Patent GB-1427869-A (GB)
Title: Control unit for electrically operable vehicle brake
IPC: B60T7/00
Filed: 1974-03-07
Abstract: 1427869 Electrically-operated brakes; warning-devices SYNCRO CORP 7 March 1974 [2 April 1973] 10322/74 Headings F2E and F2F [Also in Division H1] A control unit for an electrically-operable brake for a vehicle towed by a tractor vehicle comprises a resistance element including a continuous layer of resistive material and a conductor electrically connected with the layer of resistive material, the conductor being adapted for electrical connection to a source of electric potential or the brake, and a contact element progressively engageable with the layer of resistive material to vary the resistance between the contact element and the conductor, the contact element being adapted for connection with the brake or the source of electric potential, so that during use the current through the layer of resistive material is varied to vary the degree of brake application. As shown in Figs. 1 and 3 to 5, the coils 25 of electrically operated trailer brakes are progressively energized by lowering a pivoted arm so that resilient fingers 49, Fig. 3, of a metallic contact element 16 secured to the arm make successive contact with a thick film or layer 57 of resistive material deposited on a ceramic substrate 54 and constituting a resistance element 15, Fig. 5; the contact element 16 is connected at 17 to a battery 18 while a conductor 55 in electrical contact with layer 57 is connected to the brake coils 25, Fig. 5. The shape of the conductor 55 ensures that the current flow increases at an increasing rate as the contact element 16 progresses from right to left, but alternative shapes are described later. An additional metallic contact 56 on the substrate 54, and touched first by contact element 16, is connected to a tail lamp 23. A further lamp 28 in series with a semi-conductor rectifier 29 is energized to warn the operator when the low impedance represented by coils 25 is disconnected as a result of defective brakes or defective connection. In Fig. 9 (not shown) layer 57 has a triangular gap extending in from the right, and conductor 55 extends only half way from the left; in Fig. 10 (not shown), conductor 55 is narrow, triangular and extends only half way from the left; in Fig. 8 (not shown) conductor 55 is T-shaped and is laid directly on the ceramic substrate 54, separating two rectangular strips of resistive material; in Fig. 6 (not shown) a series of separate transverse strips of resistive material is overlain by a T-shaped conductor and the contact element 16 is continuous with two longitudinal beads: the latter contact element may be used with the resistance element of Fig. 8. In Fig. 1, the arm may be operated either by hand at 13 or by an hydraulic piston and cylinder device 14 connected to the master cylinder 34 of the tractor-vehicle brakes. In Fig. 11 two control units connected in parallel are provided: 73 for hand operation, 74 for hydraulic operation, the latter being near the master cylinder 34 away from the operator's cab. The hand rod 13 or 38 may be rotated to vary the position along it of an operating member 40, Fig. 11, to vary the mechanical advantage. Resistor 76 is selected in accordance with trailer loading or brake characteristics.