GB2311590A

GB2311590A - Venting valve

Info

Publication number: GB2311590A
Application number: GB9705820A
Authority: GB
Inventors: Kurt Stoll
Original assignee: Festo SE and Co KG
Current assignee: Festo SE and Co KG
Priority date: 1996-03-23
Filing date: 1997-03-20
Publication date: 1997-10-01
Also published as: ITVR970023A0; IT1302991B1; DE29605420U1; HU9700585D0; DE19704799B4; ITVR970023A1; HUP9700585A3; GB9705820D0; DE19704799A1; HU220929B1; HUP9700585A2

Description

--A HIGH SPEED VENTING VALVE FOR PNEUMATIC APPLICATIONS- The invention relates to high speed venting valve for pneumatic applications.

The supply of pneumatically powered equipment such as fluid power cylinders or pneumatically operated tools with compressed air is generally performed using rigid or flexible pressure medium lines, which may form part of a compressed air distribution system. In this respect there is sometimes a need for venting the above mentioned pneumatic equipment, for example, when the pressure obtaining in a pressure medium distribution system is reduced using a pressure reducing means. To the knowledge of the applicant such venting has generally so far taken place through a valve on the pressure medium line, which is operated when required. Such a way of working is relatively awkward and, owing to the small discharge flow cross section generally available, leads to delays in the venting operation.

One object of the present invention is accordingly to provide a high speed venting valve which while having a simpler manner of operation renders possible large discharge cross sections.

A high speed venting valve provided by the present invention is characterized by an inlet and an outlet for compressed air, which are connected by a principal flow duct for fluid flow, on which duct a check valve is provided to render possible flow of compressed air from the inlet to the outlet and to prevent return flow of compressed air in the opposite direction, such check valve dividing the principal flow duct into an inlet end duct section subject to the input pressure and an outlet end duct section subject to the output pressure, and furthermore by a venting duct communicating with the outlet end duct section of the principal flow duct, on which venting duct an automatically operated shut off valve is placed, such shut off valve having a shut off valve member able to be switched over between an open venting position permitting flow through the venting duct and a closed shut off position preventing flow through the venting duct, such shut off valve member being functionally connected with two mutually oppositely placed actuating faces, of which one is an actuating face effective in the closing direction and continuously subject to the input pressure and of which other is an actuating face effective in the opening direction and continuously subject to the output pressure so that for the shut off valve member there is a switching position dependent on the pressure ratio between the input pressure and the output pressure.

The invention thus creates an automatic high speed venting valve, which in a manner dependent on the ratio between the input pressure effective at the inlet end and the output pressure effective at the outlet responsible for an automatic switching over of the shut off valve controlling flow along the venting duct. The two actuating faces cooperating with the shut off valve member practically constitute a pressure balance means between he input pressure and the output pressure, a suitable selection of the surface ratio between the two actuating faces being employed to influence the response of the shut off valve. It is convenient for the surface or area ratios to be so selected that the venting duct is closed as long as the input pressure is larger than or equal to the output pressure, whereas when there is a drop in the input pressure below the value of the output pressure, the shut off valve is switched over into the venting position. Owing to the discharge flow of compressed air which then occurs through the venting duct the output pressure goes down, the venting valve being again switched over into the shut off position when a lower limit value is reached. The associated check valve in this case prevents return flow of the compressed air to the inlet so that it may be exclusively discharged through the venting duct. This venting duct may be provided with a large cross section in order to ensure rapid venting.

Further advantageous developments of the invention are defined in the claims.

The actuating faces are preferably at least in part provided on a bendingly flexible sealing diaphragm, which owing to the provision of static seal engagement ensures a reliable sealing action between the shut off valve member and the valve housing without the mobility of the shut off valve member being impaired.

The shut off valve member is preferably designed in the form of a pressure force compensated seat member, it being convenient to additionally provide a mechanical closing spring, which urges the shut off valve member in the shut off direction. It is an advantage if this closing spring also contributes to overcoming friction as may be caused by a seal (which is conveniently annular in shape) arranged between a guide recess in the valve housing and a guide spool, adapted to run in this guide recess, of the shut off valve member.

A particularly compact design is one in which the check valve and the shut off valve are arranged in a common valve housing, which however can be designed in several parts. At the outlet of the venting duct it is then convenient to provide an interface on this valve housing, such interface rendering possible the mounting of a functional unit so that for example an oil trap, a silencer or a spent air duct with a large cross section, through which the discharged compressed air flows, may be connected.

It is more particularly preferred to utilize the high speed venting valve in connection with a so-called medium servicing or conditioning unit, that is to say a device which is employed in compressed air distribution systems to treat the compressed air.

Further details of the invention will be understood from the following detailed descriptive disclosure of one embodiment thereof in conjunction with the accompanying drawings.

Figure 1 shows a preferred design of the high speed venting valve of the invention as a component of a servicing unit serving for treating or preparing compressed air in a longitudinal section.

Figure 2 shows a portion II, as marked in chained lines in figure 1, on a larger scale.

In figure 1 the reader will perceive a medium servicing unit 1, serving for the treatment of compressed air, placed on a compressed air line 2 indicated in chained lines. In the case of the particular embodiment of the medium servicing unit 1 it is a question of a spent air de-oiler, adapted to filter out oil components comprised in discharged or spent air with the aid of a filter device 3 in the form of an oil trap so that the spent air may be let off into the surroundings without oil contamination.

As its main component the medium servicing unit 1 possesses a high speed venting valve 4 having a valve housing 5, with which, by means of an interface 6, a functional unit 7 is detachably connected, such functional unit 7 in the present case being an oil trap 8.

The valve housing 5 in the present embodiment of the invention has a multiple part design. It possesses an inlet 12 connected with the section 14 approaching it of the compressed air line 2 and furthermore an outlet 13 connected the section 15, leading away from the valve housing 5, of such compressed air line 2. The approaching line section 14 is for instance connected to a source 16 of compressed air by the intermediary of a pressure reducing means 17 by which the input pressure of the compressed air at the inlet 12 may be set as required. The section 15 leading away from the housing extends for example to one or more connection points, not illustrated in detail, serving for the connection of pneumatic loads, it being possible if required for control valves to be placed in between.

In the valve housing 5 a principal flow duct 18 is formed, which in the is example straight, connecting the inlet 12 with the outlet 13. A check valve 22 is placed on this principal flow duct 18. Such check valve possesses a valve member 23 adapted to move in the longitudinal direction of the duct and which is urged by a return spring 24 into a closed position showing, in terms of figure 1, above the chained lined longitudinal axis 21 of the principal flow duct 18. In this closed position it has its seal 25 in engagement with a valve seat 26 annularly surrounding the principal flow duct 18.

By means of the check valve 22 the principal flow duct 18 is divided up into an inlet end duct section 27 and an outlet end duct section 28. The check valve 22 is so designed that flow of compressed air is possible in the principal duct 18 from the inlet 12 to the outlet 13 when the valve member 23 is moved clear of the valve seat 26 owing to the force resulting from the output pressure present at the out let end being larger than the output pressure at the outlet end and the opposing force due to the return spring 24. On the other hand the check valve 22 prevents return flow of compressed air in the opposite direction when the valve member 23 is urged against the valve seat 26 when the output pressure is larger than the input pressure. The return spring 24 lead to the advantage of ensuring stable switching conditions of the check valve 22 by being arranged downstream from the valve member 23 in the outlet end duct section 28, where it is held between the valve member 23 and a support portion 33 secured to the housing.

The valve member 23 possesses several axially extending guide bars 34 able to be slid on the bore surface of the principal duct 18, an intermediate space 35 being respectively present between guide bars 34 adjacent to each other in the peripheral direction, such intermediate space ensuring unhindered passage of the compressed air flow when the check valve 22 is open.

The outlet end duct section 28 of the principal flow duct 18 is connected with a venting duct 36, which leads to a venting outlet 37 opening at the interface 6 of the valve housing 5. An automatically actuated shut off valve 38 is placed on this venting duct 36 and like the check valve 22 is integrated in the valve housing 5 so that the resulting unit is compact.

The shut off valve 38 divides up the venting duct 36 into a supply duct section 42 communicating with the outlet end duct section 28 of the principal flow duct 18 and a duct section 43 leading to the venting outlet 37.

The shut off valve 38 possesses a closing seat 44 concentrically surrounding the venting duct 36 and secured to the housing, such seat 44 having a shut off valve member 47 able to be switched over between a closed shut off position 45 and an open venting position 46. In figure 2 the shut off position 45 is indicated on the left of the longitudinal axis 48 of the shut off valve member 47, which coincides with the direction of switching. In this case an annular sealing portion 50, provided on the first end face 49 of the shut off valve 47, sealingly engages the seat 44. In the venting position 46 illustrated on the right of the longitudinal axis 48 the shut off valve member 47 is lifted clear of the seat 44 and clears the passage along the duct. It is convenient if the shut off valve member 47 is designed in the form of a seat member as is illustrated.

In the present embodiment the seat 44 is located on the free end of a hump 53 extending coaxially into a fluid chamber 51 of the valve housing 5. It is in this manner that the opening 54, surrounded by the seat 44, of the downstream end duct section 36 is concentrically surrounded by the essentially annular fluid chamber 51. The fluid chamber 51 constitutes the terminal part of the supply flow duct section 42, which is at all times connected with the outlet end duct section 28 of the principal flow duct 18.

Between the moving shut off valve member 47 and the valve housing 5 a diaphragm 56 is arranged which is preferably concentric to the shut off valve member 47 and consists of a bendingly flexible, fluid-tight elastic material. Together with the shut off valve member 7 this diaphragm 56 constitutes a moving wall of the fluid chamber 51. Furthermore on its side opposite to the fluid chamber 51 the diaphragm delimits control chamber 57, which is connected by a control duct 58, formed in the valve housing, with the inlet end duct section 27 of the principal flow duct 18. The diaphragm 56 is responsible for a fluid-tight separation of the control chamber 57 from the fluid chamber 51 without any impairment of the mobility of the shut off valve member 47.

Since at its radially inner and its radially outer end the diaphragm 56 is statically fixed in place in relation on the one hand to the shut off valve member 47 and on the other hand in relation to the valve housing 5, more particularly by being clamped at such positions, the sealing action is extremely reliable and free of friction.

In the present embodiment the face of the diaphragm 56 facing the control chamber 57 constitutes an actuating face 59 effective in the closing direction, which is continuously subject to the input pressure of the principal flow duct 18 by way of the control chamber 57 and the control duct 58.

This subjection to the input pressure exists independently of the instantaneous position of switching of the shut off valve member 47.

Moreover an actuating face 62 is provided aligned oppositely to the above mentioned actuating face 59, such face 62 being effective in the opening direction of the shut off valve 38. The actuating face is constituted by the face of the diaphragm 56, facing in the closing direction 63 of the shut off valve member 47, and of the shut off valve member 47, such face surfaces delimiting the fluid chamber 51 in the shut off position. In the illustrated working embodiment of the invention it is consequently composed of the face of the diaphragm 56 and a surface section, placed outside the seat, of the shut off valve member 47. The above mentioned actuating face 62 effective in the opening direction, is continuously subject to the action of the output pressure of the principal flow duct 18 via the supply end duct section 42 of the venting duct 36.

It is in this manner that the actuating faces 59 and 62 aligned in mutually opposite directions, practically constitute a pressure balance, which is responsible for the current switching position of the shut off valve member 47. The current switching position of the shut off valve member 47 is dependent on the ratio between the two actuating faces 59 and 62 and on the ratio between the input pressure and the output pressure.

In the illustrated working embodiment the actuating face 59, which is effective in the closing direction is slightly larger than the actuating face 62 effective in the opening direction in the shut off position. The consequence of this is that, if the inlet pressure and the output pressure are identical, there will be a small resulting or differential force acting in the closing direction 63 on the shut off valve member 47, which holds the shut off valve member 47 in the shut off position.

Owing to the area ratio selected in the embodiment between the two actuating faces 59 and 62 it is possible to ensure that the shut off valve 38 will close the venting duct 36 as long as the output pressure present in the inlet end duct section is larger than or equal to the output pressure present in the outlet end duct section 28. Given a sufficiently large pressure difference in this case flow will take place through the principal flow duct 18 from the inlet 12 te the outlet 13. However as soon as the output pressure rises, owing to some technicality of plant operation - for example because of a reduction in the input pressure following reset ting of the pressure reducing means 17 - to exceed the input pressure a pressure differential will act across the two actuating faces 59 and 62, in the opening direction 64 on the shut off valve member 47 so that the same will now switch over into the venting position and compressed air will be able to flow from the outlet end duct section 28 via the venting duct 36 and its venting outlet 37 out from the valve housing 5. Accordingly the output pressure, that is to say the pressure present in the section 15 leading away from the valve housing, will be able to decrease to such an extent that the level of the input pressure is again reached. The check valve 22, which is closed during venting phase, will prevent return flow of the spent air to the approaching section 14 of the compressed air line 2 and the devices connected with same.

In the closed condition of the shut off valve 38 the opening 54 of the downstream duct section 36 is covered over by a closing face 65 provided on the previously mentioned first end face 49 of the shut off valve member 47. In the venting position 46 this closing face 65 is subject to the pressure obtaining in the inlet flow duct section 42 of the venting duct 36. In order to ensure that this does not have any disadvantageous effect on the desired manner of operation of the shut off valve, a compensation face 66 is provided on the shut off valve member 47, such compensation face 66 being directed in the opposite direction to the closing face 65 and consequently directed in the opening direction 64. Since the shut off valve member 47 preferably has a compensation duct 67 extending through it coaxially and which at one end opens at the closing face 65 and at the other end opens at the compensation face 66, the two above mentioned faces are always subject to the same pressure. Since the compensation face 66 is at least approximately the same in size as the closing face 65, irrespectively of the instantaneous position of the shut off valve member 47, no substantial resultant or differential forces will become established. Accordingly it is possible to ensure that the actuation of the shut off valve 38 is exclusively dependent on the instantaneous ratio between the input pressure and the output pressure and consequently the shut off valve 38 will automatically be switched in a fashion dependent on the respectively obtaining pressure ratio.

On its end portion axially opposite to the actuating face it is convenient for the shut off valve 47 to possess a more particularly cylindrically shaped guide piston or spool 68. The free end face of this guide spool 68 forms the compensation face 66. It is by means of this guide spool 68, which is arranged in a complementary guide recess 69 in the valve housing 5 for sliding in the longitudinal direction 48, that the shut off valve member 47 is guided in relation to the valve housing 5 and in a manner in which it keeps its alignment.

In order to prevent compressed air from flowing in the contact portion between the guide spool 68 and the guide recess 69 and between the control chamber 57 and the compensation chamber 70 which adjoins the shut off valve member 47 to the rear, from the compensation chamber 70 delimited by the compensation face 66, between the guide spool 68 and the guide recess 69 an annular seal 71 is arranged. It is seated in a peripheral groove in the guide spool 68. More particularly in order to compensate for friction caused by such seal 71, a closing spring 74 is arranged in the compensation chamber 70 in addition, such spring 74 bearing at one end against the valve housing 5 and at the other end against the guide spool 68 and the spring accordingly biases the guide spool 68 including the shut off valve member 47 in the closing direction 63. This is useful for instance because the compensation face 66 is slightly smaller than the closing face 65.

Instead of the diaphragm 56 it would be possible to provide some other setting or drive member, as for instance a piston arranged for movement on the wall of the fluid chamber 51 in the switching direction. Because of the seal still necessary here the friction occurring will however be somewhat larger than in the case of the use of diaphragm.

Apart form its compact dimensions the high speed venting valve 4 offers the special advantage that it is automatically operated without manual intervention simply on the basis of the respectively acting pressure ratios. By having a suitably large size of the cross section of the venting duct 36 superfluous compressed air may rapidly escape with the shut off valve 38 opened so that for practical purposes the high speed venting valve is automatic.

The compressed air discharged through the venting duct 36 may, if necessary, be subjected to some conditioning or treatment deemed to be necessary. For instance such treatment may involve de-oiling the spent air. For this purpose an oil trap 8 is provided on the interface 6, the filter device 3 thereof being connected with the venting outlet 37.

Accordingly the spent air will flow as indicated by the arrows 75 through the filter means 3 and will then blow off through lateral openings 76 of a shell- or bell-like housing 77, accommodating the filter device 3, into the outside air.

The trapped oil will drip into the lower part of the shelllike housing 77 whence it can be removed using a suitable runoff device 78 and then disposed of.

In a manner dependent on the condition of the compressed air and the conditions of use it is possible instead of the oil trap 8 to also provide a different type of functional unit 7. In this respect it would e. g. be feasible to have a silencer or a spent air duct with a large cross section, through which the discharged compressed air may be passed to some required point beyond the medium servicing unit. It will be clear that the interface 6 may be provided with differently designed coupling means in accordance with the respective functional unit 7 to be connected.

Claims

1. A high speed venting valve for pneumatic applications, comprising an inlet and an outlet for compressed air, which are connected by a principal flow duct for fluid flow, on which duct a check valve is provided to render possible flow of compressed air from the inlet to the outlet and to prevent return flow of compressed air in the opposite direction, such check valve dividing the principal flow duct into an inlet end duct section subject to the input pressure and an outlet end duct section subject to the output pressure, and furthermore comprising a venting duct communicating with the outlet end duct section of the principal flow duct, on which venting duct an automatically operated shut off valve is placed, such shut off valve having a shut off valve member able to be switched over between an open venting position permitting flow through the venting duct and a closed shut off position preventing flow through the venting duct, such shut off valve member being functionally connected with two mutually oppositely placed actuating faces, of which one is an actuating face effective in the closing direction and continuously subject to the input pressure and of which other is an actuating face effective in the opening direction and continuously subject to the output pressure so that for the shut off valve member there is a switching position dependent on the pressure ratio between the input pressure and the output pressure.

2. A high speed venting valve as set forth in claim 1, wherein the actuating face, effective in the closing direction, of the shut off valve is constituted by the moving wall of a control chamber, which communicates through a control duct with an outlet end duct section of the principal flow duct.

3. A high speed venting valve as set forth in claim 1 or in claim 2, wherein the actuating faces are provided at least partially on a bendingly flexible fluid-tight diaphragm, which extends between the shut off valve and the valve housing.

4. A high speed venting valve as- set forth in any of claims 1 through 3, wherein the actuating face adapted to be effective in the closing direction is at least as large as and preferably slightly larger than the actuating face oppositely effective in the opening direction.

5. A high speed venting valve as set forth in any of claims 1 through 4, wherein the shut off valve is designed in the form of a pressure force compensated seat member adapted to cooperate with a closing seat of the valve housing.

6. A high speed venting valve as set forth in claim 5, wherein the venting duct is divided by the shut off valve into a supply-side duct section communicating with the outlet side duct section of the principal flow duct, and a discharge-side duct section associated with a venting outlet, the shut off valve member possessing a closing face subject, in the shut off position, to the venting pressure obtaining in the downstream duct section, and furthermore a compensation face opposite to the closing face and at least approximately of equal size, the compensation face delimiting a compensation chamber, which communicates with the venting duct preferably through a compensation duct extending through the shut off valve member.

7. A high speed venting valve as set forth in claim 5 or in claim 6, wherein the shut off valve member is subject to the action of a closing spring acting in the closing direction.

8. A high speed venting valve as set forth in any of claims 1 through 7, wherein the shut off valve member is guided for sliding motion by means of a guide spool in a guide recess in the valve housing, an annular seal preferably being present between the guide spool and the guide recess.

9. A high speed venting valve as set forth in any of claims 1 through 8, wherein the check valve and the shut off valve are arranged in a common valve housing.

10. A high speed venting valve as set forth in claim 9, wherein the venting duct opens at an interface of the valve housing, which is adapted to render possible the connection of a functional unit, as for instance an oil trap, a silencer or a spent air duct, through which spent air may be passed on.

11. A high speed venting valve as set forth in any of claims 1 through 10, wherein same is adapted to be a component of a servicing unit for treatment of compressed air.

12. A high speed venting valve substantially as described hereinbefore with reference to and as illustrated in the accompanying drawings.

13. Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.