Patent GB-490305-A (GB)
Title: Improvements in material feed control mechanism
IPC: B65B41/18
Filed: 1937-02-27
Abstract: 490,305. Photo-electric control of web-feeding mechanism. FITZGERALD, A. S. Feb. 27, 1937, Nos. 5956 and 5957. Convention dates, Feb. 27, 1936 and Sept. 19, 1936. [Class 40 (iii)] [Also in Groups XXXV and XVI] Relates to apparatus for use in packaging and like machines, particularly for severing predetermined lengths of paper, metal foil, &c. According to the invention, the rate of feed of a web, such as a paper strip, relatively to a web-treating device (e.g. a cutter) is controlled by the co-operation of indicia on the web with means which respond to a change of phase relation between the indicia and the web-treating device, the responsive means automatically starting a motor to increase or decrease the rate of feed as required, and control means being provided to stop the motor when necessary to prevent the automatic increase or decrease of the rate of feed from exceeding a predetermined amount. Secondary control means are also provided for adjusting the predetermined maximum or minimum rate of feed. The invention is shown as applied to a machine for feeding to a severing-device a web or strip of paper or other wrapping material having designs thereon at regular intervals, the feed-mechanism being so controlled that the strip is cut between the designs. The web 1 is drawn intermittently from a supply roll 2 braked by a frictionally - controlled roller 36, and passes between cutting blades 43, 44, the blade 43 being reciprocated by the action of a cam 50 on a shaft 9. This shaft drives Geneva stop mechanism 7 which intermittently rotates a shaft 6 carrying a feed-roller 4. A co-operating roller 5 of rubber or the like is mounted on a shaft 13 which is driven from the shaft 6 by gears 11, 12. The shaft 13 is mounted at one end on a rocker bearing 14 supported on pivots 15, and is adapted to be tilted so as to vary the compression of the roller 5 and thereby to vary the speed at which the web 1 is driven. For this purpose, the other end of the shaft is journalled in a bearing block 18 which is adapted to be raised or lowered in a yoke 20 by means of a screwed rod 23 threading into a bushing on a shaft 25. This shaft is rotatable in either direction by a motor 51 having split-series field windings 52, 53. When the winding 52 is energized, the consequent rotation of the shaft 25 increases the pressure of the feed roller 5, so that the rate of feed of the web is increased ; conversely, when the winding 53 is energized, the rate of feed is decreased. The shaft 25 is geared through a worm 136 with a wheel 125, Figs. 2 and 3, the hub 124 of which has an arm 123 carrying a block 122 in which segmental tappets 120 are adjustably mounted. These tappets coact with rollers on a rocker 111 to operate blade contacts of " limit switches " 64, 84 (for the purpose described below), the rocker 111 being pivoted on an arm integral with a body 70, which carries the switch blades, and which is mounted on the same spindle as is the wheel 125. A circuit is made from supply mains 61 to either of the windings 52, 53 through relay contacts 55, 57 respectively, and through either of the limit switches 64, 84, the relay armature being operated by a valve 100 under the control of a photo-electric cell 105. The cell receives light reflected from the web, which is provided with a series of indicia in the form of black markings 108. These are so located that when the web comes to rest with the leading edge of a mark 108 just entering the narrow light beam concentrated on the web, the latter is correctly placed for the operation of the cutters 43, 44. When the web is of metal foil or other material giving specular reflection, instead of forming the indicia as uniform black spots, it is preferred to form them as pigmented opaque markings having two adjacent fields 203, 204, one dark and one light, as shown in Fig. 9. In the operation of the machine, the feed roller is automatically adjusted so that the rate of feed of the web tends to be either slightly greater or slightly less than that required. Thus the " kinematic image " of the design on the web always tends to have either a forward creep or a backward creep. When conditions are such that the intermittent stopping of the paper brings a dark mark 108 to rest in the spot of light falling on the web, the cell 105 operating through the valve 100 causes the contact 57 of the relay 60 to be closed ; conversely, if the paper comes to rest before a black mark has entered the light spot on the web, the contact 55 is closed. A condenser 110 of large capacity is connected in parallel with the relay 60 to prevent the relay from following the intermittent action of the paper. Assuming that when the machine starts the contact 55 is closed: a circuit is then completed through the limit switch 64 and through the winding 52 of the motor 51, whereby the direction of rotation of the motor is such as to increase the rate of feed of the web and to rotate the tappet-block 122 clockwise. When 122 has moved sufficiently to effect the opening of the switch 64, the motor 51 stops, after having brought about such an increase in the pressure between the feedrollers 4, 5 that the web has a " forward creep." As a result, the light spot is shortly afterwards eclipsed by the black marks 108, and this causes the contact 57 to close. The motor thereupon starts again, but in the reverse direction, the circuit being this time through the switch 84 and the winding 53. The tappetblock 122 is rotated counterclockwise (preparing the switch 64 for the next reversal of the motor) until it opens the switch 84 and stops the motor after a " backward creep " of the web has been established. When, as the result of this creep, the light spot on the web is no longer eclipsed by the markings 108, the relay 60 is operated again, shifting the contact 58 from 57 to 55, and the described cycle of operations begins again. An automatic brake 196 prevents over-running of the motor 51. Under certain conditions, the limits of movement of the tappet-block may be insufficient to cause enough change in the pressure of the feed roll 5 to reverse the direction of creep. A secondary control means is therefore provided, whereby the body 70, carrying the limit switches 64, 84 is automatically adjusted so as to set the switches in the correct position relatively to the tappets. For this purpose, the body 70 is made integral with a worm wheel 141 geared to a worm 140 which is adapted to be driven by a reversible motor 137. The field windings 163, 166 of this motor are energized as required under the control of switches 157, 158 which are actuated by coiled differentially operating bimetallic strips 152, 153 to which currents are supplied through transformers 150, 151 respectively each time one or other of the limit switches 64, 84 is operated by a tappet. The circuits through the primaries of the transformers are made through auxiliary contact blades on the limit switches. The arrangement is such that if the forward and rearward " creep " of the paper are substantially equal, the switches 157, 158 remain open, since the heating effects of the currents in the bimetallic strips are alike. If, however inequality arises, one or other of the switches 157, 158 closes, and the motor 137 runs in one direction or the other, adjusting the position of the limit switches. Normally-closed switches 164, 167, adapted to be opened by means associated with the body 70, form a safety-device to prevent over-running of the motor 51. Push-button switches 175, 176 are provided to enable the duration of running of the motor 51 in either direction to be increased at will, if this is necessary by reason of the paper being threaded with the design considerably out of register at the start. Operation of the push-buttons 175, 176 in this way provides for manual " framing " of the design by acceleration of the backward or forward creep as required. Push-button switches 180, 181 are also provided for manual adjustment of the gear 141 when the machine is started. Signal lamps 172, for supervising purposes, are connected as shown. In a modification, Fig. 8 (not shown), relay-operated contacts are arranged in parallel with the switches 175, 176, one or other of the relays acting automatically each time the corresponding thermostatic switch 157 or 158 closes. With this arrangement, a rapid correction is automatically effected if a sudden displacement from register of the web appears. A further modification is described, Figs. 10-14 (not shown), in which, instead of using electrical means such as the switches 175, 176 for " framing " the design, mechanical means are employed. This mechanism is described in Specification 490,342, [Group XVI].