GB2134487A

GB2134487A - Dosing of fluids

Info

Publication number: GB2134487A
Application number: GB08402901A
Authority: GB
Inventors: Konrad Bergmann
Original assignee: Ideal Standard GmbH
Current assignee: Ideal Standard GmbH
Priority date: 1983-02-04
Filing date: 1984-02-03
Publication date: 1984-08-15
Also published as: FR2544102A1; IT1199558B; IT8446806A1; DE3303778C2; FR2544102B1; JPS59187223A; GB8402901D0; IT8446806A0; GB2134487B; DE3303778A1

Abstract

The compressibility of the fluid to be dosed is utilised, by arranging that a cavity 1 of substantially constant volume and which in use remains filled with the fluid, is first placed in communication with an inlet 2 which supplies fluid at a relatively high pressure P1 so that some of the fluid enters the cavity, and is then isolated from the inlet 1 and is placed in communication with an outlet 3 which is at a lower pressure P2 so that the fluid in the cavity expands and a predetermined precise, small amount flows into the outlet. Several cavities, inlets and outlets may be provided in two or more members, such as ceramics discs, which are relatively movable by oscillation or rotation to provide simultaneous or continuous successive doses. Such devices may be used to distribute doses to several outlets or to mix doses of fluids from different inlets into a common outlet. <IMAGE>

Description

SPECIFICATION Device and method for dosing fluids Dosing of fluids is required in many fields of technology. Examples are chemical engineering, pharmacy, medical engineering and the field of chemical and physical measuring technology.

Dosing pumps are already known which operate according to various displacement principles, whose common drawback lies in intermittent supply. There are also dosing devices with which a constant volume chamber is filled with fluid and, after being isolated from an inlet, is connected to an outlet, into which the contents of the whole chamber flow or are poured. These devices are unsuitable for dosing precise small amounts, since the chamber volumes can not be made smaller at will nor can filling and emptying readily be stopped to provide an accurate smaller dosage than the chamber volume. Dosing can also be carried out with known throttle members, which admit a specific throughflow corresponding in each case to drops in pressure.

Such throttle members however, undergo strong changes in throughflow characteristics if the edges of the throttle become only slightly rounded, be this a result of erosion or contamination. When small volumetric flows and therefore small throttle cross-sections are involved, there is the additional danger of complete closure of the throttle by particles carried in the fluid.

It is the aim of certain embodiments of the invention to provide an inexpensive dosing device, with the aid of which dosing of fluids can be controlled precisely even with very small volumetric flows without susceptibility to contamination, and with which the drawback of any noticeable pulsation or variation in the volumetric flow can be avoided to a large extent in a simple manner.

According to a first aspect of the present invention there is provided a dosing device for fluids comprising means having a cavity, and means for placing the cavity in communication with an inlet and, separately, in communication with an outlet and for isolating the cavity so that it is closed during changeover from communication with the inlet to communication with the outlet.

According to a second aspect, there is provided a dosing device in which the compressibility of the medium to be dosed is exploited in that at least one cavity, which has an approximately constant volume and is, in use, permanently filled with fluid, is adapted to receive a specific amount of fluid under compression to the cavity volume at a relatively high pressure respectively at one or several inlets, and, when the inlet has been completely isolated and when the subsequent connection to one or several outlets at a lower pressure level has been established, to release an amount of the fluid from the compression volume received from the inlet by expansion of the fluid.

The volumetric flow achieved using a device according to the invention can be extremely small in the case of fluids with a low compres sibility. Since the or each cavity is substan tially greater than the volume of expansion, there is practically no susceptibility to contam ination.

In one construction,the or each cacity is provided in a first member and the inlet or inlets and outlet or outlets are provided in one or more other members, relative movement between the first member and the other mem ber or members being possible to effect com munication between the inlet(s) and outlet(s) and the cavity or isolation of the latter. The inlet(s) and outlet(s) may be in the same member. They and the or each cavity conveni ently open at mutually contacting sliding faces of the members, of which at least one may be fixed and the other(s) movable.

Preferably, there are a plurality of cavities, a plurality of inlets and a plurality of outlets, and the arrangement is such that the cavities can be brought into communication with re spective inlets and outlets simultaneously or successively or with each inlet in turn alter nately with each outlet in turn. If several cavities are connected to the inlet and outlet alternatively in time, then a virtually constant dosing can be effected practically without any additional expenditure. The volumetric flow of the dosing device can be adjusted by the frequency with which the cavities are con nected to he inlet and outlet, and by the pressure gradient.

The relative movement between the mem bers may be brought about by linear and/or reciprocal movement of one of the members, or alternatively by rotary movement of one of the members. In the latter case a plurality of cavities may be arranged on a common pitch circle relative to the axis of rotation; a plurality of inlets and outlets may also be arranged on respective similarly centre common pitch cir cles,the various pitch circles not necessarily being of the same diameter. Moreover, in any of the possible constructions the number of cavities need not be the same as or need not be a multiple of the number of inlets and outlets.

According to a developing feature of the invention, the dosing device comprises at least two discs or plates lying close on top of one another, of which one disc or plate is immovable and is provided with apertures forming the inlet(s) and outlet(s), whilst the second disc or plate is arranged on the first disc or plate in such a manner as to be movable in a rotary or oscillating fashion and is provided with the cavity or cavities in the form of one or more chambers open only in the direction of the first disc or plate, which chambers can be connected alternately to the inlet(s) and outlet(s) of the first disc or plate as a result of the arrangement of the second disc or plate to be able to oscillate or move in rotary fashion.

Ceramics are proposed, according to a preferred feature of the invention, for use as the material for the members or discs, such as aluminium oxide, since, when at least the sealing surfaces are made of this material, any undesired, permanent leakage flow from the inlet to the outlet can be almost completely avoided, so that when the cavity does not move, effective blocking of the inlet from the outlet is achieved. For less demanding tasks, other materials such as plastics, can of course be used for the members.

According to a further aspect of the invention, there is provided a method of dosing a fluid using a device comprising means defining a cavity of fixed or variable volume and means for placing the cavity in communication with an inlet and, separately, in communication with an outlet, the method comprising supplying at the inlet the fluid at a pre-determined relatively high pressure and placing the cavity in communication with the inlet, isolating the cavity from the inlet and then placing it in communication with the outlet, the outlet pressure being lower than the pressure at the inlet, whereby a predetermined amount of fluid will pass into the outlet upon expansion of the fluid in the cavity.

Where the device has a plurality of cavities, a plurality of inlets and a plurality of outlets, the cavities may be brought into communication with respective inlets and outlets simultaneously or succesively; or with each inlet in turn alternately with each outlet in turn, whereby a plurality of dosed amounts are produced simultaneously, periodically or continuously.

The invention may be put into practice in many ways but various specific embodiments will now be described by way of example with reference to the drawings, in which: Figures la to id show, in various conditions, a dosing device in accordance with the invention with two discs or other plate-like members, of which the upper is movable in oscillating fashion; Figure 2 shows a further dosing device in accordance with the invention with two discs, of which the upper is movable in rotary fashion; Figure 3 is a diagrammatic representation of a further dosing device in accordance with the invention having two discs, of which one is moved in rotary fashion, and according to which the transport of the fluid is effected in a radial direction from the outside inwards or vice versa; and Figure 4 is a diagrammatic representation of a further dosing device in accordance with the invention having two discs, of which one is moved in rotary fashion, and according to which the transport of the fluid is effected in a radial direction from the outside inwards or vice versa, and the number of cavities is not the same as nor a multiple of the number of inlets and outlets.

As can be seen from the various views in Fig. 1 showing the members in different relative positions, a cavity 1 of one disc or member is connected alternately with an inlet 2 and an outlet 3 of the other disc, which can be brought about by means of oscillating movements. According to Fig. 1 a, the cavity 1 is already filled with the medium to be dosed which may be a liquid, gas, or a mixture, or such a medium with solids entrained. The fluid in the cavity 1 is at a relatively low pressure P2 at this stage, as will be explained. According to Fig. 1 b the cavity 1 is moved so that it is connected to the inlet 2, which is under a relatively high pressure P1. A defined amount of fluid thereby flows into the cavity 1 in accordance with the compressibility of the fluid from pressure P2 to P1 and the flexible expansion of the cavity 1 if any.The cavity 1 is then closed relative to the inlet 2; this state is shown in Fig. 1 c.

Finally, according to Fig. 1 d, the cavity 1 is connected to the outlet 3 which is at the lower pressure P2, whereupon the fluid previously enclosed in the cavity at pressure P1 expands. The cavity 1 then remains filled, so that only the expansion volume passes into the outlet 3.

According to the embodiment shown in Fig.

2, the cavities 10 are brought into communication with the inlet 1 2 and outlet 13, by rotary movement of an upper disc, alternately to the inlet 1 2 and outlet 1 3 of a lower disc.

In this case, as many cavities 10 as desired, and relatively small cavities, can be provided on a common pitch circle, provided they do not directly inter connect the inlet to the outlet, in accordance with the described method of operation. According to Fig. 2, therefore, the transport of fluid is carried out on a circular path.

According to the diagrammatic representation shown in Fig. 3, the transport of fluid is likewise effected by rotary movements, but also in a radial direction from the outside inwards or vice versa. According to particular requirements, several cavities 20 (eight in this example) can be provided to circulate and several inlets 22 and outlets 23 can be used.

The number of cavities is a multiple of the number of inlets and outlets so that all the inlets communicate with respective cavities simultaneously and likewise all the outlets in their turn.

Fig. 4 shows a further diagrammatic representation, according to which the transport of fluid is again effected by rotary movements, and the number of inlets 32, and outlets 33, is not the same as the number of cavities 30, nor is the number of the latter a multiple of the number of inlets or outlets. It is hereby achieved that all the cavities 30 are connected to the inlets 32 and outlets 33 alternately in time and in succession relative to others of the inlets or outlets. For n inlets or outlets, and n + 1 cavities, this produces n. (n + 1) individual volumes for each revolution and in the example shown according to Fig. 4, twenty individual volumes.

As indicated in Figs. 3 and 4, the inlets, may, alternatively, be the radically inner apertures and the outlets the radially outer ones.

Separate inlets are conceivable according to the invention, in that simultaneous dosings and mixing of different fluids could be carried out. According to the invention, the outlets can be connected separately to different consumers. Such a design permits even distribution of the supplied fluid to be different consumers.

The shown discs or members consist, or at least their sliding surface consist, of alumi- nium oxide or other ceramics. This material is particularly hard and resistant to wear and the sealing surfaces of the discs or members can be manufactured so evenly and smoothly that practically no leakages can occur.

The described and shown embodiments are only examples for realising the invention, and the latter is not limited to them. There are further possible embodiments in respect of arrangement and design of the cavities and of the inlets and outlets within the basic concept of the invention. In this context, a dosing device with three discs is also conceivable, of which the movable middle disc would be provided with cavities in the form of apertures, whilst the two outer discs could comprise the inlets or respectively the outlets.

In all embodiments, it is of course, necessary to ensure that the device is primed, that the cavities are each completely filled with fluid, before exact dosing can be carried out.

Also, it will be apparent that the shape, size or orientation of the or each cavity must be such that the fluid does not flow out of it when it is connected to the outlet.

In use, the or each movable member may be moved in stepwise fasion or continuously.

Claims

1. A dosing device for fluids comprising means having a cavity, and means for placing the cavity in communication with an inlet and, separately in communication with an outlet and for isolating the cavity so that it is closed during changeover from communication with the inlet to communication with the outlet.

2. A dosing device for fluids, in which the compressibility of the fluid to be dosed is exploited, wherein at least one cavity,which has approximately constant volume and is, in use, permanently filled with the fluid, is adapted to receive a specific amount of fluid under compression to the cavity volume at a relatively high pressure respectively at one or several inlets and, when the inlet has been completely isolated and connection to one or several outlets at a lower pressure level is then established, to release a predetermined amount of the fluid from the compression volume received from the inlet by expansion of the fluid.

3. A device as claimed in claim 1 or claim 2, in which the or each cavity is provided in a first member and the inlet or inlets and outlet or outlets are provided in one or more other members, relative movement between the first member and the other member or members being possible to effect communication between the inlet(s) and outlet(s) and the cavity or isolation of the latter.

4. A device as claimed in claim 3, in which the inlet(s) and outlet(s) are located in the same member.

5. A device as claimed in claim 3 or claim 4, in which the inlet(s), the outlet(s) and the or each cavity open at mutually contacting sliding faces of the members.

6. A device as claimed in any one of claims 3 to 5, in which at least one of the members is fixed and the other(s) movable.

7. A device as claimed in any one of the preceding claims, in which there are a plurality of cavities, a plurality of inlets and a plurality of outlets, and in which the arrangement is such that the cavities can be brought into communication with respective inlets and outlets simultaneously or successively or with each inlet in turn alternately with each outlet in turn.

8. A device as claimed in claim 5 or any claim appendent to claim 5, in which relative movement between the members is caused by linear and/or reciprocal movement of one of the members.

9. A device as claimed in claim 5 or any claim appendant to claim 5, in which relative movement between the members is caused by rotary movement of one of the members.

10. A device as claimed in claim 9, in which a plurality of cavities are arranged on a common pitch circle relative to the axis of rotation of the rotary member, there being a plurality of inlets and outlets on respective similarly centered common pitch circles.

11. A device as claimed in claim 10, in which the common pitch circles for the cavities, the inlets and the outlets are not all of the same diameter.

1 2. A device as claimed in claim 7 or any claim appendant to claim 7, in which the number of cavities is not the same as or is not a multiple of the number of inlets and outlets.

1 3. A device as claimed in claim 3 or in any claim appendant to claim 3, comprising at least two discs lying close one on top of another, of which one disc is fixed and is provided with apertures forming the inlet(s) and outlet(s), whilst the second disc is arranged on the first disc so as to be movable in a rotary fashion or so as to oscillate, and is provided with the cavity or cavities in the form of one or more chambers open only towards the first disc, which chamber(s) can be connected alternately to the inlet(s) and outlet(s) of the first disc due to the arrangement of the second disc such as to be movable in rotary or oscillating fashion.

1 4. A device as claimed in claim 3 or in any other claim appendant to claim 3, in which the members are made of ceramic material.

1 5. A dosing device substantially as specifically described herein with reference to any one of the embodiments as illustrated.

1 6. A method of dosing a fluid using a device comprising means defining a cavity of fixed or variable volume and means for placing the cavity in communication with an inlet and, separately, in communication with an outlet, the method comprising supplying at the inlet the fluid at a pre-determined relatively high pressure and placing the cavity in communication with the inlet, isolating the cavity from the inlet and then placing it in communication with the outlet, the outlet pressure being lower than the pressure at the inlet, whereby a predetermined amount of fluid will pass into the outlet upon expansion of the fluid in the cavity.

17. A method as claimed in claim 16, in which the cavity defines a substantially constant volume.

18. A method as claimed in claim 16 or claim 17, in which the fluid is a liquid.

1 9. A method as claimed in any one of claims 1 6 to 18, in which the device has a plurality of cavities, a plurality of inlets and a plurality of outlets, and wherein the cavities ae brought into communication with respective inlets and outlets simultaneously or successively, or with each inlet in turn alternately with each outlet in turn, whereby a plurality of dosed amounts are produced simultaneously, periodically or continuously.

20. A method as claimed in any one of claims 1 6 to 19, in which the fluid or different fluids is/are dosed from more than one inlet to a common outlet, or fluid from an inlet is dosed to different outlets for distribution to different consumers.

21. A method of dosing fluid, substantially as specifically described herein with reference to any one of the illustrated embodiments.