Patent GB-365602-A (GB)
Title: Improvements in or relating to web tensioning and controlling mechanism for printing machines and the like
IPC: B65H23/08
Filed: 1930-10-22
Abstract: 365,602. Feeding webs. HOLMES & CO., Ltd., J. H., North Drive, Hebburn-on- Tyne, TAYLOR, H., 52, Eastlands, and GIBSON, W., 47, Roman Avenue, Walker, both in Newcastle-on-Tyne. Oct. 22, 1930, Nos. 31697/30, 614/31, and 1494/31. [Class 100 (i).] In a web-tension controlling mechanism for a printing &c. machine of the kind in which braking belts or aprons engaging the surface of the roll are anchored at one end and wound at-their other ends on a drum which is rotatable to vary the braking effort, the drum is connected to its spindle by a spring and the spindle is turned by an electric motor to vary the stress in the spring. Means may be provided to increase automatically the pressure of the brake belts on the roll upon stoppage of the press and to reduce automatically the braking pressure to a predetermined amount when the press speed is reduced for a web-renewing operation. The drum A, Fig. 1, to which the ends of the braking belts A<3> are secured, is loose on its spindle B and driven therefrom by a coiled spring C attached at one end to the drum and at the other end to the spindle. The spindle may be driven in either direction by an electric motor D through worm gearing D<1>, D<2> and the motor may be controlled in any suitable manner. In one form of control, Fig. 3, employing a three-wire direct current supply circuit H<1>, H, H<2>, the armature D3 of the motor D is connected on one side to the wire H and on the other side, through a normally closed contact J<1>, with the arm K of a manually controlled switch located at any suitable control point. The arm K cooperates with a number of contacts K<1> .. K<11> and is held in position by a roller L<2> carried by a spring-pressed arm L and engaging the teeth of a star-wheel L<3>. The contacts K<1> . . K<11> are connected respectively to contacts M<1> . . M<111> of a second controller comprising an insulated disc M carrying two arcuate contacts N, N<1> each capable of contacting all but one of the contacts M<1> .. M<11> and separated by insulating strips N<2>, N<3>. The strips N, N<1> are connected to the line wires H<1>, H2 and the shaft of the disc M is connected through reducing gear to the shaft of the armature D<3>. The arrangement is such that upon moving the arm K to any of the studs K<1> .. K<11> a circuit is completed through the corresponding stud M<1> . . M" and coacting strip N or N<1> and the motor D is driven to effect a corresponding increase or decrease of the braking effort of the belts A3 and at the same time turns the disc M in such a direction as to bring the strip N<2> into contact with the particular stud M<1>. . M<11> in circuit so as to break the circuit and bring the motor D to rest. The position of the arm K thus gives a visual indication of the web tension and the contacts K<1> .. K<11> may be calibrated to indicate the pressure in pounds &c. The tension of the belts A3 may be automatically reduced to a predetermined value when the machine is .driven at slow speed for web-renewing or other purposes. To this end, the armature D<3> is connected through a normally open contact J2 with a contact M<9> corresponding to the desired reduced web tension. The contacts J<2>, Jl are controlled by a relay J in circuit with two normally open contacts P, P<1> adapted respectively to be closed upon stopping the highspeed motor of the machine and starting the slow-speed motor. Thus, when the machine is running at slow speed the relay J is energized, opening the switch J<1> to cut out the handcontrol K and closing the switch J<2> to establish a circuit through the armature D<3> and contact M<9>. The belt tension is thus reduced and the circuit to the motor opened by the strip N2 engaging the stud M<9>. Upon bringing the machine again to high speed, the contacts P, P<1>, J<2> are opened and the contact J<1> closed and the motor D<3> restores the belts to the original tension corresponding to the setting of the arm K. The pressure of the belts on the roll may be greatly increased upon stoppage of the machine, by positively turning the drum A by means of a pawl E, Fig. 1, adapted to engage a friction surface A<6> on the drum. The pawl is pivoted to an arm E<3> loose on the drum shaft B and is actuated by a solenoid F<2>, Figs. 1 and 3, which may be excited automatically when the press is stopped. For this purpose, the circuit of the solenoid contains a contact R<3> held open by a normally excited relay R the circuit of which contains a contact R<1> and a " stop " pushbutton R<4>. When the button R<4> is pushed and released, the relay R is deenergized allowing the contact R<3> to close to operate the solenoid F<2>, and opening the contact R<1> and also a contact R<3> which causes the stoppage of the machine. When the machine is stopped the main controller returns to the " start " position, closing a contact P<2> which closes a circuit through the relay R to open the contact R<3> and close the contacts R<1>, R<2>. In a second form of control for the motor D, the motor armature D<5>, Fig. 5, is in series with two oppositely wound fields D<6>, D<7> in circuit respectively with limit switches S, S<1> and pushbutton switches T, T<1>, the switch T serving to increase the belt tension and the switch T<1> serving to reduce it. The limit switches serve to prevent excessive increase or reduction in the belt tension by opening the circuit to the motor and are actuated by a pin projecting from a nut B<3> on the screwed extremity of the drum shaft. The automatic reduction of belt tension upon slowing down the press is effected by two relays V, W and two limit switches S<2>, S<3> operated by a second pin on the nut B<3>. The switch S<2> is held open by the pin when the belts are at their normal running tension and the switch S<3> is adapted to be opened when the tension of the belts is reduced to slow-speed requirements. Contacts P, P<1> controlled similarly to the contacts P, P<1> of Fig. 3 normally break the circuits of the relays V, W but when the machine is running at slow speed, these contacts are closed, energizing the relays to close contacts V<2>, W<1>, W<2> and open contact V<1>. A circuit is thus established through the limit switches S3, Sl and field D<7> and the motor is driven to reduce the belt tension until the opening of the limit switch S3 by the nut B3. Instead of employing a pawl E for applying the increased belt tension upon stopping the press, means may be provided to lock the spindle B to the drum A and operate the motor D to effect the turning of the drum, and, in a control arrangement such as shown in Fig. 5, a motor having a single field winding and two armatures or armature windings may be employed. The handle K, Fig. 3, or the pushbuttons T, T<1>, Fig. 5, may be arranged to be operated automatically by the movements of a spring-controlled roller engaging the web, a clutch being provided to permit of independent manual operation.