BACKGROUND OF THE INVENTION

This invention pertains to chains, and, in particular, to a side-flexing chain with wheels for supporting the weight of the chain and for guiding the chain.

Many types of chains are known in the art. Some chains have support wheels to carry the weight of the chain and guide wheels to guide the chain as it travels along a track. However, there are several problems with these chains. The chains of this type which existed prior to the present invention cou^d only be driven by a sprocket lying below the chain, meaning that less than half of the chain could be functioning to carry products at any given time, and the rest of the chain would be passing over the sprocket or on a return run. The cost of the extra chain and the cost of continually moving the extra chain are substantial and are essentially wasted expenses.

If the conveyors using these chains get to be too long, the chain has to be broken into pieces, each having a separate drive. The cost of the drive and its related controls is usually about one-third of the cost of the conveyor, so breaking the conveyor into parts with separate drives is very expensive.

The known chains of this type can only be pulled — they can" ; be pushed. If they were pushed, they would buckle and wee against their guide tracks.

The known chains of this type can only be driven by a sprocket, which must be at the head end of the conveyor. This is often an inconvenient location for the drive, as the ends of the conveyor are often crowded with other devices. It would be very desirable to move the drive to another part of the conveyor, but, prior to the present invention, that has not been possible.

The known chains of this type all require a catenary or some other arrangement to keep the chain tight and to compensate for any stretching of the chain during operation.

The known chains of this type generally do not provide good bearing surfaces for the joints of the chain which flex, which causes the chains to tend to wear at those joints.

The known chains generally require wheel turns to carry the chain around sharp turns, which is a substantial additional expense.

SUMMARY OF THE INVENTION

The present invention overcomes many of the disadvantages of prior art chains.

The present invention provides a chain which has wheels for support and for guiding, as with some known chains, but it has several advantages over the known chains. An important advantage is that it can be driven by at least three different means. It can be driven by a sprocket lying below the chain, as in the prior art, or by a sprocket on the side of the chain (which provides the advantage that the entire top surface of the chain can be used for conveying products at any given time), or by a screw beneath the chain, which permits the entire top surface of the chain to be used for conveying and permits drives to be used at any convenient place or places along the chain, without having to break the chain into pieces when the conveyor becomes long.

The present invention permits two or more drives to be used on the same section of chain. This allows the conveyor to be as long as required for the job, and the drives can be added at spaced intervals along the chain as required in order not to exceed chain pull limits.

Unlike some prior art chains, the present invention requires only a single type of link to make the entire chain. In the prior art, it was often necessary to use two different types of chain links to form the chain — one link to carry

the guide wheels and one link to carry the support wheels, for example.

In the present invention, both the guide and support wheels are located on each individual link, and the axes of the guide wheels and of a pair of pivoting support wheels on one link intersect at the same point. This permits the chain to be pushed without jamming into the guide track, which cannot be done with any of the known side-flexing chains. It is this ability to be pushed as well as pulled which permits the chain to be driven at intermediate locations along the conveyor by means such as a screw.

In addition to the benefit of being able to locate several drives along a single length of chain, a screw drive also eliminates the jerky motion of the chain caused by cordal action as the chain passes over the sprockets.

The present invention also provides an improved bearing surface for the flexible joint, which reduces wear.

The present invention also provides a means for the chain itself to compensate for stretching during use, so that no catenary take-up is required.

The present invention can operate around tight turns without requiring the use of wheel turns on the conveyor, because it has its own low friction roller guiding arrangement, and because its design permits the chain itself to make a tight turn.

The present invention also provides an improved means for retaining the chain pin on the link.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an exploded perspective view of a chain link made in accordance with the present invention;

Figure 2 is a side view thereof, showing the support track in phantom;

Figure 3 is a bottom view thereof, with a portion of an identical adjacent link shown in phantom;

Figure 4 is a front view of the link of Figure 1 with an attachment added to the top surface and showing a broken-away view partially in section of the screw drive with the support and guide track shown in section; Figure 5 is a side sectional view of the link of Figure 1 with an attachment added to the top surface;

Figure 6 is a front view of the link of Figure 1 with a different type of guide track shown in section;

Figure 7 is a top view of a conveyor system in which the chain is made up of the links of Figure 1, and the chain is driven by a screw drive;

Figure 8 shows a broken-away side view partially in section of the system of Figure 7;

Figure 9 is a top view of a conveyor system including a chain made up of the links of Figure 1 being driven by a sprocket rotating about a vertical axis;

Figure 10 is a side view partially broken away of a conveyor system including a chain made up of the links of Figure 1 being driven by a pair of sprockets rotating about a horizontal axis;

Figure 11 is a top view of a second embodiment of the invention, in which the screw drive is skewed at an angle to the direction of travel of the chain, and the guide track has been removed for clarity; and Figure 12 is a view along the section 12-12 of Figure 11.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The chain link 10 shown in Figures 1-5 is made up of a body 16 which has a rear portion 12 and a forward projection 14. It also has an article-carrying, flat, top surface 18. The link defines three vertical holes 17, which can be drilled out through the top surface 18 to permit other types of top surfaces to be added to it. As shown in Figures 4 and 5, the vertical holes 17 have been drilled through the top surface 18, and another top surface 18A has been mounted on the link by means of self-tapping screws 19. Many different

configurations of top surfaces are known in the art, and it is contemplated that they could be added to this link or to a similar base link which is made without the top surface 18 by means of screws or other attachment means or by being formed integral with the link body 16.

A pair of support wheels 20, 22 and a pair of guide wheels 24, 26 are shown mounted on the link 10. As is shown in Figure 3, each link 10 actually has two pairs of support wheels 20, 22 mounted on it. A forward pair of support wheels 20, 22 is shared with the identical link ahead of the link 10 and pivots relative to the link 10, and a rear pair of support wheels 20, 22 is shared with the identical link behind the link 10 and does not pivot relative to the link 10. A very useful feature of this link 10 is that its forward (pivoting) pair of support wheels 20, 22 and its guide wheels 24, 26 have axes which intersect at a single point. This permits a chain made up of these links 10 to be pulled or pushed without the links 10 becoming jammed in their tracks.

The rear portion 12 of the link 10 includes firs- and second opposed arms, 28, 30, respectively. The first and second opposed arms 28, 30 are spaced apart and lie parallel to each other. Each of the arms 28, 30 defines a horizontal hole 32 which is elongated from front to back, and the horizontal holes 32 of each pair of arms 28, 30 are aligned so that a chain pin can extend through the pair of holes 32. The fact that these horizontal holes 32 are elongated in the front-to-back direction means that the chain made up of the links 10 can compensate for stretching of the links 10 during operation at t ^~ discharge side of a drive unit. The front rojection 14 has a vertical cylindrical bore 34 and a horizontal bore 36 which is elongated from fror^-to- back to permit pivoting of the links 10 about a vertical .ixis relative to each other (side-flexing). The vertical bore 34 and the horizontal bore 36 intersect. The axes of those bores 34, 36 intersect at a point which lies along an imaginary plane that bisects the link 10 from front to back.

The body portion 16 of the link 10 also includes a pair of scrapers 38, which project downward from the bottom surface of the link. These scrapers 38 lie at an acute angle of about 30 degrees to the direction of travel of the link so that they will push debris toward the center of the link, where it will fall out of the track when the link is driven forward. This feature is particularly important when the chain 40 made up of these links is used in an assembly operation, where loose pieces such as screws and bits of dirt tend to fall onto the track on which the chain runs. Many other chains tend to jam and fail when these loose pieces get wedged into the chain or between the chain and the track. These scrapers 38 help solve that problem by pushing the debris off of the track.

In order to assemble the links 10 into a chain 40, two types of pins are used. A vertical pin 42, having a head 44 at its lower end, is extended through the vertical bore 34 of the front projection 14 of each link and through the central cylindrical bores 46 in the guide wheels 24, 26. The vertical pin 42 has a transverse cylindrical bore 48, the axis of which is perpendicular to the axis of the pin 42.

Each link also has a chain pin 50, which extends through the central cylindrical bore 52 of one support wheel 20, through one of the spaced-apart arms 28, through the horizontal bore 36 in the forward projection 14 of the adjacent identical link and through the transverse bore 48 in the vertical pin 42 of that adjacent link, and through the horizontal hole 32 in the other arm 30 and through the central bore 52 of the other support wheel 22. The ends of the chain pin 50 define annular grooves 54, which receive 0-rings 56, preferably made of Teflon or some other low-friction material, to retain the chain pin 50 on the chain. The annular grooves 54 are radiused to fit the O-rings.

When the links 10 are being assembled to make a chain 40 for a conveyor system, the chain 40 is made to a length which fits tightly into the conveyor frame. When the chain 40 is stretched tight, the chain pins 50 will be bearing against the

rear semi-cylindrical surface 58 of the horizontal holes 32 in the arms 28, 30 of each link 10. As the chain links 10 stretch slightly during operation of the conveyor, the chain pins 50 can move forward in the holes 32 until they abut the forward semi-cylindrical surface 60 of the horizontal holes 32, so the length of the chain remains constant, even when the links stretch. This ability of the chain to automatically adjust its length to compensate for stretching eliminates the need for a catenary or other type of take-up arrangement at the discharge side of the drives.

. Figures 7-10 show three different conveyor systems using the chain 40. All of the conveyor frames in those systems include a pair of support rails 62 or 62A and a pair of guide rails 64, with the support surface of the support rails 62 or 62A lying perpendicular to the guide rails 64. Two types of support rails 62, 62A are shown in the drawings. As shown in Figure 4, the support rails 62A wrap around the support wheels 20, 22, to keep the support wheels from lifting up out of the track. This is needed in horizontal and vertical turns and through the screw drive. A simpler type of support rail 62, shown in Figure 6, can be used for straight runs. The support rail 62 or 62A and guide rail 64 are preferably made of a single beam 66 or 66A, as shown in Figures 4 and 6. The guide rails 64 are spaced apart a distance which is slightly larger than the diameter of the guide wheels 24, 26. If the chain 40 is to be driven by a screw 68, as shown in Figures 4 and 8, the guide rails 64 have a height which is approximately equal to the height of one of the guide wheels 24, and the upper guide wheels 24 ride between the guide rails 64 along the conveyor path. The lower guide wheels 26 extend below the guide rails 64 in order to contact the drive screw 68.

The support rails 62, 62A are wide enough to receive the support wheels 20, 22. The scrapers 38 project downward from the chain slightly less than do the support wheels 20, 22, so they travel just above the support surface of the support rails 62, as shown in Figure 2. The beams 66, or 66A, which

include the guide rails 64 and support rails 62 or 62A are usually welded or bolted onto a conveyor frame in a manner known in the art.

The conveyor system in Figures 7 and 8 shows the preferred method of driving the chain 40, by means of a drive screw 68. The drive screw 68 is mounted on a drive shaft 70, which extends beneath the chain 40 with its axis parallel to the direction of travel. When the drive shaft 70 rotates in a counter-clockwise direction as indicated by the arrow in Figure 8, it pushes the lower guide wheels 26 and drives the chain 40 to the left. The drive screw 68 imparts some lateral force to the links 10, but the guide rails 64 keep the chain 40 travelling along a straight forward path. Since this drive screw 68 is located somewhere in the middle of the conveyor, it is pulling part of the chain 40 and pushing part of the chain 40. This would not be possible with other chain designs, because, if they were pushed, they would buckle and get wedged in the guide rails 64. However, with this chain, since each link carries its own guide wheels and support wheels, and since the axes of the pair of pivoting support wheels (or load-carrying wheels) and of the guide wheels for each link intersect at the same point, this chain can be pushed or pulled without becoming wedged against the guide rails 64. Therefore, it is also possible to reverse the direction of this conveyor by reversing the direction of rotation of the screw and driving the chain 40 backwards, again with no jamming problems. However, if the chain 40 is driven backwards, the scrapers 38 will not serve their function of clearing debris from the tracks 66, 66A as efficiently as they do in the forward direction.

The conveyor system shown in Figure 7 shows the chain 40 making lateral curves at both ends of the conveyor. It is contemplated that the chain may make such curves at various positions along its length as needed to perform its functions. For example, the chain 40 may travel up and down several bays to make a closed loop throughout an entire assembly plant.

One of the advantages of this chain is that it can make tight lateral turns without requiring the use of a wheel turn. A chain made up of the links of Figure 1, when made in a two- inch pitch size (the pitch being the distance between the axes of the chain pins) , can make a lateral turn having a radius of 5.75 inches. (The radius of the turn is measured from the center of the turn to the centerline of the chain.) This is a much tighter turn than can be made with most existing chains. The conveyor system shown in Figure 9 shares with the screw drive arrangement the advantage that the entire chain 40 can be used for conveying at any one time. This is very important, because it means that the same amount of conveying can be done with half the amount of chain. In this case, the drive sprocket 72 and the idler sprocket 74 rotate about vertical axes. Actually, an idler sprocket is not required, because the chain could simply be guided around a curved track 66A at that end. Tht sprocket teeth 76 engage the lower guide wheels 26 on the links 10 to drive the chain 40. Figure 10 shows the chain 40 being driven in a more conventional manner, by a drive sprocket 78 which rotates about a horizontal axis. The drive sprocket 78 is actually a double sprocket, that is two sprockets rotating about the same axis. The sprocket teeth 82 engage the support wheels 20, 22 of each link to drive the chain forward, and, of course, the idler sprocket 80, which also rotates about a horizontal axis, also has teeth 82 that engage the support wheels 20, 22. Again, the idler sprocket is not required, because the guide track can simply be curved to guide the chain around that end of the conveyor. This chain 40 is designed so that it can be driven by standard off-the-shelf sprockets. As with the other conveyor arrangements, the support wheels 20, 22 ride on the support rails 62, 62A, and the guide wheels 24, 26 fit between the guide rails 64. However, with this drive arrangement, only one guide wheel is required per link, since the lower guide wheel is not needed

for driving the link as in the other drive arrangements. In this arrangement, less than half of the chain can be used to convey products at any given time, because the rest of the chain is passing over the drive and idler sprockets 78, 80 or is on the return run below the top surface of the conveyor. However, even in this arrangement, the chain 40 has many advantages over prior art chains. For example, only a single type of link 10 is required to form the chain, whereas the prior art generally requires two types of links — one to carry the guide wheels and one to carry the support wheels. It has a superior bearing arrangement for the flexing portion of the chain, because the chain pin 50 is fixed in the vertical pin 42, and, when the links 10 flex relative to each other, they use the entire cylindrical bearing surface between the vertical pin 42 and the vertical bore 34 to bear the forces, whereas prior art designs depended on the chain pin shifting in an elongated bore in the links, which provided a much smaller bearing surface area. Also, the arrangement for pin retention in this design is improved over chains which require cotter pins or other retention devices which can break or fall out and which do not provide as good a bearing surface as do the 0-ring retainers in the present design.

Figures 11 and 12 show a second embodiment of the invention, in which the drive screw has been skewed at an angle to the axis and direction of travel of the chain, which permits one of the guide wheels to be eliminated, thereby reducing the cost of the chain. Elements of the second embodiment shown in Figures 11 and 12 are given numbers corresponding to the numbers of the elements in the first embodiment.

The chain link 110 of the second embodiment is identical to the chain link 10 in the previous figures, except that, instead of having upper and lower guide wheels 24, 26, it has only a single guide wheel 124, which engages both the drive screw 168 and the guide rail 164. The rest of the conveyor in the second embodiment is identical to the screw-driven

conveyor shown in Figures 7 and 8, except that, in this case, the screw 168 has left-hand threads instead of right-hand threads, and the axis of the screw 168 is rotated counter¬ clockwise by an angle alpha (the skew angle) , as shown in Figure 11. (If the screw 168 had right-hand threads, its axis would be rotated clockwise by a skew angle alpha.) The angle alpha is preferably equal to or slightly greater than the lead angle of the screw 168, which is labelled as beta in Figure 11. With the screw axis rotated as shown, the direction of the force imparted to the chain by the screw will be very close to the direction in which the screw is travelling. This will eliminate most of the lateral forces which were present when the axis of the screw and the direction of travel of the chain were the same. If the direction of force imparted to the chain by the screw and the direction of travel of the chain were equal, then there would be no lateral force on the chain, which would be ideal. Making the skew angle alpha exactly equal to the lead angle beta of the screw 168 would be ideal in the absence of friction forces. However, in order to account for frictional forces, the skew angle alpha should preferably be slightly greater than the lead angle beta. If the skew angle alpha is slightly greater than is necessary in order for the force to be applied exactly in the direction of travel of the chain, then it will create a lateral force on the chain 110 tending to push the guide wheel 124 of the chain 110 against the left side of the guide rail 164, which creates no problem.

As the screw 168 of Figure 11 rotates in a clockwise direction, it pushes the chain forward, up the page. The clockwise rotation of the screw 168 imparts a counter¬ clockwise rotation to the guide wheel 124. If the screw 168 were not skewed, it would cause the guide wheel 124 to push against the right side of the guide rail 164, and, since the guide wheel 124 is rotating counterclockwise, it would be dragging against the right side of the guide rail 164,

creating problems. However, with the screw 168 skewed at an angle alpha which is greater than the lead angle beta, the guide wheel 124 will either roll between the guide rails 164 or will be pushed slightly against the left guide rail 164. Since the guide wheel 124 is rotating in a counterclockwise direction, it will simply roll along the left guide rail.

Figure 12 shows the guide wheel 124 rolling between the two guide rails 164. While it is not clearly shown in Figure 12, there is a clearance fit between the guide wheel 124 and the guide tracks 164, so the guide wheel can only contact one guide track 164 at a time. This is also true of the previous embodiment.

Since Figure 12 is a view from the front of the chain, it shows the right guide rail on the left and the left guide rail on the right. As the screw 168 rotates to drive the chain 100 of Figure 12 forward (out of the page toward the reader) , it imparts a counter-clockwise rotation to the guide wheel 124 as indicated by the arrow in Figure 12, and the guide wheel 124 will readily roll along the left guide rail 164 (which is on the right side of Figure 12) . It can be seen in Figure 12 that the guide wheel 124 has a height which is greater than the guide wheel 24 of the previous embodiment. This is necessary, because the guide wheel 124 must both run in the guide track and must extend below the guide track to engage the threads of the screw 168.

It will be obvious to those skilled in the art that many modifications may be made to the embodiments described above without departing from the scope of the present invention.