GB2067498A - Roller driving arrangement - Google Patents

Abstract

This invention relates to a device for axially locating a driving spool (22) one drive shaft (18) of a line shaft live roller conveyor (10) having rollers (12) driven by elastomeric drive belts (24) extending from corresponding spools (22) on the shaft (18) extending transversely beneath them. There is a relatively loose frictional fit between the spools (22) and the drive shaft (18), and the twist of each drive belt (24) between the spool (22) and the roller (12) results in a tendency for the spools (22) to shift along the drive shaft (18) with the intermittent application of load. The present invention provides a locating device (28) with a C-shaped resilient body (32) with a mouth (34) which may be transversely snapped over the drive shaft (18) to grip the drive shaft (18) to securely retain it in the desired axial position. <IMAGE>

Description

SPECIFICATION A line shaft live roller conveyor spool locating device This invention relates to line shaft live roller conveyors and more particularly to a locating device for axially locating the drive spools on the drive shaft thereof.

Line shaft live roller conveyors have a number of rollers arranged to carry boxes or other individual articles along a pass line. Each roller is individually driven by an elastomeric drive belt extending around a spool on a common line or drive shaft located beneath the rollers. In order to provide for accumulation of the articles on the conveyor, it is necessary that one or more of the rollers be able to stop while the others keep rotating. This independent roller operation is provided for by having the individual driving spools which are spaced along the drive shaft only lightly frictionally engaged by the drive shaft so that they may slip if necessary when the roller driven by that spool is stopped by an article sitting on it.

As is well known in the art, this type of line shaft live roller conveyor produces a phenomenon whereby the spools move axially downstream along the drive shaft when no load is applied to the driven rollers and then shift upstream to a position beneath the driven rollers when load is applied and this phenomenon is known as "axial shift". While this phenomenon is not completely understood, as discussed in Canadian Patent 930,686 to Fleischauer et al. which issued July 24, 1973, it has been thought to be as a result of the tensioning imbalance on the drive belt and the fact that the spools are able to cock slightly due to the play between them and the drive shaft. In Canadian Patent 930,686, this phenomenon of "axial shift" was presented as an advantage in that it has a self-tensioning effect on the drive belt as the load is applied.However, in practice, it has been found to be unacceptable in that it eventually results in the elastomeric belts being stretched to the point where they lose their power and have to be replaced.

This problem is aggravated by the fact that the spools shift closer to their respective roller when the load is applied, rather than further away. This has led to the use of cylindrical plastic spacers located on the drive shaft between the spools to prevent "axial shift".

However, it has been found that these spacers have several disadvantages. The length of the spacers must correspond to the desired distance between the rollers and, if it is necessary to change the roller spacing, the spacers and spools must all be taken off the drive shaft and the spacers replaced.

Similarly, this must also be done if there is a failure of one of the spacers requiring that it be replaced.

More importantly, it has been found that the independent operation of the individual rollers may be lost, at least to some extent, by forces being transmitted through the spacers between adjacent spools. When conveyor accumulation occurs and a box is stopped on a roller, the phenomenon of "axial shift" mentioned above tends to move the spool driving that roller in a downstream direction as it comes to a stop. However, when cylindrical spacers are located on the drive shaft between each of the spools, this jams all of the spacers and spools in that section of the conveyortogetherwhich tends to prevent the roller and other adjacent rollers upon which the box may be sitting from stopping.In other words, the line pressure on the box is increased because the force being exerted on the box is greater than that originating only from the rollers upon which it is sitting. This detrimentally effects the operation of the means used to stop the box and therefore, the whole accumulation operation of the conveyor.

It is an object of the present invention to at least partially overcome these disadvantages by providing a locating device which may be manually snapped onto the drive shaft downstream of a spool to axially locate that spool in a desired position along the drive shaft without making contact with any other spool, and which may be easily relocated to shift the axial position of the spool on the drive shaft.

Accordingly, the invention provides a device for axially locating a spool on a cylindrical drive shaft in a line shaft live roller conveyor having a plurality of said rollers which form a pass line thereon to carry objects along the conveyor, said drive shaft extending generally transversely to said rollers and carrying a plurality of said spools, each spool being rotated or not rotated by said shaft depending upon the degree of frictional engagement therebetween, and a plurality of endless elastomeric drive belts, each having a round cross section and each extending around one of said spools and through a circumferential groove around a respective one of said rollers, said locating device having a C-shaped body which has a mouth, the body being formed of resilient material and extending around more than 180 to provide the mouth with a height significantly less than the outside diameter of said drive shaft and being of a size whereby it may be manually snapped transversely onto said drive shaft to a position where it grips the drive shaft with sufficient force to prevent it being axially displaced or accidently dislodged from the drive shaft by the normal operating force of a spool, although allowing itto be manually relocated along the drive shaft, and said locating device normally being positioned on the drive shaft adjacent said spool to locate the spool against downstream axial shifting along the drive shaft.

Further objects and advantages of the invention will become clear from the following description taken together with the accompanying drawings.

Figure lisa perspective view of a section of a line shaft live roller conveyor utilizing locating devices according to a preferred embodiment of the invention; Figure 2 is an enlarged elevation view showing one of the locating devices seen in Figure 1 locating a spool on the drive shaft; and Figure 3 is a perspective view of the locating device seen in Figures 1 and 2.

Reference is first made to Figure 1 which shows a portion of a line shaft live roller conveyor 10 having a number of rollers 12 supported by two side frame members 14,16. The upper surfaces ofthe rollers 12 form a conveyor pass line along which boxes or other articles are transported. A line or drive shaft 18, driven by a power source (not shown) is located beneath the rollers 12 and extends transversely to them. The drive shaft 18 carries a number of spools 22, and an elastomeric drive belt 24 having a uniform round cross section extends from each spool 22 through a groove 26 in a respective one of the rollers 12.

It is necessaryforthe successful operation of this type of conveyor that provision be made for the accumulation of boxes on it, and in order to facilitate accumulation, it is desirable that only the particular rollers under a box stop rotating when that box is stopped on the conveyor by other means (not shown). It is well known in the art to provide for this by having a relatively loose fit between the spools 22 and the line shaft or drive shaft 18. Thus, when a particular roller 12 is stopped from rotating by a box being stopped on it, the spool 22 from which it is driven slips on the drive shaft 18 to provide this individual or independent roller drive function.However, as may be seen, the location and alignment of the drive shaft 18 requires that the rotational axes of the spools 22 be at an angle of substantially 90 to that of the rollers 12. This factor, combined with the necessarily loose frictional fit of the spools 22 on the drive shaft 18, results in the undesirable phenomenon mentioned above of axial shifting of the spools 22 on the line shaft 18. In a no-load or idling state, each rotating spool 22 tends to slip on the drive shaft to position itself slightly downstream from the roller 12 it is driving. When a load is applied to the roller, the driving spool would be drawn upstream to a position more directly beneath the roller.According to the present invention, this phenomenon of axial shifting is prevented by locating devices 28 which are snapped onto the drive shaft adjacent the downstream side 30 of each spool 22.

In this embodiment, the locating device has a body 32 with a uniform C-shaped cross section and a mouth 34. The shape of the inner surface 36 is slightly off-cylindrical when the locating device is in the unstressed state, whereby when it is stressed to resiliently engage the cylindrical drive shaft 18, it assumes a cylindrical shape to grip the outer surface of the drive shaft 18. While the inner surface 36 is smooth in the embodiment shown, it may be textured or otherwise designed to improve its grip on the outer surface of the drive shaft 18 during use.

The C-shaped body 32 extends around about 240 to provide the mouth 34 with a height in the unstressed state which is significantly less than the diameter of the drive shaft 18. As this dimension, combined with the resiliency of the material, determines the amount of force required to install and remove the locating device, it may be varied depending upon the application. However, it will be apparent that the C-shaped body must extend around more than 180 in order to be securely retained in the installed position. The body 32 also has a smooth outer surface 38 and smooth side walls 40, 42 to minimize frictional forces arising on contact with a spool.While this embodi mentofthe invention is formed of DELRIN (a Registered Trade Mark for an acetate product containing an anti-static agent to avoid dirt accumulation), it may be formed of any suitable material providing the necessary strength and resiliency characteristics.

In use, the locating device 28 is snapped onto the drive shaft 18 by manually forcing ittransversely against the drive shaft 18 until the mouth 34 of the C-shaped body 32 expands sufficiently to accommodate the drive shaft. When it snaps over the drive shaft, the resiliency of the material causes the inner surface 36 to securely grip the drive shaft in a fixed position. A locating device 28 is positioned adjacent each spool 22 on the downstream side to locate the spool against downstream axial shifting of the spool when the load is removed from the rollers.The width of the body, together with its resiliency is selected to ensure that the locating device grips the drive shaft 18 with sufficient force to prevent it being axially displaced by the operating force of the spool, while at the same time allowing itto be manually relocated along the drive shaft.

Thus, while each locating device is in contact with a spool on its upstream side, there is no contact with any other spool which necessarily avoids the transmission of forces between adjacent spools by the locating devices. Furthermore, while the locating devices 28 are fixed to the drive shaft 18 and rotate with it and therefore will each have some effect on the adjacent spool 22 due to frictional contact between them, this effect will be the same for each spool and therefore may be taken into consideration in the design of the accumulation means for the conveyor 10. If the conveyor is reversible, then it will be apparent that it is necessary to position locating devices 28 on both sides of each spool 22 to prevent axial shifting in either direction.

The locating devices 28 according to the invention may also advantageously be used with the new so-called "self centering" type of line shaft live roller conveyor drive. Even if the locating devices are not required to prevent intermittent axial shifting of the spools 22, they may be used to slightly shift each spool 22 away from a position directly beneath the driven roller 12 to increase tension in the drive belt 24 to a desired value. It will be appreciated that the fact that each locating device 28 may be quickly and easily relocated on the drive shaft 18 by manually sliding it along makes this very useful to compensate.

for stretching of the elastomeric drive belts 24 which ultimately occurs after long periods of use.

Although tfle disclosure described and illustrates a preferred embodiment of the invention, it is to be understood that the invention is not restricted to this particular embodiment. Many variations and modifications will now occurto those skilled in the art. In particular, it will be apparent that locating devices having other shapes and sizes and formed of other materials may be used.

Claims (5)

1. A device for axially locating a spool on a cylindrical drive shaft in a line shaft live roller conveyor having a plurality of said rollers which form a pass line thereon to carry objects along the conveyor, said drive shaft extending generally transversely to said rollers and carrying a plurality of said spools, each spool being rotated or not rotated by said shaft depending upon the degree of frictional engagement therebetween, and a plurality of endless elastomeric drive belts, each having a round cross section and each extending around one of said spools and through a circumferential groove around a respective one of said rollers, said locating device having a C-shaped body which has a mouth, the body being formed of resilient material and extending around more than 1800 to provide the mouth with a height significantly less than the outside diameter of said drive shaft and being of a size whereby it may be manually snapped transversely onto said drive shaft to a position where it grips the drive shaft with sufficient force to prevent it being axially displaced or accidently dislodged from the drive shaft by the normal operating force of a spool, although allowing itto be manually relocated along the drive shaft, and said locating device normally being positioned on the drive shaft adjacent said spool to locate the spool against downstream axial shifting along the drive shaft.

2. A locating device as claimed in claim 1 wherein the body has a uniform C-shaped cross section, thereby providing an inner surface which is entirely in contact with the drive shaft in the engaged position, the body being of sufficient width to provide the desired gripping strength.

3. A locating device as claimed in claim 1 or 2, wherein the body has at least one smooth side wall to be in contact with said spool to minimize frictional forces between them.

4. A locating device as claimed in claim 1,2 or 3 wherein the body is formed of an acetate product containing an anti-static agent to avoid dirt accumulation.

5. A locating device substantially as herein described with reference to the accompanying drawings.