Festoonless Tire Bead Winding System Technical Field The present invention relates to systems for applying a coating to metal wire and winding the coated wire into a tire bead. More specifically, the invention relates to novel and improved bead winding systems which permit alternate starting and stopping of paying off wire from a supply reel during the winding operation, thereby eliminating the need for the usual vertical festoon which accumulates a supply of wire while the winding drum is stopped between the end of one winding cycle and the beginning of the next.
Background Art In the conventional manner of fabricating tire beads, a supply reel of bare wire is mounted upon a let-off stand for free rotation about a horizontal axis. Wire is pulled from the reel by a motor-driven capstan about which the wire passes after passing through an extruder which applies a rubberized coating to the wire, i. e., the extruder is positioned between the supply reel and the capstan. The capstan operates continuously, at a substantially fixed speed, during the winding operation, although the winding drum which operates to wind the wire into a bead must stop after completion of each winding cycle to permit removal of the completed bead and restarted after preparing for a new cycle. This requires means for accumulating the wire being pulled from the supply reel by the capstan, such means commonly being in the form of a vertical festoon comprising upper and lower pluralities of sheaves, stacked in coaxial, side-by-side relation, about which the wire passes. When the winding drum is in operation, wire is pulled from the festoon by the drum faster than it is supplied by the capstan, thus causing the lower sheave stack to travel upwardly as the accumulated quantity of wire diminishes. Conversely, when the winding drum is stopped, wire accumulates on the festoon and the lower sheave stack travels downwardly.
It is a principal object of the present invention to provide a tire bead winding system, and method of operation thereof, which is both less expensive and requires less physical space than typical prior art winding systems of comparable capacity.
A further object is to provide a tire bead winding system which eliminates the need for a festoon or other wire accumulating means between the extruder and the winding drum.
Another object is to provide a tire bead winding system including novel extruder means for applying a coating to the bead wire in a manner permitting alternate stopping and starting of wire travel through the extruder.
Other objects will in part be obvious and will in part appear hereinafter.
Summary Of The Invention Rather than mounting the wire supply reel for free rotation as wire is pulled off, the winding system of the present invention includes an electric motor for rotating the supply reel to pay off wire. A pair of sheave tacks are mounted on the same frame structure as the supply reel to provide a compact accumulator for a relatively small amount of wire. A line through the axes of the two sheave stacks is at an acute angle to the horizontal, placing one stack at a higher vertical position than the other, although the stacks are not arranged in vertically aligned relation, as in typical prior art festoon apparatus.
The axis of rotation of the sheave stack at the higher elevation is stationary, the axis of the lower sheave stack being linearly movable toward and away from the axis of the other stack. The lower sheave stack is connected to the cable of an air motor, i. e., to opposite sides of the piston of a pneumatic cylinder. A manually operable throttle valve between the source of compressed air and the piston is set so that the air motor exerts a substantially constant force urging the lower sheave stack away from the upper stack, thereby providing a desired wire tension. A potentiometer formed by a stationary strip of conducting metal on the frame
contacted by a wiper arm movable with the lower sheave stack provides a feedback signal which varies the speed of the motor driving the supply reel, paying off wire at a rate tending to keep the lower sheave stack at or near a desired position, such as the center of its range of movement.
From the sheave stacks, the wire travels through extrusion apparatus which applies a uniform thickness of coating material to the wire, and thence directly to the winding drum. The wire is pulled from the extruder by the motor-driven drum, the structure and operation of which are entirely conventional. When the winding drum drive motor is stopped at the conclusion of a winding cycle to permit withdrawal of the finished bead and clamping the new leading end of the wire within the drum, the supply roll drive motor is also stopped. Thus, all wire travel is stopped, including the portion of the wire passing through the extruder. In order to avoid the deposit of excess coating material on this portion of the wire, a unique venting system, forming an aspect of the present invention, is provided for diverting any excess material away from the wire. The respective drive motors for the supply reel and the winding drum are then actuated simultaneously to begin another winding cycle.
The foregoing and other features of construction and operation of the various aspects of the invention will be or are readily understood and fully appreciated from the following detailed description, taken in conjunction with the accompanying drawings.
Brief Description of the Drainas Figure 1 is a partly diagrammatic illustration of the bead winding system of the invention; Figure 2 is a plan view of certain elements seen in phantom lines in Figure 1, i. e., those elements surrounded by the dashed lines indicated by reference numeral 16; Figure 3 is an exploded, perspective view of the elements of Figure 2; and Figures 4 and 5 are elevational views, in section, of
portions of extruder apparatus of the prior art and the present invention, respectively, used in bead winding operations.
Modes For Carrying Out The Invention Referring now to the drawings, the components of the bead winding system of the invention, and their relative relationship to one another, are illustrated in Figure 1.
Supply reel 10 of metal wire of a type suitable for use in tire beads is mounted upon frame means 12. Electric motor 14 is operable to rotate reel 10 in a direction paying off wire from the reel. Also mounted upon frame means 12, in a position generally above reel 10, is accumulator means 16 which receives wire directly from the reel, holding a variable quantity of wire and applying a desired tension thereto, as explained later. From the accumulator means, bare wire 18 passes through extrusion means 20 which applies a layer of rubber, or similar coating materials used in bead-forming operations.
Coated wire 18'is wound upon drum 22, of entirely conventional construction, as the drum is rotated by electric motor 24, pulling wire from accumulator means 16 and through extruder 20. Upon completion of the winding of a complete bead, rotation of both reel 10 and drum 22 by motors 14 and 24, respectively, is stopped while the wire is severed and the completed bead is removed from drum 22, normally by automatic means (not shown). When the new leading end of wire 18'has been clamped in drum 22, rotation of reel 10 and drum 22 is resumed and another bead is wound. Thus, rotation of both reel 10 and drum 22 is started and stopped once during each winding cycle, as opposed to typical prior art systems where rotation of the winding drum is stopped and started during each cycle but wire continues to be drawn from the supply reel and stored on a festoon between the extruder and the winding drum.
The elements of accumulator means 16 are shown in more detail in Figures 2 and 3. A first plurality of pulleys or
sheaves 26 are stacked adjacent one another for rotation about the axis of rod 28 and secured by nut 30. Rod 28 is supported upon, with its axis perpendicular and fixed with respect to, frame member 12a, and is fixedly supported by frame member 12b (Figure 1) upon the other, rigidly interconnected members of frame 12. A second plurality of sheaves 32 are likewise stacked together and mounted upon, for rotation about the axis of, rod 34 and secured by bolt 36. Rod 34 is fixedly connected to channel member 38 which slidingly engages track member 40 which is affixed to frame member 12a by screws 42, the longitudinal axes of elongated track member 40 and frame member 12a being parallel. Thus, the axis of rotation of sheave stack 32 is linearly movable toward and away from the axis of rotation of sheave stack 26 as channel member 38 slides along track member 40.
Pneumatic cylinder 44 is mounted upon frame member 12a, and connected, through manually operable throttle valve 46, to compressed air source 48. Cable 50 passes around pulleys 52, 52'at opposite ends of cylinder 44 and enters the cylinder through suitable seals with opposite ends of the cable affixed to opposite sides of the piston. A portion of cable 50 externally of cylinder 44 is affixed to bracket 54, mounted on rod 34 and connected to channel member 38. Thus, the elements operate in the manner of a so-called air motor, with the air pressure applied to one side of the piston urging it cable 50 and bracket 54, and thus sheave stack 32, in a direction away from sheave stack 26. Electrically conducting bar 56 is supported on frame member 12a, and conducting slide member or wiper 58 is connected to bracket 54 for sliding, electrical contact with bar 56 in response to movement of sheave stack 32, for purposes explained later.
Wire 18 is led from supply reel 10 to sheave 26a, at one end of sheave stack 26, and thence to sheave 32a of sheave stack 32. Wire 18 passes around successive sheaves of the two stacks, and is led from sheave 26b to extruder 20. Thus, the amount of wire 18 held upon accumulator means 16, i. e., the wire passing around sheave stacks 26 and 32, varies with the
accumulator means 16, i. e, the wire passing around sheave stacks 26 and 32, varies with the distance between the two sheave stacks. That is, the amount of wire held or stored on the accumulator means is increasingly greater as sheave stack 32 moves away from sheave stack 26, and vice versa. The wire passing around the sheave stacks is maintained under tension to some extent by gravity and to some extent by the biasing force of the air motor. In other words, by mounting sheave stack 32 for sliding movement at an acute angle to the vertical, the weight of the sheaves and associated, movable elements tend to move sheave stack 32 away from sheave stack 26. Also, the biasing force provided by the air pressure on one side of the piston tends to move stack 32 away from stack 26, this force being selectively variable by operator adjustment of valve 46.
Electrically conducting bar 56 and wiper 58 provide the fixed and movable contacts of a potentiometer, connected in a conventional speed control circuit for motor 14. Operation of the circuit is such that, as sheave stack 32 moves closer to sheave stack 26, thereby varying the resistance of the potentiometer, the speed of motor 14 is increased. This increases the rate at which wire is paid off from reel 10 and, with motor 24 operating at a substantially constant speed, increases the amount of wire held on accumulator means 16, moving sheave stack 32 away from sheave stack 26. This movement, of course, slows the speed of motor 14, eventually moving sheave stack 32 back toward stack 26. Thus, an electrical-mechanical feedback loop tends to maintain sheave stack 32 near the center of its range of movement while accommodating differences in speed and actuation times of the two motors, and other system variables.
As previously indicated, when winding of a tire bead on drum 22 is completed, both motors 14 and 24 are stopped, thereby stopping all wire travel, while the wire is severed, the completed bead is removed, and the new leading end of the wire is clamped in the drum in preparation for a new winding cycle. This would present a problem in the coating operation
using conventional extruding apparatus. As seen in Figure 4, prior art extrusion die 60 has passageway 62 with entry and exit ends 64 and 66, respectively, through which wire 18 is moved, with the coating material deposited thereon. If movement of wire 18 is stopped, the high pressure applied to the coating material within the extruder pushes the material through passageway 62 and excess material, indicated by reference numeral 68, accumulates on the portion of the wire immediately forward of passageway exit end 66, rendering the wire unsuitable for use in the beadmaking process.
This potential problem is overcome by the extrusion die of the present invention, seen in Figure 5 and denoted by reference numeral 70. Die 70 includes passageway 72, of the same cross-sectional configuration as passageway 62. In addition, die 70 has second passageway 74 with first end 76 communicating with passageway 72 between its entry and exit ends 78 and 80, respectively, and second end 82 communicating with the exterior of the extrusion apparatus. Passageway 74 has a cross-sectional area which is constant throughout its length and larger than the maximum cross-sectional area of passageway 72. The central, linear axes of passageways 72 and 74 form an acute angle, preferably about 45 degrees, and the two passageways communicate at a position preferably between about 40% and 60% of the distance between entry and exit ends 78 and 80. With this arrangement, coating material is pushed out through passageway 74 and does not accumulate on wire 18 during periods when the wire is not moving.
From the foregoing, it will be seen that the bead winding system of the invention provides significant economies of occupied space and cost over prior art systems of comparable capacity. In practice, two or more winding lines, sharing a common extrusion apparatus with a plurality of dies, are commonly placed in side-by-side relation and operated in tandem. Motor 14 is preferably capable of accelerating the rate of wire payoff from reel 10 (weighing about 1,000 pounds when full) from 0 to full speed in less than 2 seconds. For example, motor 14 may be 500V DC, 15 horsepower for wire speed of 750 feet per minute, or 20 horsepower for speeds of 1,500 feet per minute.
