Patent Publication Number: US-2021187588-A1

Title: Apparatus and method for forming springs

Description:
The present invention relates to an apparatus for forming springs, and to a method of forming springs, it is concerned particularly, although not exclusively, with an apparatus and a method for forming coil springs of wire. 
     The manufacture of helically coiled wire springs currently involves a number of steps. Firstly, the wire is taken using feed rollers from a supply, which is typically a reel, and if necessary the wire is straightened to remove any kinks or twists. The wire is then formed into a helical coil using a first deflecting tool to instigate a bend in a first direction and then a second deflecting tool, arranged substantially perpendicular to the first, to instigate a bend in a second direction. This urges the wire out pf plane, and into a helix. A pitching tool controls the separation of adjacent turns of the coil, according to requirements, and when the coil is of a predetermined length a cutter severs the spring from the rest of the wire. 
       FIG. 1  shows schematically an example of a previously considered spring forming apparatus, generally at  100 . A reel  110  dispenses metal wire  120 , typically under the control of servo-driven pairs of feed rollers  130 . The wire passes through guide rollers  140  to a forming station  150 . The forming station comprises a first deflector  160 , which causes the straight wire to deflect in a first direction, having a vector component approximately 90 degrees to the original axis of the wire. The wire then meets a second deflector  170  which causes it to be deflected in a second direction, which has a vector component approximately 90 degrees to both the first direction and to the original axis of the wire. The result is a helically coiled spring S. 
     There are several other, previously considered ways of forming springs from wire. Almost all of them involve bending the wire, usually by pushing it against some kind of deflecting tool. 
     A pitching tool (omitted from the drawing for reasons of clarity) determines the spacing between adjacent coils of the spring. When the spring reaches a pre-determined length a cutter  150  severs the spring from the rest of the wire. 
     For clean, accurate cutting, the feeding of the wire must be temporarily halted, or at least considerably slowed, whilst the cutter is introduced. Immediately after the cut is made the feed must resume. In the example shown, the cutter  100  comprises a tool  190  that is mounted for elliptical/rotational engagement with the wire, so that the motion of the wire need not be halted completely for a clean cut. 
     Most wire is supplied from a reel which, when full, can have a mass of several hundred kilograms. The reel and the feed rollers must therefore be servo-controlled so as to maintain the correct tension in the feed. The motors that drive the feed rollers must be sufficiently powerful to manipulate the wire supply in the face of considerable inertia as the wire experiences cycles of acceleration. As higher production speeds are demanded—some current manufacturers of upholstered units require springs to be produced at a rate of 300 per minute—the problem becomes exacerbated and requires ever more sophisticated, and hence expensive, drive apparatus. 
     Another example of the prior art is disclosed in WO 2015/007496. In this document, a weakening is introduced into a length of spring wire at two diametrically opposed portions of the wire surface prior to a cutting device severing the formed spring from the rest of the wire. However, this approach does not address the problem of momentarily halting the feed in order to deploy the cutting tool, with all the attendant disadvantages outlined above. 
     Embodiments of the present invention aim to address at least partly the aforementioned problem(s). 
     The present invention is defined In the attached independent claims, to which reference should now be made. Further, preferred features may be found in the sub-claims appended thereto. 
     According to one aspect of the present invention, there is provided a method of manufacturing a spring from a spring medium, the method comprising effecting an irregularity in a portion of the spring medium and thereafter deflecting the spring medium to cause it to form a spring, whereby the deflecting is arranged to cause discontinuity in the spring medium at the location of the irregularity. 
     Preferably the method comprises feeding the spring tedium from a supply to a spring forming apparatus. 
     The method may comprise effecting an irregularity in the spring medium which comprises making at least one partial cut, indent, nick, depression, deformity or weakness in the spring medium. 
     The method preferably comprises effecting the irregularity in the spring medium using one or more rollers. 
     In a preferred arrangement the irregularity is formed without halting the motion of the spring medium, more preferably without slowing the motion of the spring medium. 
     According to another aspect of the present invention there is provided apparatus for manufacturing a spring from a spring medium, the apparatus comprising a feed device for feeding the spring medium and a spring forming device for forming a spring by deflecting the spring medium, wherein deflection by the spring forming device is arranged in use to create a discontinuity in the spring medium at the location of a previously formed irregularity. 
     Preferably the apparatus further comprises an irregularity forming device for forming an irregularity in the spring medium. 
     In a preferred arrangement the irregularity forming device is arranged to form an irregularity in the spring medium comprising at least one partial cut, indent, nick, depression, deformity or weakness in the spring medium. 
     The irregularity forming device may comprise one or more rollers. 
     The spring medium preferably comprises a supply of substantially unbent material to be formed into springs by deflecting the material so as to cause it to bend. 
     The spring medium may comprise wire, and more preferably comprises metal wire. 
     In a preferred arrangement, as a result of the irregularity, the spring medium is arranged to break by the deflecting action of the spring forming device, thereby to separate a formed spring from the rest of the spring medium. 
     The invention also comprises a program for causing a device to perform a method of manufacturing a spring in according to any statement herein. 
     According to another aspect of the present invention, there is provided an apparatus comprising a processor and a memory having therein computer readable instructions, the processor being arranged in used to read the instructions to cause the performance of a method according to any statement herein. 
     In a further aspect, the invention provides a computer program product on a non-transitory computer readable storage medium, comprising computer readable instructions that, when executed by a computer, cause the computer to perform a method of manufacturing a spring according to any statement herein. 
     The invention also includes a spring formed by a method, or an apparatus, according to any statement herein. 
     The invention may include any combination of the features or limitations referred to herein, except such a combination of features as are mutually exclusive, or mutually inconsistent. 
    
    
     
       A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which 
         FIG. 1  shows schematically a previously considered apparatus for forming springs; 
         FIG. 2  shows schematically an apparatus for forming springs in accordance with an embodiment of the present invention; 
         FIG. 3  shows a portion of spring medium containing an irregularity; and 
         FIG. 4  shows a pair of rollers for forming the irregularity of  FIG. 3 . 
     
    
    
     Turning to  FIG. 2 , this shows schematically a spring forming apparatus, generally at  200 , according to an embodiment of the present invention. Metal wire  220  is fed from a supply (not shown) by feed rollers  230 , via irregularity-effecting rollers  240  to a forming station  250 . The forming station comprises a first deflector  260  and a second deflector  270 , which work in substantially the same way as the deflectors of the previously considered spring forming station described above in relation to  FIG. 1 . However, there is no cutter in this embodiment. When the spring S is complete, it separates automatically from the rest of the wire  220  due to the presence Of an irregularity  280 , as will be described below. 
     The irregularity-effecting pair of rollers  240  Comprises an upper roller  242  and a lower roller  244 . Each roller has a channel  246  in which the wire  220  is conducted. Most of the time the rollers  240  are stationary and the wire  220  slides through the channels  246 . When an irregularity is to be introduced, the rollers rotate and an anvil  248 , located in the channel of the upper roller, comes to press against the wire, resulting in an irregularity  280  being introduced in the wire. 
     The timing and the motion of the rollers  240  is computer controlled, so that the position of the irregularity can be accurately specified. 
       FIG. 3  is a more detailed view of the wire  220  including the irregularity  280  formed by the rollers  240 . 
       FIG. 4  shows the rollers  292  and  244 . On the left is the lower roller of  FIG. 2 , showing the wire  220  in channel  246 . To the right is the upper roller of  FIG. 2 , showing the irregularity-forming anvil  248 . When an irregularity is to be formed the rollers  242  and  244  rotate and the anvil  248  presses the wire against the channel  246  of the lower roller. This causes a feature  280 , such as is shown in  FIG. 3 , in a precisely determined place. 
     As the wire progresses towards the spring forming station  250  the feature  280  will eventually encounter the first deflector  260 . When this happens the wire will break cleanly, so that the spring S, formed in advance of the feature  280 , will separate from the rest of the wire  220 . This is because the presence of the irregularity  280  concentrates the stresses in the wire when it experiences bending forces. 
     No cutter is needed, and therefore no slowing, much less a halt, of the feed is necessary. This allows for springs to be manufactured at a greater rate. 
     As a consequence, the heavy and expensive feed rollers. currently used in the apparatus shown in  FIG. 1  are no longer needed. 
     Other arrangements for forming the irregularity can be used. For example, in another embodiment (net shown) the wire car be pressed between two opposed irregularity-forming anvils, or between one anvil on one roller and a pair complimentary supports on the other roller, for example. Furthermore, whilst the example of the irregularity  280  above is a V-shape, it will be understood that the shape and/or depth of the irregularity can be different. 
     An adjustment can be made for different diameters of wire by altering the pressure applied by the rollers  240  and/or the distance of the anvil feature or features  24 S from the wire. 
     The timing of the irregularity forming operation can be controlled precisely by controlling the operation of the rollers  240 , or just the single roller  242  in the example illustrated. 
     The irregularity need not be formed using one or more rollers. Other mechanical means may be employed to effect the weakness in the wire. Indeed, the means for making the irregularity need not be mechanical. An energy source, such as an electrical arc or a laser, could also be used to introduce the weakness in the wire al a predetermined location, for example. 
     Furthermore, whilst the example described above has the irregularity formed after (i.e. downstream of) the feed rollers, in another embodiment (not shown) it may be formed before (i.e. upstream of) the feed rollers. 
     In certain circumstances, the irregularities could be pre-formed on the wire, for example on another device, prior to introduction of the wire to the spring forming apparatus. 
     When combined with an alternative supply, that comprises for example a wire looped around the inside of a drum, from which the wire emerges substantially straight and under no tension, the present invention is particularly effective in increasing the speed of spring manufacture. 
     Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance, it should be understood that the applicant claims protection in respect of any patentable feature or combination of features referred to herein, and/or shown in the drawings, whether or not particular emphasis has been placed thereon.