Patent GB-903780-A (GB)
Title: Conveyor system and control
IPC: B65G19/02
Filed: 1960-07-13
Abstract: 903,780. Conveyer systems.  RICHARDS-WILCOX MANUFACTURING CO. July 13, 1960 [Aug. 17, 1959], No. 24423/60. Class 104 (2). An overhead conveyer system comprises a main line consisting of side - by - side 'load and power tracks, a storage track, load carriers arranged to travel along the load and storage tracks, a pusher chain travelling along the power track, and co-operating members carried by the chain and by the carriers for propelling the carriers along the load track; a power - operated feed - in switch unit at one end of the storage track controllable by the carriers diverts thereto carriers from the load track; a control member actuatable by a carrier at the entrance end of the storage track when the latter is filled with carriers prevents entry of a further carrier into the storage track; a power-operated escapement switch unit at the other end of the storage track, controllable by the carriers and pusher chain, delivers carriers therefrom to the the load track; and a supplementary carrier - controlled arrangement renders the poweroperated escapement switch unresponsive to improper positioning of a carrier in the escapement switch unit and responsive to a carrier approaching the escapement switch unit when the escapement switch is empty. In the system shown in Fig. 1, load carriers are normally propelled around a closed loop load track LT by a pusher chain running on a power track PT arranged in sideby side relationship. Load carriers are diverted on to branch tracks B, C or D by a switch G and a sensing device E assumes a control position if the particular branch track B, C or D is full to prevent further load carriers being fed thereto. The load carriers pass from one end of the branch tracks B, C or D by gravity and each track is provided with a retarder device R. Switches H are provided at the end of each branch track B, C or D to divert load carriers on to the load track LT of the main line ML. Load carriers and drive chain.-The load carriers, Figs. 2 and 3, comprise a bar 35, from which the load is suspended by an eye bolt 37 or similar device, provided at each end with buffers 39 and the load bar 35 is hung from wheels 48 which run on tracks LT of inverted U-shaped section. Guide-wheels 35 are also provided. The load carriers are driven by a transverse pusher bar 61 engaged by spring-loaded pivotally-mounted pusher dogs, Fig. 4 (not shown), depending from a wheel mounted chain running on an inverted U-shaped track PT. Selector pins 55, 56 are mounted on the arms of a U-shaped member 57 carried by the bar 35. Construction and operation of the feeding switch.-The feeding switch G, Fig. 7, provided at the entrance end of each branch track B, C or D is mounted on an L-shaped frame overlying the entrance of the branch track and a part of the main line ML. A lengthwise slot 103 is cut in the side wall and running track of the load track LT adjacent the branch track B or C or D. An entrance guide 104 of angle section extends from the entrance end of the slot 103 to the branch track B or C or D and comprises a straight portion 105, approximately the same length as the slot 103, inclined away from the load track LT and a second straight portion 106 merging into a curve portion 107 seated at its end in a notch cut in the adjacent side of the branch track B. A switch point 111, having a straight side facing away from the branch track B and an inner curved side adjacent the branch track B having the same contour as the portions 105, 106 of the guide 107, 104, is suspended from a plate 117, Fig. 10 (not shown), reciprocally mounted in guides 118 secured to the frame 102 transversely above the main line ML. A guideplate 115 secured to the frame 102 and spaced from the guide rail 104 has an edge facing the guide-rail 104 of a configuration similar to the straight and curved portions 106, 107. The plate 117 is reciprocated between adjustable limit stops 119 by a piston-rod 120, projecting from a pneumatic cylinder C-1, to move the switch point 111 from a position in which the carrier can pass from the load track LT to the branch track B, thus blocking the load track LT to a position blocking the passage to the branch track B to allow the carrier to pass along the load track LT or vice versa. The load carrier, diverted from the load track LT to the guide member 104 and plate 115 by the switch point 111, is moved, once a transverse bar 61 has left the driving dogs of the power chain on the track PT, by a gravity-operated pawl 130; Fig. 8 (not shown), engaging the bar 61 and provided at the free end of a pivotally-mounted sweep arm 126 operated by a double-acting pneumatic cylinder and piston C-2. The admission in the exhaust of compressed air to and from the cylinders C-1, C-2 are controlled by a valve SV operated by two solenoids. Assuming the piston-rod 120 of the cylinder C-1 to be retracted with the switch point 111 in the position allowing load carriers to pass along the load track LT the feed in switch G is operated as follows. The selector pins 55, 56 of a carrier approaching the feed-in switch G along the load track LT depress arms 150, 151 to close switches LS-1, LS-2 to energize one of the solenoids controlling the valve SV. Air is now admitted to the cylinders C-1, C-2 to shift the switch point 111 to its feed-in position, shown in Fig. 7, in advance of the sweep arm 126 reaching the limit of a clockwise rotational movement. The front of the carrier, as it moves along the guiderail 104, switch point 111 and plate 115, operates a depending arm to close a switch LS-3, the switches LS-1, LS-2 being opened due to the movement beyond the arms 150, 151 of the selector pins 55, 56. The closing of the switch LS-3 energizes the other solenoid of the air control valve SV to feed air to the other ends of the cylinders C-1, C-2 to return the switch point 111 to a position allowing carriers to pass along the load track LT and to swing the arm 126 in a counter-clockwise direction in order to propel the load carriers into the branch track B. As the carrier enters the branch track B it momentarily opens a normally-closed switch LS-4 but this does not effect the operation since the other solenoid valve of the control valve SV has been energized. Likewise the following carrier momentarily closes the switch LS-3 but this does not effect operation since the other solenoid of the control valve SV has been energized. The switch LS-4 is a sensing switch and corresponds to the sensing device E shown in Fig. 1. When the storage track B is filled the last carrier holds a trip-bar, Fig. 12 (not shown), in the raised position to hold the switch LS-4 in the open position to preclude energization of the first-mentioned solenoid of the control valve SV and render ineffective the closing of the switches LS-1, LS-2 by the selector pins 55, 56 of an approaching carrier, thus the switch point 111 is held in the retracted position to prevent further carriers being diverted into the branch track B and such carriers then travel along the load track LT until they reach a branch track C or D to be diverted thereto or if such branch tracks are filled they are propelled along a by-pass track F. Construction and operation of the escapement switch.-The escapement switch H, Figs. 1 and 15, provided at the exit end of each branch track B, C or D is mounted on a rectangular frame 102E overlying the exit end of the branch track B and part of the main line ML. The load track LT is cut away to provide a lengthwise opening 103E. One end of an arcuate guidemember 104E of angular section is received at one end of the opening 103E and the other end of the guide member 104E fits into a notch cut in the side of the branch track B. A triangular switch point 111E, Fig. 21 (not shown), suspended from a plate 117E slidable between adjustable stops 119E in guides 118E mounted on the frame 102E transversely of the main line ML, is mounted in the slot 103E. One edge of the switch point 111E is curved in conformity with the guide member 104E and the other edge is straight. The wider or base portion 112E of the switch point 111E is of reduced thickness and fits into a recess in the bottom flange of the load track LT and the recess in the under surface of the guide-plate 115E, the edges of which plate are curved in conformity with the guide-member 104E. The ends of the flange 112E are also inclined towards the branch track B. When the switch point 111E is in the position shown in Fig. 15, load carriers can pass along the load track LT and the inclined ends of the flange 112E form a continuation of the curved portion extending across the exit from the branch track B and when a load carrier is delivered along the branch track B the leading vertical guide rollers 53 of the load carriers will contact the inclined end of the flange 112E to move the switch point 111E to the right in order to allow the carrier to pass along the guide 104E, guide-plate 115E and switch point 111E. A double-acting pneumatic cylinder and piston C-1E, vertically disposed above the load track LT adjacent the exit end of the guide-member 104E, actuates a pivotally-mounted stop-pawl movable into and out of the path of carriers passing from the escapement switch H to the load track LT. A second double-acting cylinder and pistons C-2E actuates a sweep arm 126E provided at its free end with a gravity-operated pawl for engagement with the pusher bar 61 to move load carriers from the branch track B to the load track LT. Rearward movement of the load carrier positioned at the end of the branch track B is prevented by a gravity-operated pawl 168 pivotally mounted above and movable into and out of the path of the carrier on the branch track B, Fig. 17 (not shown). An exit stop provided at the end of the branch track B comprises bell-crank arms pivotally mounted on each side of the branch track B and interconnected with a pivotally mounted primary stop arms 177 having dow