GB2078184A - Driven roller conveyor - Google Patents

Abstract

In driven roller conveyors it is necessary to enable the drive to slip when an accumulation takes place. This has conventionally involved both noise and wear. In accordance with the invention the drive from a longitudinal drive shaft 3 is passed to a roller 2 by means of a driven wheel, preferably a bevel gear 4a, engaging a contact surface, preferably an annular gear 5a, of a driven wheel 5b in driving contact with the roller 2. The contact surface 5a is provided with one or more gaps 6a which enable the drive transmission to be regularly interrupted and restored, so that on accumulation, the transmission only needs to slip until the gap 6a reaches the wheel 4a where the drive wheel 5b will stop. <IMAGE>

Description

SPECIFICATION Driven roller conveyor This invention relates to driven roller conveyors used for transporting articles and packages, e.g. in factories. These conveyors consist of a basic framework extending along the required transport route and carrying transverse rollers over which the articles are passed. In a driven roller conveyor, the rollers are powered, usually from a main power unit located at one end of the conveyor.

Many different methods have been used to drive the rollers and the most common system systems use a recirculating longitudinal belt or chain drive arranged to turn at least some of the rollers. The number of rollers which are driven is usually varied depending on the power required.

One big problem with driven roller conveyors concerns the interruption of the drive when articles on the conveyor begin to accumulate, e.g., if there is a blockage or if too many are being supplied to a particular handling area.

One system which has achieved considerable success uses a longitudinal drive shaft extending along one side of the conveyor. On. this shaft are mounted spindles which are relatively loose friction fit on the shaft. These spindles are connected to rollers which are to be driven by endless belts under tension, each belt passing through a half-turn before passing over the end of the roller, so that the drive is transmitted in a direction perpendicular to that of the shaft. Such a system is commercially available under the Trade Name "Poweroll". In such a system, an accumulation of goods on the conveyor prevents the rollers from turning and the small increased load on the spindles causes them to slip on the drive shaft. The drive to the rollers is thus governed by torque - a slight increase in torque leading to interruption of the drive.

This system relies on slippage of the spindles, which inevitably leads to wear and noise, and the wear in turn leads to inefficient transmission of power to the rollers.

I have now devised a simple transmission system which enables the power to be disengaged from rollers on which an article has become stationary because of accumulation on the conveyor which does not depend on slippage under increased torque. This transmission system isolates the roller from the drive shaft almost instantaneously and as no slippage is involved the system is comparatively silent and free from wear.

According to the present invention there is provided a driven roller conveyor comprising a series of transverse rollers at least some of which are driven by a longitudinal drive shaft, characterised in that drive is transmitted to a roller by a transmission system comprising a driving wheel rotatable with the drive shaft and one or more driven wheels rotatable with the roller, arranged and constructed so that the drive supplied to the roller is regularly interrupted and is restored by rotation of the roller.

In general, the regular interruption is achieved by interrupting a contact surface on a driven wheel at one point or at two or more points spaced radially from each other so that when the deformed portion faces the contacting wheel, contact is, at that point, broken.

In one preferred embodiment, the driving wheel rotatable with the drive shaft is arranged so that its driving surface can contact a face of an intermediate drive wheel mounted with its axis perpendicular to that of the drive shaft and parallel to that of the roller, the driving surface of the intermediate drive wheel being arranged to contact the roller and so drive it, the intermediate drive wheel being provided with a recess in the area contacted by the primary drive wheel, whereby driving contact with the primary drive wheel is interrupted at the point when the intermediate drive wheel is rotated so that the recess faces the drive wheel.

Alternative embodiments are envisaged in which, e.g., the intermediate drive wheel mentioned above contacts an annular sleeve on the roller, which sleeve is provided with one or more flats.

The above-mentioned embodiments generally relate to transmissions in which the drive is by friction, the wheels rotating against one another under a certain pressure which is either provided by the natural resilience of the material, or is alternatively supplied by the spring bias on the wheel mounting. In either situation the bias must be such that when the recess or flat on a driven wheel faces the contacting driving wheel, contact is indeed broken. Obviously too much resilience would means that the driving wheel might contact the recessed part of the surface and so still transmit power.

In an alternative preferred system, the wheels may be toothed, e.g., in the manner of a bevel gear. In this case, the recess or flat can constitute one or more shorter teeth, or even a local absence of teeth.

The drive interruption is achieved as follows.

Under normal running circumstances, with no accumulation of goods on the conveyor, the momentum of an article on the conveyor and also the drive supplied to it by rollers at the rear, ensures that a driven roller at the front of the article is rotated into re-engagement of the driving wheels. Thus, as soon as drive is disengaged by the recess or flat rotating to face the driving wheel, the recessed or flattened wheel is urged passed this position by the article and drive is reconnected. As soon as there is an accumulation of goods on the conveyor, a package will stop and there will then be no momentum acting on the rollers to reconnect the drive once it has been interrupted. Thus, as soon as the passage of an article along the conveyor is impeded, the power supplied to the rollers on which it stands is interrupted.

Once the accumulation on the conveyor has been cleared, drive can be connected simply by giving the stationary packages a slight push sufficient to turn the rollers and reengage the driven wheels.

Alternatively, a manually operated device may be provided to give an impulse to a driven wheel.

One preferred embodiment of the invention will now be described with reference to the accompanying drawings, in which Figure 1 represents a partial plan view of the conveyor from below; Figure 2 represents a partial side view along the line A-A; Figure 3 represents an oblique view of the driven wheel; and Figure 4 is a view similar to Figure 2 showing an alternative arrangement.

The conveyor comprises a longitudinal frame 1 carrying a plurality of transverse rollers 2 and a longitudinally extending drive shaft 3. Under the rollers intended to be driven, there are located on the drive shaft 3 driving wheels 4. The driving wheels 4 are arranged to be rotated solidly with the drive shaft 3 and to transmit their rotation to driven wheels 5 which in turn contact the rollers 2 and turn them.

Referring specifically to Figure 3, each driven wheel 5 is provided on one face with a recess 6 such that the driving wheel 4 will rotate the driven wheel 5 until the recess 6 faces it, whereupon contact between the driving wheel 4 and the driven wheel 5 is lost, but is regained on slight rotation of the roller 2.

Conveniently, the drive wheels 4 are formed from a resilient material such as synthetic rubber and the driven wheels 5 are formed from a suitable hardwearing rigid material, e.g., a plastics material such as nylon.

In operation the drive shaft 3 rotates about its axis, thus causing the drive wheels 4 to contact the driven wheels 5 and rotate them. At each point where the drive wheel 4 comes to face the recess 6 in the driven wheel 5, contact is interrupted, but further rotation of the e driven wheel 5, by virtue of inertia in the motion of a package over the rollers 2, moves the recess 6 passed the drive wheel 4 so that contact is restored. If the roller 2 is in contact with and restrained by a stationary item then the drive will slip until interruption of the drive by the recess 6, when the drive wheel will stop. If there is no movement of the article over the rollers 2, then drive is not restored until the article is urged along the conveyor.

In the alternative, and now preferred form of the invention illustrated in Figure 4, the friction drive between the driving wheel 4 and drive wheel 5 is replaced by a driving bevel gear 4a on the drive shaft 3 and in mesh with an annular gear 5a on driven wheel Sb. The annular gear 5a is interrupted at 6a to provide the interrupted drive.

By using a gear drive between the driving and driven wheels 4a and Sb, slippage between these wheels is prevented so that any slippage occurring before the interruption of the drive must be between the drive wheel Sb and the roller. This means that interruption is achieved with minimum delay and therefore minimum wear and noise.

If required, a restart of the drive may be achieved by means of a stroking device engaging directly on the gear 5a and manually operated to provide an impulse to engage normal drive by moving the gap 6a clear of the bevel gear 4a.

Various modifications may be made within the scope of the invention.

Claims (6)

1. A driven roller conveyor comprising a series of transverse rollers at least some of which are driven by a longitudinal drive shaft, characterised in that drive is transmitted to a roller by a transmission system comprising a driving wheel rotatable with the drive shaft and one or more driven wheels rotatable with the roller, arranged and constructed so that the drive supplied to the roller is regularly interrupted and is restored by rotation of the roller.

2. A conveyor as claimed in claim 1, in which the driven wheel has an interrupted annular drivereceiving zone normally in driving contact with a dive-transmitting zone of the driving wheel.

3. A conveyor as claimed in claim 2, in which the drive between the drive and driving wheels is frictional.

4. A conveyor as claimed in claim 2, in which the drive receiving zone is an annular gear with one or more gaps with no effective gear teeth, the drive transmitting zone of the driving wheel being a gear normally in mesh with the annular gear.

5. A conveyor as claimed in claim 2, 3 or 4, comprising a manually operated device to impart a rotary impulse to the driven wheel.

6. A driven roller conveyor substantially as hereinbefore described with reference to the accompanying drawings.