I. BACKGROUND OF THE INVENTION
A. Field of Invention
This invention relates to methods and apparatuses for drawing wire and more specifically to methods and apparatuses for controlling the speed and torque of the drawing blocks used on a wire drawing machine.
B. Description of the Related Art
It is know to draw wire through multiple dies at multiple die positions of a wire drawing machine. The hardness of drawn steel wire results from the plastic deformation associated with the drawing process. The wire increases in hardness as it proceeds through the wire drawing machine. If the wire becomes too hard or brittle, breakage occurs during the drawing process or when the wire is subjected to torsion or bending.
As the wire is drawn through a die to reduce the cross sectional area, the outer fibers of the wire flow faster or at a higher velocity than those in its center. This flow velocity variation causes a lesser amount of elongation at the center of the wire than at the surface of the wire. A stress differential resulting from this mechanism of elongation induces compressive, longitudinal stresses on the surface of the wire and tensile, longitudinal stresses at its center. Voids, known as central bursts, can occur in the center of the wire when the tensile stresses exceed the breaking strength of the material. The central burst effect can be prevented by controlling the process geometries.
Strain introduced into the wire by the drawing process increases the tensile strength of the wire. Preferably, this increase is held constant at every die of the draft in a wire drawing machine. Analyses of the formation of central bursts show that bursting is more likely to occur if the increase in tensile strength remains low. Therefore, the wire is generally drawn through a draft of many dies each having a geometry to avoid the central burst zone.
Generally a drawing capstan or drawing block is used juxtaposed to each die in order to draw or pull the wire through the corresponding die. A well-known problem in the field of wire drawing machines is the problem of slip. Slip is the difference in the speed of the wire versus the tangential speed of the drawing block that the wire is traveling on. If slip is not properly controlled, both wire properties as well as the wire drawing machine can be damaged.
It is well-known to provide a drive system for use in rotating the drawing blocks of a wire drawing machine. Typically, one motor is used to drive multiple drawing blocks. Such a design generally works well for its intended purpose. The problem, however, with this type of drive system is that slip at each drawing block cannot be carefully controlled. One attempted solution to this problem is to provide one motor for each drawing block. In this way, the speed and torque at each drawing block can be carefully controlled thereby controlling slip. The problem with this solution, however, is the expense of providing all the required motors. It is well-known, for example, to use twenty (20) or more drawing blocks which would require twenty (20) or more motors.
What is needed is a method and device to accurately adjust the rotational condition of each drawing block without the need for multiple motors.
II. SUMMARY OF THE INVENTION
According to one aspect of this invention, a wire drawing machine comprises: (1) a frame; (2) at least a first die operatively supported by the frame; (3) at least a first drawing block rotatably supported by the frame for use in drawing wire through the first die; and, (4) a motor for use in providing power to rotate the first drawing block. Drive means is also provided and operatively connects the motor to the first drawing block. The drive means can be selectively adjusted to drive the first drawing block at a first rotational condition and can also be adjusted to selectively drive the first drawing block at a second rotational condition.
According to another aspect of this invention, a method of adjusting the rotational condition of a first drawing block on a wire drawing machine is provided. This method comprises the steps of: (1) providing a wire drawing machine as described above; (2) driving the first drawing block at a first rotational condition; (3) adjusting the drive means; and, (4) driving the fist drawing block at a second rotational condition.
One advantage of this invention is that the slip can be easily controlled at each drawing block.
Another advantage of this invention is that the slip can be controlled while using only a minimum number of motors.
Still another advantage of this invention is that the rotational condition, such as speed and torque, at each drawing block can be easily adjusted as required for the specific wire being drawn.
III. BRIEF DESCRIPTION OF THE DRAWINGS
The invention may take physical form in certain parts and arrangement of parts, a preferred embodiment of which will be described in detail in this specification and illustrated in the accompanying drawings which form a part hereof and wherein:
FIG. 1 is a perspective front view of a wire drawing machine according to this invention showing two banks of wire dies and drawing blocks.
FIG. 2 is a perspective back view of the wire drawing machine of FIG. 1 with a back panel removed to show the drive system used to rotate the drawing blocks and partially in schematic form to show the motors.
FIG. 3 is a schematic representation illustrating the drive system of this invention.
FIG. 4 is a close up view similar to that shown in FIG. 2 showing the drive means used to operatively connect the motor to the drawing blocks.
FIG. 5 is a schematic representation illustrating the preferred belt system used with the drive system of this invention.
IV. DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings wherein the showings are for purposes of illustrating a preferred embodiment of the invention only and not for purposes of limiting the same, FIGS. 1-2 show front and back views of a wire drawing machine 10 according to this invention. While the wire drawing machine shown is intended for the drawing of “fine” wire, typically referred to as a fine wire drawing machine, it should be noted that this invention can have a wide range of applications including other types of wire drawing machines. The particular wire drawn according to this invention can be any type chosen with sound engineering judgment.
With continuing reference to FIGS. 1-2, the wire drawing machine 10 includes a frame 12 and a dividing wall 14 that separates the front 16 (seen in FIG. 1) from the back 18 (seen in FIG. 2). Preferably, one drawing block 70 is used to draw wire through each wire die 50. The various dies 50 and drawing blocks 70 can be seen in FIG. 1 on the front 16 of the wire drawing machine 10. The preferred wire drawing machine 10 includes two banks of dies and blocks 50, 70 where the top bank is labeled A and the bottom bank is labeled B. Reference 50 is used to refer to the dies generally whereas the same reference 50 with an additional letter, such as 50a, 50b, 50c, etc., is used to refer to individual dies. Similarly, the drawing blocks are labeled 70 generally whereas the same reference 70 with an additional letter such as 70a, 70b, 70c, etc., is used to refer to individual drawing blocks. The wire drawing machine 10 shown in the FIGURES is a wet wire drawing machine and thus includes a channel 40 to hold a liquid lubricant that submerges the dies and wire as it moves through the dies 50 and drawing blocks 70. The general operation of the dies 50 and drawing blocks 70 of this invention are conventional and thus will not be described further.
With reference now to FIGS. 2-4, a drive system 100 used to rotate the drawing blocks 70 so that wire is drawn through the dies 50 will be described. Preferably the drive system 100 includes first and second motors 80, 82 as shown. It should be understood that the number of motors required with this invention can be optimized based on motor performance rather, than the number of drawing blocks 70 and can be one single motor. In the embodiment shown, the first motor 80 is used to provide power to the top bank A of drawing blocks and dies while the second motor 82 is used to provide power to the bottom bank B of drawing blocks and dies. Preferably, the first motor 80 is the “master” motor while the second motor 82 is the “slave” motor. The master motor 80 is used to control the final speed of the wire through the wire drawing machine 10. The slave motor 82 adjusts to the master motor 80 so that the wire is processed through the dies in a manner that will correspond to the desired final wire drawing speed.
With continuing reference to FIGS. 2-4, the drive system 100 also includes drive means 120 that operatively connects the motors 80, 82 to the drawing blocks 70. More specifically, a first drive means 120a operatively connects the second motor 82 to the first drawing block 70a, a second drive means 120b operatively connects the second motor 82 to the second drawing block 70b, a third drive means 120c operatively connects the second motor 82 to the third drawing block 70c, etc. In the preferred embodiment, the total number of individual drive means 120 required corresponds to the total number of drawing blocks 70 being rotated. Thus, for example, if the wire drawing machine 10 has thirty (30) drawing blocks 70, then thirty (30) drive means 120 may be used. The first drive means 120a may be selectively adjusted to drive the first drawing block 70a at a first rotational condition chosen with sound engineering judgment. By “rotational condition” it is meant a particular speed and torque supplied to the particular drawing block 70. The first drive means 120a also can be selectively adjusted to drive the first drawing block 70a at any second rotational condition chosen with sound engineering judgment. In fact, any number of rotational conditions are possible for each drawing block as will be described further below. Each adjustment can be made easily and without any need to increase the limited number of motors provided.
Still referring to FIGS. 2-4 but especially FIG. 3, in the preferred embodiment each drive means 120 uses rotational members 150 rotatably connected to shafts as shown and described further below. More specifically, each preferred drive means 120 includes a belt drive system using belts and sprockets (the sprockets serve as the rotational members 150). The preferred belts are timing belts with teeth that engage with corresponding teeth in the sprockets, as shown. In this way the speed of each drawing block 70 can be carefully controlled. It should be noted, however, that this invention would also work well if instead of using belts and sprockets, belts and pulleys were used, or chains and sprockets, or gears that directly intermesh with each other. All that is required is that specific control of each drawing block 70 be provided by the rotational members. Preferably, the first drive means 120a includes a first rotational member 150a (most preferably a sprocket) that is rotatably attached to a first block shaft 156a that is rotatably attached to the first drawing block 70a. Thus, rotation of the first rotational member 150a causes rotation of the first drawing block 70a. The first rotational member 150a is rotated by a first drive shaft 160a via a first belt system 164a that includes first belt 168a and first sprocket 170a. The first drive shaft 160a may be supported for rotation by bearings 169 and is preferably rotated by the second motor 82. The connection between the second motor 82 and the first drive shaft 160a may include a pair of motor sprockets 172a, 172b rotatably connected together with motor belt 174. The motor sprocket 172b may be fixedly connected to the first drive shaft 160a so that rotation of the motor sprocket 172b will cause rotation of the first drive shaft 160a. The particular sizes used for the motor sprockets 172a, 172b and motor belt 174 can be chosen with sound engineering judgment to optimize the size and number of motors required for the entire wire drawing machine 10. This is an improvement over known machines that require a separate motor for each drawing block in order to individually control the rotation of each drawing block.
With reference to FIGS. 3 and 5, the first rotational member 150a will provide a first rotational condition, a specific speed and torque, to the first drawing block 70a. To change the first rotational condition of the first drawing block 70a, it is only necessary to replace the first rotational member 150a with a second rotational member. In the preferred embodiment, the second rotational member is a second sprocket having a different diameter and/or a different number of teeth. If the first belt system 164a includes only first belt 168a and first sprocket 170a, as shown in FIGS. 2 and 4, then replacing the first rotational member 150a with the second rotational member will also require replacing the first belt 168a with a second belt having a different but corresponding length. In a second and preferred embodiment shown in FIG. 5, however, the first belt system 164a also includes an idler member 178, such as an idler sprocket. The idler member 178 is preferably biased using biasing means such as a spring 180 in a conventional manner to maintain tension in the first belt system 164a. In this case, replacing the first rotational member 150a with the second rotational member requires first that the idler member be pivoted to take tension out of the first belt 168a so that the first belt 168a can be removed from the first rotational member 150a. The first rotational member 150a is then removed and the second rotational member is attached to the first block shaft 156a. The same belt 168a can then be used even though the second rotational member may have a different diameter than the first rotational member 150a. The biased idler member 178 will take up more or less tension as required.
With reference now to FIGS. 2-5, preferably, the second drive means 120b includes a first rotational member 150b (most preferably a sprocket) that is rotatably attached to a first block shaft 156b that is rotatably attached to the second drawing block 70b. Thus, rotation of the first rotational member 150b causes rotation of the second drawing block 70b. The first rotational member 150b is rotated by a first drive shaft 160b via a first belt system 164b that includes first belt 168b and first sprocket 170b. The first drive shaft 160b is preferably rotated by the second motor 82. The connection between the second motor 82 and the first drive shaft 160b preferably includes a pair of drive sprockets 190a, 190b rotatably connected together with drive belt 194. The drive sprocket 190b may be fixedly connected to the first drive shaft 160a so that rotation of the motor sprocket 172b will cause rotation of the first drive shaft 160a and first drive shaft 160b. The particular sizes used for the drive sprockets 190a, 190b and drive belt 194 can be chosen with sound engineering judgment.
With continuing reference to FIGS. 2-5, preferably, the third drive means 120c includes a first rotational member 150c (most preferably a sprocket) that is rotatably attached to a first block shaft 156c that is rotatably attached to the third drawing block 70c. Thus, rotation of the first rotational member 150c causes rotation of the third drawing block 70c. The first rotational member 150c is rotated by a first drive shaft 160c via a first belt system 164c that includes first belt 168c and first sprocket 170c. The first drive shaft 160c is preferably rotated by the second motor 82. The connection between the second motor 82 and the first drive shaft 160c preferably includes a pair of drive sprockets 200a, 200b rotatably connected together with drive belt 204. The drive sprocket 200b may be fixedly connected to the first drive shaft 160c so that rotation of the motor sprocket 172b will cause rotation of the first drive shaft 160a and first drive shaft 160c. The particular sizes used for the drive sprockets 200a, 200b and drive belt 204 can be chosen with sound engineering judgment. It should be understood that the same system of belts and sprockets can be used with multiple drawing blocks so that a single motor can provide power for each drawing block. Nonetheless, because each first rotational member can be replaced, ultimate control of each drawing block can be achieved.
Having thus described the invention, it is now claimed:
Patent Application
20060090532
