Patent GB-936580-A (GB)
Title: Improvements in or relating to tube forming machines
IPC: B29D23/00
Filed: 1960-02-01
Abstract: 936,580. Tube-making machines. ARMSTRONG CORK CO. Feb. 1, 1960 [Feb. 12, 1959], No. 3557/60. Class 99(2). A machine for wrapping a ribbon of stock, e.g. an unvulcanised web of synthetic rubber composition 9 supported on a web of Holland cloth of polyethylene 10, about a mandrel M and forming a seamed joint, comprises the combination of a pair of relatively movable seaming knives 79, 81, means for delivering a metered ribbon of stock as a festoon between the knives in open position, a cradle 30 for supporting a mandrel disposed within the festoon of stock, a cradle support 41 to which the cradle is attached for limited pivotal movement relative thereto, means for relatively moving the seaming knives to seam forming position to wrap the festoon of stock about the mandrel and form a seam therein, and means for imparting a limited pivotal movement of the cradle with respect to the cradle support with the seaming knives in the seam-forming position to rupture the formed tube from the ribbon of stock. As shown in Fig. 1, the machine for making the tube includes a stock feeding, guiding and measuring unit 2 mounted on a main frame 3, a mandrel supporting and positioning unit 4 which is adjustable to accommodate mandrels of various sizes and is provided with a retracting mechanism to aid in separation of the completely formed tube from the trailer ribbon and in gravity discharge of the mandrels, the unit being pivoted to an adjusting mechanism, and a seam-forming device 6 which performs the function of wrapping the stock around the forming mandrel prior to seam formation and includes a movable seam forming knife which engages the ribbon of stock as the knife travels toward a stationary seam-forming knife, draws the ribbon around the mandrel, forms the seam, and simultaneously welds, the ribbon of stock above the seam on to a " trailer " ribbon. There is also indexing mechanism 7 which serves periodically to extract a short portion of the trailer ribbon to provide a fresh area of stock to which to weld the severed end of the stock upon completion of each seaming operation of the machine, and a stock clamping unit 8 which presses the stock in engagement with the stationary seamforming knife during mandrel positioning and seam forming. The roll of stock 11 is supported on a stand 12 adjustable transversely and for pivotal movement by handwheels 13, 14; the combined web of stock and Holland cloth is withdrawn from the roll 11 and the cloth is wound on to a rotatable roll 15 driven by a motor 17 while the web of stock 9 falls by gravity into a dip or festoon, a measured amount of stock being delivered on each cycle of operation of the machine and automatically by an electronically-actuated measuring unit, or visually and manually with well-known measuring instruments. A counting plate 23 and a wheel 26 driven by the web 9 as the latter passes over a roller 20, has a number of spaced openings 27 through which a beam of light passes to a photocell which actuates an adjustable electronic counter 28 arranged to control the motor 17 or stop the motor after delivery of a measured length of web 9. To prevent overrunning, brakes are provided in the roll 11 and the motor 17. The mandrel positioning unit 4 serves to fix the space relationship between the seamforming device and the mandrel M and includes a mandrel supporting cradle 30 comprising cradle arms 31, 32 joined by cross-bars 33, 34 and pivoted on a cross-shaft 35. An actuator bar 36 has secured thereto the piston rod 38 of a pivoted, hydraulic piston-cylinder unit 39. The arms have end stops 40 for arresting movement of the covered mandrels as the latter roll down the cradle, and also mounted on the shaft 35 is a cradle support 41 which includes a pair of arms 42 connected by cross tubes 44, 45 and transverse mandrel supporting braces 46, the support being connected to the forward end of the cradle 30 by bolts 48 around which are disposed compression springs 51 to yieldingly hold the cradle and cradle support together for elevating movement in unison; a slight yielding movement of the cradle 30 downwardly with respect to the cradle support 41 facilitates rupture of the finished tube from the trailer ribbon and ejection of the mandrel such movement being effected by actuation of the unit 39. Adjustment of the mandrel supporting cradle 30 with respect to the seaming knife unit 6 is accomplished by attachment of the cross-shaft 35 to blocks 53 which receive elevating screws 54 rotatable through gearing and by a reversible electric motor 55. An index of the position of the mandrel supporting cradle 30 is provided by an index wheel 63 having pinned to the hub thereof a pinion in mesh with a rack 65 attached to block 53 and rotated upon movement of the block. A pointer 71 on the housing of the wheel 63 co-operates with indicia on the surface of the wheel. The blocks 53 may also be adjusted by a handwheel 76. The seam-forming mechanism 6 comprises a fixed knife 79 and a movable knife 81 clamped to a holder 82 and actuated by a hydraulic piston-cylinder unit 84. Associated with the knife 79 is a stock-clamping bar 89 which engages the trailer portion of the stock disposed in engagement with the knife and is pivotally attached to actuators comprising doubleacting piston-cylinder units 90 which bring the bar into a clamping position or remove the bar from such position. The trailer ribbon extracting mechanism, Fig. 6, consists of a co-operating idler pinch roll 105 movable towards and away from a driven roll 104, an indexing motion or rotary motion being given to the roll 104 on each cycle of operation of the machine to bring fresh stock in position over the knife 79. The indexing mechanism includes a ratchet 108 keyed to the shaft of the roll 104 and a pawl 109 pivoted to a slide plate 110 and urged upwardly by a spring 115. A spring-loaded dog 117 prevents reverse rotation of the rachet wheel. The slide is actuated by a doubleacting, pneumatic piston-cylinder unit 120, and a cam plate 122 actuates switches 123, 124 which control the movement of the units 90, 120. Operation of the unit 120 causes the panel 109 to successively engage the teeth of the rachet wheel 108 to rotate the latter, and advance the trailer ribbon, a stop 116, in the retracted position of the unit, being brought into a tooth-engaging position to prevent rotation of the wheel in a direction to advance the trailer ribbon. Mandrel guiding shoes 125 are provided and these have detents 126 to hold a mandrel 127 in position ready for use; safety devices prevent accidental movement of the knife 81 during mandrel positioning. In operation and during movement thereof, the knife 81 engages the stock 9 in the festoon and wraps the stock around the mandrel M and as closing movement of the knives continues the stock between the seaming surfaces of the knives is extruded upwardly and downwardly so that a close seam 128 is formed and a seam 129 where the web of stock 9 meets and is joined to the trailer ribbon 106, the latter being made up of short sections of stock joined or seamed together.