[0001] This invention relates to an apparatus for marking zip fasteners, and in particular
to a thermal transfer contact system for automatically marking zip fasteners.
[0002] Zip fasteners are commonly used for joining together two edges of material. They
may be used for providing a closable slit in a unit e.g. as in a dress zip, or they
may be used for joining two separate pieces of material together. They are widely
used in a upholstery, clothing etc., with almost any type of material. In many situations,
a zip fastener will be used to join together two edges of patterned material. A particular
example is the manufacture of car seat covers. In this situation, it is important
that the pattern on the two edges of material matches.
[0003] Matching two such patterns is an awkward process. A conventional zip fastener has
two stringers which are formed from a plurality of coupling elements located on an
edge of a tape. The edges of material to be joined are attached to the respective
tape and the zip fastener is closed by engaging the coupling elements with a slider.
In many situations, it is not practical to attach the material when the zip fastener
is closed. Therefore, the zip fastener stringers need to be marked so that the pattern
on the edges of the material can be matched with the corresponding position on the
stringers.
[0004] A past method of doing this has been to mark the tapes of the zip fastener stringers
manually, for example with a pen. However, this method has many disadvantages, in
addition to being extremely time consuming and costly. For example, during handling
of the stringers, the pen mark can rub off. Also, the tape must be marked on its upper
and lower surface. It is awkward to accurately align pen marks on both of these surfaces.
[0005] Another method has been to use alignment marks in the zip-fastener stringer tapes
consisting of pairs of open holes. The tape of each stringer has a hole at the same
positions along the length of the stringers, allowing accurate alignment from either
side. The holes are punched between the line of attachment of the material and the
coupling elements so that the strength of the zip fastener is not weakened. To prevent
fraying, the pins used to punch the holes are heated, sealing the walls of the hole.
This works well for a polyester type material, although for other materials, a more
complicated and more expensive sealing technique may be required. A major disadvantage
of the hole punching method is that it is time consuming and therefore expensive to
punch the holes. Except for particularly long zip fasteners, only a single alignment
hole is generally provided, about halfway along the length of the zip fastener.
[0006] The present invention overcomes these problems by providing an apparatus to create
alignment marks on both sides of a zip fastener stringer by printing, particularly
thermal transfer printing. Multiple alignment marks can easily be made along the length
of the stringers, so that the material can be matched at more than one point. This
is particularly important for long zip fasteners which are used in car seat manufacture.
The alignment marks may be regularly or irregularly spaced, which may be of use for
attaching to material with a more complex pattern or shape, for example. Multiple
types of markings may be used, and markings can be accurately aligned on the upper
and lower surfaces. Markings can be made using a choice of colours of ink, or using
more than one colour of ink. Lengths of chain which have been previously dyed in different
colours may be marked.
[0007] Thermal transfer contact systems provide a simple, economical and clean method of
printing on layers of fabric, and on many consumer items utilising brightly coloured
designs, such as ceramic mugs. However, none of these currently known machines are
suited to printing on zip fasteners. In order to automatically print markings on a
zip fastener, a printing machine must be able to take account of the width of the
zip fastener chain, and it must be able to automatically deal with both continuous
chain and gapped chain, taking account of the spacings between different lengths of
gapped chain. It must be able to print on both the front and the back surfaces of
zipper chains.
[0008] Thermal transfer printing technology is suitable for printing simple codes or marks
onto a flat surface such as plastic film, cases or textile tapes. It ensures good
and regular print quality. It is particularly suitable when the code to be printed
is short and does not change often. Due to the fact that thermal contact printers
use non solvent-based solid inks, ribbons or dry inks, this technology is environmentally
friendly.
[0009] The present invention provides a printing apparatus for a marking zip fastener stringer,
a stringer comprising a plurality of coupling elements located on an edge of a tape,
the printing apparatus comprising a printer for printing onto said tape; feeding means
for feeding said tape past the printer; measuring means for measuring distance along
of said tape; and control means coupled to said measuring means and to said printer,
wherein said control means controls the intervals along said tape at which said printer
prints onto said tape.
[0010] Preferable, two tapes are joined to form a chain, and the printing means is adapted
to print on both tapes of the chain. Preferably, the measuring means comprises a rotary
shaft encoder and the feeding means comprises a feed motor. Preferably, the printing
apparatus further comprises support means for supporting the chain, allowing gapped
chain to be fed through the system, end detector means such as a space detector, for
detecting the gap. Preferably, the printing apparatus has a second print head, and
the two print heads are positioned such that in use, one print head print onto a first
surface of the chain, and the second print head prints onto the reverse surface of
the chain. Preferably, the design of the mark to be printed can be manually changed,
and the shape of the print heads is adapted to allow printing to the stringers of
a zip fastener with a slider.
[0011] The invention will now be described by way of example with reference to the following
drawings, in which:-
Figure 1 shows several lengths of zip fastener chain, each with a different arrangement
of alignment markings;
Figure 2 shows a schematic diagram of a preferred embodiment of the invention;
Figure 3 shows a side view of a preferred embodiment of the invention, and
Figure 4 shows an expanded view of a print head
[0012] Figure 1 shows three separate lengths of zip fastener chain 150, 160, 170. Each zip
fastener chain has two stringers 103 and 105, and each stringer 103, 105 is made up
of a tape 107, 109 with a multiple of coupling elements 111, 113 on the edge of the
tape 107, 109. The elements may be discrete elements or formed by a continuous moulding
or helically wound filament as is well known in the art. Typically, a length of zip
fastener chain is made into a zip fastener by removing end fastening elements, replacing
them with stops, and adding a slider. For manufacturing purposes, two tapes are formed
and then joined to form a chain which can then be processed further, for example by
dyeing, and then shipping. Gaps may be formed in the elements along the chain to indicate
start and finish points of individual zip fasteners, for example by cutting away the
elements.
[0013] The zip fastener chains of figure 1 show three different possibilities for marking.
In the first chain 150, the stringers are symmetrically marked, with level sets of
markings 115 spaced at a pre-set interval. Markings are considered level when a line
between the markings on each stringer is substantially perpendicular to the direction
of closure of the zip fastener. In the second chain 160, an asymmetric marking pattern
is shown by markings 117 on stringer 103 being at a different spacing to markings
119 on stringer 105. In the third chain 170, markings 121 on the under side of stringer
105 are aligned with markings 123 on the upper side of stringer 103.
[0014] Figure 2 shows a schematic diagram of a preferred embodiment of the invention. Zip
fastener chain 200 is fed between two rollers 202, 204 of a rotary shaft encoder 206.
The rotary shaft encoder 206 sends a signal to a controller 208, indicating the length
of chain 200 which has passed through the rollers 202, 204. The chain 200 then passes
through two sets of print heads. A bottom print head 210 prints on the underside of
the chain, and a top print head 212 prints on the upper side of the chain 200. A feed
motor 214 provides the driving force via the rollers 216, 218 to pull the chain 200
through the system.
[0015] The distance between the print heads of the printers 210, 212 is known, and the distance
from the rotary encoder 206, and hence the respective printer is triggered by the
controller after a calculated length of chain has passed through the rotary encoder
206.
[0016] The top and bottom printers are controlled via two compact control units 220, 222.
Suitable control units would be Imaje: 1 Termopack 50 V S3 and 1 Termopack 50 H S3.
These are connected to the controller 208. A control panel is provided on the controller
208. Chain guides 230, 232 are used to guide the chain 200 through the system, and
into the correct position between the print heads. By changing the chain guides 230,
232, different sizes or widths of chain can be accommodated. The printer preferably
prints a line or other marking extending in from the outer edge of the tape 107, 109
and may be adjustable to print different lengths. An achievable print head marking
speed is 150 cycles per minute. Several ribbon colours are possible, and various types
of mark shape are possible. The tolerance of positioning of a mark of 1mm. Is possible.
[0017] The print head design may allow for the printer to be set to print on one or both
sides of the elements of the chain, that is on one or both tapes 107, 109 (Figure
1). Alternatively, two printers could be provided for printing on respective tapes
107, 109.
[0018] For continuous chain, the rotary encoder controls the marking by measuring the passage
of the chain. For gapped chain, the start point of the elements can be detected by
a space sensor 240 such as a photocell or a mechanical detector, and the controller
then triggers the printers 210, 212 at pre-determined distances from the start point.
The space sensor is preferably positioned downstream of the rotary encoder 206.
[0019] Figure 3 shows a sectional view of the printing machine. The chain is guided and
aligned through a tensioner 250 before entering the rotary shaft encoder 206.
[0020] By controlling the tension, any stretching of the chain 200 between the encoder 206
and the motor 214 can be controlled, to ensure accurate positioning of the markings.
[0021] Figure 4 shows the construction of one of the print heads. The print head is fitted
with rollers which guide an ink foil 141 below a hot press 143. The ink foil 141 enters
the print head via a first roller, and leaves via a second roller. The zip fastener
chain 100 is guided below the print head. An image 144 is transferred from the ink
foil to the chain 200, by the hot press 143 moving towards the chain, and pressing
the ink foil 144 against the chain 100.
[0022] It will be appreciated that other printer types, such as ink jet, might be used,
but a thermal printer has been found to be particularly suitable.
[0023] By appropriate programming of the controller 208, markings can also be printed on
the tapes 107, 109 at irregular intervals, such as 10cm, 20 cm, 45 cm from a start
point, to suit particular user requirements.
1. A printing apparatus for marking a zip fastener stringer, said stringer comprising
a plurality of coupling elements located on an edge of a tape,
the said printing apparatus comprising:
a printer for printing onto said tape;
feeding means for feeding said stringer past a print head of the printer;
measuring means for measuring the passage of said stringer past the print head and
providing an output; and
control means coupled to said measuring means and to said printer, wherein said control
means controls the intervals along said tape at which said printer prints onto said
chain according to the output from the measuring means.
2. A printing apparatus as claimed in claim 1, wherein the measuring means comprises
a rotary shaft encoder.
3. A printing apparatus as claimed in claim 1, wherein the feeding means comprises a
feed motor which pulls the tape through the encoder and past the print head.
4. A printing apparatus as claimed in any one of claims 1 to 3, wherein a pair of coupled
stringers, forming a chain, are to be fed through the apparatus.
5. A printing apparatus, as claimed in claim 4, further comprising end detector means
for detecting a gap in the elements along the chain.
6. A printing apparatus as claimed in claim 5, wherein the end detector means comprises
a space detector.
7. A printing apparatus, as claimed in any one of claims 1 to 6, further comprising a
second print head, the two print heads positioned such that in use, one print head
print onto a first surface of the stringer or chain, and the second print head prints
onto the reverse surface of the stringer or chain.
8. A printing apparatus, as claimed in any one of claims 1 to 7, wherein the design of
the mark to be printed can be changed.
9. A printing apparatus, as claimed in any one of claims 1 to 8, wherein printer is a
thermal printer.
10. A printing apparatus as claimed in claim 7, wherein the control means is programmable
to cause the respective print heads to print at different intervals along the tape.
11. A printing apparatus as claimed in claim 4, wherein the printer prints onto both tapes
of the chain, and the control means is adapted to control the printer to print on
the respective tapes at different intervals.