Patent GB-911441-A (GB)
Title: Constant force pipe hangers
IPC: F16L3/217
Filed: 1959-06-15
Abstract: 911,441. Pipe hangers. GRINNELL CORPORATION. June 15, 1959 [Sept. 22, 1958], No. 20369/59. Class 99(2). In an hydraulic motor-operated constant-force pipe hanger for maintaining a substantially constant support force whose load-carrying piston 42 is hydraulically supported within the cylinder 18 thereof, pressure is supplied by means of a motor-driven liquid pump and the supporting force to be maintained is initially adjustable by the adjustment of pressure sensing means, the pump being mounted fixedly to the cylinder and means being provided for keeping the motor turned on when and as long as liquid is needed because of load movement in one direction. As shown in Fig. 1, the piston 42 is secured to a shaft 32 and is slidable on fixed rods 45, the shaft mounting a nut 46 carrying anti-friction ball elements 47 on the screwthread thereof for engagement with a spindle 48. The upper end of the spindle is secured to a brake disc 52 engageable by a brake shoe 60 carried by a piston 62 working in a cylinder 64 and normally urged against the periphery of the disc by a spring 68. A reservoir 84, containing hydraulic liquid 86, includes a pump 78 driven by an electric motor 82 and connected by a conduit 76, having a pressure reducing - valve 74 inserted therein, to the cylinder 18. A conduit 70 connects the conduit 76 with the cylinder 64, and a further conduit 100 allows communication between the reservoir and a chamber 31 between fluid seals 30 at the lower end of the cylinder. A pressure sensing element 94 in - the form of a Bourdon tube is inserted in the conduit 76 and actuates an electric switch 96 controlling operation of the motor 82. An overflow line 98 connects the upper end of the cylinder with the reservoir. In operation, a decrease in the load supported by the pipe hanger 36 attached to the shaft 34 causes a decrease in fluid pressure in the cylinder 18 and the element 94 actuates the switch 96 so that the motor 82 drives the pump 78, liquid then passing through the conduit 76 to the cylinder. The piston is moved upwardly until the fluid pressure in the cylinder reaches a value corresponding to the normal load carried by the hanger when the motor and thereby the pump is stopped. Conversely, with a decrease in load carried by the hanger, the relief valve 88 is actuated to allow fluid to pass from the cylinder to the reservoir. In the event of a loss of fluid pressure from the cylinder due to leakage the brake shoe 60 is forced by the piston 62 to engage the disc 52 which is rotated upon movement of the piston 42 in either direction. In a modification, the piston 62 carries a shoe provided with notches adapted to engage complementary notches on an upwardly extending stem secured to the piston 42, the disc 52 being dispensed with. In a further modification, a pressure accumulator 110, Fig. 5, comprising a spring- loaded piston 112 working in a chamber 111 and provided with a device 120 for actuating an electric motor 130 is connected between the cylinder 102 and the reservoir 125; alternatively the accumulator consists of a bag within a chamber and filled with a compressible gas.