GB2146309A

GB2146309A - Moulding machine and a metering device

Info

Publication number: GB2146309A
Application number: GB08323903A
Authority: GB
Inventors: John Mark Siddeley
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-09-07
Filing date: 1983-09-07
Publication date: 1985-04-17
Also published as: GB8323903D0

Abstract

A moulding machine for polymer concrete articles has a metering device. The metering device has three perforated plates (3, 4 and 5) of which the central one is displaceable so the perforations in the plates 3 and 4 are aligned and those in plates 4 and 5 not or vice versa. The depth of the plate 4 multiplied by the area of the perforations gives the desired volume of polymer concrete mix for the article to be moulded. The mix is delivered by a gravity or pressure feed to the metering device and then is allowed to drop into a mould 12 which is vibrated to cause the drops of the mix to coalesce and form a flat upper surface. <IMAGE>

Description

SPECIFICATION Moulding machine and a metering device The present invention concerns moulding machines and particularly a metering device suitable for use in such a machine.

The problems with which the present invention is particularly concerned arise in the casting of polymer concrete which is a highly viscous, abrasive, and sticky substance in its unset state but sets into a strong state. To add to the problems, polymer concrete sets rapidly. It is impossible to use technology based on cement-based concrete since any conveyor belt would tend to clog up with scattered concrete and in any event the short setting time calls for frequent cleaning of the apparatus used interrupting the motion of the belt.

Thus the technology used tends to rely on manual spreading of the concrete in moulds.

Even so it is difficult to meter out the right amount of concrete for each mould and so the hand trowelling tends to result in uneven thickness of the finished articles as from article to article and even in the thickness of an individual article.

One aspect of the present invention provides a metering device comprising a gravity or pressure feed, three perforated plates disposed transversely of the feed direction in the manner of gate valves with the central plate or the two outer plates being movable so as to align and misalign the perforations and with the central plate being perforated so as to be hollow to the extent of the desired volume to be metered.

Preferably the feed direction is vertical with the plates horizontal and equal in area to that of a mould with a plurality of perforations spread over that area. As a result the mould will be fed with large drops of concrete spread over the mould. These large drops can be further spread and caused to coalesce into a flat top slab by vibration and possibly by heat.

However the properties of polymer concrete are such that the use of heat is not desirable since it accelerates setting of the concrete and impairs its flow character; moreover, it is desirable that the vibration frequency is low enough not to cause appreciable heating of the concrete (it is known to cure the concrete by ultra-sonic vibration) and a frequency of about 5800 to 6000 Hertz has been found practical. The direction of vibration does not seem critical and can be vertical and/or horizontal.

Another aspect of the present invention provides a moulding machine especially for polymer concrete comprising a gravity or pressure feed, a metering device arranged to deliver spaced drops of the polymer concrete, a mould station wherein the drops are to fall onto a mould in a spaced manner, and a vibrator for imparting vibration to the mould.

An embodiment of the present invention will now be described by way of example with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a vertical section through a schematic polymer concrete moulding machine.

BEST MODE OF PERFORMING THE INVEN TION A mixing device for the two resin components and the quartz powder constituents of polymer concrete is arranged to discharge the mixed polymer concrete through its bottom and thus serves as a vertical feed 1. The device can be pressurised so the feed is a pressure feed or can rely on gravity so the feed is a mere gravity feed. A metering block 2 which is readily attachable and removable from the feed and readily dismountable for cleaning is attached to receive the polymer concrete from the feed. This block comprises three blades 3, 4 and 5 each having a central perforated area serving as a plate of a gate valve.The upstream blade 3 and the downstream blade 5 are each relatively movable in relation to the middle blade 4 so the perforations in blades 3 and 4 can be in register and those in blades 4 and 5 not and vice versa; this can be achieved by merely moving the middle blade. The perforations are in the form of elongate slots 6 with rounded ends, transverse to the direction of the relative motion, and spaced apart by lands 7 wider than the slots. The depth of the middle blade is such that the area of the perforations multiplied by the depth equals the amount to be metered making an allowance of say 5% to allow for the perforations not filling completely due to air locks and not emptying properly due to material holding up in the perforations.Conveniently the middle blade is mounted on a slide 8 driven by an eccentric 9, a low frequency vibrator 10 is provided to assist the middle blade to discharge its load of polymer concrete. The blades are of stainless steel or well polished tool steel and slide relative to each other in close sliding relationship. 'Anti-extrusion' grooves 11 can be provided around the central areas or valve plates.

The blades can be hardened to resist wear caused by the abrasive nature of the polymer concrete and in particular the fine particles which can be carried with the resin between the blades.

The polymer concrete thus enters the perforations in the middle blade when those perforations are in line with the perforations in the upstream blade and is discharged when the perforations in the middle blade are no longer in line with those in the upstream blade but are in line with those in the downstream blade.

Due to the plurality of perforations in the blades the polymer concrete drops from the metering block as spaced apart drops. A mould 1 2 in a mould station 1 4 is positioned, by means of a pusher 15, under the block so as to receive the drops. A vibrator 1 7 operating at 5000 to 6000 Hertz shakes the drops to cause them to coalesce and form a flat surface. When a mould has been filled, a subsequent mould pushes it in front of the subsequent mould into a curing station wherein the polymer is allowed to set or caused to set by heat.

Due to the rapid setting time of polymer concrete, it is important that the machine is readily strippable and cleaned between each batch of concrete mixed.

Claims

1. A metering device comprising a gravity or pressure feed, three perforated plates disposed transversely of the feed direction in the manner of gate valves with the central plate or the two outer plates being movable so as to align and misalign the perforations and with the central plate being perforated so as to be hollow to the extent of the desired volume to be metered.

2. A metering device according to claim 1 wherein the perforations are in the form of elongate slots transverse to the relative movement direction.

3. A metering device according to claim 1 or claim 2 wherein the depth of the middle plate is such that multiplied by the area of the perforations provides the volume to be metered.

4. A metering device according to anyone of the preceding claims wherein each plate is identically perforated but the two outer plates are misaligned so that in one position of the central plate where it is aligned with the upper of the two outer plates the central plate received a metered charge and then when it is moved out of alignment with the upper plate and into alignment with the lower plate can drop its charge through the lower plate without any further charge being able to enter the central plate.

5. A moulding machine especially for polymer concrete comprising a gravity or pressure feed, a metering device arranged to deliver spaced drops of the polymer concrete, a mould station wherein the drops are to drop into a mould in a spaced manner, and a vibrator for imparting vibration to the mould.

6. A moulding machine according to claim 5 wherein the metering device is as claimed in any one of claims 1 to 5.

7. A metering device substantially as herein described with reference to Fig. 1 of the accompanying drawings.

8. A moulding machine substantially as described with reference to Fig. 2 of the accompanying drawings.