Patent GB-989641-A (GB)
Title: Improvements in or relating to manufacturing systems and methods
IPC: B65G19/02
Filed: 1962-02-23
Abstract: 989,641. Machine tool details. D. A. CARGILL. Feb. 23, 1962 [Feb. 27, 1961], No. 7049/62. Heading B3B. [Also in Division B7] A manufacturing system comprises a conveyer line with work stations spaced along it for performing successive manufacturing operations, certain of the work stations including automatic machinery requiring predetermined workpiece positioning, a plurality of pallets 22 movable along the conveyer line to transport workpieces to the successive work stations, means to stop individual pallets at the work stations and for locating the pallets at the automated work stations independently of the movement of other pallets and means for stopping successive pallets overtaking a preceding pallet. The pallets 22 are driven by a continuously movable chain 41 engaging with a sprocket 31 rotatably mounted on each pallet, the sprocket being prevented from rotation by engagement of its hub 32 with a spring biased pivoted clutch arm, 33 the pallets being stopped by disengaging the arm 33 and hub 32. The pallets may build up behind each other to form a float at each work station, the size of this float, and thus the spacings of the work station being governed by the operation to be carried out at that station. The pallets move from left to right in Fig. 6. Each pallet has a pair of leading wheels 27 and blocks 27a run between a pair of vertically spaced rails 28 on each side of the pallet. The sprocket 31 is mounted on a shaft 30, and the clutch arm 33 is pivotally mounted on the shaft 26a, it being normally held in engagement with the hub 32 of the sprocket ,.31 by a spring 37 whose tension is adjustable by means of a screw 38. In this way the sprocket is prevented from rotating and the pallet is moved along by the chain 41. A roller 39 is rotatably mounted at the forward end of each pallet and projects therefrom, and a retractable ramp 40a may be provided at each work station, so that when raised into the path of a roller 39, it raises the roller against the associated spring 37 to disengage the clutch arm 33 from the hub 32, the sprocket 31 then being able to rotate freely whilst the pallet remains stationary. Each pallet 22 also has a tail ramp 40 which disengages the drive to the next following trolley when the associated roller 39 engages the ramp 40. The ramp 40a is mounted on an arm 44 pivoted at 45 and provided with a stop 43. The arm is actuated by a cylinder 47 operated by a foot pedal and when the ramp 40a is lowered to permit the passage of a pallet held at the work station the stop 43 is raised to engage with a tail dog 42 on the next following pallet and so prevent its forward movement until the ramp 40a is again raised. Thus each pallet is stopped at the particular work station. The spring 37 on each pallet is adjusted to allow rotation of the sprocket 31 whilst the pallet is held by a positive stop. The arrangement in Fig. 6 is suitable for use at manual work stations, but at automatic work stations where accurate positioning of the pallet with a work-piece held thereon is essential, then the ramp 40a is replaced by a positive stop 40b, Fig. 6A, which engages a roller 39 when raised, to stop a pallet after which a retractable arm 48a, Fig. 6, is raised to position locating pins 48 in bushings 23 on the pallet and so accurately position it. The arm 48a has an extension 48b, Fig. 6A, which raises the roller 39 of the stationary pallet and disengages the clutch arm 33 from the hub 32. The conveyer may be arranged in a horizontal or vertical loop and in some cases the sprocket and clutch arm may be dispensed with, the pallets resting at one end in frictional engagement with the driving chain.