US3028876A - Device for controlled slow-rate continuous fluid-flow - Google Patents

Description

A ril 10, 1962 J. L. GRA'I'ZMULLER 3,028,876

DEVICE FOR CONTROLLED SLOW-RATE com'muous FLUID-FLOW 2 Sheets-Sheet 1 Filed June 3, 1960 F m m IN 4 2 u m A 2 9 v 5 April 10, 1962 J. 1.. GRATZMULLER 3,028,876

DEVICE FOR CONTROLLED swwmus CONTINUOUS FLUID-FLOW 2 Sheets-Sheet 2 Filed June 5, 1960 Q aHu E v 96H... 2 v A 0 Q h r a A a o w W m m m 1 Aw Ai 8 for United States Patent ()fifice 3,028,876 DEVICE FOR CONTROLLED SLOW-RATE CONTINUOUS FLUID-FLOW Jean Louis Gratzmuller, 66 Blvd. Maurice Barres, Neuilly-sunSeine, France Filed June 3, 1960, Ser. No. 33,835 Claims priority, application France June 11, 1959 2 Claims. (Cl. 137-501) This invention relates to apparatus for ensuring a continuous, uniform flow of fluid at a slow rate from a source under pressure into an enclosed receiver at a considerably lower pressure than the source.

One contemplated application of such apparatus is to maintain in the enclosed receiver a constant atmosphere of dry air, for example for protecting the hollow porcelain insulators and electrically live working parts of a high tension circuit breaker against the damaging and poten tially dangerous effects of humidity, for which purpose complete reliability in the maintenance of the dry atmosphere is essential.

Another contemplated application is the maintenance in an enclosed receiver of a constant pressure, which can be used as a reference pressure in a fluid-circulating system.

In order to keep the average flow-rate from the source to the receiver at a low value, a flow-rate limiting device is necessary. Means must also be provided for establishing the required pressure-drop from the source to the receiver.

One possible means of obtaining the required pressure drop and at the same time limiting the flow-rate to a small value is to use a restrictor in the form of a capillary tube.

By a capillary tube in the present context is meant a tube of very small internal cross-section composed with its length, such that the flow through it is laminar throughout.

Such capillary tubes, unless of inordinate and unacceptable length, have the disadvantage that they are of such small bore so as to require the use of a filter which will only allow particles of microscopic size to reach the tube, such filters being complex and expensive; and even so it is the general experience that, sooner or later, the capillary tube becomes choked; and if the apparatus is to work safely without constant attention, this circumstance is to be avoided at all costs.

An object of this invention is an apparatus of the kind first herein mentioned, in which the use as a flow-limiting and pressure-reducing device, of a capillary tube or tubes is avoided.

The use of an ordinary, non-capillary restrictor alone is, however, in most of the contemplated applications, economically unacceptable, since the flow-rate through such a restrictor produced by the total pressure-drop between the source and the receiver will usually be much greater than the mean flow-rate demanded by the installation. Consequently, the pressure source, such as a compressor, will need to have a much greater capacity than is necessary. For instance, if a mean flow-rate to the receiver of 1 m. /hr. is called for and the total pressuredrop will cause a flow-rate through the restrictor of m. /hr., the pressure source will have to have ten times the delivery capacity that is really necessary, even if it is only required to operate intermittently. Moreover, although a filter of coarser character than is required for a capillarytube may be used, its capacity must correspond to the total volume of fluid passed through it per minute at the maximum flow-rate and if the latter is much greater than the average flow-rate demanded by the installation, a filter of much greater capacity than is actually necessary must be used.

A further object of the invention is the combination, in

i n tented Apr. 10, 1962 the conduit connecting the source and the receiver of a restrictor having a fluid passage of larger dimensions than that of a capillary tube, as above defined, with valve means controlling the fluid flow responsively to the pressure-diiference across the restrictor and a filter upstream of the restrictor, which filter need not have the superfiltering characteristics required for protecting a capillary tube and may be of a capacity corresponding to the mean fluid flow-rate demanded by the installation.

The nature of the invention and how it may be performed will be better understood from the following description with reference to the accompanying drawingsof two embodiments of the invention and including a modication, given by way of example only and without implied limitation of the scope of the invention, which is defined in the appended claims.

In the drawings,

FIGURE 1 is a schematic sectional elevation of the first embodiment,

FIGURE 1a is a detail view corresponding to a part of FIG. 1 and illustrating a modification, and

FIGURE 2 is a similar view of the second embodiment.

Referring to FIGURE 1, the apparatus comprises a source of fluid under pressure diagrammatically represented at 1 and an enclosed receiver of the fluid diagrammatically represented at 2. The source 1 and receiver 2 are connected by a conduit system comprising a conduit 3 extending from the source 1 and including a filter 4, a chamber generally indicated at 5 containing a pressurereducing valve and a conduit 6 leading from the chamber 5 to the receiver 2 and including a restrictor 7 whose fluid passage is of larger dimensions than those of a capillary tube as hereinbefore defined. The pressure-reducing valve comprises the following elements, viz. a ball 13 seatable on a setting communicating with the conduit 6 and trapped by a cotter 17, a chamber sub-divided into two compartments 8 and 9 by a flexible diaphragm 10 and a push rod 14 secured to the diaphragm 10 by two plates 15 and 16, between which the central part of the diaphragm is gripped. The ball 13 is seatable by the pressure in the conduit 3 downstream of the filter 4 and by gravity, and is unseatable by the push rod 14 when the latter is moved upwards. The compartment 8 communicates, by means of a pipe 11, with the conduit 6 downstream of the restrictor 7 and the compartment 9 communicates, by means of a gallery 12, with the conduit 6 upstream of the restrictor 7. The compartment 8 contains a spring 18 which acts on the diaphragm 10 and push rod 14 in the direction to unseat the ball 13.

The apparatus operates as follows:

Initially, that is before any flow through the conduit 6 takes place, the pressure in this conduit on either side of the restrictor 7 are equal, and consequently the pressures in the compartments 8 and 9 are likewise equal. In this condition the spring 18 raises the diaphragm 10 and push rod 14 and unseats the ball 13. Fluid delivered by the source 1 through the conduit 3 and filter 4 therefore flows through the seating of the ball 13 into the conduit 6 and flows through the restrictor 7 into the receiver 2. The restrictor 7 limits the rate of flow through it and at the same time causes the pressure in the conduit 6 upstream of the restrictor to build up above that subsisting downstream of the restrictor which is substantially the pressure subsisting in the receiver 2. The pressure in the conduit 6 upstream of the restrictor is transmitted to the gallery 12 by the compartment 9 and that in the conduit 6 downstream of the restrictor is transmitted by pipe 11 to the compartment 8. When the excess of pressure in compartment 9 over that in compartment 3 reaches a predetermined value, depending on the rating of the spring 18, the diaphragm 10 is pressed downwards and withdraws the push rod 14 allowing the bdl 13 to be seated. This stops the flow of fluid into the conduit 6 and thereupon pressures in this conduit on either side of the restrictor 7 tend to come into equilibrium, but as soon as the pressure difierence across the restrictor 7, and consequently the excess of pressure in compartment 9 over that in compartment 8 has fallen to the above-mentioned predetermined value, the spring 18 again raises the diaphragm 1i and push rod 14 and unseats the ball 13. The process then repeats itself.

It will be evident from this that the pressure difierence across the restrictor 7 can never rise above the above-mentioned predetermined value and the spring 18 is so calibrated that this predetermined value of pressure difference is very much less than the pressure difference between the source 1 and the receiver 2. The spring 18 is further so calibrated that the predetermined pressure difference established across the restrictor 7 is such that the latter limits the flow-rate through it to that demanded by the receiver 2.

It must further be emphasized that the characteristics of the filter 4 are so selected that they will not allow particles to pass it of a size capable of choking the restrictor 7, but it is not necessary that the filter 4 should be capable of stopping particles of much smaller size that would easily pass through the restrictor 7.

The apparatus illustrated in FIGURE 1 may advantageously be modified as illustrated in FIGURE 1a, by introducing a secondary filter 2% in the run of the conduit 6 between the seating of ball 13 and the restrictor 7 of such character that it will not arrest particles that have passed through the filter 4. The purpose of this secondary filter is not to arrest foreign matter derived from the source 1, this being the function of the filter 4, but merely to arrest any particles of a size capable of choking the restrictor 7 which may be derived from the pressure-reducing valve, for instance by abrasion of the seating of the ball 13.

Referring now to FIGURE 2, in which elements common to FIGURES 1 and 2 are designated by the same reference characters as in FIGURE 1, the apparatus comprises a source 1 of fluid under pressure, a receiver 2 of such fluid, a conduit 3 extending from source 1 and containing a filter 4 of similar character to the corresponding filter of FIGURE 1, a non-capillary restrictor 7 and a conduit 6 leading to the receiver 2.

In this embodiment the restrictor 7 is located in the run of conduit 3 downstream of filter 4 and the pressure-reducing valve generally indicated by a is disposed between conduit 3 and conduit 6, i.e. downstream of restrictor 7. It comprises a casing partitioned by a flexible diaphragm into two compartments or chambers, of which chamber 8 communicates via a pipe 11 with conduit 3 at a point between the filter 4 and the restrictor 7, and in chamber 9 is a valve seating communicating with conduit 6 and seatable on which is a disc valve member 13a secured to a holder 19 fixed to the center of the diaphragm 10 by a pair of gripping plates, similar to plates 15, 16 of FIGURE 1.

This apparatus operates as follows:

Before any pressure is applied to the conduit 3, the spring 18 will unseat the valve member 13a and consequently the pressures in chambers 8 and 9 will be equalised at the value of the pressure in the receiver 2. As soon as supply of fluid from the source 1 begins, the pressure transmitted through the filter 4, conduit 3 and pipe 11 to the chamber 8 will immediately rise to nearly the value of the source pressure, and the excess of pressure in chamber 8 over that in chamber 9 will overcome the eifort of spring 18 and seat the valve member 13a and seal the chamber 9 against outflow of fluid; but since the pressure in chamber 9 will initially be that of the receiver 2, the restrictor 7 will be subjected to a pressure-difference nearly as great as to total pressure difference between the source 1 and receiver 2, and

consequently there will be a rapid flow of fluid through the restrictor into chamber 9 to begin with. However, as the fluid cannot, at this stage, flow out of the chamber 9, the pressure in that chamber will build up rapidly until it reaches a value, such that the effort of spring 18 will just overcome the excess of pressure in chamber 8 over that in chamber 9 and unseat the valve member 13a, thus allowing fluid to flow from chamber 9, through conduit 6 into the receiver 2. By this time the flowrate through restrictor 7 will have fallen to the value corresponding to the pressure-difference between chambers 8 and 9; and the spring 18 is so calibrated that this (reduced) flow-rate corresponds to that demanded by the receiver 2. This flow-rate can only be exceeded momentarily, since any increase of flow-rate will re quire a greater pressure-difference across the restrictor 7 and hence an excess of pressure in chamber 8 over that in chamber 9 suflicient to overcome the effort of spring 18 and cause the valve member 13a to be reseated. Hence, the valve member 1311 controlled by the pressure-difference across the diaphragm 10 and by the spring I8 limits the flow-rate through the restrictor 7 and the conduit 6 into the receiver 2 to the predetermined required value.

Evidently, in the embodiment of FIGURE 2, the introduction of a second stage of filtration downstream of the valve seating, as in the modified form of the embodiment of FIGURE 1, illustrated in FIGURE 1a, will in no case be needed, since there is no restrictor in the conduit 6 between the valve seating and the receiver.

When the fluid to be handled by the apparatus of the invention is a gas, which is compressible, as distinct from liquids, which, in general, are only very slightly compressible, the embodiment of FIGURE 1 has an advantage over that of FIGURE 2 in that the mean pressure of the fluid within the restrictor 7 approximates more closely to that of the receiver than to that of the source, whereas the opposite is the case with the embodiment of FIGURE 2; and since in the case of a gas the density will be proportional to the pressure (at a given temperature) the mass flow-rate through the restrictor 7 will, other things being equal, be less in the embodiment of FIGURE 1 than in that of FIGURE 2; and conversely, for a given mass flow-rate, the embodiment of FIGURE 1 will not require a restrictor of such small bore as will the embodiment of FIGURE 2.

Typical dimensions of the restrictor 7 of an embodiment as shown in FIGURE 1 or FIGURE 2, for a given installation might be as follows:

Length m./m 1 Diameter of bore m./m 0.5

A capillary tube giving the same mass flow-rate for the same total pressure-difference between the source and the receiver (with-out a pressure-reducing device) would have to have approximately the following dimensions:

Length m 1 to 1.50 Diameter of bore m./m.. 0.2

For a different installation the comparative dimensions of the restrictor 7 and an equivalent capillary tube (without pressure-reducing device) would be of the same general order.

The application of the invention to the maintenance of an atmosphere of dry air in the working chamber of a high-tension circuit breaker has already been mentioned and needs no further explanation.

In another possible application, the receiver 2 may constitute an air-space of a fluid-feeding device, in which it is required to maintain a constant pressure above atmospheric, e.g. for facilitating the circulation by a pump of such fluid in a closed circuit.

It will be understood that the invention is not limited to the embodiments illustrated in and described with reference to the accompanying drawings, but is susceptible of all such variations and modifications as are within the competence of those skilled in the art and are within the scope of the invention as defined in the appended claims; and in particular, that the nature of the source of fluid under pressure and of the receiver of such fluid and the nature of the fluid to be handled are in no way circumscribed.

What is claimed is: a

1. Fluid-flow apparatus comprising a source of fluid such as dry air, under pressure, a receiver of such fluid under lower pressure than that of said source, a conduit connecting said source to said receiver, such conduit including, disposed in the following order from source to receiver, a filter element, a valve chamber, a valve seating, a second filter element, said second filter element being of such nature as not to arrest particles small enough to have passed through the first-mentioned filter element, and a restrictor, whose fluid passage is of larger dimensions than that of a capillary tube as herein defined; a ball seatable on said seating, a chamber, a flexible diaphragm partitioning said chamber into two compartments communicating with said conduit downstream of said seating, the first of such compartments communicating with the conduit upstream of the restrictor and the second compartment communicating with the conduit downstream of the restrictor, a push-rod attached to said diaphragm and adapted to unseat said ball when said diaphragm is displaced towards said first compartment, and a spring operative on said diaphragm to displace it towards said first compartment,

2. Apparatus for ensuring a small flow of fluid, such as dry air, from a source under pressure to an enclosed receiver under considerably lower pressure than said source comprising conduit means interconnecting said source and said receiver, a restrictor device in said conduit means having at least one fluid-restricting passage, the dimensions of which are greater than those of a capillary tube as herein defined, seatable valve means in said conduit means for blocking and unblocking the latter, means for seating and unseating said valve means comprising a movable Wall, means connecting opposite sides of said Wall to the pressures subsisting up-and downstream respectively of said restrictor device in suchwise that the pressure downstream of the restrictor device tends to unseat the valve member and conversely, a filter in said conduit means between said source and said valve means, and which includes a second filter disposed between said valve means and said restrictor device, said second filter being incapable of arresting particles which have passed through said first-mentioned filter.

References Cited in the file of this patent UNITED STATES PATENTS 1,787,686 Kerr Jan. 6, 1931 2,516,333 Moore July 25, 1950 2,915,084 Taylor et a1. Dec. 1, 1959 FOREIGN PATENTS 1,062,438 France Apr. 23, 1954

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