METHOD AND SYSTEM FOR FORMING SERIES OF SPIRAL ENCAPSULATED SPRINGS
BACKGROUND OF THE INVENTION
This invention relates generally to springs assemblies for mattresses, cushions and the like, and in particular, to a method and system for making a series of individually connected spiral springs for mattresses, cushions, spring units and the like. Encapsulated coil springs are often referred to as a Marshall construction in which the coiled spring is enclosed within its own capsule or fabric sack. Normally, the bag or capsule is defined between two folds of a strip of fabric connected at intervals along transverse lines spaced along the strip. The two-fold fabric strip is generally formed by folding a strip of double-width fabric over itself along a longitudinal center line, leaving the pleats superimposed along the opposite unbonded edges of the strip that will be connected each other along a longitudinal seam to close the capsules defined between the connecting transverse lines after the springs are inserted between the folds. A variety of techniques have been developed for the manufacture of encapsulated springs, some contemplate the creation of the capsules within the folds of fabric before the insertion of the wire spring and others contemplate the insertion of springs of compressed wire between the folds of the wire. the strip and the subsequent creation of the capsules when sewing or otherwise, joining the two folds together along transverse lines between adjacent springs. Regardless of the technique used, the fabric is closed around the spring after the insertion of the spring, normally when sewing or welding the two folds together along a line parallel to the free edges of the folds. The joining of folds by sewing has been replaced in more recent times by the use of a heat-sensitive fabric and ultrasonic welding techniques. Examples of known techniques and systems for making series of encapsulated coil springs are described in the U.S. Patents. Nos. 4,439,977; 4,234,983; and 5,613,287. Specifically, in the patent of E.U.A. No. 4,439,977, there is disclosed a method and apparatus for making coil springs enclosed within individual capsules in an extended fabric strip comprised of two shell folds capable of being thermally welded. The fabric strip is fed along a guide path during which the compressed springs are inserted between the folds with the axes of the springs substantially normal or perpendicular to the planes of the folds. Accordingly, the fabric folds are thermally welded longitudinally and transversely, while the spring remains compressed to form a series of encapsulated spirals. After thermal welding, the encapsulated coils are passed through a turner assembly during which the springs are normally reoriented by approximately 90 ° inside the cloth caps to positions where the axes of the springs are transverse to the strip cloth. A specific disadvantage of this method of manufacturing encapsulated coil springs is that during the turning process, the springs tend to become entangled or snagged and do not get their proper positions. As such, it requires additional and expensive work to reorient and unravel the springs to place them in their desired configurations and orientations. Even if the springs do not become entangled or hooked, difficulties may arise to correctly align them to their desired positions with the longitudinal axes of the springs being substantially parallel to each other and the transverse seams defining individual capsules. Another common problem with this type of operation is that during the operation of turning the encapsulated springs, whether the springs snag or entangle and the turning procedure is successful, the fabric around the spring is often damaged, torn, punctured, etc. In one form, the springs are beaten by pallets as described in the U.S. patent. No. 4,439,977 to perform the operation of turning the spring inside the capsule. Obviously, the repeated beating in the capsule with the paddles can cause significant damage to the fabric material and it may not be reliable to accurately place the spring inside the cloth capsule. When this happens, the damaged capsule must be repaired or removed from the series thus interrupting the procedure and requiring significant operator intervention and suspension time for the production of encapsulated spiral springs. Therefore, there is a need for a method and system for forming series of encapsulated spiral springs, which overcome the aforementioned disadvantages of the prior art and do not require the operation of turning the springs inside the capsules for alignment of the springs. spring shafts in a generally parallel and orderly arrangement, no operator intervention to disengage or untangle the springs or repair the damaged fabric surrounding the springs. In addition, there has always been a need to provide commercially feasible methods and systems to produce series of encapsulated coil springs that are cost and labor efficient by requiring a minimum amount of labor intervention and associated resources. WO 98/11015 describes a method for forming encapsulated springs in which cloth is formed in a sheath and the compressed springs are inserted into the sheath. The fin is then bent and joined with a longitudinal seam. Individual capsules are created with transverse seams and the springs are rotated inside their capsules to make their longitudinal axes parallel to the transverse seams.
BRIEF DESCRIPTION OF THE INVENTION
The present invention overcomes these and other disadvantages of the prior art by providing an improved method and system for producing series of encapsulated coil springs which are effective in performance, and even cost effective, since they require a minimum amount of materials and work. The manner in which the springs are inserted into the fabric and the formation of the capsule according to this invention, avoids the need for operation of turning or repositioning of the springs within the capsules while providing an efficient and reliable manufacturing system. and an associated method to reliably produce springs aligned in a consistent manner within undamaged cloth capsules. Preferably, the present invention begins with the insertion of a compressed spiral spring between upper and lower folds of a thermally welded bent fabric. The present invention is a continuous production process, so that the fabric is adjusted or pulled beyond a spring insertion station so that the compressed springs are individually inserted between the folds of the folded fabric at spaced intervals according to the fabric passes the spring insertion station. The springs are held in a compressed configuration between the folds of the fabric, while a longitudinal seam is formed in the fabric to join the two folds close to the free edges of the folds opposite a longitudinal fold line of the fabric. Since the fabric is a material that can be thermally welded, the longitudinal seam is preferably formed by a cooperative combination of anvil and thermal welding head. After the spring has advanced past the longitudinal welding station, it is allowed to relax and expand within the fabric in a vertical position in which a longitudinal axis of the spring is generally perpendicular to the longitudinal seam of the fabric. Preferably, the relaxation and expansion of the springs within the fabric is controlled by a pair of rotating elements on opposite sides of the springs according to different alternative embodiments of this invention. The rotating elements in presently preferred embodiments can be a pair of rotating wheels in the opposite direction with axes of rotation generally parallel to the longitudinal axes of the springs. The wheels include a plurality of arc-shaped recesses which combine to partially surround each spring during expansion. Alternatively, the rotating elements may include a pair of bands each passing over a pair of spaced rollers. The fabric and spring pass between the bands and a distance of separation between the bands increases in a downward direction to thereby control the expansion of the springs between the bands. In any mode, the springs are supported during their expansion in a vertical position. After the springs have expanded within the fabric, individual capsules are preferably formed by a transverse welding head which seals the fabric between each of the springs generally parallel to the axes of the spring. Transverse seams are formed in the fabric to complete the individual capsules for the individual springs. Finally, a pair of rotary conveying wheels in the opposite direction adjusts or moves the series of springs encapsulated forward thus advancing the fabric and the springs enclosed through the different stations as described above. Advantageously, the orientation of the springs remains generally unchanged throughout the encapsulation process, so that the reorientation, turning or the like of the springs within the capsules is avoided. Moreover, the longitudinal seam formed in the fabric is placed on a side face of the individual spring capsules in the resulting series of encapsulated spiral springs., thus avoiding the problem known in the art as "false attic". The false loft occurs when the longitudinally extending seams keep the roofing material at a certain distance away from the ends of the springs, so that when the mattress is first purchased, this distance is slightly uniform. However, after the mattress or cushion has been in use for a while, the longitudinally extending seams or other excess fabric in the encapsulated spiral spring can be compressed thereby leaving areas or regions of depression. With the continuous use of the mattress or cushion, the entire mattress or cushion support surface will be compressed in a similar manner and will look substantially flat. A user may not understand the origin of this phenomenon and consider it as a defect in the mattress or cushion. The false loft problem is thus avoided in the present invention, by placing the longitudinal seam of the series of springs on one side thereof while avoiding the need to rotate or reorient the individual springs within the capsules and the damage resulting to the fabric and other associated problems. Another feature of this invention, which also helps in the reduction of false attic and related problems, is particularly useful for barrel-shaped springs or other springs, which have a non-linear profile. With said springs, the transverse seam between adjacent springs in the series is configured to fit the profile of the springs and in this way, produce a more tight and tight fabric capsule around the spring to avoid bunching or loose excess fabric around the spring .
BRIEF DESCRIPTION OF THE DRAWINGS
The objects and features of the invention will be more readily apparent from the following detailed description taken in conjunction with the accompanying drawings in which: Figure 1 is a top horizontal projection of a schematic representation of an associated system and method in accordance with a first embodiment for producing a series of encapsulated spiral springs of this invention; Figure 2 is a side elevational view of the system and method of Figure 1; Figure 3 is a view similar to Figure 1 of a second currently preferred system and associated method in accordance with this invention; Figure 4 is a side elevational view of the system and method of Figure 3; Figure 5 is a perspective view of a series of encapsulated spiral springs produced in accordance with this invention; Figure 6 is a cross-sectional view of a single spiral spring enclosed within a cloth capsule taken along line 6-6 of Figure 5; Figure 7 is a side elevational view of a series of encapsulated spiral springs produced in accordance with an alternative embodiment of this invention; and Figure 8 is a partial perspective view of a welding head used to weld a transverse seam in the series of Figure 7.
DETAILED DESCRIPTION OF THE INVENTION
Referring to Figure 1, a first currently preferred embodiment of a system 10 and associated method is shown for forming a series 12 of encapsulated spiral springs 14 in accordance with this invention. The fabric 16, preferably thermally weldable as is known in the art, is fed from a supply roll 18 around a roll 20 as shown in Figure 1. Alternatively, the cloth 16 may be cotton or other suitable material. The fabric 16 is generally folded in half longitudinally about a longitudinal fold line 22 which coincides approximately with a longitudinal centerline of the fabric 16. The fabric 16 is folded over the longitudinal fold line 22 to produce a first upper fold 24 and a second lower fold 26 of the cloth 16 each with a free edge 28 spaced from the longitudinal fold line 22. The folded fabric 16 passes the upper and lower entry rollers 30, 32 before entering a station of insertion of spring 34. Rollers 20, 30 and / or 32 can be driven in a rotatable manner. The spring insertion station 34 includes an alternating insertion plunger 36 having a cup-shaped spring that receives a forward end 38 for receiving a compressed spiral spring 14. The plunger 36 extends to insert the compressed spring 14 between the folds 24, 26 and contracts to receive another compressed spring 14 for subsequent insertion. The spring 14 is formed and compressed and loaded into the spring insertion plunger 36 and the fabric 16 is folded according to any of the methods and systems known for this purpose. Alternatively, the spring insertion station 34 may comprise two U-shaped profiles which hold the spring 14 compressed and lead the springs 14 into the bent fabric 16. In this method, the spring 14 is supported with a hairpin (not shown) while the profiles return. As the fabric 16 advances through the system 10, the springs 14 inserted between the folds 24, 26 are maintained in a compressed configuration between upper and lower support plates 40, 42 on the upper and lower faces, respectively, of the fabric 16. as shown particularly in Figures 1 and 2. Preferably, the support plates 40, 42 are centered between the free edges 28 and longitudinal fold line 22 of the fabric 16 and can include a wider region 44 near the station of insertion of spring 34 which tapers in a downward direction toward a smaller separation region 46 between plates 40, 42 as the fabric 16 and springs 14 advance through rear portions of the system 10. In addition, a plurality of spaced alignment wheels 48, which are mounted for rotation near the longitudinal fold line 22 and free ends 28 of the 16, control and direct the movement of the fabric 16 through the system 10. Preferably, the alignment wheels include a plurality of projections 50 which engage the fabric 16 to maintain movement of the fabric 16 in an orientation aligned with respect to the different stations and components of the system 10. A longitudinal sewing forming station 52 is located downstream of the spring insertion station 34 near the free ends 28 of the fabric 16, as shown in the figures 1 and 2. After the compressed springs 14 are inserted between the folds 24, 26, the longitudinal seam forming station 52 joins the upper folds. bottoms and bottoms 24, 26 of the fabric 16 close to their respective free edges 28, thus initially enclosing the springs 14 within the fabric 16. In a presently preferred embodiment, a longitudinal seam 54 is formed between a heat sealing head 56, which alternates downwards and upwards to cooperate in welding coupling and uncoupling, respectively, in relation to an anvil 58 positioned from under the lower fold 26. The alternating welding head 56 and anvil 54 cooperate to form the longitudinal seam 54 in the fabric 16 by welding the respective folds 24, 26, ultrasonically, thermally or the like as is known to those skilled in the art. Alternatively, the anvil 58 moves reciprocally while the thermal welding head 56 remains fixed. The springs 14 remain compressed during the formation of the longitudinal seam 54 and welded with their longitudinal axes 60 generally perpendicular to the longitudinal seam 54. Signal! that other means are suitable for joining the folds 24, 26 to form the seams such as sewing, stapling, or other means within the scope of the present invention. A first transportation station 62 is located downstream of the longitudinal sewing forming station 52 and, in a presently preferred embodiment, includes four transportation bands 64. Each band 64 passes over front and drive spaced apart rolls 66, 68, by at least one of which is rotationally actuated. A first pair of bands 64a in the first transportation station 62 makes contact with the fabric 16 close to the longitudinal fold line 22 passing therebetween. Another pair 64b of conveyor belts 64 makes contact with the fabric 16 near the longitudinal seam 54 as shown in FIGS. 1 and 2. As the belts 64 pass around the spaced rollers 66, 68 in contact with the fabric 16, the fabric 16 is withdrawn from the supply cylinder 18 through the upstream stations and advanced to a downstream spring expansion station 70. The compressed springs 14 are allowed to relax and expand within the fabric 16 at the expansion station of spring 70. In a first embodiment, the expansion of the springs 14 is controlled by a pair of contrarily rotating rotational elements 72 on opposite sides of the springs 14 as shown in figure 1. A rotation axis 74 of each of the rotational elements 72 according to the first currently preferred embodiment of Figure 1, is generally parallel to the longitudinal axes 60 of the springs 14. Each rotational element 72 includes a plurality of arcuate shaped recesses 76, each of which is combined with a similarly configured recess 76 in the corresponding rotation member 72 on the opposite side of the spring 14 to partially surround each spring 14 and thus, control the expansion of it. further, the rotational elements 72 assist in advancing the springs 14 and fabric 16 towards a transverse seam forming station 78 located downstream thereof. The cross seam forming station 78 forms a transverse seam 80 in the fabric 16 between each of the adjacent springs 14 which have expanded within the fabric 16 from its compressed configuration. Preferably, the cross seam forming station 78 includes a cross seam weld head 82 and a cooperative cross seam anvil 84 located on opposite sides of the forming series 12 of spiral springs 14 encapsulated with each other. As the springs 14 advance toward and through the cross seam forming station 78, the fabric 16 between the springs 14 is joined, thus completing the individual capsules 86 for each of the springs 14 and enclosing the springs 14 within the fabric. 16. Again, it should be appreciated that other means may be used to form the cross seam 80, such as stitching, stapling or the like within the scope of this invention. While the cross seam 80 is formed, the fabric 16 is sewn or joined. As such, the series 12 of encapsulated coil springs 14 must yield or contract a little to accommodate the seam forming process. This can be done with an active mechanism, such as a powered or passive transport system such as friction between the fabric 16 and the rotational transport elements 62. The longitudinal axes 60 of the springs 14 generally remain parallel to the seams transverse 80 in the fabric 16. However, due to the expansion of the springs 14, the longitudinal seam 54 formed in the free ends 28 of the fabric 16 is generally placed on a side face 88 of the series 12 of encapsulated coil springs 14 between upper and lower ends 90, 92 of the encapsulated spiral spring 14, as shown particularly in Figures 5 and 6. With the longitudinal axes 60 of the springs 14 generally aligned and parallel to each other within individual cloth capsules 86, the present invention avoids the need to rotate springs 14 within fabric capsules 86 as required in many systems of the previous technique. Referring to Figures 5 and 6, the longitudinal seam 54, preferably joins the capsules 86 when the transverse seam 80 is formed by the cross seam forming station 78. As such, in the region of the next fabric 16 to the cross seam 80, four layers of fabric 16 are welded in the cross seam forming station 78. It should be noted that there are other methods for securing the seam 80 in this way, for example, the longitudinal seam 54 can be placed before entering the cross seam station 78 even if it is not welded to the capsule 86 with the transverse seam 80. In addition, the longitudinal seam 54 may be located anywhere between the upper and lower part of the series, although in the drawings shows approximately half of it. Preferably, a second transport station or downstream station 94 includes a pair of transport wheels that rotate in opposite fashion 96 each with a rotation axis 98 generally parallel to the longitudinal axes 60 of the springs 14. A plurality of arcuate recesses 100 at the periphery of the transport wheels 96 cooperates to at least partially surround the encapsulated springs 14 and advance them from the upstream transverse seam forming station 78 for unloading and packing, storing or further processing in a mattress, cushion or unit of internal spring. An alternative embodiment of this invention is shown in Figures 3 and 4 and the components of the system 10 of Figures 3 and 4 which are similar to those of the first embodiment shown in Figures 1 and 2, are identified by identical reference numbers and the detailed description above with respect to those elements provided above, is applied similarly to the embodiment of Figures 3 and 4. The second currently preferred mode shown in Figures 3 and 4, includes Divergent transportation bands 102 located above and below the fabric 16 and enclosed springs 14 in the spring expansion station 70. The transportation mechanism can be modalized with wheels as in figures 1 and 2 and / or transportation bands as in figures 3 and 4 which are located at the top and bottom of the series or on the side surfaces as desired. Each of the conveyor belts of Figures 3 and 4 pass over front and drive rollers 104, 106, as shown particularly in Figure 4. Further, a separation distance between the conveyor belts 102 is increased in one direction This allows the controlled expansion of the springs 14 placed on the fabric 16 between the conveyor belts 102. The relaxed and expanded springs 14 advance towards the downstream transverse seam forming station 78, so that the transverse seam 80 can be co-operating between the adjacent springs 14 to complete the individual cloth capsules 86. A further feature of this invention is shown in Figures 7 and 8 and is particularly adapted for use in construction of series 12 of encapsulated coil springs 14a having a configuration barrel shaped as shown in figure 7. The barrel-shaped springs 14a are with They include in the industry and include a profile 108 in which the middle turns 110 of the spring 14a have a diameter greater than the top turn 112 and bottom turn 114 of the spring 14a. For example, the upper and lower turns 112, 114 of the barrel-shaped spring 14a can have a diameter of about 4.1275 cm and the mean turn 110 has a diameter of about 6.35 cm. When barrel-shaped springs 14a are used in the series 12, the transverse seam 80a adjacent to the spring 14a fits the profile 108 of the spring 14a as shown in Fig. 7. With the cross seam 80a fitting to the profile 108 of the spring 14a enclosed in the capsule, a more hermetic capsule with less loose cloth 16 is produced in the series 12 and a better overall product, especially with springs 14a having a non-linear profile. With barrel-shaped springs 14a, the transverse seam 80a adjacent thereto has a concave shape and because the transverse seam 80a is located between adjacent swept springs 14a, the seam 80a may have a pair of concave shapes that they are facing outwards that form an X or similar configuration. A welding head 82a suitable for forming the transverse seam 80a is shown in Figure 8, in which a number of bolts 116 are arranged in the pattern shown so that the adjacent bolts 116 near the top and bottom of the head 82a, are spaced apart from those in the middle to conform with the profiles 108 of the adjacent barrel-shaped springs 14a. Although the transverse seam 80a of Figure 7 is symmetrical, other configurations are contemplated within the scope of this invention. In addition, in another sense, this feature of the invention is useful not only for barrel-shaped springs 14a to form a more tight cloth capsule, but also for springs having a non-linear profile, in general such as springs in the form barrel and hourglass-shaped springs in which the middle turns have a smaller diameter than the upper and lower turns. From the above description of the general principles of the present invention and the above detailed description of at least one preferred embodiment, those skilled in the art will readily understand the various modifications to which this invention is susceptible.