Printing – Special article machines – Bed and platen
Reexamination Certificate
1999-12-20
2001-06-12
Hilten, John S. (Department: 2854)
Printing
Special article machines
Bed and platen
C101S035000, C101S163000
Reexamination Certificate
active
06244172
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a device and a method at a tamp pad and at tamp printing intended to simplify the printing method, in which ink is applied on a tamp pad, that prints a picture on a piece having concave sides and a convex bottom, wherein the tamp pad has a shape in conformity with the piece for printing on the bottom and sides of the piece and can be provided with channel means for conveying away air accumulated between the piece and the tamp pad, so that the ink can be applied on surfaces difficult to access.
BACKGROUND OF THE INVENTION
In designs of this kind appearing on the market it is possible by means of a method called tamp printing to transfer a picture to a piece on surfaces which are only slightly curved, for example a ball, a front side on a mobile telephone etc. The principle for tamp printing of metal ink is described for example in PCT/SE97/00372 and PCT/SE98/01678, which are hereby incorporated by reference. The printing with good result on surfaces with corners and neighbouring sides and/or other formations, such as holes, recesses or elevations, is difficult with present technique to tamp print, as the tamp pad will not print satisfactory in corners and as it is not designed to print on neighbouring sides and further as it is not capable of allowing accumulated air in the corners to escape, as the tamp pad covers the air accumulation from all directions, so that the ink will not be applied on the piece at these locations. This means that great areas will not be covered by ink. This is a great problem, as this method has to be limited to use on pieces not having a complicated shape as mentioned above.
At the manufacture of electronic units, for example mobile telephones, an electrically conductive layer is needed for shielding off electromagnetic radiation which layer is provided by inks containing a great proportion of metal fragments which conduct current. By means of tamp printing it is possible to print such a layer solely on simple surfaces, which only has a moderately curved surface, and sides, corners, holes, smaller elevations etc can not be printed. By means of other known methods, which are more expensive to use, such as vacuum vaporizing and spray painting, it is possible to provide these units with an electrically conductive layer also on places difficult to access. Otherwise leakage of electromagnetic radiation appears at holes in the layer.
Thus, tamp printing is a comparably very cheap method, as costs for removing undesired ink at undesired places, for example at holes, screw connections and front sides, can be dispensed with. There is further no spillage of ink, as only the needed picture is printed. The machines used for this method are cheaper. It is also simple to automate the method, which means that the labour cost also is low. For this reason it is very interesting to solve the problems with said methods, so that tamp printing in corners and their neighbouring sides as well as on curved surfaces and irregularities becomes possible.
SUMMARY OF THE INVENTION
An object of the present invention is thus to eliminate the drawbacks inherent with the designs mentioned above by adopting the shape of the tamp pad in accordance with the design of the piece with concave and convex surfaces, so that at least a neighbouring side of the piece can be concurrently printed by providing the tamp pad with recesses ventilating away the air accumulations at the corners and other hole spaces of the piece, so that the tamp pad is no longer prevented from printing in the mentioned spaces, which are difficult to access.
According to the invention an adaption of the appearance and shape of the tamp pad after the piece to be printed has now been accomplished in that the pad is provided with concave and convex surfaces; further the problem has been solved with the air accumulations formed at the printing and preventing application of ink on the surfaces difficult to access for the tamp pad by transferring the air away from these places via channels and/or hole means in the tamp pad.
According to the invention the tamp pad has at least one corner, generally formed by two sides forming an angle with each other, said sides printing in two stages two neighbouring sides of the piece, so that the substantially horizontal surface of the piece is first printed, when the tamp pad moves generally downwards. Stage two means that the soft tamp pad at continued downwards movement is flattened against the bottom of the piece, so that a counter-pressure is formed, which in turn causes a deformation of the tamp pad, which then expands sidewise, contacting at least an angled side of the piece, so that the tamp pad then is able to print this side. Via a channel, which runs from a corner of the tamp pad upwards all the way to the upper part of the tamp pad, an air accumulation formed at this corner and created at depressing the tamp pad against the piece is conducted away. This means that the ink is not prevented by the air accumulation to reach the corner and other places which otherwise would be difficult to access. In a preferred embodiment of the invention the ink is first fetched from a printing block, which is covered with the intended picture. For accomplishing that the picture is also attached to the sides of the tamp pad, the printing block has a shape adapted to the shape of the tamp pad when the ink is fetched. The tamp pad can also move pivotally over the printing block, wherein the side is first applied against the printing block, so that it is provided with ink. Thereafter the pivotal movement of the tamp pad is continued with continued contact with the printing block, so that the contact angle with this is continuously changed, the remainder of the picture thereby being attached to the tamp pad. The ink can also be fetched from a rotating printing block, that emits the ink to a rotating tamp pad. Combinations of a curved printing block and a movement of the tamp pad can of course also be possible for transferring the entire picture to the tamp pad. At the tamp printing of a piece which is formed as the inside of a mobile telephone cover the tamp pad according to the invention in its preferred embodiment is formed generally as a block provided with a convexly curved underside. Connecting thereto in the hereby formed corners are four generally vertically connecting, concavely curved sides. The upper side of the block does not contact the piece at printing, which means that it can have any shape. When the ink, which constitutes a picture, now shall be printed on the piece, this is accomplished in three stages. First the picture is transferred to the horizontal part of the piece, for example a cover of a mobile telephone, when the bottom of the block is applied on this place. A continued compression of the tamp pad in stage two deforms the convex bottom surface, this deformation being transferred through the tamp pad, so that the convex sides come in contact with the generally vertical sides of the piece, which means that also these are tamp printed. The marked corners of the tamp pad will according to the invention be pressed into the corners of the piece in stage three. In the irregularities of a piece it may be difficult to access with a tamp pad with printing ink. This is according to the invention solved by shaping the tamp pad as exactly as possible after the piece to be printed. For this reason the tamp pad is provided with projections corresponding to recesses in the piece and recesses in the tamp pad corresponding to projections of the piece. Hole means and projections of the tamp pad can also need to be aired via aeration channels in order to remove the air accumulations which prevent the ink from adhering to the piece in accordance with the description above. It is also possible according to the invention to form the tamp pad as a rotating wheel, which fetches its picture via a rotating wheel shaped printing block, which is continuously provided with ink, so that the rotating tamp pad can emit its picture to a piece moving
Eriksson Lars
Holmberg Per
Hilten John S.
Jenkens & Gilchrist
Telefonaktiebolaget LM Ericsson (publ)
Williams Kevin D.
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