Abstract:
A method and apparatus is disclosed for simultaneously creating a pair of stacks of nested sinuous spring strips. This apparatus includes first and second generally circular forming drums onto which a feeder mechanism is operable to sequentially and alternately pass each of the spring strips from over a forming mandrel onto the top surface of the first and second generally circular forming drums. A first stripper mechanism is then operable to strip a first one of the strips onto a first stacking drum and for stripping a second following one of the strips onto a second stacking drum. A second stripper mechanism is then operable to strip those stacks from the stacking drums onto a pair of discharge chutes.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to arcuate sinuous wire springs and, more particularly, to a method and apparatus for arranging a plurality of arcuate sinuous wire springs in a generally circular nested stack. 
     BACKGROUND OF THE INVENTION 
     Many furniture products, including such products as chairs, sofas and automobile seats utilize sinuous wire spring elements as to create resilient surfaces, such as seats and backrests, in an item of furniture. Such resilient spring elements are disclosed, for example, in U.S. Pat. No. 2,800,928. Generally, these spring elements are of an arcuate or curvilinear shape which creates a problem in storing and using those elements, particularly if those elements are manufactured in one facility and utilized in another manufacturing facility. It has therefore become common practice to create a nested bundle of those elements for storage or shipment from one location to another. 
     U.S. Pat. No. 4,270,582 discloses a machine for creating a nested bundle of such arcuate configurated sinuous springs. According to the disclosure of this patent, precut straight spring elements are fed into the machine which imparts an arcuate curvilinear shape to the spring elements. The curvilinear or arcuate spring elements are engaged by the teeth of a gear or protrusions on the surface of a feed wheel to feed or load those curvilinear or arcuate-shaped sinuous spring elements into a first or primary cage or drum which effectively compresses the arcuate spring element into a generally circular configuration within the interior of the primary cage or drum. After the completion of the loading of the arcuate spring into the interior of the primary cage or drum, a stripper is actuated to impart an axial force upon the compressed circular-shaped arcuate spring, causing it to pass into a secondary cage or drum of larger diameter where the arcuate spring expands into contact with the interior surface of the secondary cage or into contact with the interior surface of a previously loaded arcuate spring contained within the secondary cage. After a predetermined number of springs have been loaded into the secondary cage or drum, the secondary drum is rotated to an unloading position whereat a stack of nested arcuate spring elements are removed from the secondary cage. 
     U.S. Pat. No. 5,150,600 also discloses a machine for automatically creating nested stacks of arcuately configured sinuous springs similar to the disclosure of U.S. Pat. No. 4,270,582. This patent also inserts the arcuately configured springs into the interior of a primary or first cage or drum so as to create a generally circular configured arcuate spring and then passes that generally circular arcuate spring from the interior of the first primary drum into the interior of a larger diameter circular cage or drum whereat the generally circular configured arcuate spring expands into contact with the interior surface of the secondary cage or drum or into contact with a previously inserted circular configured arcuate spring. According to the disclosure of this patent, a stripper is actuated after a predetermined number of sinuous springs have been nested within the interior of the secondary cage or drum so as to deposit the stack of nested springs onto a discharge chute. 
     Machines made in accordance with the disclosure of the above-identified patents are subject to the criticism that they are generally very noisy because of the clash of the input feed wheels with the transverse parallel bars of the sinuous springs. They are also subject to the criticism that they are very limited in the configuration of the springs which they are able to handle without a substantial reset-up and reconfiguration of the machines, often times requiring many hours or even days of reset-up operator time. The nature of sinuous springs, though, as used in the furniture industry, is that there are hundreds or even thousands of different furniture products which utilize such springs of varying and differing length, resilient characteristics, temper of the spring wire, differing gauge wire and spacing of the parallel bars of the spring. All of these differing characteristics of the sinuous springs dictate that a machine for nesting such springs should be capable of handling and stacking sinuous springs of varying dimensions and characteristics. It has therefore been an objective of this invention to overcome these limitations relative to the versatility of the machine to handle arcuate springs of different lengths and configurations with minimal requirements for reset-up operator time. 
     Another objective of the invention of this invention has been to increase the speeds of the machine and maintaining continuity of springs in a stack of nested springs created by the machine. The nature of sinuous springs is that if the sinuous springs being stacked by the machine have an uneven number of bars in the individual spring element, every other spring in the stack will have an end section which is curved in a direction opposite to the end of the spring which preceded it. It has therefore been an objective of this invention to create stacks of nested coil springs of either even or uneven number of parallel bars in which all of the end turns of the stack of springs in a nest are oriented in the same direction. At the present time, there are no machines, including the machines described in the above-identified patents, capable of nesting and stacking sinuous wire springs having uneven numbers of parallel bars with the end turns of the springs oriented in the same or a common direction as required by furniture manufacturers. Such uneven number of bar sinuous springs, which are commonly used in the furniture industry, are now manually removed from the machine which imparts an arcuate configuration to the spring and manually stacked in a nested arrangement. 
     SUMMARY OF THE INVENTION 
     The apparatus or machine of this invention which accomplishes these objectives and one aspect of the invention of this application comprises a feeder mechanism for sequentially feeding sinuous spring strips of a discrete length over a forming mandrel to impart an arcuate configuration to each strip and then feed the arcuate strip onto the surface of a generally circular forming drum. A stripper mechanism then is operable to strip a first one of the arcuate configured strips from over the forming drum and onto the top surface of a smaller diameter stacking drum and then sequentially strip a following plurality of arcuate configured strips from the forming drum onto the stacking drum and over the top of the strip which preceded it onto the stacking drum to create a nested plurality of arcuate configured springs located on the stacking drum. By creating the nest of arcuately configured springs one atop the other, rather than by forcing one to the inside of the strip which preceded it into the nest, as in the prior art machines, the machine of this invention is capable of handling a much greater variety of springs with less criticality of dimensional similarity from one spring to the next. According to the disclosure of this invention, the feeder mechanism is preferably in the form of an endless feeder belt rather than a spoked or gear-type feeder wheel with the result that the machine operates much more quietly and again, with much less criticality of dimensional similarity from one spring to the next. 
     In the practice of another aspect of this invention, the feeder mechanism is operable after imparting an arcuate configuration to each strip as it passes over the forming mandrel to sequentially and alternately move the arcuate configured strips over first and second generally circular forming drums. A first stripper mechanism is then operable to strip a first one of the arcuate configured strips from over a first one of the forming drums and onto a top surface of a first stacking drum of less diameter than the forming drum and then strip a second following one of the arcuate configured strips from over the second forming drum onto a top surface of a second stacking drum, which first stripper mechanism is then operable to sequentially and alternately strip following arcuate configured strips from the first and second forming drums onto the first and second stacking drums, respectively, and over the top surface of the preceding strips on the stacking drums to create a pair of nested plurality of arcuate configured strings located on the first and second stacking drums. After a predetermined number of arcuate configured springs are contained in each nest on each stacking drum, a second stripper mechanism is operable to strip those nested sinuous springs from the stacking drums onto a pair of first and second discharge chutes. This use of two forming drums and two stacking drums not only speeds up the machines and the rate at which they may accept and form the curvilinear-shaped sinuous springs into nested stacks of such springs, but also enables each stack to contain identical springs having the same orientation of end sections of the spring even though the springs may have an uneven number of parallel bars over the length of the spring. 
     These and other objects and advantages of this invention will become more readily apparent from the following description of the drawings. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partially diagrammatic perspective view of a machine for practicing the inventive method and machine of this invention with portions of the machine supporting frame and enclosure housing shown in phantom; 
         FIG. 2  is an enlarged perspective view similar to  FIG. 1 , but with a portion of the machine broken away and shown in phantom for clarity purposes; 
         FIG. 3  is a perspective view of a portion of the machine of  FIG. 2 , but illustrating infeed and placement of a first arcuately formed curvilinear sinuous spring, shown partially in phantom, onto a first forming drum of the machine; 
         FIG. 4  is a view similar to  FIG. 3 , but illustrating infeed of a second sinuous spring into the machine preparatory to placement of the second arcuately configured sinuous spring onto the surface of a second forming drum; 
         FIG. 5  is a view similar to  FIG. 4 , but illustrating the infeed of the second arcuately formed curvilinear spring over the second forming drum of the machine; 
         FIG. 6A  is a perspective view of the rightwardmost forming drum only and drum stripping mechanism after placement of a spring over the drum preparatory to stripping of the spring from the forming drum; 
         FIG. 6B  is a perspective view similar to  FIG. 6A  but with a spring clamp assembly activated to hold the spring against axial movement of the spring as the forming drum is moved axially in a leftward direction as viewed in  FIG. 6B ; 
         FIG. 7A  is a perspective view similar to  FIG. 6A  but illustrating the positions of the spring and spring clamp assembly after leftward movement of the forming drum, illustrated in phantom, preparatory to the spring dropping inwardly over the rightwardmost stacking drum; 
         FIG. 7B  is a perspective view similar to  FIG. 7A  but illustrating the position of the spring and spring clamp assembly after leftward movement of the forming drum (not shown) and placement of the spring onto the rightwardmost stacking drum; 
         FIG. 8A  is a perspective view similar to  FIG. 7B  but illustrating the stacking drum and stacking drum striping mechanism after placement of a stack of nested springs over the stacking drum; 
         FIG. 8B  is a perspective view similar to  FIG. 8A  after activation of the rightwardmost stacking drum striper mechanism and a stack or coil of nested stacked springs have been stripped from the rightwardmost stacking drum and dropped into a discharge chute located beneath the stacking drum; and 
         FIG. 9  is a flow chart of the operation of the apparatus and method practiced by the machine of this invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The sinuous spring nesting and stacking machine  10  of this invention comprises a rectangular frame  12  upon which is mounted a sinuous spring infeed mechanism  16  for causing straight discrete lengths  14  of sinuous wire to be fed into and over a rotating mandrel  18  which imparts an arcuate curvilinear shape to those lengths  14  of sinuous wire springs. Those discrete straight lengths  14  of sinuous wire are derived from a conventional continuously operating wire forming machine  2  (see  FIG. 9 ) which continuously feeds sinuous wire into a standard loop accumulator  4  from which the wire is fed into a cut-off machine  6 . From the cut-off machine  6 , the lengths  14  of straight sinuous wire are supplied to the feeder mechanism  16  of the nesting and stacking machine, which is synchronized by a conventional common controller (not shown) with the forming machine  2 , accumulator  4  and cut-off machine  6 . 
     The arcuately formed curvilinear sinuous springs  15  are then caused by the infeed mechanism  16  to be moved alternately over one of two circular forming drums  20 ,  22 . Those forming drums, as explained more fully hereinafter, are caused to reciprocate between two positions such that after a first spring  15  is deposited upon one forming drum  20 , the forming drums are shifted to align the second forming drum with the infeed mechanism preparatory to the next following spring  15  being deposited on the second forming drum  22 . Located internally of these forming drums  20 ,  22  are a pair of smaller diameter stacking drums  24 ,  26  (see  FIGS. 4 and 6A ). As the forming drums  20 ,  22  reciprocate after having a spring  15  deposited thereon, the next following reciprocable stroke of the forming drums causes the springs  15  to be moved off of the forming drum  20 ,  22  and onto the underlying stacking drum  24  or  26 , respectively. Consequently, the sequence is for a first arcuately formed spring  15  to be deposited upon a first forming drum  22 , for example. The drums are then reciprocated rightwardly so as to align the forming drum  20  with the infeed mechanism  18  and position the spring  15  on the drum  22  over the stacking drum  26 . The next leftward movement of the forming drums  20 ,  22 , after a spring  15  is deposited on the forming drum  20 , causes the spring  15  on the forming drum  22  to be moved off of the first forming drum  22  and onto the underlying stacking drum  26 . The next following rightwardly movement of the forming drums  20 ,  22 , the spring  15  causes the spring  15  on the leftward forming drum  20  to be stripped from that forming drum  20  and onto the underlying stacking drum  24 . This procedure is followed until a predetermined number of arcuate curvilinear springs  15  have been alternately and sequentially deposited upon each of the stacking drums  24 ,  26 , after which the stacking drum  26  is moved rightwardly, so as to strip the nested stack of springs on that stacking drum  26  from the stacking drum  26  and allow that stack to fall onto an underlying discharge chute  28  or  30 . The stacking drum  24  is then moved leftwardly and the stack of springs or the stacking drums stripped from that stacking drum  24 . Thereafter, the stacking drums  24 ,  26  are moved back to their original positions beneath their respective forming drums  20  or  22  preparatory to receiving the next following spring  15  from that forming drum. This sequence of operations is all controlled by a common controller (not shown) which synchronizes the drive of the complete machine  10 , including its infeed mechanism  16  with the drive of the sinuous wire forming machine  2 , accumulator  4  and cut-off machine  6 . 
     Nesting Stacking Machine Frame 
     The nesting stacking machine frame  12  is generally rectangular and comprises a front plate  32 , a rear plate  34 , and side plates  36 ,  38 . This frame is illustrated as being bolted together, but could as well be welded or connected via any other conventional connectors. The machine frame  12  is, in turn, mounted upon a base frame and enclosed within a housing  12   a  (shown in phantom in  FIG. 1 ) as is conventional with all machinery having moving parts. 
     Fixedly mounted upon this frame  12  and extending between the side plates  36 ,  38 , there are a pair of supporting shafts  40 ,  42 . These shafts  40 ,  42  extend through apertures (not shown) in the side plates and are secured to the side plates by mounting blocks  44 . The mounting blocks  44  each comprise pairs of blocks  44   a ,  44   b  located on the outside of each end of the shafts  40 ,  42  and secured together by conventional screws so as to clamp the ends of the shafts  40 ,  42  therebetween. The lowermost one of each pair of blocks  44   a ,  44   b  is then secured to the outside surface of the side rails  36 ,  38  by set screws  44   c . As explained more fully hereinafter, these supporting shafts  40 ,  42  then serve as mounting shafts for the reciprocable forming drums  20 , 22  and the mechanism movable with those drums  20 , 22 . These shafts  40 ,  42  also support the independently movably stacking drums  24 ,  26  as well as stationary stacking drum stripper paddles  46 , 48  (see  FIGS. 7A and 7B ) associated with the stacking drums  24 ,  26 . 
     Sinuous Spring Infeed Mechanism 
     The belt drive infeed mechanism  16  is driven from a timing input gear  50  operable through a shaft  52  to drive a drive gear or pulley  54  and, through an endless flexible belt  56 , pair of idler gears or pulleys  58 ,  60 . The flexible endless belt  56  is movable over these gears or pulleys  54 ,  58 ,  60  and has an outside peripheral surface  78  engageable with the top surface of incoming straight lengths  14  of sinuous wire so as to move those lengths  14  of sinuous wire into surface contact with the rotating mandrel  18 . The mandrel  18  is rotatably mounted upon a shaft  62  which is, in turn, fixedly secured to the frame  12 . The complete infeed mechanism  16  is mounted upon a separate frame (not shown) which is, in turn, fixedly secured to the machine frame  12 . The infeed mechanism is so constructed that the intermediate gear or pulley  58  is adjustably mounted so as to enable it to be moved relative to the mandrel  18  and thereby vary the configuration of the arc imparted to the sinuous spring  15  by the mandrel  18  as the wire moves over the mandrel. 
     Spring Stripper Mechanism 
     The mechanism for affecting reciprocable movement of the forming drums  20 ,  22  comprises a pair of air cylinders  64 ,  66  bolted to the outside surface of the side plate  38 . The piston rods  64   a ,  66   a  of these cylinders extend through the side plate  38  and are fixedly connected through an appropriate linkage  70 ,  72  to a slider plate  68  to which the forming drums  20 ,  22  are fixedly attached. This slider plate  68  is sandwiched between the forming drums  20 ,  22  and is connected via the linkages  70 ,  72  to the piston rods  64   a ,  66   a  such that upon simultaneous actuation of the cylinders  64 ,  66 , the slider plate is caused to slide and reciprocate over the supporting shafts  40 ,  42  between the two positions illustrated in  FIGS. 4 and 5 . As may be seen most clearly in  FIGS. 4 and 5 , the slider plate  68  has a bore (not shown) axially aligned with bores  70  in mounting blocks  72 ,  74  located on opposite sides of the mounting plate and secured thereto by bolts  76 . The support shafts  40 ,  42  extend through the axially aligned bores of the slider plate and the mounting blocks  72 ,  74 , thereby enabling the slider plate  68  with its attached forming drums  20 ,  22  to slide over the support shafts  40 ,  42  upon simultaneous actuation of the cylinders  64 ,  68  secured to opposite ends of the slider plate  68  via the piston rods  64   a ,  68   a  and the linkages  70 ,  72 . 
     Proximity Trigger Assembly 
     Adjustably mounted upon opposite sides of the slider plate  68 , there are a pair of proximity trigger assemblies  106 ,  108 . Each trigger assembly  106 ,  108  comprises a pair of parallel plates  106   a ,  106   b  and  108   a ,  108   b  separated by a spring assembly  106   c . These proximity trigger assemblies function as stops as springs wrap around the forming drums  20 , 22  to limit the rotary movement of the spring about the forming drum and stop it when the leading end of a spring  15  contacts the lowermost plate  106   a  or  108   a . There is also a proximity switch (not shown) associated with each of these trigger assemblies such that upon contact of the end of a spring  15  with the lower plates  106   a ,  108   a  of the assembly, the switch is actuated to initiate reciprocable movement of the forming drums as explained more fully hereinafter. 
     Fixedly mounted on the outside of each stacking drum  24 ,  26 , there is a side mounting plate  24   a ,  26   a . These side mounting plates  24   a ,  26   a  serve as mounting plates for skip paddle assemblies  80 ,  82 ,  84  and  86  ( FIG. 2 ). Two of these skip paddle assemblies  80 ,  82  are mounted upon the outside of side mounting plate  24   a , and two others,  84 ,  86 , are mounted on the outside of the side mounting plate  26   a.    
     Each side mounting plate  24   a ,  26   a  has arcuate slots  90  formed therein These arcuate slots are of slightly smaller radius than the radii on the inside of the forming drums  20 ,  22  and are generally aligned with the inside surface of those forming drums  20 ,  22 . Arcuate shaped skip paddles  96  of the paddle assemblies  80 ,  82 ,  84  and  86  are extendable through these slots  90  and engageable with the ends of the springs  15  as those springs are stripped from the forming drums, as explained more fully hereinafter. 
     The skip paddle assemblies  80 ,  82 ,  84   86  are all identical in both configuration and function. Accordingly, only one skip paddle assembly  84  will be described in detail, it being understood that the other skip paddle assemblies  80 ,  82  and  86  mounted upon their respective side mounting plates are identical. 
     With reference to  FIGS. 7A and 7B , it will be seen that each skip paddle assembly comprises a pneumatic cylinder  88  secured by a generally L-shaped cylinder mounting block  92  to a side mounting plate. In the case of the skip plate assembly  84 , the cylinder mounting plate  90  is adjustably mounted upon the side mounting plate  26   a  and is secured thereto by a bolt  94  which extends through the arcuate slot  90 . A paddle  96  is mounted on the inner end of the piston rod  98  associated with each cylinder  88  of each skip paddle assembly. These paddles are arcuately shaped so as to be extendable through the arcuate slots  90  and engageable with the ends of the arcuately configured springs as those springs are moved off of the larger diameter forming drums  20 , 22 . Those paddles engage the ends of the springs and temporarily hold them as the springs move off of the forming drums  20 ,  22 , after which the paddles retract into the arcuate slots  90  so as to permit the ends of the springs to follow the center portions of the springs inwardly into contact with the outside peripheral surface of the stacking drum or the outside peripheral surface of the spring which preceded that formed spring onto the stacking drum. 
     Also with reference to  FIGS. 7A and 7B , it will be seen that also bolted to each of the side mounting plates  24   a ,  26   a , there is a spring location finger  100  which extends radially outwardly from the outside peripheral surface of each stacking drum  24 ,  26 . This finger  100  has an inwardly extending slot  102  formed therein so as to enable a forming drum  20  or  22  to slide into and out of this slot  102 , as explained more fully hereinafter. This finger functions to locate and align springs on the stacking drum as the springs are removed off of the forming drum and onto the stacking drum. In the course of movement from a forming drum and onto a stacking drum, a loop of the spring fits over this finger  100 . Thereby, a stack of springs are all aligned one with the next above it when a stack of nested springs are removed from the stacking drum, as illustrated in  FIGS. 8A and 8B . 
     Spring Clamp Assembly 
     Located on the outside of the forming drums, and rotatably movable between a first position illustrated in  FIGS. 3 ,  6 A and  7 B, and a second position illustrated in  FIGS. 6B and 7A , there are two pair of spring clamp assemblies  130 ,  130   a  and  132 ,  132   a . Since each pair of these assemblies are identical and actuated simultaneously, only one ( 130 ) of one pair  130 ,  130   a  will be described in detail, it being understood that the other  130   a ,  132  and  132   a  are identical, but with one of each pair positioned on the opposite side of the forming drum with which it is associated. 
     Each clamp assembly includes an air cylinder  136  mounted upon a stacking drum mounting plate  24   a  or  26   a  and a pivotal paddle  134  movable between the two positions illustrated in  FIGS. 6A and 6B . To pivotally move the paddle between these two positions, the air cylinder  136  is activated to cause a rotatable piston rod  138  of the cylinder  136  to actuate the paddle  134  and move the paddle into contact with the peripheral surface of a forming drum and hold the spring against axial movement as the forming drum is moved axially from under the spring. Thereafter, the air cylinder  136  returns the paddle  134  to the rest position illustrated in  FIG. 6A . 
     Stacking Drum Stripper Mechanism 
     With reference now to  FIG. 1 , it will be seen that the stacking drum  24 ,  26  stripper mechanism comprises a first air cylinder  110  mounted upon the frame side plate  38  on the left side of the machine for affecting reciprocable movement of the stacking drum  24  and a second air cylinder  112  mounted upon the outside of the right side plate  36  operable independently of the air cylinder  110  for affecting reciprocable movement of the stacking drum  26 . Each air cylinder  110 ,  112  has a stacking drum mounting plate  114  mounted on the outer end of the piston rods  110   a ,  112   a  of the respective cylinders  110 ,  112 . The stacking drum  24  is fixedly attached to the mounting plate  114  at the end of the piston rod  110   a  and the stacking drum  26  is fixedly attached to the mounting plate  114  at the end of the piston rod  112   a  associated with the air cylinder  112 . 
     In order to limit reciprocable movement of the stacking drum  24  toward the side plate  38 , there are a pair of shock absorbers  118 ,  120  mounted on the side plate  38  and an identical pair of shock absorbers  122 ,  124  (see  FIG. 3 ) mounted on the side plate  36 . Each of these shock absorbers has a movable piston rod  118   a ,  120   a ,  122   a  and  124   a  spring biased outwardly and positioned so as to be engageable with the rim  24   a  of the drum  24  when the stacking drum  24  is moved toward the side plate  38  and with the rim  26   a  of the drum  26  when the stacking drum  26  is moved outwardly toward the side plate  36 . 
     Operation of the Spring Nesting and Stacking Machine 
     Referring first to  FIG. 9 , operation of the nesting and stacking machine  10  is synchronized and commences with start-up of a parent sinuous spring forming machine  2 . That machine is a conventional sinuous wire forming machine operative to form a continuous length of wire into a sinuous pattern of formed wire, such as the sinuous wire illustrated in the drawings of this application. That sinuous wire has multiple parallel bars  14   a , each bar of which is connected at its opposite ends to adjacent bars via semi-circular end turns  14   b  extending in opposite directions from opposite ends of each bar  14   a . While the sinuous wire illustrated in the drawings of this application have generally circular end turn sections, that sinuous wire could have end turns of varying configurations, even straight bars. That sinuous wire passes from the forming machine  2  through a conventional loop accumulator  4  to a conventional indexable cut-off machine  6  from whence it is fed via an infeed trackway  8  into the nesting and stacking machine  10 . That trackway feeds the incoming straight lengths  14  of sinuous wire into the infeed mechanism  16 , the endless belt of which forces that straight wire to pass over the mandrel  18  and thereby have an arcuate configuration imparted to the straight length of sinuous wire. The arc imparted to the then arcuately curved wire is of a radius smaller than the radius of the forming drums  20 ,  22  and even slightly smaller than the radius of the stacking drums  24 ,  26 . That arcuately formed curvilinear wire then passes between the peripheral surface of a stacking drum  20  or  22  and a stop block  25  stationarily mounted on the rear end of the machine  10  and secured to the rear plate  34  of the machine frame. 
     With reference to  FIG. 2 , there is illustrated a straight wire spring  14  being fed into and over the mandrel  18 . As there illustrated, that spring, after having an arcuate configuration imparted thereto by the mandrel  18 , as the spring passes over the mandrel and beneath the surface of the belt  58 , is caused to move onto the peripheral surface of the forming drum  22  and to wrap around that drum until the movement of the spring is blocked by contact with the lower plate  108   a  of the proximity trigger assembly  108 . That contact triggers actuation of a proximity switch (not shown) associated with that assembly  108  to initiate cycling of the machine stripper mechanism so as to cause the now arcuately formed curvilinear spring  15  on the forming drum  22  to be moved rightwardly on the forming drum  22  while simultaneously positioning the forming drum  20  in a position beneath the mandrel  18  such that the next following spring will be fed onto the other forming drum  20 . This axial movement of the forming drums  20 , 22  is affected by the simultaneous actuation of the air cylinders  64 ,  66  which cause the slider plate  68 , with its attached forming drums  20 ,  22 , to move rightward, as viewed in  FIG. 4 . In this rightwardmost position, as viewed in  FIG. 4 , the stacking drum  26  is located beneath the forming drum  22 . 
     As viewed in  FIGS. 4 and 5 , the following straight wire spring  14  is then fed over the mandrel and onto the forming drum  20  and continues to wrap around that forming drum until the leading end of that now arcuately formed configurated spring contacts the lower plate  106   a  of the proximity trigger assembly  106  associated with that forming drum  20 . This contact of the end of the spring  15  with the lower plate  106   a  of the proximity trigger assembly  106  actuates the switch associated with that assembly, which, in turn, initiates leftward movement of the slider plate  68  and the forming drums  20 ,  22  attached thereto. 
     Before that leftward movement of the slider plate  68  and attached forming drums  20 ,  22  may be initiated, though, several things need to first happen. The cylinders  136  and the clamping plates  134  associated therewith must be pivoted from the position illustrated in  FIG. 6A  to the position in  FIG. 6B , whereat the inner edge of that plate  134  contacts the peripheral surface of the forming drum  22  near the slider plate  68  so as to hold that spring against axial leftward movement as the slider plate  68  and attached stacking drums  20 ,  22  move leftwardly. Simultaneously, with the actuation of the clamping plate air cylinders  136 , the motors  88  associated with the skip plate assemblies  86  on the rightward side of the frame  12  are actuated so as to cause the skip plates  96  on that side to extend and move inwardly through the arcuate slots  90  in the slider plate  68 . When extended, as illustrated in  FIG. 7A , these skip plates  96  are located beneath the ends of the spring  15  located on the forming drum  22 . As the forming drum  22  moves leftwardly, as indicated by the arrow  93  in  FIG. 7A , the spring is held against axial movement with the forming drum by the clamp plates  134  and the ends of the spring are then temporarily held against movement into contact with the underlying stacking drum until after the forming drum  22  has moved completely out from under the spring  15  previously located on that drum. The skip plates  96  then are pulled inwardly to the position illustrated in  FIG. 7B , and the ends of the springs allowed to drop onto the stacking drum  26 . This temporary holding of the ends of the spring  15  by the skip plates  96  prevents the ends of the springs from becoming entangled with underlying springs on the stacking drums during the stacking of the springs on the stacking drums. 
     This sequence of operation and the reciprocable movement of the forming drums is then repeated when the slider plate  68  and attached stacking drums are next moved rightward after placement of a spring over the forming drum  20  and contact of a spring on the drum with the proximity trigger assembly  108 . The rightward movement of the drums then causes sequential actuation of the clamping plate air cylinder  136  mounted on the mounting plate  24   a  and simultaneously, the actuation of the air cylinder  88  on the plate  24   a  to move the clamping plates  134  and skip plates  96  into positions to prevent rightward movement of the spring  15  on the forming drum  22  and to temporarily hold the ends of the spring  15  as it moves off of the forming drum  22  against inward movement onto the stacking drum  24 . Only after the center portion of the spring has moved inwardly over the stacking drums do the skip plate paddles  96  move inwardly and allow the ends of the spring to drop into contact with the stacking drum  24  or, if a spring has been previously been placed upon that drum, into contact with the spring previously placed on that stacking drum. 
     This leftward and then rightward movement of the forming drums  20 ,  22  is repeated until an appropriate number of springs have been nested and stacked on each of the stacking drums  24 ,  26 . 
     After an appropriate number of springs have been nested and stacked on each of the stacking drums  24 ,  26 , as counted by a counter of the controller (not shown) the cylinder  112  associated with the stacking drum  26  is actuated such that its piston rod and attached mounting plate  114  are caused to move rightwardly and in the course of movement, pull the stack of springs  15  nested thereon off of the stacking drum  26  and allow the nested stack of generally circular configurated springs to fall into the discharge chute  28 . In the course of movement rightward, as viewed in  FIG. 7B , the stripper paddles  46 , which are stationarily mounted on the supporting shafts  40 ,  42 , prevent the springs from moving rightward with the stacking drum  26  and force the springs to move off of that stacking drum. 
     The movements depicted in  FIG. 9  and sequential actuation of air cylinder motors of the machine are all cycled by a conventional controller, which has not been illustrated herein, but which may be readily supplied by a person skilled in this art. 
     While I have described only one preferred embodiment of this invention, persons skilled in this art will appreciate changes and modifications which may be made without departing from the spirit of this invention.