Abstract:
Disclosed are a control method and a device for a cutter shaped by a helical spring, which comprises two cutter position controlling devices ( 20 ) connected to two spring outer diameter cutters ( 10 ) respectively and comprises a cutter lifting device ( 30 ). The two cutter position controlling devices ( 20 ) are arranged in the same mounting plane ( 40 ). The cutter position-controlling device ( 20 ) controls an amount of displacement of the stretching and retracting of the two spring outer diameter cutters ( 10 ). The amount of displacement of the spring outer diameter cutters ( 10 ) and the amount of up and down movement of the mounting plane ( 40 ) are controlled simultaneously by a motor ( 50 ). By applying the concept of relative coordinates, the requirements of control can be simplified from two two-dimensional control movements to three single-axis linear movements by using the centre (P 3 ) of a spring coil as the origin of the coordinates for the movement of the spring outer diameter cutter. In the case that the distances of linear movement on the three axes are identical or at a fixed ratio, the advantage of reducing the number of motors is achieved.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
       [0001]    The present invention relates to a controlling device, and more particularly to a controlling device for coil spring bending tool and controlling method thereof. 
       2. Description of Related Art 
       [0002]    Device for controlling an outer diameter of a coil spring in a conventional coil spring forming machine has shortcomings of being produced in high cost and difficulty for operation. For example, most advanced countries like US or European normally use multi-axis numerical control motors to control an automatic machine. Japan otherwise uses two numerical control motors to control each coil spring bending tool of the conventional coil spring forming machine. Since at least four numerical control motors were used, an absolute coordinate is therefore adopted to the conventional coil spring &amp;Inning machine. 
         [0003]    The absolute coordinate is engaged of obtaining locations of each coil spring bending tool by calculating trigonometric functions from an absolute origin point. The complex calculation requires a high-end computer to complete and further accomplish by various gearing devices. Especially for producing a coil spring with multiple diameters like hourglass-shaped, olive-shaped or cone-shaped, the numerical control motor sometimes needs to wait for the high-end computer to complete the complex calculation which leads to cost increase and prevents automation of small size coil spring forming machine. 
         [0004]    To overcome the shortcomings, the present invention provides a controlling device for coil spring bending tool to mitigate or obviate the aforementioned problems. 
       SUMMARY OF THE INVENTION 
       [0005]    In order to avoid complex calculation of the conventional coil spring forming machine when forming coil spring with multiple diameters, the present invention provide a controlling device for coil spring bending tool comprising: 
         [0006]    at least two coil spring bending tools for bending a spring wire; 
         [0007]    at least two controlling apparatuses being connected with the at least two coil spring bending tools and being mounted on a assembly platform; 
         [0008]    a lifting apparatus for controlling a height displacement of the assembly platform; wherein: 
         [0009]    the controlling apparatus controls displacements of the at least two coil spring bending tools; 
         [0010]    the displacements of the at least two coil spring bending tools are adjusted according to a radius of a coil spring, the displacements of the at least two coil spring bending tools are proportional to the radius of the coil spring; 
         [0011]    a center point of the coil spring is a virtual reference point; 
         [0012]    the height replacement is the assembly platform being moved by the controlling apparatus from the virtual reference point according to the radius of the coil spring; and 
         [0013]    the height replacement is proportional to the radius of the coil spring. 
         [0014]    According to the above-mentioned features, the present invention has advantages as followings. 
         [0015]    1. The conventional coil spring forming machine was operated by an absolute origin point and an absolute coordinate which leads to complex calculation process. The present invention is able to solve the problem of the conventional coil spring forming machine by using the virtual reference point and relative coordinate for more simple calculation process. The present invention is operated by controlling the displacement of the coil spring bending tools being adjusted according to the radius of the coil spring which leads to more simple and one-dimensional calculation. 
         [0016]    2. Since the controlling method of the coil spring bending tools  10  is simplified, the present invention may be cost down by operating multiple controlling apparatus with one motor through power transmission unit like belt set, gear set or chain set. 
         [0017]    Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a schematic diagram of a controlling device for a coil spring bending tool in accordance with the present invention; 
           [0019]      FIG. 2  is a schematic diagram for showing movements of a bending tool in accordance with the present invention; 
           [0020]      FIG. 3  is a schematic diagram of movements of a controlling device for coil spring bending tool in accordance with the present invention; 
       
    
    
     REFERENCE NUMBERS IN THE DRAWINGS 
       [0000]    
       
           10  coil spring bending tool 
           20  controlling apparatus 
           30  lifting apparatus 
           40  assembly platform 
           50  motor 
           60  cutting assembly 
           61  cutting knife 
           62  cutting board 
           70  wire feeing assembly 
           80  spring wire 
         A initial point 
         P 0  original point of the controlling device of the present invention 
         P 1 , P 2  touch points of coil spring bending tools  10  with the surfaces of the coil spring 
         P 3  coordinate of center point of the coil spring 
         R distance between A with P 1 , P 2   
         R, r radius of the coil spring 
         Z 1 , Z 2  displacement 
         Z 3  height displacement 
       
     
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0039]    With reference to  FIG. 1  and  FIG. 2 , a controlling device for coil spring bending tool of the present invention comprises a wire feeding assembly  70 , a cutting assembly  60 , at least two coil spring bending tools  10 , at least two controlling apparatuses  20 , a lifting apparatus  30 , a assembling platform  40  and a motor  50 . 
         [0040]    The wire feeing assembly  70  comprises two fixed rollers  71  dragging out a spring wire  80  and forwarding the spring wire  80  to the nearby at least two coil spring bending tools  10 . The at least two coil spring bending tools  10  provide a bending force to bend the spring wire  80  into a coil spring. Radius of the coil spring being produced by the present invention is controlled by distances between the at least two bending tools  10  with a virtual reference point. The virtual reference point is a center point of the coil spring. The center point of the coil spring is a crossing point between hypothesis extension lines extended from tough points of the at least two coil spring bending tools  10 . When the distance between the at least two bending tool  10  and the virtual reference point is closer, the radius of the coil spring becomes smaller. 
         [0041]    With reference to  FIG. 1 , after pass through an initial point, the spring wire  80  is firstly bended by the coil spring bending tool  10  being set up at nether of the controlling device of the present invention. The spring wire  80  then is forwarded to the coil spring bending tool  10  being set up at above for bended again to form the coil spring. The coil spring then is cut by the cutting assembly  60  according to a free height of the coil spring. The cutting assembly  60  comprises a cutting knife  61  and a cutting board  62 . The cutting knife  61  cuts the coil spring on the cutting board  62  with the coil spring being fixed thereon. 
         [0042]    Each coil spring bending tool  10  is respectively connected with each controlling apparatus  20 . The at least two controlling apparatuses  20  control the distance between the at least two coil spring bending tools  10  and the virtual reference point to form the coil spring with different radius. The at least two controlling apparatuses  20  are mounted on the assembling platform  40 . A tip of the coil spring bending tool  10  is continually contacted with an outer surface of the coil spring. The distance between the tip of the coil spring bending tool  10  and the virtual reference point is maintained in equidistance so that a displacement of the at least two coil spring bending tools  10  will remain the same while the radius of the coil spring is changing. Aforementioned displacement is an extend or retraced distance of the at least two coil spring bending tool  10  when changing the radius of the coil spring. Moreover, according to a mechanical tolerance or demands of actual use, the displacement of the at least two coil spring bending tools  10  is proportional to the radius of the coil spring. In the first embodiment of the present invention, the controlling apparatus  20  may be but not limited to a screw set, a cam set, a gear set or combination thereof. 
         [0043]    When three coil spring bending tools  10  are used in the second embodiment of the present invention, the third coil spring bending tool  10  may be placed between the first and the second coil spring bending tools  10 . The third coil spring bending tool  10  may provide extra bending force and prevent distortion of the coil spring away from a perfect circle according to material property or radius of the spring wire  80 . 
         [0044]    The lifting apparatus  30  is connected with the assembly platform  40  to adjust a height displacement of the assembly platform  40 . The height displacement is a distance between the assembly platform  40  and ground. The virtual reference point will adjust according to the displacement of the assembly platform  40 . The controlling apparatus  20  controls the height displacement of the assembly platform  40  with respect to an absolute point the present invention. 
         [0045]    With reference to  FIG. 3 , a third embodiment of the present invention is disclosed. The height between the virtual reference point and ground is changing according to the radius of the coil spring when the initial point A was fixed. For example, the height of the virtual reference point is vertically raised as the radius of the coil spring increased. As the height of the virtual reference point being raised, the lifting apparatus  30  will also vertically lift the assembly platform  40  correspondingly. In the third embodiment of the present invention, the controlling apparatus  20  may be but not limited to a screw set, a cam set, a gear set or combination thereof. 
         [0046]    The motor  50  provides electric power to the at least two controlling apparatuses  20  and the lifting apparatus  30 . The electric power may be provided to the controlling apparatuses  20  and the lifting apparatus  30  individually by several motors  50  when applied to large scale machine. The motor  50  may be but not limited to a stepper motor or servo motor. The motor  50  may output mechanical power to the controlling apparatuses  20  and the lifting apparatus  30  by a power transmission unit like a set of a belt, a gear, a chain, a connecting rod or combination thereof. 
         [0047]    In order to simplify whole construction of the present invention and reduce the usage of the motor  50  or its relevant power transmission unit, the motor  50 , the at least two controlling apparatus  20  and the lifting apparatus  30  may connected as desired. For instance, the motor  50  may activate the controlling apparatus  20  and the lifting apparatus  30  respectively through the power transmission unit as the controlling apparatus  20  and the lifting apparatus  30  were working separately. 
         [0048]    The motor  50  may also activate the at least two controlling apparatuses  20  and the lifting apparatus  30  by the following examples. 
         [0049]    The motor  50  may provide power to the at least two controlling apparatuses  20  through the power transmission unit when one of the controlling apparatus  20  is connected and synchronized with the lifting apparatus  30 . 
         [0050]    The motor  50  may provide power to the lifting apparatus  30  through the power transmission unit when the lifting apparatus  30  is connected with a transmission shaft of the motor  50  and synchronized with the controlling apparatuses  20 . 
         [0051]    The motor  50  may provide power to the controlling apparatus  20  that doesn&#39;t connect to the lifting apparatus  30  through the power transmission unit when the controlling apparatus  20  is connected and synchronized with the lifting apparatus  30  and further connected with the motor  50 . 
         [0052]    Moreover, the controlling apparatus  20  and the lifting apparatus  30  may be activated by multiple motors  50  respectively. 
         [0053]    The displacement of the at least two coil spring bending tools  10  and the height displacement of the assembly platform  40  are proportional to the radius of the coil spring. 
         [0054]    With reference to  FIG. 1 , the initial point A defines as a original point P 0  with coordinate (X0=0, Y0=0). Radius of the coil spring defines as R. Touch points of at least two coil spring bending tools  10  with the surfaces of the coil spring define as P 1  and P 2 . The displacements of the at least two coil spring bending tools  10  define as Z 1  and Z 2 . The height displacement of the assembly platform  40  defines as Z 3 . Angle between the at least two coil spring bending tools  10  with a virtual horizontal plane extended from the virtual reference point define as θ. Angle between the at least two coil spring bending tools  10  with a virtual horizontal plane extended from the virtual reference point define as φ. Distance between P 1 , P 2  and the virtual reference point equals to radius R. Coordinate of P 3  is X3=0 and Y3=R. With reference to  FIG. 2  and  FIG. 3 , as R decreases into smaller radius r, the radius of the coil spring, distances between P 1 , P 2  and the virtual reference point, Z 1 , Z 2  and Z 3  will all become to R minus r (R−r). The controlling apparatus  20  will also adjust the at least two coil spring bending tools  10  to maintain angles θ and φ constant. At meanwhile, coordinate of P 3  will become (X3=0, Y3=R−r). Moreover, summation of θ and φ (θ+φ) are less than 180 degree, better between 90 degree to 150 degree. The controlling method disclosed by the present invention will not be effected even though angles of θ and φ may be unequal. 
         [0055]    Furthermore, the motor  50  may be connected with a control module. The control module may control power output of the motor  50  to the controlling apparatus  20  and the lifting apparatus  30 . For example, the motor  50  may be controlled by the control module to activate the at controlling apparatus  20  and the lifting apparatus  30  respectively through the power transmission unit. The motor  50  may also be controlled by the control module to activate the at controlling apparatus  20  and the lifting apparatus  30  through the power transmission unit with only the controlling apparatus  20  or the lifting apparatus being connected with the motor  50 . 
         [0056]    In order to solve size distortion problems of the coil spring comes from a residual stress when bending the spring wire  80 , the control module may connect with a testing module with testing and correcting steps of: 
         [0057]    Step 1. comparing the size of the coil spring with a standard coil spring to obtain a difference value. The difference value may be cause by bouncing back of the spring wire  80  while bending it or location error of the coil spring bend tools  10 . 
         [0058]    The size of the coil spring may be measured by an image measurement method or an optical measurement method. The image measurement method may be achieved by filming the coil spring and calculating the difference value with the standard coil spring. The optical measurement method may be achieved by projecting a light beam to the coil spring and calculating reflect time and angle of the light beam so as to obtain the size of the coil spring. 
         [0059]    Step 2. outputting a correction signal to the control module by the testing module according to the difference or the size measured by step 1. The control module controls the displacement of the at least two coil spring bending tools  10  and the height displacement of the assembly platform  40  according to the correction signal in order to eliminate the difference value. 
         [0060]    Step 3. Re-measuring the difference value of reproduced coil spring and repeating steps 1 and 2 until the difference value being eliminated to a tolerance value. 
         [0061]    For example, the diameter of the coil spring was being preset on 5 cm. Diameter of finished product of the coil spring was 5.2 cm due to material property of the spring wire  80 . The difference value 0.2 cm then was being measure by step 1. The control module then will adjust the distance between P 1 , P 2  and the virtual reference B into 2.4 cm and R becomes to 4.8 cm according the difference value 0.2 cm. The difference value 0.2 cm that comes from material property of the spring wire  80  will be eliminated by reducing radius of the coil spring R. After re-measuring the radius of the reproduced coil spring after step 1 and step 2, the coordinate of P 1  and P 2  will be continued if the difference value is eliminated to the tolerance value. If the difference value is still over the tolerance value, step 1 and step 2 will be repeated after the difference value being eliminated to the tolerance value. 
         [0062]    A length of the spring wire  80  being dragged out from the wire feeding assembly  70  will be decided by a circumference of the coil spring according to the change of the displacement of the coil spring bending tools  10  and the radius of the coil spring. 
         [0063]    Above-mentioned testing and correction method always controls the length of the spring wire  80  being dragged out from the wire feeding assembly  70  according to preset diameter of the coil spring but the difference value. As above-mentioned embodiment, the length of the coil spring being dragged out from the wire feeding assembly  70  will be decided by the preset diameter 5 cm of the coil spring but the difference value 4.8 cm. 
         [0064]    According to the above-mentioned features, the present invention has advantages as followings. 
         [0065]    3. The conventional coil spring forming machine was operated by an absolute origin point and an absolute coordinate which leads to complex calculation process. The present invention is able to solve the problem of the conventional coil spring forming machine by using the virtual reference point and relative coordinate for more simple calculation process. The present invention is operated by controlling the displacement of the coil spring bending tools  10  being adjusted according to the radius of the coil spring which leads to more simple and one-dimensional calculation. 
         [0066]    4. Since the controlling method of the coil spring bending tools  10  is simplified, the present invention may be cost down by operating multiple controlling apparatus  20  with one motor  50  through power transmission unit like belt set, gear set or chain set.