EP3521030A1

EP3521030A1 - Pallet holder for screen printing machines

Info

Publication number: EP3521030A1
Application number: EP19155393.2A
Authority: EP
Inventors: Joaquim Matos Ferreira; Antonio PEREIRA DA SILVA
Original assignee: Ktk Lda
Current assignee: Ktk Lda
Priority date: 2018-02-02
Filing date: 2019-02-04
Publication date: 2019-08-07
Anticipated expiration: 2039-02-04
Also published as: EP3521030B1; BR102019002112A2

Abstract

Pallet holder for a screen printing machine, the pallet (2) being a screen printing pallet for supporting an article for screen printing, said pallet holder (1) comprising a releasably attached toothed fitting (6) for coupling the pallet (2) to the pallet holder (1) such that the pallet coupling position relative to the pallet holder is stepwise adjustable by teeth of said fitting (6). The replaceable toothed fitting may comprise a support (6.2) for releasably attaching the fitting to the pallet holder and a toothed rack (6.1) attached to said support, wherein fitting teeth are formed in said toothed rack. The toothed fitting (6) may be made of two metal alloys, a first metal alloy for the toothed rack (6.1) and a second metal alloy for the support (6.2), wherein the first metal alloy is harder than the second metal alloy. The two metal alloys may be such that the support and toothed rack are welded directly.

Description

Technical field

The present disclosure relates to a pallet holder for screen printing machines having a built-in longitudinal coupling assembly for holding a pallet, in particular using different metal alloys, a toothed coupling thereof and respective fitting.

Background

Screen printing is a printing process comprising the use of a mesh screen to transfer ink onto an object, but only on the areas made permeable to the ink on a stencil screen. Screen printing is also known as silk-screen, serigraphy and serigraph printing.
Usually, a blade or ramped surface is moved across the screen to fill the open mesh apertures with ink, and an inverse movement causes the screen to touch the object along a contact line. This causes the ink to touch and adhere to the object through the mesh apertures, as the screen springs back after the blade has passed.
Normally, one colour is printed at a time, so usually several screens are used to produce a multicoloured image or design.
Thus, it is rather important to have a mechanism for lowering said screen onto the object to be printed and also, after printing, for raising said screen from the object. This mechanism, able to be raised and lowered, and containing the printing implements, is the printing head. The object to be printed is placed in a flat pallet, or interchangeably called, a platen, locked to a pallet holder and attached to a machine carousel.
There exist several machine models with different elevation mechanisms used in a printing station; each machine model may allow installation of one to several printing stations disposed in circular, oval or linear positions around the machine main body.
Prior art machines also relate to radial screen printing machines, in particular for textile applications, where the machine that is provided with multiple printing stations.
In practically all machine models existing in the market the objective is to apply product, either ink or other liquid or paste material, in articles and to create a decoration on the article. The product application on the article is implemented by a screen printing process using a screen frame, and such screen containing the pattern or shape to be applied. Each printing station applies the product by screen printing process on the article placed in flat pallet locked on pallet holder, each article may get various products types, each station can apply only one product or several at same time, depending on the printing station technology.
Screen printing machines contain printing stations, having a printing base with a flat pallet and a pallet holder attached to a carousel suitable for rotating around a machine base. The printing base includes a flat pallet supported by a pallet holder including a support arm attached to said machine carousel.
Pallets can be advantageously replaced by other different pallets sizes or shapes to fitting sizes or article shapes. Advantageously, the pallet can be exchanged and its position adjusted longitudinally by means of a toothed fitting. The adjustments can damage these teeth of the toothed fitting, by abnormal use or even by normal use, that is, normal wear.
The pallet holder has to be substantially inflexible in its vertical, horizontal and longitudinal positioning, in order to maintain the printing precision between the different stations and in respect of the printing head.
The pallet holder has to be as light as possible, implying its construction is normally made with standard sheet metal bended and grouped with rivets. The pallet and pallet holder construction need to be light as possible to allow a smooth mechanical shift rotation between stations.
In most existing machines on the market, the pallet holder is usually made by a single standard metal alloy on the main body including the areas where pallet is coupled, with disadvantages compared to the present disclosure.
Printing movement creates vertical heavy stress together with longitudinal stress , thus being necessary to maintain accuracy and precision on the design printed during printing operation. All that pressure is supported by the flat pallet together with pallet holder attached to carousel.
It is very advantageous to allow pallet longitudinal adjustment and pallet retention with facilitated palette removal and replacement.
As described, in screen print machine carousels containing several pallets disposed in circular or oval, the pallet holder weight is very important however it has to withstand very high stress forces. It is necessary to provide a lightweight pallet holder using lighter metal alloys, which is simultaneously able to withstand high stress forces and allow easy replacement and repositioning of the pallets.
Document US2004/0000240A1 describes a pallet for use with a screen printing apparatus having arms extending outwardly from the printing machine supporting an article against a printing force supplied by the screen printing machine. A base portion of the pallet is attachable to the arm of the printing machine and includes a support structure extending therefrom to stabilize and reduce deflection against the printing force. As shown in the drawings, the pallet is attached to the printing machine, whereby a bracket is fixedly attached to the bottom surface of a base portion. The bracket is typically attached to the bottom surface of a centre pallet leg. The bracket includes flange portions that extend outwardly along opposing sides of the bracket. In use, the printing machine arm is inserted into this bracket. The flange portions engage a camming support surface, and cams are used to tighten the flange portions against the camming support surface to attach the pallet to the arm of the printing machine.
However, in document US2004/0000240A1 , the pallet is longitudinally attached to the arm of the printing machine merely by pressure (and consequent friction), thus not having a robust fixation and/or requiring tremendous effort on the cams.
Document US5309831 describes an automatic screen printing press which has a platen turntable carrying a plurality of platens which are indexed through a plurality of stations in an endless path of movement past printing heads having a power-driven squeegee carriage thereon. Each platen is provided on its underside with a clamping screw which passes through a clamping bracket adapted to straddle an open slot in the top of an extension arm to secure the platen in position.
However, in document US5309831 , the pallet is longitudinally attached to the arm of the printing machine merely by pressure (and consequent friction), thus not having a robust fixation and/or requiring tremendous effort on the clamping screws.
These facts are disclosed in order to illustrate the technical problem addressed by the present disclosure.

General Description

Screen printing machines contain printing stations having a printing base with a flat pallet, or interchangeably a platen, and a pallet holder preferably attached to a carousel arranged for moving, e.g. linearly or rotating around, relative to a machine base. The printing base comprises a flat pallet supported by a support arm, herewith also named pallet holder, which is attached to the machine carousel.
Pallets can be advantageously replaced by other different pallets sizes or shapes to fitting sizes or article shapes. Advantageously, the pallet can be exchanged and its position adjusted longitudinally by means of a toothed fitting according to the disclosure. The adjustments can damage these teeth of the toothed fitting, by abnormal use or even by normal use, that is, normal wear and tear.
The pallet holder has to be substantially inflexible in its vertical, horizontal and longitudinal positioning, in order to maintain the printing precision between the different stations and in respect of the printing head.
The pallet holder has to be as light as possible, implying its construction is normally made with standard sheet metal bended and grouped with rivets. The pallet and pallet holder construction need to be light as possible to allow a smooth mechanical shift rotation between stations.
In most existing machines on the market, the pallet holder is usually made in a single standard metal alloy on the main body including the areas where pallet is coupled, with disadvantages compared to the present disclosure.
Screen printing machines perform the printing operation with movement, applying ink on product or garment disposed the flat pallet. Printing movement creates vertical heavy stress together with longitudinal stress necessary to maintain accuracy and precision on the design printed during the printing operation. Printing movement is defined by a motor together with non-slip gear allowing a very high pressure on product to maintaining accuracy. All that pressure is supported by the flat pallet together with pallet holder attached to the carousel.
The pallet can be attached to pallet holder by four coupling points, one with coupling teeth and the others without teeth, i.e. coupling slots. The coupling teeth allow the pallet sufficient longitudinal adjustment and pallet retention relative to the machine centre. After pallet longitudinal adjustment, said teeth also serve to fix the pallet relative to its longitudinal position for subsequent printing operations.
Screen printing machines with pallets holders having lower integrated coupling teeth, not allowing the replacement of said longitudinal adjustment coupling teeth.
A screen printing machine carousel contains several pallets disposed in circular or oval. The pallet holder weight is very important; however it has to withstand very high stress forces. It is necessary to provide a lightweight pallet holder using lighter metal alloys, which is simultaneously able to withstand high stress forces and allow easy replacement and repositioning of the pallets.
Printing operation creates high longitudinal stress on pallet holder teeth, with a single standard metal alloy on pallet holder and coupler teeth being damaged very frequently because the metal alloy on the teeth is the same as the pallet holder main body. Main body metal alloy hardness does not correspond to resistance to stress on the teeth area when teeth are made by standard metal alloy with no special treatment for stress resistance.
The pallet holder has to be substantially inflexible in its vertical, horizontal, torsion and longitudinal positioning, in order to maintain the printing precision between the different stations.
It is disclosed a pallet holder for a screen printing machine, the pallet being a screen printing pallet for supporting an article for screen printing, said pallet holder comprising a releasably attached toothed fitting for coupling the pallet to the pallet holder such that the pallet coupling position relative to the pallet holder is stepwise adjustable by teeth of said fitting.
An embodiment comprises a support for releasably attaching the fitting to the pallet holder and a toothed rack attached to said support, wherein said fitting teeth are formed in said toothed rack.
In an embodiment, the fitting is made of two metal alloys, a first metal alloy for the toothed rack and a second metal alloy for the support, wherein the first metal alloy is harder than the second metal alloy.
In an embodiment, the fitting is made of two metal alloys, a first metal alloy for the toothed rack and a second metal alloy for the support, wherein the two metal alloys are such that the support and toothed rack are welded directly.
In an embodiment, the replaceable toothed fitting support comprises an opening for matching openings between teeth of the tooth rack such that the support is welded to and surrounds the toothed rack.
In an embodiment, the replaceable toothed fitting support comprises ribs formed across said support opening which match corresponding longer teeth extensions formed in said toothed rack.
In an embodiment, the replaceable toothed fitting support has two parts bent at an angle, a first part for receiving the toothed rack and a second part for releasably attaching the fitting to the pallet holder.
In an embodiment, the pallet holder comprises a support arm for supporting and releasably holding the pallet.
In an embodiment, the support arm is made of a bent sheet metal plate or plates.
In an embodiment, the first part of the fitting support is coplanar with first metal sheet plate of the support arm supporting the pallet and the second part of the fitting support is coplanar with a second metal sheet plate of the support arm reinforcing the first metal sheet supporting the pallet.
In an embodiment, the first part of the fitting support is releasably attached to the first metal sheet plate of the support arm supporting the pallet and the second part of the fitting support is releasably attached to the second metal sheet plate of the support arm reinforcing the first metal sheet supporting the pallet.
In an embodiment, the pallet holder support arm is made of a metal alloy of a lower strength than the metal alloy or alloys of the replaceable toothed fitting.
In an embodiment, the pallet coupling position relative to the pallet holder is stepwise adjustable along a longitudinal axis of the pallet holder.
In an embodiment, the pallet coupling position relative to the pallet holder is stepwise adjustable along a proximal-distal axis relative to the screen printing machine.
In an embodiment, comprising an attachment for attaching the pallet holder to the screen printing machine.
An embodiment comprises one or more additional couplings for coupling the pallet to the pallet holder.
In an embodiment, each said additional coupling or couplings comprises a slotted opening, a surface flange and a corresponding rotatable cam surface for coupling the pallet to the pallet holder by inserting said cam or flange surface through said opening, and by rotating said rotatable cam surface to engage said surface flange.
It is also disclosed a pallet holder and pallet assembly for a screen printing machine comprising the pallet holder according to any of the disclosed embodiments.
It is also disclosed a screen printing station comprising the pallet holder and pallet assembly according to any of the disclosed embodiments.
It is also disclosed a screen printing machine comprising the screen printing station according to any of the disclosed embodiments.

Brief Description of the Drawings

The following figures provide preferred embodiments for illustrating the description and should not be seen as limiting the scope of invention.

Figure 1 illustrates an embodiment of a screen printing machine.
Figure 2A illustrates an embodiment of a screen printing machine with an oval carrousel top view.
Figure 2B illustrates an embodiment of a screen printing machine with a circular carousel top view.
Figure 3 illustrates an embodiment of a pallet holder and pallet assembly.
Figure 4 illustrates an embodiment of a pallet holder.
Figure 5 illustrates an embodiment of a pallet holder detail, with integrated longitudinal coupling teeth.
Figure 6 illustrates an embodiment of a pallet holder detail with longitudinal coupling teeth assembly.
Figure 7 illustrates an embodiment of a pallet holder and longitudinal coupling teeth assembly in a perspective view.
Figure 8 illustrates an embodiment of a longitudinal coupling teeth assembly detail view and construction.
Figure 9 illustrates an embodiment of a printing station and machine components showing the printing application movement of a printing movement towards the machine center.
Figure 10 illustrates an embodiment of a printing station and machine components showing the printing application movement of a printing movement away from the machine center.
Figure 11 illustrates an embodiment of a pallet holder and pallet assembly, showing a pallet holder detail with integrated longitudinal coupling teeth.

Detailed Description

The present discloser relates to pallet holder for screen printing machines, built with longitudinal dent coupler assembly and using three metal alloys. Allowing longitude resistance to failure and adjust. The longitudinal dent coupler is exchangeable
Screen printing machines, see fig.1, contain printing stations 3, having a printing base with flat pallet 2 optionally attached to a carousel 12 for rolling around a machine base 11. The printing base comprises a flat pallet supported by a support arm comprised as a pallet holder 1 attached to machine carousel 12.
The pallet is attached to pallet holder by four coupling teeth 5-6, one with teeth 6 and the others without teeth 5. The coupling teeth 15 allow pallet longitudinal adjustment 14 and pallet retention related to machine center. After pallet adjust the teeth lock the position for printing operation.
The pallet holder has to be inflexible in its vertical, horizontal, torsion and longitudinal positioning, in order to maintain the printing precision between the different sift rotation stations movement.
The pallet holder has to be as light as possible, implying its construction made with standard sheet metal bended, joined with rivets. The pallet and pallet holder construction need to be light as possible to allowing a smooth mechanical shift between stations.
A longitudinal toothed coupler assembly 6 is preferably built with two metal alloys has been implemented to improve the teeth 15 hardness to daily operation and waste. The longitude dent coupler assembly 6 is built with two parts, teeth part 6.1, made by metal alloy 1 and teeth support 6.2, made by metal alloy 3.
Teeth 6.1 made by metal alloy 3 is hardness metal alloy them teeth metal alloy 6.1. The metal alloy 3 needs to be similar composition to metal alloy 2 to allow welding between them.
In this way, the maximum permissible force for the motions 9.x is relative to the resistances of the materials themselves.
The pallet holder 1 is preferably made with three metal alloys on its construction. The pallet holder base structure 1 is made by set of folded standard sheets metal grouped by rivets, to form an structure 1, then subsequently assembled to a set 6 of two metal alloys 6.1; 6.2.
The pallet holder 1 contains four points 5-6 for coupling the pallet forming a simultaneous fixation at four points. Three of these points have coupling openings 5 and the fourth point 6 has openings with teeth. Points 5 and 6 secure the pallet holder horizontally, vertically, torsion and longitudinal. Point 6 also allow pallet position longitudinal adjust relative to machine center 11. The pallet holders coupling points 5 6 has various apertures or positions for adjusting and positioning the pallet in the longitudinal 14 relative to the screen printing machine center 11, then coupling teeth block the pallet in the desired position.
Coupling point 6 requires adjustment teeth 15 to allow different pallets sizes and formats, allowing the pallet printing center to be adjusted relative to the screen printing machine center.
To improve tooth 15 longitudinal stress strength, of the present disclosure, it is disclosed to replace a standard pallet coupling 7 with a coupling set 6 containing two parts made with different metal alloys.
Metal part with teeth 6.1, is built with metal alloy with high stress resistance to operation. Metal alloy 6.1 is very hard and does not substantially allow bending at environment temperatures without damage. An important ability of hardness is the resistance to abrasion and localized deformation.
The other metal alloy is to support the teeth and interface with pallet holder 6.2 and is more resistant to overall deformation.
The following features are illustrated in the figures: pallet holder 1; pallet or flat pallet 2; printing station or printing head 3; screen printing 4; pallet coupling points 5; exchangeable longitudinal coupling made by two metal alloy sets 6; exchangeable longitudinal coupling, support part 6.1; exchangeable longitudinal coupling, teeth 6.2; longitude coupling teeth integrated in pallet holder 7; printing squeeze support 8; printing movement 9; printing squeeze 10; machine center or machine base 11; carrousel 12; printing movement motor 13; pallet adjust related to machine center 14; longitudinal coupling teeth 15.
The term "comprising" whenever used in this document is intended to indicate the presence of stated features, integers, steps, components, but not to preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.
The disclosure should not be seen in any way restricted to the embodiments described and a person with ordinary skill in the art will foresee many possibilities to modifications thereof. The above described embodiments are combinable. The following claims further set out particular embodiments of the disclosure.

Claims

A pallet holder for a screen printing machine, the pallet being a screen printing pallet for supporting an article for screen printing, said pallet holder comprising a releasably attached toothed fitting for coupling the pallet to the pallet holder such that the pallet coupling position relative to the pallet holder is stepwise adjustable by teeth of said fitting.
The pallet holder according to the previous claim wherein the toothed fitting is replaceable and toothed fitting comprises a support for releasably attaching the fitting to the pallet holder and a toothed rack attached to said support, wherein said fitting teeth are formed in said toothed rack.
The pallet holder according to the previous claim wherein the fitting is made of two metal alloys, a first metal alloy for the toothed rack and a second metal alloy for the support, wherein the first metal alloy is harder than the second metal alloy.
The pallet holder according to any of the claims 2-3 wherein the fitting is made of two metal alloys, a first metal alloy for the toothed rack and a second metal alloy for the support, wherein the two metal alloys are such that the support and toothed rack are welded directly.
The pallet holder according to any of the claims 2-4 wherein the replaceable toothed fitting support comprises an opening for matching openings between teeth of the tooth rack such that the support is welded to and surrounds the toothed rack.
The pallet holder according to the previous claim wherein the replaceable toothed fitting support comprises ribs formed across said support opening which match corresponding longer teeth extensions formed in said toothed rack.
The pallet holder according to any of the claims 2-6 wherein the replaceable toothed fitting support has two parts bent at an angle, a first part for receiving the toothed rack and a second part for releasably attaching the fitting to the pallet holder.
The pallet holder according to any of the previous claims wherein the pallet holder comprises a support arm for supporting and releasably holding the pallet.
The pallet holder according to the previous claim wherein the support arm is made of a bent sheet metal plate or plates.
The pallet holder according to the previous claim wherein the first part of the fitting support is coplanar with first metal sheet plate of the support arm supporting the pallet and the second part of the fitting support is coplanar with a second metal sheet plate of the support arm reinforcing the first metal sheet supporting the pallet.
The pallet holder according to the previous claim wherein the first part of the fitting support is releasably attached to the first metal sheet plate of the support arm supporting the pallet and the second part of the fitting support is releasably attached to the second metal sheet plate of the support arm reinforcing the first metal sheet supporting the pallet.
The pallet holder according to any of the previous claims wherein the pallet coupling position relative to the pallet holder is stepwise adjustable along a longitudinal axis of the pallet holder.
A pallet holder and pallet assembly for a screen printing machine comprising the pallet holder according to any of the previous claims.
A screen printing station comprising the pallet holder and pallet assembly according to the previous claim.
A screen printing machine comprising the screen printing station according to the previous claim.