Pocketed spring unit and method of manufacture

Abstract

A resilient unit 300 with an array of first coil springs 310 held in pockets formed between piles 320 of material that extend across plural rows of springs and are joined, such as by ultrasonic weldin

Description

The present invention relates to a resilient unit, and to an apparatus and a method for making a resilient unit, such as may be used in an upholstered article for example, and is concerned particularly, although not exclusively, with controlling the positioning of resilient elements during manufacture of such a unit. A method and apparatus for making a resilient unit, such as a mattress, for example, are disclosed in our European patent number EP 1993 947 B. This describes the formation of a pocketed spring unit by feeding springs between upper and lower sheets of material, and joining the sheets together, for example by welding, at locations between the springs, to form pockets around the springs. Figure 1 shows schematically an example of apparatus described in the abovementioned patent. Springs 100 are conveyed under compression to a spring-inserting position by spaced belts 110a and 110b, where they are pushed by mechanical pushers 120 that are driven by a motor 130 to move in a reciprocating motion, indicated by arrow Al. The pushers 120 push the springs into positions between sheets of material 130 fed from upper and lower supply rollers 140a and 140b via guide rollers 150a and 150b. The sheets 130 are joined at positions between springs by the reciprocating action of an upper welding tool 160a in the direction shown by arrow A2 that presses the sheets together and fuses them on a welding anvil 160b. Rows of springs become encapsulated in pockets as the resilient unit 170 thus formed is advanced in the direction of Arrow A3 . A refinement of this arrangement is described in our European patent number EP 3 426 099 B. Figure 2 shows schematically an 200 apparatus for forming a resilient unit. The apparatus comprises a conveyor 210 and first and second spring supply stations 212 and 214, arranged in use to deposit respectively first and second spring types 216 and 218 under compression onto the conveyor. The conveyor is arranged in use to convey a row of the springs 216, 218 in a direction shown by Arrows A4 towards pocketing station 220. The conveyor may be according to any suitable design that allows the springs to be transported securely, preferably under compression. For example, a pair of superposed belts or a single belt opposite a stationary plate, or a conveyor containing spring retaining members, can be used. At the pocketing station 220 the springs are urged from the conveyor into positions between upper and lower sheets 222 and 224, by a plurality of inserter devices 226 that move together in a reciprocating fashion in the direction of arrow A5, before retracting to the position shown. After each row of springs is inserted between the sheets 222, upper and lower computer-controlled welding tools (not shown) come together at positions P between the springs to join the sheets together, forming pockets in which the springs are encased. After each welding event the resilient unit is indexed forwards a distance equal to one pocket width in the direction of Arrows A6 by computer-controlled drive means (not shown). The next row of springs is then conveyed into position ready for insertion between the sheets of material, and the process is repeated. The two spring supply stations are arranged to supply springs that differ from one another in at least one characteristic. In this case the springs 216 are of smaller diameter and are taller and stiffer than the springs 218. The result is a resilient unit in which alternate springs are taller and stiffer than their immediate neighbours. Because of its appearance this type of unit is sometimes referred to as a "hi-lo" unit. The result is an array of springs in which the springs are arranged in rows, with alternate positions in each row being occupied by springs having a different characteristic. Embodiments of the present invention aim to provide a resilient unit, and a method and an apparatus for making a resilient unit, in which springs of different characteristic may be arranged in a more space-efficient manner, such that the spring count is increased per unit area, when compared to the prior art. The present invention is defined in the attached independent claims, to which reference should now be made. Further, preferred features may be found in the sub-claims appended thereto . According to one aspect of the present invention, there is provided a method of forming a resilient unit comprising an array of coil springs located in pockets formed between substantially continuous, axially superposed plies of pocketing material, which plies are shared by a plurality of the springs and are joined at positions between the springs, wherein a set of first springs form first rows such that springs from adjacent first rows form clusters, each cluster defining a space therein, and wherein a set of second springs form second rows such that the second springs are located within the spaces, wherein the method comprises transferring the springs from a substrate to positions between the plies by urging the springs from the substrate, wherein the first springs are arranged on the substrate with their centres in a first line at spaced apart intervals and the second springs are arranged on the substrate with their centres in a second line at spaced apart intervals between the first springs, and wherein the first and second lines are spaced from one another transversely with respect to the substrate. The method may comprise transferring the springs from a substrate which is a conveyor. The transfer of the springs from the substrate to positions between the plies of pocketing material is preferably effected by pusher tools. More preferably, a first set of pusher tools may be arranged to transfer the first springs and a second set of pusher tools may be arranged to transfer the second springs. In a preferred arrangement, the first and second pusher tools have different lengths and / or are arranged to travel different distances during pushing of the springs . More preferably, a row of first springs and a row of second springs are transferred substantially simultaneously from the substrate to positions between the plies. In a preferred arrangement, the plies of pocketing material are joined by welding, more preferably by ultrasonic welding. The welding may be effected by welding tools and the welding tools are preferably programmable, more preferably individually controllable, so that the positions of the welds may be selected according to the nature and / or position of the springs . According to another aspect of the present invention, there is provided a pocketed spring unit, comprising an array of springs in pockets formed between substantially continuous, axially superposed plies of pocketing material, which plies are shared by a plurality of the springs and are joined at positions between the springs, wherein a set of first springs form first rows such that springs from adjacent first rows form clusters, each cluster defining a space therein, and wherein a set of second springs form second rows such that the second springs are located within the spaces. Preferably the first and second springs differ from one another in at least one characteristic. The characteristic may be the diameter of the springs. More preferably, the first springs have a greater diameter than the second springs . In a further aspect, the invention provides a computer instructions that, when executed by a computer, cause the computer to perform a method of forming a resilient unit comprising an array of coils springs located in pockets formed between substantially continuous, axially superposed plies of pocketing material, which plies are shared by a plurality of the springs and are joined at positions between the springs, wherein a set of first springs form first rows such that springs from adjacent first rows form clusters, each cluster defining a space therein, and wherein a set of second springs form second rows such that the second springs are located within the spaces, wherein the method comprises transferring the springs from a substrate to positions between the plies by urging the springs from the substrate, wherein the first springs are arranged on the substrate with their centres in a first line at spaced apart intervals and the second springs are arranged on the substrate with their centres in a second line at spaced apart intervals between the first springs, and wherein the first and second lines are spaced from one another transversely with respect to the substrate. The invention also comprises a program for causing a device to perform a method of forming a resilient unit comprising an array of coils springs located in pockets formed between substantially continuous, axially superposed plies of pocketing material, which plies are shared by a plurality of the springs and are joined at positions between the springs, wherein a set of first springs form first rows such that springs from adjacent first rows form clusters, each cluster defining a space therein, and wherein a set of second springs form second rows such that the second springs are located within the spaces, wherein the method comprises transferring the springs from a substrate to positions between the plies by urging the springs from the substrate, wherein the first springs are arranged on the substrate with their centres in a first line at spaced apart intervals and the second springs are arranged on the substrate with their centres in a second line at spaced apart intervals between the first springs, and wherein the first and second lines are spaced from one another transversely with respect to the substrate. According to another aspect of the present invention, there is provided a method of making a ventilated pocketed spring unit, the unit comprising an array of coil springs in discrete pockets formed by axially superposed plies of pocketing material joined at locations between the springs, wherein at least some of the pockets include ventilation apertures, the method comprising forming a connection between the superposed plies at a location within a perimeter of a partially formed pocket, and inserting a spring into the partially formed pocket to cause the connection to break and thereby to cause a rupture in at least one of the plies in the location of the former connection. The method preferably includes closing the pocket with at least one further join after inserting the spring. The method may include forming the connection by a weld, more preferably an ultrasonic weld. The spring is preferably inserted into the partially formed pocket and is allowed to expand, at least partly, after completion of the pocket. In a preferred arrangement, the method comprises forming a connection between the plies, which connection comprises one or more spots, or dots. The invention also includes a ventilated pocketed spring unit, comprising an array of coil springs in discrete pockets formed by axially superposed plies of pocketing material joined at locations between the springs, wherein at least some of the pockets include ventilation apertures, and wherein the ventilation apertures comprise ruptures in the pocketing material of at least one of the plies, within a perimeter of at least one of the pockets. The plies / sheets are preferably substantially continuous and are preferably shared by a plurality of rows of pockets / springs . The invention may include any combination of the features or limitations referred to herein, except such a combination of features as are mutually exclusive, or mutually inconsistent. A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which: Figure 1 shows schematically a previously considered apparatus for making a resilient unit; Figure 2 shows schematically another previously considered example of an apparatus for making a resilient unit; Figure 3 shows schematically a resilient unit according to an embodiment of the present invention; Figure 4 shows schematically a first part of an embodiment of apparatus in accordance with the present invention, for making the unit of Figure 3; Figure 5 shows schematically a second part of an embodiment of an apparatus in accordance with the present invention, for making the unit of Figure 3; Figure 6 shows schematically a second embodiment of resilient unit according to the present invention; and Figures 7(a) to 7(c) are different views of part of the unit according to the second embodiment. Turning to Figure 3, this shows schematically, a resilient unit according to an embodiment of the present invention. The unit is shown generally at 300 and is shown in plan view. The unit comprises an array of first coil springs 310 that are held in pockets formed between axially superposed sheets 320 of pocketing material that extend across plural rows of springs and are joined at positions P between the springs 310 and also at the edges of the sheets. The joining is, in this example, by ultrasonic welding of the pocketing material (itself, in this case a nonwoven material, such as spun-bond polyester) and is shown as intermittent lines. The springs 310 are arranged in a grid-like pattern and a cluster C of four adjacent springs (one example shown shaded in the drawing) has within it a space S which is occupied by a second type of spring 330. In this case, the second type of spring 330 is a spring of smaller diameter. In alternative embodiments (not shown), the clusters may be made up of alternative numbers / geometries of springs. As they occupy the spaces S within the clusters C of first springs, the second springs 330 are arranged in positions that are offset from the first springs 310 in both X and Y axes . The relative sizes and / or characteristics of the first and second types of spring may be different in alternative embodiments (not shown). It should be understood that the resilient unit shown in Figure 3 is for the purposes of illustration only. In reality, there usually would be more springs in each of the X and Y axes. Figure 4 shows a first part of apparatus for making the unit of Figure 3. A row of first springs 310 and a row of second springs 330, both sets held under compression on a conveyor 340, are offset in a direction longitudinally of the conveyor (X-axis) and also transversely (Y-axis) with respect to one another. The conveyor moves in a direction indicated by Arrow A4' . An example of a spring transportation apparatus suitable for holding springs under compression may be found in our UK Patent Number GB 2565194 B. When rows of the springs have reached a position opposite a pocketing station 350 a pusher mechanism 360 urges the springs 310 and 330 from the conveyor to the pocketing station so that the springs can adopt positions between axially superposed plies of pocketing material 320 in partially formed pockets. The pusher mechanism 360 reciprocates in a direction indicated by Arrow A5', i.e., across the width of the conveyor. The pusher mechanism has inserter tines 365 which are arranged alternately in two lengths, so that as they push the springs 310 and 330 the springs maintain their biaxially offset positions when they locate between the pocketing material sheets. Note that the two sets of springs 310 and 330 are inserted substantially simultaneously in this embodiment. The sheets 320 are joined (in this example ultrasonically welded) at positions P between the springs and at the edges of the unit to secure the springs in individual pockets, the second springs 330 each occupying a pocket formed in the spaces S at the centre of a cluster of four first springs 310 (again, example shown shaded). After each cycle of insertion the pockets are completed, by joining of the sheets to close the pockets, preferably by ultrasonic welding, the unit is indexed forwards in the direction of Arrow A6' , whereupon the springs are released from compression and expand somewhat, axially, in their pockets. Figure 5 shows the conveyor 340 at an earlier stage, where two spring-forming devices 370 and 380 each deposit springs, respectively of the first type 310 and of the second type 330, on the conveyor. Figure 6 shows an alternative embodiment of resilient unit, generally at 400, comprising a plurality of resilient coil springs 410 located in pockets 420 formed between axially superposed sheets of pocketing material 430 that have been joined together (for example by ultrasonic welding) at positions P, between the springs and at edges. In this embodiment, there are only springs of one type, and there is only one type of row, though the concept could be used with more complex row / cluster structures such as that of Figures 3-5, for example. In the case of each pocket 420, in addition to the joining at positions P between the springs and at the edges, there has been a further joining / connection (in this example by ultrasonic welding) of the sheets 430 substantially within the footprint of the pocket, and more particularly within the diameter of the spring 410, at positions P' prior to insertion of the spring between the sheets. The effect of the connection P' is that when the spring is inserted, for example in the way described above in relation to Figure 4, it breaks the connection P' leaving behind a hole in the pocket. Figures 7 (a)-7(c) show the effect of the process described above in relation to Figure 6. Figure 7(a) shows part of the resilient unit 400 in side view prior to the insertion of springs. The drawing shows the sheets 430 of pocketing material, the joins P between the pockets and at the edges of the unit, and also the connections P' within the area of the pocket. In this example, the connections P' are ultrasonic welds, in which the pocketing material from the two superposed sheets 430 has been fused together by ultrasonic energy. Figure 7(b) shows the unit after the springs 410 have been inserted. During insertion, and subsequent expansion, of the springs 410, the superposed sheets 430 are forced apart and at least one of the plies / sheets 430 becomes ruptured as a result, leading to the formation of apertures A' where the connections P' were previously. Figure 7(c) is a larger view of a single spring in its pocket. This is an efficient method of forming ventilation apertures in the pockets, particularly as it does not require an extra manufacturing step, since the joining (welding) of the sheets and the insertion of the springs between the partially formed pockets must happen in any case. The number, size and position of the joins P' within the pocket area can be varied to determine the level of ventilation required. 5 Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance, it should be understood that the applicant claims protection in respect of any patentable feature or combination of features referred to herein, and / or 10 shown in the drawings, whether or not particular emphasis has been placed thereon.

Claims

l.A method of forming a resilient unit comprising an array of coil springs located in pockets formed between substantially continuous, axially superposed plies of pocketing material shared by a plurality of the springs and joined at positions between the springs, wherein a set of first springs form first rows such that springs from adjacent first rows form clusters, each cluster defining a space therein, and wherein a set of second springs form second rows such that the second springs are each located within the spaces, wherein the method comprises transferring the springs from a substrate to positions between the plies by urging the springs from the substrate, wherein the first springs are arranged on the substrate with their centres in a first line at spaced apart intervals and the second springs are arranged on the substrate with their centres in a second line at spaced apart intervals between the first springs, and wherein the first and second lines are spaced from one another transversely with respect to the substrate.2.A method according to Claim 1, comprising transferring the springs from a substrate which is a conveyor.3.A method according to Claim 1 or 2, wherein the transfer of the springs from the substrate to positions between the plies of pocketing material is effected by pusher tools.4.A method according to Claim 3, wherein a first set of pusher tools is arranged to transfer the first springs anda second set of pusher tools is arranged to transfer the second springs.5.A method according to Claim 4, wherein the first and second pusher tools have different lengths and / or are arranged to travel different distances during pushing of the springs.6.A method according to any of the preceding claims, wherein a row of first springs and a row of second springs are transferred substantially simultaneously from the substrate to positions between the plies.7.A method according to any of the preceding claims, wherein the plies of pocketing material are joined by welding, more preferably by ultrasonic welding.

8. A method according to Claim 7, wherein the welding is effected by welding tools and the welding tools are controllable, so that the positions of the welds may be selected according to the nature and / or position of the springs .

9. A pocketed spring unit, comprising an array of springs in pockets formed between substantially continuous, axially superposed plies of pocketing material shared by a plurality of the springs and joined at positions between the springs, wherein a set of first springs form first rows such that springs from adjacent first rows form clusters, each cluster defining a space therein, and wherein a set of second springs form second rows such that the second springs are each located within the spaces.10.A unit according to Claim9, wherein the first and secondsprings differ fromanotherat leastcharacteristic.11.A unit according to Claim 10, wherein the characteristicis the diameter of the springs.12.A unit according to Claim 11, wherein the first springshave a greater diameter than the second springs.

13. A computer programme product on a computer readablemedium, comprising instructions that, when executed by acomputer, cause the computer to perform a method of forminga resilient unit comprising an array of coils springslocatedin pockets formed between substantially continuous, axiallysuperposed plies of pocketing material shared by a plurality of the springs and joined at positions between the springs,wherein a set of first springs form first rows such that springs from adjacent first rows form clusters, each cluster defining a space therein, and wherein a set of second springs form second rows such that the second springs are each located within the spaces, wherein the method comprises transferring the springs from a substrate to positions between the plies by urging the springs from the substrate, wherein the first springs are arranged on the substrate with their centres in a first line at spaced apart intervals and the second springs are arranged on the substrate with their centres in a second line at spaced apart intervals between the first springs, and wherein the first and second lines are spaced from one another transversely with respect to the substrate.14.A program for causing a device to perform a method offorming a resilient unit comprising an array of coils springs located in pockets formed between substantially continuous, axially superposed plies of pocketing material shared by a plurality of the springs and joined at positions between thesprings, wherein a set of first springs form first rows such that springs from adjacent first rows form clusters, each cluster defining a space therein, and wherein a set of secondsprings form second rows such that the second springs are each located within the spaces, wherein the method comprises transferring the springs from a substrate to positions between the plies by urging the springs from the substrate, wherein the first springs are arranged on the substrate withtheir centres in a first line at spaced apart intervals andthe second springs are arranged on the substrate with their centres in a second line at spaced apart intervals between the first springs, and wherein the first and second lines are spaced from one another transversely with respect to the substrate .15.A method of making a ventilated pocketed spring unit, the unit comprising an array of coil springs in discrete pockets formed by axially superposed plies of pocketing material joined at locations between the springs, wherein at least some of the pockets include ventilation apertures, the method comprising forming a connection between the superposed plies at a location within a perimeter of a partially formed pocket, and inserting a spring into the partially formed pocket to cause the connection to break and thereby to cause a rupture in at least one of the plies in the location of the former connection.

16. A method according to Claim 15, including closing the pocket with at least one further join after inserting the spring.17.A method according to Claim 15 or 16 including forming the connection by a weld, more preferably an ultrasonic weld.18.A method according to any of Claims 15-17, wherein the spring is inserted into the partially formed pocket and is allowed to expand, at least partly, after completion of the pocket.19.A method according to any of Claims 15-18, wherein the method comprises forming a connection between the plies, which connection comprises one or more spots, or dots.20.A ventilated pocketed spring unit, comprising an array of coil springs in discrete pockets formed by axially superposed plies of pocketing material joined at locations between the springs, wherein at least some of the pockets include ventilation apertures, and wherein the ventilation apertures comprise ruptures in the pocketing material of at least one of the plies, within a perimeter of at least one of the pockets .

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