Patent Publication Number: US-6983706-B2

Title: Method of manufacturing cover for a bedding product

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a divisional of U.S. patent application Ser. No. 10/804,923 filed Mar. 19, 2004 entitled “Method For Manufacturing Cover For a Bedding Product and Resulting Product” which is fully incorporated by reference herein. 

   FIELD OF THE INVENTION 
   This invention relates generally to bedding products and more particularly, to a method and apparatus for manufacturing a cover for a bedding foundation. 
   BACKGROUND OF THE INVENTION 
   The sewing of various components of a bedding product such as a mattress or bedding foundation together to form a finished product presents several sewing challenges. One such challenge is the sewing of the components at their respective corners. Attaching an upper decking to a border or side panel of a bedding foundation presents numerous challenges. With one known process, an edge of the upper decking material is sewn to an edge of the side panel or border material along the outer edge of the bedding foundation. The joint between the corner of the upper decking can be precut so that there is no or minimal excess material at the corner. If the corners in the upper decking material are not precut, the machine operator must gather the material to accommodate the extra material at the corners. Unless the operator is particularly skilled, sometimes the result is a rather uneven look, since the bedding foundation components are unwieldy and difficult to maneuver around the corners. Further, since the sewn joint is at the edge of the bedding foundation, the upper decking material is often visible even after a mattress is set on top of the bedding foundation. 
   To provide a better finished appearance, it is also known to attach the bedding foundation border material to the upper decking material at a location inside the outer edge of the bedding foundation, for example, 3–4 inches inside the bedding foundation edge. This type of bedding foundation is known in the industry as a continental bedding foundation. However, to provide a desirable finished appearance, it is necessary to miter the bedding foundation border material as it is formed around the corners of the bedding foundation. Mitering of the bedding foundation border material is accomplished by techniques similar to those described above. While improving the appearance of the finished bedding foundation, the additional labor required substantially increases the manufacturing cost of the bedding foundation. 
   Therefore, there is a need to further improve the process of attaching the upper decking material to the border material of a bedding foundation. 
   Materials used to make bedding products such as mattresses and bedding foundations have been known to burn quickly when ignited. Due in part to a number of deaths each year caused by smokers falling in sleep in bed with a lighted cigarette, there is pressure on manufacturers of bedding products to manufacture a product which is resistant to fire. States have recently enacted new standards regarding open-flame mattress flammability. Bedding manufacturers are attempting to comply with the new state laws by constructing bedding sets which burn more slowly, enabling occupants plenty of time to escape the building in which the sleeping set is located in the event the bedding set ignites. 
   In both seating and bedding products, a welt cord may be incorporated into the product around the perimeter of the product. A lighted cigarette when dropped may fall or roll into a position adjacent the welt cord. Consequently, welt cords such as disclosed in U.S. Pat. No. 4,598,622 have been manufactured to inhibit combustion. 
   Due to the combustible nature of the materials used to manufacture bedding foundations and mattresses, such products may be easily ignitable and once ignited may combust quickly. Air entering between the mattress and bedding foundation or box spring can further fuel the fire and/or speed the combustion of the interior of either the mattress or foundation. A great amount of heat may be generated in a short time frame. 
   Therefore, there is a need for a bedding foundation which inhibits air from entering between the bedding foundation and a mattress resting on top of the foundation. 
   SUMMARY OF THE INVENTION 
   One aspect of the present invention provides a method of manufacturing a cover for a bedding product. The bedding product is preferably a bedding foundation but may be a mattress or any other product. The method involves forming a welt cord by wrapping material around a filler cord, securing the welt cord to a continuous web of border or side panel material to form a welted border or border assembly. The welted border is then measured to a predetermined length, cut and opposite ends of the border material secured together to form a loop of welted border material. The last step in forming the cover is to secure non-skid decking to the loop of border material, the welt cord being sandwiched between the border material and the decking. 
   The welt cord is made from a continuous web of welt material which is folded around a filler cord. One type of welt material which has been used is flame retardant tape three inches wide. However, any other size or material may be used in accordance with the present invention. The filler cord is preferably unwound from a roll, surrounded with welt material also unwound from a roll at a folder. One type of cord which has been used is flame retardant, 0.5 inches in diameter, has kevlar webbing and is supplied by the Atlantic Thread Company. However, cording of any other size or material may be used in accordance with the present invention. Although one type of folder is illustrated, any type of folder may be used in accordance with the present invention. The folder is attached to the front of a sewing machine in any conventional manner. 
   According to another aspect of the present invention, the method of manufacturing the cover involves building fullness into the border material to accommodate the corners of the bedding product. This is accomplished by gathering the border material at selection locations during the sewing of the welt cord to the web of border material. 
   According to another aspect of the present invention, the sewing apparatus of the present invention is a two part apparatus utilizing two different sewing machines. The first sewing machine of the sewing apparatus is used to create a border assembly during the first stage of the process. The second sewing machine is used to sew an upper decking of the cover to a loop of border assembly during a second stage of the process. 
   The first sewing machine of the present invention sews a continuous welt cord to a continuous web of border or side panel material. This part of the sewing apparatus utilizes a cutter to cut a predetermined length of border assembly after the welt cord is sewn onto the web of border material. The sewing machine used in this first stage has a pair of rotatable pullers, the speed of which is controlled by a controller. The capability of programming the first sewing machine to slow the pullers of the sewing machine enables the sewing machine to gather the side or border panel at select locations prior to sewing. This fullness built into the border material of the border assembly permits a bedding manufacturer to create a cover having an upwardly directed welt on top of the bedding foundation after the cover is place around the foundation. The welt cord of the cover is located on the top surface of the bedding foundation and spaced inwardly a fixed distance from the perimeter of the foundation. The welt cord enhances the product&#39;s ability to withstand combustion. 
   According to another aspect of the present invention, the invention provides a unique presser foot secured to a presser foot shaft of the first sewing machine. The unique configuration of the presser foot enables the web of border material to be gathered at select locations prior to sewing the welt cord to the web of border material. The pressure foot has a upper plate with a hole through it which enables the needle of the first sewing machine to pass through the presser foot. The presser foot has a lower plate smaller is size than the upper plate, the lower plate being in front of the needle so that it does not interfere with the reciprocation of the needle. 
   During operation of the first sewing machine, the welt cord is fed between the upper and lower plates of the presser foot. The continuous web of border material is fed underneath the lower plate of the presser foot and pulled rearwardly by a rotatable feed dog which operates at a specified rate so as to pull the web of border material a fixed distance per stitch of the sewing machine. As the feed dog pulls the border material rearwardly past the reciprocating needle, the needle sews the web of border material to the welt cord located above the web of border material. Once the welt cord and web of border material are sewn together, the puller located behind the presser foot pulls the combined welt cord and web of border material further rearwardly. 
   In normal operation, the puller and the feed dog operate at the same stitch rate or rotational speed so that the web of border material and the welt cord move at the same speed. Operation of the sewing machine in this fashion providing a smooth seam or joinder of the welt cord to the web of border material. 
   In order to impart fullness at select locations of the border material (where the corners of the bedding foundation are when the cover is completed and installed), the speed rate of the puller is slowed while the speed rate of the feed dog is maintained. Thus, due to the configuration of the presser foot, the linear speed at which the welt cord is moving slows while the linear speed at which the web of border material moves continues at a faster rate. Thus the border material is gathered or bunched at these locations for a specified distance. Once the desired length of web of border material has been sewed to the welt cord in this bunched manner, the controller increases the speed of the puller to equal that of the feed dog. Then for a specified distance, the welt cord is sewn to the web of border material without bunching of the web of border material. The process is then repeated until four bunches are formed in the web of border material for the four corners of the foundation cover. 
   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 
       FIG. 1  is a perspective view of a bedding foundation having a cover made in accordance with the principles of the present invention. 
       FIG. 2  is cross sectional view of the bedding foundation of  FIG. 1  illustrating a mattress on top of the foundation. 
       FIG. 3A  is a cross sectional view of a web of border material attached to a welt cord to create a border assembly. 
       FIG. 3B  is a cross sectional view of a piece of non-skid decking attached to the border assembly of  FIG. 3A . 
       FIG. 3C  is a cross sectional view illustrating a portion of the cover of  FIG. 3B  placed over a bedding foundation. 
       FIG. 4  is perspective view of a portion of the sewing system of the present invention. 
       FIG. 5  is perspective view of a portion of the sewing system of  FIG. 4 . 
       FIG. 6  is a perspective view of a portion of the sewing system of  FIG. 4 . 
       FIG. 7A  is a perspective view of the presser foot used in accordance with the present invention. 
       FIG. 7B  is a side elevational view of the presser foot of  FIG. 7A . 
       FIG. 8  is a perspective view of a portion of the sewing system of  FIG. 4  illustrating the sewing process. 
       FIG. 9  is a perspective view of a portion of the sewing system of  FIG. 4  illustrating the process of gathering the border material to create fullness in the border assembly. 
       FIG. 10  is a perspective view of a second part of the sewing system of the present invention. 
       FIG. 11  is a perspective view of a closed loop of border assembly. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to the drawings and particularly to  FIG. 1 , there is illustrated a bedding product  10  in the form of a bedding foundation or box spring. Although the bedding product  10  illustrated in  FIG. 1  is a bedding foundation, the method of the present invention may be used to cover any bedding product including a mattress, such as the one shown in  FIG. 2 . 
   Referring to  FIG. 2 , the box spring  10  of the present invention comprises a base  12  to which are secured a plurality of coil springs  14  joined into a spring assembly  15 . The springs  14  extend upwardly from the base  12  in a conventional manner. Each coil spring  14  has an upper end turn  16 , a lower end turn  17  and a plurality of central convolutions  18  therebetween. The upper end turns  16  are preferably coplanar defining an upper surface  20  of the coil spring assembly  15 . Similarly, the lower end turns  17  are preferably coplanar defining an lower surface  22  of the spring assembly  15 . Although coil springs are illustrated, any type of springs may be used in accordance with the present invention. The base  12  is preferably made of wood but may be made of any material. The springs  14  are aligned in tranversely extending rows and longitudinally extending columns, as is conventional. The upper end turns  16  of the outermost columns and rows of springs make up an upper peripheral edge  24  of the bedding foundation. 
   Referring to  FIG. 2 , the base  12  and springs  14  of the bedding foundation  10  are covered with a cover  26 . The cover  26  is made by securing a specified length of border or side panel material  28  to a generally rectangular piece of non-skid decking  30 . The side panel or border material  28  has an exterior surface  29  upon which may be quilted a desired pattern and/or upon which may be printed any desired message. As shown in  FIG. 2 , the border material  28  of the cover  26  is secured to the lower surface  32  of the base  12  with staples  34  or any other suitable means, such as adhesive or weldments. As shown in  FIG. 1 , the piece of non-skid decking material  30  covers the upper surface of the bedding foundation  10 . Although not illustrated, if desired, multiple layers of padding and/or other cushioning materials may be placed above the upper end turns of the coil springs  14  of the foundation  10  inside the cover  26 . 
   Referring to  FIG. 1 , once covered the bedding foundation  10  has a pair of end surfaces  36  which define the length or longitudinal dimension L of the product. Similarly, the covered bedding foundation  10  has a pair of side surfaces  38  which define the width or transverse dimension W of the product. 
   As best illustrated in  FIGS. 1 and 2 , the bedding foundation  10  has a welt cord  40  secured to the cover  26  and spaced inwardly a fixed distance from an upper perimeter  24  of the bedding foundation  10 . The welt cord  40  extends upwardly from the upper surface  20  of the bedding foundation  10  and from the generally planar decking  30 . The welt cord  40  is secured to both the border material  28  and the non-skid decking material  30  in a manner described below. 
   As show in  FIG. 2 , a mattress  42  comprising a plurality of interconnected coil springs  44  is placed on top of the bedding foundation  10  such that the welt cord  40  contacts the lower surface  46  of the mattress. The mattress  42  has an upper surface  48  and side surfaces  50 , as is conventional. Although a mattress with coil springs is illustrated, any other type of mattress may be used in accordance with the present invention. The welt cord  40  forms an air tight seal around the perimeter of the decking  30  of the foundation when the mattress  42  is placed thereon. This gasket or seal formed by the interaction of the welt cord  40  with the lower surface  46  of the mattress  42  slows the combustion of the materials of the bedding foundation and mattress in the event of fire. 
   Referring to  FIGS. 3A through 3C , the method of manufacturing the cover  26  for the foundation  10  is illustrated. First, welt cord  40  is formed in a manner described below. The welt cord  40  is placed above the continuous web of side panel or border material  28  as illustrated in  FIG. 3A . The exterior surface  29  of the web of border material  28  is facing upwardly in  FIG. 3A . The welt cord  40  is then secured to the web of side panel or border material  28 . Preferably this securement occurs on a first sewing machine  51  as shown in  FIG. 4 . The stitches are illustrated in  FIG. 3A  by the numeral  52 . 
   According to one preferred embodiment of the present invention, the border material is 14 inches wide and the stitches  52  are located approximately 0.75 inches from the side edge  53  of the web of border material  28 . See  FIG. 3A . 
   Once the desired length of welt cord  40  has been secured to the desired length of border material  28 , the web of border material  28  and welt cord  40  are cut with a cutter  54  like the one illustrated in  FIG. 4 . For purposes of this document, the combined welt cord  40  and web of border material  28  are referred to as a border assembly  56  or welted border. As shown in  FIG. 11  opposite ends  58 ,  60  of the cut border assembly  56  are sewn or otherwise joined together to form a border loop  62  shown in  FIG. 11 , the welt cord  40  extending outwardly from the exterior surface  29  of the border material  28  proximate the upper edge  64  of the border loop  62 . The lower edge  66  of the border material  28  is located underneath the bedding foundation  10  once the cover  26  is secured to the base  12  of the bedding foundation  10 . See  FIG. 1 . 
   Referring to  FIGS. 3B and 10 , the next step in the process is to secure the generally rectangular piece of non-skid decking material  30  to the border loop  62 , the welt cord  40  being sandwiched between the border material  28  and the non-skid decking  30 . Preferably this sewing step occurs on a second sewing machine  68  partially shown in  FIG. 10 . This second sewing machine  68  is not shown in  FIG. 4  and forms a second part of the sewing system of the present invention. However, this step in the process may occur on any sewing machine including the first sewing machine. 
   Referring to  FIG. 3B , after the perimeter of the piece of non-skid decking  30  is sewn to the border loop  62 , the piece of non-skid decking  30  is then pulled back in the direction of arrow  70  in order to expose the welt cord  40 , as shown in  FIG. 3C . The completed cover  26  is then placed around the spring assembly  15  and base  12  of the bedding foundation  10  in the manner shown in  FIG. 3C  such that the welt cord  40  is spaced inwardly a fixed distance from the perimeter  24  of the upper surface  20  of the bedding product and extends upwardly. 
     FIGS. 4–10  illustrate a two part sewing system  72  used to construct the cover  26  shown in  FIG. 1 . The first part of the sewing system  72  is illustrated generally in  FIG. 4  and the second part of the sewing system  72  is illustrated generally in  FIG. 10 . The second part of the sewing system  72  comprises the second sewing machine  68  which may be any conventional sewing machine. 
   The first part of the sewing system  72  includes a roll  74  of filler cord  76  which is fed into a folder  78 . As shown in  FIG. 5 , one configuration of folder  78  is secured to the first sewing machine  51  with bolts  79 . However, any other type of folder may be secured to the first sewing machine  51  in any desired manner to form the welt cord  40 . The first part of the sewing system  72  further comprises a roll  80  of welt material  82  which is fed into the folder  78  in the manner shown in  FIG. 5 . The folder  78  folds the welt material  82  around the filler cord  76  before the welt material  82  is sewn to the web of border material  28  as shown in  FIG. 8 . 
   Referring to  FIG. 5 , the first sewing machine  51  is mounted on a base plate  84  in a known manner. The first sewing machine  51  includes a presser foot  86  shown in detail in  FIGS. 7A and 7B  and a needle  88  that is reciprocated and carries a needle thread and a bobbin thread in a known manner. The needle thread is preferably Kevlar® thread for fire resistance but may be any type of thread. The first sewing machine  51  is a commercial sewing machine that performs lock stitching. Lock stitching is a known technique of interlacing a needle thread and bobbin thread, which will not be further described here. The presser foot  86  is mounted on a presser foot shaft  90  of the sewing machine by means of a screw  92  as shown in  FIG. 6 . The presser foot shaft  90  is located downstream or behind the needle  88  and reciprocates like the needle. See  FIGS. 5 and 6 . 
   As shown in  FIGS. 5 and 6 , a puller  94  comprises two spaced rotatable wheels  96  mounted on a common shaft  98  and is located downstream of the presser foot shaft  90 . The function of the puller  94  is to pull the web of border assembly  56  after the welt cord  40  is secured to the web of border material  28  in a downstream direction towards the cutter  54 , as shown in  FIG. 4 . The wheels  96  of the puller  94  rotate in a direction indicated by arrow  100  shown in  FIGS. 6 and 8 . 
   The operation of the puller  94  is controlled by a programmable control for example, a commercially available programmable logic controller. The control includes a user input/output (“I/O”) interface that provides various user operable input devices, for example, pushbuttons, switches, etc., as well as various sensory perceptible output devices, for example, lights, a visual display such as an LCD screen, etc. The user I/O permits the user to command the operation of individual servomotors and cylinders connected to outputs of the control. 
     FIGS. 7A and 7B  illustrate the presser foot  86  according to another aspect of the present invention. The presser foot  86  comprises an upper plate  102  joined to a lower plate  104  with a connector  106  shown in  FIG. 7B . The upper plate  102  has a forward portion  108  inclined relative to a rearward portion  110  to provide easy access for the welt cord  40  between the upper and lower plates  102 ,  104 . The rearward portion  110  of the upper plate  102  has a hole  112  therein which enables the reciprocating needle  88  to pass through the presser foot  86  to sew the welt cord  40  to the web of border material  28 . As shown in  FIG. 7B , the lower plate  104  is located in front of the hole  112  so it does not interfere with the operation of the needle  88 . 
   As best illustrated in  FIG. 6 , the first sewing machine  51  has a wheel or feed dog  114  having teeth  116  to grip the material placed thereon and move it downstream. The web of border material  28  is pushed downwardly against the feed dog  114  by the presser foot  86  and moved downstream by rotation of the feed dog  114 . 
     FIG. 8  illustrates the web of border material  28  being moved in the direction of arrow  118  by the feed dog  114  and puller  94 . Once the welt cord  40  is secured to the web of border material  28  the puller wheels  96  located on opposite sides of the welt cord  40  move the combined welt cord  40  and web of border material  28  downstream in the direction of arrow  118 . The rotational speed of the feed dog  114  and the puller wheels  96  are approximately the same so that the web of border material  28  is not bunched during the sewing of the welt cord  40  the web of border material  28 . In one preferred embodiment, the stitch rate is 5 stiches per inch. 
   Referring to  FIG. 9 , after the welt cord  40  has been joined to the web of border material  28  for a predetermined distance, the controller (not shown) slows the rotational speed of the puller wheels  96 , thereby slowing the downstream flow of the border assembly  56  after the welt cord  40  has been joined to the web of border material  28 . At select locations when the rotational speed of the puller wheels  96  has been slowed, the feed rate of the feed dog (not shown in  FIG. 9 ) continues at the same rotational speed it originally had, i.e. it does not slow down when the rotational speed of the puller wheels  96  slows. Therefore, the web of border material  28  is gathered to impart fullness  120  in selected areas, as shown in  FIG. 9 . In a predetermined length of border material used to make a bedding product like the one shown in  FIG. 1 , four such areas of fullness are built into the border assembly to accommodate the four corners of the bedding product. This fullness enables the cover  26  of the bedding foundation  10  shown in  FIG. 1  to fit around the bedding product such that the welt cord  40  extends upwardly from the upper surface of the product and is spaced inwardly a fixed distance from the perimeter of the product. 
     FIG. 10  illustrates a portion of the second sewing machine  68  which is used to sew the piece of non-skid decking  30  to the loop of border assembly  62  shown in  FIG. 11 . This second sewing machine  68  does not require any special presser foot like the one used in the first sewing machine  51 . Therefore, any conventional sewing machine may be used for this step in the process. 
   While the present invention has been illustrated by a description of various embodiments and while these embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. 
   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.