Vibratory conveyor device

Abstract: A materials handling device comprising a cascade of vibrating conveyors (61, 71, 81), each upstream conveyor (61, 71) being nestable in a downstream neighbour (71, 81) with clearance, and movable relative thereto from a nested condition in which product is conveyed from one conveyor to another, to a separated position in which product falls from the first conveyor into a gap between the adjacent conveyors. The invention avoids mechanical gates which are noisy, unreliable and are liable to trap the product being conveyed.

Description: This invention relates to a materials handling device and is particularly, though not exclusively, concerned with vibratory conveyors. Vibratory conveyors are used in many industries to move various (usually small) items from one location to another. Such conveyors usually comprise a trough mounted on a relatively massive base by means which permit the trough to be rhythmically pulsed, thereby to move items from one end of the trough to the other. It will be appreciated that these conveyors are especially suitable for transporting food products since the trough may be of simple form and is relatively easily and economically manufactured from stainless steel or aluminium. Such troughs are also easy to clean and provide minimal obstruction to the passage of items therealong. Vibratory conveyors are used in continuous food manufacturing processes, for example to transport frozen french fries to weighing and packing stations. Typically a series of three vibratory conveyors may be provided in line and having small gaps therebetween bridged by gates. The gates open under command to allow french fries to drop onto means for conveying the fries to one of several weighing stations. Only one weighing station is supplied at a time and the gates accordingly open and close rather frequently. Such apparatus may be in continuous use 6 days a week and for 24 hours each day, and must thus be entirely reliable since otherwise the entire preparation and packing line may come to a halt. A typical prior art conveyor is described in detail below. The gates of such vibratory conveyors undergo considerable stress due to the necessary vibration of the mechanism; they frequently suffer cracks and breakage. Many attempts have been made to mitigate these effects but none has been entirely successful. The prior art gates also suffer other disadvantages in that closing of a gate may trap the product between adjacent faces of the gate and conveyor, leading to misshaped or broken product and potential jamming of the gate mechanism. Prior art gates may also require stiffeners to ensure adequate strength and rigidity, but such stiffeners obstruct the free movement of product. A further disadvantage is that the gates rattle and thus the noise level in the immediate vicinity of the gate mechanism is extremely high mainly because the gate vibrates in its mounting and on the upstream conveyor bed. This is of considerable concern but to date no adequate method of noise reduction has been found which is reliable and effective. Yet another disadvantage is that as the gates pivot upward (whilst loaded with product) they tend to throw product over the side of the conveyor; this is undesirable and dangerous and makes the mechanism especially unsuitable for a food factory. Notwithstanding the very considerable disadvantage of vibratory conveyors with gates, these mechanisms have become the standard for use in many industries and particularly in the food industry. GB-A-1319669 describes such a vibratory conveyor. In that case, the gates open slidingly, but the problems associated with such conveyors as are identified above apply equally to the device of that document. DE-A-1263606 discloses a belt conveyor having several cascading belt sections. Adjacent belt sections are separable to define gaps through which material may be fed to collection chutes. The present invention provides a novel arrangement of vibrating conveyors which overcome the aforesaid problems. According to the invention here is provided a vibrating conveyor apparatus comprising two or more vibrating conveyors reciprocal relative to one another from a first condition, in which one conveyor is adapted to feed another, to a second condition in which the conveyors are spaced apart to define a gap in the conveying direction. In the second condition the one conveyor cannot feed the other, but instead product transported along said one conveyor falls through the gap. In a preferred embodiment, the conveyors are generally horizontal but spaced from one another in the vertical direction in the manner of a cascade such that the exit of an upstream conveyor is above the entrance of a downstream neighbour. In a preferred embodiment one conveyor is fixed against movement. Several movable conveyors may be provided in sequence, the conveyors being movable relative to each other to define gaps therebetween. One or more of the movable conveyors may be mounted on wheeled trucks and be movable under the control of mechanical or fluid actuators. The conveyors may be arranged in line and include troughs along which product is conveyed, the ends of adjacent troughs being formed to permit nesting of one trough within another with substantial clearance. Preferably such conveyors are arranged with each succeeding trough being lower than its predecessor, thereby permitting adjacent troughs to have substantially flat trough bases. The invention permits the conveyors to feed product either through the gap defined when adjacent conveyors are apart, or from one conveyor to the next. In one particular embodiment product is fed from a fixed conveyor to a series of two movable conveyors, thereby giving the possibility of creating conveyor gaps between the first and second, and between the second and third conveyors, and of feeding product from the end of the third conveyor. Any combination is however possible and there is no reason why a fixed conveyor should not be last in sequence or at an intermediate position. Furthermore, particular circumstances may require each conveyor in the sequence to be movable. Preferably the movable conveyors are guided on fixed rails and between stops. The invention provides vibrating conveyor apparatus which provides a plurality of feed gaps without the necessity of the prior art gates. No mechanical link between adjacent conveyors is necessary and the mechanical stress and noise is substantially reduced. In the preferred embodiment product passes from one conveyor to the next under the influence of gravity and thus undergoes minimal damage; most importantly, conveyors having troughs define a substantial clearance herebetween in the nested condition, thereby ensuring that no product can be squashed or otherwise damaged as is the case with the prior art gates. Gates do not become fouled by damaged or trapped product. Other aspects of the invention will be apparent from the following description of a preferred embodiment shown by way of example only in the accompanying drawings, in which: Figure 1 is a schematic side elevation of a prior art vibratory conveyor system with gates; Figure 2 is a plan of the system of Figure 1 showing also conveyors to the weighing stations; Figure 3 is a partially cut away isometric view of a prior art conveyor gate; Figure 4 is a schematic side elevation of an arrangement according to the present invention; Figure 5 is a plan of the arrangement of Figure 4; Figure 6 is an enlarged isometric view of two adjacent conveyors illustrated in Figure 4; and Figure 7 is an enlarged cross-section on line A-A of Figure 4. With reference to Figures 1 - 3, the drawings illustrate a prior art vibratory conveyor system with gates. A first conveyor 11 comprises a trough 12 mounted on a base 13 by a vibrating mechanism 14. Vibrating mechanisms are well known and will not be further described here, but are capable of vibrating small items from one end of the trough to the other (indicated by arrows). Spaced from the first conveyor 11 is a second conveyor 21 and a third conveyor 31 each comprising a trough 22, 32 and an individual vibrating mechanism 24, 34. The small gap between each conveyor may be closed by drop down gates 15, 25 as illustrated (gate 25 is not shown in Figure 2). The gates are pivoted above the respective troughs 12, 22 and move in the direction indicated by arrow 41 under the control of eg. individual pneumatic actuators. As shown in Figure 1 each successive trough is slightly lower than its predecessor to allow the gate to pass under the end lip of the upstream conveyor and to rest above the end lip of the downstream conveyor. Although not illustrated in Figure 1, the gates have sides to prevent loss of product. Below each gate and below the lip of trough 32 are vibratory conveyors 16, 26, 36 for conveying product to individual weighing stations (not illustrated). As shown in Figure 1, gate 15 is closed and gate 25 open, thus allowing product to fall from the end of trough 22 onto conveyor 26. Operation of the gate 15, 25 and vibrating mechanisms 14, 24, 34 is typically under the control of apparatus which detects that an adequate amount of product is being supplied to each weighing station that is in operation. Such apparatus may include photocell detectors or the like to detect the presence or absence of product at the upstream end of conveyors 11, 21, 31, 16, 26 and 36 and under the control of a logic circuit. The vibrating mechanisms 14, 24, 34 and gates may thus be operated individually or in combination to ensure that product is supplied as required. The gates 15, 25 have no vibrating mechanism of their own but by virtue of being mounted on the upstream trough the continuous movement of product is assured. Figure 3 illustrates a typical prior art gate 51 located in the down position between an upstream trough 52 and a downstream trough 53. The gate has sides 54 extending upwards to a transverse beam 55 pivoted for rotation by any suitable means on the upstream trough 52 and for arcuate movement as illustrated by arrow 56. The gates include a central stiffener 57 of the same general form as each of the sides 54. A rearward extension 58 of the trough base 59 extends just under the end lip of the upstream trough 52; the extension both ensures continuity of the conveying surface and acts on a stop for the gate. At the downstream end the gate rests above the downstream trough as illustrated. The sides 54 are made sufficiently high to ensure product is kept within the conveying path. The disadvantages of the pivoting gate arrangement are that: 1. Product is trapped under between the extension 58 and upstream trough 52, and between the base 59 and the downstream trough 53; 2. Product builds up against the upstream edge of the stiffener 57; this is especially acute where product having a long length/thickness ratio is being conveyed (eg. french fries); and 3. The gate is subjected to vibrating from both the upstream and downstream troughs, which vibration may be of different frequencies; this results in excessive noise and a high rate of material failure due to stress cracks. Hitherto gates have typically been manufactured from aluminium to minimise the incidence of stress cracking. New food plant is however often required to be manufactured from stainless steel which, being a much harder material, is very prone to stress cracking and much more difficult to repair. The invention will now be described with reference to Figures 4 - 7. A series of three vibrating conveyors 61, 71, 81 are arranged in line as illustrated. Each conveyor has a respective trough 62, 72, 82, base 63, 73, 83 and vibrating mechanism 64, 74, 84. The base 63 of the upstream conveyor 61 is fixed whereas the middle and downstream conveyors 71, 81 are mounted on trucks 75, 85 as shown, each truck having four wheels and being mounted on parallel rails for fore and aft movement. A respective mechanical actuator 76, 86 is operable to move each truck 75, 85 a limited distance along the rails 91 (rails 91 are omitted from Figure 5). End stops 92 limit and cushion truck travel. Vibratory conveyors 67, 77, 87 are provided, as in the prior art embodiment, to feed product to weighing stations. As best illustrated in Figure 5, the sides of the inlet ends of the downstream and middle troughs 62, 72 are bent outwardly so that one trough can rest within the following trough. Each succeeding trough is also slightly lower than its predecessor to maintain the trough base flat whilst permitting nesting. Figure 6 is an enlarged somewhat schematic view of two nested troughs 62, 72 whilst Figure 7 illustrates the substantial clearance "d" between the walls of the upstream trough 62 and the downstream trough 72. In operation, and with reference to Figures 4 and 5, the trucks 75, 85 are moved back and forth by the actuators 76, 86 under the command of a control mechanism similar to that provided for the prior art embodiment. As illustrated, product passes from conveyors 61 and 71 and hence drops onto conveyor 77. Actuator 76 is retracted and the vibrating mechanisms 64 and 74 operate independently to shake product in the conveying direction. The clearance between troughs 62, 72 is substantial, as illustrated in Figure 7, and this feature ensures that no product becomes trapped between the nested sections of troughs 62, 72; thus no product can be squashed or otherwise damaged. The clearance "d" is set according to the size and kind of product being conveyed. As illustrated, when feeding conveyor 77 the vibrating mechanism of trough 82 may be switched off. Clearly the conveyors 67, 77, 87 may be fed in any desired sequence by appropriate positioning of the trucks 75, 85. The arrangement has the undisputed advantages that: 1. There are no contact faces to squash or damage product. 2. The conveying paths are unobstructed. 3. There is no mechanical connection or abutment between adjacent troughs - this ensure less mechanical stress, and most importantly, less noise. 4. No gates are required, and thus there is no risk of product being thrown from the conveying path. 5. The clearances between the nested trough portions are not critical so long as they are large enough to ensure that no product can be trapped or jammed. Many changes may be made to the above described embodiment of the invention to suit the particular circumstances of each installation without departing from the invention disclosed herein, whose scope is defined by the following claims.

Claims: Vibrating conveyor apparatus comprising two or more vibrating conveyors (61,71,81), the exit end of a first conveyor (61,71) being spaced from the entrance end of a second adjacent conveyor (71,81) in the vertical direction in the manner of a cascade, characterised in that said conveyors are reciprocal relative to one another from a first condition, in which one conveyor (61,71) is adapted to feed another (71,81), to a second condition in which the conveyors (61,71,81) are spaced apart to define a gap in the conveyor direction, each conveyor (61,71,81) including a product conveying trough (62,72,82), each upstream trough (62,72) nesting within its downstream neighbour (72,82) in the first condition and being spaced from its downstream neighbour by a clearance large enough to ensure that no product being conveyed can be trapped or jammed. Apparatus according to Claim 1, wherein the conveyors (61,71,81) have the same conveying direction. Apparatus according to claim 1 or claim 2, wherein one conveyor (61) is substantially fixed against reciprocal movement. Apparatus according to any preceding claim, wherein the or each reciprocal conveyor (71,81) is mounted on wheels. Apparatus according to Claim 4, wherein said wheels are guided by tracks (91). Apparatus according to any preceding claim, wherein the or each reciprocal conveyor (71,81) is movable between fixed stops (92). Apparatus according to any preceding claim, wherein each downstream trough (72,82) is of substantially constant section, but widened at its entrance portion to accommodate the exit portion of an upstream neighbour (62,72).

Inventors: FLINTON BRIAN THOMAS, FLINTON, BRIAN THOMAS
Applicants: MCCAIN FOODS GB LTD, MCCAIN FOODS(GB) LIMITED
Application year: 1993
Main classification: B65G27
IPC codes: B65G27, B65G47