DE2254269C2 - Rocking scissors - Google Patents

Description

characterized,

- That the counterforce (Fa ) acts in such a specific point (A) on the shear frame (1), which remains unchanged with changes in the operating conditions of the scissors, and

- That the radius of the unchanged point of application (A) up to the pivot point (K) of the shear frame (1) is greater than the radius (L \) of the center of mass (G) of the shear frame (1) by such a length (L _A ),

- That a cli the torque (Tc), caused by the inertia of the rotated or rotating masses of the shear frame (1), is compensated by the torque of the counterforce (Fa) y>

(Figs. 5,2,2).

Z vibrating scbere according to claim 1 with changeable counterforce, characterized in that

- That the size of the opposing force in adaptation to the throughput speed and the sheared Length of the material is changeable

3. Rocking scissors
marked.

according to claim 1, characterized

- That the counterforce is the resultant of several force components with different points of application is

4. rocking scissors according to claim
characterized.

or 2,

- That the counterforce (F _A ) on the Schsrrahmen fl) is exerted by a linkage (2-8), the

- is coupled to a rod (21) on the drive side,

- which is brought into its rest position by inertial masses (23),

- which in turn can be displaced in a radially guided manner by centrifugal forces in a rotor (24) arranged outside the shear frame (1) and rotating at a predetermined speed (N "),

- which the rod (21) axially penetrates, which is articulated to the inertial masses (23) is

(Fig. 2.4).

The invention relates to rocking scissors according to the preamble of claim 1.

Rocking scissors are used for shearing off pre-itimmers Lengths of a continuously fed web of material during the material passage. When shearing the knife speed is synchronized with the throughput speed of the material, so that a deviation in the sheared length is kept extremely small and a satisfactory shear surface is obtained will. The shear frame, which must be rigid enough to withstand the shear force, guides an oscillating movement, the load fluctuations, d. H. Fluctuations in the force of inertia »Eight, which varies from positive to negative values and vice versa, its amount proportional to that The square of the throughput speed, as will be explained further below, so that it corresponds to the The working speed of the scissors increases and the scissors and their drive unit accelerate or delayed, i.e. a shock-free swinging movement of the shear frame is prevented. The inertial force causes thereby an increasing beating of the bearings, so that their service life is reduced, and an increasing one Gap between the knife edges, which in itself worsens the shear quality.

It is therefore difficult to increase the operating speed of vibratory scissors tu, so generally a flow rate of about 120 m / min is considered as the upper limit. Therefore, when installing rocking shears in a high-speed road, e.g. B. in a plating plant with a throughput speed of up to 120-180 m / min, it is common to reduce the line speed to a value of at most the shear speed or, alternatively, the shears separately! from the street and do the shearing only after the material to be sheared has already been wound up once in a winding device.

Rocking scissors have already become known ivgl. Journal "Bänder Sheet Metal Pipes" Düsseldorf, 13 (1972) No. 5, pp. 253-255), in which, since the loads on the individual structural elements are vibrating loads are involved, extreme shocks are mitigated by a damping, the one has double-acting air cylinder in which the air is compressed in the end positions of the oscillating movement is to absorb the blows during the reversal of movement and the acceleration of the masses after to support repentance. The degree of damping can be adapted to the operating conditions.

This known prior art is considered to be inadequate in the case of higher claims from the following Establish:

- can be recognized by a balance of masses ^ resp. Inertia torques not thought of;

OO

- The point of application, direction and amount of the opposing forces are left open, i.e. undefined, and

- the opposing forces apparently only limited in time, since they are only used to absorb blows the reversal of motion are provided, so not ϊ during the entire shear stroke.

It is therefore the object of the invention to design rocking shears of the type mentioned above in such a way that an improved effect of the compensation device is achieved.

According to the invention, this object is achieved in principle by the teaching according to the characterizing part Part of claim 1, while claim 4 indicates a practical implementation.

The invention is based on the recognition that the maximum amplitude of the counter force to balance the inertial force and the inertia torque inversely proportional to the sheared length and proportional 2t to the square of Durchlaufge-> is speed, which is why! Olgenden two conditions of the counterforce erf '.' It must be:

1. The counterforce must be 2> speed and sheared length can be adjusted; and

2. the counterforce must have at a location which lies at a value determined by the ratio of inertial torque to inertia force distance above the center of mass of the punk u> shearing frame their point of attack.

According to the invention, the load fluctuations (fluctuations in inertia force and inertia torque), which make it difficult to increase the working speed of rocking shears, kept small, so that the associated throughput speed of about 120 m / mm, which was previously considered as the upper limit was increased to about 200 m / min without changing other equipment of the production line 4 « which allows a significant increase in the productivity of the entire production line. Even if the production line speed is not very high, the invention is advantageous in that when they have a smooth *> over the entire shear stroke Oscillation movement of the scissors with minimal impacts and noises, so that the service life of the Schei e is extended considerably.

The invention is explained in more detail, for example, with the aid of the drawing. Cs show:

1 shows the forces acting on a shear frame,

F i g. 2 shows the partial view of an embodiment of the rocking scissors according to the invention;

Fig. 3 is a sectional view III-III of Fig. 2; «

FIG. 4 shows in detail an exemplary embodiment of the compensating device belonging to the rocking scissors according to FIG. 2; FIG. and

5 is a schematic perspective view of a possible drive system for rocking shears.

First, F i g <5 is explained in more detail:

A crankshaft 27, which is driven by a drive (not shown), has eccentric parts K and L, which are 180 ° out of phase with one another. With the eccentric parts / C, a gate ^ shear frame 1 is connected, on which an upper shear blade b \ is attached, while the eccentric parts L are connected to a linkage or gear 28, 29 which carries _{a lower cutter Zj 3.} The construction is chosen so that the lower cutter bi performs a vertical movement when it hits the swinging movement of the upper cutter b \ , while it slides within the shear frame 1, and a material web 30 (z. B. band steel) in shears off in a position in which it meets the upper knife b \ .

A shaft 32 with cranks Q and N is connected to the shear frame 1 via a connecting rod 31. To adapt the oscillation speed of the knife to the feed speed of the steel strip 30 at the time of shearing, a synchronizing device M, the eccentricity of which is adjustable, is connected to the crankshaft 27, the synchronizing device M also being coupled to the crank N via a connecting rod 33 so that the movement the crank N on the shear frame 1 via the crank Q and the connecting rod c; 31 is transmitted.

The movement of the Scherrahp -'- ns 1 is explained in Fig. 1. The upper knife b · and the center of mass C perform movements along curves that are indicated by a dash-dot line and a two-dot chain line in F i G. 1 are shown.

With

X, Y = orthogonal coordinates in horizontal or in

vertical direction
ε = angle of inclination of the shear frame,

the movement of the center of mass G can be approximated by the following formulas:

x = -Vii

y = - »1

ε = C _n sin ω '.
with * o, younde "= maximum amplitude in each case

provided that ω = const

x " ~ (essentially) sheared length L y" = constant (independent of L).

The approximation accuracy of χ and e is high, ie the approximation errors are less than 2 - 3%. The approximation accuracy of y is not high, but the influence of vertical movement is small and the error of y is negligible.

Therefore, with

/ W = mass of the shear frame,
/ = Moment of inertia

the forces of inertia Fa and Fy in the horizontal and vertical directions and the moment of inertia T ₃ are expressed by the following formulas:

F ₀ = -MX = ω ^ι Μχ, T ₀ = -W = ω ^ί ίε.

Forces Fb, Fr ₂ corresponding to these inertia forces a Fy and the inertia torque T _G are increased

transmit the drive and cause the difficulties described above without compensation.

With a counterforce F, \ that acts on the upper section of the shear frame (at a point of application / t at a distance L. \ from the center of mass G), we get:

- Fg ' L] ■ cos cF, ■ L ₁ · sin c + T ₁ , - F _A (L \ + L _A ) cos c _ra F ₀ Li + Γ ₍ , - F ,, (L ₁ -f L, _t ) Lf cos f Zj

^ F _<; + F ₈ -F ₁ .

With complete force and torque compensation by the counterforce, Fb = Fr: = O.

For this purpose, the following conditions must be met, derived from the equations above consequences:

F, = F ₁ , = ω ¹ Mx.

F ₁ ,

Ic Mx

Let us now consider the maximum value of the inertial force Fc .
With

Ns = speed of the main shear shaft, V = throughput speed, L - sheared length,

arises because x _o proportional to L (as described above by synchronizing the speed) and Xq is proportional to _ε ο by movement of the shear frame. and further, since the speed Ns of the main shear shaft is proportional to VIL and the angular speed ω of the shear frame is equal to the speed Ns of the main shear shaft up to a factor of:

MaxF ,, ~ M · γ.

The maximum value of the inertial force is therefore proportional to the square of the flow rate V and inversely proportional to the sheared length L. Furthermore, the point of application A is stationary (La = const), since Eo is proportional to x _o , and therefore does not need to be changed, even if the sheared length L changes. It can therefore be seen that by the action of the opposing force F _A equal to the inertia force Fc. At point A, the forces acting on the shear frame are fully balanced within the framework of the above approximation calculation and no more load fluctuations reach the drive.

From the previous explanation it can be seen that that the counterforce

Fa - co ² ■ M ■ χ

must meet the following two conditions:

1. The counterforce is a straightening force that is proportional to the stroke χ of the shear frame and is constantly directed in the λ direction. and its maximum varies proportionally to V ² ZL

2. The point of application of the counterforce is stationary and is at a distance

The conditions set out above apply to the optimal value of the counterforce, while the actual opposing force exerted to obtain the desired result in a usable approximation, something of these conditions may differ.

If, due to any construction difficulties, it is impossible to arrange the point of application A at the location specified above, several forces can act with such points of application that the point of application of the resulting force still coincides with the point of application A and the desired amount of A is obtained.

Let us now consider a pair of rocking scissors with a compensating device, which are an embodiment of the invention is described with reference to FIGS. 2-4.

A shear frame 1 is connected to one end of connecting rods 2 on opposite side arms. The other end of each connecting rod 2 is connected via a pivot pin 3 to one end of a lever 4 which is keyed onto a shaft 5 which is rotatably supported in a bracket 5A. One end of a lever 6 is keyed onto the shaft 5 and the other end is connected to one end of a lever 8 via a pivot pin 7. The other end of the lever 8 is articulated to a bearing journal 10a at the upper end of a rod 21 (see FIG. 4) which is carried by a holder 9 so as to be axially displaceable.

In Fig. 2, the rocking scissors are drawn in a position in which the holder of the upper knife lowered and the holder of the lower knife

La = TcJFg =
away from the center of mass

Oscillating mechanism, so that the upper knife b \ and the lower knife & lie against one another, ie the rocking scissors are in their shear position - and connection point A between the shear frame 1 and the connecting rod 2 on an elliptical curve which is shown in FIG. 2 on an elliptical curve, which is indicated in FIG. 2 by a two-dot chain line. This movement moves a rod 21 (cf. , 6 and 8.

According to FIG. 4, the rod 21 is connected to the upper section of the shear frame (not shown in FIG. 4) via the rods 2-7 in FIG. 2 connected. Inertial masses 23 are connected to rod 21 by connecting rods 22 for sliding movement in a rotor 24. The rotor 24 is supported by bearings 25 and driven from the outside via a gear 26 at a speed Nu . When the rod 21 oscillates in the axial direction mediated by the oscillatory movement of the shear frame, the inertial masses 23 slide in and out of the rotor 24. However, since the rotor 24 rotates at the same time at the speed Nw , a centrifugal force acts

7 8

every inertial mass eifi which has such an opposing force on the one with

associated connecting rod 22 exercises that it _M ■ ₌ total mass of inertia masses 23,

is held perpendicular to the rod 21. The output _χ _ stroke of the rod 21.
force finder rod 21, d. L · the counterforce is calculated

to: ϊ The counterforce F _w is proportional to the stroke X _s

oo And varies in amount according to the speed

F _w = M _b ( j .ν, / Vivdes rotor 24, which is why they use the above

\ 60 J conditions for the opposing force are sufficient.

For this purpose 4 sheets of drawings

Claims (1)

Patent claims: 1, Schwitig scissors with - a shear frame, which oscillates in synchronism with the throughput speed of the material to be sheared off, - two knives that lie against each other within the shaving frame and detach from each other, - a device for operating the shear frame and the knives, and - A compensation device for applying a counterforce to the frame of such size and direction that it caused the shear frame to oscillate linear inertia forces are compensated,