Patent Publication Number: US-6209468-B1

Title: Method and apparatus for sewing handles on a strip of material

Description:
FIELD OF THE INVENTION 
     This invention relates to sewing machines and more particularly to a method and apparatus for sewing handles lengthwise on a strip of material, which strip of material is, for preferred embodiments, a border strip of a mattress. 
     BACKGROUND OF THE INVENTION 
     While handles may be sewn on a strip of material in a variety of applications, perhaps the most common application for such sewing is in sewing handles on the border strip of a mattress, inner spring or the like. Since such handles are used to lift heavy mattresses, they must be strong, one way of achieving such strength being to fold over the ends of the stock used for forming each handle to form a double thickness at the ends where sewing is performed. However, it is also important that the handles have an attractive appearance. The folds, in addition to providing to strength, also give a cleaner look to the ends of the handle. However, for good aesthetic appearance, the folds on both ends of each handle should be of substantially the same length, both layers of each fold should be perfectly aligned and the handle should lie substantially flat against the mattress when not in use. 
     Heretofore, such aesthetically pleasing handles have been achieved only by using semiautomated techniques for sewing the handles, it otherwise being difficult to compensate for skewing of fold ends, stretching of for example the border material which may prevent the handle from laying flat and various factors influencing the length of the folds. However, any machine requiring a skilled operator is more expensive to operate than a fully automated machine and semi-automated machines are also significantly slower. A fully automated machine operating under computer control can also provide greater flexibility in the jobs that can be performed and the way the jobs are performed, for example permitting borders for different sized mattresses to be handled without expensive hand readjustments of the machine. 
     In view of the above, it would be preferable if a machine and a method for the operation thereof could be developed which would permit the filly automated sewing of handles on mattress border stock or other suitable strips of material at relatively high speed while still achieving quality, aesthetically pleasing handles. 
     SUMMARY OF THE INVENTION 
     In accordance with the above, this invention provides a method and apparatus for automatically sewing handles lengthwise on an elongated strip of material, for example mattress border material, which includes the forming of a fold on a leading edge of a handle stock, the moving of the fold to a sewing head where the fold is sewn to the border or other strip of material, the cutting of a sufficient length of handle stock to form the handle and the forming of a fold on a trailing end of the handle at the sewing head where it is sewn to the strip of material, thereby completing the handle. The forming of each handle fold preferably includes method/apparatus facilitating the alignment of the fold. 
     More specifically, the apparatus includes a first handle stock feeding assembly, a second stationary sewing head assembly, a programmably controlled drive for effecting relative movement between the first and second assemblies toward and away from each other and a second programmably controlled drive for feeding the strip of material to and through the sewing head of a sewing head assembly. The first assembly includes an extending guide plate coacting with first components on the second or sewing head assembly as the first drive moves the assemblies toward each other to form a fold in the leading edge of the handle stock and deliver the fold to the sewing head where the fold is sewn to the strip of material. A cutter is also provided on the first assembly for cutting a sufficient length of the handle stock to form the handle. Finally, the extending guide plate coacts with second components on the second assembly to form a fold at the sewing head on a trailing end of the handle, the fold being sewn to the strip of material to complete the handle. 
     In operation, a length of handle stock sufficient to form the first fold extends beyond the end of the guide plate when the guide plate reaches the first components, the first components including a folding bar and a drive moving the bar down over the leading edge of the guide plate to fold the length of handle stock down, the guide plate passing over the bar as the first assembly continues to move toward the second assembly. This results in the bar pressing the length of handle stock against the bottom of the guide plate to form the fold. For preferred embodiments, the folding bar includes a flexible extension or drum thereover which coacts with edge projections or fingers on the guide plate to assure proper alignment for the folded over length of handle stock. The flexible drum preferably also maintains a desired tension on the handle stock. For a preferred embodiment, the sewing head also includes staking needles and a drive mechanism which moves the needles into engagement with each fold when the fold is positioned at the sewing head, removes the staking needles when the fold is clamped by the sewing head and tilts the staking needles out of the way once they have been retracted. An end detector is also provided for the handle, the guide plate coacting with the second components to form the fold on the trailing end of the handle in response to a selected output from the detector. 
     The second components preferably include a rear folding bar and a folding blade, the bar and blade normally being retracted to an inoperative position, and a drive being provided for moving the bar and blade to an operative position at a selected time after the fold at the leading end of the handle has been sewn to the strip of material. The second components also include a drive which moves the folding bar down past a trailing edge of the blade when only a length of the trailing end of the handle stock sufficient to form a fold extends beyond the trailing edge of the blade, the bar folding the trailing end of the handle over the trailing edge of the blade. Finally, a mechanism is provided for folding the trailing end of the handle under the blade to form the trailing end fold on the handle. For a preferred embodiment, the mechanism for folding the trailing end includes the programmably controlled drive moving the guide plate under the blade. The folding bar and/or the foot preferably include components for facilitating alignment of the fold. Alternatively, the second folding bar and the blade may be moved relative to each other so that the bar passes under the blade to fold the trailing end of the handle thereunder. 
     The method for sewing the handles preferably includes the steps of: (a) feeding the strip of material to and through the sewing head, such feeding being programmably controlled; (b) feeding a leading end of handle stock to extend beyond the end of the guide plate on the feed assembly by a length sufficient to form a handle fold; (c) moving a folding bar down past the tip of the guide plate to fold the extending handle stock down over the guide plate; (d) moving the feed assembly toward the sewing head with the guide plate over the fold bar to form a handle fold, this step continuing until the fold is at the sewing head; (e) using the sewing head to sew the fold on the handle stock to the strip of material; (f) cutting the handle stock at a point so as to provide sufficient handle stock to form the handle; (g) continuing step a, the handle now sewn to the strip of material moving therewith; (h) moving a second folding bar and a folding blade into a position adjacent the sewing head with the bar above the handle and adjacent the trailing edge of the blade and with the blade below the handle; (i) detecting when the cut trailing end of the handle reaches a selected position, for example, when a length of this end sufficient to form a fold extends beyond the trailing edge of the folding blade; (j) moving the second folding bar down past the trailing edge of the blade to fold the extending length of material down; (k) moving the feed assembly toward the sewing head with the guide plate under the blade to form a fold on the trailing end of the handle; and ( 1 ) sewing the fold to the strip of material to complete the handle. For preferred embodiments, the following steps are performed after step (d) and after step (k): (m) moving staking needles down into the fold; (n) moving the feed assembly, including the guide plate, away from the sewing head, (o) clamping the fold, and (p) moving the staking needles up and out of the fold and tilting the staking needles out of the way. Step (c) preferably includes utilizing a resilient drum on the folding bar acting in conjunction with edge projections/fingers on the guide plate to align the forward fold, and step (j) preferably includes utilizing spaced collars on the folding bar to align the rear fold. 
     The foregoing other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention as illustrated in the accompanying drawings, common reference numerals being utilized to refer to common elements in the various figures. 
    
    
     IN THE DRAWINGS 
     FIG. 1 is a perspective view of a sewing machine suitable for practicing the teachings of this invention. 
     FIG. 2 is a perspective view of a mattress having handles sewn thereon in accordance with the teachings of this invention. 
     FIG. 3 is an enlarged perspective view of a single hand of FIG.  2 . 
     FIG. 4 is a simplified side view of the sewing machine shown in FIG.  1 . 
     FIG. 5 is an enlarged perspective view of certain assemblies shown in FIG.  1 . 
     FIG. 6 is an enlarged perspective view of a guide plate and related components of the machine shown in FIG.  1 . 
     FIG. 7 is an enlarged perspective view of an alignment drum formed on a folding bar of the machine. 
     FIGS. 8-19 are simplified side views of a portion of the machine shown in FIG. 4 illustrating the relative positions of machine components at various stages in the operation of the machine. 
    
    
     DETAILED DESCRIPTION 
     While the invention may be utilized to sew handles on a strip of material for a variety of applications, for the preferred embodiment to be described hereinafter it will be assumed, as shown in FIGS. 2 and 3, that handles  10  are being sewn on a side binding strip  12  of a mattress or inner spring  14 . Both to achieve a more pleasing aesthetic appearance and for enhanced strength, a fold  16 , which may be best seen in FIG. 3, is provided on each end of each handle, with stitching  18  being performed through each fold  16 . The pattern utilized for stitching  18  may vary with application, and, as will be discussed later, the sewing machine of this invention may be programmed to provide a variety of patterns for stitching  18 . In order to achieve a pleasing aesthetic appearance for handles  10 , the bottom of each fold  16  must align perfectly with the top of the fold, the length of each fold  16  for each handle  10 , and preferably for all the folds  16  of the handles for a given mattress, should be of substantially identical length and all of the handles  10  should lie flat against binding  12  when not in use. Each handle  10  should of course also be perfectly aligned with the top and bottom edges of binding  12  rather than at an angle thereto. In accordance with the teachings of this invention, all of these objectives are achieved while providing a fully automated machine capable of sewing handles at relatively high speed, and, by requiring minimum operator intervention, at relatively low operating cost. 
     FIGS. 1 and 4 are respectively a prospective view of a machine  20  suitable for use in practicing the teachings of this invention and a simplified side view of the machine  20  in operation. Referring to these figures, it is seen that a roll of binding stock  12  is mounted on a spindle  22  supported on an arm  24 , and a roll of handle stock  30  is mounted on a second spindle  26  supported on arm  28 . Binding stock  12  passes through a standard tensioning mechanism  32 , a sewing head assembly  34 , a take away tensioning mechanism  36  and a pair of feed rollers  38 ,  38 ′, at least one of which is driven, for example roller  38 ′, to a pneumatically operated cutter  40 . A take away mechanism can also be provided beyond cutter  40  or the cut binding with the handles sewn thereon may be dropped into a suitable receptacle. 
     Handle stock  30  passes to a handle stock feed assembly  42  which includes an optical end of stock detector  44 , a pair of feed rollers  46  and  46 ′, one of which, for example roller  46 ′, is driven, a pneumatically driven cutter mechanism  48 , a detector  50  at the leading edge of the assembly and a projecting guide plate  52  over which handle stock  30  passes. Guide plate  52  has a pair of spaced slots  53  (FIG. 6) formed in its leading edge and has a pair of projections or fingers  55  extending a short distance from each side of its leading edge, the spacing between fingers  55  being equal to or slightly greater than the width of handle stock  30 . All of these components are mounted to a vertical arm  54  which is connected by a horizontal bar  56  (FIG. 1) to a nut  58  on a worm gear  60  driven by a motor  62 . In FIG. 4, nut  54  and worm gear  60  are shown as covered by a cover  64 . Motor  62  is a programmably controlled servo motor, the functioning of which will be discussed in greater detail in describing the operation of machine  20 . 
     Sewing head assembly  34  includes sewing head  70 , which may be of standard design; staking needle assembly  72 , which includes staking needles  73 , pneumatic actuators  75  for raising and lowering the staking needles, and pneumatic actuators  77  for tilting actuators  75  and needles  73  between an operative position and an out-of-the-way inoperative position; clamping plate  74 ; and a fold roller  76  having a slightly eccentric flexible extension or drum  78  mounted thereon. Drum  78  is preferably formed of a resilient drum spring covered with silicon rubber to provide the drum with tackiness. Drum  78 , which may be best seen in FIG. 7, is eccentrically mounted at, for example, a 45° angle to equalize tension applied thereby. Bar  76  is raised and lowered by a pneumatic mechanism  79  (FIG.  5 ). 
     The machine also includes an assembly  80  which is best seen in FIG.  5 . Assembly  80  is mounted to the housing of sewing head assembly  34  by a bracket  82 . A pneumatic cylinder  84  is attached to and extends from bracket  82 . Arm  86  extending from pneumatic cylinder  84  is attached at its distal end through a linkage  88  to a plate  90  supporting a pair of pneumatic cylinders  92  and  94  and a pair of anti-rotation guide supports  95  and  97 . A folding blade  96  is connected to the end of an arm extending from pneumatic cylinder  92  and a folding bar  98  is connected at the end of an arm extending from pneumatic cylinder  94 . A pair of alignment collars  99  are either formed or mounted on bar  98 . Both blade  96  and folding bar  98  extend back toward the sewing head, but are spaced away from the sewing head as shown in FIG. 1 when pneumatic cylinder  84  extends arm  86  as shown in FIGS. 1 and 5. However, when pneumatic cylinder  84  is activated to retract arm  86 , blade  96  and bar  98  move adjacent to sewing head for purposes to be discussed later. 
     Finally, machine  20  includes a control panel or operator interface  100 , including a display screen  102  and pressure sensitive input keys  104  which may be utilized by an operator to select various machine parameters, including the size of the mattress, the stitch pattern  18  for the handles and, where applicable, the thickness or type of material being used for stocks  12 ,  30  and other system variables. These inputs are fed to a control computer  106  which utilizes this information to control motor  62 , the motors controlling the various feed rollers, including rollers  38  and  46 , the various pneumatic cylinders, the sewing head, including the sewing pattern used by the head, and any other components of the system involved in the automatic operation thereof. As will be discussed below, except for the loading of control information on interface  100 , the only operations on machine  20  which are manually performed are the mounting of rolls of stock  12  and  30  on spindles  22  and  26  respectively and the initial threading of this stock to the appropriate feed rollers. 
     In operation, a full roll of border stock  12  is mounted on spindle  22  and the leading edge of the border material is fed through tensioning device  32 , under sewing head  70 , through tensioning device  36  and feed rollers  38  and past cutter assembly  40 . The operator may either carefully position the end of border material  12  so that the quantity of this material beyond sewing head  70  is known with reasonable precision, or preferably cutter  40  may be operated before sewing operations begin so that the location where the first handle is to be sewn may be precisely determined relative to the leading edge of border material stock  12 . A roll of handle stock  30  is also mounted on spindle  26  and this stock is hand fed past feed rollers  46 . 
     At the beginning of a handle sewing operation, the components of machine  20  are positioned generally as shown in FIG. 8 with assembly  42  in a retracted position spaced to the left from sewing head assembly  34 , fold bar  76  in a raised position, pneumatic cylinder  84  operated to extend arm  86 , moving assembly  80 , and in particular folding blade  96  and folding bar  98 , away from the sewing head, and staking pins  73  raised and tilted out of the way. The final operation in getting to the state shown in View  1  is for drive rollers to be operated until detector  50  detects the leading edge of handle stock  30 , and for the feed rollers to then continue to be operated for a precise additional number of revolutions to advance handle stock  30  so that a precise length  98  of the handle stock extends beyond the leading edge of guide plate  52 , this precise amount being the amount required to form a handle fold  16 . 
     Referring now to FIG. 9, two things have happened. First, motor  62  has been operated to turn worm gear  60 , moving feed assembly  42  to the left toward sewing head assembly  34  until fold bar  76  is adjacent the leading edge of guide plate  52 . Pneumatic mechanism  79  is then operated to move fold bar  76  down past the leading edge of guide plate  52  to fold length of handle stock  98  extending beyond the end of guide plate  52  downward. As may be best seen in FIG. 6, guide fingers  55  extend slightly beyond the ends of guide plate  52 , the spacing between fingers  55  being substantially equal to the width of handle stock  30 . The width of drum  78  on fold bar  76  is also substantially equal to the width of the handle stock and is positioned so that the drum passes between fingers  55  as fold bar  76  passes adjacent the tip of guide plate  52 . Drum  78  and extending fingers  55  thus coat to force the handle stock being folded by bar  76  between fingers  55  so as to assure alignment of the two sides of the fold  16  being formed, and thus to assure proper alignment of the handle. Bar  76  stops just under guide plate  52  with drum spring  78  exerting pressure on the underside of the guide plate, and thus on the fold of handle stock pinched between guide plate  52  and the drum spring. This maintains tension on the end of the handle stock  30  and also starts to fold material extension  98  under guide plate  52  as shown in View  2 . 
     Referring to FIG. 10, feed assembly  42  continues to be moved to the left toward sewing head assembly  34 , with guide plate  52  passing over rod  76  and flexible drum  78  thereon, the rod and drum flattening extending portion  98  against the underside of the guide plate to form a fold on the leading edge of the handle stock. By the time drum  78  is adjacent the rear tip of extending portion  98 , guide plate  52 , with fold  16  form thereon is located under the sewing head. 
     At this point, staking pin assembly  78  is operated to move the staking needle, which have heretofore been in a tilted position out of the way, to a substantially vertical position (FIG. 11) and to pneumatically drive these needles into fold  16 , the needles passing through slots  53  in guide plate  52 , to hold the fold in place. Once the staking needles are in place, feed assembly  42  may be moved to the right as shown in FIG. 12 to withdraw guide plate  52  from fold  16 . Clamp  74  of the sewing machine may then be lowered (FIG. 13) to press fold  16  against binding stock  12  and to press both the fold and binding stock against a backing plate  75 . The removal of guide plate  52  from the fold and the activation of the sewing machine clamps can occur substantially concurrently. Once the fold has been clamped, staking needles  73  may be retracted by pneumatic actuators  75  and the needles tilted out of the way by pneumatic actuators  77  (FIG.  13 ). When these operations have been completed, the fold  16  of handle  10  may be sewn to binding stock  12  by sewing head  70  utilizing the programmed stitch pattern previously selected. 
     Once the sewing operation has been completed, the sewing clamp is deactivated to release the handle and binding stock. At roughly the same time, cutter blade  48  is operated to cut handle stock  30 , the handle stock to the left of the cut being sufficient to form a single handle  10 . Once the front fold of handle  10  has been sewn to binding stock  12 , advancing the binding stock through the operation of feed rollers  38  also results in an advancing of handle  10 . Thus, referring to FIG. 14, once a sewing operation has been completed, cutting blade  48  is pneumatically operated to cut handle stock  30 , leaving material for a single handle attached to the binding stock. The binding stock is then advanced about 2 inches at which time pneumatic cylinder  84  is energized to move folding blade  96  and folding bar  98  adjacent sewing head  20 . At this time, pneumatic cylinder  92  is operated to retract or lower blade  96  and pneumatic cylinder  94  is operated to raise folding bar  98  so that, as shown in FIG. 15, when these components are moved adjacent the sewing head, folding blade  96  is under the stock for handle  10  and folding bar  98  is above the handle stock. 
     During the next step in the operation, as shown in FIG. 16, folding blade  96  is moved up by cylinder  92  and, substantially concurrent therewith, feed assembly  42  is moved to the left by motor  62  in the manner previously discussed until detector  50  is spaced from the trailing edge of blade  96  by a distance roughly equal to the desired length of the rear fold, which length is substantially equal to the length  98  of the forward fold, this position being shown in FIG.  17 . Rollers  38  continue to move binding stock  12  and handle  10  sewn thereto to the left as these operations are occurring. When the trailing edge of handle  10  is detected by detector  50 , the drive for feed rollers  38  is stopped and motor  62  is operated to back off feed assembly  42  as shown in FIG.  17 . Also as shown in View  10 , folding bar  98  is lowered by cylinder  94  to bring the rear side of handle  10  against the trailing edge of folding blade  96 , roller  98  being closely adjacent to the trailing edge of the blade. Collars  99  on roller  98 , which are spaced by roughly the width of handle  10 , function to properly align the rear fold of the handle as this fold is being pushed down over the trailing edge of folding blade  96 . The collars may be slightly tapered to facilitate this alignment function. 
     Once this operation has been completed, assembly  42  is again moved to the left toward the sewing head by motor  62 , guide plate  52  at this point passing under blade  96  to tuck the rear fold of the handle under folding blade  96  as shown in FIG. 18 to complete the reverse rear fold. Fingers  55  also perform an alignment functions during this operation. The fold is slightly longer than folding bar  96  so that, when these operations are completed, pneumatic actuators  77  and  75  may again be operated in that order to drive staking needle  73  into the leading edge of the fold (FIG.  19 ). 
     When these operations have been completed, the folding blade is moved down by cylinder  92  and motor  62  is again operated to retract assembly  42  and in particular to remove guide plate  52  to, for example, the position shown in FIG.  19 . Substantially concurrent with these operations, sewing machine clamp  74  is activated and cylinder  84  is activated to extend arm  86 , removing blade  96  from the fold and removing assembly  80  out of the way. Once these operations have been completed, staking needles  73  are removed and tilted out of the way in the manner previously described and the sewing head is activated to sew the rear fold of handle  10  to border stock  12 . 
     One major advantage of the procedure described above for sewing the rear fold of the handle is that, by detecting when the trailing edge of handle  10  is in position for the rear fold rather than relying on border stock  12  being moved by drive rollers  38  the required distance to bring the rear side of the handle to the desired position, any errors in positioning the handle stock for forming the rear fold as a result of stretching of the border stock is eliminated, resulting in greater uniformity in handle lengths and significantly reducing the likelihood of slack in the handle after sewing so that the handle will lie flat against the border stock. 
     Once the operations described above have been completed, rollers  38  are operated to advance border stock  12  to bring the location where the next handle is to be sewn adjacent sewing head  70 , rollers  46  are operated to bring a length of handle stock  98  beyond the end of guide plate  52  and the machine is otherwise set up as shown in FIG.  8  and FIG. 19 to sew the next handle on border stock  12 . When all four handles  10  for a given piece of border stock have been sewn, rollers  38  advance the border stock with the handles sewn thereon until the end of the border stock is adjacent cutter  40 , cutter  40  being then operated to complete the fabrication of a single border. This advancing may be interrupted to sew the first handle on the next border if appropriate. When detector  44  detects that the end of a roll of handle stock  30  has been reached, computer  106  will determine if there is sufficient handle left to complete the handle currently being sewn. If not, the operation will be terminated at that point until a new roll of handle stock is mounted on spindle  26  and an operator restarts the operation. If there is sufficient handle stock to complete the handle being sewn, this operation is completed before the operation of the machine is stopped. 
     While the discussion of above is with reference to a preferred embodiment, it is apparent that many variations on the details of operation for this embodiment are possible. For example, in FIG. 18, rather than using guide plate  52  to tuck the end of the rear fold under blade  96 , roller  98  could be moved under the blade by a suitable mechanism to effect this tuck, blade  96  could initially be positioned past the sewing head and moved back over roller  98  to effect this operation, or relative movement between these components could be achieved in some other way. Similarly, the location of detectors  44  and  50  could be varied, although, for reasons discussed above, the current locations are considered preferable. Hydraulic, electromagnetic or other suitable actuators, or electric motors could be substituted for various of the pneumatic actuators, the component moved to effect relative movement between two components may be varied, and other suitable variations could be made in the specific components used and in the sequences of operation to achieve the desired results. Thus, while the invention has been particularly shown and described above with reference to a preferred embodiment, it should be understood that this embodiment is for purposes of illustration only and that the foregoing other changes in form and detail may be made therein by one skilled in the art while still remaining within the spirit and scope of the invention, which is to be defined only by the appended claims.