Printing – Stenciling – Stencils
Patent
1998-06-01
2000-05-30
Yan, Ren
Printing
Stenciling
Stencils
381023, B05C 1705
Patent
active
060679034
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention is primarily concerned with means for applying solder paste to circuit boards and a mounting support means therefor but may be used for applying other viscous compounds such as glues or adhesives for other purposes.
The present invention provides an improved supporting and tensioning frame for a stencil having improved means for displacement of the mounting teeth and also provides separate support means for the stencil which facilitate insertion and removal of the teeth of the frame in the slots of stencil.
BACKGROUND OF THE INVENTION
In GB 2264460 of Micro Metallic Limited there is disclosed a support and tensioning frame and a rectangular stencil mountable thereon wherein at least two opposite edge regions of the stencil have apertures which receive displaceable mounting fingers or mounting teeth on opposite sides of the frame and tension the stencil by rotary or linear displacement of the teeth which abut the edges of the stencil and lie out of the main plane of the stencil in the tensioned condition.
In GB 2292115A of N. M. Baker a mounting frame is disclosed wherein springs bias stencil mounting bars inwardly into a non-tensioning position and manually operable levers are used to displace cams to move at least two adjacent mounting bars outwardly to tension the stencil. Manual operation is required and the cams may not apply the same even tension nor the same force nor is there the same ease of stencil mounting as in the present invention.
SUMMARY OF THE INVENTION
According to the present invention a support and tensioning frame for a stencil for enabling soldering paste to be applied to electric circuit boards comprises a rectangular support frame with each of at least two opposite side regions of the frame having an elongate stencil support surface against which a stencil abuts and is flexed in such region on tensioning, and a displaceable mounting bar carrying a row of projections or teeth which are insertable and engageable in apertures in opposite side regions of a stencil, characterised by the feature that the mounting bars of said at least two opposite sides of the frame are permanently biased, for example, by spring means, to move away from each other into the stencil engaging position of the teeth, and that optionally operable displacing means are provided for optionally displacing each said mounting bar against the action of its biassing means to displace the mounting bars into closer proximity and, in use, to displace the tensioning teeth out of the apertures in the opposite side regions of the stencil to permit the stencil to disengage from the teeth and frame.
For achieving most accurate stencilling results, it is desirable that a rectangular and preferably square stencil be tensioned along all four sides and thus the following description will mainly be in respect of a stencil having teeth-receiving apertures along all four sides thereof and to a supporting and tensioning frame having mounting bars and tensioning teeth along all four sides thereof.
In accordance with the inventive principle of the earlier GB Patent 2264460, it is preferred that the frame of the present invention operate such that the mounting means which will preferably be teeth, do not extend into the plane in which the main central body of the stencil lies when tensioned which means the edge regions of the stencil have to be flexed over/under surfaces of the frame to be engaged by the mounting teeth.
The optionally operable displacing means will accordingly be preferably provided along all four sides of the frame and preferably be simultaneously operable and preferably will comprise an inflatable and deflatable tubular or other flexible elongate member (normally closed at one end) which will preferably extend continuously around the four sides of the frame so as to act on the four displaceable mounting bars equally and simultaneously. Preferably a releasable valve means is provided to optionally maintain the tubular means in the inflated condition prior to tensioning
REFERENCES:
patent: 3608484 (1971-09-01), Bubley et al.
patent: 4442772 (1984-04-01), Bubley
Alpha Fry Ltd.
Yan Ren
LandOfFree
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