GB780461A - Pneumatic servo-controlled device for locking the suspension of one of the axles of a semi-trailer having more than one axle and/or moving to its operative position the forecarriage supporting the semi-trailer - Google Patents

Abstract

780,461. Spring suspensions; vehicle rest bars. OFFICINE VIBERTI SOC. PER AZIONI. Sept. 12, 1954, No. 26097/55. Class 108(2) [Also in Group XXIX] Relates to pneumatic servo control mechanism adapted to lock the suspension of one or more axles of a semi-trailer and/or move to its operative position, the forecarriage of the semi-trailer and to respectively release the suspension and withdraw the forecarriage. According to the invention, the mechanism comprises cylinders mounted on the semi-trailer, pistons, movable in the cylinders and acting respectively on members connected to the axle to prevent movement thereof in one direction and on the forecarriage for moving it to its road position, a pneumatic unit connected to the cylinders and means for controlling the pneumatic unit. As shown, a semi-trailer chassis comprises a pair of axles 2, 3 supported by interconnected leaf springs 7 and 8 and a wheeled forecarriage 10 comprising a rod 13 slidable in a cylinder 14 attached to the chassis frame. A locking device 26 also attached to the frame and is operative between the latter and the axle 3 when the trailer is disconnected from a tractor (not shown). The cylinder 14 and locking device 26 are connected in the compressed air circuit for the trailer braking system. The arrangement is such that the compressed air is supplied from a tractor through a coupling 16 to the trailer brakes 21, 22 and to a compressed air reservoir 20 through conduits 17 and 19 respectively and a distributer 18 of known form. When the coupling is disconnected, conduit 19 is connected to atmosphere and a valve 23 admits compressed air from the reservoir 20 to a hydraulic reservoir 24, the liquid in which is displaced through conduit 29 to actuate non return valves 25 associated with the locking devices 26 and the cylinder 14. When the coupling is reconnected, reservoir 24 is connected to atmosphere through valve 23, the locking devices are connected through line 30 with compressed air and liquid is returned to the reservoir 24 by resilient means incorporated in the locking devices 26. Each locking device comprises a cylinder 32 Fig. 5 and a piston 33 connected to a hollow piston rod 37 and loaded by a spring 42. Hydraulic fluid from the reservoir 24 is fed to a chamber 40 above the piston from the valve 25 which may be arranged adjacent or otherwise to the device 26. The valve 23 comprises a body 50, Fig. 6, having therein a chamber 51 communicating at its lower end via a pipe 52 with the reservoir 20 and via a pipe 53 with reservoir 24. A valve 54 is slidable in a bush 57, and controls compressed air flow through grooves in the bush. A disc valve 59 co-operates with the lower end of a spring loaded hollow member 61, a flange 62 of which bears on a flexible diaphragm 66 clamped between the flange and a cup 65. The arrangement is such that when the coupling 16 is disconnected the diaphragm is acted upon by atmospheric pressure only. The member 61 is forced downwardly by its spring into engagement with valve 59 which.opens valve 54 to admit compressed air from reservoir 20 to the reservoir 24 via ports 52 and 53. When the coupling 16 is reconnected compressed air is admitted to the diaphragm chamber at port 19, lifts member 61 to permit valve 54 to close to the position shown, and vents the reservoir through port 53 to the member 61 and atmosphere. Each non-return valve comprises a casing 72, Fig. 7, having a chamber therein which is connected. through ports 74, 75 and a non return valve 76, between conduit 29 and inlet port 41 of the locking devices 26. The chamber also includes a spring loaded relief valve 85. The valve 76 is released, to unlock the device 26 by a push rod 78 which is actuated through the flexible diaphragm 82 by compressed air admitted at port 84 from conduit 30 when the coupling 16 is connected.