GB2350434A

GB2350434A - Metering liquid additives by weight

Info

Publication number: GB2350434A
Application number: GB0006941A
Authority: GB
Inventors: Roland J Wood; David H Beet; Jason Raftrey; Roy Jones
Original assignee: ADMIX WATER SERV Ltd
Current assignee: ADMIX WATER SERV Ltd
Priority date: 1999-03-23
Filing date: 2000-03-23
Publication date: 2000-11-29
Also published as: GB0006941D0; GB9906552D0

Abstract

A metering dispenser comprises fluid reservoirs (11,12,13) and weighing means for monitoring the weight of the fluid reservoirs (11,12,13). Each fluid reservoir (11,12,13) has a fluid inlet by which the fluid reservoir (11,12,13) can be charged with a fluid and a fluid outlet by which fluid from the fluid reservoir (11,12,13) can be dispensed. The fluid reservoirs (11,12,13) also have an inlet for gas underpressure, eg compressed air, to displace fluid from the fluid reservoir (11,12,13). The dispenser is particularly suitable for the addition of additives to concrete.

Description

2350434 ADMI 133.GB.wpd Title - Metering Dispense This invention relates

to a metering dispenser, and in particular to a metering dispenser suitable for the dispensing of known weights of one of a number of fluids. The apparatus of the invention is particularly suitable for the addition of known weights of additives to bulk 5 volumes of fluid, eg concrete or other cementitious products.

Ready-mixed concrete is generally prepared at a plant and then delivered to site in a mixer lorry. Clearly, it is essential that the concrete should be of the right consistency to be dispensed from the lorry at the site, that it should not go off prematurely, either before delivery or too quickly after delivery, but equally that it should not take an excessively long period of time to go off. In order to achieve these properties, specific quantities of additives such as accelerators or retardants are generally added to the concrete before the lorry leaves the plant. Additives may also be added for other purposes, eg as pigments.

Known forms of apparatus for metering quantities of additive into bulk concrete suffer from numerous disadvantages. For instance, the additive may be weighed into a hopper mounted on load cells. Where a variety of different additives are used, as is generally the case, this can lead to problems of cross-contamination. In addition, because the additive may be gravity-fed to the lorry, the apparatus must be mounted at an elevated position within the structure of the plant, making calibration extremely difficult, due to vibration within the plant structure. In addition, known systems are relatively costly, eg because they utilise multiple load cells or expensive pumps are required to raise and/or discharge the additive to the necessary height. In addition, the system must be flushed between uses with differing additives, so as to minimise cross- contamination. This may make it difficult or impossible to add two different additives to the same bulk.

There has now been devised a metering dispenser, of particular use in dispensing additives to a batch, eg of concrete, which overcomes or substantially mitigates the above-mentioned or other disadvantages.

ADMI 133.GB.wpd 2 According to the invention, there is provided a metering dispenser comprising at least one fluid reservoir, weighing means for monitoring the weight of said at least one fluid reservoir, said at least one fluid reservoir having a fluid inlet by which the fluid reservoir can be charged with a fluid and a fluid outlet by which fluid from the fluid reservoir can be dispensed, and said at least one fluid reservoir having an inlet for gas under pressure, introduction of such gas under pressure being effective, in use, to displace fluid from the fluid reservoir.

The dispenser according to the invention is advantageous primarily in that it permits the accurate dispensing of quantities of fluids. Because the fluids are dispensed under positive pressure of gas, the dispenser does not have to be mounted at an elevated level, or not even within the plant structure at all, leading to reduced cost and ease of maintenance and calibration etc. The apparatus is relatively inexpensive, not least because a small number of load cells, eg one or two load cells, may be sufficient to weigh the fluid reservoir.

in one preferred embodiment, there are provided a plurality of fluid reservoirs. In such a case, each reservoir and associated pipework can be dedicated to a particular fluid, thereby eliminating risk of cross-contamination and allowing more than one additive to be added to the same bulk. The fluid reservoirs may take any suitable form, but in a preferred embodiment are cylindrical, the cylinders being disposed horizontally. A plurality of such cylinders may be arranged in parallel, or the cylinders may be concentric.

The fluid reservoirs are preferably fixed on a rigid frame which in turn acts upon the weighing means. The weighing means most preferably comprises one or more load cells. More than one load cell may be used, but for many applications it is possible to utilise only one or two load cells, particularly since the fluid in the reservoirs will find its own reproducible level. A single load cell is preferably positioned generally centrally with respect to the plurality of reservoirs.

In another preferred embodiment, a single fluid reservoir is used- In this case, the fluid reservoir is preferably connected to a supply of water so that, if necessary or desirable, it can ADM I 133.GB.wpd 3 be flushed out between charges of differing fluids. The fluid reservoir in this case is preferably mounted to discharge fi7om its base, so as to facilitate emptying.

The gas under pressure is most preferably compressed air, a supply of which will in most instances be readily available, being used in the plant for many other purposes. The compressed air is preferably supplied to the fluid reservoirs at a pressure of less than 50psi, most preferably a pressure of between 20 and 30psi.

Charging of the or each fluid reservoir may be carried out by gravity feed, or one or more pumps may be provided.

Operation of the dispenser according to the invention is most preferably performed under microprocessor or computer control. A suitable control unit may have input means such as a keypad and will be operably linked to the various valves etc necessary for operation of the system.

Although described herein principally with reference to the mixing of additives with concrete, the dispenser of the invention is of potential utility in any situation in which measured quantities of a fluid are to be added to a bulk.

The invention will now be described in greater detail, by way of illustration only, with reference to the accompanying drawings, in which Figure I is a schematic view of a first embodiment of a dispenser according to the invention; Figure 2 is a side view of a reservoir assembly forming part of the apparatus of Figure 1; Figure 3 is an end view of the reservoir assembly of Figure 2; Figure 4 is a cross-sectional side view of a second form of reservoir assembly which can be used as part of the apparatus of Figure 1; ADII I 133.GB.wpd 4 Figure 5 is a horizontal cross-section of a third form of reservoir assembly; and Figure 6 is a schematic view of a second embodiment of a dispenser according to the invention.

Referring first to Figure 1, a dispenser according to the invention is suitable for the dispensing of three different liquid additives into ready-mixed concrete lorries prior to departure of the lorry from a ready-mixed concrete plant. The dispenser comprises three cylindrical reservoirs 11, 12,13 which are gravity fed with the three additives from respective bulk tanks 14,15,16 via pipes 17,18,19 each of which is fitted with an air-actuated ball valve 21,22,23.

Additive can be discharged from each reservoir 11,12,13 via an outlet pipe 24,25,26, each of which is fitted with an air-actuated ball valve 27, 28,29. The outlet pipes 24,25,26 are positioned such that their discharge ends are located above a lorry into which the additive is delivered. Typically, the ends of the outlet pipes 24,25,26 may be approximately five metres or more above ground level. 15 Each reservoir 11,12,13 is also connected via a compressed air manifold 31 and an L-port valve 32,33, 34 to a supply of compressed air (not shown). The L-port valves 32,33,34 are switchable between vent positions (as shown in Figure 1), in which the reservoir 11, 12,13 is open to the atmosphere, to operating positions in which compressed air under a pressure, typically, of 20-30 psi is supplied to the respective reservoir 11,12,13. The effect of the 20 compressed air is to discharge material from the respective reservoir 11, 12,13 via the valve 27,28,29 and the discharge pipe 24,25,26. Thereservoirs 11,12,13 are shown in more detail in Figures 2 and 3. Eachreservoir 11,12,13 has the form of a cylindrical tank, the tanks being welded together in the arrangement shown and mounted on a support frame 41. The support frame 41 is in turn mounted on two load 25 cells 42 (only one of which is shown) which act between the support frame 41 and the ground. As shown in the drawings, the lower two reservoirs 11, 12 are of equal volume and ADM I 133.GB.wpd 5 the upper reservoir 13 is of somewhat greater diameter. In other embodiments, the volumes of the reservoirs may all be equal or they may all be different.

Between operations the reservoirs 11, 12,13 are normally maintained in a full or substantially fall condition, and/or at a prescribed weight, by opening of the respective valves 21,22,23 and gravity feed of additive from the respective bulk tanks 14,15,16. When it is desired to dispense a specified weight of an additive from, say, reservoir 11, the load cell is tared and the L-port valve 32 switched to the operating position. Compressed air is thereby supplied to the reservoir 11, displacing additive through the valve 27 and discharge pipe 24. The weight of the reservoir assembly is monitored by the load cell 42, the supply of compressed air being switched off (by switching of the L-port valve 32 to the vent position) once the desired weight of additive has been displaced from the reservoir 11.

In practice, operation of the dispenser is controlled by a microprocessorcontrolled control unit (not shown) which automatically actuates the various valves. Generally, such a control unit will include a keypad for input of information such as the particular additive to be dispensed and the required amount.

The dispenser described above is suitable for the dispensing of three different additives. If a larger number of additives is to be used, then a larger number of reservoirs may be fitted to the support frame or two or more units such as that described above may be used, each having three reservoirs or whatever other number is appropriate.

The embodiment of the invention shown in Figure 4 differs from that described above in that there are again three cylindrical reservoirs 51, 52,53, but these are concentric and of differing length. The central reservoir 51 is thus cylindrical, whilst the middle and outer reservoirs 52,53 are in effect annular. In other respects, this embodiment is identical to that of Figures I to 3. 25 Figure 5 shows another possible arrangement of reservoirs, in this case comprising a single cylindrical drum 61 divided by internal partitions into four reservoir compartments ADM I 133.GB.wpd 6 62,63,64,65.

Referring now to Figure 6, a second embodiment of a dispenser according to the invention comprises a single cylindrical reservoir 71 which in this embodiment is mounted vertically. The reservoir 71 is suspended from a pair of load cells 90,91.

The reservoir 71 is connected via an inlet pipe 72 to a manifold 73 which is in turn connected to three bulk tanks 74,75,76 containing three different fluid additives. Appropriate valves etc (not shown), eg solenoid valves, are provided for selection of the desired additive to be transported to the reservoir 71. The manifold 73 is also connected to a water supply 79. Additive from the selected tank 74,75,76 is transported to the reservoir 71 by a pump 77, via 10 a non-return valve 78. The weight of the reservoir 71 is measured by the load cells 90,91, the pump 77 being deactivated when the desired weight of additive has been filled into the reservoir 71. A known volume of water may be carried into the reservoir 71, preceding the additive, and a further volume of water may be drawn into the reservoir 71 behind the additive. This ensures that all of the desired quantity of additive is carried into the reservoir is 71 and also fluidises the additive, thereby facilitating its subsequent discharge from the reservoir 7 1. Additive is discharged from the reservoir 71 by a compressed air supply 82 and passes through a valve 81 and an outlet pipe 80. The valve 81 has a closed position for charging of the reservoir 71 with additive, and a discharge position for connecting the reservoir 71 to the 20 outlet pipe 80. The reservoir 71 is provided with a vent 83 to enable the reservoir 71 to be flushed with water. Thus, between charging with different additives the reservoir 71 can be filled with water which is then discharged through the vent 83. As for the first embodiment, a microprocessor-controlled control unit (not shown) is provided 25 to automate operation of the apparatus, by controlling operation of the various valves etc.

ADM I 133.GB.wpd 7

Claims

1. A metering dispenser comprising at least one fluid reservoir, weighing means for monitoring the weight of said at least one fluid reservoir, said at least one fluid reservoir having a fluid inlet by which the fluid reservoir can be charged with a fluid and a fluid outlet by which fluid from the fluid reservoir can be dispensed, and said at least one fluid reservoir having an inlet for gas under pressure, introduction of such gas under pressure being effective, in use, to displace fluid from the fluid reservoir.

2. A dispenser as claimed in Claim 1, wherein there are provided a plurality of fluid reservoirs.

3. A dispenser as claimed in Claim 2, wherein the fluid reservoirs are cylindrical, the cylinders being disposed horizontally.

4. A dispenser as claimed in any preceding claim, wherein the at least one fluid reservoir is fixed on a rigid frame which in turn acts upon the weighing means.

5. A dispenser asclaimed in Claim 1, wherein a single fluid reservoir is provided.

6. A dispenser as claimed in any preceding claim, wherein the gas under pressure is compressed air.

7. A dispenser as claimed in Claim 6, wherein the compressed air is supplied to the fluid reservoir(s) at a pressure of between 20 and 30psi.

8. A dispenser as claimed in any preceding claim, wherein charging of the or each fluid reservoir is carried out by gravity feed.

9. A dispenser as claimed in any one of Claims I to 7, wherein the or each fluid reservoir is charged by a pump.

ADMI 133.GB.wpd 8

10. A metering dispenser substantially as hereinbefore described and as illustrated in Figure 1.

11. A metering dispenser substantially as hereinbefore described and as illustrated in Figure 6.