a molding process wherein the hub is formed in a first molding step, the mold is expanded or modified and the tread portion is molded over the hub in a second molding step without removing the hub from the mold structure. A strong bond between the hub and the tread is formed in the molding process. 
     In accordance with a further aspect of the present invention, a dual durometer roller guide member is provided for use with track guided and upward-acting doors, in particular, and wherein the guide member is formed of dual durometer construction including a thermoplastic hub having a durometer of about Rockwell R120, for example, and a thermoplastic elastomer tread which is molded over the hub and is of a durometer of about 70 to 90 Shore A. The hub and tread are both, preferably, formed of a suitable urethane compound wherein the hub and the tread are strongly bonded together. 
     In accordance with a still further aspect of the present invention, a dual durometer roller guide member is provided for use, in particular, with track guided upward-acting doors and wherein the roller is provided with a low durometer thermoplastic elastomer tread of a configuration which assures quiet and reliable operation while minimizing drag or friction forces between the rollers and the guide tracks and also avoiding the rollers undergoing lateral oscillation or “climbing” of the side walls of channel shaped guide tracks. 
     Those skilled in the art will further appreciate the above-mentioned advantages and superior features of the invention together with other important aspects thereof upon reading the detailed description which follows in conjunction with the drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a sectional upward-acting track guided door which includes roller guide members in accordance with the invention; 
     FIG. 2 is a detail perspective view of one of the guide members mounted on a support bracket which, in turn, is mounted on one of the door sections for the door shown in FIG. 1; 
     FIG. 3 is a longitudinal central section view taken generally along the line  3 — 3  of FIG. 2; 
     FIG. 4 is a detail section view showing the configuration of the over-molded tread or tire for one preferred embodiment of the guide roller of the present invention; 
     FIG. 5 is a view similar to FIG. 4 showing a first alternate embodiment of a guide roller in accordance with the invention; 
     FIG. 6 is a section view of a second alternate embodiment of a guide roller in accordance with the present invention; 
     FIG. 6A is a detail section view of a third alternate embodiment of a guide roller in accordance with the invention; and 
     FIG. 7 is a perspective view, in somewhat schematic form, showing a guide roller in accordance with the invention disposed within a mold which may be expanded to provide a two-step molding process for molding the hub and then the tread or tire of the guide roller. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In the description which follows, like parts are marked throughout the specification and drawing with the same reference numerals, respectively. The drawing figures are not necessarily to scale in the interest of clarity and conciseness. 
     Referring to FIG. 1, there is illustrated an upward-acting track guided door  20  disposed to move between a closed position shown covering an opening in a wall  26  and an open position guided and supported by opposed somewhat channel-shaped guide tracks  28  and  30 . The guide track  28  includes a channel-shaped recess  28   a  extending along a horizontal run portion  28   b  and a vertical run portion  28   c.  In like manner, guide track  30  is a mirror image of guide track  28  and includes a channel-shaped recess  30   a  which extends along a horizontal run portion  30   b  and a contiguous vertical run portion  30   c.  One preferred embodiment of a guide roller in accordance with the invention is indicated by numeral  32  in FIG.  1 . Each of the guide rollers  32  is supported in a suitable manner on spaced-apart support brackets to be described in further detail herein, which brackets are mounted on opposite lateral sides of plural sectional door panels  22 , respectively. The door panels  22  are delimited by opposite lateral side edges  22   a  and  22   b.  The panels  22  are also joined together by suitable hinges  23  and are delimited by longitudinal side edges  38  and  40 , respectively. The panels  22  may be reinforced by plural spaced-apart vertically extending support members or stiles  50 , as shown in FIG. 1. A suitable counterbalance mechanism  34  is operably connected to the door  20  by depending flexible cable type members  35  in a conventional manner. The door  20  may be of a type disclosed in my U.S. patent application Ser. No. 09/570,618 on May 15, 2000 and assigned to the assignee of the present invention. Moreover, the counterbalance mechanism may be of a type covered by U.S. Pat. No. 6,134,835 issued on Oct. 24, 2000 and also assigned to the assignee of the present invention. However, those skilled in the art will also recognize that the roller guide members  32  may be used on other types of sectional or single-piece track guided doors. 
     Referring now to FIG. 2, one of the guide rollers  32  is shown in a working position disposed within the channel-shaped recess  28   a  of track section  28   c.  In one preferred arrangement for the guide roller  32 , the roller is mounted on a support shaft  52  which is disposed in an elongated tubular support or bearing member  54  secured to and forming a part of a support bracket  56 . Support bracket  56  includes a base or web portion  57  and opposed parallel flanges  58  and  59  integrally formed with the web portion  57  and extending normal thereto. Tubular bearing member  54  may be formed as a separate member and suitably secured to the flanges  58  and  59  and extending through coaxial bores  58   a  and  59   a,  see FIG.  3 . As shown in FIG. 2, support bracket  56  is secured to a door panel  22  by suitable fasteners  60 , for example. Further details of the support bracket  56  may be determined from U.S. patent application Ser. No. 09/570,618, the subject matter of which is incorporated herein by reference. Each of the guide roller members  32  for the door  20  may be mounted in a similar manner. 
     Referring further to FIG. 3, by way of example, the track  28  defines the channel  28   a  by opposed diverging side walls  28   d  and  28   e  interconnected by a generally planar section  28   f  which is disposed opposite a substantially planar flange  28   g.  Flange  28   g  is joined to side wall  28   d  by a suitable web portion  28   h.  Track side walls  28   d  and  28   e  join section  28   f  by substantially constant circular radii which are somewhat larger than the radius of curvature, in cross section, of the outer surface of guide roller  32 . Moreover, the spacing between side walls  28   d  and  28   e  is sufficient to allow some longitudinal movement of guide roller  32  and support shaft  52  within the tubular bearing member  54 . 
     As further shown in FIG. 3, guide roller support shaft  52  includes an integral collar  52   a  and a stub-bearing portion  52   b  for supporting a hub  33  of guide roller  32 . Hub  33  includes a suitable bore  34  journaling the stub shaft  52   b.  Hub  33  is retained on support shaft  52  by a retaining washer  35  which, in turn, is retained on the shaft  52  by staking or coining the shaft end face  52   d  to enlarge same and retain the washer  35  thereon. Washer  35  is preferably mounted on a slightly reduced diameter portion  52   e  of stub shaft  52   b,  as shown in FIG.  3 . 
     Referring further to FIG.  3  and also FIG. 4, the roller hub  33  includes a circumferential radially extending web  36  integrally joined to an outer circumferential rim portion  38  and to a hub bearing portion  37 . As shown in FIG. 4, in particular, rim portion  38  has an outer convex arcuate surface  39  extending between spaced-apart circumferential shoulders  40  and  41 . A circumferential recess  42  is also provided in surface  39  and is substantially centered and aligned with the web  36 , for example. The radius of curvature of surface  39  is preferably constant and extends between the shoulders  40  and  41  and is interrupted only by the recess  42 . The hub  33  is preferably molded of a thermoplastic. A urethane composition having a durometer of approximately Rockwell R 120 is preferred. 
     Referring further to FIGS. 3 and 4, the roller  32  also includes a circumferential outer tire or tread  43  which has an arcuate outer surface  44 , FIG. 4, and extends between the shoulders  40  and  41 , as illustrated. The outer tread  43  is preferably secured to the hub  33  by molding the tread  43  over the rim  38  in a two-step molding process which forms both the hub and the tread. However, the tread  43  may be formed or placed over the rim  38  in a different manner. The thickness of the tread  43  may be varied. However, for a roller  32  having an outer diameter of about 1.75 inches, the thickness of the tread  43  may range from about 0.03 inches to 0.07 inches. The tread  43  is preferably formed of a rubber or thermoplastic elastomer (TPE) and having a durometer of about 70 to 90 Shore A. In a preferred manner of fabricating the roller  32 , the tread  43  is molded over the hub  33  without removing the hub  33  from a mold in which the hub itself was formed. The overmolding process assures a strong bond between the rim  38  of hub  33  and the tread  43 . 
     The extent of the arcuate surface  44  about its own axis is preferably about 180°, although the angular extent of the surface  44  may be less as will be explained in further detail in conjunction with an alternate embodiment of the invention. The cross section of the rim  38  and tread  43  may be symmetrical about a plane  45  centered in the web  36 , FIG. 4, although the tread may be formed asymmetrical about the centerline or plane  45 . Recess  42  may be relieved along lines  42   a  or  42   b  to intersect surface  39 , as indicated in FIG. 4, to facilitate molding the tread  43  over the rim  38 . 
     Referring briefly to FIG. 5, there is illustrated a guide roller  132  comprising a first alternate embodiment of the invention and modified as shown to form a rim  38   a  for a hub  33   a . A tread  43   a  is overmolded the rim  38   a  and is substantially like the tread  43  except the rim  38   a  has been modified to provide two opposed annular grooves  38   b  and  38   c  adjacent the shoulders  40  and  41  and effectively extending the axial extent of the shoulders  40  and  41 . Accordingly, when the tread  43   a  is molded over the rim  38   a , two annular reentrant flanges  43   b  and  43   c  are formed which may further enhance retention of the tread  43   a  on the rim  38   a . The configuration of guide roller member  132  may be preferred where the tread is not over molded on the hub of the roller. Thus, the reentrant flanges  43   b  and  43   c  aid in retaining the tread on the roller hub. 
     Referring now to FIG. 6, a second alternate and also preferred embodiment of a guide roller in accordance with the invention is illustrated and generally demonstrated by the numeral  70 . The guide roller  70  is provided with a hub  72  including an axial bore  74  for receiving a stub shaft  52   b , not shown, on a support shaft  52 , also not shown, whereby the roller  70  may be retained on such support shaft in the same manner as the rollers  32  and  132 . Hub  72  includes a circumferential radially extending web portion  76  integrally formed with a circumferential rim  78  having an arcuate outer surface  79 . As further shown in FIG. 6, a somewhat elliptical cross-section shaped tread or tire  80  is disposed in a circumferential recess or groove  81  formed in the rim  78 . The tread  80  is also preferably molded over the rim  78  of the hub  72  and is exposed to the exterior surface  79  of rim  78  within an included angle X, FIG. 6, of about 60° to 90° with respect to the center  83  of the cross sectional shape of the rim  78  as defined by arcuate surface  79  whereby the tread or tire  80  does not extend over an arc as great as the tread or tire of the rollers  32  or  132 . In this way, the relatively soft tire or tread  80  may be less likely to frictionally engage the side walls  28   d  or  28   e  of the track  28  (as well as the same or corresponding side walls of the track  30 ) so that there is less drag on the door operator and less tendency for the roller  70  to oscillate or tend to move in a lateral manner with respect to the tracks, which manner would be moving axially of the central axis of rotation  77  for the roller and the shaft  52 , for example. The hub  72 , web  76 , rim  78  and the tread or tire  80  may be formed of the same or similar materials as provided for the hub and tread of the roller  32 . 
     Referring briefly to FIG. 6A, a further modification of a guide roller in accordance with the invention is illustrated and generally designated by the numeral  70   a . The roller  70   a  includes a modified hub which includes a radially extending web portion  76   a  and a rim  78   a  in which a somewhat circular segment shaped notch or recess  81   a  is provided in a circumferential manner. The rim  78   a  includes a somewhat circular cross sectional shape having a center at  83   a  which is coincident with a plane passing through the center of the web  76   a  as indicated at  76   p.  Center  83   a  preferably coincides with the center of arcuate surface  79   a  of rim  78   a . The angle X is defined about the plane  76   p  and the center  83   a  and may range between about 60° to 90°, thus defining the sidewalls of the recess  81   a , as shown. A thermoplastic elastomer tire or tread  80   a  is molded over and bonded to the rim  78   a  within the recess  81   a.    
     Referring briefly to FIG. 7, a further modified roller  32   a  is shown disposed in a suitable multi-part mold  90  which may be placed in a first position to form a mold cavity which is delimited by surfaces which will only form the hub  33   b  of the roller  32 , for example. However, the mold  90  may be expanded, after molding the hub  33   b,  such that a mold cavity space is provided corresponding to the space occupied by a tread  43   d.  After the mold  90  is expanded to provide the molding space corresponding to that required to form the tread  43   d,  tread-forming material is injected into the mold and is thus integrally joined or bonded to the previously molded hub  33  so that the roller  32   a  does not require removal from the mold until the hub and the overmolded tread are formed. Moreover, a superior bond may be provided between the tread  43   d  and the hub  33   b  of the guide roller  32   a  since, for example, the overmolding process may take place only shortly after the hub material solidifies in the process of molding the hub. All embodiments of the guide roller of the present invention may be molded in generally the same manner. 
     The construction and operation of the guide rollers disclosed herein and shown in the accompanying drawing figures may be carried out as described and which is believed to be sufficient to enable those skilled in the art to practice the invention. Although preferred embodiments have been disclosed in detail herein, those skilled in the art will recognize that various substitutions and modifications may be made without departing from the scope and spirit of the appended claims.