Patent GB-778502-A (GB)
Title: Improvements in free-piston engines including starting means
IPC: F02B71/02
Filed: 1956-01-03
Abstract: 778,502. Starting-free piston engines. SOC. D'ETUDES ET DE PARTICIPATIONS EAU, GAZ, ELECTRICITE, ENERGIE SOC. ANON. Jan. 3, 1956 [Feb. 2, 1955], No. 212/56. Classes 7 (1), 7 (2) and 7 (5). An internal-combustion operated free-piston engine (compressor or gas generator) comprising at least one engine piston operating in an engine cylinder a return energy accumulator adapted for the purpose of starting the engine to be charged with compressed air which exerts pressure on the piston when the piston is in its starting position means for locking the piston in the starting position and means for disengaging the locking means to permit the compressed air to drive the piston inward on its compression stroke is characterized by the provision of a servo control circuit containing a starting control device adapted to complete the circuit when the engine is to be started, a second control device arranged in series in the circuit and adapted to complete the circuit automatically when the piston reaches a predetermined outer position and means operated automatically by completion of the circuit to permit supply of the compressed air to the accumulator. The servo circuit may be pneumatic or hydraulic. When the gas generator is stationary so that there is no pressure in the casing and when the circuit 23 is open because the switch 26 is open the piston assemblies 4, 5 are brought into their outermost end positions through the action of the reduction of pressure produced in the accumulators b by placing the interior thereof in communication with vacuum producing means which is connected to the pipe 38. In the last-mentioned position the rod 31 closes the switch 24. The switch 29 is also closed as a result of the reduction of pressure in the accumulators b. The piston assemblies are now in a position permitting starting and the operator merely has to close the switch 26 in order to initiate starting. Closure of the switch 26 first causes raising of the stop 27. The stop 27 is therefore positioned in the path of the hook 27a which in the outermost end position of the piston assembly 34 has passed beyond the stop 27. Simultaneously the slide valve 35 is brought into the position shown in Fig. 1 by means of the solenoid 25. Compressed air enters accumulators b from the pipe 37 the pressure therein moving the piston assemblies slightly inwards until the hook 27a engages the stop 27. When the pressure of the starting air has reached the requisite value for starting, the piston 47 moves towards the left and opens the switch 29 and therefore the circuit 23. Consequently the armature 45 ceases to be attracted by the winding 28 and the spring 46 acts upon the knuckle joint 41 and brings the stop 27 into the retracted position. Starting air in the accumulators can therefore drive the now unlocked free piston assemblies inwards. Since the action of the winding 25 on the armature 34 has likewise ceased the spring 39 brings the slide valve 35 into the position in which the latter places the pipe 36 in communication with the pipe 38. However as early as the end of their first inward stroke the piston assemblies 3, 4 have delivered some compressed air into the casing 9 with the result that a pressure increase occurs therein and brings the slide valve 30 into the closed position. If for any reason the first stroke of the arrangement should not result in normal starting pressure in the casing 9 would drop the slide valve 30 would open the pipe 36 and the pistons would be returned to their outermost end position. If at this moment the switch 26 should still be closed a new starting operation would be initiated automatically by closure of the switch 24 by the rod 31. The same device can be used for supplying compressed starting air and as a suction pump. The slide valve may be replaced by a change-over vane. In another arrangement a reversible compressor driven by a reversible electric motor is employed. In this case the control member 25 and spring 39 control an electric switch associated with the electric motor. The compressor can be used as suction or compression pumps for the brakes of a road vehicle on which the gas generator is mounted. The electromagnetic action of the winding 28 and the force of the spring 46 may be augmented by an appropriate pneumatic means through the agency of the excess and negative pressures in the accumulator b. A piston is connected to the member 42 and a solenoid operated valve is provided. During movement of the valve from its right to its left hand position the low pressure in the accumulator is able to act on the piston during the opposite movement of the valve pressure acts on the piston. Fig. 5 shows another arrangement. When the circuit 23 is closed the distributer 80 is brought into its upper position so that compressed air then arriving through the pipe 36 can pass through the valve 79 and the distributer 80 into the cylinder 77. The compressed air acts on the piston 76 and moves the stop 27 into the operative position. When the piston reaches the end of its leftward stroke 'it engages the rod 84 and opens the valve 73. As soon as the starting pressure in the accumulator b has reached the desired value the circuit 23 is opened. Thus the distributer 80 is moved down and places the cylinder 77 in communication with the atmosphere. This results in unlocking of the locking device. The locking element may act upon an element such as the lever 10 of the synchronizing means. In a vehicle such as a lorry the starter may have as its source of energy the battery of the vehicle.