WO2000063113A1 - Method and system for forming strings of pocketed coil springs - Google Patents

Abstract

A string (12) of pocketed coil springs (14) is formed by inserting compressed springs between upper and lower plies of a folded, preferably thermally weldable fabric (16). The springs are maintained in a compressed configuration while a longitudinal seam (54) joins the free edges of the thermally welded fabric (16) together. Subsequently, the compressed springs (14) are allowed to relax into an expanded configuration after which a transverse seam (80) is formed in the fabric (16) between the adjacent springs (14) thereby encapsulating each spring (14) within a fabric pocket (86). The string (12) of pocketed coil springs (14) is advantageously formed without the need for reorienting the springs (14) after being inserted between the plies (24, 26) of the fabric (16) and thereby avoiding the disadvantages and complications associated with turning or reorienting the pocketed coil spring (14).

Description

METHOD AND SYSTEM FOR FORMING STRINGS OF POCKETED COIL SPRINGS

This is a continuation-in-part of U.S. Patent Application

Serial No. 09/293,221 , filed April 1 6, 1 999 and hereby incorporated

by reference in its entirety.

Background of the Invention

This invention relates generally to spring assemblies for

mattresses, cushions and the like, and, more particularly, to a

method and system for making a string of connected individually

pocketed coil springs for mattresses, cushions, spring units and the

like.

Pocketed coil springs are often referred to as a Marshall

construction in which each coil spring is encased within its own fabric sack or pocket. The sack or pocket is typically defined

between two plies of a fabric strip connected together at intervals

along transverse lines spaced along the strip. The two-ply fabric

strip is generally formed by folding a strip of double width fabric

upon itself along a longitudinal centerline, leaving the overlapped

plies along the unjoined opposite edges of the strip to be connected

to each other along a longitudinal seam to close the pockets defined

between the transverse lines of connection after the springs are

inserted between the plies.

A variety of techniques have evolved for the

manufacture of pocketed springs, some contemplating the creation of

the pockets within the fabric plies prior to insertion of the wire spring

and others contemplating the insertion of compressed wire springs

between the plies of the strip and the subsequent creation of the

pockets by stitching or otherwise joining the two plies to each other

along transverse lines between adjacent springs. Irrespective of the

technique used, the fabric is closed around the spring after the

insertion of the spring, usually by stitching or welding the two plies

together along a line parallel to the free edges of the plies. Joining

the plies together by stitching has largely been replaced in more

recent times by the use of a heat sensitive fabric and ultrasonic

welding techniques. Examples of known systems and techniques for

manufacturing strings of pocketed coil spring are disclosed in U.S. Patent Nos. 4,439,977; 4,234,983; and 5,61 3,287, each of which

are incorporated herein by reference.

Specifically, in U.S. Patent No. 4,439,977, a method

and apparatus are disclosed for making coil springs enclosed within

individual pockets in an elongate fabric strip comprised of two

overlying plies capable of being thermally welded together. The

fabric strip is fed along a guide path during which compressed

springs are inserted between the plies with the axes of the springs

substantially normal or perpendicular to the planes of the plies.

Thereafter, the fabric plies are thermally welded together

longitudinally and transversely while the spring remains compressed

to form a string of pocketed coils. After thermal welding, the

pocketed coils are passed through a turner assembly during which

the springs are reoriented typically about 90° within the fabric

pockets to positions wherein the axes of the springs are transverse

to the fabric strip.

One specific disadvantage of this method of

manufacturing pocketed coil springs is that during the turning

process, springs tend to become entangled or hooked together and

do not achieve their proper positions. As such, additional and costly

labor is required to reorient and disentangle the springs to place them

into their desired configurations and orientations. Even if the springs

do not become entangled or hooked, difficulties may still arise in correctly aligning them to their desired positions with the longitudinal

axes of the springs being substantially parallel to one another and the

transverse seams defining individual pockets.

Another common problem with this type of operation is

that during the turning of the pocketed springs, whether or not the

springs become hooked or entangled and the turning process is

successful, the fabric surroundjng the spring is often damaged, torn,

punctured or the like. In one form, the springs are beaten by paddles

as disclosed in U.S. Patent No. 4,439,977 to effect the turning of

the spring within the pocket. Obviously, the repeated beating on the

pocket with the paddles may cause significant damage to the fabric

material and prove to be unreliable to accurately position the spring

within the fabric pocket. When this happens, the damaged pocket

should be repaired or removed from the string thereby interrupting

the process and requiring significant operator intervention and down

time for the production of pocketed coil springs.

Therefore, a need exists for a method and system for

forming strings of pocketed coil springs which overcomes the above

described disadvantages of the prior art and does not require the

turning of the springs within the pockets for alignment of the spring

axes in a generally parallel and ordered arrangement nor operator

intervention to unhook or disentangle the springs nor repair the

damaged fabric surrounding the springs. Further, a need has always existed to provide commercially viable methods and systems for

producing strings of pocketed coil springs which are cost and labor

effective by requiring a minimal amount of labor intervention and

associated resources.

Summary of the Invention

The present invention overcomes the above described

and other disadvantages in the prior art by providing an improved

method and system for producing strings of pocketed coil springs

which are effective in performance, yet cost effective in that it

requires a minimum amount of materials and labor. The manner in

which the springs are inserted into the fabric and the formation of

the pocket according to this invention avoids the need for turning or

repositioning the springs within the pockets while still providing an

efficient and reliable manufacturing system and associated method

for reliably producing consistently aligned springs within undamaged

fabric pockets.

The present invention preferably begins with the

insertion of a compressed coil spring between upper and lower plies

of a folded thermally welded fabric. The present invention is a

continuous production process such that the fabric is indexed or

pulled past a spring insertion station so that the compressed springs

are individually inserted between the plies of the folded fabric at spaced intervals as the fabric passes the spring insertion station.

The springs are maintained in a compressed configuration between

the plies of the fabric while a longitudinal seam is formed in the

fabric to join the two plies together proximate free edges of the plies

opposite from a longitudinal fold line of the fabric. Since the fabric is

a thermally weldable material, preferably the longitudinal seam is

formed by a cooperating thermal weld head and anvil combination.

After the spring has advanced past the longitudinal weld station, it is

allowed to relax and expand within the fabric into an upright 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 members on opposite sides of the springs according to

various alternative embodiments of this invention. The rotating

members in presently preferred embodiments may be a pair of

oppositely rotating wheels with axes of rotation generally parallel to

the longitudinal axes of the springs. The wheels include a plurality of

arcuate-shaped recesses which combine to partially surround each

spring during the expansion. Alternatively, the rotating members

may include a pair of bands each passing over a pair of spaced

rollers. The fabric and springs pass between the bands and a

separation distance between the bands increases in a downstream

direction to thereby control the expansion of the springs between the bands. In either embodiment, the springs are supported during their

expansion into an upright position.

After the springs have expanded within the fabric,

individual pockets are formed preferably by a transverse weld head

sealing the fabric between each of the springs generally parallel to

the spring axes. The transverse seams are formed in the fabric to

complete the individual pockets for the individual springs. Finally, a

pair of opposing and rotating transport wheels indexes or moves the

string of pocketed springs forwardly thereby advancing the fabric and

enclosed springs through the various stations as described.

Advantageously, the orientation of the springs remains

generally unchanged throughout the pocketing process so that

reorientation, turning or the like of the springs within the pockets is

avoided. Moreover, the longitudinal seam formed in the fabric is

positioned on a side face of the individual spring pockets in the

resulting string of pocketed coil springs thereby avoiding the problem

known in the art known as "false loft". False loft occurs when the

longitudinally extending seams maintain the cover material at a

certain distance away from the ends of the springs so that when the

mattress is first purchased, this distance is fairly uniform. However,

after the mattress or cushion has been in use for a period of time,

the longitudinally extending seams or other excess fabric in the

pocketed coil string may become crushed thus leaving areas or regions of depression. With continued use of the mattress or

cushion, the entire support surface of the mattress or cushion will

similarly be crushed and will appear substantially flat. A user may

not realize the source of this phenomenon and consider it to be a

defect in the mattress or cushion.

The problem of false loft is thereby avoided in the

present invention by positioning the longitudinal seam of the string of

springs on a side thereof while still avoiding the need to turn or

reorient the individual springs within the pockets and the resulting

damage to the fabric and other associated problems.

Another feature of this invention which also aids in the

reduction of false loft and related problems is particularly useful for

barrel shaped springs or other such springs which have a non-linear

profile. With such springs, the transverse seam between adjacent

springs in the string is shaped to conform to the profile of the springs

and thereby produce a tighter, more conforming fabric pocket around

the spring to avoid bunching or excess loose fabric around the spring.

Brief Description of the Drawings

The objectives and features of the invention will become

more readily apparent from the following detailed description taken in

conjunction with the accompanying drawings in which: Fig. 1 is a top plan view of a schematic representation

of a system and associated method according to a first embodiment

for producing a string of pocketed coil springs of this invention;

Fig. 2 is a side elevational view of the system and

method of Fig. 1 ;

Fig. 3 is a view similar to Fig. 1 of a second presently

preferred system and associated method according to this invention;

Fig. 4 is a side elevational view of the system and

method of Fig. 3;

Fig. 5 is a perspective view of a string of pocketed coil

springs produced according to this invention;

Fig. 6 is a cross-sectional view of an individual coil

spring encased within a fabric pocket as taken along line 6-6 of Fig.

5;

Fig. 7 is a side elevational view of a string of pocketed

coil springs produced according to an alternative embodiment of this

invention; and

Fig. 8 is a partial perspective view of a weld head used

to weld a transverse seam in the string of Fig. 7.

Detailed Description of the Invention

Referring to Fig. 1 , a first presently preferred

embodiment of a system 1 0 and associated method for forming a string 1 2 of pocketed coil springs 1 4 according to this invention is

shown. Fabric 1 6, preferably thermally weldable as is well known in

the art, is fed from a supply roll 1 8 around a roller 20 as shown in

Fig. 1 . Alternatively, the fabric 1 6 could be cotton or another

suitable material. The fabric 1 6 is folded generally in half

longitudinally about a longitudinal fold line 22 which coincides

approximately with a longitudinal centerline of the fabric 1 6. The

fabric 1 6 is folded about the longitudinal fold line 22 to produce a

first, upper ply 24 and a second, lower ply 26 of fabric 1 6 each with

a free edge 28 spaced from the longitudinal fold line 22. The folded

fabric 1 6 passes upper and lower input rollers 30, 32 prior to

entering a spring insertion station 34. The rollers 20, 30 and/or 32

may be rotationally driven.

The spring insertion station 34 includes a reciprocating

insertion plunger 36 having a cup-shaped spring receiving leading end

38 to receive therein a compressed coil spring 1 4. The plunger 36

extends to insert the compressed spring 1 4 between the plies 24, 26

and retracts to receive another compressed spring 1 4 for subsequent

insertion. The spring 1 4 is formed and compressed and loaded onto

the spring insertion plunger 36 and the fabric 1 6 is folded according

to one of any number of well known systems and methods for doing

so. Alternatively, the spring insertion station 34 may comprise two

U-shaped profiles which keep the spring 1 4 compressed and lead the springs 14 inside the folded fabric 1 6. In this method, the spring 1 4

is held with a horn (not shown) while the profiles return.

As the fabric 1 6 advances through the system 10, the

springs 14 inserted between the plies 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 1 6

as particularly shown in Figs. 1 and 2. Preferably, the support plates

40, 42 are centered between the free edges 28 and longitudinal fold

line 22 of the fabric 1 6 and may include a wider region 44 proximate

the spring insertion station 34 which tapers downwardly to a region

of smaller separation 46 between the plates 40, 42 as the fabric 1 6

and springs 1 4 advance through subsequent portions of the system

10.

Additionally, a plurality of spaced alignment wheels 48

which are mounted for rotation proximate the longitudinal fold line 22

and free edges 28 of the fabric 1 6 control and direct the movement

of the fabric 1 6 through the system 10. The alignment wheels

preferably include a plurality of projections 50 which engage the

fabric 1 6 to maintain the movement of the fabric 1 6 in an aligned

orientation with respect to the various stations and components of

the system 1 0.

A longitudinal seam forming station 52 is located

downstream from the spring insertion station 34 proximate the free edges 28 of the fabric 1 6, as shown in Figs. I and 2. After the

compressed springs 14 are inserted between the piies 24, 26, the

longitudinal seam forming station 52 joins the upper and lower plies

24, 26 of the fabric 1 6 together proximate their respective free

edges 28 thereby initially enclosing the springs 1 4 within the fabric

1 6. In a presently preferred embodiment, a longitudinal seam 54 is

formed between a thermal weld head 56 which reciprocates

downwardly and upwardly for cooperating welding engagement and

disengagement, respectively, relative to an anvil 58 positioned below

the lower ply 26. The reciprocating weld head 56 and anvil 58

cooperate to form the longitudinal seam 54 in the fabric 1 6 by

welding the respective plies 24, 26 together ultrasonically, thermally,

or the like as is well known by those skilled in the art. Alternatively,

the anvil 58 is moved reciprocally while the thermal weld head 56

remains stationary. The springs 1 4 remain compressed during the

formation of the longitudinal seam 54 and weld with their

longitudinal axes 60 generally perpendicular to the longitudinal seam

54. It should be appreciated that other means for joining the plies

24, 26 together to form the seams such as stitching, staples, or

other means are well within the scope of the present invention.

A first transport station 62 is located downstream from

the longitudinal seam forming station 52 and, in a presently preferred

embodiment, includes four transport bands 64. Each band 64 passes over spaced forward and trailing rollers 66, 68, at least one of which

is rotationally driven. A first pair of bands 64a at the first transport

station 62 contacts the fabric 16 proximate the longitudinal fold line

22 passing therebetween. Another pair 64b of transport bands 64

contacts the fabric 16 proximate the longitudinal seam 54 as shown

in Figs. 1 and 2. As the bands 64 pass around the spaced rollers 66,

68 in contact with the fabric 1 6, the fabric 1 6 is pulled from the

supply roll 18 through the upstream stations and is advanced toward

a downstream spring expansion station 70.

The compressed springs 14 are permitted to relax and

expand within the fabric 16 at the spring expansion station 70. In a

first embodiment, the expansion of the springs 14 is controlled by a

pair of oppositely rotating rotational members 72 on opposite sides

of the springs 14 as shown in Fig. 1 . An axis of rotation 74 of each

of the rotational members 72 according to the first presently

preferred embodiment of Fig. 1 is generally parallel to the longitudinal

axes 60 of the springs 14. Each rotational member 72 includes a

plurality of arcuate-shaped recesses 76, each of which combine 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 thereby control the expansion thereof.

Additionally, the rotational members 72 assist in advancing the springs 14 and fabric 1 6 toward a transverse seam forming station

78 located downstream therefrom.

The transverse seam forming station 78 forms a

transverse seam 80 in the fabric 1 6 between each of the adjacent

springs 14 which have expanded within the fabric 1 6 from their

compressed configuration. Preferably, the transverse seam forming

station 78 includes a transverse seam weld head 82 and a

cooperating transverse seam anvil 84 located on opposite sides of

the forming string 1 2 of pocketed coil springs 14 from each other, as

shown in Fig. 1 . As the springs 1 4 advance toward and through the

transverse seam forming station 78, the fabric 1 6 between the

springs 1 4 is joined together thereby completing individual pockets

86 for each of the springs 1 4 and enclosing the springs 1 4 within the

fabric 1 6. Once again, it should be readily appreciated that other

means for forming the transverse seam 80 such as stitching, staples

or the like may be used within the scope of this invention. While the

transverse seam 80 is formed, the fabric 1 6 is needed or gathered.

As such, the string 1 2 of pocketed coil springs 1 4 must give in or

contract somewhat to accommodate the seam forming process. This

can be accomplished with an active mechanism such as a driven

transport system or with in a passive manner such as friction

between the fabric 1 6 and the transport rotational members 72. The longitudinal axes 60 of the springs 14 remain

generally parallel to the transverse seams 80 in the fabric 1 6.

However, due to the expansion of the springs 14, the longitudinal

seam 54 formed at the free edges 28 of the fabric 1 6 is positioned

generally on a side face 88 of the string 1 2 of pocketed coil springs

1 4 between top and bottom ends 90, 92 of the pocketed coil spring

1 4 as shown particularly in Figs. 5 and 6. With the longitudinal axes

60 of the springs 1 4 generally aligned and parallel with one another

within individual fabric pockets 86, the present invention avoids the

need for turning the springs 1 4 within the fabric pockets 86 as is

required in many prior art systems.

Referring to Figs. 5 and 6, the longitudinal seam 54

preferably becomes attached to the pockets 86 when the transverse

seam 80 is formed by the transverse seam forming station 78. As

such, in the region of the fabric 1 6 proximate the transverse seam

80, four layers of fabric 1 6 are welded together at the transverse

seam forming station 78. It should be appreciated that there are

other methods to fix the seam 80 in this manner, for example, the

longitudinal seam 54 could be positioned prior to entering the

transverse seam forming station 78 even if it is not welded to the

pockets 86 with the transverse seam 80. Further, the longitudinal

seam 54 may be located anywhere between the top and bottom of the string although it is shown in the drawings as approximately in

the middle thereof.

A downstream or second transport station 94 preferably

includes a pair of oppositely rotating transport wheels 96 each with

an axis 98 of rotation generally parallel to the longitudinal axes 60 of

the springs 14. A plurality of arcuate recesses 100 on the periphery

of the transport wheels 96 cooperate to at least partially surround

the pocketed springs 14 and advance them from the upstream

transverse seam forming station 78 for discharge and subsequent

packaging, storage or processing into a mattress, cushion or

innerspring unit.

An alternative embodiment of this invention is shown in

Figs. 3 and 4 and components of the system 10 of Figs. 3 and 4

which are similar to those of the first embodiment shown in Figs. 1

and 2, are identified by identical reference numerals and the previous

detailed description with respect to those items provided hereinabove

is likewise applicable to the embodiment of Figs. 3 and 4. The

second presently preferred embodiment shown in Figs. 3 and 4

includes divergent transport bands 102 located above and below the

fabric 1 6 and enclosed springs 14 at the spring expansion station 70.

The transport mechanism could be embodied with wheels as in Figs.

1 and 2 and/or transport bands as in Figs. 3 and 4 which are located

on the top and bottom of the string or the lateral side surfaces as desired. Each of the transport bands 102 of Figs. 3 and 4 pass over

forward and trailing rollers 1 04, 1 06, as shown particularly in Fig. 4.

Furthermore, a separation distance between the transport bands 102

increases in a downstream direction thereby permitting the controlled

expansion of the springs 14 positioned in the fabric 1 6 between the

transport bands 1 02. The relaxed and expanded springs 1 4 are then

advanced to the downstream transverse seam forming station 78 so

that the transverse seam 80 may be positioned between the adjacent

springs 1 4 to complete the individual fabric pockets 86.

An additional feature of this invention is shown in Figs.

7 and 8 and is particularly adapted for use in constructing strings 1 2

of pocketed coil springs 14a having a barrel shaped configuration as

shown in Fig. 7. Barrel shaped springs 1 4a are well known in the

industry and include a profile 1 08 in which the middle turns 1 1 0 of

the spring 1 4a have a greater diameter than the top turn 1 1 2 and

bottom turn 1 1 4 of the spring 1 4a. For example, the top and bottom

turns 1 1 2, 1 14 of the barrel shaped spring 1 4a may have a diameter

of about 1 .625 inches and the middle turn 1 1 0 have a diameter of

about 2.5 inches. When barrel shaped springs 1 4a are used in the

string 1 2, the transverse seam 80a adjacent to the spring 1 4a

conforms to the profile 1 08 of the spring 1 4a as shown in Fig. 7.

With the transverse seam 80a conforming to the profile 1 08 of the

spring 14a encased in the pocket a tighter pocket is produced with less loose fabric 1 6 in the string 1 2 and a better overall product,

especially with springs 1 4a 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 barrel shaped springs 1 4a the seam 80a may have

a pair of outwardly facing concave shapes forming an X or similar

configuration. A weld head 82a suitable for forming the transverse

seam 80a is shown in Fig. 8 in which a number of studs 1 1 6 are

arranged in the pattern shown so that adjacent studs 1 1 6 proximate

the top and bottom of the weld head 82a are spaced farther apart

than those in the middle to conform with the profiles 1 08 of the

adjacent barrel shaped springs 1 4a. Although the transverse seam

80a of Fig. 7 is symmetric, other configurations are contemplated

within the scope of this invention. Moreover, in another sense, this

feature of the invention is useful not only for barrel shaped springs

1 4a to form a tighter, more conforming fabric pocket, but also for

springs having a non-linear profile in general such as the barrel

shaped springs and hour glass shaped springs in which the middle

turns have a lesser diameter than the top and bottom turns.

From the above disclosure of the general principles of

the present invention and the preceding detailed description of at

least one preferred embodiment, those skilled in the art will readily

comprehend the various modifications to which this invention is susceptible. Therefore, we desire to be limited only by the scope of

the following claims and equivalents thereof.

We claim:

Claims

1 . A method of forming a string of pocketed coil springs

comprising the steps of:

feeding a supply of fabric;

folding the fabric about a longitudinal fold line into first and

second generally parallel plies of the fabric-

inserting a series of compressed springs between the first and

second plies;

joining the first and second plies together to form a

longitudinal seam proximate free edges of the first and second plies

opposite from the longitudinal fold line;

allowing the springs to at least partially expand within the

fabric so that a longitudinal axis of each of the springs is generally

perpendicular to the longitudinal seam of the fabric; and

forming a transverse seam in the fabric generally parallel to the

longitudinal axis of the springs and between adjacent springs to

thereby enclose each of the springs within a fabric pocket.

2. The method of claim 1 wherein the springs are allowed to at

least partially expand prior to forming the transverse seam and after

joining the first and second plies to form the longitudinal seam.

3. The method of claim 1 wherein the joining and forming steps

are performed by welding the fabric together.

4. The method of claim 1 wherein the expansion of the springs is

controlled by a pair of rotating members on opposite sides of the

springs within the fabric.

5. The method of claim 4 wherein the axes of rotation of the

rotating members is generally parallel to the longitudinal axes of the

springs and each rotating member comprises a plurality of arcuate

shaped recesses which combine to partially surround each spring.

6. The method of claim 4 wherein the axes of rotation of the

rotating members is generally perpendicular to the longitudinal axes

of the springs and each rotating member comprises a band passing

over spaced rollers, wherein a separation distance between the bands

increases in a downstream direction to thereby control the expansion

of the springs between the bands.

7. The method of claim 1 further comprising:

pulling the fabric between a pair of rotating transport members

spaced on opposite sides of the fabric and located downstream from

a position at which the transverse seam is formed, the rotating

transport members comprise a plurality of arcuate shaped recesses

which combine to partially surround each spring.

8. The method of claim 1 wherein the longitudinal seam is

positioned generally on the side of the springs between top and

bottom ends thereof in the formed string of pocketed coil springs.

9. The method of claim 1 wherein the springs are compressed

while the first and second plies are joined to form the longitudinal

seam and the springs are uncompressed while the transverse seam

between adjacent springs is formed.

10. The method of claim 1 wherein the orientation of the

longitudinal axes of the springs remains generally unaltered during

the entire process.

1 1 . The method of claim 1 wherein the inserting further comprises

inserting compressed springs which have a generally non-linear

shaped profile adjacent to the transverse seam and the forming of

the transverse seam further comprises forming the transverse seam

to generally correspond to at least a portion of the profile of the

adjacent springs.

12. The method of claim 1 1 wherein the springs being inserted are

barrel shaped.

13. The method of claim 1 wherein the inserting further comprises

inserting compressed barrel shaped springs and the forming of the

transverse seam further comprises forming the transverse seam to

have a generally concave configuration adjacent to the barrel shaped

springs.

14. The method of claim 1 wherein the recited steps are performed

sequentially in the order recited in claim 1 .

15. A method of forming a string of pocketed coil springs

comprising the steps of:

feeding a supply of thermally weldable fabric;

folding the fabric about a longitudinal fold line into first and

second generally parallel plies of the fabric;

inserting a series of compressed springs between the first and

second plies;

thermally welding the first and second plies together to form a

longitudinal seam proximate free edges of the first and second plies

opposite from the longitudinal fold line;

allowing the springs to at least partially expand within the

fabric so that a longitudinal axis of each of the springs is generally

perpendicular to the longitudinal seam of the fabric, the expansion of

the springs being controlled by a pair of rotating members on

opposite sides of the springs within the fabric;

thermally welding a transverse seam in the fabric generally

parallel to the longitudinal axis of the springs and between adjacent

springs to thereby enclose each of the springs within a fabric pocket;

and

pulling the fabric between a pair of rotating transport members

spaced on opposite sides of the fabric and located downstream from

a position at which the transverse seam is formed.

1 6. The method of claim 1 5 wherein the recited steps are

performed sequentially in the order recited in claim 15.

17. A method of forming a string of pocketed coil springs

comprising the steps of:

feeding a supply of fabric-

folding the fabric about a longitudinal fold line into first and

second generally parallel plies of the fabric;

inserting a series of compressed springs between the first and

second plies;

joining the first and second plies together to form a

longitudinal seam proximate free edges of the first and second plies

opposite from the longitudinal fold line; and

forming a transverse seam in the fabric between adjacent

springs to thereby enclose each of the springs within a fabric pocket

when inserted therein;

wherein the inserting further comprises inserting compressed

springs which have a generally non-linear shaped profile adjacent to

the transverse seam and the forming of the transverse seam further

comprises forming the transverse seam to generally correspond to at

least a portion of the profile of the adjacent springs.

18. The method of claim 17 wherein the springs are barrel shaped

and the transverse seam is formed to have a generally concave

configuration adjacent to the barrel shaped springs.

1 9. A system for forming a string of pocketed coil springs, each of

the springs being enclosed within a pocket formed of fabric, the

system comprising:

a spring insertion station at which compressed springs are

individually inserted between first and second plies of the fabric

folded about a longitudinal fold line;

a longitudinal seam forming station located downstream from

the spring insertion station, the longitudinal seam forming station

joining the first and second plies of the fabric together to form a

longitudinal seam proximate free edges of the first and second plies

opposite from the longitudinal fold line;

a spring expansion station located downstream from the

longitudinal seam forming station, the spring expansion station

permitting the springs to at least partially expand between the first

and second plies so that a longitudinal axis of each spring is generally

perpendicular to the longitudinal seam;

a transverse seam forming station located downstream from

the longitudinal seam forming station, the transverse seam forming

station forming a transverse seam in the fabric to separate each pair

of adjacent springs and thereby enclose each of the springs within a

fabric pocket when inserted therein; and

a transport station which advances the fabric and springs

contained therein through the respective stations.

20. The system of claim 1 9 wherein the transport station further

comprises a pair of rotating transport members spaced on opposite

sides of the fabric and located downstream from the spring

expansion station, the rotating transport members comprise a

plurality of arcuate shaped recesses which combine to partially

surround each spring and the surrounding fabric to thereby pull the

fabric and springs contained therein through the respective stations.

21 . The system of claim 1 9 wherein the spring expansion station

further comprises a pair of rotating members on opposite sides of the

springs within the fabric.

22. The system of claim 21 wherein the axes of rotation of the

rotating members are generally parallel to the longitudinal axes of the

springs and each rotating member comprises a plurality of arcuate

shaped recesses which combine to partially surround each spring.

23. The system of claim 21 wherein the axes of rotation of the

rotating members are generally perpendicular to the longitudinal axes

of the springs and each rotating member comprises a band passing

over spaced rotational mounted rollers, wherein a separation distance

between the bands increases in a downstream direction to thereby

control the expansion of the springs between the bands.

24. The system of claim 1 9 wherein the longitudinal seam forming

station and the transverse seam forming station each further

comprise a cooperating thermal weld head and anvil to form thermal

welds in the fabric.

25. The system of claim 24 wherein the weld head and the anvil at

the transverse seam forming station are configured to produce a

transverse seam which conforms to a non-linear profile of the

adjacent spring.

26. The system of claim 1 9 wherein the orientation of the

longitudinal axes of the springs remains generally unaltered from the

spring insertion station through formation of the string of pocketed

coil springs.

27. The system of claim 1 9 wherein the transverse seam forming

station forms the transverse seam which conforms to a non-linear

profile of the adjacent spring.

28. A system for forming a string of pocketed coil springs, each of

the springs being enclosed within a pocket formed of fabric, the

system comprising:

a spring insertion station at which compressed springs are

individually inserted between first and second plies of the fabric

folded about a longitudinal fold line;

longitudinal seam forming station located downstream from

the spring insertion station, the longitudinal seam forming station

including a cooperating thermal weld head and anvil to thermally

weld the first and second plies of the fabric together to form a

longitudinal seam proximate free edges of the first and second plies

opposite from the longitudinal fold line;

a spring expansion station located downstream from the

longitudinal seam forming station, the spring expansion station

including a pair of rotating members on opposite sides of the springs

within the fabric to permit the springs to at least partially expand

between the first and second plies so that a longitudinal axis of each

spring is generally perpendicular to the longitudinal seam;

a transverse seam forming station located downstream from

the spring expansion station, the transverse seam forming station

including a cooperating thermal weld head and anvil to thermally

weld a transverse seam in the fabric between each pair of adjacent springs to thereby enclose each of the springs within a fabric pocket

when inserted therein; and

a transport station which advances the fabric and springs

contained therein through the respective stations, the transport

station including a pair of rotating transport members spaced on

opposite sides of the fabric and located downstream from the spring

expansion station.

29. The system of claim 28 wherein the weld head and anvil of

the transverse seam forming station are configured to produce the

transverse seam which conforms to a non-linear profile of the

adjacent spring.

30. A system for forming a string of pocketed coil springs, each of

the springs being enclosed within a pocket formed of fabric, the

system comprising:

a spring insertion station at which compressed springs are

individually inserted between first and second plies of the fabric

folded about a longitudinal fold line, each of the springs having a

non-linear profile between a top and a bottom thereof;

a longitudinal seam forming station located downstream from

the spring insertion station, the longitudinal seam forming station

joining the first and second plies of the fabric together to form a

longitudinal seam proximate free edges of the first and second plies

opposite from the longitudinal fold line;

a spring expansion station permitting the springs to at least

partially expand between the first and second plies;

a transverse seam forming station forming a transverse seam

in the fabric to separate each pair of adjacent springs and thereby

enclose each of the springs within a fabric pocket when inserted

therein, the transverse seam having a non-linear profile conforming to

that of the adjacent spring; and

a transport station which advances the fabric and springs

contained therein through the respective stations.