Patent GB-277220-A (GB)
Title: Improvements relating to air and other gas compressors
IPC: F04D27/02
Filed: 1927-02-01
Abstract: 277,220. Jude, A., and Belliss & Morcom, Ltd. Feb. 1, 1927. Regulating or controlling.-Apparatus for controlling compressors, especially for preventing surging in turbo-compressors, by closing a valve in the inlet when the discharge pressure exceeds a determined value, comprises a device responsive to the discharge pressure controlling an electromagnetic relay which operates a fluidpressure engine to control the valve. A device responsive to the discharge volume may prevent action of the relay until the discharge volume has fallen sufficiently. A discharge relief valve may open and close as the inlet valve closes and opens. The inlet throttle valve a<0> and discharge relief valve b<0> are linked to one arm d<5> of a lever, the other arm d' of which is operated by the rod of a piston d<1>. This piston moves under the action of oil or air supplied under pressure through ports controlled by a valve e<0>. This valve is operated through levers g<1>, g<2> by a piston h operated by electromagnetic valves n which open the ends of the cylinder i either to compressed air or atmosphere. The valves consist of soft iron discs faced with split skin &c., attracted by electromagnets j<1>, j<2>. The coils of the magnets are connected to contacts v<1>, v<2> respectively, with which a contact v<0> engages in -the end positions of the lever arm d<5>. The other ends of the coils are connected respectively to a piston t<1> moved in accordance with the volume of air supplied and to a lower contact r<2> on a cylinder o‹ in which is a piston p<0> moved under the pressure of the supply and connected to a weighted lever q. The piston t' is subject on its upper and lower faces to fluid in the discharge pipe b<2> entering through reverse Pitot tubes s', s<2>. It is supported by a spring and carries a contact adapted to engage a contact u<1> connected with an upper contact r' on the cylinder o‹. The weighted lever q carries a contact adapted to engage either of the contacts r<1>, r<2>, and connected through a battery w with the contact v<0> on the lever arm d<5>. When the valve a‹ is fully open and the valve b<0> correspondingly closed, the circuit of the electromagnet j<2> is broken. If owing to reduced demand the pressure rises sufficiently, contact will be made between the parts r', r<2>. If, further, the volume is sufficiently reduced, the parts u<1>, u engage and complete the circuit. The right hand valve n is lifted, allowing compressed air to escape from the right hand of the piston h which is moved to the right, moves the valve e‹ to the left and causes the piston d to pull the lever d<3>, d<5> over and reverse the valves a<0>, b<0>. Fig. 8 shows a modified form of volume-controlled switch. The reservoir k by which compressed air is supplied to the cylinder i may be supplied through a non-return valve from one of the lower pressure stages and through a reducing valve from the high pressure main. The pistons h, d' may in some cases be single acting, being returned by springs. The valves and magnets may be multiplied in parallel, in large installations. Fig. 4 shows the upper plate of one of the valve casings, formed of non-magnetic material into which the magnets are screwed and provided with multiple valve ways k<1> surrounded by countersunk grooves y forming valve seats. The lower plate, Fig. 6, comprises an annular recess z<1> connecting with the cylinder i and enclosing a central recess z<2> separated from it by a stepped ring of metal. Ring grooves are countersunk around the valve ways m<1> to form valve seats intersecting each other and the stepped ring, the parts thus cut away from the ring forming passage ways between the cylinder i and the valve ways. The plates may be die cast.