Metal fusion bonding – With means to juxtapose and bond plural workpieces – Including compliant cushioning medium
Patent
1990-05-11
1992-10-06
Seidel, Richard K.
Metal fusion bonding
With means to juxtapose and bond plural workpieces
Including compliant cushioning medium
228 443, 100295, 269275, B23K 3704
Patent
active
051524465
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a press for welding magnetic yokes, being of a type which comprises first and second frames movable toward and away from each other and having respective confronting pressure surfaces, a motive means acting between said frames, and a presser associated with each of the pressure surfaces, said pressers defining a saddle piece for receiving said yoke.
The magnetic yokes for which the machine according to this invention is intended are formed by joining together, as by welding, two half-yokes in superimposed relationship. Each half-yoke comprises a pack of about 1800 core sheets having a roughly semicircular shape and each being 5 mm thick, to provide an overall length of the half-yoke of about 9 m. The half-yokes must then be welded together to provide a cylindrical yoke. Welding is carried out along two opposite generatrix lines of the yoke outer surface, at the mating surfaces of the half-yokes. The welding is carried out simultaneously along both generatrix lines to avoid distorting the yoke.
With the weld completed, no appreciable gap should remain between the mating surfaces of corresponding sheets in the two half-yoke packs. It is for this reason that the two half-yoke are held pressed against each other during the welding process. The pressure force is applied to the half-yokes at suitable seats formed around the outer contours of the core sheets.
Since the half-yokes are made up of a large number of superimposed sheets, the pressing load requires to be applied across the entire length of a yoke being processed with the highest possible uniformity, meaning that the pressure surfaces of the press employed and the pressers acting on the pressure pads formed on the sheets are, as far as feasible, to undergo no deformations under load.
BACKGROUND ART
To meet the demand for arrangements to have magnetic yokes correctly welded, the background art has proposed that the press distortion be minimized by using frames which are made as rigid as possible and driven by a large number of hydraulic cylinders placed at short intervals from one another. As an example, a prior press for welding yokes with the above-specified dimensions has 13 hydraulic cylinders which are arranged to act on the pressers with the interposition of respective metal blocks effective to spread the pressing load over the relevant pressure area of the corresponding cylinders.
Thus, the design trend is toward "segmenting" the press into sections of reduced length which can be more easily handled versus induced deformations.
In practice, this prior press operates as if the pressers acting on the half-yokes were split into contiguous sections correspondingly with the areas affected by the respective cylinders, thereby achieving decreased deformation of a yoke being pressed by virtue of a smaller spacing of the cylinders.
Each cylinder, moreover, is suspended above the yoke by means of a portal-type frame the pillars whereof extend upright from the press bed.
A first drawback of this prior press design is that the uniformity of the half-yoke pressing is directly dependent on the machining accuracy of the various press components as well as, of course, on its overall rigidity, particularly as concerns the pressure surfaces and pressers, and on the various hydraulic cylinders applying an even pressure force. In view of the considerable length dimension of a yoke, it is evident that it is quite difficult to ensure uniform pressing conditions over the entire length of the half-yokes.
Further, since welding along the two opposed generatrix lines of the yoke is a time-consuming operation, it becomes necessary to ensure that the pressure inside the hydraulic cylinders be kept throughout its duration within very narrow limits of variation, possibly by providing pressure accumulators, automatically driven manostat-regulated control units, or some like ancillary equipment.
But not even by providing such items of equipment can an initiated processing step be discontinued, such as at the end of the workday, becau
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patent: 1206656 (1916-11-01), Benedictus
patent: 2288158 (1942-06-01), Ellinwood
patent: 2796787 (1957-06-01), Aske
patent: 3873395 (1975-03-01), Ehrlich
patent: 4438911 (1984-03-01), McDougal
patent: 4848639 (1989-07-01), Belanger, Jr.
Western Electric "Stress Compensating Fixture for Lead Frame Bonder" Tech. Digest No. 52, Oct. 1978.
CTE Sistemi S.r.L.
Miner James
Seidel Richard K.
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