Safety valves

April 21, 1964

3,129,784

C. D. P. SMALLPEICE

SAFETY VALVES Filed Oct. 31, I960

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United States Patent Office

3,129,784

Patented Apr. 21, 1964

3,129,784 SAFETY VALVES

Cosby D. P. Smallpeice, “Flagstaff,” Swanwick Shore, near Southampton, Hampshire, England, assignor of one-half to Nuquip Limited, Richmond, Surrey, Eng- ⁰land

Filed Oct. 31, 1960, Ser. No. 66,172 Claims priority, application Great Britain Mar. 22, 1960

Claims. (Cl. 181—37) ¹⁰

The invention relates to a valve which is adapted to open when a predetermined fluid pressure is reached and is adapted primarily for use as a safety valve in the exhaust line from a pneumatically-operated system. The object of the invention is a valve of the kind referred to 15 which is of simple construction and will remain open after affording pressure relief.

According to the invention a valve which is adapted to open when a predetermined fluid pressure is reached, and to remain open, includes a hollow cylindrical body 20 provided with an inlet for the fluid and having, in its cylindrical wall, at least one outlet normally sealed by a contractile member which engages round the exterior of the cylindrical wall, the contractile member being supported such that it will be displaced axially of the said 25 wall by the escape of the fluid under a pressure superior to the predetermined one, whereby afterwards to leave the outlet unsealed.

According to a still further feature a plurality of the outlets are arranged on a circle round the body for co- SO action with a single contractile member.

The contractile member is a band of a resilientlyextensible, impervious material which is engaged round the body in a condition of tension so as to cover the outlet or outlets, the tension in the band being chosen S5 to set the predetermined pressure, within the body, at which a said outlet will be opened with resultant displacement of the band axially of the body to an unsealing position.

According to a still further feature the valve can have a body of a porous material and form a silencer for a gas exhaust, the outlet or outlets being adapted to open when a predetermined back-pressure arises in the body due to the pores of the latter becoming choked.

In the accompanying drawings:

FIGURE 1 is a longitudinal section through one form of valve in accordance with the invention adapted for use as a silencer for a pneumatic exhaust;

FIGURE 2 is a section on the line 2—2 of FIGURE 1, _Knand

FIGURE 3 is a sectional diagram illustrating the operation of the valve.

Referring to FIGURES 1 and 2 the valve includes a porous cylindrical element 10 having a closed end 11, ₅₅and its opposite end open and made sealingly fast with an adaptor 12 provided with a screw thread 13 for enabling it to be connected to an exhaust pipe from a pneumatic system. The element is provided in its cylindrical wall with a plurality of ports 14 which are arranged in a θθ ring and are normally covered by a contractile band 15 of a natural or synthetic rubber or of another suitable, resiliently-extensible, impervious material.

The band is arranged to be under tension so that should the pressure within the element rise above that which is predetermined by the pressure of the band, the latter will be forced away from the ports to allow the excess pressure to escape. By the nature of the band the escaping pressure passing round its opposite edges will tilt the band laterally and force it to one side as indicated in ₇q FIGURE 3 whereby to leave the ports open so that the valve will not close again should the pressure within the element afterwards drop. Thus, as soon as choking of the pores of the element 10 with suspended matter from the exhaust from the pneumatic system impairs its permeability the pressure within the element will rise and cause one or more of the ports to open for relieving the excess pressure. This results in the band 15 being moved axially of the element to an out-of-the-way position, and the escaping of the fluid from the ports will give a warning that the filter element ought to be removed for cleaning, or renewed.