GB2057283A

GB2057283A - Luxury machine having means for calibrating a metering pump

Info

Publication number: GB2057283A
Application number: GB8027628A
Authority: GB
Original assignee: UMENCO FOUNDRY PROCUCTS Ltd
Current assignee: UMENCO FOUNDRY PROCUCTS Ltd
Priority date: 1979-08-25
Filing date: 1980-08-26
Publication date: 1981-04-01
Also published as: GB2057283B

Abstract

The machine (10) includes a metering pump for drawing liquid from a reservoir (12) and supplying a metered quantity thereof to the mixing chamber and a calibration device comprising a measuring cylinder (14) whose lower end is connected via valve means (20, 26) to reservoir (12) and the metering pump. The valve means is arranged to selectively connect the measuring cylinder to either the metering pump or to the reservoir, or to connect the reservoir directly to the metering pump with the measuring cylinder isolated therefrom. Instead of the two valves (20, 26) a single three-way valve can be provided. The machine is preferably used to mix foundry moulding sand with a liquid binder, catalyst or acid hardener drawn from the reservoir. <IMAGE>

Description

SPECIFICATION Improvements in or relating to mixing machines This invention relates to a mixing machine having a calibration device for calibrating the quantities of materials supplied by and dispensed therefrom and more particularly, but not exclusively, to a mixing machine such as, for example, a mixing machine which is mixing and dispensing moulding sand.

The moulding sand concerned is utilised to produce moulds and cores for use in the production of castings, and normally consists of a mixture of sand, and liquid additives. It is necessary to accurately control the quantities of sand and liquid additives which are mixed together by the mixing machine in order to ensure that the castings produced do not suffer from defects. It is therefore necessary to accurately calibrate the quantities of the materials which are drawn from their respective storage reservoirs by the mixing machine and which are then mixed together by said machine.

Usually, the mixing machine includes metering pumps, which draw quantities of the liquid additives from their associated reservoirs. In order to calibrate the quantities of liquid additives drawn from the reservoirs by the associated metering pumps, it is normal practice to disconnect the outlet pipe from the associated pump, to run the pump for a measured period of time at a particular speed setting, to collect the liquid issuing from the outlet pipe, to measure the weight of the liquid collected, and then to calculate the rate of flow of liquid for the particular pump speed setting.

It will be appreciated that this calibration procedure is a time consuming operation and as it is usual in a conventional mixing machine for both the metering pump supplying a resin binder and the metering pump supplying a catalyst to each have a range of speed settings, then clearly the entire calibration procedure is extremely time consuming.

Furthermore, the metering pumps normally supply the liquid additives to a spray head from which they are sprayed on to the sand being supplied by the machine. It is usual when calibrating the machine, to disconnect the outlet pipes from the metering pumps at the spray head in order to measure the quantity of liquid flowing from the outlet pipe, and it is therefore possible that an error could occur as the quantity of liquid discharged from the outlet pipe may not be identical to the quantity of liquid discharged from the spray head. It will be appreciated that the normal calibration procedure is therefore not only a time consuming operation but also possesses inherent disadvantages with regard to its accuracy, and the object of this invention is to provide a mixing machine having a calibration device in which the above disadvantages are alleviated.

According to this invention, a mixing machine includes at least one metering pump for drawing liquid from a reservoir and supplying a metered quantity of liquid therefrom and a calibration device which comprises-a measuring chamber, the lower end of which is connected via valve means to both the reservoir and the metering pump; wherein the valve means is arranged to selectively connect the measuring cylinder to either the metering pump or the reservoir, or to connect the reservoir directly to the metering pump with the measuring cylinder isolated therefrom.

Preferably, the lower end of the chamber is connected to a stem portion of an inverted T-shaped pipe connector. Preferably, also, the valve means comprises a first valve disposed between the chamber and both of the connection points thereof to the pump and the reservoir to control the supply of liquid into and the withdrawal of liquid from the chamber, and a second valve disposed between the first valve and the reservoir to control the flow of liquid from the reservoir.

Preferably, the first valve is connected between the stem oftheT-shaped connector and the chamber and the second valve may be connected in or between one arm of the T-shaped connector and the reservoir and the other arm of the T-shaped connector may be connected to the metering pump. Preferably, also, the first and second valves each comprise a manually-operated on/off valve.

Alternatively, the valve means may comprise a single three-way manually-operated valve disposed at the junction of the stem and the arms of the T-shaped connector.

Preferably, the measuring chamber comprises a measuring cylinder formed at least partially of transparent material and the cylinder may be provided with a graduated scale so that the volume of liquid flowing therefrom can be determined by visual inspection. Preferably, also, the upper end of the cylinder has a closure device releasably connected thereto for sealing the upper end of the cylinder.

A preferred embodiment ofthis invention will now be described, by way of example only, with reference to the accompanying drawings, of which: Figure 1 is a diagrammatic side elevation of a mixing machine including a calibration device; and Figure 2 is a diagrammatic side elevation of a mixing machine including a modified calibration device.

Referring now to Figure 1 of the drawings, a mixing machine indicated generally at 10 which is particularly suitable for mixing and dispensing moulding sand is provided with at least one metering pump (not shown) for drawing liquid from a tank 12.

The mixing machine 10 includes a calibration device comprising a measuring cylinder 14formed of a transparent material such as glass.

The cylinder 14 has a graduated scale 16 extending along the length thereof by means of which the volume of liquid flowing from the cylinder 14 can be accurately determined. The upper end of the cylinder 14 has a screw-threaded cap 18 releasably secured thereto, by means of which the open top of the cylinder 14 can be sealed. The cylinder 14 also has a The drawings originally filed were informal and the print here reproduced is taken from a laterfiled formal copy.

first manually-operated valve 20 connected to the lower end thereof through which liquid is admitted to or withdrawn from the cylinder 14.

The opposite side of the valve 20 to the cylinder 14 is connected to a stem portion 22 of an inverted T-shaped pipe connector indicated generally at 24.

One end ofthe connector 24 has a second manually-operated valve 26 connected thereto and the valve 26 is connected by a pipe 28 to the tank 12.

The other end of the connector 24 is connected by a pipe 30 to the metering pump of the mixing machine 10 which is to be calibrated by the device.

The calibration device is adapted to be connected permanently in position between the tank 12 and the particular metering pump of the mixing machine 10 which it is to be used to calibrate, and where the mixing machine 10 is for mixing a moulding sand formed of measured quantities of sand, liquid resin binder and liquid catalyst or acid hardener, a separate calibration device is connected between the binder storage tank and the associated metering pump and between the catalyst or acid hardener storage tank and the metering pump associated therewith.

In operation, when the metering pump is to be calibrated, the cap 18 is removed from the upper end of the cylinder 14 and the valves 20 and 26 are both opened to allow liquid to flow under gravity from the tank 12 into the cylinder 14, until the cylinder 14 is full. The valve 20 is then closed to retain the liquid in the cylinder 14.

If desired, the metering pump can be actuated to draw liquid from the tank 12 and supply it in the conventional manner to, for example, a spray head in the mixing machine 10 from which liquid is sprayed on to and mixed with the sand. This operation of the metering pump with the valve 20 closed has no effect on the level of the liquid in the cylinder 14.

When the metering pump is to be calibrated, the valve 26 is closed thus isolating the feed from the tank 12 from the metering pump. The valve 20 is then opened so that the metering pump can only draw liquid from the cylinder 14. The mixing machine 10 is operated for a measured period of time (for example for ten to sixteen seconds) after which the valve 20 is closed and the valve 26 is immediately opened. The mixing machine 10 can then be operated in the normal manner.

The liquid in the cylinder 14 is allowed to settle and the volume of liquid displaced during the measured period of time can then be determined by using the graduated scales 16. It will be appreciated that this measurement of volume gives the true volume of liquid supplied by the metering pump from the spray head in the machine 10. It is then possible to convert this volume to an equivalent weight, and then to express this as a percentage of the weight of sand to determine the ratio between the weight of sand and liquid mixed therewith by the mixing machine 10.

The cap 18 is then replaced in order to prevent accidental overflow from the cylinder 14 if the valve 20 is opened.

In Figure 2 of the drawings the mixing machine 10 is shown with a modified calibration device and for ease of reference the components therein which are identical to the components described with reference to Figure 1 of the drawings have been allocated the same reference numerals. In this modified calibration device, the two separate manually-operated valves 20 and 26 are replaced by a three-way manually-operated valve 32. The valve 32 is either mounted in an inverted T-shaped connector34 at the junction of the stem and the arms thereof, or the body of the valve 32 can itself constitute such an inverted T-shaped connector.

In operation, the three-way manually-operated valve 32 is arranged in one of its three positions to provide a connection between the pipe 28 and the pipe 30 with the cylinder 14 isolated therefrom. In the second position of the valve 32, a connection is provided between the cylinder 14 and the pipe 30 and in the third position of the valve 32 connections are provided between the pipe 28, the pipe 30, and the cylinder 14.

It will therefore be appreciated that the operation of this modified calibration device thus closely follows the operating procedure of the calibration device described with reference to Figure 1 of the drawings, the only difference being that the single three-way valve 32 is moved to its different positions to correspend to the above described opening and closing of the valves 20 and 26.

The calibration procedures described above for the mixing machine ensure that the metering pump or pumps therefore are accurately and easily cali brated without the need to disconnect any pipes from the metering pumps or, indeed, any need to stop operation of the mixing machine.

It will be appreciated that this calibration device is suitable for use with either a metering pump of a sand mixing machine which is supplying liquid resin binder or with the metering pump of such a machine which is supplying liquid catalyst or acid hardener, or indeed, with any other type of mixing machine containing metering pumps which need to be accu rately calibrated.

Claims

1. A mixing machine including at least one met ering pump for drawing liquid from a reservoir and supplying a metered quantity of liquid therefrom and a calibration device comprising a measuring chamberthe lower end of which is connected via valve means to both the reservoir and the metering pump, wherein the valve means is arranged to selec- tively connect the measuring cylinder to either the metering pump or the reservoir orto connect the reservoir directly to the metering pump with the measuring cylinder isolated therefrom.

2. A mixing machine according to claim 1, wherein the lower end of the chamber is connected to a stem portion of an inverted T-shaped pipe con nector.

3. A mixing machine according to claim 1 or claim 2, wherein the valve means comprises a first valve disposed between the chamber and both of the connection points thereof to the pump and the reservoir to control the supply of liquid into and the withdrawal of liquid from the chamber, and a second valve disposed between the first valve and the reservoirto control the flow of liquid from the reservoir.

4. A mixing machine according to claim 2 and claim 3, wherein the first valve is connected between the stem of the T-shaped connector and the chamber.

5. A mixing machine according to claim 4, wherein the second valve is connected in or between one arm of the T-shaped connector and the reservoir, and the other arm of the T-shaped connector is connected to the metering pump.

6. A mixing machine according to any one of claims 3 to 5, wherein the first and second valves each comprise a manually-operated on/off valve.

7. A mixing machine according to claim 1 or claim 2, wherein the valve means comprises a single three-way manually-operated valve disposed at the junction of the stem and the arms of the T-shaped connector.

8. A mixing machine according to any one of the preceding claims, wherein the measuring chamber comprises a measuring cylinder formed at least partially of transparent material.

9. A mixing machine according to claim 8, wherein the cylinder is provided with a graduated scale so that the volume of liquid flowing therefrom can be determined by visual inspection.

10. A mixing machine according to claim 8 or claim 9, wherein the upper end of the cylinder has a closure device releasably connected thereto for sealing the upper end of the cylinder.

11. A mixing machine constructed, arranged and adapted to operate substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawings.