EP0248661A1

EP0248661A1 - Apparatus for use in making spring units

Info

Publication number: EP0248661A1
Application number: EP87304934A
Authority: EP
Inventors: Lawrence Holland
Original assignee: Multilastic Ltd
Current assignee: Multilastic Ltd
Priority date: 1986-06-04
Filing date: 1987-06-03
Publication date: 1987-12-09

Abstract

A known kind of spring unit, for use in mattresses etc., is made as an assembly of spring bands (7,8,9) which are disposed side by side and linked together by transverse helical wires (6A,6B). Each spring band comprises a length of wire bent to form a row of springs (1). An integral connector (2) interconnects each pair of adjacent springs. In a known form of apparatus for assembling a spring unit, spring bands are fed intermittently past a linking station (13) where locating jaws (10,11) engage portions (3) of the bands and drive means (14) is operative to cause two parallel helical wires to travel axially across the band while rotating, to link those portions together. The invention provides such apparatus in which there is a trimming station downstream of the linking station. Here, end portions of the helical wires are trimmed off, and the trimmed ends are bent back, by combined trimming and bending devices (21 to 24).

Description

This invention relates to apparatus for use in making spring units. Spring units can be incorporated in mattresses, seats, cushions and other products.
The invention is particularly concerned with apparatus for use in making spring units of the kind comprising an assembly of spring bands and helical wires. Each of the spring bands is of a known kind (hereinafter referred to as a spring band of the kind specified) comprising a length of wire bent so as to form a plurality of coil springs disposed side by side in a row, ends of the coil springs lying in or near opposed edge faces of the band, and a plurality of connectors integral with the springs, each such connector lying in or near an edge face of the band and serving to interconnect two adjacent springs in the row.
Spring bands of the kind specified can be assembled together to form a spring unit of a known kind (hereinafter referred to as a spring unit of the kind specified) comprising a plurality of spring bands, each of the kind specified, disposed side by side so that their edge faces lie in or near main faces of the unit, and a plurality of helical wires, some lying in or near one of said main faces and others lying in or near the other of said main faces and each helical wire embracing component portions of each band.
The manufacture of one design of spring band of the kind specified is described and illustrated in the complete specification of British patent No. 937 644 granted to Willi Gerstorfer, and a method of assembling spring bands of that design with helical wires to form a spring unit of the kind specified, and one form of apparatus for carrying out that assembly, are described and illustrated in the complete specification of British patent No. 1 095 980 granted to Multilastic Limited.
The assembly apparatus is of the kind (hereinafter referred to as assembly apparatus of the kind specified) comprising feed means for intermittently feeding a plurality of spring bands of the kind specified in a downstream direction past a linking station, locating means at the linking station operative while the bands are stationary to engage the portions of the bands that are to be linked together, and drive means at the linking station for causing a helical wire to be rotated and moved axially, in the manner of a screw, across the bands so as to link those portions of the bands together.
In the manufacture of spring units of the kind specified with the aid of assembly apparatus of the kind specified, it is usual for the length of each helical wire to be a little greater than the width of the assembly of spring bands. When a helical wire is linked with the bands at the linking station, an end portion of the helical wire extends a short way beyond each side of the assembly. While still at the linking station the helical wire is then trimmed to length. Moreover, the end portions of the trimmed helical wire may be bent back so that the sharp ends of the wire do not project at the sides of the assembly. In being bent back these end portions preferably form loops or eyes that embrace adjacent parts of the marginal spring bands and thus prevent the helical wires rotating and becoming unlinked or partially unlinked from the bands of springs.
Mechanism for trimming the helical wires to length and for bending back the end portions of the wires has been provided at the ends of the locating means at the linking station. In addition it is normally necessary for the drive means for the helical wires to be located at one end of the locating means and for stop means for the helical wires to be located at the other end of the locating means. The stop means serves to prevent the helical wires running beyond the desired position when rotated by the driving means, something that is otherwise likely to occur, particularly as the drive means normally operates relatively rapidly so as to move a helical wire quickly across the bands of springs. The presence of a trimming device, and possibly a bending device as well, together with drive means and stop means at the ends of the locating means imposes considerable limitations on the design and operation of the mechanism. Moreover, the presence of those devices at the ends of the locating means makes it awkward to carry out adjustment and repair and awkward to remove the short lengths of wire that are trimmed from the ends of the helical wire.
An aim of the present invention is to overcome or at least to reduce some or all of those difficulties.
The present invention consists in assembly apparatus of the kind specified which also includes trimming means operative to trim off an end portion from at least one end of a helical wire, after it has been linked with the spring bands, the apparatus being characterised in that the trimming means is located at a trimming station downstream of the linking station and is operative to trim a helical wire after it has left the locating means and has been carried downstream to the trimming station by the spring bands to which it is linked.
The separation of the trimming means from the linking station in that manner can lead to numerous advantages. It generally makes it easier to obtain access to the trimming means and to driving means and to the stop means, when provided, to enable maintenance and repair to be carried out. It also reduces the limitations imposed on the design and function of those parts of the apparatus. It is also generally the case that it simplifies the removal of the end portions of the helical wires that are trimmed off by the trimming means.
The apparatus is normally such that, in use, the feed means allows the spring bands to remain stationary while a helical wire is linked to them at the linking station. Moreover, the apparatus is preferably such that the spacing between the linking station and the trimming station is such that when the feed means allows the spring bands to remain stationary for that purpose, a helical wire is located at the trimming station to be trimmed.
The trimming means preferably comprises a pair of spaced trimming devices, one operative to trim one end of a helical wire at the trimming station and the other operative to trim the other end of that helical wire.
The trimming devices are preferably so mounted that the spacing between them can be adjusted to enable the apparatus to be used in making spring units of different widths. In particular, when the apparatus is used to make spring units incorporating a different number of spring bands from that previously used, the spacing between the trimming devices can be adjusted as required. In a preferred arrangement, one of the said pair of trimming devices is adjustable along a track extending transversely of the apparatus at the trimming station. The fact that the trimming station is spaced away from the linking station generally enables there to be ample space available for the track. It is particularly convenient to arrange for that trimming device on the same side of the apparatus as the drive means to remain fixed and to enable the other trimming device to be mounted so that its spacing from the stationary trimming device can be adjusted. The advantage of that arrangement is that when the apparatus is adjusted to enable it to link together more or fewer spring bands than before, it is necessary for one edge of the spring unit to remain adjacent to the drive means and for the position of the other edge to be altered.
In a preferred form of apparatus the trimming means also includes a pair of secondary trimming devices, additional to the aforementioned or primary trimming devices, each of the secondary trimming devices being in fixed relationship to an associated one of the primary trimming devices, the primary trimming devices being operative to trim the ends of a helical wire in or near one of the main faces of a spring unit and the secondary trimming devices being operative to trim the ends of a helical wire in or near the other of the main faces of the spring unit.
Each trimming device preferably has a mouth, opening downstream, into which can enter an end portion of a helical wire that is to be trimmed, each trimming device also having deflector means operative to deflect an untrimmed end portion of a helical wire past the trimming device, the arrangement being such that in use a helical wire to be trimmed is moved downstream a short way past the trimming station, its untrimmed end portion being deflected past the trimming device by the deflector means, and is then moved a short way upstream again so that said untrimmed end portion enters the mouth of the trimming device preparatory to its being trimmed off.
In the assembly apparatus described and illustrated in the complete specification of the aforementioned British patent No. 1 095 980, the locating means comprises pairs of jaws, and the arrangement is such that when the feed means operates it brings portions of the bands that are to be linked together to positions a short way downstream of the jaws. The feed means then releases the bands, and closure of the jaws, prior to the linking of a helical wire with those portions of the bands, pulls the bands slightly upstream. This same slight upstream movement of the bands can be used to bring a helical into the mouth of a trimming device.
The apparatus may be further characterised in that there is a bending device associated with each trimming device and operative to bend back an end portion of a helical wire that has been trimmed by the associated trimming device. The trimming and bending devices may be combined to form a composite trimming and bending device.
In the accompanying drawings:-

Figure 1 is a perspective view of part of a spring band of the kind specified and incorporating a preferred shape of connector;
Figure 2 is a schematic plan view of a spring unit of the kind specified and incorporating spring bands of the kind shown in Figure 1;
Figure 3 is a schematic plan view of apparatus for use in assembling a spring unit of the kind shown in Figure 2;
Figure 4 is a perspective view of a body used in assembly apparatus of the kind shown in Figure 3;
Figure 5 is a schematic elevation of means for supporting trimming and bending devices for use with assembly apparatus of the kind shown in Figure 3;
Figure 6 is an elevation, to a larger scale, of one of the combined trimming and bending devices of Figure 5;
Figure 7 is a plan view of the device shown in Figure 6; and
Figure 8 is an end view, to a larger scale, of the device shown in Figure 6, as viewed from the left of Figure 6.

The spring band illustrated in Figure 1 is a spring band of the kind specified and comprises a length of wire bent so as to form a plurality of coil springs 1 disposed side by side in a row, ends of the coil springs lying near opposed edge faces of the band. In this particular form of spring band, alternate springs are coils of one hand while the remaining spring are coils of the other hand. In this way each left-handed coil is disposed between two right- handed coils, and each right-handed coil is disposed between two left-handed coils. This arrangement, however, is not an essential feature of spring bands used in connection with the present invention. The length of wire also affords a plurality of connectors 2 that are integral with the coils 1. Each connector lies at or near an edge face of the band and serves to connect two adjacent springs in the row. Each connector 2 extends past those two springs and has two spaced end portions 3 with a intermediate portion 4 between them.
After the springs have been formed, a turn of each spring is passed round a turn of the next adjacent spring so that each spring becomes linked to its neighbouring two springs. This interlinking of the springs is already known in spring bands of this kind.
A spring band of the kind described can be made by a spring-making machine of the kind described and illustrated in the complete specification of the aforementioned British patent specification No. 937 644.
After a spring band of that kind has been made, the band incorporating rectilinear connectors of rather greater length than usual, each connector in turn is introduced between appropriately shaped dies which are then closed to bend a central part of the intermediate portion to form a transversely extending part that constitutes a supporting structure 5 of a kind that is the subject of British patent No. 2 143 731. It is to be understood that the supports 5 form no part of the present invention and may be omitted, if desired.
Spring bands of the kind illustrated in Figure 1 are assembled together to form a spring unit of the kind illustrated schematically in Figure 2. The spring unit is of the kind specified and comprises spring bands disposed side by side with their edge faces lying in or near the main planes of the unit, and a plurality of helical wires. Some of the helical wires 6A lie in or near one main plane of the unit, while other helical wires 6B, lie in or near the other main plane thereof. Each helical wire embraces component portions of each spring band, namely two adjacent end portions 3 of two neighbouring connectors.
Each of the two marginal spring bands 7 and 8 of the unit is so orientated that its component connectors 2 lie at or close to the sides of the unit, while the remaining spring bands, 9, are all orientated in the same way as the marginal band 7. As the connectors of the marginal bands 7 and 8 are at or close to the sides of the unit they assist in strengthening the marginal parts of the unit, parts that tend to yield unduly. Moreover the connectors of the marginal bands are suitably placed for attachment to peripheral frames lying in or near the main planes of the unit. The frames serve to strengthen the marginal parts of the unit and are made from flexible and resilient strip metal.
The spring bands can be assembled with the aid of assembly apparatus of the kind described and illustrated in the complete specification of the aforementioned British patent No. 1 095 980. In accordance with the present invention, however, the layout of that assembly apparatus is modified in the manner illustrated schematically in Figure 3. In this Figure there are shown the spring bands 7, 8 and 9 being unwound from rolls 12 of spring banding and fed past a linking station 13 at which locating means, in the form of pairs of jaws 10 and 11, engage end portions 3 of the connectors that are to be linked. At one side of the linking station 13 is drive means 14 operative in use to cause helical wires to be rotated and moved axially, in the manner of screws, across the bands so as to link the end portions together.
The marginal band 8, which is orientated in a manner different from the bands 7 and 9, is adjacent to the drive means 14. The advantage of that arrangement is that if it is desired to reset or adjust the apparatus to enable it to make spring units of a different width, more (or fewer) of the jaws can be brought into operation at that side of the linking station further from the drive means, and no special arrangement has to be made for the marginal band at that side of the unit as that marginal band is orientated in the same manner as all the other bands except the band 8. For example, if it were desired to make a unit which additionally incorporated bands 15, only a minimum of alteration would be required, and what had previously been the marginal band 7 would merely become one of the intermediate bands.
The helical wires 6 are preformed and precut to a length a little greater than the width of the finished spring unit. In order to prevent the drive means causing the helical wires to travel beyond their desired positions, use is made of jaws of a form illustrated in Figure 4. The jaws are disposed at that side of the linking station remote from the drive means 14, and immediately adjacent to the marginal band 7. The jaws are therefore disposed at the locations indicated at 16 in Figure 3. There are two pairs of jaws, one aligned with drive means for one helical wire 6A and the other aligned with the drive means for the other helical wire 6B.
Each jaw, 17, comprises a block of metal with a planar front face 18, formed with a row of recesses 19. Each recess 19 is of part-spherical shape and has a circular mouth. The axes of the recesses are normal to the planar face 18 of the jaw. The axes are spaced uniformly apart, the distance between each axis and the next being equal to the pitch length of the helical wires. Each recess in the row is less deep than the preceding recess in the row.
The jaws of each pair are disposed in exactly the same manner as the jaws described in the complete specification of British patent No. 1 522 611 granted to Multilastic Limited. In use, when a pair of jaws 17 is closed and the leading end of a helical wire enters the recesses 19, the helical wire comes into frictional contact with an interior face of each of the recesses in turn. Owing to the progressively decreasing depth of the recesses, the force exerted on the wire by each recess is greater than that exerted by the preceding recess. In consequence the helical wire is rapidly brought to a halt.
If it is desired to adjust the apparatus to enable it to make a spring unit of a different width, the standard jaws next to the marginal band of the unit can be replaced by jaws 17.
One jaw of each pair of jaws 17 carries a proximity switch 20 at that end thereof closer to the spring unit. The unit is such that in use the switch operates, in response to the presence of a helical wire entering between the jaws 17, to yield a signal indicating that a helical wire is in place. When both switches at the linking station have been operated, to signal the presence of two helical wires 6A and 6B, the jaws are opened and the spring bands are fed forward. This sequence of events may be initiated automatically in response to operation of both the proximity switches.
Jaws of the kind illustrated in Figure 4 are of a new form and can, of course, be used in any appropriate assembly apparatus in which helical wires need to be brought to a halt.
Each time the jaws open the linked spring bands are fed forward by feed means. Consequently, projecting ends of upper and lower helical wires are brought adjacent to devices operative to trim and bend the helical wires. These devices are mounted downstream of the jaws as described in more detail below. The assembly apparatus operates in such a manner that during each cycle of operation the spring bands are moved forward to an extent such that the end portions of the connectors that are to be linked together by a helical wire are carried a short way past the path that helical wire will subsequently follow through the closed jaws. The forward movement of the bands is effected by fingers (not shown) which form part of the feed means. The fingers engage the bands and push them forward. They then withdraw from engagement and return, allowing the resilience of the bands to carry the end portions of the connectors backwards to a small extent preparatory to the closure of the jaws. Moreover, when the jaws close, they, too, pull the previously linked bands backwards to a further small extent. The devices for trimming and bending the helical wires are so designed that, during the forward movement of the bands, the projecting end portions of the helical wires are guided past the devices, but when the bands move backwards, as described above, the projecting ends enter the mouths of the devices, those mouths opening downstream of the apparatus. After the projecting ends have entered the mouths, the devices are then operated to trim and bend the helical wires.
The location of the combined trimming and bending devices is indicated at 21, 22, 23 and 24 in Figure 3 and also in Figure 5. The devices are supported on a vertical rectangular frame 25 which stands downstream of the linking station. The top of the frame lies below the path of the linked spring bands issuing from the linking station. At that side of the apparatus adjacent to the marginal band 8, an upright element 26 of the frame is extended upwards and carries devices 21 and 22. Towards the other side of the apparatus is a carriage 27 with supporting rollers 28 resting on parallel horizontal elements 29 of the frame. The elements 29 constitute a track. An upwardly extending element 30 of the carriage carries devices 23 and 24. Each of the four devices is similar in construction and operation, though the upper devices 21 and 23 are inverted to the lower devices 22 and 24. Locating or locking means (not shown) is provided to fix the carriage 27 relatively to the frame 25. When it is desired to adjust the apparatus to enable it to make spring units of a different width, the carriage can be released and moved along the frame on its rollers to an appropriate position where it is located or locked again.
The combined trimming and bending device 24 is illustrated in detail in Figures 6, 7 and 8. The device has a fixed plate 31 which is secured to the element 30 of the carriage by a horizontally projecting supporting rod (not shown). A lateral extension 32 of the plate carries a bracket 33 to which is pivoted at 34 the cylinder 35 of a pneumatic piston-and-cylinder unit 36. The piston rod 37 of the unit 36 is pivoted at 38 to one end of an arm 39 of which the other end is pivoted to the plate 31 by means of a pivot rod 40. One end of the rod 40 enters a bearing hole in the plate 31, while the other end of the rod enters a bearing hole in a plate 41 parallel with the plate 31 and secured to it by screws 42. A spacer 43 separates the plates 31 and 41.
A cam 44 fixed to the pivot rod 40 rotates in a slot 45 in an arm 46 of which one end is pivoted to the plate 31 by a pivot 47. The other end of the arm 46 carries a tool 48 which is secured to the arm by screws 49.
A bracket 50 secured to the back of the plate 31 supports one end of the cylinder 51 of a second pneumatic piston-and-cylinder unit 52. The piston rod 53 of the unit 52 is connected to the rear side block 54 which is fixed to a front slide block 55 by rods which extend through a vertically extending slot 56 in the plate 31. The front slide block 55 runs in a groove 57 formed in the front face of the plate 31. A first tool support 58 is secured by screws 59 to the front side block 55 and a second tool support 60 is secured to the first tool support by screws 61. A tool 62 is secured between the tool supports 58 and 60.
A locating bar 63 is mounted on top of the plate 31, an upper part of the bar projecting forwards above the level of the tool 48 so as to define the upper part of a mouth which opens downstream of the device. A guide plate 64 is secured to the bar 63 by screws 65. The guide plate is inclined upwards and forwards to the locating bar 63.
In use, when the linked bands are fed forward by the feed means, as described above, a helical wire, which is at the lower of the main faces of the length of spring unit and which embraces the end portions of two connectors forming part of the marginal band 7, rises up over the guide plate 64 and then drops again so that those linked end portions lie just in front of the locating bar 63. The subsequent slight rearward movement of the bands, as described above, then carries the linked end portions into the mouth 70 beneath the locating bar 63, the helical wire taking up the position indicated at 66 in Figures 6 and 8. A hemispherical locating boss 67 on the underside of the locating bar projects between adjacent coils of the helical wire and ensures that the helical wire is located in a desired axial position.
The second piston-and-cylinder unit 52 is then operated. This causes an upper part of the first tool support 58 to lie in front of the helical wire and thus to block its exit from beneath the locating bar 63. The rear upper edge of the first tool support is chamfered, as indicated at 68, to guide the helical wire rearwards in case it has not fully entered the mouth beneath the locating bar. The operation of the unit 52 also brings the tool 62 into a position between adjacent coils of the helical wire, the position being indicated by the chain-dotted lines 69. The first piston-and-cylinder unit 36 is next operated. This causes the arm 39 to rotate the cam 44, this rotation of the cam in turn causing rotation of the arm 46, but through a much smaller angle than that through which the arm 39 rotates. The provision of this mechanism incorporating the cam 44 and slot 45 gives rise to a considerable mechanical advantage. The rotary movement of the arm 46 causes the tool 48 to engage the helical wire and to sever it against the tool 62. Further rotary movement of the arm 46 causes the tool 48 to deform what is now the last turn or coil of the helical wire into the shape of a closed loop or eye, a loop or eye which embraces or encircles a constituent wire of the marginal band 7. This positively prevents the subsequent occurrence of any significant rotation of the helical wire relative to the bands to which it is linked.
The severed end portion of the helical wire is free to drop from the device and can fall into a funnel or chute (not shown) leading to a waste container. This arrangement is largely made possible owing to the fact that the device is spaced away from the jaws of the apparatus. In earlier designs of apparatus, in which the helical wires were trimmed and bent while still located within the jaws it proved difficult or even impossible satisfactorily to arrange for the automatic collection and removal of the severed end portions of the helical wires.
After the loop or eye has been formed, the piston-and- cylinder units 36 and 52 are operated to retract their piston rods 37 and 53 respectively, thereby leading to the return of the device to the state illustrated. Then, on further forward movement of the linked bands the helical wire 66 is free to leave the device.
It will be appreciated that the guide plates of the upper devices 21 and 23 push the marginal bands downwards during forward movement of the linked bands. Although the upper devices 21 and 23 are offset longitudinally of the apparatus from the lower devices 22 and 24, the bands are sufficiently supported by the lower devices to ensure that the bands are lightly compressed during this forward movement past the guide plates. Relaxation of this compression at the end of the forward movement causes the helical wire that has just passed the upper guide plates to spring upwards into a position in front of the mouths of the upper devices.
Operation of the devices 21, 23 and 24 occurs simultaneously, but a pneumatic timer device (not shown) causes a slight delay in the operation of the device 22. This ensures that by the time device 22 has completed its operation the other three devices have already completed their operations. A proximity switch or micro-switch (not shown) operated by the device 22 on completion of its operation provides a signal indicating that the next step in the operation of the apparatus - the opening of the jaws and forward feed of the bands - can take place.
After leaving the trimming and bending devices the length of spring unit is fed to apparatus for severing and dividing the length of spring unit into individual units each of predetermined length.

Claims

1. Apparatus for use in making spring units of the kind comprising an assembly of spring bands (7,8,9) and helical wires (6A,6B), each spring band comprising a length of wire bent so as to form a plurality of coil springs (1) disposed side by side in a row, ends of the coil springs lying in or near opposed edge faces of the band, and a plurality of connectors (2) integral with the springs, each such connector lying in or near an edge face of the band and serving to interconnect two adjacent springs in the row, the spring bands being disposed side by side so that their edge faces lie in or near main faces of the unit, and a plurality of helical wires, some (6A) lying in or near one of said main faces and others (6B) lying in or near the other of said main faces and each helical wire embracing component portions (3) of each band, the apparatus comprising feed means for intermittently feeding a plurality of the spring bands in a downstream direction past a linking station (13), locating means (10,11) at the linking station operative while the bands are stationary to engage the portions (3) of the bands that are to be linked together, and drive means (14) at the linking station for causing a helical wire to be rotated and moved axially, in the manner of a screw, across the bands so as to link those portions of the bands together, the apparatus also including trimming means (21,22,23,24) operative to trim off an end portion from at least one end of a helical wire, after it has been linked with the spring bands, the apparatus being characterised in that the trimming means (21 to 24) is located at a trimming station downstream of the linking station (13) and is operative to trim a helical wire after it has left the locating means and has been carried downstream to the trimming station by the spring bands to which it is linked.

2. Apparatus according to claim 1 further characterised in that the trimming means comprises a pair of spaced trimming devices, one (21) operative to trim one end of a helical wire at the trimming station and the other (23) operative to trim the other end of that helical wire.

3. Apparatus according to claim 2 further characterised in that the trimming devices are so mounted that the spacing between them can be adjusted to enable the apparatus to be used in making spring units of different widths.

4. Apparatus according to claim 3 further characterised in that one (23) of said pair of trimming devices is adustable along a track (29) extending transversely of the apparatus at the trimming station.

5. Apparatus according to any one of claims 2 to 4 in which the trimming means also includes a pair of secondary trimming devices (22,24), additional to the aforementioned or primary trimming devices (21,23), each of the secondary trimming devices being in fixed relationship to an associated one of the primary trimming devices, the primary trimming devices being operative to trim the ends of a helical wire in or near one of the main faces of a spring unit and the secondary trimming devices being operative to trim the ends of a helical wire in or near the other of the main faces of the spring unit.

6. Apparatus according to any one of claims 2 to 5 further characterised in that each trimming device has a mouth (70), opening downstream, into which can enter an end portion of a helical wire that is to be trimmed, each trimming device also having deflector means (64) operative to deflect an untrimmed end portion of a helical wire past the trimming device, the arrangement being such that in use a helical wire to be trimmed is moved downstream a short way past the trimming station, its untrimmed end portion being deflected past the trimming device by the deflector means, and is then moved a short way upstream again so that said untrimmed end portion enters the mouth of the trimming device preparatory to its being trimmed off.

7. Apparatus according to any one of claims 2 to 6 further characterised in that there is a bending device associated with each trimming device and operative to bend back an end portion of a helical wire that has been trimmed by the associated trimming device.