Abstract:
The apparatus has an indexable carriage adapted to move the coil springs and the border wire along a path. A wire cutter disposed adjacent the path has an inner member with an axial hole adapted to receive the wire and a tubular outer member receiving the inner member and movable relative to the inner member. The outer member has a cutting edge. An actuator is operatively connected to one of the inner and outer members to provide a relative rotation between the inner and outer members. That relative rotation results in the wire being sheared by the cutting edge to provide a length of wire. A wire wrapping mechanism disposed adjacent the path receives the length of wire and wraps the length of wire around an end turn of a coil spring and a border wire.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates generally to the assembly of coil springs of the type used in bedding and upholstery and, more particularly, to an improved apparatus for attaching end turns of a coil spring to a border wire.  
         BACKGROUND OF THE INVENTION  
         [0002]    In known assemblies of coil springs that are used in bedding and upholstery, adjacent rows of coil springs are connected by a helical lacing wire that is laced around adjacent portions of top and bottom turns of the coil springs. The lacing wire often extends from one side edge of the coil spring assembly to an opposite side edge to form a matrix of interconnected coil springs. In some applications, only the top turns or only the bottom turns are laced together. Thereafter, the coil spring matrix is converted into a completed coil spring assembly by attaching the coil springs to a border wire in either or both of the top and bottom planes of the spring unit. The border wire is generally a single heavy gauge wire preformed into a rectangular configuration and disposed in border fashion about the periphery of the coil spring matrix. The border wire is attached to the peripheral portion of the end turns of the spring coils by helical lacing wires, preformed metal clips, staples or separate lengths of straight wire. The attachment of the border wire to the matrix of coil springs is performed either manually or automatically.  
           [0003]    At the present time, nearly all commercial fasteners used for attaching the border wire to the coil springs are sheet metal clips that are preformed and assembled into a string of clips. The string of clips is fed into a machine that applies the clips to a border wire and inner spring assembly being conveyed past the machine. The sheet metal clips have sharp edges and corners that often cause problems during the manufacturing process. For example, the corners of the clips can catch on fabric that is subsequently applied to the coil spring assembly. Any time fabric catches on a clip, some sort of special handling is required that adds cost to the manufacturing process. Further, any time the coil spring assembly is manually handled, care must be taken to avoid contact with the sharp edges and corners of the sheet metal clips.  
           [0004]    Therefore, there is a need for an apparatus that connects coils springs to a border wire with fasteners that do not have sharp or pointed edges, corners or ends.  
         SUMMARY OF THE INVENTION  
         [0005]    The present invention provides a wire cutting and wrapping apparatus that provides cut wire tips that are blunt. The wire cutting and wrapping apparatus of the present invention is especially useful for attaching coil springs to border wires in the manufacture of coil spring assemblies to be used for bedding and upholstery. By providing cut wire fasteners with blunt ends, a resulting coil spring assembly can be readily covered with a fabric without the fabric being unnecessarily caught or torn by the ends of the wire fasteners. In addition, the blunt tips of the wire fasteners provided by the wire cutting and wrapping apparatus of the present invention make the finished coil spring assembly much easier to manually handle.  
           [0006]    According to the principles of the present invention and in accordance with the described embodiments, the invention provides an apparatus for attaching end turns of coil springs to a border wire. The apparatus has an indexable carriage adapted to move the coil springs and the border wire along a path. A wire cutter located adjacent the path has an inner member with an axial hole adapted to receive the wire and a tubular outer member receiving the inner member and movable relative to the inner member. The outer member has a cutting edge. An actuator is operatively connected to one of the inner member and the outer member to provide a relative rotation between the inner member and the outer member. That relative rotation results in the wire being sheared by the cutting edge to provide a length of wire. A wire wrapping mechanism located adjacent the wire cutter and the path receives the length of wire and wraps the length of wire around an end turn of a coil spring and a border wire.  
           [0007]    In one aspect of the invention, the wire wrapping mechanism has a pair of gears rotatable with respect to a common axis of rotation. Each of the gears has a radial slot that receives an end turn of a coil spring and a border wire and a hole that receives the length of wire. A drive shaft is mechanically coupled to the pair of gears, and the drive shaft is operable to rotate each of the gears in a different direction to wrap the length of wire around the end turn of the coil and the border wire. In another aspect of the invention, the hole has a centerline nonparallel with respect to the common axis of rotation.  
           [0008]    In another embodiment of the invention, a method is provided for attaching an end turn of a coil to a border wire. First, the end turn of a coil spring and a border wire are located in radial slots of respective gears, wherein the respective gears having a common axis of rotation. Next, a wire is fed through an axial hole of an inner member of a wire cutter. The wire cutter has a tubular outer member that receives the inner member, and the outer member has a cutting edge adjacent an end surface of the inner member. Next, the wire is fed through holes in the respective gears, and an actuator of the wire cutter is operated to provide a relative rotation between the inner member and the outer member. That relative rotation causes the cutting edge to pass over the axial hole of the inner member and shear the wire to a length. A drive shaft mechanically coupled to the two gears is then rotated to simultaneously rotate each of the two gears in a different direction and the length of the wire is wrapped around the end turn of the coil spring and the border wire located in the radial slots of the respective gears.  
           [0009]    These and other objects and advantages of the present invention will become more readily apparent during the following detailed description taken in conjunction with the drawings herein. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a perspective view of an inner spring and border wire fastening machine utilizing wire fastening heads in accordance with the principles of the present invention.  
         [0011]    [0011]FIG. 2 is a partial perspective view of carriage drive mechanism used with the inner spring and border wire fastening machine of FIG. 1.  
         [0012]    [0012]FIG. 3 is a partial perspective view of a wire wrap station on the inner spring and border wire fastening machine of FIG. 1.  
         [0013]    [0013]FIG. 4 is a perspective view of one side of the wire fastening head used on the inner spring and border wire fastening machine of FIG. 1.  
         [0014]    [0014]FIG. 5 is a perspective view of an opposite side of the wire fastening head used on the inner spring and border wire fastening machine of FIG. 1.  
         [0015]    [0015]FIG. 6 is a centerline cross-sectional view of a wire cutter used on the wire fastening head of FIGS. 4 and 5.  
         [0016]    [0016]FIGS. 7A and 7B are cross-sectional views taken along the line  7 A- 7 A of FIG. 6 and illustrate the wire cutting operation of the wire cutter.  
         [0017]    [0017]FIG. 8 is a disassembled perspective view of the gear drive for a wire wrapper used on the wire fastening head of FIGS. 4 and 5.  
         [0018]    [0018]FIG. 9 is a cross-sectional view taken along line  9 - 9  of FIG. 6 and is an end view of the gear drive for the wire wrapper used on the wire fastening head of FIGS.  4 - 6 .  
         [0019]    [0019]FIG. 10 is a schematic block diagram of a control system for the inner spring and border wire fastening machine of FIG. 1.  
         [0020]    [0020]FIG. 11 is a cross-sectional view similar to FIG. 6 of the wire fastening head and illustrates a cut length of wire prior to a wire wrapping operation.  
         [0021]    FIGS.  12 A- 12 C are cross-sectional views similar to FIG. 9 of the wire fastening head that illustrate the wire wrapping process.  
         [0022]    [0022]FIG. 13 is another cross-sectional view similar to FIG. 11 of the wire fastening head illustrating the cut length of wire after the wire wrapping operation. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]    Referring to FIGS.  1 - 3 , a coil/border wire fastening machine  20  includes a wire wrapping station  22  and an inner spring feed and support structure  24 . The support structure  24  includes a base  26  that carries a support table  28  and movable carriage  30 . The support table  28  is tilted rearwardly at an angle of about 15° from vertical and is provided with a smooth-surfaced skin or facing  32 , for example, a thin, lightweight aluminum sheeting or other material. The slight inclination of the table  28  from vertical maintains the center of gravity of a mattress spring assembly  34  and its associated front and rear border wires  36 ,  38 , respectively, in a position such that they remain in contact with the facing  32  throughout the wire wrapping operation. The base  26  and support table  28  are fabricated of hollow bar stock utilizing a minimum number of structural elements consistent with providing a self-supporting, high strength, stable, relatively lightweight unit. The base  26  further includes casters  40  that permit the machine to be moved to different locations. The front of the base  26  is provided with support tube  44  on which the spring assembly  34  rests. The border wires  36 ,  38  do not rest on the support tube  44 . The spring assembly and border wires  36 ,  38  are advanced together in the direction of the wire wrapping station  22 . After the spring assembly  34  and border wires  36 ,  38  have moved through the wire wrapping station  22  and advanced onto a paddle-like member  46 , the member  46  is rotated through an angle of about 90° to position another edge of the spring assembly  34  on the support tube  44 .  
         [0024]    The spring assembly  34  and border wires  36 ,  38  are moved toward and away from the wire wrapping station  22  by the movable carriage  30 . Referring to FIG. 2, the carriage  30  is provided with a plurality of rollers  48  that ride along the upper and lower margins and against an inner wall  50  of guide plate  52 . The carriage  30  has pins  54  that engage an endless chain  56  driven by a sprocket (not shown) in a known manner. The sprocket is connected to a drive shaft  55  on which a pulley  58  is also mounted. The pulley  58  is driven by a belt  60  connected to a pulley  62  mounted on an output shaft  57  of a servomotor  64 . A pulse encoder  66  is mounted on the drive shaft  55  and provides a feedback signal representing travel of the carriage  30  toward and away from the wire wrapping station  22 . The inner spring feed and support structure  24  is substantially similar to a support described and illustrated in U.S. Pat. No. 4,829,643 entitled “Apparatus and Method for Automatically Securing Border Wires on Mattress Innersprings”, which patent is hereby incorporated in its entirety by reference herein.  
         [0025]    Referring to FIG. 3, the wire wrapping station  22  includes front and rear wire fastening heads  72 , 73 , respectively. Each of the wire wrap heads  72 ,  73  has a respective positioning actuator  74 ,  75 , for example, a cylinder, mounted on a respective fixed bearing block  76 ,  77 . Each of the bearing blocks  76 ,  77  is mounted to a lower side of a plate  78  via brackets  79 . Front and rear wire wrap servomotors  80 ,  81  are mounted to the ends of respective cylinders  74 ,  75 . Operation of the cylinders  74 ,  75  moves the cylinder  74 ,  75  and the associated front and rear wire wrap heads  72 ,  73  in a generally vertical direction  82  relative to the respective fixed bearing blocks  76 ,  77  and into alignment with the respective front and rear border wires  36 ,  38 . Wire wrapping operations are then executed during which wires  84 ,  85  are fed to the respective front and rear wire wrap heads  72 ,  73  from respective wire feeders  86 ,  87  (FIG. 1). The wire wrap heads  72 ,  73  cut the respective wires  84 ,  85  to a predetermined length and wrap the cut lengths around respective border wires  36 ,  38  and adjacent end turns  88 ,  89  of a border coil  90  in the spring assembly  34 .  
         [0026]    The construction and operation of the front and rear wire fastening heads  72 ,  73  are identical, and therefore, only the construction and operation of the rear wire fastening head  73  will be described in detail. Referring to FIGS. 4 and 5, the wire fastening head  73  is comprised of a wire cutter  92  and a wire wrapper  94 . The wire cutter  92  has a bracket  96  that is bolted to a gear box or body  98  of the wire cutter  94 . The bracket  96  has a clamp  100  that holds a wire guide  102 . The wire guide  102  is made from a hardened steel and has a longitudinal bore or hole  104  for receiving and guiding the wire  84 . As shown in FIGS. 6 and 7A, the hole  104  is offset from, and does not intersect, the longitudinal centerline  106  of the guide tube  102 . A steel sleeve  108  is rotatably mounted on the guide tube  102 . The sleeve  108  has a lever arm  110  extending radially therefrom. The lever arm includes a slot  112  that receives a drive pin  114  extending across a clevis  116  mounted on a distal end of a rod  118  (FIG. 5). The rod  118  is reciprocated by operation of a cylinder  126 , thereby moving the lever  110  and sleeve  108  through an arc of about 90°. With the rod  118  fully retracted into the cylinder  126 , the wire  84  extends through the guide tube  102  (FIGS.  6 - 7 A) and past a cutting or shearing edge  122  mounted on the end of the rotatable sleeve  108 . The shearing edge  122  is located immediately adjacent a lower end surface  124  of the guide tube  102 . Operating the cylinder  126  moves the rod  118  outward, thereby moving the sleeve  108  in a generally counterclockwise direction as viewed in FIG. 7A. Sleeve  108  is moved approximately 90° and the cutting edge  122  moves across the feed hole  104 , thereby shearing the wire  84  to its desired length.  
         [0027]    Referring to FIG. 4, the wire wrapper  94  is operated by a drive shaft  128  that is connected via a sprocket  129  and chain  130  to the rear wire wrap servomotor  81  (FIG. 3). The drive shaft  128  is rotatably mounted in the gear box  98 . Referring to FIG. 8, the wire wrapping action is provided by two counter rotating wire wrap gears  132 ,  134 . Rotation of the drive shaft  128  in a counterclockwise direction, as viewed in FIGS. 8 and 9, also rotates a first drive gear  136  counterclockwise. That rotation causes a clockwise rotation of the larger gear  138  that, in turn, simultaneously rotates gears  140 ,  142  counterclockwise. The gears  140 ,  142  mesh with the first wire wrapping gear  132  and turn it clockwise. Simultaneously, the counterclockwise rotation of the drive shaft  128  rotates drive gears  144 ,  146  in the counterclockwise and clockwise directions, respectively. The clockwise rotating gear  146  meshes with gear  148  and turns it counterclockwise. The counterclockwise rotation of the gear  148  causes a clockwise rotation of the gears  150 ,  152  that, in turn, rotate the second wire wrapping gear  134  in a counterclockwise direction. Thus, rotation of the drive shaft  128  creates opposite rotations of the first and second wire wrap gears  132 ,  134 .  
         [0028]    In use, referring to FIG. 1, a spring assembly  34  with forward and rear border wires  36 ,  38 , respectively, is placed on the support tube  44  of the base  26  and is also supported by the surface  32  of the table  28 . A control  154  (FIG. 9) is operated to initiate a wire fastening cycle. The control  154  may be any suitable controller, for example, a programmable logic control. The control  154  first provides output signals to command the carriage servomotor  64  to index the carriage  30  along a linear path in a direction indicated by the arrow  68 . The indexing carriage  30  pulls the spring assembly  34  and border wires  36 ,  38  over the support tube  44  until end turns  88 ,  89  (FIG. 3) of a border coil  90  are adjacent the wire wrap station  22 . The desired location of each coil is detected by a coil sensor  153  (FIG. 3) that provides a feedback signal to the control  154 , and the control  154  commands the carriage servomotor  64  to stop in response to the feedback signal from the coil sensor  153 . The coil sensor  153  can be any proximity sensor that is effective to detect coil presence such that an axial centerline of the coil is substantially in line with the axis of rotation of the wire wrap gears  132 ,  134  (FIG. 8). When properly located, the front and rear end turns  88 ,  89  are positioned immediately adjacent and above the front and rear wire fastening heads  72 ,  73 , respectively. When the carriage  30  has been moved to the desired position, the control  154  stops the operation of the carriage servomotor  64  and initiates operation of the front and rear head position actuators  74 ,  75 .  
         [0029]    The head position actuators  74 ,  75  can be any actuators that are effective to selectively raise and lower the respective wire fastening heads  72 ,  73 . When the control  154  commands the head position actuators  74 ,  75  to raise, the wire fastening heads  72 ,  73  are elevated and the end turns  88 ,  89  and respective border wires  36 ,  38  are received in radial slots  155  (FIG. 8) located in each of the wire wrap gears. When the wire fastening heads  72 ,  73  are fully elevated, the border wires  36 ,  38  are located in the slots  155  approximately coincident with a centerline axis of rotation of the wire wrap gears  132 ,  134  as shown in FIG. 9. Simultaneously, as shown in FIGS. 5 and 6, the border wire  36  is located in border wire support brackets  159  that are located on opposite sides of the gear box  98  of the wire wrapper  90 .  
         [0030]    As will be appreciated, the operation of wire fastening heads  72 ,  73  is substantially identical, and therefore, the operation of only wire fastening head  73  will be described in detail. The control  154  initiates operation of a wire feed servomotor  156  (FIG. 10) associated with the wire feeder  86  (FIG. 3). The wire feeder  86  feeds the wire  84  through the longitudinal bore  104  (FIG. 6) of the wire guide tube  102  of the wire cutter  92 . The wire  84  is further fed through a guide block  160  that is attached to a side face of the wire wrap gear  134 . The wire is further fed through a hole  162  in the wire wrap gear  132 . The control  154  terminates the operation of wire feed servomotor  156  when the proper length of wire  84  has been fed into the wire fastening head  73 . The proper length of wire is a length such that the point  164  where the wire  84  passes between the wire wrap gears  132 ,  134  is a midpoint between a distal end  166  and an end surface  124  of the wire guide  102 .  
         [0031]    Thereafter, the control  154  provides output signals to command operation of the wire cut actuators  120 ,  126  (FIG. 10). Again, the operation of the wire cut actuators  120 ,  126  is identical, and only the operation of the wire cut actuator  126  will be described in detail. Referring to FIG. 4, operating the actuator  126  moves the rod  118  outward, thereby rotating the sleeve  108  and the cutting edge  122  (FIG. 7A). After the sleeve  108  moves through an angle of about 90° as shown in FIG. 7B, the wire  84  is sheared such that it has a relatively smooth cut end. The control  154  then reverses the operation of the actuator  126 , thereby retracting the rod  118  and returning the sleeve  108  and cutting edge  122  to their original positions as illustrated in FIG. 7A. Referring to FIG. 11, a cut length of wire  168  is now located within the wire wrap gears  132 ,  134  adjacent end turn  89  and border wire  38 . At this point, the control  154  commands the wire wrap servo motors  80 ,  81  (FIG. 3) of the respective wire fastening heads  72 ,  73  to rotate the servo motors through four full revolutions. Rotation of the drive shaft  128  (FIG. 4) causes the wire wrap gears  132 ,  134  to rotate in opposite directions. Thus, referring to FIG. 11, the wire wrap gear  132  wraps one end  166  of the cut length of wire  168  in a first longitudinal direction along the border wire  38 , for example, to the right as viewed in FIG. 11. Simultaneously, the wire wrap gear  134  wraps the opposite end  170  of the cut wire  168  in the opposite longitudinal direction along the border wire  38 , for example, to the left as viewed in FIG. 11. The wire wrapping process resulting from one revolution of the counter-rotating wire wrapping gears  132 ,  134  is shown in FIGS.  12 A- 12 C and  13 . Rotating the drive shaft  128  through two revolutions results in one revolution of the counter-rotating wire wrap gears  132 ,  134 . Thereafter, the control  154  commands the wire wrap servo motors  80 ,  81  to rotate the drive shaft  128  through an additional two revolutions, thereby further working and smoothing the wire length  168  around the end turn  89  and border wire  38 .  
         [0032]    Thereafter, the control  154  reverses the operation of the head position actuators  74 ,  75  to lower the wire fastening heads  72 ,  73  to their original positions away from the border wires  36 ,  38 . The carriage motor  64  is again operated by the control  154  to increment the carriage  30  through a displacement equal to the coil pitch, that is, the distance between the centerlines of the border coils  90  in the spring assembly  34 . Thus, the end turns of an adjacent border coil are located above the wire fastener heads  72 ,  73  at the wire wrap station  22 . The operation previously described is then repeated. After the end turns of each of the border coils along one edge of the inner spring have been fastened to the border wires  36 ,  38 , the paddle-like member  46  is rotated in a known manner, thereby rotating the spring assembly  34  and border wires  36 ,  38  about 90°. The wire wrapping operation continues until all of the end turns of the border coils around the perimeter of the spring assembly  34  have been fastened by wire wrapping to the border wires  36 ,  38 .  
         [0033]    The wire fastening heads  72 ,  73  provide cut wire tips that are blunt. Thus, the cut wire with blunt ends permits a resulting coil spring assembly to be readily covered with a fabric without the fabric being unnecessarily caught or torn by the ends of the wire fasteners. In addition, the blunt tips of the wire fasteners provided by the wire wrapping mechanisms make the finished coil spring assembly much easier to manually handle. This is a substantial improvement over known wire attachments that produce a cut wire tip that often has some pointed shape. A pointed shape may be the result of the wire cutting edge not moving perpendicular to the wire centerline; the wire not being firmly supported during the cutting operation; or the structure of the wire cutter results in a working of the wire tip that produces a pointed shape.  
         [0034]    While the invention has been illustrated by the description of one embodiment and while the embodiment has been described in considerable detail, there is no intention to restrict nor in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those who are skilled in the art. For example, in the described embodiment.  
         [0035]    Therefore, the invention in its broadest aspects is not limited to the specific details shown and described. Consequently, departures may be made from the details described herein without departing from the spirit and scope of the claims which follow.