WO2007113492A2

WO2007113492A2 - Wiper blade for printer roller

Info

Publication number: WO2007113492A2
Application number: PCT/GB2007/001143
Authority: WO
Inventors: Gary Williamson
Original assignee: Litho Devices Limited
Priority date: 2006-04-03
Filing date: 2007-03-28
Publication date: 2007-10-11
Also published as: GB0606718D0; WO2007113492A3

Abstract

A wiper blade for a printer roller in which the deformable wiper tip is attached to a support plate by being gripped between inwardly crimped webs. An upstanding central prong is received in the wiper tip for additional support. The wiper tip can comprise a body part which is gripped by the support plate and a contact edge part for contacting the roller, wherein the contact edge part is harder than the body part. The body part and contact edge part may be coextruded in one piece.

Description

WIPER BLADE FOR PRINTER ROLLER

Field of the Invention

This invention relates to waste material collection apparatus for printer rollers, e.g. to systems for collecting waste liquids, inks or other print-related substances from rollers used in the printing industry.

Background to the Invention

In the printing industry, waste material is removed from rollers by using a wiper blade, which has a tip of rubber or other suitable material that engages a rotating roller to scrape any surplus material away. The collected material can be directed from the blade to a collection tray. A known type of wiper blade consists of two components: a steel plate and a elastomeric (e.g. nitrile rubber or ethylene polypropylene diene monomer (EPDM)) tip attached along a wiping edge thereof. Fig. 1 shows a cross-sectional view through such a wiper blade. The rubber tip 2 is vulcanised on to the steel plate 1. This is done by placing the steel plate 1 in a tool and inserting two separate pieces of rubber along respective sides of the wiping edge. The tool heats the rubber pieces and presses them together (typically with around 300 tonnes of pressure) so that the rubber pieces melt into each other and onto the steel plate. The tool also moulds the melted rubber to achieve the desired tip shape. The tool must be allowed to cool sufficiently before the wiper blade is removed, in order to let the tip set and to prevent damage during removal. More recently, the printing industry has begun using polyurethane tipped wiper blades because of their useful properties in the removal of certain materials. Polyurethane was also found to have desirable wear resistance and resistance to ultraviolet (UV) radiation. However, polyurethane does not vulcanise well, so the process described above is not efficient because many produced blades are defective and must be rejected. This problem is solved by cold casting polyurethane blades. Cold casting involves pouring a liguid polyurethane mix into a mould that also contains the steel plate and then allowing the mix to set. Whilst the setting process can be accelerated using heat (e.g. to help remove the solvent from the mix) , each blade can take more than 16 hours and as much as 24 hours to form.

Summary of the Invention

A first aspect of the invention provides a wiper blade in which the plate physically (mechanically) grips the wiping tip. The gripping can be effected quickly and may avoid the need for heating and cooling which can slow down the manufacturing methods described above.

Accordingly, the first aspect of the invention may provide a wiper blade for removing waste material from a printer roller, the blade having a rigid plate with a wiper tip along a wiping edge thereof, wherein the rigid plate includes a jaw at the wiping edge, in which jaw the wiper tip is securably gripped- to fasten it to the plate. In contrast to known wiper blades, the dominant fixing force that attaches the wiper tip to the rigid plate is mechanical (i.e. rather than the bonding that occurs e.g. through vulcanisation) .

The jaw may be integral with the plate. For example, the plate and jaw may be extruded in one piece e.g. from aluminium or steel. The jaw may define a recess parallel to or along the wiping edge. In one embodiment, the jaw comprises two elongate webs, parallel to the wiping edge one or both of which may protrude out of the plane of the plate to form the recess. In this embodiment, the webs are arranged to grip the wiper tip.

The wiper tip may comprise a contact edge for engaging the roller surface, and a base receivable in the jaw. In one embodiment, the base is shaped e.g. pre- machined to cooperate with the recess defined by the jaw. This arrangement can provide a snug fit between the wiper tip and jaw to ensure a secure attachment.

The jaw may include a central elongate web parallel to the wiping edge that projects outwardly from the recess and is cooperably received in a channel formed (e.g. pre-machined) in the wiper tip. The central web may be in the plane of the plate. Such an arrangement can improve the strength and stability of the attachment e.g. because the base of the wiper tip now comprises two elements, each of which are gripped between the elongate webs. The central web can be integral (co-extruded) with the rigid plate.

In one embodiment, the recess is tapered to secure the wiper tip. For example, the elongate webs may slope toward the plane of the plate in the direction toward the wiping edge. This can also increase the strength of the attachment . Adhesive may be provided between the jaw and wiper tip as an additional strengthening attachment or to ensure that there is to relative movement between these components during the attaching process. Another expression of the first aspect may be a method of manufacturing a wiper blade for removing waste material from a printer roller, the wiper blade having a rigid plate with a wiper tip along a wiping edge thereof, the method including bringing the wiper tip into cooperation with a jaw at the wiping edge of the plate, and closing the jaw onto the wiper tip to fasten the wiper tip to the plate .

The jaw and wiper tip may have any of the features described above. The method may include pre-machining the wiper tip to give it a shape including the contact edge mentioned above and a base to cooperate with the jaw. Pre- machining the tip (and not needing to use heating/cooling steps to achieve attachment) permits a wider variety of materials to be used on the tip. The tip may be preformed by extrusion.

In one embodiment, the step of closing the jaw involves crimping together two elongate webs that run parallel to the wiping edge and protrude from the plate. Such inward crimping can form a strong and permanent connection between the components. The crimped webs may have tapered inner surfaces so when crimped they form a wedge-shaped joint between the plate and tip. The method may include applying adhesive between the jaw and tip e.g. before crimping to further strengthen the attachment . This method can offer a significant time saving when compared with conventional wiper blade formation techniques because it can take only about 30 seconds from assessing the components to have a finished usable article.

The first aspect of the invention may also include a kit of parts for making a wiper blade and a waste collection apparatus for printer rollers that incorporates a wiper blade. A second aspect of the invention, which may be independent of the first aspect, concerns the wiper tip itself. In the second aspect, the material at the contact edge of the wiper tip is more hard-wearing than the material of the rest of the wiper tip body. Wiper tips formed by vulcanisation were necessarily homogenous. Conventional materials for the blades, such as nitrile rubber, EPDM or polyurethane are prone to wear. This can cause a problem known as "roller squeal" when the tip rubs against a roller that has become dry during a wash-up cycle. The friction caused by the rubbing can cause heat to build up in the apparatus, which can accelerate wear. Moreover, the rubbing can cause undesirable vibration in the apparatus .

According to the second aspect, there may be provided a wiper blade for removing waste material from a printer roller, the blade having a support plate and a wiper tip along a wiping edge of the support plate, wherein the wiper tip comprises a body portion attached to the support plate and a contact edge portion for contacting the^' printer roller, the contact edge portion comprises a material that is harder than the material of the body portion. The contact edge portion may be fused to the body- portion, i.e. they may have the same or a similar molecular structure which allows them to be formed integrally together by coextrusion. The contact edge portion may be formed from a thermoplastic vulcanizate (TPV) . Such materials may be particularly suitable for coextrusion. For example, polyester or polypropylene may be used. The contact edge portion may be 100% polypropylene. This material is both durable and exhibits desirable chemical and ultraviolet (UV) radiation resistance. Compared with a standard wiper tip, the two-material tip of the second aspect can achieve up to ten times better wear performance. The hardness of the contact edge portion may be selected according to the particular use. For example, the edge portion may have a hardness of around 60 Shore D.

The body portion may be formed from conventional wiper tip materials, e.g. EPDM. The body portion may be formed from a fully crosslinked mix of polypropylene and EPDM. The mix may be selected to give properties such as chemical and UV resistance. In a development of the invention, the body portion may be made of softer material than conventional wiper tips . This can make the wiper blade more flexible, so that it is more adaptable to slight misalignments between the printer roller and wash-up tray apparatus, e.g. due to manufacturing tolerances. Softer material could not be used for this purpose in conventional wiper blades because they would wear too quickly. By providing a more durable contact edge portion, the physical requirements for the body portion may be relaxed. For example, the body portion may have a Shore A value of less than 85, e.g. 64. As mentioned above, the second aspect of the invention may be used in conjunction with the first aspect, i.e. a two-material coextruded wiper tip can be mechanically clamped to a support plate using the jaw structure disclosed above.

Another expression of the second aspect may be a method of manufacturing a wiper blade for removing waste material from a printer roller, the method including coextruding together a body portion and a contact edge portion of a wiper tip, wherein the contact edge portion is made of a harder material than the body portion.

Co-extrusion permits formation of a dual hardness material in a single profile.

The method may further include attaching the wiper tip to a support plate, e.g. by crimping the body portion between elongate webs as discussed above with reference to the first aspect.

Brief Description of the Drawings

Examples of the invention are described below with reference to the accompanying drawings, in which:

Fig. 1 is a cross-sectional view of a conventional wiper blade and is described above; and Figs. 2A-2C illustrate a cross-sectional view of the assembly of a wiper blade that is an embodiment of the first aspect of the invention;

Fig. 3 illustrates a cross-sectional view of a wiper blade that is an embodiment of the second aspect of the invention.

Detailed Description; Further Options and Preferences Fig. 2A shows two components of the wiper blade device of the present invention before they are attached to one another. The rigid plate 4 is an extruded plate of aluminium, and its cross section has a trident-like shape. Two webs 6 project out from the plane of the plate 4 in a hook-like way to form a recess 7 out of which projects a central prong 8, parallel to the plane of the plate 4. The wiper tip 10 is pre-machined to have a contact edge 12 facing away from the plate 4 and adapted to engage the surface of a printer roller (not shown) . The other end of the wiper tip has a channel 14 for receiving the prong 8 on the plate 4 and projections 16 shaped to cooperate with the recess 7 formed by the projecting webs 6. The webs 6 therefore form a jaw structure adapted to receive the projections 16 on the wiper tip 10.

Fig. 2B shows the arrangement where the wiper tip 10 is mounted on the plate 4 so the central prong 8 fits snugly in the channel 14 and the projections 16 fit in the recess 7. To fasten the plate 4 to the wiper tip 10, pressure is applied on both of the projecting webs 6 to push them towards the central prong 8. The pressure is selected to bend the webs inward so that they grip the wiper tip 10; specifically, that they grip the projections 16.

Fig. 2C shows the gripped configuration. The inwardly crimped webs 6 each provide a tapering surface 18 which creates a wedge-shaped joint between the plate 4 and the wiper tip 10. Each web 6 includes an inwardly projecting tang along it top edge (edge furthest from bottom of recess 7) . The tangs improve the security of the grip on the tip 10.

In a development of the process shown in Figs. 2A to 2C, adhesive may be applied to the inner surfaces of the recess 7 to ensure that the wiper tip is secured thereto during the crimping process and to strengthen further the final join. For firm materials, such as polyurethane, adhesive is not required because the wedge-shaped joint and tangs can provide sufficient grip. Fig. 3 shows a wiper blade that is an embodiment of the second aspect of the invention. The wiper blade has a wiper tip 20 that is attached to a support plate 4 in the same way as that illustrated in Figs. 2A-2C. The same reference numbers are given for corresponding features.

The difference between Figs. 2A-2C and Fig. 3 is in the composition of the wiper tip 20. In Fig. 3, the wiper tip 20 has two parts: a body part 22 which is gripped between the inwardly crimped webs 6, and a contact edge part 24 which is adapted to contact the printer roller (not shown) . The wiper tip 20 is formed in one piece by coextrusion. The body part 22 and contact edge part 24 are therefore fused (e.g. crosslinked) with each other. The contact edge part 24 is made of polypropylene whereas the body part 22 is made from a mix of EPDM and polypropylene. For example, Santoprene® TPV may be used for the body portion. The hardness for the body portion depends on the grade of TPV used (effectively the ratio of EPDM to polypropylene) , and can be from 40 or 50 Shore A to 50 or 60 Shore D.

The contact edge part 24 is harder and more durable than the body part 22.

Claims

1. A wiper blade for removing waste material from a printer roller, the blade having a support plate and a wiper tip along a wiping edge of the support plate, wherein the support plate includes a jaw at the wiping edge, in which jaw the wiper tip is gripped to secure it to the plate.

2. A wiper blade according to claim 1, wherein the jaw is integral with the support plate.

3. A wiper blade according to claim 2, wherein the support plate and jaw are extruded in one piece.

4. A wiper blade according to any preceding claim, wherein the jaw defines a recess along the wiping edge.

5. A wiper blade according to any preceding claim, wherein the jaw comprises two elongate webs along the wiping edge, one or both of the elongate webs protruding out of the plane of the plate to form a recess which receives the wiper tip therein.

6. A wiper tip according to claim 4 or 5, wherein the jaw includes a central elongate web along the wiping edge, the central web being arranged to project outwardly from the recess and to be receivable in a corresponding channel in the wiper tip.

7. A wiper blade according to any preceding claim, wherein the wiper tip comprises a contact edge for engaging a surface of a printer roller, and a base receivable in the jaw.

8. A wiper blade according to any of claims 4 to 6, and 7, wherein the wiper tip base is shaped to cooperate with the recess defined by the jaw.

9. A wiper blade according to any preceding claim, wherein the jaw defines a tapered recess.

10. A wiper blade according to any preceding claim, wherein the wiper tip is bonded to the jaw.

11. A method of manufacturing a wiper blade for removing waste material from a printer roller, the method including: engaging a wiper tip with a support plate by mounting the wiper top in a jaw located along a wiping edge of the support plate, and closing the jaw onto the wiper tip to secure the wiper tip to the support plate.

12. A method according to claim 11 including shaping the wiper tip to provide a contact edge for engaging a surface of a printer roller, and a base receivable in the jaw.

13. A method according to claim 11 or 12, wherein closing the jaw includes crimping together two elongate webs that run along the wiping edge and protrude from the plate .

14. A method according to claim 13, wherein crimping the two elongate webs includes forming a wedge- shaped joint between the support plate and wiper tip.

15. A method according to any of claims 11 to 14 including applying adhesive between the jaw and wiper tip.

16. A kit of parts for making a wiper blade according to any of claims 1 to 10, the kit comprising the wiper tip and the support plate.

17. A wiper blade for a printer roller, the wiper blade comprising a deformable wiper tip attached to a support plate, wherein the support plate includes a gripping portion arranged to secure the wiper tip to the support plate.

18. A wiper blade for a printer roller, the wiper blade comprising a deformable wiper tip attached along a distal edge of a support plate, wherein the support plate includes two outer webs along the distal edge which grip the wiper tip.

19. A wiper blade according to claim 18, wherein the distal edge of the support plate has a trident-shaped cross-section.

20. A wiper blade for removing waste material from a printer roller, the blade having a support plate and a wiper tip along a wiping edge of the support plate, wherein the wiper tip comprises a body portion attached to the support plate and a contact edge portion for contacting the printer roller, the contact edge portion comprises a material that is harder than the material of the body portion.

21. A wiper blade according to claim 20, wherein the contact edge portion is fused with the body portion.

22. A wiper blade according to claim 20 or 21, wherein the contact edge portion and body portion are coextruded in one piece.

23. A wiper blade according to any of claims 20 to

22, wherein the contact edge portion is made of polypropylene .

24. A wiper blade according to any of claims 20 to

23, wherein the body portion has a Shore A hardness of less than 85.

25. A wiper blade according to any of claims 20 to

24, wherein the support plate includes a jaw which is arranged to grip the body portion to secure the wiper tip to the plate.

26. A method of manufacturing a wiper blade for removing waste material from a printer roller, the method including coextruding together a body portion and a contact edge portion of a wiper tip, wherein the contact edge portion is made of a harder material than the body portion.