CA2007848A1 - Shear for shearing laminar elements, or the like - Google Patents

Abstract

"SHEAR FOR SHEARING LAMINAR ELEMENTS, OR THE LIKE"
Abstract The shear for shearing laminar elements or the like comprises a pair of blade-holders, which, during the shearing operation, are stressed by two forces (Fx and Fy) perpendicular to each other and having as their resultant, the force FR. At the shearing time, both of said blade-holders are supported in an inclined position, so that their main axes come to coincide with the direction of said resultant force (FR). From the above, the possibility results that the mass of the inclined blade-holder can be reduced even by 50% relatively to the mass of a traditional blade-holder which is not inclined, without the stiffness of said blade-holder, relatively to the shearing forces, being endangered.
The invention can be applied as well to quillotine shears and to rotary shears equipped with roll blade-holders.

Description

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1 .

"SHEAR FOR SHEARING LAMINAR ELEMENTS, OR THE LIKE"
The present ;nvent;on relates to a shear for shearing laminar elements, or the like, ~hich shear comprises at least one pair of blade-holders and the relevant blades relatively mobile according to parallel straight lines spaced apart from each other by a distance computed as a function of the thickness and of the nature of the material to be shorn, with said blades being provided with cutting edges at which, at the shearing time, a pair of mutually perpendicular forces Fx and Fy are applied, with this latter ~orce Fy acting alond a straight line perpendicular to the plane on which the material to be shorn is laid, according to which straight line the movement takes place of the blade-holder.
At present, an extremely wide range of shearing machines are available from the market, which are different from one another according to the structure of the component organs.
However, from the standpoint of the shearing action, all of the shears can be substantially subdivided into two types, i.e., the shears of the guillotine type, and the shears of the rotary type.
The tirst type of shear, i.e., the guillotine shear, comprises a blade movable on a vertical plane and cooperating, at the shearing line, with a stationary counter-blade.
The second type of shear, i.e., the rotary shear, comprises a pair of blades translating in synchronism along a circular trajectory, so as to cooperate ~ith each other at the shearing line.
In both of the above types of shears, the shearing 2.

action takes place substantialLy o~ing to the ~ovement of sliding of the one blade relatively to the other one according two directions parallel to each other and s;multaneousLy perpend;cular to the plane on ~hich the material to be shorn is laid.
During the shearing, the distance betueen the straight l;nes according to ~h;ch the two blades move relatively to each other should remain as constant as possible, and, in order to attain this result, in the shearing mach;nes kno~n from the prior art, the blade-holders are g;ven a stiff structure by means of suitable strengthening elements, so as to counteract the t~o mutually perpendicular forces Fy and Fy. These strengthen;ng elements should display the maximum value of their moment of inertia in the direction of the relevant force, and they cause the relevant blade-holders to become particularly large and heavy.
This circumstance creates considerable hindrances to the ;ncroase in shearing machines throughput, a matter of fact, this, ~hich is particularly burdensome in case of shears of rotary type, and severely jeopardizes the productivity rate of the production l;nes ;n which these shearing machines are installed.
In order to obviate this dra~back, one could think of replacing the presently installed motor means ~ith other, more po~erful, motor means ~ith simultaneous~y generally strengthening the shear;ng machine, so as to enable the mach;ne to exceed determ;ned operating speeds.
Such a solut;on ;s not recommended, in that a more po~erful motor means is also a more ~eighing one from a dynamic viewpoint, and therefore the added po~er ~ould be .
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most used in order to overcome its own inertiaL reactions during the acceleration and deceleration steps.
The purpose of the present invent;on is of providing a shear, in particular of the rotary type, which is capable of obviating the above sa;d draubacks, i e., ;s capable of displaying -- at the shearing time -- a higher stiffness of the blade-holders than as offered by the blade-holders of the traditional shears with the mass of said blade-holders being the same, i.e., a shear in which, with the stiffness of the blade-holders -- at the shearing time -- being the same, the mass of said blade-holders is considerably smalLer than of the blade-holders the traditional shearing machines are-equipped with, thus making it possibLe the operating speed of the shear, and therefore the throughput of the l;ne in which the shear is possibly installed, to be considerab~y increased.
Such purposes are achieved by a shear for shearing lam;nar elements, or the like, of the initially defined type, characterized in that both of said blade-holders .: ~
are given such a structure, and are so constrained, that they show the maximum va~ue of their moment of inertia at bending according to one direction only, with said direction being coincident with the direction of the force F~ which is the resultant from the vectorial composition of the forces F~ and Fy The advantages resulting from the present invention essential~y consist in that, inasmuch as said invention makes it possible light, powerful shears to be used, the presently reached productivity limits can be overcome, with considerable benefits for the production l;ne of which the shearing machine possibly constitutes one of 4.

the component elements.
The ;nvention is d;sclosed for merely exemplifying, non-limitative, purposes, by referring to the figures of the hereto attached drawing tables, in which:
Figure 1 shows a schemat;c side viev of the cutting elements of a traditional shear;
Figure 2 shows a perspective view of a correctly shorn edge of a metal sheet;
Figure 3 shows a schematic side vie~ of the shear-holder of a shear of the rotary type accomplished according to the instant invention, sho~n during the shearing step;
F;gure 4 shows a schematic v;e~ of the cutting elements of the shear according to the instant invention;
Figure 5 shows a schematic side view of a rotary shear equipped w;th blade-holders of roll type, accompl;shed accord;ng to the teachings of the present ;nvention, Figure 6 shows a schematic v;ew of a rotary shear ~ith roll shear-holders of tradit;onal type.
It should be observed here that the figures and the graph;c representations of the concerned forces have not been str;ctly made ;n scale, ;n order to improve the understanding of the invention.
In order to better understand the technical problem solved by the present invention, the dynamics of the shearing action performed by the traditional shear are illustrated first, with the aid of Figures 1 and 2.
The cutting elements of a shear traditionally comprise an upper blade-holder 1 ard a lower blade-holder 2, respectively supporting an upper blade 3 and a lower 8~3 5.

blade 4, suitable for operating, e.g., on a metal sheet 5 of thickness "s" The blades 3 and 4, which usually are of the added type in order to make it possible them to be rapidly replaced when they are worn out, are respectively provided with straight cutting edges 6 and 7 so lengthwise inclined, as to favour the cutting action The lengthwise deve~opment of the cutting edges 6 and 7 and their inclination along said lenghtwise development are not visible in the figures.
During the shearing action the blades 3 and 4, as well as their respective blade-holders 1 and 2 move relatively to each other (arrows "F") along parallel straight lines 10 and 10A, spaced apart from each other by a distance "d" and substantially perpendicular to the plane on which the metal sheet 5 is laid The distance "d" is preset by those skilled in the art as a function of the thickness "s" of the metal sheet, and is generally a function of said thickness according to the well-known relationship:
. . .
d = (from 0 07 to 0.10).s wh;ch opt;mises the shearing action.
The respect of such a distance "d" is essential in order that a correct shearing -- i.e., without burrs being formed --, as shown in figure 2, may be obtained In said Figure 2, one can substantially see a first, peripheral section 8, of a height substantially equal to 1/3rd of the thickness "s" of the metal plate, in which the cutting took place by plastic deformation of the metal caused by the cutting edges 6 and 7, and a second portion 9, in which the cutting took place by slipping/fracture of the molecular planes, hence without ~ v(~784~

any burrs be;ng formed.
If for the distance between the blades "d" a wrong value is selected, w;th the thickness of the material to be shorn being not taken into due consideration, negative phenomena occur, which negatively affect the cutting action Such negative phenomena are not described herein, in that they are well-known to those skilled in the art.
It results that it ;s necessary that during the cutting action said distance "d" should rema;n as constant as possible along the whole length of the cutting edges 6 and 7, a feature which cannot be achieved if, e.g., a bend;ng occurs of the blade and of the blade-holder under the effect of the shearing stresses. In order to obviate such a dra~back, in the shears known from the prior art, whether of guillotine or of rotaty type, both of the blade-holders are therefore given a part;cular~y stiff structure both on the vertical plane, in order to counteract the vertical force Fy~ and on the horizontal plane, in order to counteract the horizontal force Fy.
The vertical force Fy has an extremely h;gh value and therefore tends to deform the blades by causing them to bend on a vertical plane. However, relatively high values of such a bending do not endanger the cutting, because the blades compensate for them by means of the;r natural downwards movement along a vertical trajectory, according to the direction of the arrow "F". The horizontal force Fx is of a relatively low value, but it tends anyway to deform the blades by causing them to bend on a horizontal plane parallel to the plane on which the metal sheets is laid.
However, even relatively small values of such a X~()'78~3 7.

bending on the horizontal plane irreparably jeopardize the quality of the cut, so that the maximal deformation allowed for the blade-holders in the direction of the force Fy is much smaLler than the maximal deformation allowed for the same blade-holders in the direction of the arrow Fy. Usually, a bending is a~lowed in the horizontal plane, the extent of which is 1/10th of the bending extent allowed in the vertical plane.
Therefore, in the shearing machines according to the prior art, each blade-holder has to be equipped with t~o strengthening structures tindicated by the reference letters "A" and "B" in Figure 1~, respectively equal for both blade-holders, each of which structures counteracts one of the two forces generated at the shearing time.
The mass of the "A" structure is ~arge, because it has to counteract a considerably large force Fy; and the mass of the "B" structure ;s also large, in that --although it has to counteract a force Fx which is smalLer than the force Fy -- it should reduce to values as small as possible any berd;ng deformations along the whole Length of the blade-holder, which is at least equal to the ~idth of the metal sheet to be shorn.
The structural typolog;es of the "A" and "B"
structures may vary according to the type of the shearing machine, and according to the manufacturer thereof; in any case~ they should however necessarily share the geometric character;stic of displaying their maximum moment of inertia in the direction of the relevant force According to the present state of the art, a good shearing machine is therefore necessarily equipped with large-mass blade-holders, in that the valu~s of their 84~

moments of ;nertia, and therefore of stiffness, should be h;gh along two direct;ons perpend;cular to each other.
Referr;ng in particular to Figures 3 and 4, a shear according to the present invention, generally indicated by the reference numeral 11, is of the type with rotary blades and comprises a guide column 12, an end of wh;ch is ;ntegrally fastened to a bracket element 13 destined to support a lower blade-holder 32, whose main ax;s is ;nd;cated by the reference numeral 20. On the column 12 a sleeve 14 slides, which makes a part of a bracket element with bhich an upper blade-holder 31 with main axis 21 ;s ;ntegral. The blade-holders 31 and 32 respectively support an upper blade 33 and a lower blade 34, w;th cutting edges 36, 37 engaging, dur;ng the shear;ng step, a metal sheet 35 uh;ch is being fed ;n the direction of the arrow "H". The bracket elements 13 and 14 are integral, through crank pins 16 and 16A running along circular trajectories 17 and 17A, with gear wheels 18 and 18A, ~h;ch gear ~heels are each driven by a motor means of its own ~not shown in the figures), so as to revolve accord;ng to the respective arrow "G".
Said motor means are governed by means of one single microprocessor circuit, and the gear wheels 18 and 18A
are inmeshed w;th each other, thus securing their necessary synchromism.
By simultaneously varying the revolution speed of said motor means by a same value, the revolut;on speed of sa;d blade-holders 31 and 32 is varied. The metal sheet travel;ng according to a constant-speed recti~inear movement in the direction of the arrow "H" will be consequently shorn into sheets of different lengths X3()7~

In the shear 11 according to the present invention, the shearing of the metal sheet 35 is obtained by means of a relative movement tarrows "M") of both of said blade-holders 31 and 32 relatively to each other according to the same mutuaLly parallel straight lines 10 and 10A, spaced apart by the necessary distance "d" and perpendicular to the plane on which the metal sheet 35 is laid.
But both of said blade-hoLders 31 and 32 result to be so orientated, that their respective main axes 21 and coincide with a half-line along ~hich a force FR i5 applied, which is the resultant from the vectorial composition of the forces F~ and FY which are generated at the shearing time.
In such a way, the blade-holders are subject to one s;ngle bend;ng stress, due to the resultant force FR, and the resist;ng sect;on of each blade-holder ;s g;ven such a structure that said blade-holders will show their h;ghest moment of ;nert;a against said s;ngle bending stress.
In more concrete terms, such a matter of fact results ;nto the blade-holders 31 and 32 being not equipped w;th the strengthen;ng structures -- inasmuch as such structures are now useless -- as ;ndicated by the reference letter "B" ;n Figure 1, typical for the blade-holders of the shears according to the prior àrt; and into said bLade-holders being slim and having their own ma;n ax;s 21 and 20 orientated at an angle cC of approximately from 10 to ôo relatively to the straight lines 1û and 10 A perpendicular to the plane on which the metal sheet 35 is laid, it being anyway confirmed that 78f~$
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for the purposes of the shearing, the relative posit;ons and movements relatively to the metal sheet 35 of the blades 33, 34 supported by sa;d blade-holders 31 and 32 are ;dentical to those of a traditiona~ shear~
In case of non-metal materials, the angle O< may reach values of values of up to 20. The relative positions and movements of the blades 33, 34 relatively to the sheet 35 remain unchanged in that they are suggested by the prior art in order to fulfil the necessary condit;ons for the shearing to be correctly executed.
At least one of the blade-holders 31, 32, and in particular the lower blade-holder 32, ;s associated with means wh;ch make it possible the distance "d" existing between the blades 33, 34 to be adjusted by varying the value of the angle ~ of incl;nation of the same blade-holder, relatively to the bracket element 13 which supports ;t.
Such adjustment means comprise an eccentric 38 hinged onto the bracket element 13, motor driven and revolving at the adjustment time, inside a hollow 19 provided on the blade-holder 32.
The possibility of varying the distance "d" is provided ;n order to make due allowance for the changes in cutt;ng parameters, such as, e.g., the nature of the mater;al, and/or the thickness thereof.
The teach;ngs according to the instant invention are also advantageously applicable to guillotine shears, as wéll as to rotary shears equipped with shear-holders of roll type, as generally indicated by the reference numeral 45.

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In case of shears of guillotine type, just incLining by the angle ~ the mobile blade-holder only, and consistently structurally lightening ;t, can be enough.
On the contrary, as regards the stat;onary blade-holder, on considering the absence of forces of inertia,varying the traditional position thereof relatively to the shearing forces, also reducing the mass thereof, is not essential for the purposes of the invention In case of rotary shears 45 ~reference is made to Figures 5 and 6), they use roll blade-holders, respectively indicated by the reference numerals 39 (the upper blade-holder) and 39A tthe lower blade-holder), revolving aroung the axes 40 and 40A, as shown in Figure 5, in which same reference numerals have been used in order to indicate eLements corresponding to those as already mentioned.
In particular, by comparing Figure 5, ~hich shows a rotary shear equipped with blade-holders of roll type mod;f;ed accord;ng to the teach;ngs of the present invention, to Figure 6, showing a rotary shear equipped with traditional blade-holders of roll type as known from the prior art, one can observe that the roll blade-holders of this latter shear are also stressed by a t~isting torque Mt having its pole on the axis of revolution 40, 40A of the rolls. This twisting tQrque deforms the cutting edges on the horizontal plane leading to an ;ncrease in sa;d d;stance "d"
In the shear shown in Figure 5, on the contrary, said tw;st;ng torque Ht ;s not generated,` in that the resultant force FR ~eriving from the vectorial composition of the forces Fx and Fy passes through the 4~
12.

revolution axes 40, 40A and its direction is the same as of the main axes (20, 21).

Claims (7)

1. Shear (11, 45) for shearing laminar elements (35) or the like, comprising at least one pair of blade-holders (31, 32 and 39, 39A) and relevant blades (33, 34) relatively mobile according to straight lines (10, 10A) substantially parallel to each other and spaced apart from each other by a distance (d) computed as a function of the thickness (s) and of the nature of the material to be shorn, with said blades (33, 34) being provided with cutting edges (36, 37) at which, at the shearing time, a pair of mutually perpendicular forces Fx and Fy are applied, with this latter force Fy acting along a straight line 10, 10A) perpendicular to the plane on which the material (35) to be shorn is laid, according to which straight line the movement takes place of the blade-holders (31, 32), which shear is characterized in that both of said blade-holders (31, 32 and 39, 39A) are given such a structure, and are so constrained, that they show the maximum value of their moment of inertia at bending according to one direction only, with said direction being coincident with the direction of the force FR which is the resultant deriving from the vectorial composition of the forces Fx and FY.

2. Shear according to claim 1, characterized in that the blade-holders (31, 32 and 39, 39A) constitute a part of a shear of rotary type (11, 45) for shearing a metal sheet (35), in which both the lower blade-holder (32, 39A) and the upper blade-holder (31, 39) have their main axis (20, 21) coincident with the direction of the resultant force FR.

3. Shear according to claim 2, characterized in that 14.

the angle (?) of inclination of the main axes (21, 20) of the blade-holders (31, 32 and 39, 39A) relatively to the mutually parallel straight lines (10, 10A) perpendicular to the plane on which the metal sheet (35) is laid, is substantially comprised within the range of from 10° to 80.

4. Shear according to claim 1, characterized in that the angle (?) of inclination of the main axes (21, 20) of the blade-holders (31, 32 and 39, 39A) relatively to the mutually parallel straight lines (10, 10A) perpendicular to the plane on which a non-metal material to be shorn is laid, may reach values of up to 200.

5. Shear according to claim 2, characterized in that at least one of said blade-holders (32) is associated with means (18, 19) for adjusting the distance "d"
existing between the two blades (33, 34).

6. Shear according to claim 5, characterized in that the adjustment of the distance "d" existing between the blades (33, 34) is obtained by changing the value of the angle (?) of inclination by means of an eccentric (18), which, at the adjustment time, rotates inside the interior of a hollow (19) provided on the lower blade-holder (32).

7. Shear according to one or more of the preceding claims, and equipped with blade-holders (39, 39A) of the roll type, revolving relatively to revolution axes (40, 40A), characterized in that both the lower blade-holder (39A) and the upper blade-holder (39) have their respective main axis (20, 21) coincident with the direction of the resultant force FR passing trhough the revolution axes (40 and 40A).