GB2194195A - Apparatus and method for casting elongate concrete articles - Google Patents

Abstract

The method involves casting liquid concrete into an open-topped elongate mould. When the concrete has set the mould is opened at its narrow ends and the cast article is ejected lengthwise through one of the ends by means of a pusher acting through the other end. Apparatus for making the articles includes a plurality of such moulds and holding means for holding a mould stationary with its narrow ends open. Pusher means is arranged to act on the cast concrete article in said mould through one of the ends so as to eject it lengthwise through the other of said ends. Receiving means is provided for receiving the cast article so ejected. A mould comprises a floor and side walls (2, 3) and end walls (5) movable into out-of-way positions enabling ejection of the article. An ejector station (19), which has grippers (20, 21) which clamp a mould against an upstanding wall (22), is aligned to one side of a hydraulic ram (24) provided with a pusher plate (26) and cleaning brush (27). The preferred application is to making slotted fence posts. <IMAGE>

Description

SPECIFICATION Improvements in or relating to the casting of elongate concrete articles This invention is concerned with improvements in or relating to the casting of elongate concrete articles and, more specifically, with a method of and apparatus for making such an article as well as a mould for casting the article.

The invention is primarily although not exclusively concerned with elongate concrete articles of the kind generally referred to as "slotted fence posts having a square or rectangular profile with lengthwise channels at two opposite sides for locating fencing elements when the post is vertically positioned in appropriate spaced relationship with similar posts to each side thereof. In the absence of such channels the casting operation would be a simple procedure. The casting mould could be an open-topped elongate box shape with fixed side and end walls providing a slight taper facilitating release of the article when the mould is inverted for that purpose.Because of the channel formations, the moulds for casting slotted fence posts have hitherto required openable side and end walls or, alternatively, elongate core pieces which are fixed to the elongate side walls of the mould during the casting process so as to form the channels and are then released for ejection with the cast article through the open top of the mould. In either case, the mould required is expensive and the casting process requires considerable manual input (for example in opening and re-assembling the moulds) which renders it unsuitable to economical mechanization.

It is an object of the present invention to obviate or mitigate the aforesaid disadvantages.

According to a first aspect of the present invention, there is provided a method of making an elongate concrete article, comprising the steps of casting liquid concrete into an open-topped mould of elongate shape corresponding to the article, allowing the concrete to set, opening the mould at its opposite narrow ends and ejecting the cast article lengthwise through one of said ends by means of a pusher acting through the other of said ends.

According to a second aspect of the present invention, there is provided apparatus for making an elongate concrete article, comprising a plurality of open-topped moulds of elongate shape corresponding to the article and each having its opposite narrow ends adapted to open, an ejection station including holding means for holding the mould stationary with said narrow ends open, pusher means arranged to act on the cast concrete article through one of said ends so as to eject it lengthwise through the other of said ends, and receiving means for receiving the cast article so ejected.

According to a third aspect of the present invention, there is provided a mould for casting an elongate concrete article, comprising an open-topped box shape corresponding to that of the article with a floor, fixed longitudinal side walls and narrow end walls movable into out-of-the-way positions enabling ejection of the cast article lengthwise through one of said ends by pusher means acting through the other of said ends.

In each case the elongate concrete article is preferably, although not necessarily, a slotted fence post of the kind described above.

The invention will now be further described by way of example only, with reference to the accompanying drawings, in which: Figs. 1 and 2 are respectively a side elevation and plan view of part of one embodiment of apparatus for making an elongate concrete article in accordance with the invention; Fig. 3 is another part of the same apparatus in plan view; and Fig. 4 shows various views of one end of an embodiment of casting mould in accordance with the invention.

The illustrated apparatus and mould are designed for the purpose of manufacturing slotted fence posts of the kind described above. It will be appreciated that such fence posts may vary slightly in design to suit customer demand and local casting practice.

Thus, for example, the dimensions of the square or rectangular cross-sectional profile may vary slightly between different geographical regions; also, the ends of the posts may be of differing shapes, e.g. round or pyramid.

These slight variations must of course be taken into account in the design of the mould and the inserts which determine the shape of the ends of the posts.

Referring now to Fig. 4, It will be seen that the casting mould of the invention comprises an elongate box shape (only partly shown in the drawing) with a floor 1 integral with longitudinai side walls 2, 3, an open top 4 and narrow end walls 5 (only one of which is shown in the drawing). The side walls 2, 3 terminate in out-turned flanges 6, 7 and have channel formations 8, 9 in the outer surfaces thereof so as to form corresponding confronting projections on their inner surfaces for the purpose of casting the side channels in the fence posts. Each end wall 5 is hinged at one side to the side wall 2 by a conventional hinge arrangement as illustrated. At the opposite side is a conventional anti-loose pin 10 comprising a bar 11 welded to the mould side wall 3 so as to project outwardly through a hole in the end wall 5 when the latter is closed.The bar 11 has a forked end with a cross pin 12 passing through a slot of a tapered wedge element 13. When the end wall 5 is being opened or closed the wedge ele ment 13 is in line with the bar 11 so as to pass through the hole in the wall 5. When the wall- 5 is closed the wedge element 13 is moved into the illustrated position transverse the bar 11 and then lengthwise to produce a wedging effect which forces the end wall 5 into its fully closed position, the wedge ele -ment tending to remain in this position by virtue of a serrated edge of its slot.

A plurality of such moulds is provided and filled successively with concrete cast through a hopper 14 above a roller track 15 along which the moulds are moved lengthwise one after the other. A vibrating unit (not shown) is provided as part of the conveyor track 15 in order to vibrate the mould as it is filled with concrete thereby ensuring uniformity of the cast concrete in the finished product. The filled moulds are then conveyed lengthwise from the filling station under the hopper 14 to a transfer station where a pusher 16 acts si deways on the mould to transfer it to a hold ing station 17 which may simply be parallel roller tracks for supporting a succession of moulds in parallel relationship one behind the other.

When the concrete has set, the moulds are transferred, e.g. by fork-lift truck to a holding station 18 similar to the holding station 1 7 but with the roller tracks inclined downwardly to provide a gravity feed of the moulds to an ejection station 19. The ejection station 19 has grippers 20, 21 which can be extended underneath the leading mould and into the gap between it and the adjacent mould (created by the abutment of adjacent mould flanges 6, 7) whereupon the gripper draws the leading mould past a stop at the front of the -con veyor 18 and onto the ejection station 19 clamping it firmly against an upstanding wall 22 forming an integral part of the ejection station 19. By this stage, the end walls 5 have been opened and the mould is therefore positioned at the ejection station 19 with the opposite ends of the casting article exposed.

As seen in Figs. 1 and 2, the ejection sta tion 19 is aligned to one side with a ram which may be a fluid pressure operated (preferably hydraulic) double-acting ram. A con ventional double-acting hydraulic ram powered by a hydraulic unit with an 8 horse-power motor has proved acceptable in practice. The ram 24 has a stroke of length such that the head 25 of the ram can reciprocate over the entire length of the ejection station 19. The ram 24 constitutes the pusher means of the invention in this embodiment and its head 25 is provided with a pusher plate 26 which is shaped to conform to the shape of the end of the cast post, being slightly smaller than the cross-sectionai profile of the mould in order to ensure easy passage therethrough.The pusher plate 26 may be exchangeably mounted so that it can be replaced by other pusher plates suitable for different mould cross-sections and/or end shapes of the posts. Immediately behind the pusher plate 26 at the ram head 25 is a brush 27 which is slightly oversize with respect to the mould cross-section so that it performs a cleaning action as the ram head 25 passes lenghtwise through the mould.

It will be evident that with the open-ended mould held firmly at the ejection station 19 by the grippers 20, 21, the ram 24 may be operated to bring the pusher plate 26 into contact with the adjacent exposed and of the cast article. The force of the ram 24 serves to eject the article through the opposite end of the mould, the head 25 including the pusher plate 26 and the brush 27 travelling into one end of the mould, fully through the whole length of the mould and out of the opposite end of the mould thereby fully ejecting the article from its mould and at the same time cleaning the mould in preparation for the next casting operation. The force required to eject the cast article from the mould is considerably reduced if known chemical release agents are utilized.

The ejected article is conveyed along the roller track 28 to a transfer station 29 where a pusher 30 transfers the article to another holding station 31. The empty mould is removed from the ejection station 19 by an operator who places it under the hopper 14 in readiness for refilling. The cycle of operations is then repeated.

The sequence of operations is controlled by solenoid operated limit switches and interlocks. Thus the ram can only be extended when a mould is held by the grippers at the ejection station and operation of the sideways pushers 16, 30 takes place automatically when the mould/cast article is in the correct position for transfer. Such control systems are well known and require no further-explanation.

It will be appreciated that the mould design used in the present invention has significant advantages over the drop-sided moulds used in the prior casting techniques described above. Thus, the body of the mould is of integral construction with the floor 1 and the longitudinal side walls 2, 3 with their flanges 6, 7 being formed by a folding operation from a single piece of rolled steel. The mould is therefore cheap to make as well as being more durable and better able to produce a standard shape of fence posts.

It will be further appreciated that numerous modifications may be made without departing from the scope of the invention. For example, the end walls 5 of the mould may be hinged to the floor rather than to a side wall and the method of fixing the end wall in its closed position may also be modified in any desirable way, for example to facilitate automatic opening of the moulds during movement to the ejection station.

Claims (4)

1. A method of making an elongate concrete article, comprising the steps of casting liquid concrete into an open-topped mould of elongate shape corresponding to the article, allowing the concrete to set, opening the mould at its opposite narrow ends and ejecting the cast article lengthwise through one of said ends by means of a pusher acting through the other of said ends.

2. Apparatus for making an elongate concrete article, comprising a plurality of opentopped moulds of elongate shape corresponding to the article and each having its opposite narrow ends adapted to open, an ejection station including holding means for holding the mould stationary with said narrow ends open, pusher means arranged to act on the cast concrete article through one of said ends so as to eject it lengthwise through the other of said ends, and receiving means for receiving the cast article so ejected.

3. A mould for casting an elongate concrete article, comprising an open-topped box shape corresponding to that of the article with a floor, fixed longitudinal side walls and narrow end walls movable into out-of-the-way positions enabling ejection of the cast article lengthwise through one of said ends by pusher means acting through the other of said ends.

4. A method, apparatus or mould as claimed in claims 1, 2 or 3 respectively, wherein the elongate concrete article is a slotted fence post of the kind herein described.