GB744513A - Improvements in or relating to exhaust braking apparatus for motor vehicles - Google Patents

Abstract

744,513. Regulating. CLAYTON DEWANDRE CO., Ltd. Dec. 14, 1954 , [Sept. 14, 1953], No. 25351/53. Class 7(6) [Also in Groups XXXI and XXXIV] A rotatable exhaust braking valve operated through a lever 11 is closed by an electromagnetic device 7 against the force of a spring means having a spring rate which increases during closing movement of the brake valve. The braking valve (not shown) is a butterfly throttle valve mounted in a flanged member 1, which is inserted in the exhaust conduit, and actuated from a shaft 6 journalled in the member 1 downstream of the braking valve and connected to the spring-loaded armature 9 of the electromagnet 7 the circuit 18 of which is controlled by a switch 20 which may be mounted on the dashboard or steering column. The armature may he loaded by a first spring 14 and by a second spring 17 which only comes into operation at the end of the closing movement of the braking valve, The switch 20 may be replaced by a switch actuated by the accelerator pedal when the latter is released or by a switch 25, Fig. 4, arranged on the brake pedal 24 and adapted, when the brake pedal is depressed, to be -closed by a pivoted member 26 on the brake pedal to cause actuation of the exhaust braking means before the wheel brakes are, brought into operation. The circuit 18 may also include a switch which is opened by a speed-responsive means, when the engine speed drops to idling, to cause the braking valve to be re-opened and prevent stalling. In one embodiment the speed-responsive means comprises a centrifugal governor and in another embodiment it comprises an electromagnetic device holding the switch closed, 'the circuit of which device is broken by the opening of the normal battery cut-out switch at idling. In a further embodiment, Fig. 8, the switch 20 comprises a pivoted contact 49 which in moving to the left first engages a contact 51 to close the circuit 18 of electromagnet 7 and close the braking valve, whereby the exhaust pressure rises and causes a pressure-responsive device to close a switch 47 in a holding circuit 48 which is energized when the contact 49 is moved further to the left to engage a contact 52, the contact 49 being held in its extreme left position against the action of a spring 50 by an electromagnet 53 in - the .circuit 48. When the engine speed drops to idling the switch 47 opens to de-energize the electromagnets 7, 53, whereby the braking valve opens and the contact 49 is returned by the spring. 50 to its "off" position. In Fig. 5 a spring-loaded latch 27 engages a recess .28 in an extension'of the armature 9 to hold the braking valve in the closed position and simultaneously breaks a switch 30 to de-energize the electromagnet 7. To reopen the braking valve, the control switch 32 is moved to the contact 34 to energizea solenoid 36 which withdraws the latch 27 from the recess 28, permitting the braking valve to be opened by its loading springs. In a further embodiment the electromagnet 7 comprises two solenoids, one of which is energized to partially close the exhaust valve for partial braking and both of which are energized for full braking. In Fig. 10 the electromagnet 7 is mounted coaxially with the braking valve shaft 6 and a pin 77 on the armature 9 engages a helical groove 76 in an extension 75 of the shaft 6 so that axial movement of the armature 9 rotates the shaft 6 to close the braking valve. The Provisional Specification describes a modification in which one coil closes the exhaust brake and a second coil opens the brake and states that the solenoid device may be. replaced by an electromagnet with a rotating armature.