WO2002058930A1

WO2002058930A1 - Printing screen support, method of mounting a printing screen and assembly jig

Info

Publication number: WO2002058930A1
Application number: PCT/GB2002/000344
Authority: WO
Inventors: Richard Andre Piatek; Bernward Starke; Peter William Marshall
Original assignee: Dek International Gmbh
Priority date: 2001-01-25
Filing date: 2002-01-25
Publication date: 2002-08-01
Also published as: GB0101970D0; GB2371520B; GB2371520A; GB0201719D0; GB2371519A

Abstract

A printing screen support (101) for supporting a printing screen (102) under tension, the support comprising: a frame (104); a plurality of attachment elements (106) for attachment to a printing screen; and a plurality of resilient elements (108) connecting the attachment elements to the frame, the resilient elements being tensioned prior to attachment of the screen to the attachment elements.

Description

PRINTING SCREEN SUPPORT. METHOD OF MOUNTING A PRINTING SCREEN AND ASSEMBLY JIG

The present invention relates to a printing screen support for supporting a printing screen, often alternatively referred to as a printing stencil, for use in a screen printing machine, a method of mounting a printing screen, and an assembly jig for mounting a printing screen support to a printing screen.

A printing screen includes apertures which define the pattern to be printed, with the screen being located over an object to be printed and printing medium forced through the apertures to provide the required print.

Traditionally, printing screens have been formed of a woven fabric which is selectively impregnated with a resin to block the mesh of the fabric and define the apertures. For applications where the printing medium includes particles of a relatively large size, such as a solder paste as used in the electronics industry, and the mesh of the woven fabric is too fine to allow the transfer of such particles, printing screens are formed of a metal sheet, typically of a thickness of about 0.015 mm, in which the apertures are machined.

In order to produce high quality prints, printing screens have to be held under tension in screen printing machines. Woven fabric screens are usually tensioned by stretching the fabric over a rigid frame and bonding the same thereto. Metal screens do not, however, allow for such direct bonding to a rigid frame and alternative mounting arrangements have been proposed. In one such mounting arrangement, a woven fabric is first stretched to the required tension over a rigid frame and bonded thereto, and the periphery of a metal screen is bonded to the stretched fabric which is then removed in the operative region of the screen. Numerous other mounting arrangements have also been proposed which allow for the removable mounting of printing screens, with examples being disclosed in GB-A-2264460, GB-A-2291624, GB-A-2292115 and GB- A-2303333. These mounting arrangements generally comprise projections, which are located in apertures at opposing edges of the printing screen, by means of which the screen can be tensioned. In GB-A-2303333, the printing screen includes a plurality of slots along each of the edges thereof and the frame includes a tensioning bar along each of the edges thereof, which tensioning bars include a plurality of projections which engage in the slots in the screen and are biased outwardly by springs to tension the screen.

Whilst the above-described mounting arrangements do provide for the tensioning of metal screens, such mounting arrangements do suffer from a number of significant drawbacks. The mounting arrangements which utilise a woven fabric to mount a printing screen to a frame result in assemblies which are large and relatively expensive in terms of manufacture, handling and storage. The mounting arrangements which allow for the removable mounting of printing screens do overcome certain of these disadvantages, but suffer from other significant drawbacks. Notably, an unmounted printing screen is very thin and flexible, making handling hazardous and being prone to accidental damage. Also, the repeated removal and mounting of different printing screens increases the cost of use and also the likelihood of damage to the screens. In this regard, it has been found that printing screens are damaged to the point of being unusable by the repeated removal and mounting before any significant wear of the screens has occurred. In addition, the printing screens have to be configured specifically for each mounting arrangement, and thus those screens can only be used with a particular mounting arrangement. Moreover, the current trend in the miniaturisation of electronics components necessitates the use of even thinner printing screens and only exacerbates the above-mentioned problems.

It is thus an aim of the present invention to provide a printing screen support to which a printing screen can be permanently attached, and thereby provide a printing screen assembly which is robust, safe to handle, and inexpensive to manufacture, handle and store. It is a further aim of the present invention to provide an improved method of mounting a printing screen. It is a yet further aim of the present invention to provide an assembly jig for enabling the permanent attachment of a printing screen to such a printing screen support.

In one aspect the present invention provides a printing screen support for supporting a printing screen under tension, the support comprising: a frame; a plurality of attachment elements for attachment to a printing screen; and a plurality of tensionable resilient elements coupling the attachment elements to the frame, with the attachment elements being moved in a direction inwards of the frame on tensioning the resilient elements.

Preferably, at least one of the attachment elements is disposed inwardly of the frame.

More preferably, each of the attachment elements is disposed inwardly of the frame.

In one embodiment at least one of the resilient elements is disposed inwardly of the frame.

Preferably, each of the resilient elements is disposed inwardly of the frame.

In another embodiment at least one of the resilient elements is disposed within the confines of the frame.

Preferably, each of the resilient elements is disposed within the confines of the frame.

Preferably, the attachment elements are substantially co-planar with a lowermost surface of the frame.

Preferably, the resilient elements are substantially co-planar with a lowermost surface of the frame.

Preferably, the frame has a thickness of not more than about 40 mm.

More preferably, the frame has a thickness of not more than about 10 mm.

Preferably, the frame is of tubular section.

Preferably, the frame is of substantially rectangular section. Preferably, each of the attachment elements includes a flat surface for attachment to a printing screen.

More preferably, at least one of the attachment elements comprises a fiat sheet.

Yet more preferably, each of the attachment elements comprises a flat sheet.

Preferably, the attachment elements are separate elements.

Preferably, the attachment elements are substantially rigid elements.

In one embodiment at least one of the resilient elements comprises a concertina structure.

Preferably, each of the resilient elements comprises a concertina structure.

In another embodiment at least one of the resilient elements includes at least one resilient member which includes first and second sections which couple respective ones of the frame and the respective attachment element and define a space therebetween.

Preferably, each of the resilient elements includes at least one resilient member which includes first and second sections which couple respective ones of the frame and the respective attachment element and define a space therebetween.

In a further embodiment at least one of the resilient elements includes first and second opposed resilient members, each including first and second sections which couple respective ones of the frame and the respective attachment element and define a space therebetween.

Preferably, each of the resilient elements includes first and second opposed resilient members, each including first and second sections which couple respective ones of the frame and the respective attachment element and define a space therebetween.

Preferably, the or each resilient member comprises a looped member.

More preferably, the or each resilient member comprises a substantially U-shaped or V- shaped member.

Preferably, at least ones of the resilient elements include an engagement aperture for engaging an engagement member of a tensioning jig.

Preferably, each respective attachment element and the at least one resilient element connected thereto are formed from a single sheet.

More preferably, the sheet is a metal sheet.

Preferably, the frame comprises a plurality of connected frame elements.

In one embodiment the frame comprises a plurality of frame elements having welded connections.

In another embodiment the frame comprises a plurality of frame elements and a plurality of connecting pieces connecting the same.

In one embodiment at least part of each frame element and the at least one attachment element and the at least one resilient element connected thereto are formed from a single sheet.

Preferably, each respective frame element and the at least one attachment element and the at least one resilient element connected thereto are formed from a single sheet.

More preferably, the sheet is a metal sheet. In another embodiment the frame elements comprise extruded sections.

Preferably, at least one of the attachment elements and the at least one resilient element connected thereto are substantially planar.

More preferably, each respective attachment element and the at least one resilient element connected thereto are substantially planar.

In one embodiment each attachment element is coupled to the frame by a single resilient element.

In another embodiment each attachment element is coupled to the frame by a plurality of resilient elements.

Preferably, the support further comprises: a plurality of engagement elements coupling respective ones of the resilient elements to the frame.

In one embodiment the support comprises: a plurality of connection elements each comprising an engagement element, at least one attachment element and at least one resilient element.

Preferably, the connection elements are detachably coupled to the frame.

Preferably, the frame includes at least one slot in a lower surface thereof and the connection elements each include at least one projection for engagement in the at least one slot.

Preferably, the frame includes a recess in a lower surface thereof accommodating the connection elements.

In one embodiment the frame is of rectangular shape. Preferably, the frame has at least one edge of narrower width than the other edges thereof.

Preferably, each pair of opposing edges of the frame has a different width.

In another aspect the present invention provides a printing screen support for supporting a printing screen under tension, the support comprising: a frame; a plurality of attachment elements for attachment to a printing screen, the attachment elements being disposed inwardly of the frame; and a plurality of resilient elements connecting the attachment elements to the frame, the resilient elements being tensionable to a predeterminable tension.

In a further aspect the present invention provides a printing screen support for supporting a printing screen under tension, the support comprising: a frame; a plurality of attachment elements for attachment to a printing screen; and a plurality of resilient elements connecting the attachment elements to the frame; wherein each respective attachment element and the at least one resilient element connected thereto are formed from a single sheet.

The present invention also extends to a printing screen assembly comprising the above- described printing screen support in combination with a printing screen attached to the attachment elements of the support.

In one embodiment ones of the resilient elements are tensioned to different tensions.

Preferably, the printing screen is rectangular in shape and the resilient elements are tensioned such that an increased tension is applied at each comer of the screen.

More preferably, the resilient elements are tensioned such that the tension increases progressively from a mid-point to the respective adjacent corners of each edge of the screen. The printing screen support of the present invention is particularly advantageous in allowing for the attachment of almost any printing screen thereto. Indeed, the printing screen support of the present invention is such as to allow the attachment of existing printing screens thereto which are so damaged as not to allow attachment to the mounting arrangement for which the screens were originally designed. Most existing printing screens would simply need to be trimmed to size.

In a yet further aspect the present invention provides a method of mounting a printing screen to a printing screen support, the method comprising the steps of: providing a printing screen support comprising a frame, a plurality of attachment elements for attachment to a printing screen, and a plurality of tensionable resilient elements coupling the attachment elements to the frame; tensioning the resilient elements; and attaching a printing screen to the attachment elements.

Preferably, the attachment elements are moved in a direction inwards of the frame on tensioning the resilient elements.

Preferably, the step of tensioning the resilient elements comprises the step of: tensioning ones of the resilient elements to different tensions.

More preferably, the printing screen is rectangular in shape, and the step of tensioning the resilient elements comprises the step of: tensioning the resilient elements such that an increased tension is applied at each corner of the screen.

Yet more preferably, the resilient elements are tensioned such that the tension increases progressively from a mid-point to the respective adjacent corners of each edge of the screen.

Preferably, the step of attaching the screen to the attachment elements comprises the step of: welding the screen to the attachment elements.

In a still further aspect the present invention provides an assembly jig for mounting a printing screen to a printing screen support comprising a frame, a plurality of attachment elements for attachment to the screen and a plurality of tensionable resilient elements coupling the attachment elements to the frame, the assembly jig comprising: a support unit for supporting the screen and the support; first and second sets of engagement members for engaging opposed attachment elements or resilient elements coupled thereto of the support; and a tensioning mechanism for relatively moving the engagement members of the first and second sets of engagement members towards one another to extend the resilient elements coupled to the opposed attachment elements and tension the same.

Preferably, the jig further comprises: third and fourth sets of engagement members for engaging further opposed attachment elements or resilient elements coupled thereto of the support extending substantially orthogonally to the first-mentioned opposed attachment elements of the support; and wherein the tensioning mechanism is configured to move the engagement members of the third and fourth sets of engagement members relatively towards one another to extend the resilient elements coupled to the further opposed attachment elements and tension the same.

In one embodiment the tensioning mechanism is configured to move the engagement members of at least one of the sets of engagement members in unison.

In another embodiment the tensioning mechanism is configured to move groups of ones of the engagement members of at least one of the sets of engagement members in unison.

In a further embodiment the tensioning mechanism is configured to move ones of the engagement members of at least one of the sets of engagement members individually.

In one preferred embodiment the tensioning mechanism is configured to move the engagement members of each of the respective sets of engagement members in unison.

In another preferred embodiment the tensioning mechanism is configured to move groups of ones of the engagement members of each of the respective sets of engagement members in unison.

In a further preferred embodiment the tensioning mechanism is configured to move ones of the engagement members of each of the respective sets of engagement members individually.

Preferably, the tensioning mechamsm is configured such that ones of the resilient elements are tensioned to different tensions.

In one embodiment the tensioning mechanism is configured such that the resilient elements are tensioned such that an increased tension is applied at each corner of a rectangular printing screen.

Preferably, the tensioning mechanism is configured such that the resilient elements are tensioned such that the tension increases progressively from a mid-point to the respective adjacent corners of each edge of the screen.

In one embodiment the tensioning mechanism is configured such that groups of ones of the engagement members of at least one of the sets of engagement members are moved in different orients relative to a reference direction.

Preferably, the tensioning mechamsm is configured such that groups of ones of the engagement members of each of the respective sets of engagement members are moved in different orients relative to respective reference directions.

Preferably, the groups comprise respective halves of the engagement members of any set of engagement members.

In another embodiment the tensioning mechanism is configured such that ones of the engagement members of at least one of the sets of engagement members are moved in different orients relative to a reference direction. Preferably, the tensioning mechanism is configured such that ones of the engagement members of each of the respective sets of engagement members are moved in different orients relative to respective reference directions.

Preferably, the orients extend through a substantially common point.

Preferably, the jig further comprises: an attachment unit for attaching the screen to the attachment elements of the support.

More preferably, the attachment unit comprises a welding unit for welding the screen to the attachment elements of the support.

Preferred embodiments of the present invention will now be described hereinbelow by way of example only with reference to the accompanying drawings, in which:

Figure 1 illustrates a perspective view from above of a printing screen support for supporting a printing screen in accordance with a first embodiment of the present invention;

Figure 2 illustrates in enlarged scale a fragmentary perspective view from above of one corner (region A in Figure 1) of the support of Figure 1;

Figure 3 illustrates a fragmentary vertical sectional view of the support of Figure 1;

Figure 4 illustrates a perspective view from above of a printing screen support for supporting a printing screen in accordance with a second embodiment of the present invention;

Figure 5 illustrates in enlarged scale a fragmentary perspective view from above of one corner (region B in Figure 4) of the support of Figure 4; Figure 6 illustrates a fragmentary vertical sectional view of the support of Figure 4;

Figure 7 illustrates a perspective view from above of a printing screen support for supporting a printing screen in accordance with a third embodiment of the present invention;

Figure 8 illustrates a perspective view from below of the support of Figure 7;

Figure 9 illustrates in enlarged scale a fragmentary perspective view from above of one corner (region C in Figure 7) of the support of Figure 7;

Figure 10 illustrates in enlarged scale a fragmentary perspective view from below of another corner (region D in Figure 8) of the support of Figure 7;

Figure 11 illustrates a fragmentary vertical sectional view of the support of Figure 7;

Figure 12 illustrates a perspective view from above of a printing screen support for supporting a printing screen in accordance with a fourth embodiment of the present invention;

Figure 13 illustrates a perspective view from below of the support of Figure 12;

Figure 14 illustrates in enlarged scale a fragmentary perspective view from above of one corner (region E in Figure 12) of the support of Figure 12;

Figure 15 illustrates in enlarged scale a fragmentary perspective view from below of another corner (region F in Figure 13) of the support of Figure 12;

Figure 16A illustrates a first fragmentary vertical sectional view of the support of Figure 12;

Figure 16B illustrates a second fragmentary vertical sectional view of the support of Figure 12;

Figure 17 illusfrates a perspective view from above of an assembly jig in accordance with a first embodiment of the present invention;

Figure 18 illustrates a perspective view from below of the assembly jig of Figure 17;

Figure 19 illustrates a perspective view from above of the assembly jig of Figure 17 having a printing screen located thereon;

Figure 20 illusfrates a perspective view from above of the assembly jig of Figure 17 having a printing screen and the printing screen support of Figure 1 located thereon;

Figure 21 illustrates a perspective view from above of an assembly jig in accordance with a second embodiment of the present invention;

Figure 22 illustrates a perspective view from above of the assembly jig of Figure 21, with the table assembly removed;

Figure 23 illustrates a perspective view from below of the table assembly of the assembly jig of Figure 21;

Figure 24 illustrates a perspective view from above of the assembly jig of Figure 21 having the printing screen support of Figure 12 located thereon; and

Figure 25 illusfrates a perspective view from above of the assembly jig of Figure 21 having the printing screen support of Figure 12 and a printing screen located thereon.

Figures 1 to 3 illustrate a printing screen support 100 in accordance with a first embodiment of the present invention.

The support 100 comprises first, second, third and fourth support members lOla-d for attachment to respective edges of a printing screen 102.

The support members lOla-d each comprise a frame element 104a-d, which frame elements 104a-d are joined together at the respective ends thereof, in this embodiment by butt welding, and define a rigid frame, an attachment element 106a-d for attachment to a respective edge of the screen 102, in this embodiment by spot welding, and a resilient element 108a-d connecting the frame element 104a-d and the attachment element 106a-d. The support members lOla-d are each fabricated from two metal sheets, in this embodiment stainless steel sheets of 0.5 mm in thickness, one sheet defining one part of the frame element 104a-d, the attachment element 106a-d and the resilient element 108a-d, and the other sheet defining the other part of the frame element 104a-d. In an alternative embodiment the support members lOla-d could be fabricated from nickel-plated mild steel.

The frame elements 104a-d each comprise a box section, in this embodiment a rectangular box section of a thickness T of 8 mm, which has an outwardly-directed peripheral flange. In other embodiments the frame elements 104a-d could take any form which provides the necessary rigidity, for example, flat plates.

The attachment elements 106a-d are each attached, in this embodiment by spot welding, to a respective edge of the screen 102 and include apertures 1 lOa-d for engagement with a tensioning jig to enable pre-tensioning of the resilient elements 108a-d prior to attachment to the screen 102, as will be described in more detail hereinbelow. As illustrated in Figure 2, the distal ends of the attachment elements 106a-d are spaced to allow for movement of the same in tensioning the resilient elements 108a-d. In this embodiment the attachment elements 106a-d comprise flat sections, but, in other embodiments, could take any form. Also, in other embodiments, the attachment elements 106a-d could be attached to the screen 102 by any means, for example, an adhesive, which would be particularly suitable for non-metallic screens.

In this embodiment the resilient elements 108a-d each comprise a concertina structure which is formed from a single metal sheet. In this embodiment the width W of each corrugation is 6.9 mm, with each adjacent fold enclosing an angle α of 35°. With this configuration, the resilient elements 108a-d can be integrally formed with the respective frame elements 104a-d and attachment elements 106a-d.

Figures 4 to 6 illustrate a printing screen support 200 in accordance with a second embodiment of the present invention.

The support 200 comprises first, second, third and fourth support members 201a-d for attachment to respective edges of a printing screen 202, and first, second, third and fourth corner pieces 203a-d connecting the respective ends of the support members 201a-d.

The support members 201a-d each comprise a frame element 204a-d, which frame elements 204a-d are connected to the respective corner pieces 203 a-d, in this embodiment by butt welding, such as to define a rigid frame, an attachment element 206a-d for attachment to a respective edge of the screen 202, in this embodiment by spot welding, and a plurality of resilient elements 208a-d connecting the frame element 204a- d and the attachment element 206a-d. In this embodiment the attachment element 206a- d and the resilient elements 208a-d of each support member 201 a-d are disposed inwardly of the frame element 204a-d thereof. The support members 201 a-d are each fabricated from a single metal sheet, in this embodiment stainless steel sheet of 1 mm in thickness. In an alternative embodiment the support members 201 a-d could be fabricated from nickel-plated mild steel.

The frame elements 204a-d each comprise a box section, in this embodiment a rectangular box section of a thickness T of 8 mm, and the comer pieces 203 a-d are solid pieces which are slotted into the ends of the frame elements 204a-d. In other embodiments the frame elements 204a-d could take any form which provides the necessary rigidity, for example, flat plates.

The attachment elements 206a-d are each attached, in this embodiment by spot welding, to a respective edge of the screen 202. As illustrated in Figure 5, the distal ends of the attachment elements 206a-d are spaced to allow for movement of the same in tensioning the resilient elements 208a-d. In this embodiment the attachment elements 206a-d comprise flat sections, but, in other embodiments, could take any form. Also, in other embodiments, the attachment elements 206a-d could be attached to the screen 202 by any means, for example, an adhesive, which would be particularly suitable for non- metallic screens.

In this embodiment the resilient elements 208a-d each include first and second opposed members 212, 213, here looped members, which each include first and second sections 212a, 213a, 212b, 213b which extend from respective ones of the respective frame element 204a-d and the respective attachment element 206a-d and define a space 214, 216 therebetween. In this embodiment the resilient elements 208a-d are also configured to define engagement apertures 218 therewithin for engagement with a tensioning jig to enable pre-tensioning of the resilient elements 208a-d prior to attachment to the screen 202, as will be described in more detail hereinbelow. With this configuration, the resilient elements 208a-d can be integrally formed with the respective frame elements 204a-d and attachment elements 206a-d from a single sheet, with the resilient elements 208a-d being formed, for example, by stamping or laser cutting.

Figures 7 to 11 illustrate a printing screen support 300 in accordance with a third embodiment of the present invention.

The support 300 comprises first, second, third and fourth support members 301a-d for attachment to respective edges of a printing screen 302, and first, second, third and fourth corner pieces 303a-d connecting the respective ends of the support members 301a-d.

The support members 301a-d each comprise a frame element 304a-d, which frame elements 304a-d are connected to the respective corner pieces 303a-d, in this embodiment by butt welding, such as to define a rigid frame, an attachment element 306a-d for attachment to a respective edge of the screen 302, in this embodiment by spot welding, and a plurality of resilient elements 308a-d connecting the frame element 304a- d and the attachment element 306a-d. In this embodiment the attachment element 306a- d of each support member 301 a-d is disposed inwardly of the frame element 304a-d thereof and the resilient elements 308a-d of each support member 301a-d are disposed within the confines of the frame element 304a-d thereof, in this embodiment at the lower surface of the frame element 304a-d thereof. In this embodiment the frame elements 304a-d each include a plurality of first apertures 309 in the upper and lower surfaces thereof for providing access to the resilient elements 308a-d, in particular the engagement apertures 318 thereof, as will be described in more detail hereinbelow, and a plurality of second apertures 310 in the upper surface thereof for providing access internally of the frame elements 304a-d in welding the same. With this configuration, the lateral dimension of the support members 301 a-d is reduced as compared to configurations where the resilient elements 308a-d are disposed inwardly of the frame elements 304a-d, such that the lateral dimension of a mounted screen 302 is reduced. The support members 301 a-d are each fabricated from a single metal sheet, in this embodiment stainless steel sheet of 1 mm in thickness. In an alternative embodiment the support members 301a-d could be fabricated from nickel-plated mild steel.

The frame elements 304a-d each comprise a box section, in this embodiment a rectangular box section of a thickness T of 8 mm, and the comer pieces 303 a-d are solid pieces which are slotted into the ends of the frame elements 304a-d. In other embodiments the frame elements 304a-d could take any form which provides the necessary rigidity, for example, flat plates. In this embodiment the frame elements 304a-d each include an internal projection 311a-d at the lower surface thereof which is of the same height as the thickness of the folded sheet from which the frame elements 304a-d are fabricated, such that the comer pieces 303a-d are a tight fit within the frame elements 304a-d and allow readily for welding.

The attachment elements 306a-d are each attached, in this embodiment by spot welding, to a respective edge of the screen 302. As illustrated in Figures 9 and 10, the distal ends of the attachment elements 306a-d are spaced to allow for movement of the same in tensioning the resilient elements 308a-d. In this embodiment the attachment elements 306a-d comprise flat sections, but, in other embodiments, could take any form. Also, in other embodiments, the attachment elements 306a-d could be attached to the screen 302 by any means, for example, an adhesive, which would be particularly suitable for non- metallic screens.

In this embodiment the resilient elements 308a-d each include first and second opposed members 312, 313, here looped members, which each include first and second sections 312a, 313a, 312b, 313b which extend from respective ones of the respective frame element 304a-d and the respective attachment element 306a-d and define a space 314, 316 therebetween. In this embodiment the resilient elements 308a-d are also configured to define engagement apertures 318 therewithin for engagement with a tensioning jig to enable pre-tensioning of the resilient elements 308a-d prior to attachment to the screen 302, as will be described in more detail hereinbelow. With this configuration, the resilient elements 308a-d can be integrally formed with the respective frame element 304a-d and attachment element 306a-d from a single sheet, with the resilient elements 308a-d being formed, for example, by stamping or laser cutting.

Figures 12 to 16 illustrate a printing screen support 400 in accordance with a fourth embodiment of the present invention.

The support 400 comprises first, second, third and fourth support members 401 a-d for attachment to respective edges of a printing screen 402.

The support members 401 a-d each comprise a frame element 404a-d, which frame elements 404a-d are joined together at the respective ends thereof, in this embodiment by butt welding, and define a rigid frame, and a connection element 405a-d for attachment to a respective edge of the screen 402 and connecting the respective edge of the screen 402 to the frame element 404a-d.

The frame elements 404a-d each comprise a box section, in this embodiment an extruded, substantially rectangular box section of a thickness T of 8 mm. The frame elements 404a-d each have a stepped lower surface 406a-d, the lower surface 406a-d including a first, mounting surface 407a-d for providing for mounting to printing machines and a second, connection surface 408a-d which is spaced from the mounting surface 407a-d by a height corresponding to the thickness of the connection elements 405a-d for accommodating the respective connection element 405a-d, as will be described in more detail hereinbelow. The frame elements 404a-d each include a slot 409a-d in the lower surface 406a-d thereof, in this embodiment an elongate slot at the junction of the mounting surface 407a-d and the connection surface 408a-d, which is inwardly directed and defines an outwardly-directed projection 410a-d for engaging the respective connection element 405a-d, as will be described in more detail hereinbelow. The frame elements 404a-d each further include a recess 411a-d in the connection surface 408a-d of the lower surface 406a-d, the purpose of which will become apparent hereinbelow.

The connection elements 405a-d each comprise an engagement element 412a-d, in this embodiment including an upwardly and inwardly-directed projection 413a-d, for engagement with the outwardly-directed projection 410a-d at the lower surface 406a-d of the respective one of the frame elements 404a-d, an attachment element 414a-d for attachment to a respective edge of the screen 402, in this embodiment by spot welding, and a plurality of resilient elements 418a-d connecting the engagement element 412a-d and the attachment element 414a-d. In this embodiment the attachment elements 414a-d of the connection elements 405a-d are disposed inwardly of the respective frame elements 404a-d and the resilient elements 418a-d of the connection elements 405a-d are disposed within the confines of the respective frame elements 404a-d, in this embodiment at the lower surface 406a-d of the respective frame elements 404a-d. With this configuration, the lateral dimension of the support members 401 a-d is reduced as compared to configurations where the resilient elements 418a-d are disposed inwardly of the frame elements 404a-d, such that the lateral dimension of a mounted screen 402 is reduced.

The attachment elements 414a-d are each attached, in this embodiment by spot welding, to a respective edge of the screen 402. As illustrated in Figures 14 and 15, the distal ends of the attachment elements 414a-d are spaced to allow for movement of the same in tensioning the resilient elements 418a-d. In this embodiment the attachment elements 414a-d comprise flat sections, but, in other embodiments, could take any form. Also, in other embodiments, the attachment elements 414a-d could be attached to the screen 402 by any means, for example, an adhesive, which would be particularly suitable for non- metallic screens.

In this embodiment the resilient elements 418a-d each include first and second opposed members 420, 422, here looped members, which each include first and second sections 420a, 422a, 420b, 422b which extend from respective ones of the engagement element 412a-d of the respective connection element 405a-d and the attachment element 414a-d of the respective connection element 405a-d and define a space 424, 426 therebetween. In this embodiment the resilient elements 418a-d are also configured to define engagement apertures 428 merewithin for engagement with a tensioning jig to enable pre-tensioning of the resilient elements 418a-d prior to attachment to the screen 402, as will be described in more detail hereinbelow. In this embodiment the engagement apertures 428 are in alignment with the recesses 41 la-d in the respective frame elements 404a-d, such as to facilitate engagement with the tensioning jig. With this configuration, the resilient elements 418a-d can be integrally formed with the respective engagement element 412a-d and attachment element 414a-d from a single sheet, with the resilient elements 418a-d being formed, for example, by stamping or laser cutting. In this embodiment the connection elements 405a-d are each fabricated from a single metal sheet, here stainless steel sheet of 1 mm in thickness. In an alternative embodiment the connection elements 405a-d could be fabricated from nickel-plated mild steel.

Figures 17 and 18 illustrate an assembly jig 500 in accordance with a first embodiment of the present invention. For the purposes of exemplification, the assembly jig 500 will be described hereinbelow with reference to the printing screen support 100 of the above- described first embodiment.

The assembly jig 500 comprises a support member 502, in this embodiment a thick metal plate of rectangular shape, on which a printing screen 102 and a printing screen support 100 are locatable to enable the tensioning of the resilient elements 108a-d of the support 100 and the attachment, in this embodiment by spot welding, of the support 100 to the screen 102. The support member 502 includes a plurality of clips 504 about the periphery thereof for holding the support 100 thereto. The support member 502 further includes a plurality of first apertures 506a-d along each of the edges thereof, which apertures 506a-d, as will be described in more detail hereinbelow, allow for the welding of the support 100 to the screen 102. The support member 502 further includes a plurality of fixed pins 510a, b, which extend from the upper surface thereof, along each of first and second adjacent edges thereof. The support member 502 further includes a plurality of second apertures 511a, b along each of the other, third and fourth edges thereof.

The assembly jig 500 further comprises first and second tensioning assemblies 512a, b for tensioning the resilient elements 108a-d of the support 100.

The tensioning assemblies 512a, b each comprise a slide 514a, b which is slideably disposed to the lower surface of the support member 502 adjacent a respective one of the third and fourth edges thereof. The slides 514a, b each include a plurality of pins 515a, b which extend through respective ones of the plurality of second apertures 511a, b along the third and fourth edges of the support member 502 and from the upper surface of the support member 502 in parallel relation to respective ones of the plurality of pins 510a, b along the first and second edges of the support member 502. The slides 514a, b each further include a plurality of apertures 516a, b which are in registration with the plurality of first apertures 506c, d along the third and fourth edges of the support member 502 and allow for the attachment, in this embodiment by spot welding, of the support 100 to the screen 102.

The tensioning assemblies 512a, b each further comprise an actuator 517a, b, in this embodiment a pneumatically-operated actuator, which is coupled to the respective slide 514a, b by a lever 518a, b and operable to cause the inward sliding of the respective slide 514a, b and the tensioning of the resilient elements 108a-d of the support 100.

In another embodiment the plurality of pins 515a, b on each of the slides 514a, b could be individually movable to allow for the precise tensioning of the resilient elements 108a-d of the support 100.

In yet another embodiment the plurality of pins 510a, b fixed along each of the first and second edges of the support member 502 could instead be provided on third and fourth tensioning assemblies in the same manner as the plurality of pins 515a, b on each of the first and second tensioning assemblies 512a, b. With this construction, the sets of pins 510a, b, 515a, b engaging each of the edges of the screen 102 would be separately movable. Also, in a still further embodiment the pins 510a, b, 515a, b of each of the sets of pins 510a, b, 515a, b could be individually movable as mentioned hereinabove.

Operation of the assembly jig 500 will now be described hereinbelow with reference to Figures 19 and 20.

As illustrated in Figure 19, a printing screen 102 is first located on the support member 502 within the upstanding pins 510a, b, 515a, b. As illustrated in Figure 20, a printing screen support 100 is then located on the support member 502, with the upstanding pins 510a, b, 515a, b being located in the apertures HOa-d in the respective attachment elements 106a-d of the support 100 and the frame elements 104a-d of the support 100 being held in place by the clips 504. Here, it should be understood that the clips 504 allow for sliding movement of the support 100 relative to the screen 102, such that each of the resilient elements 108a-d of the support 100 is tensioned to the same extent. The actuators 517a, b of the tensioning assemblies 512a, b are then operated to cause the slides 514a, b to be slid inwardly and the resilient elements 108a-d of the support 100 to be extended. In this embodiment the actuators 517a, b are actuated by a predetermined pressure such that the extension of the resilient elements 108a-d corresponds to a predetermined tension to which the screen 102 is to be tensioned. Once so extended, the support 100 is then attached, in this embodiment by welding, to the screen 102, such that the screen 102 is under a predetermined tension. In this embodiment the edges of the screen 102 are welded, here spot welded, to respective attachment elements 106a-d of the support 100. Figures 21 to 23 illustrate an assembly jig 600 in accordance with a second embodiment of the present invention. For the purposes of exemplification, the assembly jig 600 will be described hereinbelow with reference to the printing screen support 300 of the above- described third embodiment.

The assembly jig 600 comprises a table assembly 602 on which a printing screen support 300 and a printing screen 302 are locatable to enable the tensioning of the resilient elements 308a-d of the support 300 and the attachment, in this embodiment by spot welding, of the support 300 to the screen 302, a support assembly 604 to which the table assembly 602 is mounted, in this embodiment rotatably mounted, and a welding assembly 605 for welding the screen 302 to the support 300.

The table assembly 602 comprises a table 606, in this embodiment a substantially rectangular table, for supporting the support 300 and the screen 302, and first, second, third and fourth tensioning assemblies 608a-d which are disposed to the respective edges of the table 606 for tensioning the resilient elements 308a-d of the support 300.

The table 606 comprises a support member 609, in this embodiment a thick metal plate, which includes a planar support surface 610 on which the support 300 is supported, in this embodiment in an inverted orient, and a seat 611, in this embodiment a rectangular plate, which is disposed on the support member 609 such as to present an upper surface which is spaced from the support surface 610 of the support member 609 such as to support the attachment elements 306a-d of the support 300 and the screen 302, whereby pressure can be applied to the attachment elements 306a-d in welding the screen 302 thereto. The support member 609 includes a plurality of clamps 612, in this embodiment turnbuckle clamps, about each of the edges thereof for holding the support 300 to the support member 609. The support member 609 includes a plurality of first apertures 613a-d which are disposed along each of the edges thereof adjacent the edges of the seat 611, which apertures 613a-d are in registration with the resilient elements 308a-d of the support 300 when supported on the support member 609, in particular the engagement apertures 318 within the resilient elements 308a-d, a plurality of second apertures 614a-d, in this embodiment arcuate through slots, which are disposed along each of the edges thereof adjacent and outwardly of the first apertures 613a-d, and a plurality of third apertures 615a-d, in this embodiment arcuate through slots, which are disposed along each of the outer edges thereof, which second and third apertures 614a-d, 615a-d, as will be described in more detail hereinbelow, allow for the configuration of the tensioning assemblies 608a-d in orients inclined to the respective edges of the screen 302.

The tensioning assemblies 608a-d each comprise a plurality of actuator units 616a-d which are operable to tension the resilient elements 308a-d of the support 300. In this embodiment the tensioning assemblies 608a-d each comprise first and second sets of actuator units 618a-d, 620a-d which are configured to tension the resilient elements 308a-d in each of the respective halves along each of the respective edges of the screen 302.

The actuator units 616a-d each comprise an actuator 622a-d, in this embodiment a pneumatically-operated actuator, a mounting block 624a-d by which the actuator unit 616a-d is pivotally mounted to the support member 609, a pin 626a-d which extends through a respective one of the first apertures 613a-d in the support member 609 such as to engage a respective one of the resilient elements 308a-d of the respective support members 301 a-d of the support 300 when supported on the support member 609, and is coupled to the actuator 622a-d such as to be slid inwardly and tension the respective attachment element 306a-d of me support 300 on actuation of the actuator 622a-d, and a fixing element 628a-d for fixing the orient of the actuator unit 616a-d relative to the respective edge of the screen 302.

With this configuration, an increased tension can be applied at each of the comers of the screen 302 where substantially the same tensioning force is applied by each of the actuator units 616a-d, in this embodiment by applying the same pneumatic pressure to each of the actuator units 616a-d. It has been determined that a rectangular screen 302 is optimally tensioned where the tension at the comers of the screen 302 is greater than at the centres of the edges of the screen 302, and in particular where the tension increases progressively from the mid points of the edges of the screen 302 to the respective adjacent comers of the screen 302. In alternative embodiments a tension which increases progressively to the comers of the screen 302 could be achieved by configuring the actuator units 616a-d to apply different tensioning forces which increase towards the comers, typically by applying a different pneumatic pressure to each of the actuator units 616a-d where the actuator units 616a-d are pneumatic units, or varying the spacing of the actuator units 616a-d, such that the actuator units 616a-d are progressively more closely spaced towards the comers of the screen 302, where the actuator units 616a-d apply substantially the same tensioning force.

The table assembly 602 further comprises a plurality of, in this embodiment four equi- spaced, supporting legs 632 for supporting, in this embodiment rotatably supporting, the table assembly 602 on the platform assembly 604, which legs 632 are attached to and depend downwardly from the support member 609. In this embodiment the legs 632 each include a resiliently-biased bearing 634 at the lower end thereof, which bearings 634 act to provide for free rotation of the table assembly 602 between stop positions and engage in complementary recesses 640 in a track 638 in a platform 636 of the support assembly 604 such as to define four stop positions for the table assembly 602, as will be described in more detail hereinbelow.

The support assembly 604 comprises a platform 636, in this embodiment a thick metal plate, which includes a circular track 638 in an upper surface thereof in which the legs 632 of the table assembly 602 are located such as to provide for rotation of the table assembly 602 about a rotation axis. In this embodiment the track 638 includes a plurality of, in this embodiment four, equi-spaced recesses 640 in which the bearings 634 on the legs 632 of the table assembly 602 are locatable to define stop positions, in this embodiment four stop positions, for the table assembly 602.

The welding assembly 605 comprises a welding unit 642 for welding the edges of a screen 302 to the tensioned attachment elements 306a-d of a support 300, and a positioning unit 644 for positioning the welding unit 642 at a plurality of positions relative to the table assembly 602 such as to allow for welding along each of the edges of the screen 302. In this embodiment the welding unit 642 comprises a welding head 646 which includes a pair of juxtaposed welding electrodes 648, which electrode configuration allows for welding of a screen 302 to the tensioned attachment elements 306a-d of a support 300 from a single direction.

In this embodiment the positioning unit 644 is disposed to one side of the support assembly 604 and is such as to provide for the welding of each edge of a screen 302 in turn to a support 300. The positioning unit 644 comprises a manually-operated, single- axis positioning table which comprises a pair of parallel guide rails 650, a table 652 which is slideably mounted on the guide rails 650, and a drive mechanism 654, in this embodiment comprising a rotatable handle and a threaded rod coupling the handle to the table 652, for moving the table 652 on the guide rails 650, and hence the welding unit 642 relative to the support 300 and the screen 302. In an alternative embodiment the drive mechanism 654 could be electrically-operated such as to allow for automated welding of one edge of the screen 302 to an attachment element 306a-d of the support 300. Also, in another embodiment, the table assembly 602 could be motorised, such as to allow for automated rotation of the table assembly 602, and hence possibly a fully- automated welding system.

Operation of the assembly jig 600 will now be described hereinbelow with reference to Figures 24 and 25.

As illustrated in Figure 24, a printing screen support 300 is first located in an inverted orient on the support member 609 of the table 606 such that the frame elements 304a-d of the support 300 are adjacent the respective edges of the seat 611 of the table 606 and the attachment elements 306a-d of the support 300 are disposed on the respective edges of the seat 611 of the table 606. In this position, the pins 626a-d of the actuator units 616a-d extend through the respective clearance apertures 309 in the frame elements 304a-d of the support 300 and into the engagement apertures 318 of respective ones of the resilient elements 308a-d of the support 300. With the pins 626a-d of the actuator units 616a-d so located, the tensioning assemblies 608a-d are then actuated to tension the resilient elements 308a-d of the support 300 as required. In this embodiment the actuators 616a, b are actuated by a predetermined pressure such that the extension of the resilient elements 308a-d corresponds to a predetermined tension to which the screen 302 is to be tensioned.

As illustrated in Figure 25, a printing screen 302 is then located on the seat 611 of the table 606 such that the edges thereof extend over the respective ones of the attachment elements 306a-d of the support 300. With the screen 302 so located, the edges of the screen 302 can then be welded to respective attachment elements 306a-d of the support 300. In a welding step, the table assembly 602 is rotated such that one edge of the screen 302 is adjacent the welding assembly 642, and the screen 302 is welded to the attachment element 306a-d of the respective support member 301a-d of the support 300 at a plurality of positions by repeatedly actuating the welding unit 642 and moving the welding unit 642 along the respective edge of the screen 302 by operation of the positioning unit 644. This welding step is then repeated for each of the other edges of the screen 302, with the table assembly 602 being rotated so as to present the other respective edges of the screen 302 to the welding unit 642.

Finally, it will be understood that the present invention has been described in its preferred embodiments and can be modified in many different ways without departing from the scope of the invention as defined by the appended claims.

Claims

1. A printing screen support for supporting a printing screen under tension, the support comprising: a frame; a plurality of attachment elements for attachment to a printing screen; and a plurality of tensionable resilient elements coupling the attachment elements to the frame, with the attachment elements being moved in a direction inwards of the frame on tensioning the resilient elements.

2. The support of claim 1, wherein at least one of the attachment elements is disposed inwardly of the frame.

3. The support of claim 2, wherein each of the attachment elements is disposed inwardly of the frame.

4. The support of any of claims 1 to 3, wherein at least one of the resilient elements is disposed inwardly of the frame.

5. The support of claim 4, wherein each of the resilient elements is disposed inwardly of the frame.

6. The support of any of claims 1 to 3, wherein at least one of the resilient elements is disposed within the confines of the frame.

7. The support of claim 6, wherein each of the resilient elements is disposed within the confines of the frame.

8. The support of any of claims 1 to 7, wherein the attachment elements are substantially co-planar with a lowermost surface of the frame.

9. The support of any of claims 1 to 8, wherein the resilient elements are substantially co-planar with a lowermost surface of the frame.

10. The support of any of claims 1 to 9, wherein the frame has a thickness of not more than about 40 mm.

11. The support of claim 10, wherein the frame has a thickness of not more than about 10 mm.

12. The support of any of claims 1 to 11, wherein the frame is of tubular section.

13. The support of any of claims 1 to 12, wherein the frame is of substantially rectangular section.

14. The support of any of claims 1 to 13, wherein each of the attachment elements includes a flat surface for attachment to a printing screen.

15. The support of claim 14, wherein at least one of the attachment elements comprises a flat sheet.

16. The support of claim 15, wherein each of the attachment elements comprises a flat sheet.

17. The support of any of claims 1 to 16, wherein the attachment elements are separate elements.

18. The support of any of claims 1 to 17, wherein the attachment elements are substantially rigid elements.

19. The support of any of claims 1 to 18, wherein at least one of the resilient elements comprises a concertina structure.

20. The support of claim 19, wherein each of the resilient elements comprises a concertina structure.

21. The support of any of claims 1 to 18, wherein at least one of the resilient elements includes at least one resilient member which includes first and second sections which couple respective ones of the frame and the respective attachment element and define a space therebetween.

22. The support of claim 21, wherein each of the resilient elements includes at least one resilient member which includes first and second sections which couple respective ones of the frame and the respective attachment element and define a space therebetween.

23. The support of any of claims 1 to 18, wherein at least one of the resilient elements includes first and second resilient members, each including first and second sections which couple respective ones of the frame and the respective attachment element and define a space therebetween.

24. The support of claim 23, wherein each of the resilient elements includes first and second resilient members, each including first and second sections which couple respective ones of the frame and the respective attachment element and define a space therebetween.

25. The support of any of claims 21 to 24, wherein the or each resilient member comprises a looped member.

26. The support of claim 25, wherein the or each resilient member comprises a substantially U-shaped or N-shaped member.

27. The support of any of claims 21 to 26, wherein at least ones of the resilient elements include an engagement aperture for engaging an engagement member of a tensioning jig.

28. The support of any of claims 1 to 27, wherein each respective attachment element and the at least one resilient element connected thereto are formed from a single sheet.

29. The support of claim 28, wherein the sheet is a metal sheet.

30. The support of any of claims 1 to 29, wherein the frame comprises a plurality of connected frame elements.

31. The support of claim 30, wherein the frame comprises a plurality of frame elements having welded connections.

32. The support of claim 30, wherein the frame comprises a plurality of frame elements and a plurality of connecting pieces connecting the same.

33. The support of any of claims 30 to 32, wherein at least part of each frame element and the at least one attachment element and the at least one resilient element connected thereto are formed from a single sheet.

34. The support of claim 33, wherein each respective frame element and the at least one attachment element and the at least one resilient element connected thereto are formed from a single sheet.

35. The support of claim 33 or 34, wherein the sheet is a metal sheet.

36. The support of any of claims 30 to 32, wherein the frame elements comprise extruded sections.

37. The support of any of claims 1 to 36, wherein at least one of the attachment elements and the at least one resilient element connected thereto are substantially planar.

38. The support of claim 37, wherein each respective attachment element and the at least one resilient element connected thereto are substantially planar.

39. The support of any of claims 1 to 38, wherein each attachment element is coupled to the frame by a single resilient element.

40. The support of any of claims 1 to 38, wherein each attachment element is coupled to the frame by a plurality of resilient elements.

41. The support of any of claims 1 to 40, further comprising: a plurality of engagement elements coupling respective ones of the resilient elements to the frame.

42. The support of claim 41 , comprising: a plurality of connection elements each comprising an engagement element, at least one attachment element and at least one resilient element.

43. The support of claim 42, wherein the connection elements are detachably coupled to the frame.

44. The support of claim 42 or 43, wherein the frame includes at least one slot and the connection elements each include at least one projection for engagement in the at least one slot.

45. The support of any of claims 42 to 44, wherein the frame includes a recess in a lower surface thereof accommodating the connection elements.

46. The support of any of claims 1 to 45, wherein the frame is of rectangular shape.

47. The support of claim 46, wherein the frame has at least one edge of narrower width than the other edges thereof.

48. The support of claim 47, wherein each pair of opposing edges of the frame has a different width.

49. A printing screen support for supporting a printing screen under tension, the support comprising: a frame; a plurality of attachment elements for attachment to a printing screen, the attachment elements being disposed inwardly of the frame; and a plurality of resilient elements connecting the attachment elements to the frame, the resilient elements being tensionable to a predeterminable tension.

50. A printing screen support for supporting a printing screen under tension, the support comprising: a frame; a plurality of attachment elements for attachment to a printing screen; and a plurality of resilient elements connecting the attachment elements to the frame; wherein each respective attachment element and the at least one resilient element connected thereto are formed from a single sheet.

51. A printing screen assembly comprising the printing screen support of any of claims 1 to 50 in combination with a printing screen attached to the attachment elements of the support.

52. The assembly of claim 51, wherein ones of the resilient elements are tensioned to different tensions.

53. The assembly of claim 52, wherein the printing screen is rectangular in shape and the resilient elements are tensioned such that an increased tension is applied at each comer of the screen.

54. The assembly of claim 53, wherein the resilient elements are tensioned such that the tension increases progressively from a mid-point to the respective adjacent comers of each edge of the screen.

55. A method of mounting a printing screen to a printing screen support, the method comprising the steps of: providing a printing screen support comprising a frame, a plurality of attachment elements for attachment to a printing screen, and a plurality of tensionable resilient elements coupling the attachment elements to the frame; tensioning the resilient elements; and attaching a printing screen to the attachment elements.

56. The method of claim 55, wherein the attachment elements are moved in a direction inwards of the frame on tensioning the resilient elements.

57. The method of claim 55 or 56, wherein the step of tensioning the resilient elements comprises the step of: tensioning ones of the resilient elements to different tensions.

58. The method of claim 57, wherein the printing screen is rectangular in shape, and the step of tensioning the resilient elements comprises the step of: tensioning the resilient elements such that an increased tension is applied at each comer of the screen.

59. The method of claim 58, wherein the resilient elements are tensioned such that the tension increases progressively from a mid-point to the respective adjacent comers of each edge of the screen.

60. The method of any of claims 55 to 59, wherein the step of attaching the screen to the attachment elements comprises the step of: welding the screen to the attachment elements.

61. An assembly jig for mounting a printing screen to a printing screen support comprising a frame, a plurality of attachment elements for attachment to the screen and a plurality of tensionable resilient elements coupling the attachment elements to the frame, the assembly jig comprising: a support unit for supporting the screen and the support; first and second sets of engagement members for engaging opposed attachment elements or resilient elements coupled thereto of the support; and a tensioning mechamsm for relatively moving the engagement members of the first and second sets of engagement members towards one another to extend the resilient elements coupled to the opposed attachment elements and tension the same.

62. The jig of claim 61 , further comprising: third and fourth sets of engagement members for engaging further opposed attachment elements or resilient elements coupled thereto of the support extending substantially orthogonally to the first-mentioned opposed attachment elements of the support; and wherein the tensioning mechanism is configured to move the engagement members of the third and fourth sets of engagement members relatively towards one another to extend the resilient elements coupled to the further opposed attachment elements and tension the same.

63. The jig of claim 61 or 62, wherein the tensioning mechanism is configured to move the engagement members of at least one of the sets of engagement members in unison.

64. The jig of any of claims 61 to 63, wherein the tensioning mechanism is configured to move groups of ones of the engagement members of at least one of the sets of engagement members in unison.

65. The jig of any of claims 61 to 64, wherein the tensioning mechanism is configured to move ones of the engagement members of at least one of the sets of engagement members individually.

66. The jig of claim 63, wherein the tensioning mechanism is configured to move the engagement members of each of the respective sets of engagement members in unison.

67. The jig of claim 64, wherein the tensioning mechanism is configured to move groups of ones of the engagement members of each of the respective sets of engagement members in unison.

68. The jig of claim 65, wherein the tensioning mechanism is configured to move ones of the engagement members of each of the respective sets of engagement members individually.

69. The jig of claim 65 or 68, wherein the tensioning mechamsm is configured such that ones of the resilient elements are tensioned to different tensions.

70. The jig of claim 69, wherein the tensioning mechanism is configured such that the resilient elements are tensioned such that an increased tension is applied at each comer of a rectangular printing screen.

71. The jig of claim 70, wherein the tensioning mechamsm is configured such that the resilient elements are tensioned such that the tension increases progressively from a mid-point to the respective adjacent comers of each edge of the screen.

72. The jig of any of claims 68 to 71, wherein the tensioning mechanism is configured such that groups of ones of the engagement members of at least one of the sets of engagement members are moved in different orients relative to a reference direction.

73. The jig of claim 72, wherein the tensioning mechanism is configured such that groups of ones of the engagement members of each of the respective sets of engagement members are moved in different orients relative to respective reference directions.

74. The jig of claim 72 or 73, wherein the groups comprise respective halves of the engagement members of any set of engagement members.

75. The jig of any of claims 68 to 71, wherein the tensioning mechamsm is configured such that ones of the engagement members of at least one of the sets of engagement members are moved in different orients relative to a reference direction.

76. The jig of claim 75, wherein the tensioning mechanism is configured such that ones of the engagement members of each of the respective sets of engagement members are moved in different orients relative to respective reference directions.

77. The jig of any of claims 61 to 76, further comprising: an attachment unit for attaching the screen to the attachment elements of the support.

78. The jig of claim 77, wherein the attachment unit comprises a welding unit for welding the screen to the attachment elements of the support.