Patent GB-1240564-A (GB)
Title: Friction welding apparatus
IPC: B29C65/00
Filed: 1969-02-10
Abstract: 1,240,564. Seaming non-metallic sheet material. FMC CORP. 10 Feb., 1969 [21 March, 1968], No. 7108/69. Heading B5K. Apparatus for friction welding two thermoplastic parts 14<SP>1</SP>, 14<SP>11</SP>, Fig. 6, e.g. overlapping end portions of a loop of thermoplastic strapping tensioned about an object, comprises a device 22, Fig. 2, for gripping one of the thermoplastic parts and rubbing it against the other, rotatable drive means for the device 22 comprising a pair of relatively movable parts 32, 38 which, in a first relative position, hold the device 22 and the thermoplastic part gripped thereby in alignment and, in a second relative position, effect movement of the device 22 to rub the thermoplastic part gripped thereby against the other part, and means operating in response to the rotation of the drive means for shifting the parts 32, 38 from the first position to the second position. The apparatus comprises a serrated-edge dog 12, Fig. 1, to hold the strapping 14 against a base 10, a tensioning mechanism 16 operated by a lever 18, a sealing head 20 and a cutter (not shown) to sever the tensioned strap from the supply.  The head 20, Fig. 2, comprises a cylindrical device 22 carrying a pad 28 directly above a pad 30 mounted in or on the base 10. The drive shaft 32 of an electric motor 34 has a sleeve 38 secured thereto and extends into the device 22. The sleeve 38 has a cylindrical bore 40 of larger diameter than the shaft 32 and a cylindrical outer periphery which is eccentric with respect to the bore 40. A needle bearing 44 is mounted between the device 22 and the sleeve 38 which is rockable about a pin 42, Fig. 4. A member 48 fits into a groove 50 in the shaft 32 and into a notch 46 in the sleeve 38. With the member 48 in the position of Fig. 4, the sleeve 38 is positioned so that its outer periphery is concentric with the shaft 32 so that the sleeve 38 and the shaft 32 can rotate freely within the device 22 without moving the device. If the member 48 is shifted so that the sleeve 38 is rocked about the pin 42 so that its outer periphery is eccentric with respect to the shaft 32, Fig. 5 (not shown), rotation of the shaft 32 and the sleeve 38 imparts an orbital motion to the device 22 with the centre line of the shaft 32 at the centre of motion of the device 22. For operating the member 48 so as to locate the sleeve 38 in either of its two positions, a weight 54 is secured to the member 48 or is integral therewith. A torsion spring 55 is attached to the weight 54 and to the sleeve 38 and normally holds the member 48 in the Fig. 4 position but when the drive means 32, 38 reaches a predetermined speed, centrifugal force acting on the weight 54 causes the weight to swing outwardly to the second position. Alternatively, the spring 55 may be omitted and the sleeve 38 shifted between its two positions by the force of inertia of the weight 54. A compression spring 60 acts on a collar 58 surrounding the device 22 and carrying balls 64 in sockets 62 therein to engage the base 24 of the device 22. A retainer 66 is secured to the collar 58. To ensure that the device 22 remains stationary when the sleeve 38 is in the Fig. 4 position and to constrain the device 22, when the sleeve 38 is in its second position, to the orbital motion shown in Fig. 6, a member 51 is secured to the base 24 and to a wire (52), Fig. 3 (not shown), and a spring 53. To move the device 22 towards and away from the pad 30, a shifter 74 is pivotally mounted on horizontal pins, e.g. 78, and is pivoted to the collar 58 by pins (80), (82), Fig. 3 (not shown). Arms (84), (86) extend from the body of the shifter 74 and carry a follower 88, Fig. 2, which engages a cam 90 on a shaft 92. Movement of a lever 94 clockwise of Fig. 1 rotates the shaft 92 so that a cutter (not shown) is actuated and a low portion of the cam 90 engages the follower 88 so that the spring 60 moves the collar 58 downwardly. When the strap portions are squeezed between the pads 28, 30, the motor 34 is started to effect the welding. A timer 98, Fig. 1, may be provided to stop the motor 34 after a predetermined time.