GB2216991A - Pneumatic valve - Google Patents

Abstract

A pneumatic valve particularly for use in controlling needle operation in a tufting machine comprises aligned inlet and outlet ports (21, 22) a valve member (23) between the flanks of which and the valve body (11) air may pass in moving between the ports, an exhaust passage (25) in the valve member communicating with an exhaust port (15), and the inner end of the exhaust passage defining a valve seating for a valve element (28) movable between a position in sealing contact therewith to prevent exhaust of air from the chamber (12) and a position in which the element seals the inlet port and opens chamber (12) to exhaust. Movement of the valve element (28) into contact with the seating is effected by incoming pressure air and into sealing relationship with the inlet port, on cessation of pressure feed, by the residual pressure air in the chamber. In an alternative embodiment the valve member (23) is integrally formed with body part (17). <IMAGE>

Description

PNEUMATIC VALVES The invention concerns pneumatic valves, and has more particular reference to miniature quicAk-exhaust valves for use in controlling the application of air under pressure to pneumatic actuators.

One particular application of such valves is in the context of a controlled needle tufting machine wherein a needle is moved to or from an operating position, by a pneumatic actuator, according to whether or not that needle is to reciprocate through a backing fabric and thus insert a loop of yarn therein.

Since a tufting machine operates at high speed, say between 200 and 450 cycles per minute, a particularly rapid response of the actuator is necessary, and speed and reliability of operation are of paramount importance.

In the known quick-exhaust valve, the path followed by the pressure air in moving through the valve is non-linear, and such non-linearity is thought likely to inhibit the effectiveness of the valve, particularly at the extremely high operating speeds necessary in the field of tufting machinery.

It is an object of the present invention to provide a quick-exhaust valve wherein speed of operation, and particularly of the application of pressure air to an actuator, is maximised.

According to the present invention there is proposed a pneumatic valve comprising a valve body having inlet and outlet ports in opposed faces thereof, and an exhaust port at a position transverse to said inlet and outlet ports, the valve body defining a valve chamber therein in fluid flow connection with said inlet, outlet and exhaust ports, a valve member within said chamber and providing a flow passage between said inlet and outlet ports, said valve member having a flow passage therein in fluid flow connection with the exhaust port and said chamber, and a floating valve element selectively engageable with a seating on said valve member to close the flow passage therein whilst allowing passage of pressure air from the inlet to the outlet port, the valve element being displaceable from its seating on reduction of inlet pressure to place the chamber in fluid flow connection with the exhaust port.

According to a preferred feature, the floating valve element is movable between a first position in engagement with the seating on said valve member to close the flow passage therein and a second position remote from said seating in engagement with a seating about said inlet port to close the same against passage thereto of pressure fluid in the chamber.

According to a further preferred feature, the valve body is of two part construction and the member is formed integrally with one part of the valve body.

The invention will now be described further, by way of example only, with reference to the accompanying drawings in which Fig. 1 is a longitudinal section through a pneumatic valve constructed in accordance with the invention; Fig. 2 is a section taken on line Il-Il of Fig. 1; Fig. 3 is a view corresponding to Fig. 1 and shows the pneumatic valve as applied to a control piston of the kind used in the context of tufting machinery; Fig. 4 is a view similar to Fig. 1; and shows an alternative to the embodiment illustrated therein; and Fig. 5 is a section taken on line V-V of Fig. 4.

Referring now to the drawings, and particularly to Figs.

1 and 2 thereof, a pneumatic valve constructed in accordance with the invention comprises a valve body 11 defining a chamber 12 therein, inlet and outlet ports 13, 14 to said chamber, said ports 13, 14 being arranged in opposed disposition in the walls to the chamber, and an exhaust port 15 positioned transversely of the inlet and outlet ports.

The valve body 11 is of two-part form, each part 16, 17 providing a respective one of the inlet and outlet ports 13, 14 and being of cup-shaped form, the parts being arranged in opposed disposition and being screw-threadedly connected together to define chamber 12 aforesaid therebetween. Respective spigots 18, 19 extending outwardly from the base of the parts 16, 17 provide fluid flow passages 21, 22 leading to inlet and outlet ports 13, 14.

Valve body parts 16, 17 are cylindrical in form, and exhaust port 15 is provided in the side wall of body part 16.

The inner end of the body part 17 is flat and perpendicular to the axis of such part, whilst the inner end of body part 16 is conical for a purpose hereafter to be made apparent, the inlet and outlet ports lying on the axis of the cylindrical chamber 12.

The valve further includes a valve member 23 provided as a tight fit within body part 16, said valve member being of a lesser axial extent than the said body part and terminating in spaced disposition relative to the opposing inner endzf such body part.

The inner end of valve member 23 is of stepped configuration, and such member 23 is provided with a flow-passage 24 having an axially extending portion 25 coaxial with the stepped end region of the valve member and a radial portion 26 positioned to register with exhaust port 15 in body part 16. The annular outer end of the stepped end region 27 defines a seating to receive a floating valve element 28 into sealing engagement therewith.

The flanks 29 of the valve member 23 are flat, as can be seen in Fig. 2, to define flow passages 31 connecting front and rear parts 32, 33 of chamber 12.

Valve element 28 is a thin body of an elastomeric material and is of generally conical form, the base of such element being recessed, as at 34, and the apex thereof being enlarged to provide a cylindrical locator 35 for engagement in the inner end of flow passage 21 on movement of the element from seating engagement with stepped end of the valve member. Valve element 28 is a free fit within the chamber 12, whilst the cone angle of the outer surface thereof corresponds with the conical inner end face of body part 16.

In use, with a pressure line connected with spigot 18 and with spigot 19 connected with the pneumatic device, not shown, operable through the valve, on feed of pressure air, valve element 28 is moved into engagement with the stepped end 27 of valve member, thus to close flow passage 24, and pressure air flows around the edge of valve element 28, deforming such edge to increase the through flow area by pivotting about the reduced thickness region of the element in so doing according to the stiffness of the material of the valve element, through flow passages 31 to part 33 of the chamber and thence through outlet port 14 and flow passage 22 to the pneumatic device, say a piston and cylinder arrangement.

On termination of the supply of pressure air, the pressure differential between the two sides of the valve element 28 moves such element from its engagement with end region 27 of the valve member into seating engagement with the inner end of body part 16, thus opening flow passage 24 and closing inlet passage 21. Pressure air within the chamber passes to atmosphere through passage 24 and exhaust port 15.

On further feed of pressure air through inlet port 13, valve element 28 is moved into seating engagement with the stepped end 27 of the valve member, and pressure air is thus applied to outlet port 14 as before.

The in-line character of the inlet and outlet ports and generally straight-line path through the chamber for incoming air provides for a rapid and accurate control of the application of pressure air to the-pneumatic device. Furthermore, the opening of the exhaust passage, and the automatic closing of the. inlet passage, upon the attainment of a pressure differential between the two sides of the valve element, allied to the provision of an exhaust passage of increased cross-sectional dimensions, provides for a quick exhausting of the pressure within the chamber, thus facilitating any spring,or otherwise induced, return motion of the pneumatic device served by the valve.

One particular application of the pneumatic valve hereinproposed is in the field of tufting machinery, where the need exists for the selective movement of a tufting machine needle between operative and nonoperative positions relative to a reciprocating drive element. The machine operates at say, 200 to 450 cycles per minute, and thus minimal time only is available for effecting lateral movement of a given needle between operative and inoperative positions. Furthermore, the space available for pneumatic actuators is limited, and thus miniature actuators must be used. Accordingly, the requirement is for a reliable quick-exhaust valve capable of ready and accurate response to frequent, short duration operations, and which is of minimal dimensions, say of the order of 7 mm diameter.

A structure suitable for use in controlling tufting machine needle operation is shown in Fig. 3, and will be seen to comprise a piston and cylinder arrangement of which the piston is located within the body of the valve illustrated in Figs. 1 and 2 and of which the piston rod extends outwardly of an elongated such body.

Thus, referring now to Fig. 3, in which like reference numerals are used to those of Figs. 1 and 2 for the same or similar parts, the outlet part is effectively co-extensive with the end wall of the valve chamber, and merges into a chamber 33 of elongated, stepped form, to receive a piston 36 and piston rod 37, there being a return spring 38 between the rear face of the piston and a step 39 formed in the wall of chamber 33. A sealing ring 41 is seated in a peripheral groove in the piston, and the piston rod 37 extends outwardly from the valve body 11.

The front face of the piston is provided with a screw slot to facilitate engagement of the threaded remote end of the rod with a suitable support, not shown, access to such slot being had from within the body part 17 prior to the assembly together of body parts 16, 17.

The operation of the arrangement shown in Fig. 3 is directly analogous to that illustrated in Figs. 1 and 2, and no further description is thought necessary.

In a simplified form of the valve, see now Figs. 4 and 5, valve member 23 is formed integrally with body part 17, the latter being of stepped configuration and having a threaded outer periphery for engagement with an internal thread at the opposing end of body part 16. As an alternative to the screw threaded engagement between the body parts, such parts may be an interference fit one with the other or the said parts may be bonded together.

The operation of the codified form of valve is directly analogous to that of the embodiment shown in Figs. 1 and 2, and again no further description is thought necessary.

The invention is not restricted to the exact detail of the embodiments hereinbefore described since alternatives will readily present themselves to one skilled in the art.

The arrangements shown in Figs. 1 to 3, save for the valve element, will ordinarily be of metal, for example brass, whilst the embodiment of Figs. 4 and 5 will be of moulded construction.

Claims (11)

1. A pneumatic valve comprising a valve body having inlet and outlet ports in opposed faces thereof, and an exhaust port at a position transverse to said inlet and outlet ports, the valve body defining a valve chamber therein in fluid flow connection with said inlet, outlet and exhaust ports, a valve member within said chamber and providing a flow passage between said inlet and outlet ports, said valve member having a flow passage therein in fluid flow connection with the exhaust port and said chamber, and a floating valve element selectively engageable with a seating on said valve member to close the flow passage therein whilst allowing passage of pressure air from the inlet to the outlet port, the valve element being displaceable from its seating on reduction of inlet pressure to place the chamber in fluid flow connection with the exhaust port.

2. A pneumatic valve as claimed in Claim 1, wherein the floating valve element is movable between a first position in engagement with the seating on said valve member to close the flow passage therein and a second position remote from said seating in engagement with a seating about said inlet port to close the same against passage thereto of pressure fluid in the chamber.

3. A pneumatic valve as claimed in Claim 1 or 2, wherein that end wall of the valve chamber within which the inlet port is provided and the opposing face of the floating valve element are of corresponding conical form.

4. A pneumatic valve as claimed in Claim 3, wherein the floating valve element is of conical form, the periphery of element being flexible.

5. A pneumatic valve as claimed in Claim 4, wherein that face of the floating valve element engageable with the valve member to close the flow passage therein is rebated to define a reduced thickness region in closely spaced disposition relative to the periphery of the element about which the edge of the element pivots to allow flow of fluid between the inlet and outlet ports.

6. A pneumatic valve as claimed in any one of the preceding claims, wherein the flow passage in the valve member comprises axial and radial sections respectively in alignment with the inlet port and the exhaust port, flanks of the valve member remote from the radial section being flat and arranged in spaced apart relationship from the opposing wall region of the chamber to define a part of the flow passage between the inlet and outlet ports.

7. A pneumatic valve as claimed in any of the preceding claims, wherein the valve body is of two-part construction and the valve member is formed integrally with one part of the valve body.

8. An actuator for a tufting machine including a pneumatic valve as claimed in any one of the preceding claims, wherein the outlet to the valve chamber connects with a cylinder arranged coaxially therewith, pressure air delivered to the outlet being applied to a resiliently loaded piston movable in said cylinder, the piston being connected with an actuator rod at that face thereof remote from the chamber and adapted to effe-ct reciprocation thereof under the combined effect of resilient and pneumatic pressures applied to the opposite faces of the piston.

9. A pneumatic valve substantially as hereinbefore described with reference to and as illustrated in Figs. 1 and 2 or 4 and 5 of the accompanying drawings.

10. An actuator including a pneumatic valve as claimed in Claim 9.

11. An actuator for controlling needle operation in a tufting machine including a pneumatic valve as claimed in Claim 9 or substantially as hereinbefore described with reference to and as illustrated in Fig. 3 of the accompanying drawings.