GB2208838A - Conveyor skirt seal - Google Patents

Abstract

A skirt board assembly for providing a seal around a chute or hopper of a troughed belt conveyor is formed by a structural backing plate (13) and a plurality of rubber skirt board sections (14) with interfitting guide formations (19, 20) enabling the skirt board sections to be lowered to contact the belt. The skirt boards (14) are slotted at (21) and individually bolted at a predetermined torque by bolt and nut assembly (17, 18) to the backing plate (10) so as to have firm frictional grip to resist displacement. As wear takes place, the skirt boards (14) can be tapped down using a hammer without releasing the nuts (18) until the travel allowed by the slot (21) has been used. Replacement skirt boards can be positioned by face fixing by removal of the bolt and nut assemblies. A dished auxiliary clamping plate (22) may be provided to spread the clamping pressure. <IMAGE>

Description

TITLE: Conveyor Skirt Seal This invention relates to conveyor skirt seals.

Conveyors carrying loads of bulk material such as coal, rock or ore are usually of the troughed belt type in which an endless belt rides in trough shaped supports, usually including stands of freely rotatable rollers.

Where loads are deposited on the conveyor belt, or where one run of conveyor feeds onto another, the feed hopper or chute should desirably be provided with a skirt to form a dynamic seal with the moving belt. The skirt is needed to reduce dust and spillage.

The skirt edges are subjected to abrasion by the moving belt and also by the bulk load. This abrasion reduces the efficiency of the seal and allows dust to escape.

In early proposals, adjustment of the skirt required shut down of the conveyor, unbolting of the skirt and its subsequent reattachment at an adjusted position.

There has also been a proposal, in British patent number 2,014,530, to make the skirt in inter-engaging short lengths, or "skirt boards" which are individually adjustable for vertical height. The skirt boards are mounted on attachment plates which have key ways interengageable with corresponding key ways formed in the skirt blocks. Barbed formations on the plate key ways resist upward movement of the skirt boards but permit the individual sections to be tapped down vertically with a hammer to form a good seal with the belt.

However, this skirt board system has certain drawbacks and it is an object of the present invention to overcome or reduce these drawbacks.

Firstly, the skirt blocks are physically keyed to the backing plates and can only be attached by downward sliding movement. Where there is inadequate headroom, this is not possible.

Secondly, the skirt boards, which are generally of hard rubber, are subjected to high lateral thrust where a conveyor belt carrying a heavy load tends to wander from its centered position. In this case, it is possible for the skirt boards to be stripped off the backing plates, leaving an opening through which dust and load materials can escape. This problem is aggravated where the skirt boards have interfitting edges because this may result in a number of skirt boards simultaneously being peeled off the backing plates, leaving a large opening.

Finally, the amount of friction obtainable to resist upward movement of the skirt board sections is predetermined by the friction formations provided on the guideway of the backing plate and cannot be adjusted except by substitution of new backing plates.

According to the present invention there is provided a conveyor skirt board assembly comprising a rigid backing plate including a plurality of generally parallel guides perpendicular to the plate; a plurality of skirt boards each including guide means adapted to engage one or more corresponding guides of the backing plate, each skirt board having a through slot disposed parallel to the guide means; and clamping means adapted to clamp the skirt boards to the backing plate and to provide a predetermined frictional engagement such as normally to prevent skirt board movement but to permit movement of the skirt boards in the direction of the guides and guide means when hammer blows are applied to the skirt boards.

Preferably, the clamping means includes a bolt and nut assembly adapted to be tightened to a predetermined torque.

The assembly may include an auxiliary clamping plate abutting each skirt board at the face thereof remote from the backing plate.

The auxiliary clamping plate may be dished.

Friction increasing means may be provided on the backing plate and/or on the abutting face of the skirt boards.

A skirt board assembly embodying the invention will now be described in more detail by way of example only with reference to the accompanying drawings in which: FIGURE 1 is a plan sectional view of the assembly.

FIGURE 2 is a front elevational view of the assembly.

FIGURE 3 is an end elevational view of the assembly.

FIGURE 4 is a general arrangement of the skirt board assembly in use on a feed station of a conveyor.

FIGURE 5 is a front view of a back plate.

FIGURE 6 is a detail section on the line 6:6 of Figure 5.

FIGURE 7 is a detail plan view of a modified connection.

Referring firstly to Figure 4 of the drawings, a feed chute 10 of a troughed belt conveyor 11 is provided with skirts 12 consisting of a backing plate 13 and a plurality of skirt plates 14 to be described in more detail with reference to the remaining drawings. The direction of the conveyor is indicated by the arrow A in Figure 4 and it will be seen that bulk material 15 dropping onto the conveyor is prevented from escaping from the back and sides of the feed chute 10 by the skirt 12. The latter conforms to the shape of the belt. In particular, at the rear of the chute 10, the lower edges of the skirt boards 14A are shaped to conform to the troughed profile of the conveyor belt 16.

Turning now to Figures 1 to 3 of the drawings, each skirt board 14 is made of tough rubber or plastics of a hardness slightly less than the hardness of the conveyor belt 16 so that the skirt board will be worn away in preference to the belt during normal running of the conveyor. The lower part of the board may be made of a material having a lower Shore hardness than that of the upper part if desired. Each skirt board 14 is mounted on the backing plate 13 by means of a clamping bolt 17 and a lock nut 18. The bolts 17 may be free standing or may be provided as fixed studs welded to the backing plate 13.

Each skirt board is provided with a pair of vertical grooves 19 which receive corresponding projecting parallel fins 20 provided on the backing plate. The fins 20 running in the grooves 19 form guide means for movement of the skirt board to accommodate any wear at the skirt edge. A vertical through slot 21 is provided in the skirt board to permit the bolt 17 to pass through. When the lock nut 18 has been tightened, the skirt board is therefore held captive to the backing plate 13. However the vertical position of the skirt plate can be varied since the fins 20 and grooves 19 only constrain the skirt plate against lateral movement and since the bolt can pass through the slot 21 at any position along its length.

In order to spread the clamping pressure of the bolt and nut assembly over the area of the skirt plate, an auxiliary clamping plate 22 is provided which may be dished as shown at 23 to exert a resilient pressure on the skirt board 14. In addition to spreading the clamping pressure, the auxiliary clamping plate 22 prevents the bolt and nut assembly from indenting into the material of the skirt board which might prevent proper adjustability of the skirt board sections.

In order to install the skirt assembly, the backing plate 13 is firstly installed by bolting or welding to a convenient fixed part of the feed chute or hopper. The skirt boards 14 are then attached to the backing plate 13 either by vertical sliding movement between the fins 20 and grooves 19 or by face fixing. Referring to Figure 6, it will be noted that the fins 20 are parallel and not undercut or dove tailed, which permits face fixing. Face fixing may be essential where there is insufficient headroom for vertical downward sliding movement of the skirt boards to take place or where the clamping bolt 17 is provided as a stud, welded onto the backing plate 13.

To complete assembly, the skirt board sections are clamped by means of the bolt and nut assembly, using the auxiliary clamping plate where provided, and the nut is tightened to a predetermined torque so as to exert a known clamping pressure on the rubber skirt board.

The assembly is then adjusted so that the lower edge 24 of the skirt board makes brushing contact with the surface of the conveyor belt 16.

The side edges of the skirt blocks 14 are rebated at 25 so as to form a good seal. It will be seen that it is still possible to attach the skirt boards by face fixing since the protruding tongue 26 of one board can be slipped behind the corresponding outer tongue 27 of the adjacent board to permit face fixing.

In the modified form shown in Figure 7 of the drawings, the skirt blocks have interlocking tongue and groove formations. However it is still possible to make a face fixing by using the slight flexibility of the skirt board material. Where one or two skirt board sections are to be replaced, the adjoining skirt board sections are loosened and pulled slightly away from the backing plates. The interlocking tongues and grooves 30, 31 are then assembled together and the skirt boards pushed back into place. Tightening of the nuts is all that is required to complete the assembly.

The backing plate 13 is preferably provided, as shown in Figure 5, with a scored or deckled front face 28 against which the rear surface of the skirt board abuts.

Alternatively or in addition, the rear face of the skirt board can be provided with friction formations, with the objective of increasing the frictional resistance of the skirt board to movement.

In use, the skirt boards are positively clamped against the forward face of the backing plate 13. They are therefore not readily torn off by side loads on the skirt boards due to wandering of the heavily loaded conveyor belt.

When the lower edge 24 of the skirt board becomes worn at any point, it is unnecessary to adjust the clamping pressure of the bolt and nut assembly 17, 18. All that is required is to tap the skirt board 14 downwardly with a hammer, overcoming the predetermined frictional force between the deckled backing plate 13 and the rubber skirt board 14. The skirt board section moves downwardly in a direction constrained by the inter-engagement of the fins 20 and slots 19 and the bolt runs in the vertical through slot 21 which is parallel to the fins and grooves.

The bolt and nut assembly only needs to be adjusted when a complete replacement of the skirt board is required, when the maximum travel permitted by the slot 21 has been taken up. However, the backing plate 13 can be left in place at this time and replacement need only be made of those skirt boards which have been heavily worn.

Where permitted by safety regulations, work can be carried out to adjust the skirt boards while the conveyor is in moticn.

Claims (7)

1. A conveyor skirt board assembly comprising a rigid backing plate including a plurality of generally parallel guides perpendicular to the plate; a plurality of skirt boards each including guide means adapted to engage one or more corresponding guides of the backing plate, each skirt board having a through slot disposed parallel to the guide means; and clamping means adapted to clamp the skirt boards to the backing plate and to provide a predetermined frictional engagement such as normally to prevent skirt board movement but to permit movement of the skirt boards in the direction of the guides and guide means when hammer blows are applied to the skirt boards.

2. A conveyor skirt board assembly according to Claim 1 wherein the clamping means includes a bolt and nut assembly adapted to be tightened to a pre-determined torque.

3. A conveyor skirt board assembly according to any preceding claim and including an auxiliary clamping plate abutting each skirt board at the face thereof remote from the backing plate.

4. A conveyor skirt board assembly according to Claim 3 wherein the auxiliary clamping plate is dished.

5. A conveyor skirt board assembly according to any preceding claim wherein friction increasing means are provided on the backing plate.

6. A conveyor skirt board assembly according to any preceding claim wherein friction increasing means are provided on the face of the skirt board which abuts the backing plate.

7. A conveyor skirt board assembly substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.