GB2129752A - Roller conveyors for single-layer ceramic firing kilns - Google Patents

Abstract

A roller conveyor 2 comprising a plurality of equidistant hollow metal or ceramic rollers, at the drive end of each of which is provided a friction clutch device 15, from the driven element 13 of which there extend means 17 for rotating the rollers, together with retention means 22 for this latter, which are arranged to prevent its withdrawal from the respective firing tunnel 1. <IMAGE>

Description

SPECIFICATION Roller conveyers for single-layer ceramic firing kilns The ceramic tile manufacturing industry has for some time used so-called single-layer firing kilns comprising a tunnel provided with a longitudinal roller conveyor for transferring the material therealong.

The known roller conveyor of this type, on which an alignment or layer of ceramic tiles to be fired is formed, comprise a plurality of equidistant hollow rollers, which can be either of metal or ceramic, and of which the opposite ends emerge beyond the side walls of the tunnel.

Each roller is supported at one end by a pair of idler wheels, whereas its other end rests on a pair of drive wheels which are driven by a chain and associated sprocket wheels.

Under normal or regular operating conditions, the friction between the pairs of drive wheels and the corresponding ends of the rollers enables these latter to be kept rotating and thus to transfer the material along the firing kiln.

However, when two or more consecutive tiles along the alignment come into contact or become superposed, the forces in play become such that the drive wheels slip on the corresponding rollers, which remain stationary.

In less serious cases, correct operation of the roller conveyor is restored automatically after only a short time, whereas in more serious cases action has to be taken from the outside with long spikes or pusher rods in order to avoid greater difficulties.

Moreover, because the rollers of such known roller conveyors or tables are simply rested on said opposing pairs of wheels, two opposing longitudinal retention plates are fitted in order to prevent the rollers escaping sidewards from the conveyor.

The wide use of these roller conveyors in this industry has brought to light the drawbacks summarised hereinafter.

In this respect, it has been found that the rollers of such roller conveyors become halted not only for the said reasons relating to factors internal to the firing kiln, but also due to factors external to the kiln, for example when dirt, moisture, grease or other foreign bodies become deposited on the drive wheels or on the corresponding ends of the rollers, to lower the friction between said contacting parts until mutual slippage occurs, leading to stoppage of the rollers.

This also obviously leads to stoppage of the corresponding tiles, which then become struck by those upstream and can be irreparably damaged, this also possibly leading to the superposing of tiles, and the at least temporary stoppage of further rollers.

Furthermore, these known roller conveyers have proved to be excessively complicated due to the presence of the two lateral roller retention plates.

It is an object of the invention to provide a roller conveyor for single-layer ceramic kilns which obviates or minimises the aforesaid drawbacks by means of a simple and rational constructional design.

Accordingly, the invention consists in a roller conveyor for a single-layer ceramic firing kiln, of the type comprising a plurality of equidistant hollow metal or ceramic rollers, the opposing ends of which are arranged to emerge from the side walls of an associated ceramic material firing tunnel, for rotation by a drive system comprising a chain, wherein, a constantly engaged friction clutch is at the drive end of each roller, said clutch device being arranged to drive the corresponding roller during correct transfer of the material along the tunnel, but is arranged to slip when said transfer is irregular, and from the driven element of which there branch suitable means for rotating the roller, and a retention member for this latter which is arranged to prevent its withdrawal from the firing tunnel.

In a first embodiment, the friction clutch device comprises at least one elastically loaded ball which is slidable transversely to a rotatable pivot pin coaxial to the roller, and is partly inserted in a groove in a drive sprocket wheel which is driven by a chain and is mounted in the required position on the outer end of the pivot pin.

The other end of said pivot pin comprises two appendices for driving the corresponding roller, and a resilient member arranged to prevent the roller withdrawing from its end supports.

In another embodiment, the sprocket and rotatable pivot pin are fixed together, and the friction clutch device is in the form of a spring of adjustable loading which acts on a ring rotatably mounted on the pivot pin and from which said drive appendices and resilient anti-withdrawal member project.

In a further embodiment, the friction clutch device comprises at least one elastically loaded ball which is slidable transversely to the rotatable pivot pin and in the case of ceramic rollers is arranged for partial insertion into a seat in a resilient bush mounted on the pivot pin and locked on the roller, whereas in the case of metal rollers it is arranged for insertion into a seat in the roller, which is directly mounted on the pivot pin.

In this specific case, the corresponding end of the roller is supported by the rotatable pivot pin, so that the support wheels are dispensed with, and said at least one ball acts as an anti-withdrawal member for the same roller.

In order that the invention may be more clearly understood, reference will now be made to the accompanying drawings which illustrate certain details and preferred embodiments of the invention by way of nonlimiting example, and in which: Figure 1 is a cross-section through a first embodiment of the invention, Figure 2 is an exploded perspective view of the drive and anti-withdrawal members provided at the drive end of each roller of the roller conveyor of Figure 1, Figure 3 is a partial cross-section through a further embodiment of the roller conveyor or table, and Figures 4 and 5 show a further embodiment of the invention which, as in the case of the preceding embodiments, can be used either for ceramic rollers or for metal rollers.

Referring now to the drawings, these, and in particular Figures 1 and 2, show a normal single layer ceramic kiln comprising a firing tunnel 1 and a longitudinal roller conveyor or table 2 for transferring the ceramic material through said tunnel.

The roller conveyor 2 is composed of a plurality of similar equidistant hollow rollers which can be of metal, ceramic or any other material able to withstand the temperature in the tunnel 1.

In Figures 1 and 2, each roller is of the ceramic type, and its opposing ends emerge from the side walls of the tunnel where suitable apertures having a diameter greater than the roller diameter are provided. The end of each roller is covered by a metal sleeve 3 the under part of which rests on two idler wheels 4 mounted on a longitudinal support 5 disposed outside the corresponding wall of the tunnel.

From the longitudinal support 5, which is shown to the right in Figure 1 and defines the drive side of the roller conveyor, there branches a strut 6 which extends beyond the corresponding end of the roller 2 in order to support a bar 7.

Instead of the bar, there may be provided a plurality of blocks rigid with the strut, and of number equal to the number of rollers in the roller conveyor.

A guide 8 for the upper rectilinear portion of a suitably motorised drive chain 9 is disposed to the side of the outer vertical wall of the bar, by way of a suitable support.

On the bar 7 there is provided for each roller 2 a bearing 10, into the casing of which there is screwed from below a screw 11 passing freely through the bar.

The correct positioning of the bearing is determined by two small pins 12 provided on the bar, and housed in respective seats in the bearing.

This latter supports a rotatable pivot pin 13 coaxial to its roller 2 and having mounted in the required position on its outer end a sprocket wheel 14 which engages with the underlying chain 9.

In the through bore of the sprocket wheel there is provided a circumferential groove or channel which partially houses two opposing balls 15 slidably inserted in a diametrical bore of the pivot pin 13. A suitably loaded compression spring 16 is inserted between the two balls in the same diametrical bore.

When the sprocket wheel 14 is removed from the pivot pin 13, the balls 15 are prevented from escaping by suitable retention elements provided on the mouths of said diametrical bore.

The balls 15 define a type of friction clutch between the sprocket wheel and pivot pin, said friction clutch being preset in such a manner as to enable the roller to be driven during correct transfer of the material along the tunnel, while being designed to slip, with consequent stoppage of the roller, when said transfer is irregular.

Several pairs of opposing balls 15 can also be provided, or alternatively it is also possible to provide for each diametrical bore of the pivot pin 13 a single ball, of which the elastic load due to the spring 16 can be adjusted by means of a grub screw provided in the opposite mouth of the respective diametrical bore.

The inner end of each pivot pin 13 is in the form of an enlarged head from which there branch two pins 17 parallel to the axis of the pivot pin.

The ends of these pins are freely inserted, with a certain degree of slack, into two diametrically opposing circular apertures 18 provided in a disc 19 which closes the mouth of the roller 2 (Figure 2). The disc 19 is locked axially and torsionally to the ceramic roller 2 by two resilient strips 20 forcibly inserted into the roller. The disc 19 is also provided, either outside or inside the circumference defined by the circular apertures 18, with a through bore 21 into which there is inserted a profiled retention member 22 branching from the pivot pin 13, and the purpose of which is to prevent the roller withdrawing from its supports 4.

As clearly shown, the retention member 22 is in the form of a piece or rod or steel wire which may be piano wire, having two humped portions pointing in the same direction and designed to lie on one side and the other of the disc. The retention member 22 is inserted and withdrawn into and from said through bore 21 by snap action.

The advantageous presence of the profiled wire 22 enables the two opposing plates used in the prior art for correctly retaining the rollers 2 on the wheel supports 4 to be dispensed with.

In the case of metal rollers, the elements of the invention remain unchanged, with the single exception ofthe sleeves 3, in that said metal rollers are directly rested on the wheel supports 4.

At this point it should be noted that the replacement of a roller and the respective friction clutch device, or of only one of said two combined elements, is an extremely simple operation, this being contributed to by the advantageous arrangement of the endless chain 9 which lies entirely below the level of the roller conveyor.

The same advantageous results are also obtained in the case of a roller conveyor according to the alternative embodiment shown in Figure 3.

The roller conveyor is again composed of a plurality of ceramic rollers which are supported at each end by a pair of idler wheels. Said rollers can also be of metal or any other material able to withstand high temperature.

From this Figure, it can be seen that the drive sprocket wheel 14 is fixed on the rotatable pivot pin 13, whereas the friction clutch device is provided at the inner end of the pivot pin 13.

At this end, the pivot pin terminates in a cap 23 which acts as a support seat for a ring 24 rotatably mounted on the pivot pin by way of a self-lubricating bush 25.

Against the ring 24 there presses a washer 26 on which there acts a compression spring 27 mounted on the pivot pin 13 and resting at its other end against a shoulder of said pivot pin.

From the inner transverse face of the cap there branch two pins 17 and a profiled wire 22 which are inserted, as referred to above, into the disc 19 rigid with the roller2.

As will be apparent, the friction generated by the described friction clutch device can be adjusted at will by disposing suitable spacers between the washer 26 and spring 27.

As in the preceding embodiments, the embodi ment of the roller conveyor shown in Figures 4 and 5 comprises a friction clutch device at the drive end of each component roller.

In contrast to the preceding embodiments however, in this specific case the free end of the roller is directly supported by the friction clutch device, so that the corresponding pair of idler wheels is dispensed with.

Although not shown, it is apparent that the other end of each roller rests on two idler wheels.

It should be noted that by virtue of this type of support, which is certainly more rigid than the preceding, the roller conveyor of Figures 4 and 5 is particularly suitable for single-layer ceramic kilns operating at relatively low temperature.

From Figure 4 it can be seen that the sprocket wheel 14 is fixed on to the outer end of the rotatable pivot pin 13, whereas the friction clutch device is provided on the other end of said pivot pin.

At this end, said pivot pin comprises two mutually orthogonal adjacent diametrical through bores, in each of which two opposing balls 28 are slidably inserted.

These latter are prevented from escaping from the corresponding bore by means of suitable inward projections at the mouths of these latter. Said two pairs of opposing balls are urged elastically outwards by respective springs 29, and are partly inserted into two circumferential grooves 30 provided on the inside of a collar 31.

This latter is mounted in the required position on the pivot pin 13 and rests against a shoulder thereon.

From the inner end of the collar 31 there branches a bush 32 which is made resilient by means of a longitudinal siot and is locked by means of a screw on to the corresponding free end of a ceramic roller 102. As can be seen, a shoulder is provided between the collar and bush for the correct insertion of the ceramic roller.

In Figures, the exclusion of the collar 31 enables the same friction clutch to be used for metal rollers 202.

In this specific case, the balls 28 are partly inserted into suitable through bores 33 provided in the corresponding end of the metal roller 202.

It will be apparent that the through bores 33 may be replaced by inner circumferential grooves.

It is also possible to make the friction force generated by the balls 28 adjustable by simply providing a single ball inside each diametrical bore of the pivot pin 13, and screwing a suitable grub screw into the opposite mouth of said diametrical bore so that it acts against the respective compression spring 29.

Claims (11)

1. Arollerconveyorfora single-layer ceramic firing kiln of the type comprising a plurality of equidistant hollow metal or ceramic rollers, the opposing ends of which are arranged to emerge form the side walls of an associated ceramic material firing tunnel, for rotation by a drive system comprising a chain wherein, a constantly engaged friction clutch is at the drive end of each roller, said clutch device being arranged to drive the corresponding roller during correct transfer of the material along the tunnel, but is arranged to slip when said transfer is irregular, and from the driven element of which there branch suitable means for rotating the roller, and a retention memberforthis latter which is arranged to prevent its withdrawal from the firing tunnel.

2. A roller conveyor as claimed in claim 1, wherein the friction clutch device comprises a rotatable pivot pin, which is coaxial to the respective roller and mounted on a removable bearing, and which comprises at least one diametrical bore in which there is slidably inserted at least one ball which is elastically urged outwards and is partly inserted in a circumferential groove provided in a drive sprocket wheel which engages with a lower chain and is mounted in the required position on said rotatable pivot pin.

3. A roller conveyor as claimed in claim 1, wherein the friction clutch device comprises a rotatable pivot pin, which is coaxial to the respective roller and mounted on a removable bearing, and of which one end has a drive sprocket wheel fixed thereon, whereas on the other end there is rotatably mounted a ring which is constantly pressed against an end cap by a suitable compression spring, this latter being mounted on said pivot pin, and being of adjustable load by interposing suitable washers.

4. A roller conveyor as claimed in claim 1, wherein the drive means comprise two diametrically opposed pins which are parallel to the axis of the corresponding roller and project from said rotatable pivot pin or rotatable ring, to be inserted with a certain degree of transverse slack into two corresponding apertures in a disc fixed to the roller mouth.

5. A roller conveyor as claimed in claim 1, wherein the retention member comprises a length of rod of wire which contains two humped portions extending in the same direction and arranged to lie on one side and the other of said disc by way of a further aperture provided in this latter, said further aperture being disposed either external or internal to the circumference defined by the two apertures which receive said pins.

6. A roller conveyor as claimed in claim 1, wherein the friction clutch device comprises a rotatable pivot pin, which is coaxial to the respective roller and mounted in a removable bearing, and of which one end has fixed thereon a drive sprocket wheel while the other end comprises at least one diametrical bore in which there is slidably disposed at least one ball which is urged elastically outwards and is partly inserted in a seat which, in the case of a metal roller, is provided in the actual wall of the roller, whereas in the case of a ceramic roller is provided in the wall of a sleeve, this latter being mounted in the required position on the pivot pin and comprising a resilient bush which is clamped on to the roller.

7. A roller conveyor as claimed in claim 2 or 6, wherein the elastic load of said at least one ball can be adjusted by a grub screw in the opposing mouth of said at least one diametrical bore.

8. A roller conveyor as claimed in claim 1, wherein the chain is arranged to drive on drive sprocket wheels of the rollers and lies completely below these latter, in order to enable these latter and the respective friction clutch devices to be easily replaced.

9. A roller conveyor for a single-layer ceramic firing kiln, substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.

10. A roller conveyor for a single-layer ceramic firing kiln, substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings.

11. A roller conveyor for a single-layer ceramic firing kiln, substantially as hereinbefore described with reference to Figures 4 and 5 of the accompanying drawings.