RU2360772C1 - Rolled sheet shears - Google Patents

Abstract

FIELD: mechanics.

SUBSTANCE: proposed shears comprises lower knife and movable upper knife interacting with the former and furnished with cutting edge formed by circular arc and articulated with the driving lever link and head arranged to move in vertical guides of the fixed base. The movable lower knife is articulated with the knife head that moves in vertical guides and with the driving lever link on the side opposite to its axis of rotation. The cutting edges of both knives are formed by circular arcs, the upper knife cutting edge centre of curvature, on the side of driving lever link, being located on the continuation of axis that passes through the hinge of the driving lever link and hinge. The centre of curvature of the cutting edge of lower movable knife, on the side of the knife head linked up with it, is located on the continuation of axis that passes through the hinge jointing the lower movable knife with its head and driving lever link together. The radii of circular arcs that form the cutting edges of both knives are selected proceeding from the condition of their identity required to allow a permanent overlapping of the shears knives in compliance with the enclosed computation formulae.

EFFECT: increased cutting angle, permanent overlapping.

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Description

The invention relates to mechanisms for processing materials by pressure.

Known scissors for cutting rental [Korolev A.A. Mechanical equipment of ferrous and non-ferrous metallurgy workshops. M .: Metallurgy, 1976, pp. 245-250], containing a bed, a fixed knife beam and a movable knife beam installed with the possibility of movement in the guides of the bed and connected with the eccentric shaft of the drive.

The disadvantages of this device are the large overall dimensions and complexity of the design, the need for sharpening the cutting edge of the knife, the inconstancy of overlapping knives.

Known scissors for cutting sheet material [USSR author's certificate No. 1655661, B23D 15/00, 1991] containing a base, a fixed knife fixed thereon and a movable knife interacting with it, mounted on a slide movably mounted on the base bracket by means of a holder made in in the form of a plate with a groove and a cylindrical protrusion and equipped with a position lock, which allows fixing the holder together with the movable knife in two positions, providing the opposite cutting angle. In this case, you can change the cutting direction along the edge of the fixed knife to the opposite.

The mechanism is driven by an eccentric pivotally mounted on the base bracket and forming a higher pair with a slider.

The disadvantages of these scissors are the design complexity, unreliable operation, the inconvenience of adjusting the gap between the knives by maneuvering the bracket in the horizontal plane with respect to the base, the need to sharpen the cutting edge of each knife, the large unevenness of the torque on the drive eccentric, the inconsistency of the knife overlap, significant cutting forces.

Closest to the proposed invention are scissors [patent RU 2025223 C1, 12/30/1994, class. B23D 15/06], comprising a case with a fixed knife fixed thereon and a movable knife interacting with it, connected with a slider movably mounted in the vertical guides of the case and driven by an eccentric shaft pivotally mounted in the upper part of the case, the movable knife being pivotally connected to the slider and the neck of the eccentric shaft, and its profile is formed by arcs symmetrical with respect to the axis passing through the axis of the slider and the eccentric shaft, while the lower fixed knife is fixed to the housing one vertical nym screw in the middle and two horizontal thrust adjustment screws.

The disadvantage of this invention is the lack of technological capabilities, in particular the relatively small clearance between the knives and the cutting angle, limiting the thickness of the material being cut.

The aim of the invention is to remedy these disadvantages and increase technological capabilities.

This goal is achieved by the fact that in the scissors containing the lower knife and the upper movable knife interacting with it, made with a cutting edge formed by an arc of a circle, and pivotally connected to a drive link and a slider mounted with the possibility of movement in the vertical guides of the fixed base, the lower the knife is made movable and pivotally connected to a slider mounted with the possibility of movement in vertical guides and to a drive link with a link opposite to its axis of rotation sides, and the cutting edges of the upper and lower movable knives are formed by circular arcs with the center of curvature of the cutting edge of the upper knife on the side of the drive link on the axis extending through the hinge of the drive link and the hinge connecting the upper movable knife to the slider, and the center of curvature of the cutting the edges of the lower movable knife - from the side of the slider connected to it on the continuation of the axis passing through the hinge connecting the lower movable knife with the slider, and the hinge of the drive link, When this radii of circular arcs forming the cutting edges of the upper and lower movable cutters are chosen from the condition of equality for constant overlap between the blades of scissors.

A diagram of the shears for cutting sheet metal is shown in the drawing.

The device consists of a fixed base 1, on which the drive link 2 is rotatably mounted and pivotally connected to the upper movable knife 3, which is pivotally mounted on the slider 4, reciprocating along the guides in the base 1 and the lower movable knife 5, connected with a drive link 2 with a hinge located on the opposite side from the axis of rotation of the drive link and pivotally mounted on a slider 6 that moves in vertical guides warping 1. The cutting edges of the upper 3 and lower 5 movable cutters formed by circular arcs of radii R _1, R _2, respectively. The center of curvature of the cutting edge of the upper movable knife (point M) is located on the side of the drive link 2 on the continuation of the axis passing through the hinge of the drive lever link, and the hinge connecting the upper movable knife to the slider 4, and the center of curvature of the cutting edge of the lower movable knife (point M ') is located on the side of the slider 6 connected to it on an extension of the axis passing through the hinge connecting the lower movable knife to the slider 6, and the hinge of the drive link 2.

The position of the points M and M 'having connecting rod curves with straight sections is determined by one of the methods for synthesizing a symmetrical linear guide mechanism known in the theory of mechanisms and machines. The lengths of the straight sections of the connecting rod curves L ₁ and L ₂ are equal to each other and equal to the width of the sheet of cut steel, and are determined by the expressions:

where r ₁ - the radii of the cranks of the drive link, m;

b is the distance between the hinges of the cranks of the drive link and the corresponding sliders, m;

φ ₁ - the angle of rotation of the drive link, corresponding to the beginning of the working stroke of the scissors, deg;

r ₂ , r ₃ - the distance from the hinges of the cranks of the drive link to the centers of curvature of the cutting edges of the upper and lower movable knives, respectively, m

The distance r _{2 is} determined from the condition of the best approximation of the trajectory of point M to a straight line, equating its coordinates in the extreme position at φ ₁ , corresponding to the beginning of the working stroke of the scissors, and in the middle position at φ ₁ = 0:

From the condition that the lengths L ₁ and L _{2 of the} straight sections of the connecting rod curves are equal, an unknown parameter r _{3 is} determined:

r ₃ = 2b + r ₂ .

The rolling of the upper knife 3 with respect to a straight line parallel to the rectilinear portion of the trajectory of point M is ensured for any R ₁ , but from the condition of the minimum sliding of the knife along the cut sheet metal, the radius R ₁ is chosen so that the length of the arc of a circle forming the edge of the knife 3 is equal to the width sheet cut steel, that is, L ₁ . Subject to the minimum slip condition, the radius of the arc of a circle forming the cutting edge of the upper movable knife is determined by the formula:

The minimum slip condition must be met for rolling the lower movable knife 5, and since the radius R _{2 is} also chosen so that the length of the arc of the circle forming the edge of the knife 5 is equal to the width of the sheet to be cut, the radius R ₂ can be determined by the formula:

The constant overlap between the knives 3 and 5 is ensured from the condition that the lengths of the straight sections of the corresponding connecting rod curves are equal L ₁ = L ₂ and provided that the radii of the arcs of the circles forming the edges of the knives are equal, R ₁ = R ₂ .

Scissors for cutting sheet metal work as follows.

During rotation of the drive link 2, the movable knives 3 and 5 diverge to the extreme upper (for knife 3) and lower (for knife 5) positions, which corresponds to the idle speed of the knives and the movement of the guide points M and M 'along the curved sections of the corresponding connecting rod curves, at the same time, a cut sheet is introduced into the resulting solution of knives 3 and 5. With further rotation of the drive link 2, the movable knives converge, making a complex movement - a rolling cut, while the sheet material is cut with a constant overlap of the knives 3 and 5 and at a constant maximum cutting angle. At this point, the points M and M 'move along the corresponding rectilinear sections of the connecting rod curves parallel to the surface of the sheet being cut. Further movement of the drive link 2 again dissolves the knives 3 and 5, and the cut sheet is introduced into the resulting solution.

Claims (1)

Scissors for cutting sheet metal, containing a lower knife and an upper movable knife interacting with it, made with a cutting edge formed by an arc of a circle, and pivotally connected to a drive link and a slider mounted for movement in the vertical guides of the fixed base, characterized in that the lower knife is movable and pivotally connected to the slider mounted with the possibility of movement in vertical guides and to the drive link with the opposite from its axis in the rotation of the side, and the cutting edges of the upper and lower movable knives are formed by circular arcs with the center of curvature of the cutting edge of the upper movable knife on the side of the drive link on the axis extending through the hinge of the drive link and the hinge connecting the upper movable knife to the slider, and the center the curvature of the cutting edge of the lower movable knife - from the side of the slider connected to it on the continuation of the axis passing through the hinge connecting the lower movable knife with the slider, and the hinge drive of the link is, the radii of the arcs of circles forming the cutting edges of the upper and lower movable cutters are chosen from the condition of equality to ensure continuity between the overlapping knives and scissors are defined by the formulas

,
Where

,
where r ₃ = 2b + r ₂ ,
where R ₁ , R ₂ are the radii of the arcs of circles forming the edges of the upper and lower movable knives, respectively, m;
r ₁ is the radius of the crank drive link, m;
b is the distance between the hinges of the cranks of the drive link and the corresponding sliders, m;
φ ₁ - the angle of rotation of the drive link, corresponding to the beginning of the working stroke of the scissors, deg;
r ₂ , r ₃ - the distance from the hinges of the cranks of the drive link to the centers of curvature of the cutting edges of the upper and lower movable knives, respectively, m