Abstract:
A system is provided, in which the drive chain has features that permit control of the threshold driving force that will be reached before the chain&#39;s carrier rollers begin to rotate to permit accumulation or slip. The threshold driving force is controlled by friction members which are located between split portions of the carrier rollers and by the angle of the outer surface of the carrier rollers as well as by the amount of force provided by a biasing member. The threshold force depends upon the angle and the amount of biasing force.

Description:
This application is a continuation-in-part of U.S. application Ser. No. 08/878,810, now U.S. Pat. No. 5,960,938, filed Jun. 19, 1997 and is a continuation-in-part of U.S. application Ser. No. 09/014,870, now U.S. Pat. No. 6,062,378, filed Jan. 28, 1998, both of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to roller chains used for driving conveyors and other movable devices. Accumulating conveyor chains are known. These chains generally include a roller which carries a product, and, when the products begin to back up on the conveyor, the rollers begin to rotate, allowing the products to sit on top of the chain while the chain continues to run, without creating a large back line pressure on the products. A problem that can be encountered with such chains is that, if a substantial driving force is needed to move the products, the rollers may begin to rotate too soon, so that the products are not moved by the conveyor. Prior art accumulating conveyors generally do not allow control or adjustment of the threshold force at which the rollers begin to rotate. 
     SUMMARY OF THE INVENTION 
     The present invention provides a chain and drive design in which the threshold force at which the rollers begin to rotate is controlled. In the design of the present invention, the central carrier roller that carries the product or that drives the driven member is made in two pieces, and a friction member is mounted between the two roller pieces so as to restrict rotation of the roller pieces until a threshold force is reached. Also, in the preferred embodiment, the central carrier roller pieces may be tapered at various angles, in order to control the amount of friction force between the roller pieces and the friction member. 
     The design of the present chain may be used in any number of conveyor or drive systems where the accumulating concept is desirable. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view through a conveyor using a chain made in accordance with the present invention; 
     FIG. 2 is a top view of the chain of FIG. 1; 
     FIG. 3 is a side view of the chain of FIG. 1; 
     FIG. 4 is an exploded perspective view of a portion of the chain of FIG. 1; 
     FIG. 5 is an enlarged front sectional view of the chain of FIG. 1; 
     FIG. 6 is a side view of a chain similar to the chain of FIG. 1 but using an alternate embodiment of the friction member; 
     FIG. 6A is a side view of the friction member of FIG. 6; 
     FIG. 7 is a sectional view through an alternate conveyor using the chain of FIGS. 6 and 6A; 
     FIG. 8 is a sectional view through a second alternate conveyor using the chain of FIGS. 6 and 6A; 
     FIG. 8A is a sectional view through a third alternate conveyor using the chain of FIGS. 6 and 6A; 
     FIG. 9 is a sectional view through a fourth alternate conveyor made in accordance with the present invention, using the chain of FIGS. 6 and 6A; 
     FIG. 10 is a side view of the conveyor of FIG. 9; 
     FIG. 11 is a top view of an alternative adjustable friction chain; 
     FIG. 12 is a side view of the chain of FIG. 1 1 ; 
     FIG. 13 is a top view of a lift/turntable using the chain of FIG. 6; 
     FIG. 14 is a side sectional view of the lift/turntable of FIG. 13; 
     FIG. 15 is an enlarged view of the right side of FIG. 14; 
     FIG. 16 is a top view of a turntable being driven by the chain of FIGS. 11 and 12; and 
     FIG. 17 is a view along the section  17 — 17  of FIG.  16 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1-5 show an example of a conveyor and chain  10  made in accordance with the present invention. FIG. 1 shows the chain  10  mounted on an extruded support frame  12 , and driving a carriage  14 . So, in this case, the support frame  12  is stationary and the carriage  14  is the movable member driven by the chain. The weight of the carriage  14  is carried on the support frame  12  by rollers  13 , which roll along the support frame  12 . While the rollers are mounted on the carriage, they could, alternatively, be mounted on the frame. The carriage  14  includes a spring-biased drive member  16 , the bottom surface  18  of which has a V-shaped recess. The contour of the female V-shaped bottom surface  18  of the drive member  16  is the same as the contour  34  of the male V-shaped outer edge of the assembled carrier rollers  20  of the chain  10 . As will be explained later, the slope of the V-shaped contour affects the drive force with which the chain  10  drives products being carried on the chain, and different slopes can be used, as needed. The carrier roller  20  is made in two pieces  20   a,    20   b,  and a friction member  22  is mounted between and in friction contact with the pieces  20   a,    20   b.  The friction member  22  prevents the carrier roller  20  from rotating until some threshold force is reached. This means that, as the chain  10  is driven, it will drive the carriages  14  until the threshold force is reached. Once the threshold force is reached, the carrier rollers  20  will rotate so that the carriages  14  remain stationary as the chain  10  passes under the carriages  14 . 
     FIG. 1 also shows that, in addition to the carrier roller  20  and the friction member  22 , the chain  10  includes chain pins  24 , inner sidebars  26 , outer sidebars  28 , and outboard support rollers  30 . At intervals along the chain  10  are pairs of outer guiding sidebars  28   a,  which project downwardly to help guide the chain  10  between the rails  29  of the frame  12 . As shown in FIGS. 2 and 3, the carrier rollers  20  are mounted on every odd-numbered chain pin  24   a,  while the even-numbered chain pins  24   b  do not carry a carrier roller  20 . (The use of the terms even-numbered and odd-numbered is arbitrary. The odd-numbered pins  24   a  may also be referred to herein as forward pins, and the even-numbered pins  24   b  may be referred to as rear pins.) All the chain pins  24   a,    24   b  carry left and right support rollers  30 , which roll along the frame  12  as the chain  10  is driven. The mechanism for driving the chain  10  is not shown in these drawings but includes a drive sprocket, as is well known in the art. The friction members  22  are mounted on the odd-numbered chain pins  24   a  but also partially encircle the even-numbered chain pins  24   b,  which prevents the friction members  22  from rotating relative to the chain  10 . It would be possible to use other known methods to prevent the friction members  22  from rotating relative to the chain  10 , such as keying the friction members  22  to the pins  24  or to the bushings  42  or press fitting them onto the chain  10 , but this embodiment is preferred. Each of the friction members  22  includes horizontally-projecting wings  32 , which cover a space in the chain  10 , preventing dirt and debris from getting into the chain  10 . 
     FIG. 4 is an exploded perspective view of the chain  10 , showing the odd-numbered pins  24   a,  the even-numbered pins  24   b,  the friction members  22  with wings  32 , the carrier roller halves  20   a,    20   b,  each having a tapered outer edge surface, so that, when they are put together, they form a male V-shaped drive surface  34 , which contacts the complementary-shaped bottom surface  18  of the drive member  16 . FIG. 4 also shows the inner sidebars  26 , outer sidebars  28 , support rollers  30 , and snap-rings  36 , which fit into ring-shaped grooves  38  in the pins  24  (shown in FIG.  5 ). 
     FIG. 5 is the same sectional view of the chain  10  as shown in the top portion of FIG. 1, but it is enlarged to show more detail. It can be seen that there is a bushing  42 , pressed onto the odd-numbered pins  24   a,  on which the split carrier roller  20  is mounted. As shown in this view, there is an angle a between the drive surface  34  of the carrier roller portions  20   a,    20   b  and the horizontal (shown in phantom). The axis  40  of the pin  24  defines the horizontal direction. In this preferred embodiment, the angle a is 45°. The angle a may vary, depending upon the desired threshold friction force. The angle preferably is between 30° and 45°. The amount of horizontal force with which the carrier roller halves  20   a,    20   b  push against the friction member  22  depends upon the angle α and the amount of force exerted on the carrier roller halves  20   a,    20   b  by a pusher. The greater the horizontal force against the friction member  22 , the greater the friction force between the friction member  22  and the carrier roller halves  20   a,    20   b,  and the greater the threshold force required to cause rotation of the carrier rollers  20  relative to the chain  10 , meaning that the chain  10  will exert a greater drive force on the products being driven before the carrier rollers  20  begin to rotate relative to the chain  10 . 
     The threshold force of the chain may also be varied by varying the materials used to make the chain. The higher the coefficient of friction between the carrier roller portions  20   a,    20   b  and the friction member  22 , the greater the threshold force. 
     So, the present invention provides an arrangement whereby the threshold force of the chain may be controlled, to ensure that the products are driven up to the threshold force before the chain goes into an idling or accumulation mode, in which the carrier rollers rotate as the chain passes under the stationary products. 
     FIGS. 6 and 6A show a chain that is identical to the chain of FIGS. 1-5, except that it uses an alternative friction member  22 ′. This friction member  22 ′ can be snapped onto the chain and removed from the chain without having to disassemble the chain. This allows for ease of removal and replacement of the friction elements  22 ′ in case of excessive wear or when it is deemed desirable to replace the friction members  22 ′ with friction members  22 ′ made out of a different material with a different coefficient of friction. 
     FIG. 7 shows left and right loops of chain  710 , which are identical to the chain shown in FIGS. 6 and 6A, mounted on an alternate type of conveyor system. The chains  710  are mounted on left and right fixed support frames  712 , and drive a carriage  714 . The weight of the carriage  714  is carried on the support frames  712  by rollers  713 , which roll along the support frames  712 . The rollers  713  rotate about axes that are at an angle to each other of approximately 90°, each being approximately 45° from the horizontal, and the support surfaces on the support frame  712  are at the same angle to each other, which helps keep the carriage  714  running straight on the support frames  712 . The carriage  714  includes left and right spring-biased drive members  716 , each of which has a V-shaped recess in its bottom surface  718 . The contour of the V-shaped recess in the bottom surface  718  of the drive member  716  is the same as the contour  734  of the outer edge of the carrier rollers  720  of the chain  710 . 
     The conveyor frames  712  are held a fixed distance apart by means of brackets  750  bolted to the frames  712 . A horizontal beam  752  on the carriage  714  is used to support the product(s) being conveyed. 
     FIG. 8 shows a conveyor similar to the conveyor of FIG. 7, except that the angles of the wheels  813 ,  813 A,  813 B are different from the angles of the wheels in the embodiment of FIG.  7 . In this case, the support surfaces  815  are angled down from the horizontal at an angle of approximately 15°, and the wheels  813  rotate about axes that lie at the same angles, so that the carriage  814  tracks correctly on the conveyor. There are also left and right guide wheels  813 A,  813 B, on the carriage  814 , which rotate about vertical axes along vertical guide surfaces  815 A,  815 B, respectively. The weight of the carriage  814  is carried on the support frame  812  by the rollers  813 . The two loops of chain  810  are the same as in the previous embodiment. The frame members  812  provide angled support surfaces  815 , to support the wheels  813  of the carriage  814 . The carriage  814  includes left and right spring-biased drive members  816 , the bottom surface  818  of each of the spring-biased drive members having a V-shaped recess. The contour of the female V-shaped bottom surface  818  of the drive member  816  is the same as the contour  834  of the male V-shaped outer edge surface of the assembled carrier rollers  820  of the chain  810 . Brackets  850  are bolted to the frame members  812  to hold them a fixed distance apart. Each carriage  814  includes at least one cross-member  852 , which supports the products on the carriage  814 . 
     FIG. 8A shows an embodiment that is identical to the embodiment of FIG. 8, except that the angled support wheels  613  and their respective support surfaces  615  are on the outside, and the vertical-axis guide wheels  613 A and  613 B and their respective guide surfaces  615 A and  615 B are on the inside. 
     FIGS. 9 and 10 show another alternative embodiment of a conveyor made in accordance with the present invention. In this case, instead of the chain being mounted on the conveyor frame, the chain  910  is mounted on the carriage  914 . The chain  910  is identical to the chain shown in FIGS. 6 and 6A. There are two loops of the chain  910  on the carriage  914 , and they are driven by a drive motor  936 , which drives sprockets  938 , which drive the chains  910 . So, in this case, the movable member, which is the pallet, is motorized and drives itself along the left and right conveyor frame members  912 . The motor  936  preferably is an electric motor. The weight of the carriage  914  is carried on the support frame  912  by horizontal-axis rollers  913 , which roll along horizontal support surfaces  915  on the frame members  912 . The carriage  914  includes biased drive members  916 , which push down on the outer rollers  930  of the chains  910 , so as to push the respective chains  910  downwardly, against female V-shaped carry-ways  935  on the frame members  912 . The female V-shape of the carry-ways  935  has the same contour as the male V-shape of the carrier rollers  920 . The pusher  918 , which pushes down on each drive member  916 , may be a simple spring, or it may be a solenoid, which would enable it to adjust the amount of force applied to the drive member  916 . 
     FIGS. 11 and 12 show an adjustable friction chain  510 , which is identical to the chain of FIG. 6, except that it does not have the outer rollers  30 , and the split carrier roller halves  20   a,    20   b  are mounted on every pin rather than every other pin. This chain includes left and right carrier roller halves  20   a,    20   b,  chain pins  24   a,    24   b,  inner sidebars  26 , outer sidebars  28 , and friction pads  22 ′. The friction pads  22 ′ lie between the roller halves  20   a,    20   b  and are mounted on the forward pins  24   a  and the rear pins  24   b  to prevent them from rotating. The left and right roller halves  20   a,    20   b  have tapered outer edges, which, when assembled together, form a V-shaped projection. 
     FIGS. 13-15 show a turntable for a conveyor system, which is driven by the chain of FIG.  6 . The chain is driven by a motor  600  and a double sprocket  610  and is wrapped around a circular V-shaped track  612 , which is fastened to the table  614  by pins  616 , so that the track  612  rotates with the table  614  (See FIG.  15 .). The sprocket  610  is a double sprocket, which drives on the outboard rollers  30  of the chain. The motor  600  is mounted on a fixed frame  617 , and the table  614  is supported on the frame  617  by ball bearing rollers  619 . The stationary support  617  for the table  614  includes stationary shock-absorbing stop blocks  618 ,  620 , and the table  614  carries a stop block  622 , so that, when the table  614  is rotated in a clockwise direction, it will be stopped when the stop block  622  hits the shock-absorbing stop block  620 , and, when it is rotated in a counterclockwise direction, it will be stopped when the stop block  622  hits the shock-absorbing stop block  618 . While the shock-absorbing stop blocks  618 ,  620  are fixed on the stationary support  617  in this embodiment, it would be possible to mount them on solenoids so they can move into and out of position and to provide several of them, so as to provide any number of possible stop positions. 
     A chain tension adjuster  630  applies the desired amount of force to tension the chain, and this controls the amount of force with which the split roller halves  20   a,    20   b  are pressed against the V-track  612 , and the amount of friction between the friction members  22 ′ and their respective roller halves  20   a,    20   b,  thereby controlling the amount of force with which the chain will drive before the roller halves  20   a,    20   b  begin to rotate. When the table  614  is stopped, because the stop block  622  has run up against one of the shock-absorbing stop blocks  618 ,  620 , the chain will simply run relative to the stopped table  614 , with the roller halves  20   a,    20   b  rotating relative to the track  612  and relative to the friction pads  22 ′. When there is no stop block interfering with the travel of the table  614 , the friction between the split rollers  20   a,    20   b  and the friction pads  22 ′ is sufficient to prevent the rollers  20   a,    20   b  from rotating, so their contact with the V-track  612  will cause the table to be driven. The drive gearmotor  600  can change direction, so that the table is rotated from one stop position to the other and then back again. 
     FIGS. 16 and 17 show a drive arrangement similar to the arrangement of FIGS. 13-15, except that the chain  510  of FIGS. 11 and 12 is used, and the chain is driven by a V-shaped pulley  512  rather than by a sprocket. The pulley  512  is driven by a gear motor  600 , and the chain  510  wraps around the pulley  512  and around the V-track in the turntable  614 . 
     It will be obvious to those skilled in the art that modifications may be made to the embodiments described above without departing from the scope of the present invention.