RU41652U1 - PRESS FOR STRETCHING SHEET PARTS DOUBLE CURVITY - Google Patents

Abstract

The invention relates to the processing of metals by pressure, namely, sheet stamping of cladding parts of aircraft and allows to improve the quality of tightened sheet / parts by eliminating corrugation during tightening. The press for tightening sheet metal parts of double curvature contains a frame 8 and mounted on it with the possibility of horizontal adjustment and stationary in the vertical direction of the clamping jaws 2 and a lifting table 3 with a tightening punch 4 mounted on it, connected and. vertical displacement drive 5. Adjustable tensioning devices 6 are fixed on the lifting table 3 with grippers 7 of the lateral edges of the stretched sheet blank 1. The tensioning devices 6 are regulated, for example, by manual screw drives.

Description

The utility model relates to the processing of metals by pressure, namely, sheet stamping of cladding parts of aircraft, and can be used in the manufacture of car body parts, tank parts of the oil, gas and chemical industries, parts of household appliances, etc.

Known exhaust stamp for a double-action press (patent No. 2173569, IPC B 21 D 22/02, published 2001.09.20) containing a punch, a matrix with a U-shaped brake threshold and a clamp. The shape of the sheet metal part during stamping is determined by the punch, and the matrix with a U-shaped brake threshold and clamp serve to create lateral tension of the sheet blank, which prevents the appearance of corrugations.

A disadvantage of the known device is the insufficient degree of transverse tension of the sheet stock, which is especially noticeable in the initial stage of shaping, because due to the difference in the curvatures of the sheet stock in the longitudinal and transverse directions, the movement of the punch leads to tensile strains proportional to these curvatures, and the transverse curvature at the initial moment of shaping equals zero. A small degree of transverse tension of the sheet stock leads to the appearance of a tightening and the appearance of corrugations that cannot be completely straightened when the working surfaces of the punch and die of the known device are closed.

A known method of forming a close-fitting thin sheet double curvature parts (patent No. 1361813, IPC B 21 D 11/20, published 1995.11.20), carried out on a tight press with a tight punch mounted on a press lifting table, on the gentle slopes of which

inserts are placed that increase the longitudinal and transverse curvatures of the sheet blank. The inserts are used for pre-tightening the sheet blank. After heat treatment, the workpiece is calibrated by a tight punch without inserts. The presence of additional curvatures during preliminary tightening and the small size of deformations during calibration make it possible to reduce (it is not possible to completely eliminate) tightening of the workpiece and waviness (corrugations) in its shallow sections.

The disadvantages of this method are: limited technological capabilities (a positive effect can only be obtained for parts with flat sections; for dome-shaped parts, the known method is not suitable) and the insufficient degree of transverse tension of the sheet blank, leading to the appearance of a contraction and the appearance of waviness (corrugations).

A press is known for tightening sheet metal parts of double curvature (Groshikov A.I., Zaslavsky Yu.L., Gorbenko NN. Blanking and stamping work in aircraft construction. M: Oborongiz 1961; see Fig. 6.15a, p. 251. ), containing the bed and mounted on it with the possibility of horizontal adjustment and vertically stationary clamping jaws and a lifting table with a tightening punch installed on it, connected to a vertical displacement drive. The well-known press for tightening sheet metal parts of double curvature in its design is closest to the claimed utility model and is taken as a prototype. Figure 1 shows the sequence of tightening the sheet blank on the press adopted as a prototype: a - initial state, b - the emergence of a transverse tension, c - the formation of corrugations, where 1 is a sheet blank, 2 - clamping jaws, 3 - lifting table, 4 - tightening punch, In the initial state (Fig. 1 a), the flat sheet blank 1 is bent and fixed on both sides in the clamping jaws 2. When moving up the lifting table 3 with the tightening punch 4 in the sheet blank, longitudinal deformation strains e arise, the magnitude of which

depends on the angle y (Fig. 16) and can be calculated using the well-known formula (Gorbunov MN The technology of blanking and stamping in aircraft manufacturing. - M .: Mechanical Engineering, 1981. see p. 144, formula 9.2.)

where N 'is the tensile force in the central part of the workpiece (at γ = 0,

N is the tensile strength of the workpiece in an arbitrary section, determined by the angle γ,

μ is the coefficient of friction between the sheet blank and the tight punch,

e is the basis of natural logarithms.

Then from the expression

where b, s is the width and thickness of the sheet stock,

σ is the tensile stress,

K, n- module and rate of hardening of the workpiece material, we obtain the following formula

which after reductions and transformations will take the form

where ε ₀ is the tensile strain in the central section of the sheet stock (at γ = 0).

It can be seen from formula (*) that the strain ε (γ) increases with increasing angle γ and becomes maximum in the zone where the sheet blank passes from the tight punch. The deformation of the transverse tension of the sheet blank has the opposite sign with respect to the tensile strain and is numerically equal to half its magnitude. Thus, the deformation of the transverse tension is minimal in the Central part of the sheet stock,

maximum - in the areas where the sheet blank comes off the tightening punch and is equal to zero in the places where the sheet blank is fastened in the clamping jaws (the clamping jaws hold the sheet blank tightly and prevent the occurrence of transverse tightening). The adherence of the sheet blank to the tight punch when a transverse tightening occurs (Fig. 16) is unstable, therefore, the sheet blank goes into a more stable position (Fig. 1c) with the formation of longitudinal corrugations. The thinner the sheet stock, the earlier the transition from state (Fig. 16) to state (Fig. 1c) occurs. Smoothing the corrugations with a mallet on a sheet billet stretched over a tight punch becomes an almost impossible task when the thickness of the sheet billet, for example, from D16 alloy, is 0.6 mm or less. The corrugations on sheet blanks with a thickness of 0.8 mm or more lend themselves to manual editing (smoothing with a mallet), but the surface quality of the part from the impacts is significantly deteriorated.

A disadvantage of the known press for covering sheet metal parts of double curvature is the low quality of the resulting part.

The technical result, the achievement of which is proposed by the proposed utility model, is to improve the quality of stretched sheet metal parts of double curvature.

The technical result is achieved by the fact that in the press for tightening sheet metal parts of double curvature containing a bed and clamping jaws and a table fixed on it with horizontal adjustment mounted on it with vertical adjustment and a lifting table with a tightening punch mounted on it, connected to a vertical displacement drive, that the press is equipped with additional adjustable tensioning devices with captures of the lateral edges of the sheet part.

In figure 2. The claimed tightening press is shown (front, side and top view).

Here: 1 - a sheet blank, 2 - clamping jaws, 3 - a lifting table, 4 - a tightening punch, 5 - a drive of vertical movement, 6 - adjustable tensioning devices, 7 - clamps, 8 - a bed.

In the top view, the adjustable tensioning devices 6 are conditionally not shown, and their effect on the grippers 7 is shown in the form of transverse tension forces q.

Press for tightening sheet parts of double curvature contains a frame 8 and mounted on it with the possibility of horizontal adjustment and fixed in the vertical direction clamping jaws 2 and a lifting table 3 with a tightening punch 4 mounted on it, connected to a vertical movement drive 5. On the lifting table 3 are fixed adjustable tensioning devices 6 with grippers 7 of the lateral edges of the sheet metal blank 1. The tensioning devices 6 are regulated, for example, by manual screw drives.

The proposed press for tightening sheet parts of double curvature works as follows. The clamping jaws, depending on the dimensions of the manufactured part, are adjusted in the horizontal direction to the appropriate distance between them. The flat sheet 1 is bent and fixed at the edges in the clamping jaws 2. The lifting table 3 with the tightening punch 4 is lifted with the help of a vertical displacement drive 5 until the tightening punch 4 is touched with the sheet 1. The grips 7 are attached to the lateral edges of the sheet 1 and produce pre-transverse tension of the sheet stock 1 using adjustable tensioning devices 6, which are regulated, for example, by manual screw drives. The vertical displacement drive 5 is turned on, and, as necessary, during the shaping of the sheet stock 1 according to the tightening punch 4, additional lateral tension of the sheet stock 1 is carried out using adjustable tensioning devices 6. The tightening process is continued until the blank 1 is completely adhered to the tightening punch 4. B tightening process

the clamping jaws 2 are stationary, and the grippers 7 change their position in linear and angular coordinates from the lateral tension forces q applied to them from the tensioning devices 6, excluding the formation of corrugations when fitting parts.

On the OP-3 tight press equipped with six additional adjustable tensioning devices 6 with manual screw drives and grippers of 200 mm wide each, sheet blanks made of D16 alloy 0.6 mm thick and with original dimensions of 1500 × 2000 mm were wrapped (dimensions of the finished parts were approximately 1200 × 1200 mm).

The transverse tension of the sheet blanks during the tightening process completely eliminated the appearance of corrugations on the parts of the entire batch of 5 sets (5 right and 5 left), which are the fuselage skin of a light helicopter. High quality parts were obtained in the absence of additional manual fine-tuning.

Claims (1)

A press for tightening sheet metal parts of double curvature, comprising a bed and horizontally mounted on it with vertically adjustable clamping jaws and a lifting table with a tightening punch mounted on it, connected to a vertical displacement drive, characterized in that the press is equipped with additional adjustable tension devices with captures of the lateral edges of the sheet part.