Patent GB-1434976-A (GB)
Title: Apparatus for ultrasonic welding of sheet materials
IPC: B29C53/00
Filed: 1973-07-26
Abstract: 1434976 Seaming non-metallic sheet material; laminates CROMPTON & KNOWLES CORP 26 July 1973 [20 Dec 1972] 35730/73 Headings B5K and B5N Apparatus for welding at least two sheets 25, 27, at least one of which contains a thermoplastic material, comprises an ultrasonic electroacoustic converter or transducer 42 to which a resonator 26 having a working surface (24) is connected, anvil means (22), Fig. 2 (not shown), having surfaces (23) for co-operating with the surface (24) to produce welds on the sheets 25, 27, the total contact area between the surfaces (23), (24) varying during operation of the apparatus, means 28, 30 for advancing the sheets 25, 27, means 40 for modifying the total amount of energy transmitted by the resonator 26 to the sheets 25, 27, and control means 68, 70 operatively connected to the means 40 so that energy will be transmitted by the resonator 26 to the sheets 25, 27 at at least two different rates, a relatively high rate for a relatively high total surface area of the surfaces (23), (24) and a relatively low rate for a relatively low total surface area of the surfaces (23), (24). In an embodiment, Fig. 1, a plurality of anvils (22) are arranged in a pattern on a rotatable roll 18 with variations in anvil density along lines extending across the roll surface and parallel to the axis thereof. The converter 42 is fixed to a casing 48 slidably mounted on two diagonally opposite fixed guide rods 50. Fluid pressure actuators 41 comprise two air cylinders 52 having pistons 54 which engage the casing 48 at the two diagonally opposed corners not occupied by the rods 50. Compressed air is supplied through a line 56 to the cylinders 52 and to a bleeder valve 68 having a plunger 72 engaged by a cam 70 which has high and low portions 74, 76 designed to correlate with the anvil density on the roll 18. The pressure within the cylinders 52 increases with greater anvil density and decreases with less anvil density due to decreased or increased bleeding of the valve 68 and thus the force exerted by the resonator 26 against the sheets and the energy transmitted by the resonator is increased or decreased. In a modification (not shown), the valve 68 is replaced by an "on-off" valve which is bled only when the anvil density drops below a predetermined value. In another embodiment, Fig. 4, the resonator 26<SP>1</SP> is supported from a fixed converter 42<SP>1</SP> which is restrained against vertical movement. The patterned anvil roll 18<SP>1</SP> is mounted on a shaft 19<SP>1</SP> supported by arms 78 pivoted on a driven shaft 80 which drives the shaft 19<SP>1</SP> through a drive 82. A cam 70<SP>1</SP> is fixed to the shaft 19<SP>1</SP> and engages a plunger 72<SP>1</SP> of a valve 68<SP>1</SP> which controls the supply of compressed air to cylinders 52<SP>1</SP> having pistons 541 which engage the arms 78 to force the anvils 22<SP>1</SP> on the roll 18<SP>1</SP> against the resonator 26<SP>1</SP>. The pressure within the cylinders 52<SP>1</SP> increases with greater anvil density and decreases with less anvil density.  In a further embodiment, Fig. 6, the converter 42<SP>11</SP> is fixed against vertical movement and the anvil roll 18<SP>11</SP> is mounted on a shaft 19<SP>11</SP> supported on a pair of arms 78<SP>11</SP> pivoted on a shaft 80<SP>11</SP> and which is driven from the shaft 80<SP>11</SP>. A cam 70<SP>11</SP> is mounted on the shaft 19<SP>11</SP> and is engaged by a follower 84 on a plunger 86 urged out of a casing 88 by a heavy spring 90. The pressure of the spring 90 increases with greater anvil density and decreases with less anvil density. In a still further embodiment, Fig. 7, the sheets 92, 93 pass between a resonator 94 and anvils 96 patterned on a rotatable roll 96 driven in timed relation to the sheet feed. The resonator 94 is connected to a converter 106 connected to a control circuit 108 the voltage to which can be controlled by an adjustable transformer 110 connected to a power source 112. The transformer 110 includes a movable tap 114 connected to a follower 116 engaged by a cam 118 rotated with the roll 98. When the anvil density decreases or increases, the tap 114 is shifted to decrease or increase the voltage to the circuit 108 and decrease or increase the energy transmitted from the resonator 94 to the sheets 92, 93.