EP3536501A1

EP3536501A1 - Sectional rack gear of a screen printing machine carousel

Info

Publication number: EP3536501A1
Application number: EP19160909.8A
Authority: EP
Inventors: Joaquim Matos Ferreira; António Pereira da Silva
Original assignee: Ktk Lda
Current assignee: Ktk Lda
Priority date: 2018-03-05
Filing date: 2019-03-05
Publication date: 2019-09-11
Anticipated expiration: 2039-03-05
Also published as: BR102019004177A2; EP3536501B1

Abstract

Sectional rack gear for a screen-printing machine carousel, comprising a plurality of gear sections (10), each one in sector shape, wherein each gear section (10) comprises side fittings (9) for engaging with the neighboring sections such that said gear sections, when engaged, form a circumferentially complete gear. The gear sections (10) may be annular sections. The gear teeth are preferably on the outer perimeter of the gear sections. Preferably, the fittings (9) are tongue-groove or dovetail type fittings. The screen-printing machine carousel comprises a base structure (5) wherein, preferably, each of the gear sections is detachably attached. Preferably, the material of the sectional rack gear is more wear-resistant than the material of said base structure (5). The screen-printing machine comprises said carousel and an actuator for rotating said carousel about the screen-printing machine.

Description

Technical Domain

The present disclosure relates to a sectional rack gear applicable to carousels of screen-printing machines and respective screen-printing machine with sectional rack gear applied in the carousel thereof.

Background Art

Screen-printing is a printing process which comprises the use of a matted screen to transfer ink to an object, but only in the ink-permeable areas on a tensioned screen. Screen-printing is also known as serigraphy, screen-printing with stamped printing.
Generally, a surface or blade is moved across the screen to fill the mesh openings, and a reverse 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 openings as the screen returns after the passage of the blade.
Typically, one color is printed at a time, so typically, multiple screens are used to produce a multicolored image or design.
There are several machine models with different lifting mechanisms used in a printing station; each machine model allows the installation of one or more printing stations arranged in circular or oval positions around the main body of the machine.
In all machine models existing on the market, the goal is to apply product, ink or other materials on articles and create a decorative motif in the article. The application of the product in the article is implemented by a screen-printing process using a screen frame containing a pattern or the shape to be applied. Each printing station applies the product by screen-printing process to the item placed on a flat pallet coupled to the pallet carrier. Each station can apply only one product or several at a time, depending on the technology of the printing station.
The pallets which support the article to be printed are usually arranged in a circle, supported by a pallet holder, which is mounted on the base structure of the carousel inserted in the central axis of the machine base. Rotating the carousel around the center of the machine allows positioning the pallets that support the article on the printing stations as a color is applied in each station.
Screen-printing machines contain a plurality of printing stations each with a flat pallet printing base coupled to the pallet carrier mounted to the base structure of the carousel rotating about the base of the machine.
The base structure of the carousel of the printing machine is usually constructed in a circular structure in metal sheets, of standard metal material and cut with fittings between the sheets. After the sheets are engaged, they are punctured in order to block the fitting. The joining of the sheets in the fittings is done by puncture or other fastening technology. In this way a base structure called carousel is built, consisting of a base structure, a pallet holder, and a pallet that is integrated in the machine through a central axis.
These facts are described in order to illustrate the technical problem solved by the embodiments of the present document.

General Description

The present disclosure relates to a sectional rack gear applicable to carousels of screen-printing machines and made of wear resistant metal alloy. This gear concept allows to develop a rack gear of any size while maintaining both gear precision and operation wear resistance. The rack gear allows application in screen-printing machine carousels.
Screen-printing machines contain a plurality of printing stations each with a printing base with pallet mounted in the carousel rotating about the base of the machine. The printing base consists of the flat pallet supported by a support arm called pallet carrier that is mounted to the carousel of the machine.
The carousel of the printing machine is built as a circular structure, preferably in standard metal sheets cut with laser technology, which have fittings between the sheets punched in order to block the fitting and form a rigid structure. The joining of the sheets with fittings is done by fittings or other fastening technology, preferably without causing deformation in the sheets.
The base structure of the carousel is integrated in the machine by an axis, wherein the carousel is moved around the center of the machine through a drive gear, driven by an electric, hydraulic, pneumatic driving element or another movement technology.
Although the toothed gear can be integrated during construction in the base structure of the carousel, the gear according to the present description is preferably constructed separately and thereafter mounted to the base structure of the carousel. This gear is called rack gear.
The sectional rack gear described herein is constructed in separate sections, forming a full circumference after being mounted to the base structure of the carousel. This gear is defined as a sectional rack gear.
The rack gear sections are produced separately and engage therebetween through preferably non-clearance fittings, forming a complete gear mounted to the base structure of the carousel. The number of sections depends on the size of the carousel and the machine to be produced, which can decrease or increase the number of sections depending on the size of the machine's carousel.
The fittings allow the sections to be held together without clearance, or with a minimum of clearance, in order to avoid wear in operation due to friction and failure of engagement with the movement means of the carousel, which would occur if there were relevant clearance between the sections.
By constructing a rack gear separate from the base structure of the carousel, it is possible to use an anti-wear metal alloy, even if heavier, without significantly affecting the overall weight of the carousel. The use of an anti-wear metal alloy enables to increase the operation wear resistance of the rack gear by improving its operating time infinitely.
The construction of the rack gear in separate sections allows its production in standard CNC machines without the need to use specific machines for the full circumference of a rack gear. When producing the rack gear in CNC machines it eliminates the defects defined by the cutting with laser cutting technology evidenced in the toothed gear.
By constructing a rack gear separate from the base structure of the carousel it is possible to replace the rack gear without the need to replace the entire base structure of the carousel.
The rack gear is applied onto the base structure of the carousel. In other implementations, the rack gear can be applied onto other areas of the base structure of the carousel.
A sectional rack gear is described for a stamping machine carousel, comprising a plurality of gear sections, each one in sector shape, wherein each gear section comprises side fittings for engaging with the neighboring sections such that said gear sections, when engaged, form a circumferentially complete gear.
In one embodiment, the gear sections are annular sections.
In one embodiment, the gear teeth are in the outer perimeter of the gear sections.
In one embodiment, the gear sections are flat.
In one embodiment, the gear sections are 4, 5, or 6.
In one embodiment, the fittings are tongue-groove fittings.
In one embodiment, the fittings are dovetail type fittings.
In one embodiment, the sectional rack gear is obtained by CNC machining, Computer Numerical Control, of each one of the gear sections.
In one embodiment, the sectional rack gear is of wear resistant metal alloy.
A screen-printing machine carousel is further described comprising the sectional rack gear according to any of the described embodiments.
An embodiment of the carousel comprises a base structure of the carousel wherein the sectional rack gear is detachably attached to said base structure.
In one embodiment, the sectional rack gear is detachably attached to the lower part of said base structure.
In one embodiment, each one of the gear sections is detachably attached to said base structure.
In one embodiment, the material of the sectional rack gear is more wear-resistant than the material of said base structure.
A screen-printing machine is further described comprising the carousel according to any of the described embodiments and an actuator for rotating said carousel about the screen-printing machine.

Brief Description of the Figures

For an easier understanding, figures are herein attached, which represent preferred embodiments which are not intended to limit the object of the present description.

Figure 1 - Illustration of an embodiment of the circular screen-printing machine with all components.
Figure 2 - Top view illustration of an embodiment of the screen-printing machine evidencing the top view of the carousel.
Figure 3 - Illustration of an embodiment of the complete carousel of the screen-printing machine separate from the main structure of the machine containing drive gear.
Figure 4 - Illustration of an embodiment of the sectional rack gear complete with coupled drive gear.
Figure 5 - Illustration of an embodiment of the sectional rack gear complete with separate sections - in this illustration, 5 sections of the rack gear can be identified.
Figure 6 - Illustration of an embodiment of the rack gear mounted on a central structure of the carousel - detail of the fitting between sections of the rack gear.
Figure 7 - Illustration of a toothed gear integrated in the base structure of the carousel.

Detailed Description

The pallets 2 which support the article to be screen-printed are usually arranged in a circle, see Fig. 1 , each one supported by a pallet holder 1, which is mounted on the base structure 5 of the carousel inserted in the central axis of the base of the machine 11. Rotating the carousel around the center of the machine allows positioning the pallets that support the article on the printing stations as a color is applied in each station.
The screen-printing machine, see Fig. 1 , contains the printing station 3, the flat pallet printing base 2 coupled to the pallet carrier 1 mounted on the base structure 5 of the carousel rotating about the base of the machine 11.
The base structure of the carousel of the printing machine is constructed in a circular structure in metal sheets, of preferably standard metal material and cut with fittings between the sheets. After the sheets are engaged, they are punctured in order to block the fitting. The joining of the sheets in the fittings is done by puncture or other fastening technology. In this way a base structure designated carousel is constructed, see Fig. 3 , consisting of the base structure 5, pallet holder 1, and pallet 2 which is integrated in the machine through a central axis 6. The carousel moves around the center of the machine 11 through the drive gear 8.
The screen-printing carousels can be constructed with a toothed gear 13 at the bottom of the carousel, see Fig. 7 . The toothed gear is normally constructed during cutting of the base structure of the carousel it being integrated into the base structure itself. The base structure of the carousel is preferably constructed of standard metal sheets. It uses the laser cutting technology or other alternative sheet cutting technology. In a non-sectional rack gear, the gear can be integrated during construction at other points in the base structure of the carousel depending on the structure defined, e. g. on top of the carousel.
In the case of a non-sectional rack gear, during the construction of the base structure of the carousel, a toothed gear is integrated in the base structure of the carousel to enable it to be moved about the axis of the machine. The base structure of the carousel includes a toothed gear integrated in order to enable coupling of a drive gear driven by an electric, hydraulic, pneumatic element or other movement technology.
In the case of a non-sectional rack gear, the toothed gear 13 integrated in the base structure 5 of the carousel is constructed of the same material as the base structure, standard sheet metal, and during the same manufacturing process. In the case of the sectional rack gear it is possible to use different materials: a more wear resistant material in the sections of the rack 10 and a lighter or stronger, e.g. cheaper, material in the base structure 5.
Although the toothed gear can be integrated during construction in the base structure of the carousel, the gear according to the present description is preferably constructed separately and thereafter mounted to the base structure of the carousel 5. This gear is called rack gear.
The sectional rack gear described herein is constructed in separate sections 10, forming a full circumference after being mounted to the base structure of the carousel 5. This gear is defined as a sectional rack gear.
The rack gear sections 10 are produced separately and engage therebetween through preferably non-clearance fittings 9, forming a complete gear mounted to the base structure 5 of the carousel. The number of sections 10 depends on the size of the carousel and the machine to be produced, which can decrease or increase the number of sections 10 depending on the size of the machine's carousel.
In particular, the figures illustrate the following features: pallet carrier or pallet holder 1; pallet or flat pallet 2; printing station 3; screen-printing frame 4; base structure 5 of the carousel with central opening for the machine axis; center 6 of the base structure 5 with opening for insertion of the central axis of the machine; rack gear 7; drive gear or movement of the carousel 8; fitting 9 between sections of the rack gear; sections 10 of the sectional rack gear; center of the machine or central base 11 of the machine; complete carousel 12 shown in more detail in Fig. 3 ; toothed gear 13 integrated in the base structure of the carousel.
Alternatively, the sectional rack may consist of multiple overlapping sectional racks which are actuated together by a same means of movement. Alternatively, additional racks may be installed, each one being actuated by its own means of movement.
The pitch of the drive means (typically a chain, or alternatively one or more gears) may be altered in conjunction with the pitch of the rack, as required. A larger pitch, therefore, with rack teeth and chain links furthest from each other, is more robust and more tolerant to misalignments, but has less precision in terms of displacement and by having a larger pitch results in larger, sharper movements.
If the base structure of the carousel is constructed of the same type of standard sheet material of the carousel structure and being constructed with the integrated gear during cutting of the sheet, they generate significant operating problems and disadvantages as will be seen below. The described embodiments avoid the following drawbacks.
The integrated toothed gear constructed in a single assembly, integrated in the base structure of the carousel, in standard sheet metal, presents inherent limitations to the laser cutting technology of the sheet used to construct the base structure. Laser cutting technology has limitations at perpendicular cutting level. Laser cutting technology has a cut limitation by having temperature burrs the cutting not being straight. These defects are derived from the high-power light beam used to melt the material and thus the cut is imperfect in a non-rectangular shape.
Laser cutting technology uses an extreme temperature that melts the metal material by cutting. This technology, applied to the cutting of standard metal sheets, causes small temperature burrs to generate imperfections in the toothed gear. These almost imperceptible burrs create friction and deflection between the toothed gear and drive gear during machine operation.
Laser cut has limitations at the precision level, causing deflections in the circular shape of the toothed gear. The precision and accuracy margin of laser cutting machines are negligible in most constructions, but in the construction of the rack gear integrated into the carousel, it becomes important given constant contact and effort with the drive chain.
The toothed gear integrated in the carousel structure is produced in the same material as the base structure. It does not allow using a metal alloy more wear resistant to moving operation by the drive gear to avoid increasing the overall weight of the carousel. If a base structure of the carousel with wear-resistant alloy were to be built, this carousel would be extremely heavy and would raise production costs making the operation unfeasible due to the high weight and making commercialization impracticable due to the high costs of anti-wear metal alloys as compared to standard material.
Due to the previously defined problems which generate friction by the drive gear in permanent contact with the toothed gear integrated in the base structure of the carousel, a wear is caused on the toothed gear that will create imperfections that can lead to the destruction thereof.
The frictions and imperfections also give rise to problems of controlling the movement of the carousel between stations, causing a slower and less smooth movement due to the friction generated by laser cutting defects. In this way, the carousel movement speed is limited, leading to productivity loss issues, with productivity losses increasing as the operating wear is accentuated on the toothed gear.
The construction of the single gear in a CNC machining center capable of receiving the dimensions of such a part could be analyzed, significantly improving the accuracy of the toothed gear, but that would prevent their commercialization derived at the cost of that operation compared to the laser cut.
The construction of the base structure of the carousel entirely in operation wear-resistant material could be analyzed, but this construction would make it unfeasible to be commercialized due to the high cost and also due to the excessive weight created by the operation wear-resistant sheet.
In the event of failure or damage to the integrated gear, it is necessary to replace the entire structure of the carousel with all necessary replacement procedures.
The term "comprises" or "comprising" when used herein is intended to indicate the presence of the features, elements, integers, steps and components mentioned, but does not preclude the presence or addition of one or more other features, elements, integers, steps and components, or groups thereof.
The embodiments described are combinable with each other. The present invention is of course in no way restricted to the embodiments described herein and a person of ordinary skill in the art can foresee many possibilities of modifying it and replacing technical features with equivalents depending on the requirements of each situation as defined in the appended claims.
The following claims define additional embodiments of the present description.

Claims

Sectional rack gear (10) for screen-printing machine carousel, comprising a plurality of gear sections, each one in sector shape, wherein each gear section comprises side fittings (9) for engaging with the neighboring sections such that said gear sections, when engaged, form a circumferentially complete gear.
Sectional rack gear (10) according to any one of the previous claims, wherein the gear sections are annular sections.
Sectional rack gear (10) according to the previous claim, wherein the gear teeth are on a circular outer perimeter of the gear sections.
Sectional rack gear (10) according to any one of the previous claims, wherein the gear sections are flat.
Sectional rack gear (10) according to any one of the previous claims, wherein the gear sections are 4, 5, or 6.
Sectional rack gear (10) according to any one of the previous claims, wherein the fittings (9) are tongue-groove fittings.
Sectional rack gear (10) according to the previous claim, wherein the fittings (9) are fittings of the dovetail type.
Sectional rack gear (10) according to any one of the previous claims obtained by CNC machining, Computer Numerical Control.
Sectional rack gear (10) according to any one of the previous claims, in wear resistant metal alloy.
Screen-printing machine carousel comprising the sectional rack gear (10) according to any one of the previous claims.
Screen-printing machine carousel according to the previous claim, comprising a base structure (5) of the carousel wherein the sectional rack gear (10) is detachably attached to said base structure.
Screen-printing machine carousel according to the previous claim, wherein the sectional rack gear (10) is detachably attached to the lower part of said base structure (5).
Screen-printing machine carousel according to any claims 10-12 wherein each one of the gear sections is detachably attached to said base structure (5).
Screen-printing machine carousel according to the previous claim, wherein the material of the sectional rack gear (10) is more wear-resistant than the material of said base structure (5).
Screen-printing machine comprising the carousel according to any claims 10-14 and an actuator (8) for rotating said carousel about the screen-printing machine.