GB2070201A - Flow divider - Google Patents

Abstract

The invention relates to a flow divider of the type comprising an inlet 11 for a primary flow, two outlets 21, 22 for secondary flows, two chambers 8, 9, two first conduits 19, 20 connecting said chambers to the inlet, a floating piston valve 3 with two faces situated opposite the edges separating the inner chambers from the outlets, and defining a first restriction between the said faces and edges, and two second restrictions situated on the said first conduits in which each second restriction is made pressure responsive so that the flow cross- section varies in the same direction as, and in correspondence with a variation of the said primary flow. To this end, a spring pressed slide 13 having a set of apertures 52 coacting with a flow groove A and a set of apertures 54 coacting with a flow groove 18 is provided. <IMAGE>

Description

SPECIFICATION Flow divider The application of pressurized fluids, such as in particular in hydraulic engineering, have led to the production of flow dividers, for dividing a primary flow into two secondary flows whose values are within a predetermined ratio and whose sum is equal to the said primary flow.

According to the known techniques, a flow divider is constituted by a divider body, inside a bore of which is floatingly mounted a slide valve whose opposite ends define two variable restrictions situated on two separate conduits connecting the intake to the two fluid exhausts. On these two conduits, and between the intake and the two first restrictions mentioned, are provided two second restrictions of constant value.

It has been noted that, if two such second constant restrictions are adopted, the functioning is only satisfactory when its characteristics, and in particular the value of the primary flow, are approaching the theoretical value adopted to calculate the dimensions of the flow divider. Immediately one departs from the aforesaid special characteristics, the functioning becomes defective.For example: when the primary flow is less than the theoretical flow, the responsiveness of the divider worsens and the division ratio varies uncontrollably and undesirably, -when on the contrary, the primary flow is greater than the theoretical flow, the responsiveness is preserved and the division ratio is obtained, but the drops in pressure and the rise in the temperature of the fluid increase considerably, and the low output obtained makes the divider unserviceable.

The invention step has been to design second restrictions of varying values, whose characteristics are adaptable with respect to the value of the primary flow.

The invention therefore relates to a flow divider constituted by: -a body, -a fluid inlet through which flows a primary flow of fluid to be divided, -two outlets for two secondary flows resulting from the division of the primary flow, -two inner chambers provided in the body, -two first conduits, each connecting an inner chamber to the inlet; -two second conduits each connecting an inner chamber to an outlet;; -a floating slide-valve provided, with two separate first faces, each one facing the dividing edge between an inner chamber and the corresponding second conduit, and being at a varying distance of the said edge, so as to define a first restriction of variable cross-section between the said first face and edge, and, with two axial second faces oriented in opposite directions and each one communicating with an inner chamber, and, -two second restrictions, one on one of the said first conduits, the other on the other first conduit.

Each one of the second restrictions is provided with means for adjusting its value, said means causing the flowing section to vary in the same direction as, and in correspondence with a variation of the said primary flow.

Advantageously, the following arrangements are also adopted: each one of the second restrictions is constituted by a slide valve which: is mounted for sliding in tight manner inside a bore of the body of the flow divider, each one of the said first conduits issuing into the said bore via a fixed orifice, is coupled to a position return spring, whilst being subjected to the antagonistic pressures of the said return spring and to the pressure of the fluid flowing through the inlet, and, is provided with at least one connecting.

conduit which issues on its periphery via a movable orifice adapted, on the one hand, to be concealed by the wall of the bore, and on the other hand, once the slide valve has moved under the preponderent effect of the pressure of the fluid flowing through the inlet, to be at least partly superimposed on the said fixed orifice; -the connecting conduit relative to the two second restrictions are provided in a single slide valve; roach slide valve comprises an axial recess which is in permanent communication with the inlet, whereas the connecting conduit relative to each second restriction is constituted by at least one hole traversing radially the wall of the said recess;; The connecting conduits relative to the two second restrictions are constituted by two series of identical through holes, the holes of one series being centred in the same transverse plane perpendicular to the axis of the slide, and the two transverse planes relative to the two series of through holes being separate; -the theorectical division ratio is dependent on the ratio of the number of through holes of one series to the number of through holes of the other series; -the fixed orifice relative to each first conduit is constituted by a circular groove provided in the body of the divider and issuing into the said bore; -the two second conduits are joined by an equalizing pipe on which is placed another restriction.

The invention will be more readily understood on reading the following description with reference to the accompanying drawings in which: -Figure 1 is a diagrammatical cross-section of a flow divider according to the invention; -Figure 2 is an axial cross-section of the slide valve producing the two restrictions of the flow divider shown in Fig. 1, in a first configuration of operation; -Figure 3 is a cross-section along Ill-Ill of Fig. 2; -Figure 4 is a cross-section along IV-IV of Fig. 2; --Figure 5 is a view showing a plane development of the slide valve of Fig. 2;; -Figure 6 is an axial cross-section similar to that shown in Fig. 2 of the same slide, but in a second configuration of operation, and -Figure 7 is a plan development, similar to that shown in Fig. 5, of the slide valve of Fig. 6.

The illustrated flow divider comprises: -a body 1, " bore 2 -a piston valve 3, which is mounted for sliding in tight manner inside the bore 2, -two chambers 4 and 5, constituting extensions of the ends of the bore 2, -two elastic return springs 6 and 7, interposed between the bottoms 8 and 9 of the two chambers and the ends of the piston valve 3, holding the latter in a middle position, which springs are guided by cylindrical part 10 integral with the ends of the piston valve which they surround, -an inlet orifice 11 for a primary flow of fluid to be divided, -a bore 12, one end of which is constituted by the inlet 11, -a slide valve 1 3 comprising an intermediate bottom 14, which is cylindrical, tubular, provided with an axial recess 1 5 defined by the intermediate bottom 14 and by an opening 16, and which is mounted for sliding in tight manner inside the bore 12, its opening 1 6 communicating with the part of said bore bounded by the primary flow inlet 11, -two grooves 1 7 and 1 8 provided in the body 1, issuing into the bore 12, -two first conduits 1 9 and 20, connecting the chambers 4 and 5 with the grooves 1 7 and 18, respectively, -two second conduits 21 and 22, issuing on the one hand into grooves 23 and 24 whose edge 25, 26 of one of the sides is adjoining the said chamber 4, 5, respectively, and on the other hand, to the outside of the body 1, via outlets 21a, 22a, -a main connecting pipe 27, -two return conduits 28, 29 connecting the grooves 30, 31 to the said main connecting pipe 27, -two non-retuin valves 32, 33 which, in the closed position, isolate the grooves 23, 24 from the return conduits 28, 29, but on the contrary connect when in the open position, the said grooves with the return conduits, respectively, -a chamber 34, which constitutes the bottom of the bore 12, which chamber contains an elastic return spring 41 for the slide valve 13, and is in permanent communication with the first conduits 1 9, 20 via two conduits 35, 36, called leakage return conduits, on which are placed two restrictions 37, 38, respectively, secondary return conduits 39, 40 connecting the rear faces of the non-return valves 32, 33 to one of the return conduits, in this case the return conduit 28, -an equalizing pipe 42, connecting the second conduits 21 and 22, and -a restriction 43, placed on the said equalizing pipe 42.

The active ends of the piston valve 3 comprise two truncated cone-shaped first faces 44, 45 situated opposite the edges 25, 26 and defining together with the said edges, first restrictions 46, 47 respectively, of values varying in relation to the position of the piston valve 3 inside the bore 2. Said first restrictions create a communication between the chamber 4 and the groove 23 and between the chamber 5 and the groove 24.

These ends of the piston valve 3 also comprise two transverse second faces 48, 49 which are perpendicular to the axis 50 of the piston valve 3 and oriented in opposite directions, whilst being in permanent communication with the chambers 4, 5 respectively.

The constitution of the tubular slide valve 1 3 will now be described in more details, reference being made to this effect to Figs. 2 to 7.

It should first be noted that the cylindrical wall of the slide valve which separates the axial recess 1 5 from the external cylindrical face 51 (sliding in tight manner inside the bore 12) is traversed by two series of identical holes: one series of two holes 52 centred in a transverse plane 53 and diametrically opposed, and one series of four holes 54, of similar diameter as the holes 52 but centred in another transverse plane 55 and angularly set-back by 90 with respect to the axis 56 of the slide valve 1 3.

It is also to be noted that, depending on the value of the primary flow going through the inlet 11, and therefore on the pressure acting on the intermediate bottom 14 of the slide valve 13, the effect of which pressure opposes the action of the return spring 41, the slide valve 1 3 is more or less sunk in the bore 1 2. In this way, two very distinct configura- tions are shown, the first one in Figs. 2 to 5, and the second one in Figs. 6 and 7.

The configuraton shown in Figs. 2 to 5 corresponds to a strong primary flow. The pressure of the fluid acting on the intermediate bottom 14 is relatively high and it is sufficient to partly overcome the return force of the spring 41, thereby permitting a great covering height A by superimposition of the holes 52 and 54, and of the corresponding grooves 17, 1 8. Also to be noted is that the covering of the holes 52 and the groove 1 7 has a value A equal to that of the holes 54 and the groove 1 8. The sections created by the superimposition of the holes 52, 54 and of the grooves 17, 18, respectively, for the flow of the fluid contained in the axial recess 1 5 towards the first conduits 1 9 and 20 are relatively large although they are designed to restrict the flow of said fluid.

The configuration shown in Figs. 6 and 7 corresponds on the contrary, to a small primary flow, which is less than that of the previous case. The pressure acting on the intermediate bottom 14 is less than in the previous case, and the spring 41 has pushed the slide valve 1 3 back towards the inlet 11, thus causing a smaller part of the holes 52 and 54, and of the corresponding grooves 17, 1 8 to be covered than in the previous case.

The height B over which the holes 52 and the groove 1 7 are covered, and which is also the covering height of the holes 54 and of the groove 18, is less than the value A. The sections created by the partial superimposition of the holes 52, 54 on the grooves 17, 18 respectively to restrict the flow of fluid from the recess 1 5 towards the first conduits 1 9 and 20, are small, smaller than the corresponding sections in the previous configuration.

Concerning the resulting functioning, it is noted that the division ratio of the flow rates into the first conduits 1 9 and 20, and which results from the ratio of the sections through which the fluid flows from the axial recess 1 5 towards these two conduits, and which are created by the partial superimposition of the holes 52 and 54 on the grooves 17, 1 8 respectively, is, in this particular case, equal to the ratio of the number of holes (2/4 = 0.5). Said ratio remains constant whatever the value of the primary flow and whatever the pressure acting on the bottom 14, this being a first and primary characteristic.

But what is also very important is that the pressure drops resulting from the fluid flowing through the restrictions formed by the partial superimposition of the holes 52, 54 on the grooves 17, 18, retain permanently acceptable values. Indeed, when the primary flow rate is small, the covering height B is such that the sections of the holes 52 and 54 through which flows the fluid are adapted to the value of that flow rate. The height B is small. When the primary flow rate is strong, the pressure resulting therefrom automatically causes the slide valve to move thus enlarging the said flow sections, to reach a height A greater than B.In view of the return force of the spring 41, of the value of the pressure inside the recess 1 5 and.of the relative positions of the holes 52, 54 with respect to the grooves 17, 18, the variation of the flowing section is such that the drop in pressure is substantially constant in value. In particular, the flow divider is well adapted to the division of high primary flows.

The function of the slide valve 3 is quite a normal one in the technique of flow dividers.

For example, the flows in the second conduits 21, 22 are secondary flows issued from the division of the primary flow of fluid. The division ratio, as we have just seen, is constant and equal to the theoretical ratio corresponding to the definition of the slide valve 1 3. It could however happen that receiving apparatus fed with these secondary flows require to have slightly different supply rates from those going through the second conduits 21, 22. It is precisely to compensate the flow circulating in one of these second conduits with part of the flow in the other second conduit that the equalizing pipe 42 has been provided. Thus, the momentary excess of flow into one of the second conduits can pass through the said equalizing pipe and complete the flow into the other second conduit.It is not of course recommended to re-mix these two secondary flows without taking any precautions, once the primary flow has been accurately divided and once two secondary flows of specific values have been obtained.

For this reason, a restriction 43 has been provided on the equalizing pipe 42, to obstruct the re-mixing of these secondary flows.

As to the non-return valves 32, 33, their function is, on the one hand, when the primary flow to be divided penetrates through the main connecting pipe 27, to prevent the fluid from flowing directly through the return pipes 28, 29 towards the second conduits 21, 22, and on the other hand, when the receiving apparatus connected to the second conduits 21, 22 are reversible and when said second conduits have ceased to convey the supply fluid to the said receiving apparatus, but on the contrary carry the exhaust fluid, to allow these flows of exhaust fluid flowing in through the second conduits 21, 22 towards the grooves 23, 24, to flow freely towards the main connecting pipe 27, and from there towards a non-pressurized discharge tank, by lifting the non-return valves 32, 33 and flowing through the return pipes 28, 29.

The invention is not limited to the description given hereinabove but on the contrary covers any variant that may be brought thereto without departing from the scope or spirit thereof.

Claims (8)

1. Flow divider comprising: -a body, -a fluid inlet through which flows a primary flow of fluid to be divided, -two outlets for two secondary flows resulting from the division of the primary flow, -two inner chambers provided in the body, -two first conduits, each connecting an inner chamber to the inlet, -two second conduits each connecting an inner chamber to an outlet, -a floating slide-valve provided, with two separate first faces, each one facing the dividing edge between an inner chamber and the corresponding second conduit, and being at a varying distance of the said edge, so as to define a first restriction of variable cross-section between the said first face and edge, and, with two axial second faces oriented in opposite directions and each one communicating with an inner chamber, and, -two second restrictions, one on one of the said first conduits, and the other first conduit, characterised in that each one of the second restrictons is provided with means for adjusting its value, said means causing the flowing section to vary in the same direction as, and in correspondence with a variation of the said primary flow.

2. Flow divider as claimed in claim 1, characterised in that each of the two restrictions is constituted by a slide valve which: is mounted for sliding in tight manner inside a bore of the body of the flow divider, each one of the said first conduits issuing into the said bore via a fixed orifice, is coupled to a position return spring, whilst being subjected to the antagonistic pressures of the said return spring and to the pressure of the fluid flowing through the inlet, and, is provided with at least one connecting conduit which issues on its periphery via à movable orifice adapted, on the one hand, to be concealed by the wall of the bore, and on the other hand, once the slide valve has moved under the preponderent effect of the pressure of the fluid flowing through the inlet, to be at least partly superimposed on the said fixed orifice.

3. Flow divider as claimed in claim 2, characterised in that the connecting conduits relative to the two second restrictions are provided in a single slide valve.

4. Flow divider as claimed in any one of claims 2 and 3, characterised in that each slide valve comprises an axial recess which is in permanent communication with the inlet, whereas the connecting conduit relative to each second restriction is constituted by at least one hole traversing radially the wall of the said recess.

5. Flow divider as claimed in claim 4, characterised in that the connecting conduits relative to the two second restrictions are constituted by two series of identical through holes, the holes of one series being centred in the same transverse plane perpendicular to the axis of the slide, and the two transverse planes relative to the two series of through holes being separate.

6. Flow divider as claimed in claim 5, characterised in that the theoretical division ratio is dependent on the ratio of the number of through holes of one series to the number of through holes of the other series.

7. Flow divider as claimed in any one of claims 2 to 6, characterised in that the fixed orifice relative to each first conduit is constituted by a circular groove provided in the body of the divider and issuing into the said bore.

8. Flow divider as claimed in any one of claims 1 to 7, characterised in that the two second conduits are joined by an equalizing pipe on which is placed another restriction.