Patent Publication Number: US-2022235597-A1

Title: Tensioning device for a drive train

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to a tensioning device used in the drive train of a door opening system. 
     BACKGROUND OF THE INVENTION 
     The use of tensioning devices with a drive train are generally well known. One area of application for a tensioning device is part of a drive train for a door operating system, such as for a garage sectional door. The door is generally moved between open and closed positions by a door operator, which drives a belt or chain that is attached to a trolley that runs forward and backward along a track or rail mounted to the garage ceiling, with the trolley attached to the door via a closure arm. Over time, continued movement of the trolley back and forth along the track during door opening and closing operations can lead to a slackening in the belt or chain through wear, leading to excessive movement of components of the drive train, thereby creating noise and possibly causing damage. 
     When the above issue is encountered, the belt or chain is generally tensioned by adjusting a belt or chain tensioner provided as an adjustment bolt until the tension in the belt or chain is sufficient to overcome the above issues. However, adjustment of the tensioning device is often inconvenient due to the conventional positioning of the tensioning device proximate the wall above the door, with the adjustment bolt usually positioned very close to the wall, outboard from the idler pulley, and thus difficult to access. 
     It is known for such tensioning devices to include a spring, the coils of which surround the shank of the adjustment bolt, with the spring serving as a shock absorber when the belt or chain experiences sudden or excessive loading that can sometimes occur during initiating or halting opening or closing of the door. In these applications, the spring is generally pre-loaded when the level of tension in the belt or chain is being set. However, it is important that the spring is still able to compress and thus provide resilient resistance during operation in order to provide shock absorption. 
     It is desirable to provide a tensioning device that addresses at least in part one or more of the above problems with conventional tensioners, or provides a useful alternative to the known tensioners. 
     Reference to any prior art in the specification is not an acknowledgment or suggestion that this prior art forms part of the common general knowledge in any jurisdiction or that this prior art could reasonably be expected to be understood, regarded as relevant, and/or combined with other pieces of prior art by a skilled person in the art. 
     SUMMARY OF THE INVENTION 
     In a first aspect, the present invention provides a tensioning device for a door operating system, the door operating system including a track, a longitudinal drive component to be tensioned, the longitudinal drive component running along the track between a track door end and a track operator end, a powered operator arranged to drive the longitudinal drive component and a pulley configured to operatively engage the longitudinal drive component adjacent the track door end, the tensioning device including: a pulley carriage on which the pulley is mounted for rotation, the pulley carriage being movable relative to the track; an adjuster configured to move the pulley carriage relative to the track and thereby alter a level of tension in the longitudinal drive component, the adjuster of the tensioning device being accessible from an end of the tensioning device facing said track operator end; and a resilient member operatively engaged with the adjuster, the resilient member configured to provide damping of forces experienced by the longitudinal drive component. 
     Advantageously, the longitudinal drive component (belt, chain, or other suitable transmissive component), can be tensioned by a user in a simpler manner than is conventional because the adjustment means of the tensioning device is provided on the end facing the track operator end, rather than at an end facing the track door end, where a user generally has a very limited amount of space to access the adjuster and effect adjustment. 
     Preferably, the adjuster includes a drive part for manipulation by a user to effect the adjustment, the adjuster drive part being disposed at a position on the side of the pulley carriage towards the track operator end, in order to render it accessible from an end of the tensioning device facing said track operator end. In a preferred form the adjuster drive part is a head of an adjustment bolt or screw, rotation of which (eg. by way of a suitable tool) effects adjustment of the level of tension in the longitudinal drive component. 
     The resilient member is preferably a spring, particularly a compression spring. However, the resilient means may be of any other suitable form capable of absorbing and releasing load transferred thereto. For example, in certain embodiments the resilient means may be a tension spring or torsion spring, or may be formed of a body of a polymer or rubberised material, configured to provide the required resilience. 
     The pulley carriage preferably includes a surface on which the load from the adjuster bears in order to move the carriage. The carriage may include lateral portions that engage with the track to facilitate axial movement of the carriage along the track, while preclude substantial movement of the carriage in any other direction. These lateral portions may be provided as wings or outriggers to minimise material and therefore weight, sized and shaped to suit the dimensions of the track. 
     The adjuster is preferably an adjustment bolt engaging with a threaded element mounted in a fixed position relative to the track, rotation of the adjustment bolt in a tightening direction bearing on the resilient member, which bears on the carriage. The adjustment bolt may bear on a bearing element such as a plate, which in turn bears on the resilient member. 
     In a preferred embodiment, the belt tensioning device further comprises a retention structure disposed between the carriage and the adjuster, the retention structure configured to confine the resilient member. The retention structure can be of any suitable form that acts to confine the resilient member to its operating position between the adjuster and the carriage. For example, the retention structure may be a housing in which the resilient member is contained. In another example, the retention structure may be a cage formed of multiple bars that extend around the resilient member in order to confine it in its operating position. In another form, the retention structure need not be external of the resilient member, but may pass wholly or partially within the resilient member (such as within the coils of a compression spring). The retention structure may be a separate part disposed between the carriage and the adjuster, and may be mountable to the carriage so that it moves therewith. Alternatively, the retention structure may be formed as part of the carriage and/or the adjuster. 
     As will be understood, the retention structure prevents the dislodgement or disengagement of the resilient member from its operating position, thus ensuring optimum operation of the device and minimising safety risks which might otherwise arise. 
     In an embodiment, the retention structure is configured to afford a visual indication of the loading of the resilient member, thus providing to a user an indication of the level of tension in the belt. The user is therefore able to monitor the preload of the resilient member at installation or on any subsequent visual inspection, for example as part of a regular maintenance check, and adjust it to always ensure an optimum level of shock absorption. As will be understood, an unsuitably low preload will generally indicate insufficient belt tension, while an unsuitably high preload will generally indicate that the belt is overloaded, and the resilient member not able to afford shock absorption. 
     The adjustment bearing element (such as a plate on which the adjuster bears) may be disposed within the retention structure. Visual inspection of the position of the adjustment bearing element within the retention structure can thus provide an indication of loading in the resilient member. 
     The indication of loading in the resilient member, which is afforded by a visual inspection of the retention structure, can be provided in many different ways. For example, the retention structure may include one or more openings that allow a user to view the resilient member or a part operatively engaged with the resilient member (such as said adjustment bearing element). In another embodiment, the retention structure may be wholly or partially transparent, allowing a user to visually inspect the loading in the resilient member. 
     In a further embodiment, the device may include an indicator element in operative engagement with the resilient member, the indicator element extending from the retention structure, with movement of the indicator element providing to a user a measure of the loading of the resilient member. In this way, the resilient member need not be visible. For example, the indicator element may comprise a pointer moving relative to a graduated scale on the retention structure. Alternatively, the visual indication may be provided electronically, such as via an encoder in operative engagement with the resilient member. 
     The tensioning device may include a chassis, wherein one or more component parts of the tensioning device are provided on the chassis, the chassis being configured to be mounted to the track. The chassis may be arranged for attachment to the wall defining the opening for which the door provides closure, e.g. by way of a mounting bracket. 
     In a second aspect, the present invention provides a door operating system including the tensioning device of the first aspect. 
     In an embodiment, the door operating system includes a motor powered operator configured to drive said longitudinal drive component. 
     As used herein, except where the context requires otherwise, the term “comprise” and variations of the term, such as “comprising”, “comprises” and “comprised”, are not intended to exclude further additives, components, integers or steps. 
     Further aspects of the present invention and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, given by way of example and with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  provides a perspective view of a door operating system; 
         FIG. 2  provides a bottom perspective view of a tensioning device in accordance with an embodiment of the present invention; 
         FIG. 3  provides a partly exploded bottom perspective view of the tensioning device of  FIG. 2 , depicting the various components; and 
         FIG. 4  provides a bottom view of another embodiment of the tensioning device installed to a track for mounting in a door operating system. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  illustrates a door operating system  1  installed in a garage to drive a door  2  between open and closed positions. A closure arm  4  connects the door  2  to a closure drive assembly. The closure drive assembly includes a motor operator  6 . The motor of operator  6  is arranged to drive a longitudinal drive member in the form of a drive belt  8 , arranged in a closed loop arrangement within or around a track  9 , which extends between the door  2  and the operator  6 . A drive device for the closure drive assembly in the form of trolley  3  moves along the track  9  and is connected to the closure arm  4 . Mounted above the door  2  and received at the door end of track  9  is a belt tensioner  10 . The belt tensioner  10  is configured to receive the belt  8  and allow a user to set and adjust the level of tension in the belt  8 . 
       FIGS. 2 and 3  illustrate a belt tensioner  10  in accordance with an embodiment of the present invention. It will be appreciated that  FIGS. 2 and 3  illustrate a view from a lower side of the belt tensioner  10  when in situ, i.e. mounted to a ceiling of a garage. Belt tensioner  10  includes a chassis  20  configured to be mounted to the track  9  at the door end thereof (see further below). The chassis  20  comprises a horizontal planar top web  21 , having a front portion  22  and a rear portion  23 . It will be understood that the front portion  22  faces the door  2 , whilst the rear portion  23  faces the operator  6 . A pair of lateral flange portions  24  extend downwardly and substantially perpendicular to the web  21 , the chassis  20  thereby defining a substantially C-shaped channel with rounded flange corners as shown. 
     Chassis  20  is sized to fit within track  9  (as discussed further below with reference to  FIG. 4 ), and may be formed in any conventional manner. For example, chassis  20  may be formed as an extruded section, formed by bending of an appropriate sheet material into the substantially C-shaped channel, or by welding the flange portions  24  to the top portion  21 . An aperture  25  is provided in each lateral flange portion  24  towards the front portion  22  of the chassis  20 . The apertures  25  are configured to receive fastening elements (not shown) that allow the chassis  20  to be mounted to a wall or other structure, generally above the door, by way of a suitable mounting bracket. The mounting of chassis  20  also provides support for the door end of track  9  as, once assembled, chassis  20  in effect forms a terminal extension of the track. 
     The rear portion  23  of chassis  20  includes an edge  26 , from which downwardly and perpendicularly extends a shaped planar tab  32  as shown in  FIGS. 2 and 3 . The tab  32  has an inner surface  33  facing towards the front portion  22  of the chassis  20 , and an outer surface  34  facing the operator  6 . The tab  32  is formed by bending downwardly a protruding portion of horizontal planar top web  21 , with reinforcing gussets pressed into the fold line as shown. Extending in a perpendicular direction and towards the front portion  22  from the inner surface  33  is an annular boss  35 . Annular boss  35  is integral with or welded to tab  32  and has a threaded inner bore, which extends to outer surface  34  of the tab  32 , thereby defining a passage for an adjustment bolt  36  to engage therein, as shown in  FIGS. 2-4 . Once the tensioner device is assembled in track  9 , clockwise rotation of the hex head of adjustment bolt  36  advances the bolt in the direction of door  2 . Adjustment bolt  36  is configured to engage other components of belt tensioner  10  as discussed below. 
     Chassis  20  further includes lateral hooked tabs  27  extending from the front portion  22  of each flange portion  24 , inboard of apertures  25 . The hooked tabs  27  have a first part  28  extending outwardly and perpendicular to an outer surface of each flange portion  24  and a second part  29  extending in a longitudinal direction towards the rear portion  23  from first part  28 , as shown. Lateral hooked tabs  27  are configured to receive the leading edges of the lateral flanges of track  9  at a position that leaves clear apertures  25 , hence ensuring the track does not interfere with the mounting of the chassis to the wall. The hooked tabs  27  are formed by stamping and folding from flange portions  24 . 
     The belt tensioner  10  further comprises a carriage  40  to support idler pulley  70  for rotation; carriage  40  configured to move in the axial direction relative to chassis  20  when adjusting the level of tension in the belt, but constrained against movement in any other direction. Idler pulley  70  includes a profiled circumferential groove  72  that receives the belt (as is conventional in the art) and rotates by way of suitable bearings on a shaft  56 , disposed vertically when in situ. 
     When viewed laterally, carriage  40  has a U-shaped form (see  FIG. 3 ), comprising an upper carriage portion  50 , a lower carriage portion  60  and an intermediate web providing force-receiving member  66 , all three portions cut and folded from a single sheet of material. The open end of the U-shaped form allows idler pulley  70  to be inserted during assembly of the device between carriage portions  50  and  60 . 
     Upper portion  50  is provided by a substantially planar body, comprising a pair of laterally extending shaped parts  53  and a bridging part  54  extending in the axial direction between parts  53 . Thus, the upper portion is substantially ‘I’ shaped as best shown in  FIG. 3 . The upper portion  50  also includes a rectangular aperture  58  for receiving an upper rectangular end  57  of shaft  56  on which idler pulley  70  rotates. When in situ, the shaped lateral ends of parts  53  are in close proximity to the inner surface  16  of flange portions  24 , affording smooth movement of the upper portion  50  in the axial direction, whilst preventing any substantial transverse movement. 
     The lower carriage portion  60  similarly includes an elongate body portion  61  having a front end  62  and a rear end  63 . The body portion  61  is of substantially rectangular form extending to transversely extending opposed wings  64  that project laterally from the body portion  61  at each end. The wings  64  are each contoured in a substantially S-shape in order to complement the shaping of the inner channels of track  9 . Like laterally extending parts  53  of upper portion  50 , wings  64  facilitate the axial movement of the carriage  40  (and therefore idler pulley  70 ) relative to the track, precluding any lateral movement or yaw of carriage  40 . Lower carriage portion  60  also includes an aperture  65  for receiving a lower end of shaft  56 . 
     Connecting rear end  62  of body portion  61  with the rear end of upper carriage portion  50  is an intermediate web forming force-receiving member  66 , the outer face of which faces the rear portion  23  of chassis  20  when assembled. As described further below, the force provided by the adjustment bolt  36  is ultimately transmitted to carriage  40  via force receiving member  66 , thereby driving axial movement of the carriage  40  relative to the track  9  towards the front portion  22  of chassis  20 . 
     Assembly of carriage  40  involves inserting bearing shaft  56  through idler pulley  70 , and then inserting pulley  70  into carriage  40  to locate the ends of shaft  56  into the apertures of upper and lower carriage portions  50 ,  60 . As  FIG. 3  illustrates, shaft  56  is formed such that it projects no more than a minimum distance beyond the outer surfaces of the upper and lower portions  50 ,  60  of carriage  40 , which might otherwise interfere with smooth lateral displacement of the device within chassis  20 . In the assembled state, it is important that relative movement between the component parts of the carriage  40 , the idler pulley  70  and shaft  56  is precluded, other than rotation of pulley  70  on vertical shaft  56 . 
     Interposed between the adjustment bolt  36  and the carriage  40  is an intermediate assembly  80 . Intermediate assembly  80  is configured to receive load provided by adjustment bolt  36  and transmit that load to carriage  40  to move the carriage  40  in the longitudinal direction towards the front portion  22  of chassis  20  when an increased level of tension in the belt is required. 
     The intermediate assembly  80  includes a hollow retainer housing  82  of generally cuboid form configured to retain a compression spring  83  in the space therein, as shown in  FIGS. 2 and 4 . The retainer housing  82 , when viewed in situ ( FIG. 2 ) is formed of a lower wall  84 , a pair of side walls  85  extending upwardly and in a perpendicular direction from the lateral edges of lower wall  84 , and a rear wall  86  that extends upwardly and in a perpendicular direction from the lower wall  84  from a rear edge thereof. The rear wall  86  includes an opening  87  (see  FIG. 4 ) to provide passage for the threaded shank of adjustment bolt  36 . 
     Opposite the rear wall  86  is an opening  90  provided by the substantial absence of a wall at the front side of the retainer housing  82  (see  FIG. 3 ) that allows insertion of spring  83  into the retainer housing  82  on assembly of the device. Once the device is assembled, the spring  83  sits in contact with the force bearing surface of force bearing member  66 . In an alternative embodiment, retainer housing  82  may include a front wall, with the spring  83  inserted in the retainer housing  82  through the opening opposite the lower wall  84  (provided by the substantial absence of a wall at the top side). Retainer housing  82  includes a pair of hooked lugs  81  ( FIG. 3 ) which extend from side walls  85  and in an axial direction. These lugs are configured to engage with carriage  40 , through a pair of corresponding apertures in carriage  40 , thereby fixedly connecting the intermediate assembly  80  to carriage  40  for movement therewith. 
     The retainer housing  82  therefore provides a retention structure for spring  83 , ensuring that the spring does not dislodge from its operational position during use. It will be readily appreciated that the spring may be retained in position in suitable ways other than by retainer housing  82 . It will further be appreciated that intermediate assembly  80  need not be provided as a separate component, but may be part of or attached to carriage  40  or chassis  20  in a suitable manner. Operably connected with the spring  83  is a rectangular plate  88 , which provides an adjustment bearing element. In the assembled belt tensioner  10 , the end of the threaded shank of adjustment bolt  36  bears on one face of plate  88 , while the end of spring  83  bears against the opposite face. When the adjustment bolt  36  is screwed inwardly (i.e. towards the front portion  22  of chassis  20 ), plate  88  acts to compress spring  83  which in turn transmits the load onto force receiving member  66 . This urges carriage  40  towards the front portion  22  of chassis  20 , thus increasing the tension in belt  8 . 
     Intermediate assembly  80  thus acts as a shock absorber between adjustment bolt  36  and carriage  40 , spring  83  absorbing any sudden jolts experienced by the belt when the door is moving between open and closed positions (particularly at starting and stopping of operator  6 ). In order for the spring to provide a sufficient level of shock absorption, the spring must be able to compress resiliently. Thus, during initial tensioning of the belt (or during further tensioning adjustments of the belt), it is important that the spring  83  is sufficiently preloaded, but not compressed beyond a threshold limit in order to allow it to provide the required shock absorbing function. For this purpose, the housing  82  provides a visual indication of the level of compression of the spring  83 . 
     Reference is now made to  FIG. 4 , which illustrates the belt tensioner  10  received in the track  9 . It will be appreciated that adjustment bolt  36  (and particularly the hex head of the bolt  36 ) is positioned within track  9  between the track rails provided by the surfaces of the inner channels thereof, accessible from the rear side (i.e. the operator-facing side), making it easier for a user to access and adjust the belt tension. Chassis  20  of belt tensioner  10  is received within track  9 , with the wings  64  of the lower carriage portion  60  able to slide along the track rails, thereby allowing idler pulley carriage  40  to displace axially along the track. 
     Lower wall  84  of retainer housing  82  includes a viewing window, in the form of two axially extending elongate slots  89  that allows a user to view the level of compression of the spring  83  by observing the position of plate  88 . As a general guide, slots  89  are disposed such that if plate  88  is visible then spring  83  is within a workable operating range, between a wholly uncompressed and a wholly compressed condition. 
     The ability to view the level of compression in the spring  83  assists a user when preloading the belt for a given door, or for readjusting the belt tension as part of a maintenance check. For example, the user may tension the tensioning device  10  to a prescribed preload in accordance with the size or type of door, by adjusting plate  88  to one of a number of positions along the length of slots  89 . For a heavier door, the spring  83  may need to be compressed until element  88  is positioned in the front part of the viewing window  89 , whilst for a lighter door the spring  83  may need to be compressed until the force receiving member  66  is positioned in a rear part of the viewing window  89 . Visual indicators, such as incremental markers, may be provided on retainer housing  82  (such as the single marking  92  shown in  FIGS. 2 to 4  between slots  89 ) to guide a user when setting or adjusting the tension. 
     Other suitable forms of visual indication of preload may be used. By way of example, retainer housing  82  may take the form of a cage (retaining spring  83  while allowing visual inspection of plate  88 ), or it may be wholly or partially transparent to allow visual observation. Alternatively, a pointer may protrude from retainer housing  82 , the pointer in movable association with the spring (e.g. attached to plate  88 ). Observation of a viewable part of the pointer against graduations on an external part of housing  82  provide an indication of the level of compression of the spring. Alternatively an electronic means such as a sensor or other position indicating encoder may be used, to provide a visual indication to a user of spring compression (e.g. via a light, display, etc.). 
     Track  9  is described and illustrated as a C-shaped track which encloses drive belt  8  and trolley  3 , however it will be understood that other forms of track may be used with the invention, such as an I-form rail, where trolley  3  is engaged around a part of the rail and the belt (or chain) runs alongside the rail. In such a version, idler pulley carriage  40  is arranged to displace along a front end portion of the I-form rail. 
     The chassis  20  and carriage  40  are formed of a material such as pressed steel. Pulley  70  is manufactured from a suitable engineering polymer, such as Dupont&#39;s Delrin®, an acetal homopolymer self-lubricating resin material, which is lightweight but durable, with suitable low wear and low friction properties, while the pulley axle shaft  56  is steel. Retainer housing  82  is made of a suitable lightweight polymer material such as Nylon. Spring  83  is fabricated from a tempered steel, although other suitable materials may be used. 
     It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.