GB2059019A - A valve - Google Patents

Abstract

A valve ball 10 is movable between two valve seats 16, 18. A ram 15 operated by a solenoid is provided for controlling the pressing of the valve ball 10 against the seat 16. The ball valve 10 is adapted to be urged by liquid pressure into sealing abutment with the second valve seat 18 and when in sealing abutment with a seat ring 17 is also supported by a second abutment which as shown may be provided by the end 19 of the ram. By use of the additional support the seat diameter may be made larger in relation to the ram cross section. A return spring 28 may be applied to the ball. <IMAGE>

Description

SPECIFICATION A valve The invention relates to a valve, particularly but not exclusively an electromagnetically operated valve, having a housing, a valve ball movable between two valve seats in the housing, wherein when the valve ball sits on the first valve seat a connection between a liquid pressure line and a consumer is closed and between the consumer and an outlet is opened and wherein when the valve ball sits on the second valve seat the connection between the pressure line and consumer is opened, the valve ball being adapted to be urged into sealing abutment with a seat ring of the second valve seat by liquid pressure, an axially movable operating ram for pressing the valve ball and sealingly against the first valve seat.

Valves of the above-mentioned type are known, for example, from German Offenlegungsschrift 21 24 484, and are, generally considered, characterised by high functional efficiency so long as the switching speeds demanded are not too high. However, if very high switching speeds are demanded, this dictates appropriately small moving masses in order to keep the operating forces small, with the result that both the valve ball diameter and the diameter of the operating ram have to be kept very small. Such a reduction necessarily means a reduction in the flow cross-sections, so that valves of this type are then suitable only for comparatively small flow rates. Such small flow rates are necessary only when these valves are used as pilot valves, and a preferred application for valves of this type is accordingly that as pilot valves for logistors in fluid logic circuits.However, the latter in turn permit such short switching times as to render minimum ball diameter and minimum diameter of the operating ram necessary in order to keep the operating forces small. However, if the diameter of the valve ball is reduced, e.g., to 2 mm, then a corresponding reduction in the diameter of the operating ram is necessary in order to obtain the necessary free cross-section for the outlet path, because the ram engages the valve ball within the seat ring of the second valve seat which opens the outlet, and the seat ring of this second valve seat must have a considerably reduced cross-section compared with the ball diameter in order not to be knocked too rapidly by the ball.However, such a reduction in the diameter of the operating ram in turn renders the latter so sensitive to stresses, particularly flexural forces, that it becomes impossible to exert sufficient control on the forces occurring particularly at high switching speeds.

The invention now proposes to disclose a solution whereby it is possible to realise sufficiently large flow cross-sections on the outlet side even for a very small ball diameter.

According to the present invention there is provided a valve, including a housing, a valve ball movable between two valve seats in the housing, wherein the valve ball sits on the first valve seat a connection between a pressure line and a consumer is closed and between the consumer and an outlet is opened and wherein when the valve ball sits on the second valve seat the connection between the pressure line and consumer is opened, the valve ball being adapted to be urged into sealing abutment with a seat ring of the second valve seat by liquid pressure, and an axially movable operating ram for controlling the pressing of the valve ball sealingly against the first valve seat, wherein the valve ball when in sealing abutment against the seat ring of the second valve seat is braced against a second abutment independent of the seat ring and offset towards the operating ram from the seat ring.

By this means it is possible to enlarge the second valve seat in its free cross-section to a cross-section largely corresponding to the ball diameter, because the second valve seat as such now has substantially only a sealing function, but not a supporting function. Moreover, the enlargement of the free cross-section of the second seat ring simultaneously makes it possible either to construct the operating ram correspondingly stronger or else, when is a preferred solution according to the invention, to provide a guide extending almost up to its terminal region, in which case the outlet path is formed by an annular channel lying between the second valve seat and the second abutment.

Practical trails have revealed that the double bracing of the valve ball provided according to the invention gives satisfactory sealing even in long-term service, and that no knocking or hammering of the second valve seat occurs. It has also been discovered in the context of practical trials that a valve designed according to the invention is suitable for both high pressure and low presure. Nevertheless, for use with low pressure it may be convenient to additionally load the valve ball resiliently towards the second valve seat.A cup spring constructed as a return spring, which is braced in the housing coaxially with the valve seats, preferably adjacent to the first valve seat, and is provided with a central ball cavity which is smaller than the valve ball diameter and greater than the internal diameter of the first valve, and also with flow orifices, has been found particularly suitable for this purpose. These flow orifices are preferably formed by radially oriented slits. According to the invention the said cup spring is preferably braced loosely, i.e., not clamped rigidly, in the housing. The said spring ensures, even when the said valve is used in low-pressure systems, that the desired high switching speeds can be obtained in spite of the weaker hydraulic forces compared to high-pressure systems.

As a further development of the invention the second abutment may be formed by the operating ram itself, which is guided at least in its terminal region near the ball and is itself, in the bracing position, braced axially unyieldingly against the valve housing. With a construction of this type, despite the additional use of the operating ram as a bracing element, a very slender construction of the operating ram compared to the ball diameter is possible, because buckling of the operating ram is prevented by the guide.In conjunction with this slender construction of the operating ram, comparatively large free outlet paths are then again obtained when the valve ball is pressed against the first valve seat by the operating ram, because only the operating ram dips into the cross-sectional region located in the region of the seat ring of the second valve seat, which is critical for the outlet cross-section.

Another possible further development according to the invention is that the second abutment is formed by a part integral with the housing. This part integral with the housing is conveniently formed by the guide of the operating ram, so that in this respect substantially the same advantages are obtained as by the solution in which the bracing occurs against the operating ram. In this case the second abutment is conveniently formed by a second annular seat surface, which may be formed for example by the bevelled rim of the guide of the operating ram.

In high-pressure systems particularly, and in conjunction with the desired high switching forces, comparatively high operating forces still have to be exerted in forcing the valve ball way from the seat ring of the second valve seat, and it is found convenient in this respect if the second annular seat surface forming the abutment has an internal diameter which is greater radially than the diameter of the guide of the operating ram, and if the operating ram is located at an axial distance from the ball when the ball is in abutment against this second annular seat surface.In this way a liquid cushion is created between the ball and the operating ram which is guided practically fluid-tightly in its guide, of which (cushion) the cross-sectional area bounded by the second annular seat surface is greater than the cross-sectional area of the operating ram, so that a hydraulic force transmission ratio is obtained which, referred to the operating force of the operating ram, results in an intensified operating force on the ball, so that the latter can be lifted out of its position on the seat ring of the second valve seat by comparatively weak control forces at the operating ram.

In another embodiment of the invention the valve ball is braced against the second abutment by a support ball, whilst this second ball is conveniently of smaller diameter than the valve ball which, particularly for very small nominal widths, results in a large nominal width in relation to the ball mass and favourable discharge conditions.

Because the second valve seat can have its free cross-section enlarged to a cross-section largely corresponding to the ball diameter, the ball abuts the second valve seat with an annular zone adjacent to its equator, whilst the annular zone preferably lies in the region of the tenth degree of latitude of the ball.

Because the second valve seat has essentially a sealing function, it is also possible for it to be elastically yielding to a small degree, i.e., practically of virtually knife-edge construction, whilst this second valve seat may optionally also be formed by a corresponding resilient annular disc.

It is also possible from the production standpoint to associate a guide tube with the valve ball and to machine an annular bead into this guide tube as a second valve seat.

This results in a simpler construction for production purposes.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows schematically a known logistor in conjunction with a valve according to the invention as a pilot valve, Figure 2 shows a larger scale view of the pilot valve in a first embodiment, in which the valve ball when in sealing abutment against the seat ring of the second valve seat is braced against a second abutment independent thereof and formed by the operating ram, Figure 3 shows a second embodiment of the pilot valve, in which the second abutment is formed by the guide for the operating ram, Figure 4 shows a third embodiment corresponding in principle to Fig. 3, in which the guide for the operating ram is formed by an inserted tubular sleeve, Figure 5 shows a fourth embodiment, in which a support ball, the diameter of which is smaller than that of the valve ball, is arranged between valve ball and operating ram, and Figure 6 shows a fifth embodiment, in which a liquid cushion is provided between operating ram and valve ball or support ball when the valve ball-or an interposed support ball, if any-is braced against the second abutment.

In Fig. 1, 1 designates a logistor, theconstruction of which corresponds in principle to the prior art, as shown, for example in German Patent 20 04 567. The logistor 1 is located in a housing 2, only schematically indicated here, with which fluid supply connection are associated, the connection to a fluid pressure source being designated 3 and the connection leading to a consumer is designated 4.

The logistor 1 has a switch element in the form of a ball 5, which is movable by hydraulic forces in a guide 1 3 between two switching positions. In the position shown in Fig. 1 the ball 5 abuts against a valve seat 6 and interrupts the connection between the pressure source and the consumer. In this position of the ball 5, it is loaded towards the valve seat 6 by pressure medium derived from a pressure chamber 7 of the logistor through a supply pipe 8 and a control pipe 9. The connection to the control pipe 9 from the supply pipe 8 can be shut off by a valve ball 10 of a pilot valve 11. The connection between supply pipe 8 and control pipe 9 is open in the illustrated position of the valve ball 10, and accordingly, as explained, the ball 5 of the logistor 1 is loaded by pressure towards the valve seat 6.The control pipe 9 issues into an antechamber 12, with a second valve seat 14 of the ball 5 is associated at one end of the guide 1 3.

When, by switching over the pilot valve 11, the connection between supply pipe 8 and control pipe 9 is interrupted, the ball 5 is displaced towards the valve seat 14 due to the pressure loading in the pressure chamber 7, whereby the connection to the consumer is opened.

To switch the pilot valve, an operating element (not shown), such as a solenoid, is provided, by which the operating ram 1 5 can be moved linearly. When the said solenoid comprising the operating element and control member is excited, the operating ram 1 5 is moved towards the valve ball 10, and the valve ball 10 is pressed against a first valve seat 1 6 blocking the connection between supply pipe 8 and control pipe 9. This blocking position is maintained as long as the excitation of the solenoid is maintained.In this blocking position of the ball, a connection between the control pipe 9 and an outlet pipe (not shown), which leads to a fluid reservoir, is opened, and by this means, as previously explained, the ball 5 of the logistor 1 can be moved towards its valve seat 14 under the influence of the hydraulic forces in the pressure chamber 7 of the logistor. When the operating element, i.e., the solenoid, is released, the loading of the valve ball 10 by the operating rod 1 5 is cancelled, and the valve ball 10 is displaced by fluid pressure into the position shown in Fig. 1, in which it interrupts the connection of the control pipe 9 with the outlet, due to the hydraulic forces from the supply pipe 8 which is under pressure due to its connection to the pressure chamber 7 of the logistor.

Applications frequently occur in which the logistor is required to be predominantly open, i.e., the ball 5 rests predominantly in the seat 14. The ball 10 in this case is arranged to have a normal position of rest against the seat 16, and a solenoid is used which when energised, moves the ram 1 5 away from the ball 10. The rest position is maintained by a spring.

In its position blocking the outlet to the reservoir the valve ball 10 is braced in sealing abutment against a second valve seat and additionally aginst a second abutment offset towards the operating ram 1 5. By this means it is possible to position the valve seat comparatively close to the equator of the ball and so, as shown particularly in the following Figs.

to guide the operating ram 1 5 virtually up to its terminal region, in which case the outlet path is formed by an annular channel located between the second valve seat and the second abutment. Practical trials have revealed that the double bracing of the valve ball provided according to the invention provides satisfactory sealing conditions even in long-term service, and that no knocking or hammering of the second valve seat occurs.

Various constructions of the pilot valve 11, which show particularly the type of bracing of the valve ball 10 in its second position blocking the connection to the outlet, are now shown on a larger scale in the following Figs.

2 to 6. As shown in Fig. 2, the valve ball 10 in the construction of the pilot valve 11 according to the invention is an fact braced not only in sealing contact with a seat ring 1 7 of the second valve seat 18, but simultaneously against an abutment offset towards the operating ram 1 5 with reference to the seat ring 17. In the embodiment according to Fig.

2 this abutment 1 9 is formed by the operating ram 15, which is in turn braced by a collar 20, associated with it, against a part of the pilot valve, secured rigidly to, or integral with, the housing 2, here a schematically illustrated plate 21, through which a further section 22 of the operating ram 1 5 passes.

By this bracing of the valve ball 10 against an abutment 1 9 independent of the seat ring 1 7 of the second valve seat 18, it is possible to keep the seat ring 1 7 of the valve seat 1 8 substantially free of forces and accordingly to arrange this seat ring 1 7 in a position relative to the ball 10 near the equator thereof, i.e., approximately in the region of the 1 0th degree of latitude when the valve ball 10 is in sealing abutment. The seat ring 1 7 may also be virtually knife-edged, since it has practically no support function to perform.

Practice has shown that such a solution is both simple to manage from the production standpoint and also satisfactory in long-term service. No hammering of the second valve seat 1 8 occurs. Moreover, the second valve seat 1 8 can also be made so slender that it possesses a certain elastic yielding property, as a result of which it is also possible for the seat to lie on a ring inserted in the housing.

Because the seat ring 1 7 can be place virtually on the equator of the ball 10, a comparatively great axial distance is obtained between the seat ring 10 and the abutment 19, with the result that comparatively large outlet cross-sections can be realised. This is so even if the operating ram 1 5-relative to its position in which it acts as an abutment-is placed within a guide 23 as far as its end, which abuts the ball 10 as illustrated in the embodiment according to Fig. 2.

If the hydraulic system, in which the logistor is included, is a high-pressure system, then the valve ball 10 will also be loaded by correspondingly high pressures. Consequently an immediate movement of the valve ball 10 occurs as soon as it ceases to be retained in its abutment against the first valve seat 1 6 by the operating ram. If the logistor is included in a low-pressure system, then the corresponding hydraulic forces are weaker and in these circumstances it may be desirable to provide a return spring 24 as illustrated in Fig. 2. The return spring 24 according to Fig.

2 is of cup spring-like construction, i.e., a dished washer, and has a central cavity 25 associated with the ball 10. The spring is located movable along its circumference in an annular groove 27 in the pressure chamber 26 located between supply pipe 8 and control pipe 9, and has, in the region between the cavity 25 and its circumference slots which preferably extend radially serving as passage orifices for the hydraulic liquid. These slits are designated 28.

In the embodiment according to Fig. 2 the outlet path is formed adjacently to the seat ring 1 7 of the second valve seat 18 by an annular channel 29 which surrounds the guide 23 and which also has a comparatively great width in its region converging inwards towards the seat ring 17, due to the comparatively great distance between abutment 1 9 and seat ring 17, so that favourable fluid flow conditions exist. The part of the outlet formed by the annular channel 29 is adjoined by a corresponding pipe connection to the reservoir, which is indicated here as a radial bore 30.

The embodiment according to Fig. 3 corresponds in principle to that according to Fig. 2, and accordingly the same references are used again for corresponding parts. Departing from the embodiment according to Fig. 2, however, the abutment 1 9 independent of the seat ring 1 7 of the valve seat 1 8 is here formed not be the operating ram 1 5 per se, but rather by the guide 23 thereof.In this embodiment, when the ball 10 abuts against the second seat ring, the operating ram 1 5 lies within the guide 23 and thus the guide 23 forms a support integral with the housing 2 independently of the operating ram 1 5. The guide is accordingly provided with a bevel corresponding to the diameter of the ball 10 in its rim region associated with the operating ram 1 5.

As may be seen from a comparison of the drawings, otherwise no great differences exist between the embodiment according to Fig. 2 and that according to Fig. 3.

The embodiment illustrated in Fig. 4 again corresponds very largely to that according to Fig. 3, so that the statements made there apply to this embodiment also. Differing from that embodiment however, the guide, here designate 23a, is not formed by a part of the housing itself, but rather by an inserted tubular bushing, which may lead to technical advantages in production, particularly from the standpoint of preferred material selection. This tubular bushing is also provided in the region of the abutment 1 9 with a bevel which is chosen to match the diameter of the valve ball 10.

Fig. 5 shows an embodiment which, whilst having fundamentally the same construction of the pilot valve, operates with a support ball 31 interposed between operating ram 15 and valve ball 10. This support ball 31 is provided with a smaller diameter than the valve ball 10 and lies in an axial bore 32 of the guide 23b for the operating ram 1 5. In the embodiment illustrated, compared to the diameter of the support ball 31 the axial bore 32 has a diameter which is somewhat greater than that of the operating ram 1 5 and the guide bore associated therewith in the guide 23b.Due to the interposition of the support ball 31 particularly large free passage cross-sections are obtained between the seat ring 1 7 of the second valve seat 18 and the annular channel 29, as is clear from the position of support ball 31 and valve ball 10 shown in solid lines.

If, as shown by chain-dotted lines, the valve ball 10 is in sealing abutment against the seat ring 17, then the support ball is preferably braced against the guide 23bwhilst the abutment 1 9 is again formed by a bevelled region of the guide bore for the operating ram 1 5.

However, it is of course also possible in such an embodiment with interposed support ball 31 to brace the latter directly against the operating ram 15, similiarly to the embodiment according to Fig. 2.

In the embodiments described the operating ram 1 5 loads the valve ball 10 directly during switching. At high switching speeds correspondingly high operating forces occur at the operating ram 15, although the latter should advantageously be as slender as possible, firstly in order to keep the mass inertias as low as possible, and secondly in order to enable the outlet cross-sections in the region of the second valve seat to be made as large as possible.

Now to enable the operating forces at the initiation of switching to be kept as low as possible, in the embodiment according to Fig; 6 a construction is chosen in which a liquid cushion is present between the operating ram and the ball, whilst the cross-sectional area of this liquid cushion is greater than the crosssectional area of the operating ram. By this means a transmission ratio is obtained, so that the operating loading on the ram can be kept lower than with direct loading of the valve ball 10 by the operating ram in order to trip the switching movement.

This is achieved structurally in the embodiment according to Fig. 6, in that the abutment 1 9 preceding the seat ring 1 7 of the second valve seat 1 8 in the direction towards the operating ram 1 5 is formed by an annular seat surface associated with the guide 23 of the operating ram 15, the internal diameter of which surface is made greater than the diameter of the operating ram, and which lies at an axial distance from the ball when the ball is in abutment against this second annular seat surface.Because the operating ram 1 5 is guided practically without play, hence substantially also fluid-tightly in the guide 23, and the valve ball 10 is in turn also in sealing abutment with the abutment 1 9 in the described embodiment, when the operating ram 1 5 slides towards the ball 10 the operating force is at first transmitted to the valve ball 10 solely through the pressure cushion, whilst in accordance with the transmission rations resulting from the said surface ratios, the total operating force acting upon the ball 10 is greater than the ram force.

In other respects the construction according to Fig. 6 also corresponds to the embodiments previously described, and it lies within the scope of the invention to provide only an indirect loading of the valve ball 10 by the operating ram 1 5 initially, also in conjunction with guides used accordingly to the embodiments previously described. Such a construction according to Fig. 6 can furthermore also be realised in conjuction with solutions according to Fig. 5, in which a support ball is arranged between valve ball 10 and operating ram 15.

Claims (11)

1. A valve including a housing, a valve ball movable between two valve seats in the housing, wherein when the valve ball sits on the first valve seat a connection between a pressure line and a consumer is closed and between the consumer and an outlet is opened and wherein when the valve ball sits on the second valve seat the connection between the pressure line and consumer is opened, the valve ball being adapted to be urged into sealing abutment with a seat ring of the second valve seat by liquid pressure, and an axially movable operating ram for controlling the pressing of the valve ball sealingly against the first valve seat, wherein the valve ball when in sealing abutment against the seat ring of the second valve seat is braced against a second abutment independent of the seat ring an offset towards the operating ram from the seat ring.

2. A valve according to Claim 1, wherein the second abutment is formed by the operating ram which is guided at least in its terminal region adjacent to the valve ball and is itself, in its bracing position, braced unyieldingly against the valve housing.

3. A valve according to Claim 1, wherein the second abutment is formed by a part secured rigidly to, or integral with, the housing.

4. A valve according to Claim 3, wherein the second abutment is formed by the guide of the operating ram.

5. A valve according to Claim 3 or 4, wherein the second abutment forms a second annular seat surface.

6. A valve according to Claim 5, wherein the second annular seat surface has an internal diameter which is greater than the diameter of the guide of the operating ram and when the valve ball abuts against this second annular seat surface, the operating ram is located at an axial distance from the valve ball.

7. A valve according to any one of Claims 3 to 6, wherein the guide of the operating ram is formed by an insert.

8. A valve according to Claim 7, wherein the insert forming the guide is constructed as a tubular sleeve.

9. A valve according to any one of the preceding claims, wherein the valve ball is adapted to be braced against the second abutment through a support ball.

10. A valve according to any one of the preceding claims, wherein the valve ball has an annular zone adjacent to its equator, which is adapted to abut the second valve seat.

11. A valve according to Claim 10, wherein the ball is adapted to abut the second valve seat approximately in the region of its 10th degree of latitude.

1 2. A valve according to any one of the preceding Claims, wherein the seat ring of the second valve seat is elastically yielding.

1 3. A valve according to any one of the preceding Claims, wherein the seat ring of the second valve seat is formed by an annular bead of a ball guide tube.

1 4. A valve according to any one of the preceding Claims, wherein the seat ring of the second valve seat is associated with an axially firmly clamped plate.

1 5. A valve according to any one of the preceding claims wherein the ram is movable by means of an electro-magnetic solenoid.

1 6. A valve substantially as described herein with reference to, and as illustrated in, any one or more of Fig. 1 to 6 of the accompanying drawings.