Advancing material of indeterminate length – By orbitally traveling material-engaging surface – Comprising rotary pinch pair
Patent
1984-11-13
1986-12-16
Gilreath, Stanley N.
Advancing material of indeterminate length
By orbitally traveling material-engaging surface
Comprising rotary pinch pair
226176, 226190, B65H 5110
Patent
active
046291059
DESCRIPTION:
BRIEF SUMMARY
The invention relates to apparatus for longitudinally driving a rigid wire which is driven by two wheels between which it is pressed.
Apparatus of this type is already known, in particular for driving metal wires through numerous machines, for example machines for bundling various articles which are bound together by a taut metal wire which is subsequently knotted by twisting its ends together.
The wire is driven by the friction which exists between the wire and the groove of a drive wheel into which it is pressed by a pressure wheel. In order to avoid any risk of the drive wheel skidding on the wire, the wire is pressed by the pressure wheel using a force which is greater than the product of the drive-resisting force multiplied by the coefficient of friction of the wire in the groove of the drive wheel. Since the drive-resisting force is variable, its maximum expected value is used for establishing the force to be applied by the pressure wheel. As a result the apparatus frequently operates with too much pressure wheel force, thereby reducing efficiency and causing more rapid wear of the parts.
The main aim of the invention is to provide apparatus for driving a taut rigid wire between two wheels in which the pressing force exerted by the pressure wheel is constantly maintained at the necessary value for properly driving the wire.
Apparatus for driving a rigid wire comprises a pressure wheel mounted to rotate freely on a frame; a driven wheel locked to rotate with a grooved wheel co-operating with the pressure wheel is mounted to rotate freely on the same frame, a motor unit including a drive pulley is supported by the frame, a belt connects the drive pulley and the driven pulley of the grooved wheel, a resilient member exerts a force on the pivot arm tending to bring the grooved wheel closer to the pressure wheel in correspondance with a minimum value of the pressing force exerted by the pressure wheel on the grooved wheel.
In accordance with the invention, the driven pulley and the grooved wheel are mounted on a arm pivoting freely relative the frame, and the motor unit is supported by a parallelogram articulated relative to the same frame. In addition, an actuator is disposed between the motor unit and a fixed point of the frame to act to move the pressure wheel and the grooved wheel closer together and further apart. The pressure chamber of this actuator is connected via a channel to a slide valve which is connected to a hydraulic circuit for fluid under low pressure and to a hydraulic circuit for fluid under high pressure. A slide mounted in the slide valve is capable of occupying a first end position putting the actuator in communication with the low pressure fluid circuit, a second end position putting the actuator in comunication with the high pressure fluid circuit, and a neutral intermediate position isolating the actuator from both of the circuits. The slide is urged form one of ends by a relatively weak constant force pressing its opposite end against the axis on which the driven pulley is mounted.
In an equilibrium operating position of the assembly, for driving a wire of given diameter between the wheels, the slide is pressed against the axis of the driven pulley while being in its neutral intermediate position. In this state the pressure of the fluid in the actuator chamber is the pressure which corresponds to the just sufficient belt tension for suitably clamping the driven wire between the grooved wheel and the pressure wheel.
Any variation in the diameter of the wire corresponds to a a relative displacement of the grooved wheel relative to the pressure wheel, together with a displacement of the slide in the slide valve towards one of its end positions. As a result, the actuator receives or looses fluid and the motor unit moves relative to the frame until the slide returns to its neutral intermediate position. Thus, the assembly comprising the motor unit, the driven pulley and the grooved wheel is moved relative to the frame, and thus relative to the pressure wheel, while the distance betwe
REFERENCES:
patent: 3093285 (1963-06-01), Leaming et al.
patent: 3396888 (1968-08-01), Rygiol
patent: 3657940 (1972-04-01), Wagner
patent: 3675837 (1972-07-01), Gerould
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