Abstract:
A conveyor construction includes a frame having a pair of side members, a belt and a tensioning section mounted for longitudinal extendable and retractable movement relative to the frame for establishing a desired tension on the belt. The tensioning section includes a spindle engaged with the belt and a pair of side plate structures connected to the spindle and located one adjacent each frame side member. A drive member is rotatably mounted relative to the frame and is drivingly engaged with the tensioning section for imparting longitudinal extendable and retractable movement relative to the frame upon rotation of the drive member. A locking device inserts a frictional locking force on the side plate structures relative to the frame side members for selectively fixing the position of the tensioning section relative to the frame. A restraining arrangement is incorporated in the side plate structures for limiting the retractable movement of the tensioning section upon the imposition of a random force applied to the spindle and overcoming the frictional locking force of the locking device so as to substantially retain the desired tension on the belt and preserve operability of the drive member.

Description:
FIELD OF THE INVENTION 
     This invention relates broadly to conveyor construction and, more particularly, pertains to developments in the mechanism for tensioning the continuous belt of the conveyor. 
     BACKGROUND OF THE INVENTION 
     The present invention contemplates improvements to a known conveyor construction such as generally disclosed in Hosch et al. U.S. Pat. No. 6,298,981, the disclosure which is hereby incorporated by reference. The &#39;981 patent discloses a conveyor construction including a frame and a tensioning section including spaced side members mounted for longitudinal movement relative to the frame. The tensioning section includes a spindle about which a conveyor belt is trained, and movement of the tensioning section functions to control the tension of the belt. A drive and locking arrangement for imparting movement to the tensioning section and for selectively locking the tensioning section in position includes a pair of pinion carriers or retainer blocks mounted one to each side of the frame, with a drive pinion being rotatably supported by the retainer blocks. Each side member includes integrally formed gear teeth engageable with opposite ends of the drive pinion, and a drive pinion actuator is engaged with one side of the frame for imparting rotation to the drive pinion to extend and retract the tensioning section. A locking arrangement is interconnected with the opposite end of the drive pinion, and functions to selectively frictionally engage the drive pinion with one of the retainer blocks to prevent rotation of the drive pinion and to thereby maintain the tensioning section in a desired position relative to the frame. 
     This construction is generally satisfactory, but can present problems upon the imposition of a sudden or random force applied to the spindle once the tensioning section has been locked into a particular position so as to set a desired tension for the moving belt. Such a force may be caused by a collision or impact of the spindle with another piece of equipment or with a structural member, such as a wall. If this impact force has enough intensity, it can overcome the frictional locking force of the locking arrangement, such as by shearing or stripping the locking components, resulting in undesirable, retractable movement of the tensioning section which will alter the belt tension and negatively affect the performance of the conveyor. In some designs, the impact force may act to drive the gear teeth on the moving side members against the drive pinion as its locked position is overcome causing damage or destruction to the gear teeth on the drive pinion. 
     It is desirable to provide a conveyor construction which rectifies the problems described above, and offers enhancements in the components, assembly, operation and maintenance of the tensioning section of the conveyor. 
     SUMMARY OF THE INVENTION 
     It is one object of the present invention to provide a conveyor construction in which involuntary, retractable movement of the tensioning section is limited so as to maintain a desired tension on the conveyor belt and preserve the integrity of the drive pinion structure. 
     It is also an object of the present invention to provide a conveyor construction which relies upon wedging action between the components of the tensioning unit to prevent damage to the drive pinion structure when an undesirable force is inflicted upon the spindle. 
     It is a further object of the present invention to provide a conveyor construction having an improved structure for engaging the drive pinion structure with the tensioning section. 
     In accordance with one aspect of the invention, a conveyor construction includes a frame having a pair of side members, a belt and a tensioning section mounted for longitudinal extendable and retractable movement relative to the frame for establishing a desired tension on the belt. The tensioning section includes a spindle engaged with the belt and a pair of side plate structures connected to the spindle and located one adjacent each frame side member. A drive member is rotatably mounted relative to the frame and is drivingly engaged with the tensioning section for imparting longitudinal extendable and retractable movement relative to the frame upon rotation of the drive member. A locking device exerts a frictional locking force on the side plate structures relative to the frame side members for selectively fixing the position of the tensioning section relative to the frame. This aspect of the invention contemplates an improvement in the form of a restraining arrangement incorporated in the side plate structures for limiting the retractable movement of the tensioning section upon the imposition of a random force applied to the spindle and overcoming the frictional locking force of the locking device so as to substantially retain the desired tension on the belt and preserve operability of the drive member. 
     Each of the side plate structures includes a first member which is selectively moveable or lockable relative to a fixed second member. The first member preferably includes a head plate extending longitudinally along an inside surface of one of the frame side members. The second member preferably includes a clamp plate extending longitudinally along an inside surface of the head plate. The head plate is integrally constructed of a forward portion, a mid portion and a rear portion. The spindle has opposed ends, each end being rotatably mounted to the head plate. The forward portion of the head plate includes a circular socket member connected to the mid portion by an angularly and inwardly offset segment. The socket member receives a spherical ball bearing assembly for enabling rotation of the spindle. The mid portion is formed with a first throughslot and includes a first pair of upper and lower angled surfaces. The rear portion is formed with a second throughslot and includes a set of teeth extending axially along a wall forming the second throughslot. The drive member has opposed ends provided with drive pinion ends rotatably mounted to the frame members. Each drive pinion end extends into the second throughslot for engagement with axially extending teeth on the rear portion of the head plate. The clamp plate includes a restraining block integrally connected to an extension portion which rotatably receives an adapter connected to each drive pinion end. The restraining block is inserted into the first throughslot formed in the mid portion of the head plate and locked to one of the frame side members. The restraining block includes a second pair of upper and lower angled surfaces which are selectively slidably and lockingly engageable with the first pair of upper and lower angled surfaces on the mid portion of the head plate. The first and second pairs of angled surfaces are constructed and arranged to move into a wedging relationship with one another upon imposition of the random force applied to the spindle. 
     In accordance with another aspect of the invention, a conveyor construction includes a frame having a pair of side members, a belt and a tensioning section mounted for longitudinal extendable and retractable movement relative to the frame for establishing a desired tension on the belt. The tensioning section includes a spindle engaged with the belt and a pair of side plate structures connected to the spindle and located one adjacent each frame side member. A drive member is rotatably mounted relative to the frame and is drivingly engaged with the tensioning section for imparting longitudinal extendable and retractable movement relative to the frame upon rotation of the drive member. A locking device exerts a frictional locking force on the side plate structures relative to the frame side members for selectively fixing the position of the tensioning section relative to the frame. The conveyor construction is improved wherein each of the side plate structures includes a first member selectively movable and lockable with respect to a second member. The first member is freely slidable upon the second member when the tensioning section is extended, and the first member is slidable into a wedging relationship with the second member when the tensioning section is retracted. 
     The first member is preferably a head plate formed with a top wall, a bottom wall and a first throughslot. The head plate includes upper and lower inner edges having planar surfaces which angle slightly outwardly towards a respective one of the frame side members as the head plate extends from front to rear. The second member is preferably a clamp plate including a restraining block having an outer section received in the first throughslot, and an inner section which is coplanar with an extension portion. The outer section of the restraining block includes an upper horizontal surface engageable with an outer, bottom portion of the head plate top wall, and a lower horizontal surface engageable with an outer, top portion of the head plate bottom wall. The inner section of the restraining block includes an upper vertical face engageable with the upper inner edge of the head plate, and a lower vertical face engageable with the lower, inner edge of the head plate. The upper and lower vertical faces have planar surfaces which extend at an angle from front to rear similar to the angle formed on the upper and lower inner edges on the head plate. The locking device includes a pair of fasteners passing through respective holes formed in a respective frame side member and the first throughslot for threaded engagement with the restraining block whereby tightening of the fasteners will lock the head plate and clamp plate together relative to the respective frame side member. 
    
    
     Various other objects, features and advantages of the invention will be made apparent from the following description taken together with the drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawings illustrate the best mode presently contemplated of carrying out the invention. 
     In the drawings: 
     FIG. 1 is a perspective view of the conveyor assembly according to the present invention; 
     FIG. 2 is another perspective view of the conveyor assembly of FIG. 1 shown turned over with the conveyor belt removed; 
     FIG. 3 is an enlarged, detail or bottom perspective view of the movable tension section of the conveyor assembly taken on line  3 — 3  of FIG. 2; 
     FIG. 4 is a reverse, exploded view of the movable tensioning section; 
     FIG. 5 is a plan view of the movable tensioning section shown in FIG. 3; 
     FIG. 5A is an enlarged, fragmentary sectional view taken on line  5 A— 5 A of FIG. 5; 
     FIG. 6 is a view like FIG. 5 showing the tensioning section moved relative to the conveyor frame in the direction of the arrows; 
     FIG. 7 is an enlarged, fragmentary sectional view taken on line  7 — 7  of FIG. 5; 
     FIG. 8 is a sectional view of the movable tensioning section shown in FIG. 5; 
     FIG. 9 is an enlarged, detailed view in partial cross section taken on line  9 — 9  of FIG. 5; and 
     FIG. 10 is an enlarged sectional view taken on line  10 — 10  of FIG.  7 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1 and 2, a conveyor assembly  10  generally includes a frame  12 , a stationary drive section  14  interconnected with a motor  16 , a movable tensioning section  18 , and a belt  20 . 
     Frame  12  extends between a first end  22  located adjacent drive section  14  and a second end  24  located adjacent tensioning section  18 . Referring to FIGS. 3 and 4, frame  12  includes an upper wall or support surface  26  and a pair of depending side flanges or walls  28 ,  30  extending downwardly from the sides of upper wall  26 . Side wall  28  includes an outwardly offset lower end portion  32  and side wall  30  includes an outwardly offset lower end portion  34 . An angled connector section  36  extends between side wall  28  and lower end portion  32 , and likewise an angled connector section  38  extends between side wall  30  and lower end portion  34 . Side wall  28  and lower end portion  32  lie in parallel planes, as do side wall  30  and its associated lower end portion  34 . 
     Frame upper wall  26  defines a central groove  40  which extends to full length of frame  12  between first end  22  and second end  24 . Groove  40  is defined by a downwardly deformed central section of upper wall  26  having an upper surface which is recessed relative to the upper surface of upper wall  26  on either side of groove  40 . Belt  20  includes a dependent rib  42  (FIG. 5) which is received within groove  40 . 
     Referring now to FIGS. 3,  4 , and  5 , tensioning section  18  is movably mounted to frame  12  at its first end  24  for selectively tensioning a belt  20  in a manner to be explained. Tensioning section  18  includes a pair of identical, spaced apart side plate structures  44 , each of which is positioned inwardly adjacent one of the frame side walls  28 ,  30 . Each identical side plate structure  44  includes a first member or head plate  46  which is selectively movable or locked relative to a second member or clamp plate  48 . 
     Each head plate  46  extends longitudinally along an inner surface of a respective frame side wall  28 ,  30  and is integrally constructed of a forward or spindle mounting portion  50 , a mid portion  52  and a rear portion  54  having an end wall  56 . A vertical dividing wall  58  separates each mid portion  52  from its rear portion  54 . Each head plate  46  has a planar top wall  60  and a planar bottom wall  62  which lie generally parallel to each other. Each forward or spindle mounting portion  50  is defined by a circular socket member  64  which is joined to its mid portion  52  by an angularly and inwardly offset segment  66 . 
     An idler spindle  68  extends between and is rotatably mounted to and between the circular socket members  64 . Idler spindle  68  includes belt engaging sections  70  with a groove  72  therebetween for receiving belt rib  42 . The belt engaging sections  70  have a link for supporting substantially the entire width of the belt  20 . 
     As seen best in FIGS. 4 and 8, each circular socket member  64  forms a cavity  74  having circular outer walls  76  defining an outer opening, and circular inner walls  78  defining an inner opening. Each outer opening is closed by an end cap  80  having an inwardly extending ring  82  which is press fit against the outer walls  76 . Each inner opening is shaped to receive and retain a spherical ball bearing assembly  84  having an inner race  86  and an outer race  88 . The inner races  86  are slipped over short cylindrical heads  90  projecting from the end walls  92  of the spindle belt engaging sections  70  and lie against circular necks  94  surrounding the heads  90 . Torque screws  96  are inserted through the inner races  86  and the heads  90  so that a tool may be introduced into passages (one being shown at  98 ) formed transversely in the spindle end portions for swaging the torque screws  96  outwardly into frictional contact with the heads  90  and the inner races  86 . Because of the end caps  80  and the engagement of the inner races  86  with the radially extending necks  94  and the axially extending heads  90 , this construction provides an effective arrangement for enclosing bearing assemblies  84  to ensure that water or other liquid cannot easily reach the interior of the bearing assemblies  84 . 
     The mid portion  52  of each head plate  46  has respective outer and inner walls  100 ,  102  formed with a horizontal throughslot  104  which is alignable with a pair of openings  106  and frame side walls  28 ,  30 . Each mid portion  52  provides an upper, outer edge  108  and a lower, outer edge  110  which are coplanar with the straight inner surface of a respective frame side wall  28 ,  30 . Each mid portion  52  further provides an upper, inner edge  112  and a lower, inner edge  114  which are coplanar and integrally define a first pair of engagement surfaces constructed in accordance with the present invention. Referring to FIGS. 3,  4 ,  5  and  8 , the upper and lower, inner edges  112 ,  114  have planar surfaces which angle slightly inwardly or taper toward their respective side walls  28 ,  30  as each mid portion  52  progresses longitudinally from front to rear. 
     The rear portion  54  of each head plate  46  has upper and lower, outer edges  116 ,  118  which are respectively aligned longitudinally with the upper and lower, outer edges  108 ,  110  of each mid portion  52 . Each rear portion  54  also has upper and lower, inner edges  120 ,  122  which are outwardly recessed relative to the upper and lower, inner edges  112 ,  114  of each mid portion  52 . In contrast with the outer and inner edges  108 ,  110 ,  112 ,  114  of each mid portion  52 , the outer and inner edges  116 ,  118 ,  120 ,  122  of each rear portion  54  are generally parallel to each other. A horizontal throughslot  124  is provided in each rear portion  54  and lies in alignment with a single hole  126  in a respective frame side wall  28 ,  30 . Each rear portion  54  carries a series of gear teeth  128  forming an axially extending gear rack located vertically above and inwardly of throughslot  124 . 
     Each clamp plate  48  is positioned inwardly of each head plate  46  and includes a restraining block  130  integrally connected to an extension portion  132 . As seen in FIG. 10, each restraining block  130  is generally T-shaped in cross section and has an elongated outer section  134  and an inner section  136  which are provided with a pair of spaced apart, threaded apertures  138 . Each outer section  134  is received within one of the throughslots  104  in a mid portion  52  and includes respective upper and lower, horizontal surfaces  140 ,  142  which respectively engage the outer, bottom portion of the mid portion top wall  60  and a outer, top portion of the mid portion bottom wall  62 . Each inner section  136  has respective upper and lower, vertical faces  144 ,  146  which engage the upper and lower, inner edges  112 ,  114  of each mid portion  52  and define a second pair of engagement surfaces. Each pair of faces  144 ,  146  has planar surfaces which angle slightly outwardly or diverge complimentary to the upper and lower edges  112 ,  114  of each mid portion  52  as illustrated in FIGS. 3,  4 ,  5  and  8 . Bolts  148  extend through aligned openings  106  and throughslots  104  and are threaded into apertures  138  to securely mount restraining blocks  130  to frame side walls  28 ,  30  when the tensioning section  18  is used to set a desired tension on the belt  20  as will be appreciated hereafter. 
     Referring to FIGS. 4,  5 A,  7  and  9 , the extension portion  132  of each clamp plate  48  terminates in a circular recess  150  which surrounds and rotatably receives a round adapter  152  that carries a rotatable drive pinion end  154  having a through hole  153 . Each adapter  152  has a hexagonally shaped interior recess  155 , the walls of which are press fit over mating hexagonally shaped outer walls  156  on each end of a rotatable hex rod or drive member  158 . Each drive pinion end  154  extends into a respective throughslot  124  in each head plate rear portion  54 , and has a series of radial teeth  160  which engage the axially extending teeth  128  of each rack depending from the underside of the top wall  60  forming the throughslot  124 . The opposed ends of the drive member  158  are provided with threaded holes  162  which are in registration with the holes  126  formed in the frame side walls  28 ,  30 . Sleeves  164  are inserted into the side wall holes  126 , and inner ends  166  of bolts  168  extend through the sleeves  164  and the recesses  155  for threaded engagement in the holes  162  in drive member  158 . It will be appreciated that rotation of a bolt  166  and drive pinion ends  154  and engagement of the rack teeth  128  will enable the head plates  46  and connected idler spindle  68  to extend and retract longitudinally relative to frame  12  so as to adjust tension on belt  20 . It should be further understood that with the restraining blocks  130  inserted in throughslots  104  in the extension portions  132  engaged around the adapters  152  on the ends of drive member  158 , the clamp plates  48  are always held fixed relative to the head plates  46 . 
     In operation, tensioning section  18  is selectively moved relative to frame  12  and selectively locked into position as follows. Once belt  20  is initially installed such that rib  42  is received within frame groove  40  and in initial engagement with spindle groove  72 , bolts  148  are loosened in the restraining blocks  130  to permit the head plates  46  and idler spindle  68  joined thereto to slide relative to the frame side walls  28 ,  30  and the clamp plates  48 . One of the bolts  166  is then rotated to turn drive pinion ends  154  causing the racks formed by teeth  128  to move outwardly in unison and correspondingly move the head plates  46  and joined idler spindle  68  outwardly until the desired belt tension is achieved. During this outward or extendable movement, the engagement surfaces  112 ,  114  on each head plate mid portion  52  slide freely relative to engagement surfaces  144 ,  146  of clamp plate restraining blocks  130 . Once the belt tension is set, the bolts  148  are tightened to lock head plates  46  and clamp plates  48  tightly together and at the same time, lock the idler spindle  68  in the desired position relative to the belt  20  as depicted in FIG.  5 . Normally, the setting of the desired belt tension is maintained by the tightening of the bolts  148  in the restraining blocks  130  which place the engagement surfaces  112 ,  114  of the head plates  46  in a secured, flush relationship with engagement surfaces  144 ,  146  of the clamp plates  48 . 
     It sometimes happens that an unexpected, involuntary force is applied to the idler spindle  68  by impact or collision with another static or moving component. In such cases, the intensity of the impact can overcome the force exerted by the applicable locking device. This causes the idler spindle  68  to be forcefully retracted in a manner which can decrease the belt tension and negatively effect the conveyor operation. In some situations, this undesirable, forceful retraction can also damage or destroy the teeth on the drive pinion. Such problems are minimized by the action of the cooperating engagement surfaces  112 ,  114 ,  144 ,  146  of the present invention. 
     FIG. 6 depicts such a situation wherein a random blow is inflicted upon the idler spindle  68  in the direction of arrow A. Such blow can overcome the locking force provided by the tightened bolts  148  and begins to retract the idler spindle  68  as the head plates  46  are forced rearwardly in the direction of the arrows B. However, the head plates  46  are only permitted to move from the phantom line position to the full line position a very small distance, typically a fraction of an inch, relative to the frame side members  28 ,  30  because the angled or tapered surfaces  112 ,  114  quickly slide into a wedging, restraining relationship with the corresponding fixed, clamp plate angled or diverging surfaces  144 ,  146 . The wedging, progressively increasing frictional interaction between the angled, engagement surfaces  112 ,  114  and the angled, engagement surfaces  144 ,  146  tends to absorb the impact force on the idler spindle  68  so that the moving teeth  128  of the gear rack on the rear portions  54  will cause the drive pinion ends  154  to harmlessly rotate with respect thereto preserving the integrity of the drive pinion ends  154 . Following this reaction, maintenance is undertaken to inspect the components of the tensioning section  18 . 
     The present invention thus provides a restraining arrangement for limiting the retractable movement of and substantially maintaining the tension section  18  in a desired position even in the event of a random impact on the idler spindle  68 . The engagement of drive pinion ends  154  with the rack teeth  128  on head plates  46  ensures that the head plates  46  are simultaneously and synchronously moved relative to frame  12 . If belt  20  exhibits any skewing tendency, engagement of belt rib  42  with spindle groove  72  prevents skewing along with the action of the spherical ball bearing assemblies  84  on the ends of the idler spindle  68 . 
     While the invention has been described with reference to a preferred embodiment, those skilled in the art will appreciate that certain substitutions, alterations and omissions may be made without departing from the spirit thereof. Accordingly, the foregoing description is meant to be exemplary only, and should not be deemed limitative on the scope of the invention set forth with the following claims.