US2101527A - Press - Google Patents

Description

Dec. 7, 1937. A. A. BYIERLEIN PRESS Filed Dec. 5, 1934 2 Sheets-Sheet l 2 5 a 0 a 4 4 2 FI ill n n 1 I z a fi;

1/ 4 a I M II I |i|||; I I 0 FJ J 4 a E 3nnentor attorney Dec. 7, 1937. BYERLElN 2,101,527

PRESS Filed Dec. 5. 1954 2 Sheets-Sheet 2 j az Z2. 6!- v if? {D D D r/ 3maentor WM 443 M Gttorneg Patented Dec. 7, 1937 UNITED STTE PE T General Machinery Corporation, Hamilton,

Ohio, a corporation of Delaware Application December 5, 1934, Serial No. 756,107

5 Claims.

This invention relates to presses and more particularly to presses for drawing or forming sheet metal or the like.

One object of the invention is the provision of a press of the character described in which a blank holder or dwell slide has a positive or nonyielding drive for the transmission of all forces up to the normal load capacity of the slide and its operating means, but having suflicient flexibility or non-rigidity for stresses beyond that point to avoid breakage or overstraining of any of the press parts.

Another object of the invention is the provision of a slide operating with a dwell in its movement as by toggle links or the like, the links being connected to the slide through the intermediary of lug members which are secured to the slide by tensioned rods which are initially given a predetermined definite tension so as to maintain an exactly coordinated operation of the slide with respect to its driving means during operation of the press within a predetermined safe working capacity of the slide and its operating means, the rods, however, being adapted to stretch and provide for relative movement between the lugs and the body when an overload is imposed.

Other objects and advantages of the invention will be apparent from the following description, the appended claims and the accompanying drawings, in which,

Fig. 1 is a top plan View of a corner of a press slide embodying the present invention, with the toggle link and its connection removed;

Fig. 2 is a front elevation of the press slide shown in Fig. 1, showing its attachment to an operating or pressure link.

Fig. 3 is a front elevation of the slide portion corresponding to Fig. 2, but showing a step in the stretching of the tension rods;

Fig. 4 is a section on the line 4& of Fig. 2;

Fig. 5 is a detailed view Mom of the spacer shims; and

Fig. 6 is a front elevation of a press having slides and slide operating means embodying the present invention.

Referring more, particularly to the drawings by reference numerals, Ill designates generally the frame of a power press adapted for drawing or forming sheet metal and the like. As herein shown for purposes of illustration of the invention, the frame til is provided with a suitable operating shaft which effects the timed operation of toggle shafts II and I2, which are duplicated at the front and rear of the press. This construction may be in accordance with my prior Patent No. 1,768,503, granted June 24, 1930. The two rockshafts II are connected by toggle links [3 to the four corners of an outer or blank holding slide I5, while the rock shafts l 2 are connected by links M to another slide l6 which also operates as a blank holder or dwell slide as well as serving to draw the metal or blank while the latter is held by the blank holder l5. The two slides l5'and l6 are suitably guided for vertical reciprocatory movement in the press frame It].

The frame preferably comprises frame sections which are bolted to the top or arch ill and tothe bed section ill by means of pretensioned bolts l9 which are normally stressed to serve to secure the various press sections rigidly together for all normal or safe operating capacities of the press, but which are adapted to stretch and provide for some flexibility of the press when a predetermined overload is imposed.

Under normal production demands, an active press must be operated at or near its maximum rate of operation in order to hold forming costs to an economical limit. Under such conditions it is practically certain that press overloads will occur in spite of the competent supervision and careful operation. Dies set a trifle too tight, excess metal thickness, or the accidental placing of two blanks instead of one cannot always be avoided. When an oversized blank, for example, is encountered by the blank holder, an unusual load is created on the crank shaft and an overload is created on the rock shafts and the operating connections between the rock shafts and the blank holder. The overload in question becomes effective about the time the operating link or toggle arm is almost straightened. With a positive or non-yielding connection between the rock shafts and the blank holder even a few thousandths of an inch excess metal thickness will throw a large overload on the slide operating parts and produce ultimate failure of the most vulnerable parts in its operating mechanism, due to fatigue under repeated high stresses. In accordance with the present invention, however, the operating connection between the blank holder and its rock shafts is of a substantially non-yielding char-, acter up to the normal or safe load capacity of these parts, but it is such that sufiicient flexibility is provided to take care of stresses beyond that point.

Referring now more particularly to Figs. 1 to 5 inclusive, the blank holder l5 comprises a main body member 2%, to which the blank holding die is adapted to be secured in any suitable manner. At each corner of the body 2! and rigid or integral therewith is an outwardly and upwardly extending body portion 22. Bolted below each of the body portions 22 is a lug or member 23, bolts or rods 24 serving to hold these parts together. Adjustably mounted in each lug 23 is an adjusting screw 25, positioning nuts 26 serving to locate the screw 25 axially with respect to its supporting lug 23. The upper end of each of the screws 25 is securely bolted to a block 21, herein shown as circular in cross-section and vertically guided in a circular bore 28 provided in the body portion 22. The vertical position of the block 21 in the body portion 22 can thus be changed in order to provide for adjustment of the path of travel of the slide.

The toggle or pressure link I3 is pivotally connected to the block 21, being mounted on a pivot pin 25! so that the link l3 may move angularly during the vertical movements of the slide I5.

In assembling the lug 23 to the body portion 22 the rods 24 are given an initial tension so that for all normal operating loads imposed on this slide and its driving connections the two parts 22 and 23 will be held immovable with respect to one another. The pre-tensioning of the rods is preferably accomplished by placing the lug 23 in contact with the body portion 22, inserting the bolts 24, tightening the nuts 30, and then jacking the two parts 22 and 23 apart as by means of an hydraulic jack ill or the like, which is interposed in the space 32 so that the upper plate 33 of the jack bears against a downwardly facing surface of the body portion 22 while the lower part of the jack rests on the top of the lug 23. A known predetermined pressure is then applied, forcing the two parts 22 and 23 apart so as to pretension the rods 24 evenly to a known degree, and shims 3 5 are then inserted in the spaces or cracks 35 to maintain this tension. The jack is then removed and the adjusting screw 25 together with its block 2! and connected link I3 are then inserted and fastened in their desired positions.

The initial or normal tension given to the rods 24 is a known-predetermined value selected in accordance with the safe operating loads of the blank holder and its driving connections. The rods 24 are of such diameter that they may be initially stressed up to about one-third of their elastic limit to secure the parts 23 and 22 together so that these parts are normally held perfectly rigid with respect to one another during operation of the press within the safe Working capacity of the slide and its operating connections. When stresses beyond that point are imposed, due by reason of an excess metal thickness for example, instead of straining all of the operating or driving connections. of the slide, the rods 24 will stretch or yield in order to safeguard the operating connections and in order to prevent the imposition of too great a force on the metal being drawn or formed. By reason of the flexibility of the slide parts as above set out, the operating or driving links and connections, and the adjusting screw 24 through which the pressures are applied from the toggle links to the slide lugs 23 need not be made heavy enough to take care of 200 or 300 percent overloads, since the stressed rods 24 will yield upon overloads and will stretch sufficiently so that the overloads actually imposed on the toggle links and other driving connections for the slide are much less than even twice the normal loads encountered in normal operation.

It will be apparent that in accordance with the present invention the rods may be pretensioned initially to a known degree, and that the tension initially applied to all of the rods 24 may be made exactly equal and of such value that overloads will effect such stretching action of the rods as to prevent danger of breakage of the slide operating parts. Since the initial tension is well below the elastic limit of the rod material the operating connections of the slide will not be affected after an overload is encountered and there will be no loss of time for shutdown, repair or replacement. In accordance with the present invention if the dies are made too tight, or with insufficient clearance, the separation of the parts 22 and 23 and the shims 34 may be noted during operation and the fault remedied. Or if one corner of the die is inaccurately made so as to throw an unusual force on one of the sets of operating links, that fault may also be readily observed during press operation, and corrected. It should be also understood that while the invention has ben described above with reference to the blank holding slide IS, the driving connections between the operating links it and the inner slide I6 are also of similar construction.

While the form of apparatus herein described constitutes a prefered embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. In a press of the character described, a frame, a slide reciprocably operable in said frame, means for operating said slide in one direction for a pressure operation including a pressure link, said slide comprising a main body having a surface facing generally in said direction and also having a separate lug to which said link is connected, and means acting under initial tension effective to normally force said lug toward said surface to hold said lug rigidly to said main body during pressing operation of the press within a predetermined safe working capacity of the slide and its operating means, but adapted to stretch and provide for relative movement of said lug away from said surface of the body when an overload is imposed.

2. In a press of the character described, a frame, a slide reciprocably operable in said frame, means for operating said slide in one direction for a pressure operation including a pressure link, said slide comprising a main body having a surface facing generally in said direction, and also having a separate lug, means adjustably connecting said link to said lug, and fastening means acting under initial tension to normally force said lug toward said surface to hold said lug rigidly to said main body during pressing operation of the press within a predetermined safe working capacity of the slide and its operating means but adapted to stretch during pressing operation and provide for relative movement of said lug away from said surface of the body when an overload is imposed.

3. In a press of the character described, a frame, a slide reciprocably operable in said frame and movable in one direction for a pressure operation, a plurality of sets of toggle links for operating said slide, said slide comprising a main body having a surface facing generally in said direction and having a separate lug for each t of toggle links and connected thereto, and rods extending generally in said one direction and acting under initial tension to normally hold said lugs rigidly to said surface of the main body during operation of the press Within the safe working capacity of the slide and its operating toggle means, but adapted to stretch and provide for relative movement of said lugs and body when an overload is imposed during pressing operation.

4. In a press of the character described, a frame, a slide reciprocably operable in said frame in a downward direction to effective position, means for operating said slide with a dwell in its movement including four sets of toggle links, said slide comprising a main body and four separate lugs each connected to a toggle link, and rods acting under initial equal predetermined tension to normally hold said lugs upwardly rigidly against a part of said body during operation of the press within a predetermined safe working capacity or the slide and its operating means, but adapted to stretch and provide for relative movement of said lugs and body when an overload'is imposed.

5. In a press of the character described, a frame, a blank holder reciprocably operable in said frame, means for operating said blank holder with a dwell in its movement including pressure links, said blank holder comprising a main body and separate lugs, a screw adjustably mounted in each lug, means guided in said blank holder and pivotally connecting said screw to one of said links, and rods acting under predetermined initial tension to normally hold said lugs rigidly to a part of said body which faces generally in the direction of pressure movement of the blank holder during operation of the press within a predetermined safe Working capacity of the blank holder and its operating means, but adapted to stretch and provide for relative movement of said lugs and body in the direction of blank holder movements when a predetermined excessive overload is imposed.

ARTHUR A. BYERLEIN.

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