Patent GB-681309-A (GB)
Title: Improvements in apparatus for feeding strip material to extrusion machines
IPC: B29C48/09
Filed: 1950-05-19
Abstract: 681,309. Apparatus for extruding rubber &c. WESTERN ELECTRIC CO., Inc. May 19, 1950 [May 29, 1949], No. 12601/50. Class 87 (ii). Relates to feeding materials to extrusion machines and aims to overcome clogging due to the rate of feed being too high for the rate of extrusion; and comprises a driven extruder, a feeding device driven to feed strip material to the extruder, a brake adapted to engage the feeding device so as to prevent its motion, and control means responsive to the quantity of material in the extruder for interrupting the drive to the feeding device and applying the brake thereto when an excess of material is present in the extruder and for releasing the brake and restarting the drive when a normal quantity of material is present. Strip material 8 is fed from a feed roll 24 driven from the extension screw 10 and fitted with a brake 64, 66, and a feeler 50 responsive to feed conditions in the extruder is adapted to operate the control means for interrupting the drive and applying the brake. The feed roll 24 is rigid with a drive ratchet wheel 34 which is engaged by a drive panel 36 mounted on a projection from a collar 40, and an arm 42 on the collar 40 is reciprocated through a rocker 46 from a cam on the shaft of the extension screw. The strip is thus advanced intermittently towards the screw, aided by pins 26 on the feed roll 24 on which the strip is pressed by a roller 30. The feeler 50 is held on an arm pivoted at 82 and extends downwards into a notch 19 which is formed by the space between the wall of the feed throat and a lug 18 on a feed plate 16. When material accumulates in the feed throat it fills the notch 19 and pushes up the feeler and so turns its arm clockwise against the pull of a spring 51. The movement of the arm is transmitted through a link 54 and moves a gear segment 52 clockwise. The gear segment 52 meshes with teeth on a cam 56 and its movement turns the cam counterclockwise and causes it to disengage the pawl 36 from the ratchet wheel 34, so disconnecting the drive of the feed roll 24. The length of feed is controlled by the extent to which the lobe 58 on the cam 56 remains in a position holding up the pawl, so that a variable feed stroke is provided. Although the feed drive is disconnected the extrusion screw still pulls the strip 8 and if the accumulation is such that the feed must be completely stopped a brake must be applied to the feed roll. A brake ratchet wheel 66 is connected rigidly to the feed roll 24 and is engageable by a brake pawl 64, the pawl 64 being held out of engagement, against the pull of a spring, by the cam 56 until this cam has moved so far (owing to excess accumulation and therefore large movement of the feeler 50) that it allows the brake pawl to engage the brake ratchet wheel and positively lock the feed roll 24 against rotation by the pull on the strip 8, so preventing all further feed. The pins 26 prevent the strip from being drawn off the stationary feed roll. As the extrusion screw carries the excess material from under the feeler 50 the feeler drops and the brake is released and the positive feed drive restored. The feeler has a shoe 8 with a sharp edge 76 and another sharp edge at right angles to it which, by scraping against the lug 18 and a wall of the feed throat, tend to keep material off the top of the shoe and to prevent sticking. To deal with any material that may get above the shoe there may be fixed to the feeler a clearer which has inclined surfaces so disposed as to push the material back along the screw.