GB2252526A - Press heads and press forming methods - Google Patents

Abstract

A press head 10 for forming, and extracting liquid from, a liquid or semi-liquid substance in a mould includes a carrier assembly 12, a plate assembly 14 and a quick release arrangement 16 for replaceably securing the plate assembly 14 to the carrier assembly 12. An improved method of forming articles, e.g. from a concrete mix, is disclosed which employs a press head 10 with a replaceable perforated plate assembly 14 with a permeable filter cloth 29 bonded to it. <IMAGE>

Description

PRESS HEADS AND PRESS FORMING METHODS This invention relates to press heads and in particular, but not exclusively, to press heads for a press for forming articles from a concrete mix. The invention also extends to methods for forming articles from a concrete mix or slurry by pressing.

Concrete articles such as paving stones, kerb stones etc. are commonly made by pouring a concrete mix or slurry into a mould and then applying pressure on the exposed surface of the mix or slurry via a perforated pressure plate and a paper filter to express the surplus water. The typical water content is 20% of the volume of the mix or slurry.

There are two problems associated with the existing method and press. Firstly, the perforated plate is secured to the press head by several peripheral bolts and so, when the plate fails or needs to be changed the press is out of service for an hour or so with the loss of production of several hundred articles. Secondly, the use of paper filters as an interface between the surface of the mix or slurry and the perforated plate means both that each paper must be individually inserted, thus taking time and that a large stock of papers must be provided which takes up floor space adjacent the press and must be regularly replenished.

It has been proposed to secure a cloth to the underside of the perforated plate to obviate the need for paper filters. The typical life of a plate with such a cloth will be less than the conventional plate and so this improvement only becomes feasible if the downtime required for changing the plate can be significantly reduced.

A need exists therefore for a press head having a pressing surface which can be replaced quickly and easily to reduce the downtime.

Accordingly, in one aspect, this invention provides a press head for a press for forming articles said press head including a carrier portion, a plate means releasably carried by said carrier portion, clamp means operable for releasably securing said plate means to said carrier portion, and actuator means for operating said clamp means.

In a preferred arrangement the press head is adapted for forming articles from a liquid or semi-liquid substance such as a concrete mix or other slurry.

The clamp means preferably includes complementary engagement means provided on said carrier portion and said plate means. For example, the plate means may carry a latch block which is engageable by latch means provided on the carrier portion. Preferably, the latch means is biassed and the latch block includes a camming surface so that the plate may be releasably retained on said carrier portion by urging the plate means towards the carrier portion to cause the latch block to be engaged and clamped by the latch means.

The latch means may comprise two latch members mounted for movement relative to the carrier portion and acted on by a respective actuator, for example a fluid-operated ram.

Preferably, the press head includes biassed release means arranged to urge the plate means away from the carrier portion when said clamp means is released.

The plate means may be a perforated plate and the perforated plate preferably carries filter means. The filter means preferably comprises a woven or non-woven cloth or cloth-like permeable layer secured adjacent the perforated plate.

In another aspect, this invention provides a method of forming an article from a liquid or semi-liquid substance which comprises providing a mould, introducing said substance into said mould, and pressing said substance with a press head to express liquid therefrom, said press head including a carrier portion, a plate means releasably carried by said carrier portion, clamp means operable for releasably securing said plate means to said carrier portion, and actuator means for operating said clamp means.

Whilst the invention has been described above it extends to any inventive combination of features set out above or in the following description.

The invention may be performed in various ways and two embodiments of the invention will now be described by way of example only, reference being made to the accompanying drawings, in which: Figure 1 is a transverse section view on a part of a press head in accordance with a first embodiment of the invention showing one of two spaced clamping stations which clamp a plate assembly to a carrier head; Figure 2 is a longitudinal section view on that part of the press head illustrated in Figure 1 and taken on arrows II II; Figure 3 is a longitudinal section view on a press head in accordance with a second embodiment of the invention, and Figure 4 is a transverse section view on the press head illustrated in Figure 3, taken on arrows IV IV.

Referring to Figure 1, the first embodiment of press head is of similar overall shape and function as the second embodiment shown in Figures 3 and 4, to which reference should be made. The press head 10 of Figures 1 and 2 includes a carrier assembly 12, a perforated plate assembly 14 and a pair of spaced quick release clamp arrangements 16 (only one of which is shown) provided at either end of the press head for releasably securing the plate assembly 14 to the carrier assembly 12.

The carrier assembly 12 comprises a die block 18 fastened to a die carrier 8. Referring to Figure 2, the lower surface of the die block 18 carries an inner die plate 22 and outer die plates 24 (only one of which is shown) spaced from either end of the inner die plate 22 to define spaced channels into which fit spaced loose die plates 26 (only one of which is shown) secured to the upper side of the perforated plate 28 of the assembly 14. Referring to Figure 2, each quick release clamp arrangement 16 is situated above the channel and comprises two latches 30 slidably housed in the die block 18 and urged towards each other by two springs 32. A diaphragm cylinder actuator 34 is associated with each latch for urging it against the spring 32 to withdraw it.

The perforated plate assembly 14 comprises the perforated plate 28 carrying the loose die plates 26, as described above. Each die plate 26 carries on its upper surface a latch block 36 for being engaged by the latches 30. The lower side of the perforated plate has secured or bonded to it a filter cloth 29. Alternatively, the perforated plate may be used with the conventional type of paper filter.

Next to each set of latches there is provided a springbiassed plunger 38 for assisting release of a perforated plate assembly 28.

In use, to change the plate assembly, the existing plate assembly 14 is supported and the cylinder actuators 34 are operated to withdraw the latches 30 to allow the perforated plate assembly 28 to be released by raising the die block 18. A new plate assembly 14 may be fitted by opening the latches 30 and lowering the die block 18 onto the new plate assembly and then closing the latches.

In the above example, it will be seen that the release mechanism comprising the clamp arrangements 16 does not encroach on the die carrier 8.

Referring now to Figures 3 and 4, there is shown an alternative example of press head with another type of quick release mechanism for the plate assembly. In this example, the press head 110 includes a carrier assembly 112, a perforated plate assembly 114 and a pair of spaced quick release clamp arrangements 116 provided at either end of the press head for releasably securing the plate assembly 114 to the carrier assembly 112.

The carrier assembly 112 comprises a die block 118 fastened to a die carrier 120 and the lower surface of the die block 118 carries an inner die plate 122 and outer die plates 124 spaced from either end of the inner die plate 122 to define spaced channels into which fit spaced loose die plates 126 secured to the upper side of the perforated plate 128 of the assembly 114. Referring to Figure 2, the quick release clamp arrangements 116 are situated above the channels and comprise two generally C-shaped latches 130 pivoted on spindles 132 which are secured in the die block 118. Each two latches 130 are urged towards each other by a tension spring 134 acting between them. Each two latches 130 may be unlatched by a piston rod 135 of a common ram 136.

The upper end of the piston rod carries a plate 138 positioned beneath a diaphragm 140. The diaphragm is clamped around its edge and closes a pressure chamber 142 fed by an inlet passage 144. Each latch has a camming surface 146 on its lower surface to allow opening, as to be described below. Next to each set of latches there is provided a spring-biassed plunger 147 for assisting release of a perforated plate assembly 114.

The perforated plate assembly 114 comprises the perforated plate 128 carrying the loose die plates 126, as described above. Each die plate carries on its upper surface a latch block 148 for being engaged by the latches 130. The lower side of the perforated plate has secured or bonded to it a filter cloth 149.

In use, the current perforated plate assembly 114 is released by admitting working fluid, e.g. air, into the pressure chambers 142 to cause the diaphragms 140 to bow downwardly and to urge the rams 136 downwardly to pivot the latches 130 so their teeth 150 move apart to release the latch blocks 148. The plate assembly is then urged or ejected downwardly by the spring-biassed plungers 147.

The supply to the chambers 142 is turned off and vented. The carrier assembly is lowered onto the replacement perforated plate assembly so that the latch blocks 148 contact the camming surfaces 146 on the latches 130 and urge them apart to snap over and latch the latch blocks 148 in place. The press head is now ready for service.

In this second example the quick release clamp arrangements encroach into the die carrier 120.

Claims (14)

1. A press head for a press for forming articles, said press head including a carrier portion, a plate means releasably carried by said carrier portion, clamp means operable for releasably securing said plate means to said carrier portion, and actuator means for operating said clamp means.

2. A press head according to Claim 1, wherein said press head is adapted for forming articles from a liquid or semi-liquid substance.

3. A press head according to Claim 2, wherein said substance comprises a concrete mix or other slurry.

4. A press head according to any preceding claim, wherein said clamp means comprises interengageable engagement means provided on said carrier portion and said plate means.

5. A press head according to Claim 4, wherein said clamp means comprises a latch block provided on said plate means and which is engageable by latch means provided on the carrier portion.

6. A press head according to Claim 5, wherein the latch means is biassed and the latch block includes a camming surface so that the plate may be releasably retained on said carrier portion by urging the plate means towards the carrier portion to cause the latch block to be engaged and clamped by the latch means.

7. A press head according to Claim 5 or 6, wherein the latch means comprises two latch members mounted for movement relative to the carrier portion and acted on by a respective actuator.

8. A press head according to Claim 7, wherein said actuators comprise fluid-operated rams.

9. A press head according to any preceding Claim, wherein the press head includes biassed release means arranged to urge the plate means away from the carrier portion when said clamp means is released.

10. A press head according to any preceding Claim, wherein the plate means is a perforated plate which carries filter means.

11. A press head according to Claim 10, wherein said filter means comprises a woven or non-woven cloth or clothlike permeable layer secured adjacent the perforated plate.

12. A method of forming an article from a liquid or semi-liquid substance which comprises providing a mould, introducing said substance into said mould, and pressing said substance with a press head to express liquid therefrom, said press head including a carrier portion, a plate means releasably carried by said carrier portion, clamp means operable for releasably securing said plate means to said carrier portion, and actuator means for operating said clamp means.

13. A press head substantially as hereinbefore described with reference to, and as illustrated in, any of the accompanying drawings.

14. A method of forming an article, substantially as hereinbefore described with reference to any of the accompanying drawings.