Patent GB-341018-A (GB)
Title: Improvements in and relating to brake mechanisms
IPC: B60T11/04
Filed: 1929-09-06
Abstract: 341,018. Transmitting mechanismfor brakes. R OCKWELL, E. A., 1725, Diversey Parkway, Chicago, U. S. A. Sept. 6, 1929, No. 27122. Convention date, May 22. [Class 103 (i).] A thrust is exerted on a brake-operating lever 14 through a linkage comprising relatively movable members 18, 28 rotated about a fixed pivot 29 by the brake pedal or lever 16, relative movement between them being resisted by a spring 31 until the power exerted is sufficient to distort the spring, whereupon the members move relatively to each other causing the thrusting end 20 of the member 18 to slide relatively to the lever 14. The brake pedal or lever 16 is connected by an adjustable link 24 with a pivot stud 21 on a U-shaped lever 18 pivoted at 19 to an arm 28 pivoted to the casing 11 at 29. A face 20 on the lever 18 bears against the rounded toe 15 of the brake-operating lever 14. The spring 31 extends from a pin 32 on the lever 18 to a pin 33 on an arm 34 integral with the arm 28, and a link 36 pivoted on the pin 32 has a slot 37 to receive the pin 33. On depression of the brake pedal the lever 18 together with the bell crank 28, 34, will first swing about the pivot 29 to take up the slack. When the brake shoes &c. are in contact with a light initial pressure further movement of the pedal causes the face 20 to slide relatively to the toe 15 the pivot 19 moving in a clockwise direction about the fixed pivot 29 and the spring 31 being extended, the force exerted upon the arm 14 depending upon the resistance of the spring to extension. When the pin 33 engages the lower end of the slot 37 the levers will move as a unit about the fixed pivot 29 transmitting a direct thrust on the arm 14. The input arm of the lever is shorter when the parts are turning as a whole about the pivot 29 than when extending the spring so that the driver must exert an increased pressure to transmit a direct thrust to the arm 14. As shown the arm 14 operates servomechanism within the casing 13. The lever 18 is shaped to avoid interference with a speedometer connection 30. Fig. 3 shows a modification in which the pedal 16 is connected to the arm 42 of a bell-crank lever 40 pivoted at 41 on the arm 50 of a bell-crank lever 49 mounted on a fixed pivot 60. The other arm 43 of the bell-crank lever 40 has a pivoted bearing-plate 45 angularly adjusted by a screw 47 and contacting with the rounded end of the brake-operating arm 14. A compression spring 53 extends between a lug 56 on the arm 43 and the end 55 of the arm 54 of the bell-crank lever 49. The bell-crank levers 40, 49 are provided adjacent the pivot 41 with co-operating lugs 51, 52 normally held in engagement by the spring 53. An internal stop member 59 limits the compression of the spring and comprises a flanged tube held against the upper spring cap 57 by the spring. The initial movement of the pedal causes the levers 40, 49 to move about the fixed pivot 60 until the slack is taken up, when the spring 53 will be compressed and the pivot 41 will move in a clockwise direction about the pivot 60, the lugs 51, 52 separating and the plate 45 sliding on the lever 14. By changing the angle of the bearing-plate 45 the sliding movement may be regulated and the pivot 41 stabilized. When the stop member 59 engages the lower spring cap 58 a direct thrust will be imparted to the brake lever the parts again moving about the fixed pivot 60. To alter the pedal movement an additional hole 83 is provided in the lever arm 42, and an adjustable stop 39 limits the upward movement of the pedal under the action of a retracting spring 80. Springs 38 having different lengths but the same resistance may be inserted between the lugs 55, 56 to alter the pedal movement, and the internal stop member may be omitted, a helical spring of square cross section being used and complete closure of the spring acting as a stop. Fig. 13 shows the linkage used without a servo device, the lever 40 engaging a brake-operating lever 70 on a cross shaft 71 carrying a lever 72 to which front and rear brake rods 65, 62 are attached. An emergency hand-lever 68 is connected to the lower end of the lever 72.