Patent Publication Number: US-6698166-B2

Title: Pocket spring assembly and methods

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of U.S. application Ser. No. 09/917/479, filed Jul. 27, 2001 now U.S. Pat. No. 6,467,240, which is a divisional application of U.S. application Ser. No. 09/273,394, filed Mar. 22, 1999 now U.S. Pat. No. 6,315,275, which is a continuation in part application of U.S. application Ser. No. 08/995,857, filed Dec. 22, 1997 now U.S. Pat. No. 6,029,957, which is a continuation in part of U.S. application Ser. No. 08/500,904, filed Sep. 18, 1995 now U.S. Pat. No. 5,699,998. The complete disclosures of all these references are herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to pocket spring assemblies, and in particular to pocket spring assemblies for use in cushions or mattresses. More specifically, the invention relates to apparatus and methods for efficiently producing pocket spring assemblies having a two-dimensional array of pocketed springs. 
     Most pocket spring assemblies are constructed of two-dimensional arrays of coil springs contained in individual fabric pockets. Such a construction is often referred to as the Marshall construction, being named after its inventor. Although the Marshall construction has provided a desirable level of cushioning performance for almost a century, its usage has been limited for a variety of reasons, primarily being limited by its high cost of manufacture. 
     For example, one common way of constructing pocket spring assemblies is by producing strings or linear arrays of pocketed springs which are subsequently joined together to form a two-dimensional array of pocketed springs. U.S. Pat. No. 4,234,983 describes one common way of forming strings of pocketed springs which can then be joined together to form a two-dimensional array of pocketed coils. Similar patents describing methods and apparatus for constructing strings of pocketed coils are U.S. Pat. Nos. 4,854,023 and 4,986,518. The complete disclosures of all these patents are herein incorporated by reference. 
     U.S. Pat. No. 4,578,834 describes techniques for joining strings of pocket springs to form a two-dimensional array of pocketed springs. In this patent, the strings of pocketed springs are connected to each other by an adhesive that is applied between lines of tangency of adjacent coil springs. A hot melt adhesive applicator transverses a string of pocketed coils, depositing a precise amount of adhesive on each coil jacket. A second string is positioned on the first, and pressure is applied thereto. The applicator then traverses the second string in the same manner as the first. The sequence is repeated until a spring assembly of desired size is created. The complete disclosure of this patent is herein incorporated by reference. U.S. Pat. No. 4,234,984 describes another method for joining adjacent strings of pocketed springs by alternately connecting the interior string of springs to the adjacent string on either side. 
     In summary, common prior art techniques for forming two-dimensional arrays of pocketed springs include the steps of forming strings of pocketed springs and then joining the strings together. Unfortunately, such a process is time consuming and inefficient, thereby increasing the cost of the pocket spring assembly. Hence, it would be desirable to provide a more efficient way to make a two-dimensional array of pocketed springs to thereby reduce the overall cost of the spring assembly. In particular, it would be desirable to provide a way to join strings of pocketed assemblies while the strings are being formed. In this way, a two-dimensional array of pocketed springs may be formed in a single, continuous process. 
     SUMMARY OF THE INVENTION 
     The invention provides exemplary fabric quilts, pocket spring assemblies, and apparatus and methods for producing such fabric quilts and pocket spring assemblies. The invention also provides exemplary mattresses incorporating such pocket spring assemblies. In one exemplary embodiment, a pocket spring assembly comprises a plurality of elongate fabric tubes disposed adjacent to each other. Each of the fabric tubes has a plurality of pockets into which a spring is disposed. Further, at least some of the pockets of adjacent fabric tubes are welded together at midpoints on the adjacent pockets, i.e. at locations where adjacent springs in adjacent tubes are closest to each other. Such a construction is preferably accomplished by welding together adjacent pockets utilizing welders which are disposed within the pockets. By utilizing a heat fusible material to construct the fabric tubes, the welder heat fuses the material together to produce an internal weld. In this manner, adjacent fabric tubes may be joined together just prior to depositing springs within each of the tubes so that the resulting pocket spring assembly is produced in a single, continuous process. 
     Each fabric tube preferably has a longitudinal axis, and each spring has a central axis about which the spring is coiled. The central axis of each spring is preferably oriented so that it is generally perpendicular to the longitudinal axis of the fabric tube. In one aspect, each fabric tube includes a plurality of closed segments which are spaced apart from each other to form the pockets. The closed segments preferably comprise welds that are generally perpendicular to the longitudinal axis of the fabric tubes. 
     The invention further provides an exemplary mattress which includes a pocket spring assembly having a plurality of elongate fabric tubes which each include a plurality of pockets into which springs are disposed. At least some of the pockets of adjacent tubes are welded together at midpoints on the adjacent pockets as described above. The mattress further includes at least one layer of padding material that is disposed on a top side of the spring assembly. A fabric cover is positioned over the spring assembly and the layer of padding material. 
     The invention also provides an exemplary method for producing a fabric quilt assembly. According to the method, a plurality of separate fabric tubes which are disposed laterally adjacent each other are simultaneously formed. A closed segment is simultaneously formed in each of the fabric tubes, and adjacent tubes are simultaneously joined together proximate the first closed segment. 
     In one aspect, the adjacent tubes are joined by welding the adjacent fabric tubes from within the fabric tubes. In another aspect, the closed segments are formed and the adjacent tubes are joined at substantially the same time. 
     The invention still further provides an exemplary method for producing a pocket spring assembly. According to the method, a plurality of fabric tubes are formed. A first closed segment is formed in each of the fabric tubes, and adjacent tubes are joined proximate to the first closed segment. A spring is placed adjacent to the first closed segment of each fabric tube. Preferably, the adjacent tubes are joined together before placement of the springs adjacent to the first closed segment. A second closed segment is then formed in each of the fabric tubes in a manner such that the springs are disposed between the first and the second closed segments in a fabric pocket. Once each fabric has received a first spring, a second spring is placed behind the second closed segment after first joining adjacent tubes proximate to the second closed segment. A third closed segment is then formed in each of the fabric tubes behind the second springs. This process is then repeated as many times as needed to produce the desired size of the pocket spring assembly. In this manner, a way is provided to produce a two-dimensional array of pocketed springs in a continuous process. 
     In one particularly preferable aspect, adjacent tubes are joined together by welding the adjacent fabric tubes from within the fabric tubes. In this way, the two-dimensional array of pocketed springs may be formed in a continuous process, without the need to separately join strings of pocketed springs as with conventional prior art techniques. 
     In another particular aspect, the method utilizes a plurality of parallel guide members which each has a longitudinal axis and a longitudinally oriented channel. In this way, at least a section of each of the fabric tubes is placed over the guide members, and the springs are introduced through the channels until they exit the guide members and expand within the fabric tubes. Preferably, the adjacent tubes are joined together while the fabric tubes remain over the guide members to allow the pocket spring assembly to be formed in situ. For example, the fabric tubes are preferably advanced over guide members after a spring has been inserted and the second closed segment has been formed so that an additional row of springs may be introduced through the guide members and a closed segment formed behind each of the springs in the row. 
     Each of the springs has a central axis about which the springs are coiled, and the central axis of each spring is preferably perpendicular to the longitudinal axis of the guide members when introduced through the channels. Further, the first and the second closed segments are preferably produced by welds that are generally perpendicular to the longitudinal axis. In another aspect, each fabric tube is formed from a single piece of fabric. Preferably, two side edges of each piece of fabric are welded together along a longitudinal line to form the fabric tubes. 
     The invention also provides an exemplary apparatus for producing a pocket spring assembly. The apparatus comprises a plurality of parallel guide members which each have a longitudinal axis and a longitudinally oriented channel. The guide members are each configured to be received into at least a section of a fabric tube. An advancement mechanism is provided to selectively advance the fabric tubes over the guide members. The apparatus also includes a dispensing mechanism to dispense compressed springs through the channels and into the fabric tubes. When dispensed, a central axis of the springs is perpendicular to the longitudinal axis. A connection mechanism is provided to produce closed segments in the fabric tubes to form a fabric pocket around each spring. Further, a joining mechanism is provided to join adjacent fabric tubes before dispensing of the springs. In this way, an apparatus is provided for producing a two-dimensional array of pocketed springs in situ, i.e., while at least a portion of the fabric tubes remain over the guide members. 
     In one particular aspect, a compression mechanism is provided to compress the springs so that they may be inserted through the channels. The apparatus preferably also includes at least one folding element that is associated with each guide member. The folding element is configured to form a piece of fabric into one of the fabric tubes. Fabric welding mechanisms are preferably also provided to weld two ends of the pieces of fabric together to form the fabric tubes. 
     In one particularly preferable aspect, the connection mechanisms each comprise a pair of jaws to produce a weld in the tubular fabric sections generally perpendicular to the longitudinal axis. The joining mechanisms preferably each comprise welders to produce welds between the adjacent tubular fabric sections, with the welds being made from within the tubular fabric sections. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a top view of a guide member and associated components employed to produce a two-dimensional array of pocket spring assemblies when used in combination with multiple similar guide members according to the invention. 
     FIG. 1B is a side view of the guide member and associated components of FIG.  1 A. 
     FIG. 1C is an end view of the guide member and associated components with FIG.  1 B. 
     FIG. 2 is a vertical section through a spring assembly produced by the apparatus of FIGS. 1A-1C, on a line extending parallel to and between adjacent fabric tubes. 
     FIG. 3 is a general arrangement plan of a particularly preferably embodiment of a pocket spring forming apparatus according to the invention. 
     FIG. 4 is a perspective view of part of a spring feed zone of the apparatus of FIG.  3 . 
     FIGS. 4A,  4 C,  4 D,  4 F and  4 H are fragmentary vertical sectional views, and FIGS. 4B,  4 E,  4 G and  4 I are fragmentary broken away plan views illustrating the transfer of a spring from a conveyor and into a spring assembly according to the invention. 
     FIG. 5 is a perspective view of part of a tube forming and cross-welding zone of the apparatus of FIG.  3 . 
     FIGS. 6A and 6B are simplified fragmentary lateral vertical sections illustrating operation of fabric feeding elements shown in FIG.  5 . 
     FIGS. 7A and 7B are lateral vertical sections through fabric tube forming assemblies shown in FIG.  5 . 
     FIG. 7C is a top view of the fabric tube forming sections of FIG. 7B showing thermal welding elements in a sealing position. 
     FIG. 8 is a section through a single tube forming assembly on the line  8 — 8  in FIG.  9 . 
     FIG. 9 is a section of the line  9 — 9  in FIG.  8 . 
     FIG. 10 is a front perspective view of a single fabric tube forming assembly. 
     FIG. 10A is a perspective view of an operating lever of FIG. 10 for moving thermal welding elements of FIG.  10 . 
     FIGS. 10B and 10C illustrate the operation of the operating lever of FIG.  10 A. 
     FIGS. 10D and 10E illustrate a simplified view of the fabric tube forming assembly of FIG. 10 showing the passage of a spring through a central channel. 
     FIG. 11 is a perspective view of part of a pulling and spring pocketing zone of the apparatus of FIG.  3 . 
     FIG. 11A is a perspective view of a lead screw drive mechanism for moving a row puller carriage in the pulling zone of FIG.  11 . 
     FIG. 11B is a perspective view of a drive motor and toothed belt drive arrangement for driving the lead screw drive mechanism of FIG.  11 A. 
     FIG. 12 is a side view of pulling elements of FIG. 11, illustrating a pulling cycle. 
     FIG. 13 is a side view of the pulling and spring pocketing zone of FIG.  11 . 
     FIGS. 13A and 13B are cross-sectional side views of FIG. 13 showing pocket welding elements. 
     FIGS. 14A and 14B are fragmentary frontal views illustrating the operation of the pocket welding elements. 
     FIG. 15 is a simplified fragmentary cut-away plan view of the pulling and spring pocketing zone showing elements used to sever a completed spring assembly. 
     FIG. 15A is a cross-sectional view of the pulling and spring zone of FIG.  15 . 
    
    
     DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENTS 
     The invention provides exemplary apparatus and methods for producing fabric quilts and pocket spring assemblies. The pocket spring assemblies of the invention are preferably constructed so that they include a two-dimensional array of springs which are disposed within fabric pockets. Preferably, each of the fabric pockets is formed within an associated fabric tube. Further, each of the fabric tubes are joined together at spaced apart locations to form the two-dimensional array of pockets. One particularly important feature of the invention is that the pockets are created, the springs are inserted, and adjacent pockets of adjacent tubes are joined together in one continuous process. In this way, a two-dimensional spring assembly may be formed without the need for separately joining individual strings of pocketed springs as with previously proposed techniques. In this way, an extremely efficient method is provided for producing two-dimensional arrays of pocketed spring assemblies, thereby significantly reducing the cost to produce such spring assemblies. 
     The pockets of the invention are preferably formed using a welding process where a heating element is forced against an anvil. Adjacent pockets in adjacent fabric tubes are preferably joined together in a similar manner. However, it will be appreciated that various other joining or connection techniques may be employed, including gluing, stapling, application of one or two part fasteners, ultrasonic welding, and the like. 
     Referring now to FIGS. 1A-1C, modifications to the apparatus described in WO 94/18116 and U.S. Pat. No. 5,699,998 to integrate the production of joined adjacent fabric tubes with the formation of a two-dimensional pocket spring assembly will be described. The equipment shown in FIGS. 1A-1C is also described in PCT Application No. PCT/CA98/01188, filed Dec. 22, 1998, and co-pending U.S. application Ser. No. 08/995,857, filed Dec. 22, 1997. The complete disclosures of all the references in this paragraph are herein incorporated by reference. 
     The equipment shown in FIGS. 1A-1C comprises an assembly  70  having a guide member  72  through which compressed springs are advanced by one spring diameter each time a new spring is inserted. For convenience of illustration, only one assembly  70  is shown. However, it will be appreciated that the spring assembly apparatus will include a row of substantially identical assemblies  70  which are placed adjacent to each other. Guide member  72  includes a pair of openings  71  to in part reduce the frictional engagement between guide member  72  and the springs which are inserted through guide member  72 . At a forward end of each guide member  72  is pivoted upper and lower arms  74 , each actuated by a small air cylinder  73  between extended and retracted positions. Arms  74  are opened to form upper and lower folds in the fabric tube to allow a fastening mechanism to apply fasteners as described in U.S. Pat. No. 5,699,998, previously incorporated by reference. Alternatively, as described below, arm  74  and air cylinder  73  may be eliminated and a vertical welding mechanism employed to produce vertical welds in the tubes which form the pockets around the springs. 
     Assembly  70  further includes a tubular sleeve  100  which terminates just proximal to openings  71  and provides a surface for supporting a quilt  24  which is formed in situ, i.e., on multiple assemblies  70 , from a plurality of webs of material  102  drawn from spools (not shown). Each web of material  102  is associated with one assembly  70  so that a fabric tube may be formed around each assembly  70  using a single web of material. Each web  102  is conveniently folded to double on its associated spool, and the spool is oriented with its axis parallel to each assembly  70  so that each web  102  moves upwardly towards sleeve  100  and presents a fold  104  towards the rear of the machine. Forward edges  106  of web  102  pass into diagonal slots  108  in a folding guide  110 , which like tubular member  100  is supported from a fixed member  112 . Pulling of quilt  24  forwardly over tubular member  100  results in slots  108  and folding guide  110  folding web  102  around tubular member  100  so that edges  106  overlap to form a fabric tube. 
     Within tubular member  100 , actuators  114  and  116 , typically pneumatically operated, are provided carrying movable jaws  124 ,  126  and  128 . Jaw  124  cooperates with a fixed jaw formed by an anvil  134  on folding guide  110  to form longitudinal welds on the lapped edges  106  of web  102  and thus seam it into a fabric tube. Jaws  126  and  128  cooperate with corresponding jaws in an adjacent assembly (not shown) so as to weld the fabric of adjacent fabric tubes together at vertically spaced connections. The spacing of the vertically spaced connections is preferably similar to the connections formed in the folds of the upper and lower layers of fabric of each fabric tube to separate rows of springs in the tubes. Preferably, the welds placed between the springs in each fabric tube is accomplished by utilizing pairs of welding jaws and anvils that are associated with each assembly  70 . These welding jaws are preferably mounted above and below the outer ends of guide members  72 . Such an arrangement enables a long welding cycle to be provided between each draw of quilt  24  for all of the welding mechanisms used, in each of which the jaws may be closed against each other through the two layers of fabric to be welded. Conveniently, a heating element associated with at least one of the jaws is activated to fuse the fabric material. The jaws may then remain closed with the heating element deactivated while the weld sets. The time available for such a cycle is that required to insert a complete row of springs so that there is ample time to set the welds before they are subjected to stress. Optionally, arms  74  and cylinder  73  may be eliminated, with the vertically oriented welds between the springs being created by the jaws which pinch the fabric together. 
     Referring now to FIG. 2, an exemplary spring assembly  2  which is formed utilizing a plurality of assemblies  70  of FIGS. 1A-1C will be described. Spring assembly  2  of FIG. 2 is shown in cross-section such that only one column or string of springs  10  is shown. For example, the string of springs shown in FIG. 2 would be produced by one assembly  70  as shown in FIG.  1 A. As such, spring assembly  2  is formed from a single web of fabric  102  as previously described in connection with FIGS. 1A-1C. Each web  102  that is formed into a tube is connected with an adjacent fabric tube by spaced connections  8 A. These connections are formed by jaws  126  and  128  as previously described. The vertical welds between each spring  10  are referenced by reference numeral  16  and are formed by the vertically oriented welding jaws as previously described. After two pairs of welds  16  are formed, they define a pocket  14  into which spring  10  is disposed. 
     Hence, with the modification of FIGS. 1A-1C, spring assembly  2  includes welds  8 A which provide connections between each pocket  14  and an adjacent pocket in an adjacent fabric tube, with each connection having an approximately equal span. Along each individual fabric tube, welds  16  secure the fabric tube to itself to form the pockets  14 . As shown in FIG. 2, both welds  8 A and  16  are spaced apart from a center plane of a spring assembly. Welds  8 A and  16  are formed such that they are less than the height of spring  10  when expanded within pocket  14 . This configuration is sufficient to provide an adequate connection between adjacent pockets to maintain the spring orientation in the pockets sufficiently to prevent innerspring interference, without prejudicing the independent compressibility of the springs which is a feature of pocket spring mattresses. 
     Another important feature of spring assembly  2  is that each fabric tube is formed from a separate web of material. In this way, mechanisms for securing adjacent tubes together may be disposed within each assembly  70  to allow quilt  24  to be formed in situ, i.e., directly on assembly  70 . Another advantage of spring assembly  2  is that it is configured so that there is little independent motion of the vertical axis of pockets in adjacent rows. In this way, the springs are supported so that essentially no interference exists between coils of adjacent springs, which may cause undesirable noise as a user moves on a mattress or cushion incorporating the spring assembly. This advantage is obtained by providing fasteners  8 A and  16  which are spaced apart from the central horizontal plane of the spring assembly, at approximately the same relative location. Although shown with spaced apart welds, it will be appreciated that welds  8 A and  16  may be formed at different locations and have different lengths. For example, weld  16  may be formed the entire height of the fabric tube. It is, however, preferred that the vertical spans of the welds  8 A and  16  are similar so as to provide substantially symmetrical connections between the pockets in both the longitudinal and lateral directions. Moreover, it will be appreciated that connections  8 A and  16  may be formed using other connection schemes for which the apparatus can be accommodated within assemblies  70 , such as clips, glue, staples, one or two part fasteners, and the like. 
     Since the length of the spring assembly that is produced when the quilt is formed in situ is limited only by the length of fabric on the rolls from which webs  102  are fed, a mechanism is preferably provided to cut the quilt once an assembly of sufficient length has been formed. This may be accomplished, for example, by running a pass of the apparatus with the spring feed disabled to produce a row of empty pockets through which the cut may be made. 
     Once the spring assembly has been formed, it may be incorporated into a mattress, cushion, or other type of furniture. To construct a mattress, one or more layers of padding are placed adjacent to one or both sides of the spring assembly. A fabric cover is then secured about the assembly. 
     FIGS. 3-15 illustrate a particularly preferable embodiment of the invention, incorporating many of the same principles as described with reference to FIGS. 1A,  1 B,  1 C and  2 . One particularly advantageous feature of the embodiment of FIGS. 3-15 is that it provides the ability to form the quilt in situ as previously described. 
     A general layout of an apparatus  200  for forming spring assemblies is shown in FIG.  3 . Apparatus  200  is associated with a table  202  for receiving each assembly as it is formed. Springs are fed to apparatus  200  by a conveyor  204  which receives them from spring making and tempering machines  206 . Associated with machines  206  are wire feeds  208  and control units  210  as is known in the art. Springs on conveyor  204  which were heat treated in spring making machine  206  pass an optional cooling fan  214  before reaching apparatus  200 . Webs of material for forming fabric tubes of a quilt in apparatus  200  are drawn from rolls  216 . Each web of material is folded in half and turned 90 degrees by a folding assembly  218  before being passed as multiple folded superposed webs  220  (see FIG. 5) to apparatus  200 , in a direction parallel to that of conveyor  204 , as best shown in FIG.  5 . Apparatus  200  is shown divided generally into functional zones; namely a spring feed zone  300 , a tube forming and cross-welding zone  400 , and a pulling and spring pocketing zone  500 . 
     Referring now to FIG. 4, an upper run of spring conveyor  204  is shown. Conveyor  204  is disposed below spring feed zone  300 . A transverse cross member  402  is employed to support other elements (which are shown in FIG. 5) of tube-forming and cross welding zone  400 . Individual coil springs  302  have bottom turns received in shoes  304  attached to conveyor  204 . Springs  302  are loaded and removed from conveyor  204  by moving their bottom turns perpendicular to the direction of movement of conveyor  204 . Conveyor  204  moves a row of springs into spring feed zone  300 , alongside a row of vertical semi-cylindrical spring receivers  306 . For convenience of illustration, only one end of this row is shown in FIG.  3 . In practice, the number of receivers will be equal to the maximum number of columns of springs required in a spring assembly. For mattress spring assemblies, this number is typically at least 32 and preferably 40, depending on the spring size to be used, and assuming that the columns run transversely of the length of the mattress. It should be appreciated that many elements of the apparatus to be described will be duplicated identically for each column of springs in the assembly, and in all such cases only a single element or a few elements will be illustrated. 
     Opposite receivers  306  is a transverse member  310  supporting a corresponding row of semi-cylindrical spring pushers  308  (see also FIGS.  4 A and  4 B), which move with member  310  during a row cycle in a path illustrated by an arrow  311 . By “row cycle” is meant a cycle of operations of apparatus  200  to produce a row of springs in the spring assembly, i.e. one spring in each column. An initial arcuate forward movement of the pushers  308  by an actuator  320  moves a row of springs  302  out of shoes  304  and into receivers  306  as shown in FIG.  4 C. Pushers  308  cooperate with receivers  306  to form vertical tubes as shown in FIG.  4 D. Springs  302  in the tubes are then compressed by plungers  312  to the condition shown in FIG.  4 D. Plungers  312  are moved downward by an actuating bar  314  driven by a actuator  316 . Subsequently, member  310  and pushers  308  are lifted by actuator  318 . Member  310  and pushers  308  are then moved rearwardly and downwardly to their original position by actuator  320  and actuator  318 . In this manner, pushers  308  are clear from another set of springs advanced by conveyor  204 . 
     Referring also now to FIGS. 4D-4I, springs  302  compressed by the plungers  312  are in line with open ends of horizontal forward extending transfer tubes  404 , the rear ends of which pass through and are secured in cross member  402  (see FIGS.  4 D and  4 E). Also in line with tubes  404  are push rods  322  which pass through a transverse guide member  324  and are connected to a transverse push bar  326  driven by actuators  328  (see FIG.  4 ). Push rods  322  are tubular and contain secondary push rods  330  actuated by an actuator (not shown) operating between a secondary push bar (not shown) connected to rods  322  and push bar  326 . At the forward ends of push rods  322  are upper and lower plates forming duckbills  332  which are adapted to receive springs  302  as push rods  322  are moved forward beneath plungers  312 , as shown in FIGS. 4F and 4G. When duckbills  332  reach the limit of their travel at forward ends of tubes  404  as shown in FIGS. 4H and 4I, secondary push rods  330  are extended to eject springs  302  from duckbills  332 , as discussed further below. 
     FIG. 5 is a fragmentary view of tube forming and cross-welding zone  400  of apparatus  200 . In zone  400 , a quilt is formed into which springs  302  are to be inserted. Tube forming assemblies  406 , of which only a few are shown, are mounted on cross-member  402  concentric with spring transfer tubes  404 . Assemblies  406  are arranged to receive folded webs  220  of fabric from a fabric puller assembly  407  which comprises brake mechanisms  408  and  410  disposed above a roller box  412 . Roller box  412  is arranged to turn webs  220  so that one web  220  is provided to each assembly  406 . 
     The operation of brake mechanisms  408  and  410  of fabric puller assembly  407  is best shown in FIGS. 6A and 6B. The purpose of the assembly  407  is to draw measured lengths of fabric from rolls  216 , equal to the lengths of fabric drawn forward over the forming assemblies  406  by a pulling assembly in zone  500 , as described later. Each mechanism  408  and  410  is provided with a top plate  414  having slots to pass the folded fabric webs and a slotted brake plate  416 , movable laterally to clamp the webs between the slots of the two plates by an actuator  418 . The fabric is normally clamped by actuator  418  of top mechanism  408  as shown in FIG.  6 A. However, during a pulling operation, actuator  418  of top mechanism  408  is released and that of mechanism  410  is engaged as shown in FIG. 6B. A motor  422  drives lead screws  421  through belts  423  so as to raise mechanism  410  and pull the fabric. An exemplary motor that may be used is a servomotor, commercially available from Omron. After completion of the pulling stroke, the brake of mechanism  410  is disengaged and that of mechanism  408  is engaged so that motor  422  may return mechanism  410  to its original position ready for another pulling operation. 
     Above mechanism  408 , webs  220  (with the opening of their folds facing towards the front) pass upwardly around each assembly  406  and are tuck-folded through 90 degrees around each assembly  406  so as to be directed forwardly with the fold openings directed upwardly (see also FIGS.  8  and  9 ). Each assembly  406  comprises a lower guide plate  424 , which splits the fold of the fabric, and beneath which is mounted a guide rod assembly  426  whose rods guide the fabric over the outer portions of plate  424 . Folding guides  428  guide the free edges of the fabric onto an upper folding plate  430 , with the free edges projecting upwardly, while the rear portion of the fabric is tuck folded forward over plate  434  and passes between plates  424  and  434 . Guides  428  are supported from cross member  402 , as are folding plates  430  and  434 , guide plates  424  and tube  404 . 
     Referring now to FIGS. 8 and 9, operation of a fabric alignment scheme will be described. In order to counter any tendency of the fabric to track incorrectly through the folding assemblies, an optical sensor  470  is located on each side of a fin projecting upwardly from folding guide  430  between the edges of the fabric just forward of guides  428 . If the fabric moves out of alignment, one of its edges will move down and uncover the fin so that the misalignment will be detected by the sensor on that side. In response, the sensor will activate an actuator  472  on that side to press a skewed guide wheel  474  against the fabric. Guide wheel  474  is angled to pinch the fabric against guide  430  and steer it back on course until the fin is again covered, at which point the actuator is released. 
     Referring back to FIG. 5, four actuating bars  440 ,  442 ,  444  (see FIG. 10A) and  446 , operated by actuators  452  and  456 , extend laterally of the row of assemblies  406 , each being movable by its actuator through a short lateral stroke. Structures  454  and/or  468  supporting the actuating bars and associated parts may be mounted for limited forward and rear movement together with the parts they support, as described further below. Bars  440  and  442 , as best shown in FIGS. 7A-7C, actuate scissor arms  448  pivoted on fixed lateral bars  438  so as to clamp free edges of the fabric between thermal welding elements  460  and anvils  462 . In this way, webs  220  are formed into fabric tubes into which springs  302  will be inserted as described hereinafter. 
     Referring also to FIGS. 10 and 10A, bars  444  and  446  operate rocker levers  458  which are pivoted to tubes  404  at pivot points  463  to move welding elements  466  against anvil plates  436  of adjacent tubes  404 . It will be noted that in FIGS. 7A and 7B that the outermost welding elements  466  in the furthest left and furthest right assembly  406  are omitted since they are not needed. As shown in FIGS. 10A-10C, springs  461  are disposed between bars  446  and levers  458 . When bars  444  and  446  are moved, levers  458  are pivoted about pivot points  463  to move welding elements  466  against anvil plates  436  (see FIG. 10C) under a pressure determined by springs  461 . In this manner, adjacent fabric tubes on adjacent assemblies  406  may be welded together to form a two-dimensional array of pockets for receiving springs, e.g., forming welds  8 A as shown in FIG.  2 . In this way, a fabric quilt  464  (see FIG. 12) within which the pockets are included may be constructed in situ rather than pre-fabricating individual strings of spring assemblies. 
     FIGS. 10D and 10E are fragmentary views of one assembly  406  illustrating the ejection of spring  302 . As previously described in connection with FIGS. 4H and 4I, duckbills  332  force spring  302  out of tube  404 . FIG. 10D illustrates spring  302  as it begins to exit tube  404 , and FIG. 10E illustrates spring  302  when fully expanded. In operation, spring  302  is ejected into one of the fabric tubes formed from web  220  after a transverse weld has been created in the fabric tube as described hereinafter. 
     FIG. 11 is a view of one end of pulling and spring pocketing zone  500 . Zone  500  comprises a chassis  502  which is normally located just in front of zone  400 , but can be moved forwards on slide bars  504  to permit access to zone  400 . Zone  500  further comprises a spring pocketing assembly  508  and a quilt puller assembly  510 . As shown in FIGS. 11A and 11B lead screws  506  are employed to move puller assembly  510  forward and rearward. A drive motor  507  having a toothed belt drive  509  is operated to turn belts  511  which cause lead screws  506  to rotate. Depending on the direction of rotation of motor  507 , quilt puller assembly  510  is moved forward or rearward. An exemplary motor that may be used is a servomotor, commercially available from Omron. 
     Referring to FIG. 12, quilt puller assembly  510  comprises actuators  512  which raise and lower a cross member  514  carrying puller elements  516  which are moved upwardly by actuators  512  into slots occurring between successive welds  8 A formed by welding elements  466 . In this way, when lead screws  506  are rotated, puller elements  516  are moved forward (as shown in phantom line) to engage welds  8 A and thereby pull a formed mattress assembly forward onto table  202  (see FIG.  3 ). At the same time, puller elements  516  pull forward a quilt  464  (of connected fabric tubes) formed on assemblies  406 , and pull up folded fabric webs  220  fed by assembly  410  (see FIG.  6 ). After moving forward, elements  516  are retracted downwardly, and puller assembly  510  is moved to its starting position. 
     Quilt puller assembly  410  may also be connected to structures  454  and/or  468  (see FIG. 5) so that, during a pulling operation, welding elements  460  and/or  466  may be maintained clamped against their associated anvils and travel with quilt  464  formed on forming assemblies  406 . This provides a more even pulling action and further relieves any stress on the welds. If welding elements  466  are movable, anvil plates  438  and levers  458  should be supported on structure connected to structure  468  rather than directly connected to tubes  404 . In like manner, spring pocketing assembly  408  may be connected to move with puller assembly  410  so as to further distribute the pulling forces and avoid stress on welds formed by pocketing assembly  508  as described below. Indeed, by pulling with the welding elements clamped against the anvils, it may be possible to dispense with the use of separate puller elements  516 . It will be understood that in arrangements in which the welding elements and anvils travel during the pulling stroke, the elements and anvils are not released after a welding operation until after the pulling stroke is completed. If these elements do not travel, they must be released prior to the pulling stroke. 
     Spring pocketing assembly  508  (see FIGS. 13,  13 A,  13 B,  14 A,  14 B and  15 ) which may be mounted on chassis  502 , to travel with the pulling assembly  510 , comprises actuators  520  which raise and lower a cross member  522 . Coupled to cross member  522  are laterally extending actuator bars  524  and  526  which carry downwardly extending fingers  528  and  530 , respectively. Fingers  528  carry welding elements  532  and fingers  530  carry anvils  534  as best seen in FIGS. 14A and 14B. Bars  524  and  526  are actuated by actuators  536  and  538  to move elements  532  and anvils  534  between the positions shown in FIGS. 14A and 14B. In FIG. 14A, elements  532  and anvils  534  extend downwardly through slots between successive welds  8 A (see FIGS. 13A and 13B) between tubes in quilt  464  formed on assemblies  406 . In FIG. 13B, elements  532  and anvils  534  clamp the tubes in quilt  464  and form welds  16  (shown in phantom line in FIGS.  13 A and  13 B). Welds  16  may be either vertically spaced welds as shown in FIG. 2, or as single continuous welds extending through a horizontal center plane of quilt  464 . 
     Actuators  520  raise cross member  522  and connected elements  532  and anvils  534  clear of quilt  464  during return motion of carriage  502  (see FIG.  13 A). Welds  16  define pockets for successive springs that are discharged from the tubes  404  as best shown in FIGS. 13A and 13B. As shown in FIGS. 15 and 15A, cross member  522  also caries a cutting wire  540 , which may be activated to sever a spring assembly when it has reached a sufficient length (e.g., when it has sufficient rows of springs) and has been transferred to table  202 . The severance will typically be made after a cycle in which no springs are delivered from the conveyor, so as to produce an empty length of quilt through which the cut may be made. 
     Spring assembly forming apparatus  200  is preferably operated using one or more controllers which control the various actuators, lead screw motors, heating elements, and other movable parts. Preferably, the controller is programmed so that apparatus  200  operates in cycles where rows of springs are inserted into the quilt as the quilt is being formed on assemblies  406 . In this way, a two-dimensional spring assembly is formed in situ. Exemplary controllers which may be employed to control the various operations of apparatus  200  are PLC controllers, such as Mitsubishi FX series controllers, commercially available from Mitsubishi, and having a Quick Panel touch screen available from TCP. 
     In operation, fabric webs  220  are initially loaded onto assemblies  406 . A first row of springs are also loaded into tubes  404  utilizing the equipment in spring feed zone  300  as described in connection with FIGS. 4A-4I. Bars  440  and  442  are moved to clamp the free ends of webs  220  between welding elements  460  and anvils  462  as shown in FIG.  7 B. Thermal welds are then produced to form webs  220  into fabric tubes which are disposed about assemblies  406 . At the same time, cross bar  522  is lowered and elements  532  and anvils  534  are closed around webs  220  as shown in FIG.  14 B. In this way, a transverse weld  16  is produced in each fabric tube to form one end of a pocket. While this transverse weld is being produced, welding elements  466  are moved against anvils  436  as shown in FIG. 7B to produce cross welds  8 A between adjacent fabric tubes. In this manner, quilt  464  (see FIG. 12) is produced in situ on assemblies  406 . Once the welds have set, all welding elements are released, and pulling assembly  510  is employed to pull quilt  464  forward over assemblies as shown in FIG.  12 . Alternatively, the welding elements themselves may be employed to pull quilt  464  forward as previously described. 
     At this point, a row of springs  302  are ejected out of tubes  404  (see FIGS. 10D and 10E) into the row of half formed pockets in quilt  464 . At this point, one full cycle has been completed. This cycle is repeated as many times as desired depending on the desired length of the spring assembly. More specifically, cross bar  522  is again lowered and elements  532  and anvils  534  are closed about each fabric tube to form a transverse weld  16  behind each spring to enclose the spring in a pocket. Also formed are the longitudinal welds, the cross welds, and another row of springs are introduced into tubes  404 . The springs are ejected into a second row of pockets after quilt  464  has been advanced over assemblies  406 . Once a desired length has been reached, cutting wire  540  is lowered to sever the completed spring assembly from the quilt remaining on assemblies  406  as shown in FIG.  15 . 
     The various welding elements are preferably electrically heated wires. Such wires are preferred because of their relatively small cost and size. Thermal welds are also advantageous because, if the welds are formed well before the quilt is pulled, ample time is available for the welds to set before they are subjected to any stress. If the welding elements and anvils remain clamped during the pulling stroke, the welds have still further opportunity to set before being exposed to stress. 
     Welds  8 A and  16  are sufficiently vertically spaced such that their upper and lower extremities are well above and below a center line of the mattress assembly and of the quilt from which it is formed. This provides symmetrical support for the springs and inhibits possible interference between the springs due to inadequate lateral support. In order to provide the most effective welding, without undue weakening of the fabric, it is preferred to utilize a composite non-woven fabric formed of fibers of two different synthetic plastic resins, which will bond together, but one of which fuses at a considerably higher temperature than the other. For example, such synthetic plastic resins can include polyethylene, polypropylene, polyester, and the like. Alternatively, the fibers themselves may be composite, with a lower fusing outer layer which bonds the fibers and a higher fusing core. Such materials can include, for example, polyethylene and polyester (with either material being either on the outside or inside). The welding elements are energized so as to fuse only the lower melting component or layer. 
     One important advantage of the invention is that springs which are constructed from tempered steel may be used. The use of tempered coils is advantageous in that tempered coils make the spring unit more resilient and provide a much longer life to the spring unit. Also, tempering allows the manufacturer to use less wire while achieving a better coil. Further, tempering provides cost savings because lower tensile wire may be used. When non-tempered wire is used, the manufacturer is generally required to include more turns of wire in a coil. As such, the coil must be inserted under pressure into the pocket so that the coil will hold its original height. 
     The invention has now been described in detail for purposes of clarity of understanding. However, it will be appreciated that certain changes and modifications may be practiced within the scope of the appended claims.