US3024676A - Hydraulic presses - Google Patents

Description

March 13, 1962 E. HOWAHR ET AL HYDRAULIC ERESSES Filed Nov. 19, 1959 IN VE N TORS INA/$2.10}! CH/M PAH/IKE;

BY ERICH H0 WA HR ATTaR/VEYS United States Patent C) 3,024,676 HYDRAULIC PRESSES Erich Howahr, Dusseldorf, and Hans-Joachim Pahnke,

Dusseldorf-Bath, Germany, assignors to Maschinenfabrik Sack G.m.b.H., Dusseldorf-Ram, Germany Filed Nov. 19, 1959, Ser. No. 854,099

Claims priority, application Germany Nov. 28, 1958 3 Claims. (Cl. 78-42) Hydraulic presses, in particular forging presses with underfloor drives, that is presses which have a driving mechanism which operates the movable press platen from below the lower platen usually have frames with either two or four supporting columns and the driving mechanism usually includes either one or three hydraulic rams. In such presses either the two or the four columns together with a cross-beam which carries the upper platen or upper die are movable relative to a fixed cross-head which carries a lower platen or a lower die. The movable parts are guided in guide sleeves provided on the fixed cross-head.

With this type of press construction, eccentric loads on the press have a very disadvantageous effect on the guide sleeves which guide the columns. These guide sleeves are usually not adjustable, so that they are subject to very rapid wear. With progressive wear of the guides, the press becomes more and more inaccurate in use; it also becomes progressively less stable and will oscillate during operation.

Owing to the heating up of the parts of the press during forging, it is necessary to provide ample clearances between all the guide sleeves and columns when the press is constructed, so that these parts will not jam as a result of thermal expansion. These clearances, however, tend to make the movable parts of the press take up an oblique position relative to the fixed parts of the press when acted upon by eccentric forces; this leads to uneven stresses on the guide surfaces.

In four-column presses, the axes of the columns are usually arranged not at the corners of a square but at the corners of a long rectangle, so that the distance between the columns transversely to the direction in which the material being forged is passed into or through the press is greater than the distance between the columns in that direction. Consequently the ratio between the distance between the columns and the length of the guide sleeves transversely to the said direction is particularly unfavourable. If the press is eccentrically loaded in the direction of the greater distance between the columns, the movable part of the press frame containing the columns moves into a position oblique to the fixed cross-beam. Additional bending forces are thereby exerted on the press columns through the guide sleeves. The magnitude of these bending forces is not controllable because the eccentricity of the forces occurring during pressing cannot be limited. For this reason, the columns of forging presses are usually designed to carry relatively low stresses, that is to say they have a high factor of safety. In spite of the resulting large cross-sectional areas of the columns, breakage of the columns may occur as a result of eccentric loads on the cross-heads which carry the dies. This is especially so in the case of presses having driving mechanisms situated below the lower press platen.

The object of the present invention is to overcome or at least reduce the tendency of the relatively movable parts of presses to move into oblique positions and so to jam and cause excessive wear.

With this end in view, according to the present invention, a hydraulic forging press comprises a cross-head and two chain-link shaped members forming two parallel pairs of columns of rectangular section which are slidable "ice longitudinally relatively to the cross-head, the cross-head carrying one platen or die and the other platen or die being carried on a cross-beam extending between two adjacent ends of the link-shaped members, one pair of columns being guided on the cross-head by their two faces which face towards each other and by an adjacent face on each column and the other pair of columns being guided on the cross-head only by their two faces which face towards each other.

A four column hydraulic press in accordance with the invention and having a driving mechanism situated below the lower press platen is illustrated by way of example in the accompanying drawings in which:

FIGURE 1 isa side view of the press partially in section;

FIGURE 2 is -a vertical section on the line II--II in FIGURE 1; and,

FIGURE 3 is a horizontal section on the line III-III of FIGURE 1.

The movable frame of the four column press comprises tension members 1 and 2 shaped like the links of a chain. These members, which in effect form four c01- umns extend over the top of a cross-beam 7 which carries an upper platen or die 17 and are connected to the beam 7 by a transverse piece 8. The piece 8 lies on the upper surface of the tension members '1 and 2 which are clamped between it and the cross beam 7. The crossbeam 7 and the tension members 1 and 2 have cylindrical contact surfaces 19. At their lower ends, the tension members 1 and 2 are connected to each other by a light transverse member 9. The columns of the tension members 1 and 2 are square in section, and they are thus better able to take up the bending stress caused by an eccentric load P or P, (FIGURES 1 and 2) than other presses which have columns of the same cross-sectional area but circular in section. In addition, all guide surfaces may -be made adjustable.

In such a press with a driving mechanism situated below the lower platen and in which four columns of rectangular cross-section are disposed at the corners of an elongated rectangle and each of the closer pairs of columns form the components of a frame which constitutes a tension member, the two frames being connected by a cross-member carrying an upper platen or die, each of the two frames 1 and 2 is constructed as a single piece in the form of a chain link.

Replaceable guide bars 3, 5 and 6 are provided on the cross-head 16 between the latter and the frame 2, and replaceable guide bars '4 are provided on the cross-head 16 between the latter and the frame 1.

A gap may therefore be left between the cross-head 16 and the columns of the frame 1 to allow the expansion of the fixed cross-head 16, without bending forces being exerted on the columns of the frames 1 and 2, Consequently the tensile strength of the material of the columns can be fully utilised for withstanding tensile forces in the columns with the result that the whole frame of the press becomes lighter in construction.

The press is operated by two hydraulic rams 10 and 11, cylyinders 14 and 15 of which are let deeply into the fixed cross-head 16 and pistons 12 and 13 of which are supported directly on the lower parts of the tension members 1 and 2. The centres of thrust of the pistons 12 and 13 are at the centres of the chain link shaped frames 1 and 2. By using a known synchronised hydraulic control, the press components 1, 2, 7, 9 and 16 are moved relative to each other in such a way that they do not become obliquely placed with consequent jamming of the movable parts 1, 2, 7 and 9 of the press. With this synchronised hydraulic control eccentrically acting forces P and P are compensated for by different loads P and P on the two pistons 12 and 13. Bending stresses are thereby largely avoided also in the tension member 2 the columns of which are guided on three faces by the guide bars 3, 5 and 67 As well as the two hydraulic rams 10 and 11, the press may have a third ram which is arranged at the centre of the cross-head 16 with a piston which is supported on the cross-member 9, provided that the two rams 10 and 11 ensure that the parts 1, 2, 7 and 9 of the press are guided accurately in a straight line. The crossmember 9 which transmits the force from the pressure of the third cylinder must then be so strong that it can transfer the force acting on it to the two tension members 1 and 2 without being deformed. In addition, the centres of force or the effective centres of the two rams which effect the straight line guidance can be displaced inwardly or outwardly relative to the centres of the chain link shaped frames so that the forces produced by these rams also are transmitted to the frames through the crossmember 9 which must then be made especially strong.

We claim:

1. A hydraulic forging press, substantially with underfioor driving means, comprising a stationary lower crosshead, two parallel pairs of columns vertically slidable relatively to the cross-head, an upper cross-beam connecting the upper ends of the two pairs of columns, one platen or die on the cross-head and one platen or die on the-cross-beam, the columns having rectangular crosssection and each pair of columns forming a chain linkshaped unit of rectangular cross-section, the columns of one pair being in contact with guide planes on the stationary cross-head by their two faces facing each other and by the adjacent faces, the columns of the other pair being in contact with guide planes on the stationary crosshead by those of their faces only which face each other.

2. A press according to claim 1, the driving means of which comprises two hydraulic pressure devices, one disposed between the columns of each pair, each cylinder of said devices being at least partially disposed inside the stationary cross-head and each piston of said devices being fixed to the lower end of one of said chain link-shaped units.

3. A press according to claim 2, the two rams further provided with means for controlling synchronously in such a way that differences in the forces applied to the platens on each side of a central plane occurring between the pairs of columns are compensated by suitable differences in the forces acting on the pistons of the two rams.

References Cited in the file of this patent UNITED STATES PATENTS D. 120,235 Bolling Apr. 30, 1940 FOREIGN PATENTS 459,340 Canada Aug. 30, 1949 7,679 Denmark July 17, 1905 41,979 Sweden Nov. 2, 1915 522,065 Great Britain June 7, 1940

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