GB2191087A - Apparatus for use in making spring units - Google Patents

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

SPECIFICATION Apparatus for use in making spring units This invention relates two 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 ofthe kind comprising an assembly of spring bands and helical wires. Each ofthe spring bands is of a known kind (hereinafter referred to as a spring band ofthe kind specified) comprising a length of wire bent so asto form a plurality of coil springs disposed side by side in a row, ends ofthe 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 ofthe band and serving to interconnect two adjacent springs in the row.

Spring bands ofthe kind specified can be assembled together to form a spring unit of a known kind (hereinafter referred to as a spring unit ofthe kind specified) comprising a plurality of spring bands, each ofthe kind specified, disposed side by side so that theiredgefaces lie in or near main faces ofthe 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 wirestoformaspring unitofthekindspecified,and one form ofapparatus fo r ca rryi ng 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 ofthe kind specified) comprising feed means for intermittently feeding a plurality of spring bands ofthe kind specified in a downstream direction past a linking station, locating means at the linking station operativewhilethe bands are stationary to engage the portions ofthe 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 asto linkthose portions ofthe bands together.

in the manufacture of spring units ofthe kind specified with the aid of assembly apparatus ofthe kind specified, it is usual for the length of each helical wiretobea Iittlegreaterthanthewidthofthe assembly of spring bands. When a helical wire is linked with the bands at the linking station, an end portion ofthe helical wire extends a short way beyond each side of the assembly. While still atthe linking station the helical wire isthen trimmedto 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 ofthe assembly.In being bent backthese end portions preferably form loops or eyes that embrace adjacent parts ofthe marginal spring bands and thus prevent the helical wires rotating and becoming unlinked or partiallyunlinked from the bands of springs.

Mechanism fortrimming the helical wires to length and for bending back the end portions of the wires has been provided atthe 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 ofthe locating means and for stop meansforthe helical wires to be located atthe other end ofthe locating means. The stop means serves two prevent the helical wires running beyond the desired position when rotated by the driving means, something that is otherwise likelyto occur, particularly as the drive means normally operates relativelyrapidlysoasto movea helicalwirequickly across the bands of springs.The presence of a trimming device, and possibly a bending device as well,togetherwith drive means and stop means at the ends ofthe locating means imposes considerable limitations on the design and operation of the mechanism. Moreover, the presence of those devices at the ends ofthe 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 ofthe present invention is to overcome or at least to reduce some or all of those difficulties.

The present invention consists in assembly apparatus ofthe kind specified which also includes trimming means operative to trim offan end portion from at least one end of a helical wire, after it has been linked with the spring bands, the apparatus being characterised inthatthetrimming means is located atatrimming station downstream ofthe 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 leadto 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 repairto be carried out. Italso reduces the limitations imposed on the design and function of those parts ofthe apparatus. It is also generally the case that it simplifies the removal ofthe end portions of the helical wires that are trimmed off bythetrimming means.

The apparatus is normally such that, in use,the feed means allows the spring bands to remain stationarywhilea helical wire is linkedtothem atthe 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 bandstoremain stationaryforthat purpose, a helical wire is located atthetrimming 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 atthetrimming 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 ofthe said pairoftrimming devices is adjustable along a track extending transversely ofthe apparatus atthetrimming station. The fact that thetrimming station is spaced away from the linking station generally enables there to be ample space available forthe track.It is particularly convenient to arrangeforthattrimming device on the same side ofthe 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 itto linktogether more orfewerspring bands than before, itis necessaryforone edge ofthe 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 ofthe secondary trimming devices being in fixed relationship to an associated one ofthe primary trimming devices, the primary trimming devices being operative to trim the ends of a helical wire in or near one ofthe main faces of a spring unit and the secondary trimming devices being operative to trim the ends of a helical wire in or nearthe other ofthe main faces ofthe 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 ofthetrimming 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 095980,the locating means comprises pairs of jaws, and the arrangement is suchthatwhen the feed means operates it brings portions of the bands that are to be linked togetherto positions a short way downstream of the jaws. The feed means then releases the bands, and closure of the jaws, priortothe 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 lisa perspective view of part of a spring band ofthe kind specified and incorporating a preferred shape of connector; Figure2 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 ofthe kind shown in Figure 2; Figure 4 is a perspective view of a body used in assembly apparatus ofthe kind shown in Figure 3; Figure 5is a schematic elevation of means for supporting trimming and bending devicesforuse 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 7is a plan view of the device shown in Figure 6; and Figure 8 is an end view, to a larger scale, ofthe device shown in Figure 6, as viewed from the left of Figure 6.

The spring band illustrated in Figure lisa spring band ofthe 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 ofthe coil springs lying near opposed edge faces of the band.

In this particularform of spring band, alternate springs are coils of one hand while the remaining spring are coils ofthe 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 ofwire also affords a plurality of connectors 2 that are integral with the coils 1. Each connectorliesatornearan edgefaceofthe 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.

Afterthe 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.

Aspring band ofthe kind described can be made by a spring-making machine of the kind described and illustrated in the complete specification ofthe aforementioned British patentspecification 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 partofthe intermediate portion to form a transversely extending partthat constitutes a supporting structure 5 of a kind that is the subject of British patent No. 143731. It is to be understood thatthe supports 5form no part of the present invention and may be omitted, if desired.

Spring bands ofthe kind illustrated in Figure 1 are assembled togetherto form a spring unit of the kind illustrated schematicaily 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 nearthe main planes ofthe unit, and a plurality of helical wires. Some ofthe helical wires 6A lie in or nearone main plane ofthe unit, while other helical wires 6B, lie in ornearthe other main plane thereof.

Each helical wire embraces component portions of each spring band, namelytwo adjacent end portions 3 oftwo neighbouring connectors.

Each ofthetwo marginal spring bands 7 and 8 of the unit is so orientated that its component connectors 2 lie at orcloseto the sides ofthe unit, whilethe remaining spring bands, 9, are all orientated in the same way as the marginal band 7.

As the connectors ofthe marginal bands 7 and 8 are at or close to the sides of the unittheyassistin strengthening the marginal parts ofthe 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 nearthe main planes of the unit. The frames serve to strengthen the marginal parts ofthe unitandare madefrom flexible and resilientstripmetal.

The spring bands can be assembled with the aid of assembly apparatus of the kind described and illustrated in the complete specification ofthe aforementioned British patent No. 1 095980. In accordancewiththepresentinvention, 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 pasta linking station 13atwhich locating means, in the form of pairs of jaws 10 and 11, engage end portions 3 ofthe connectors that are to be linked.At one side ofthe 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 linkthe end portionstogether.

The marginal band 8, which is orientated in a manner different from the bands 7 and 9, is adjacent tothe drive means 14. The advantage ofthat arrangement is that if it is desired to reset or adjust the apparatus to enable itto make spring units of a different width, more (or fewer) ofthe 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 madeforthe marginal band atthatsideoftheunitasthatmarginal 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 ofthe intermediate bands.

The helical wires 6 are preformed and precut to a length a little greaterthan the width ofthefinished spring unit. In orderto 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 atthat 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 alignedwith drive meansforone helical wire 6Aand the otheraligned with thedrive means forthe other helical wire 6B.

Each jaw, 17, comprises a block of metal with a planarfrontface 18, formed with a row of recesses 19. Each recess 19 is of part-spherical shape and has a circular mouth. The axes ofthe recesses are normal totheplanarface 1 8 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 mannerasthejaws described in the complete specification of British patent No. 1 522611 granted to Multilastic Limited. In use, when a pairofjaws 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 greaterthan that exerted by the preceding recess. In consequence the helical wire is rapidly broughtto a halt.

If it is desired to adjustthe apparatus to enable itto make a spring unit of a differentwidth, the standard jaws next the marginal band ofthe unit can be replaced byjaws 17.

Onejaw of each pair of jaws 17 carries a proximity switch 20 at that end thereof closerto 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 ofthe kind illustrated in Figure 4 are of a new form and can, of course, be used in 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 adjacentto 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 mannerthat during each cycle of operation the spring bands are moved forward to an extentsuch that the end portions ofthe 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 ofthe bands is effected byfingers (not shown) which form part ofthe 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 ofthe helical wires are guided past the devices, but when the band move backwards, as described above, the projecting ends enterthe mouths ofthe devices, those mouths opening downstream ofthe apparatus. After the projecting ends have entered the mouths, the devices are then operated to trim and bend the helical wires.

The location ofthe 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 rectangularframe 25 which stands downstream of the linking station. The top of the frame lies below the path ofthe linked spring bands issuing from the linking station. At that side of the apparatus adjacent to the marginal band 8, an uprightelement 26 of the frame is extended upwards and carries devices 21 and 22. Towards the other side ofthe apparatus is a carriage 27 with supporting rollers 28 resting on parallel horizontal elements 29 ofthe frame. The elements 29 constitute a track.An upwardly extending element 30 ofthe carriage carries devices 23 and 24. Each of the four devices is similarin 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 adjustthe apparatus to enable itto make spring units of a different width, the carriage can be released and moved alongtheframe 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 ofthe carriage by a horizontally projecting supporting rod (not shown). A lateral extension 32 of the plate carries a bracket 33 to which is pivoted at34 the cylinder 35 of a pneumatic piston-and-cylinder unit 36. The piston rod 37 of the unit 36 is pivoted at 38to 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 ofthe 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 and41.

A cam 44fixed 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 ofthe cylinder 51 of a second pneumatic piston-and-cylinder unit 52. The piston rod 53 ofthe unit 52 is connected to the rear sidle 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 frontside block55and a secondtool support60is secured to the first tool support by screws 61. Atool 62 is secured between the tool supports 58 and 60.

Alocating bar63 is mounted on top ofthe plate 31, an upper part ofthe bar projecting forwards above the level ofthe tool 48so as to definethe upper part of a mouth which opens downstream ofthe 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 ofthe main faces of the length of spring unit and which embracestheend portions oftwo connectors forming part ofthe marginal band 7, rises up overthe guide plate 64 and then drops again sothatthose linked end portions lie just in front of the locating bar 63. The subsequent slight rearward movement ofthe 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 at66 in Figures 6 and 8.A hemispherical locating boss 67 on the underside ofthe 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 ofthe firsttool support 58 to lie in front of the helical wire and thus to block its exit from beneath the locating bar 63. The rearupperedgeofthefirsttool 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 ofthe cam in turn causing rotation of the arm 46, but through a much smaller angle than that th rough which the arm 39 rotates. The provision ofthis 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 ofthe arm 46 causes the tool 48to deform what is now the lastturn or coil of the helical wire intothe shape of a closed loop or eye, a loop or eye which embraces or encircles a constituent wire ofthe marginal band 7.

This positively prevents the subsequent occurrence of any significant rotation ofthe helical wire relative tothebandstowhich 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 ofthe helical wires.

Afterthe 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 furtherforward movement of the linked bands the helical wire 66 is free to leave the device.

It will be appreciated that the guide plates ofthe upper devices 21 and 23 push the marginal bands downwards during forward movement ofthe linked bands. Although the upper devices 21 and 23 are offset longitudinally ofthe apparatusfromthe 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 ofthis compression atthe end oftheforward movement causes the helical wire that has just passed the upper guide plates to spring upwards into a position in front ofthe mouths ofthe upper devices.

Operation ofthe devices 21,23 and 24 occurs simultaneously, but a pneumatic timer device (not shown) causes a slight delay in the operation ofthe device 22. This ensures that by the time device 22 has completed its operation the otherthree devices have already completed their operations. A proximity switch or micro-switch (not shown) operated bythe 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 ofthe 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 (9)

1. Apparatus for use in making spring units ofthe kind comprising an assembly of spring bands and helical wires, each spring band comprising a length of wire bent so asto form a plurality of coil springs disposed side by side in a row, ends ofthe coil springs lying in or near opposed edge faces ofthe band, and a plurality of connectors integral with the springs, each such connector lying in or near an edge face ofthe 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 ofthe unit, and a plurality of helical wires, some lying in or near one of said main faces and others lying in or nearthe other of said main faces and each helical wire embracing component portions of each band, the apparatus comprising feed meansfor intermittentlyfeeding a plurality of the spring bands in a downstream direction pasta linking station, locating means at the linking station operative while the bands are stationary to engage the portions ofthe 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 linkthose portions of the bands together,the apparatus also including 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 leftthe locating means and has been carried downstream to thetrimming 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 operative to trim one end of a helical wire atthetrimming station and the other 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 thatthe 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 3further characterised in that one of said pair of trimming devices is adjustable along a track extending transversely of the apparatus atthe 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, additional tothe aforementioned or primary trimming devices, each of the secondarytrimming devices being in fixed relationship to an associated one ofthe 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 operativetotrim the ends of a helical wire in or near the other of the main faces ofthe spring unit.

6. Apparatus according to any one of claims 2 to 5 further characterised in that each trimming device 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 pastthetrimming 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 pastthe trimming device bythe 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 anyone of claims 2to 6furthercharacterised inthatthereisa 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.

8. Apparatus for use in making spring units ofthe kind specified and substantially as hereinbefore described with reference to Figures 3 and 5 ofthe accompanying drawings.

9. Apparatus according to claim 8 in which the trimming and bending devices are substantially as hereinbefore described with reference to Figures 6,7 and 8 ofthe accompanying drawings.