Field of the invention

This invention relates to a conveyor assembly having a conveyor belt caused to follow an endless path part of which is formed by a helical conveying path consisting of a plurality of tiers arranged one on top of another in a stack.

Background to the invention

Known conveyor assemblies of this sort are disclosed in EP 0293095 and US 3938651. In these known conveyor assemblies/ the conveyor belt is driven, at least in part, within the stack. This is done either by applying drive to the lowermost tier of the stack (where the belt emerges from the stack) or by utilising a central drive drum around which the tiers of the stack extend and which applies drive to the inner peripheries of the tiers of the belt. Generally, such belts are also driven at a location external to the stack, and this double drive necessitates the provision of some form of take-up device to accommodate variations in belt tension. In other known assemblies the stack is driven by a separate ball drive system in which balls are enclosed in channel sections and are used to drive a chain system which in turn engages the lower part of the conveyor stack (described in US Patent

4,565,282). This is extremely complicated and is fraught with problems when operating at low temperatures (ie -

-0°C}. An aim of the present invention is tc provide an improved form of drive means for driving the conveyor belt.

Disclosure of the invention

According to the invention a conveyor assembly has a conveyor belt caused to follow an endless path part of which is formed by a helical conveying path consisting of a plurality of tiers arranged on top of one another in a stack, the edges of the belt having upstanding projections which act to space adjacent tiers of the stack, and drive means which drive the belt around the endless path and which apply drive to the belt at a location other than where the belt follows the helical conveying path. Hence, in the invention the drive means drive the belt at a location outside the stack, and it is thought that this will have advantages of ease of accessibility, simplicity and cheapness and better application of drive to the belt. A single drive means, at a location external to the stack, avoids any build-up of tension in the belt (which can happen when a double drive is employed) and avoids the need for any form of device for taking up belt tension.

The base of the stack may be supported by a turntable which is rotatably mounted so that in use the turntable supports and is rotated by the belt. The turntable thus freewheels, in contrast to known arrangements where the base of the stack is driven. The turntable may comprise inner and outer annular rings respectively supporting the inner and outer peripheries of the tiers, and these rincs may if desired be interconnected so that they rotate at

the same rotational speed. The inner and outer rings may alternatively be separate and therefore capable of rotating at different rotational speeds, to cope with differing speeds of the inner and outer peripheries.

The belt preferably descends the stack, being delivered to the stack at the top thereof and being drawn off the stack at the bottom. Although the belt preferably decends the stack it can also be allowed to ascend the stack if required.

In the preferred embodiment, the belt is driven at a location where the belt approaches the infeed to the stack, and this location is preferably where the belt undergoes a change of direction of 180°.

The drive means may comprise a rotatably driven hub having radial bores accommodating drive pins, the radially inner ends of the pins engaging an eccentric member as the hub rotates to cause the pins to move in the bores between radially projecting positions, in which the pins apply a drive to the belt, and retracted positions in which the pins are retracted from the belt to allow the latter to move away from the drive means. The hub may be one of two such hubs which are mounted on a common shaft which drive, through the respective sets of pins, the two sides of the belt.

The drive can be by other means as well as the eccentric member pin arrangement. Using a belt which expands on the outside allows a minimum pitch on the links which means that a normal toothed sprocket could be used to drive sucn a belt.

The conveyor assembly is particularly suitable for conveying a food product, and the spaces between the tiers are then dimensioned to suit the product being conveyed. The product is preferably treated as it moves along the helical stack. This treatment may be heating, drying or chilling, but is preferably freezing.

A conveyor■ ssembly according to the invention will now be described, by way of example, with reference to the accompanying drawings in which:-

Figure 1 is a perspective view of the conveyor assembly,

Figure 2 is a perspective view of a turntable support which supports a stack of tiers of a conveyor belt,

Figure 3 is a detailed view cf drive means for the conveyor belt, and

Figure 4 is a fragmentary sectional view on the line IV-IV of Figure 3.

Referring to Figure 1 , the conveyor assembly comprises a conveyor belt 10 guided around an endless path part of which is formed by a helical conveying path consisting of a plurality of tiers arranged one on top of another so as tc form a stack 12.

The edges of the belt have upstanding segmented projections which act to space adjacent tiers of the belt apart at a vertical distance to accommodate products being conveyed through the stack. The belt also has a base made of segmented elements which enable the belt to change direction in a horizontal plane as is required for the

belt to move around the helical conveying path.

The base of the stack is supported by the turntable support shown in Figure 2. This comprises a radially inner ring (not shown) supported for rotary sliding movement on a circular fixed rail 14 supported by legs 16. Similarly, an outer annular ring (not shown) is supported for rotary sliding movement on a circular fixed outer rail 18 supported on legs 20. The inner and outer rings support the inner and outer peripheries of the lowermost tier of the stack 12, and the ability of the inner and outer rings to rotate on their respective circular rails 14, 18 enables the conveyor belt to move around its helical conveying path in the stack and to be drawn smoothly away from the base of the stack. The inner and outer rings are interconnected by radial spokes or the like.

The conveyor belt 10 is driven at the location shown at 22 in Figure 1, where the belt changes its direction of movement through 180". The drive means at the location 22 comprise a sprocket 24 (Figure 4) which is driven by a chain (not shown) and which is mounted on a drive shaft 26. Each end of the shaft 26 carries a drive hub 28 which has a plurality of angularly spaced radial bores, each accommodating a drive pin 30 urged by a corresponding spring towards a radially inner position. The inner peripheries of the pins engage the outer periphery of a circular plate 32 which is fixed and is eccentric with respect to the shaft 26. Hence, as each hub 28 rotates, the eccentric shape of the plate 32 drives the pins 30 to projecting positions in which the pins engage recesses in the corresponding side of the belt in order to drive the latter. This is shown in the lower part of Figure 3. The

upper part of Figure 3 shows the pins in their withdrawn or retracted positions.

It will be appreciated that the shaft 26 is driven anti¬ clockwise in Figure 3, this drive causing the belt to approach the infeed of the stack 12, to pass around the helical path of the stack and to move from the outfeed of the stack to the location 22.