Metal deforming – By use of closed-die and coacting work-forcer – Cup or shell drawing
Patent
1996-05-02
1998-08-18
Larson, Lowell A.
Metal deforming
By use of closed-die and coacting work-forcer
Cup or shell drawing
72351, B21D 2200, B21D 2221
Patent
active
057944822
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an apparatus in a hydraulic press for deep drawing, and comprises mutually reciprocating clamping members for fixedly clamping therebetween a sheet metal blank with a predetermined force; at least two counter-directed clamping cylinders connected with, and operating, each respective clamping member; a tool piece over which the sheet metal blank is formed; and a power unit which, for forming the sheet metal blank, is operative to realise a relative movement between, on the one hand, the tool piece, and, on the other hand, the clamping members.
BACKGROUND ART
Numerous different designs of hydraulic presses are previously known in the art for deep drawing of sheet material. In such presses, use is made of a locator ring and a clamping ring between which the sheet metal blank is fixedly clamped with a predetermined force. The thus fixedly retained sheet blank is displaced, together with the clamping ring and the locator ring, down over a tool, the sheet material being drawn radially inwards at the same time as it is formed over the tool.
The clamping ring is mounted on a movable slide which, as a rule, is operated by means of one or more cylinders. In order to realise a predetermined clamping force between the clamping ring and the locator ring so that the sheet metal blank can be held in the requisite manner and prevented from being buckled when it is drawn inwards towards the tool, the locator ring is suspended on a locator cylinder which strives to move the locator ring in a direction which is opposed to the direction of movement of the clamping ring. When the clamping ring is subsequently depressed, the locator ring is entrained in the movement against the action of the locator cylinder. In order that this is not ruptured, hydraulic fluid is released from the locator cylinder via a throttle which regulates that counterforce which the locator cylinder generates.
Displacement of the locator ring against that force which the locator cylinder generates entails a considerable work which in principle is equal to the product of the clamping force against the sheet metal blank and the stroke length of the movement of the locator ring. All of this work is throttled off in the pressure regulator throttle valve and is thereby lost. In many applications, there is inherent work which is lost in this manner, of the same order of magnitude or greater than the work which is required for the actual forming of the sheet metal blank.
PROBLEM STRUCTURE
The present invention has for its object to design the apparatus intimated by way of introduction such that it offers a possibility of substantially reducing the energy consumption in a hydraulic press for deep drawing. In particular, the present invention had for its object to design the apparatus so that the clamping of the sheet metal blank during the forming operation proper may take place without any substantial work being executed. The invention further has for its object to realise an apparatus which is simple and economical in manufacture and which affords high operational dependability.
SOLUTION
The objects forming the basis of the present invention will be attained if the apparatus intimated by way of introduction is characterized in that the working volumes of the clamping cylinders, at least during the forming phase proper, are interconnectable to a common volume; and that a pressure maintenance device is coupled to this volume for realising the predetermined clamping force.
Given that the two counter-directed clamping cylinders are interconnected in this way, they will not accomplish any actual work during their movement. That volume of hydraulic fluid which is forced aside out of the one cylinder flows over to the other cylinder to fill it. The only work which, in such instance, is accomplished is represented by friction and flow losses.
One preferred embodiment of the present invention is suitably characterized in that the total area of the clamping cylinders which act on each clamping member is substanti
REFERENCES:
patent: 1861337 (1931-05-01), Ernst
patent: 2136240 (1936-04-01), Ernst
patent: 2233164 (1938-06-01), Glasner
patent: 2300162 (1938-05-01), Maude
patent: 2333529 (1940-08-01), Ernst
patent: 3202411 (1965-08-01), Heiser
patent: 5339665 (1994-08-01), Yoshikawa
AP&T Tranemo AB
Butler Rodney
Larson Lowell A.
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