Patent GB-1403888-A (GB)
Title: Control systems for vehicles operating on a track
IPC: B61L23/14
Filed: 1972-11-21
Abstract: 1403888 Fluid operated vehicle control system; railway systems UNIFLO SYSTEMS CO 21 Nov 1972 [30 Nov 1971] 53819/72 Headings B7L and B7N [Also in Division G4] In a moving block control arrangement for a tracked hovercraft system, fluid circuits respond to vehicle presence and act to control air supply to levitation and propulsion valves on the track. Each vehicle 25 is passive and when over a levitating valve 11 on track 10 provides pressure to open the valve so that levitation air is automatically supplied from plenum 15 beneath the base 13 of the track to a plenum chamber below the vehicle, similarly thrust valves 16 are automatically opened to propel the vehicle which is guided along the track by side walls 12. The valves 11, 16 can also be controlled via ducts 17, 18. The track is divided into sections 32-56 each of which is provided with a vehicle detector at its entry point and a fluid control circuit for a vehicle in the section. Vehicles are controlled to normal speed in the section by a timer 87 which is triggered by the entry of a vehicle into a section which is two sections before that containing the timer, e.g. the fluid circuit, Fig. 5, is for section 53 and includes timer 87 which is actuated by a signal on line 51AL from detector 51A at the entry to section 51. Until it times out the timer supplies an output on line 92 which is connected via OR gate 93 to an input of AND gate 85. If the timer period has not expired before the vehicle enters section 53, i.e. the vehicle is too fast, a signal from detector 53A is also applied to the AND gate which provides an output via OR gate 96 to inhibit the thrust valves in the section via line 53D. The AND gate also supplies an output to OR gate 93 and is thus held open until no signal is received from either detector 53A or 54A indicating that the vehicle has completely left section 53. If a vehicle present signal is received in the fluid control circuit from any of the detectors of the four clear sections in advance on lines 55AL-58AL it is used via OR gate 76 and OR gate 96 to inhibit the levitation and thrust valves in the section so that any entering vehicle is immediately stopped. This arrangement provides a stop block of four sections behind any vehicle. When a signal is received from detector 56A on line 56AL, i.e. the section which is four clear sections ahead of any vehicle about to enter section 51 and trigger the timer 87 in the fluid control circuit for section 53, the signal operates on the timer to increase its duration so that when the vehicle enters section 53 it is controlled to a slower speed. This condition of the timer is maintained for a nominal period for a vehicle to travel four sections and is then altered to provide a shorter timer period than normal for a nominal period for a vehicle to travel ten sections. Thus after each vehicle there is arranged a stop block of four sections, a slow block of four sections and an overspeed block of ten sections so that a following vehicle in this moving controlled length of track is controlled to a position between the last slow and the first overspeed sections.  If a vehicle is brought to a halt in a sectiondetectors 53A or 54A operated-a signal is applied via OR gate 79 and delay 81 to a Venturi which if no vehicle is signalled as present in the next four clear blocks in advance, creates a negative pressure signal to the levitate and cruise valves via line 53C so that these open to provide lift for the vehicle. Detector 53A also supplies a signal to the units to the rear for stop block control &c. via line 100, however where a number of vehicles are coupled to form a train this rearward signal is inhibited until a signal on line 52AL from the detector of the section to the rear indicates that this section is free. Arrangements for controlling the vehicles on merging track, on station tracks along which vehicles accelerate before joining a main track and on intersecting track, in which the track sections of the lines approaching the merging or intersection points are cross connected for control purposes are described with reference to Figs. 10 and 11 (not shown).