Patent GB-818899-A (GB)
Title: Improvements in or relating to mechanically propelled two wheel vehicles
IPC: B62D61/02
Filed: 1956-05-24
Abstract: 818,899. Safety wheels for motor-cycles. PEARSON, H. M. Aug. 19, 1957 [May 24, 1956], No. 16084/56. Class 136(1) [Also. in Group XXIX] In a mechanically propelled two-wheeled vehicle, such as a motor-cycle or motor scooter, provided with a pair of retractable stabilizing wheels 8 mounted one on each side of the vehicle, means dependent on the forward speed of the vehicle are provided for automatically moving the stabilizing wheels from an operative or stabilizing position, in which these wheels are in contact with the ground, to a retracted position when the vehicle speed exceeds .a critical value and for restoring these wheels to their stabilizing position when the vehicle speed falls below this value. Each stabilizing wheel 8 is pivotally mounted on one end of an arm 9 fixed at its other end to an axle 12 rotatably mounted in brackets 10 fixed to the vehicle frame. The mounting of the wheel .8 on the arm 9 includes spring controlled castor mechanism 11. The plates 12<SP>1</SP>, 12<SP>2</SP>, .are fixed to the axle 12. The plate 12<SP>1</SP> is connected to piston rod 13 of a hydraulic cylinder 14. The plate 12<SP>2</SP> is connected to one end of a tension spring 16 the other end of which is pivotally connected to the vehicle frame at 17. Hydraulic . fluid is supplied from a reservoir 27 by a pump 24 driven from the transmission shaft 26 of the vehicle through reduction gearing 25. While the vehicle is stationary, the wheels 8 are maintained in their operative positions in contact with the ground by the action of the tension spring 16. When the vehile starts to move forward the pump 24 causes the hydraulic fluid to be drawn from the reservoir 27 through a pipe 28 to a pipe 23 and through a retraction control unit 55. A manually operated screw 56 controls an .adjustable orifice in the unit 55 so that the speed set for retraction of the wheels may be adjusted. When the vehicle speed exceeds the speed set for retraction the orifice in the control unit 55 can no longer pass all the fluid supplied by the pump and a pressure is built up in front of a valve member 40 in a control device 21 (Fig. 3). The valve 40 is caused to move against the pressure of a spring 43 into a position to uncover a passage 46. The excess flow of fluid passes under high pressure through a port 20 and a pipe 19 into the cylinder 14, the piston and piston rod of which iare thereby actuated to re-  tract the wheels 8 against the pressure of the spring 16. As soon as the speed of the  vehicle drops below the critical value all the fluid can pass through the orifice in the unit 55 and the valve member 40 will be returned by its spring 43 into the position in which the passage 46' is closed and a port 42 is opened. The port 42 communicates between the pipe 19 and the reservoir 27 through a pipe 28. The fluid in the cylinder 14 is exhausted to the reservoir 27 by the action of the spring 16. An emergency valve 35 is provided for enabling the wheels 8 to be lowered even if the automatic control valve 21 should be defective. The valve 35 is manually opened to enable fluid to flow from the cylinder 14 through pipe 19 directly into the pipe 28. Thus the fluid in the cylinder 14 will be exhausted and the wheels 8 will move into contact with the ground. When the speed of the vehicle is high enough to produce an excessive flow of the fluid from the pump which cannot pass through the orifice of the unit 55 and the cylinder 14 is full, then the fluid pressure will increase and open a spring loaded non-return valve 32 through which fluid will flow back to the pipe 28.