GB2068475A

GB2068475A - Metering appliance

Info

Publication number: GB2068475A
Application number: GB8101954A
Authority: GB
Original assignee: Arcana Chem-Pharm Fabrik GmbH
Current assignee: Arcana Chem-Pharm Fabrik GmbH
Priority date: 1980-01-31
Filing date: 1981-01-22
Publication date: 1981-08-12
Also published as: DE3100708A1; FR2475152A1; IT8119422A0; IT8119422A1; IT1169029B

Abstract

A fluid driven metering appliance has a drive piston 4 which moves to and fro because of the fluid pressure, the piston rod 12 activating a product pump 2 for a product which is to be mixed with the fluid. The effective stroke of the product pump is variable. The appliance has a mechanically operated closure valve 7 for the fluid supply, which is movable between two conditions in dependence upon the amount of product contained in a product container. The product pump 2 is arranged outside the fluid drive on the piston rod 12 of the drive piston 4 and is connected to the product container. <IMAGE>

Description

SPECIFICATION Metering appliance The invention relates to a metering appliance with fluid drive, which has a drive piston, which moves to and fro because of the pressure of the fluid, the piston rod of which operates a product pump for the product which is to be mixed with the fluid in a changing ratio, whereby the effective stroke of the product pump is variable and the fluid emitted by the fluid drive is mixed with the product emitted from the product pump.

Metering appliances of this kind are used for the production of dilutions of disinfectants or for the mixing of products such as detergents or flocculation agents with water or for the addition of veterinary hormones to animal feeding stuffs.

In the preparation of solutions for use, we are familiar with mixing appliances which use the principle of a Venturi tube. The excess pressure on the one side of the Venturi tube operates a rubber bag which is filled with a concentrate of disinfectant. The accuracy of this arrangement leaves much to be desired. With these appliances it varies according to the quantity withdrawn and it is naturally only applicable for a specific viscosity. Small variations in viscosity require variations of concentration in the solution to be used.

Furthermore we are familiar with metering pumps which measure the quantity of the water flow with a water gauge. The latter emits electric impulses in proportion to the quantity of water and it regulates electronically a piston metering pump which meters out the disinfectant. The vulnerability of the electric design is great and the constructiorl of these metering pumps is very complicated. High maintenance costs and dependence on the electric circuit are additional disadvantages.

Furthermore, electrically operated metering pumps are well known. These are either diaphragm or piston metering pumps. If proportional metering is to occur with these appliances, then naturally the water must also be metered. These pumps cannot cope with metering independently of the flow of water without additional equipment.

Moreover we are familiar with a metering pump which is placed inside the water piston drive, whereby the housing of the metering pump is placed inside the cylinder of the water piston drive which is filled with water. Therefore it is a disadvantage that, if the metering pump should leak, the water will be polluted. An additional disadvantage is that if the flow to the metering pump is interrupted, the water piston drive carries on working and therefore a metering of the supply is no longer possible.

It is the purpose of the invention to produce a metering appliance which renders possible an exact metering out of the product which is to be mixed with the fluid whereby a too low level of concentration which has once been set is avoided and a leakage of the product into the liquid is prevented.

The invention provides a fluid driven metering appliance, which has a drive piston which moves to and fro because of the pressure of the fluid, the piston rod activating a product pump for the product which is to be mixed in with the liquid in changing ratio, whereby the effective stroke of the - product pump is variable and the fluid which is drained out of the fluid drive is mixed with the product which is drained out of the product pump, the appliance having a mechanically operated closure valve for the fluid supply, which is movable between two conditions in dependence upon the amount of product contained in a product container and the product pump is arranged outside the fluid drive on the piston rod of the drive piston and is connected to the product container.

This design permits an automatic metering out of the product, whereby the regulated concentration during the operation of the appliance can be maintained exactly.

As the appliance, according to the invention, switches itself off mechanically if the regulated level of the specified quantity of the product in the product container is not reached, and as the product pump is separated spatially from the fluid drive, so that if the product pump is not watertight the concentration of the product in the fluid is not impaired, then accuracy of metering, owing to breakdowns in the operation of the appliance, is not impeded.

An additional feature of the invention consists in arranging for the housing of the product pump to be movable on the piston rod of the drive piston, whereby the piston rod of the drive piston at the end which is protruding from the fluid drive is designed as a piston for the product pump, and the product pump is movable up to a movable stop opposite the fluid drive. This design renders possible a very simple construction of the product pump, whereby the stroke of the product pump is determined by the stop. Because the housing of the product pump moves, the number of places to be made watertight is reduced to a minimum.

Furthermore, according to the invention, the stop valve on the housing of the fluid drive is designed as a solenoid valve which is operated by a lever placed on the housing of the fluid drive, on to which the weight of the product container or a float provided in the product container operates against the force of a spring. Through this process a faultless switching off of the appliance is made possible before the product container is absolutely empty.

Moreover the invention provides a product pump for a metering device, which is characterised in that in a housing in a chamber a piston is positioned on a piston rod connected to a drive and it divides the chamber into a front and a rear piston displacement area, whereby the front piston displacement area is connected to a feeding pipe, which is fitted with a suction valve, and via an outlet orifice with a pipe for the product fitted with an outlet valve and whereby the rear piston displacement area is connected with the front piston displacement area via a transfer port which discharges into the outlet valve into the pipe for the product.

Thereby it is advantageous that the measuring out of the product should not only occur in the forward movement of the piston but also in the backward movement. The measuring out occurs therefore on both sides of the piston. In this process there is a significantly more uniform metering out of the product, whereby the inward flow of the product is not interrupted by the backward movement of the product piston.

An additional characteristic of the invention enables the effective stroke volume in the front piston displacement area to be twice as great as the effective stroke volume in the rear piston displacement area. Thereby one may achieve a virtually continuous flow of the product towards the metering appliance.

An additional characteristic of the invention consists in arranging for the housing on the piston rod to be movable as far as a movable stop for the regulation of the stroke volume.

This development renders possible a very simple construction of the pump for the product whereby the stroke of the product pump is determined by the stop. Because the housing of the product pump is moving the number of points to be made watertight is reduced to a minimum.

By way of example, specific embodiments of the invention will now be described, with reference to the accompanying drawings, in which: Figure 1 is a schematic illustration of an embodiment of metering appliance according to the invention; Figure 2 is a perspective view of a practical embodiment of metering appliance according to the invention; Figure 3 is a perspective view of the appliance of Figure 2 from the rear; Figure 4 is a view similar to Figure 2 but showing an alternative embodiment; Figure 5 is a cross-section through an embodiment of appliance according to the invention; Figure 6 is a cross-sectional view on lines B-B and C-C of Figure 5; Figure 7 is a cross-sectional view on line A-A of Figure 5;; Figure 8 is a cross-section similarto Figure 5 but showing an alternative embodiment of the invention; and Figure 9 is a cross-section on lines B-B and C-C of Figure 8.

Figure 1 illustrates schematically a metering appliance, and shows a fluid drive 1, a product pump 2, and a product container 3.

The fluid drive 1 has a drive piston 4, which is moved to and fro in a cylinder 5 arranged in a housing, by the pressure of the fluid. The cylinder 5 is connected on both sides of the drive piston 4 via channels 6 to a switch valve 7, which is connected via channels 8 with the inflow orifice 9 and the outflow orifice 10 of the housing.

The cylinder 5 is closed to the outside by means of a lid 11, through which only the piston rod 12 of the drive piston 4 extends. On the piston rod 12 there is a switching arm 13 attached, which operates the switch valve 7 via a switch rod 14. For this purpose the switching rod 14 is connected via a spring 1 5 with a distributor arm attached to the switch valve 7, so that the switch valve 7 is switched over into one of two end positions by the movement of the drive piston 4.

The outer end of the hollow piston rod 12 of the drive piston 4 is closed and it bears the housing 17 of the product pump 2. In the housing 1 7 a cylinder room area 18, closed on one side, has been constructed, which is placed with slack on the piston rod 12, whereby the piston rod 12 acts, as piston for the product pump. On its open side the cylinder area 1 8 is made waterproof by means of a casing 19. On the side of the housing 17, valves 20 have been fixed which adjoin the cylinder area 1 8 via channels. On the side of the inward flow the product pump 2 is connected via a pipe 21 with the bottom side of a product container 22. The product container 22 is placed upon one end of a lever 23 which is swivel mounted on the housing of the fluid drive. On the other end 24 of the lever 23 a spring 25 acts.An operating rod 26 projects from the other end 24 of the lever 23 and is connected to a solenoid valve 27. This solenoid valve 27 is positioned in the inflow pipe to the fluid drive 1.

On the housing 17 of the product pump 2 a thread is provided on to which a female adjusting nut 29 has been screwed. Between the housing 17 of the product pump 2 and the female adjusting nut a stop 30 has been arranged, which surrounds the thread pipe 28 with slack and is fixed by rods 31 on to the housing of the fluid drive 1. The stop 30 bears a metering scale, on which the regulated concentration can be read.

The metering appliance works as follows. With the opening of a stop valve in a pipe with fluid, e.g.

in a water piping system, the appliance is ready for use. It only works if, in the product container 22, where the substance to be mixed in (disiniectants, detergents, flocculation agents, addition of veterinary hormones to animal feeding stuffs) is present in sufficient quantity. In this case, the solenoid valve 27 is opened mechanically via the lever 23, and the water passes through the switch valve 7 into the fluid drive 1. The drive piston 4 is operated by the pressure of the water. The switching arm 1 3 fixed on the piston rod 12 also moves with the drive piston 4 in the same direction. The switching arm 1 3 is connected by the switching rod 14 via the switching spring 1 5 and the distributor arm 1 6 with the switch valve 7.

If now because of the movement of the piston with the parts described above the spring 15 moves over the axle centre of the switch valve, then the spring 1 5 pulls the distributor arm around by approximately 600 to the other side. The switch valve thereby releases the side of the piston previously connected with the feed pipe for the flowing off and simultaneously releases the opposite side of the piston for the inward flow of water out of the piping system.

The piston rod 12, which is simultaneously the piston for the product pump 2, is thereby moved, with the drive piston 4 in the direction of the longitudinal axis. Thereby in proportion to the movement of the piston in the product pump 2, the product is forced out once and sucked in once.

The product which has been sucked in is pressed along the piston rod to the valves 20, or the other way round from the valves 20 along the piston rod and then it is sucked into the pump area. The piston of the product pump 2 has sufficient slack in the housing of the pump for the product to flow through the intermediate space to the valves 20, or the other way round. The regulation of the metering results as the stroke length is changed on the product pump 2 with a female adjusting nut. The product pump 2 moves with the drive piston, in so far as the female adjusting screw permits slack.

Automatic switching off of the appliance occurs with a smaller weight of storage container via the solenoid valve, which is operated mechanically.

The switching on or off is dependent on the weight of the storage container.

A variation of a product pump, according to the invention, is illustrated in Figure 8 and Figure 9.

To the outer end of the hollow piston rod 12 of the drive piston 4 there is a piston rod 40 attached, which bears the housing 1 7 of the product pump 2. In the housing 1 7 a cylinder area 18 has been developed which is closed on one side, in which a piston 41 of the product pump 2 has been arranged on.the piston rod 40. On its open side the cylinder area 1 8 has been made waterproof by means of a casing 1 9. On the side of the housing 1 7 valves have been fixed, which adjoin the cylinder area 1 8 via channels. On the side of the inward flow the product pump 2 is connected to a pipe 36 via a suction valve 38.

On the housing 17 of the product pump 2 a thread 28 has been developed, on to which a female adjusting nut 29 has been screwed.

Between the housing 1 7 of the product pump 2 and the female adjusting nut, a stop 30 has been arranged, which surrounds the thread pipe 28 with slack and is fixed by rods 31 on to the housing of the fluid drive. The stop 30 bears a metering scale, on which the concentration chosen can be read.

The cylinder area 18 is divided by the piston 41 into a front piston displacement area 18' and a rear piston displacement area 18". The front piston displacement area 1 8 is positioned at the front of the piston 41, the rear piston on the side of the piston rod 40. The volume of the front piston displacement 1 8' is twice as great as the volume of the rear piston displacement 1 8". With the forward movement of the piston 41 half the product is passed back out of the front piston displacement 18' into the rear piston displacement 18" via a transfer port 42, the other half is transported through the outlet 37.On the backward movement of the piston 41 the amount of the product which has been sucked in from the rear piston displacement 1 8" during the forward movement, is likewise transported out through the transfer port 42.

At the same time in the front piston displacement 18' the product is sucked in again in the inlet valve 38. Therefore sucking in occurs once for each stroke and the quantity that has been sucked in in two portions is squeezed out half by half from the front and the rear piston displacement.

If the piston 4 together with the piston rod 12 of the fluid drive 1 and the piston 41 of the product pump which is attached, is moved forwards, (piston rod coming out of the fluid drive), then the product which is in front of the piston 41 is expelled through the outlet valve 39 (suction valve 38 closed). Via the connecting channel 42 to the rear piston displacement 18" on the rear side of the piston, 50% of the product, which has been expelled in front of the piston 41, is taken in by the increasing volume on the rear side of the piston of the rear piston displacement 1 8". After switching the fluid drive into the backward movement, the product which is now on the one hand behind the piston 41, is expelled via the connecting channel 42 to the outlet 37 (outlet valve 39 closed to the front piston displacement 18').On the other hand, a fresh supply of the product is sucked through the suction valve 38 into the front piston displacement 18'. After renewed switching over of the fluid drive, the process described above is repeated.

The metering adjustment occurs because the length of the stroke is adjusted by a female adjusting nut on the product pump 2. The product pump 2 moves with the drive piston in so far as the female adjusting nut allows for slack.

In the operating example, illustrated in the diagrams, the piston rod 40 of the product pump 2 is, in accordance with the invention, connected so that it may be detached, by means of a rivet 43, from the piston rod 12 of the fluid drive 1. Both the piston rods can be screwed together or constructed in one piece. Furthermore even another system can be provided, as a drive for the product pump, other than a direct coupling with a fluid drive. So, for example, the product pump can, according to the invention, be driven by a motor, regulated in proportion to the quantity of the liquid flowing through, into which the product is metered out.

Claims

1. A fluid driven metering appliance, which has a drive piston which moves to and fro because of the pressure of the fluid, the piston rod activating a product pump for the product which is to be mixed in with the liquid in changing ratio, whereby the effective stroke of the product pump is variable and the fluid which is drained out of the fluid drive is mixed with the product which is drained out of the product pump, the appliance having a mechanically operated closure valve for the fluid supply, which is movable between two conditions in dependence upon the amount of product contained in a product container and the product pump is arranged outside the fluid drive on the piston rod of the drive piston and is connected to the product container.

2. A metering appliance according to claim 1, in which the housing of the product pump is arranged so that it can move on the piston rod of the drive piston, whereby the piston rod of the drive piston is constructed as the piston of the product pump on its end protruding from the fluid drive and the product pump can move up to a movable stop opposite the fluid drive.

3. A metering appliance according to claim 1 or claim 2, in which the closure valve is constructed as a solenoid valve on the housing of the fluid drive, and the solenoid valve is operated by a lever placed on the housing of the fluid drive, on to which the weight of the product container or a float provided in the product container works against the force of a spring.

4. A product pump for a metering appliance, and especially for a metering appliance with fluid drive according to any one of claims 1 to 3, the product pump having a piston designed to move to and fro in a chamber in a housing, the piston being positioned on a piston rod connected to a drive and dividing the chamber into a front and a rear piston displacement area, the front piston displacement area being connected to a feeding pipe which is fitted with a suction valve and via an outlet orifice with a pipe for the product fitted with an outlet valve, and the rear piston displacement area being connected with the front piston displacement area via a transfer port which discharge into the outlet valve into the pipe for the product.

5. A pump, according to claim 4, in which the effective stroke volume in the front piston displacement area is twice as great as the effective stroke volume in the rear piston displacement area.

6. A pump, according to claim 4 or 5, in which the cross-section of the transfer port amounts to at least 50% and preferably 66% of the crosssection of the outlet orifice.

7. A pump, according to one of claims 4 to 6, in which the housing on the piston rod is constructed so as to be movable as far as the movable stop for the regulation of the stroke volume.

8. A metering appliance constructed and arranged substantially as herein described with reference to the accompanying drawings.

9. A product pump constructed and arranged substantially as herein described with reference to the accompanying drawings.