SU1808522A1 - Cutting tool holder - Google Patents

Description

The invention relates to the machining of metals and can be used mainly on milling and boring machines.

The purpose of the invention is to increase the reliability of fixing the cutting tool.

This goal is achieved by the fact that in the known device the window surface of the ramrod and the supporting surface of the second wedge element interacting with it are made inclined at an angle of 2-15 ° to the supporting surface of the first wedge element.

In FIG. 1 shows a device in section; figure 2 is a design diagram of the mechanism of the device; in Fig.3 and 4 - section aa in Fig.1; figure 5 is a graph of the dependence of the increase in the force of fixing the tool from the fall of the friction coefficient; 6 is a graph of the dependence of the change in the fixing force on the ratio of the angles between the supporting surfaces of the wedge elements.

The device comprises a housing 1, in the upper part of which a threaded hole 2 is made for interaction with a mating spindle of the machine. In the lower part of the housing 1 there is a blind central hole 3, in which a ramrod 4 is mounted with axial movement, having a window 5, in which the first wedge element 7 is located on the lining 6, which interacts with its inclined surface with the second wedge element 8, which contacts the surface, opposite to its wedge surface, with the surface of the window 5 of the ramrod 4, and its lateral surface in the radial direction with the inner surface of the elastic ring 9. The screw 10 is a threaded hole elastic th ring 9 and designed to move the wedge member 7 in a radial direction with simultaneous deformation of the elastic ring 9. Cleaning rod 4 at one end cooperates with a return spring 11 disposed in a blind axial bore 3 of the housing 1, and the other interacts with the threaded ring cutter tool 12.

The device operates as follows.

The cutter 12 is screwed onto the threaded end of the ramrod 4 until the interaction of its base end with the end face of the mandrel body 1. By rotating the screw 10, the wedge element 7 along the lining 6 moves in the radial direction, at the same time the wedge element 8 and the ramrod 4 and the cutter 12 interacting with it, compressing the return spring 11, move upwards and make a power short circuit of the joint between the ends of the cutter 12 and the housing 1 .

Moreover, under the action of forces from the side of the screw 10 and the lateral surface of the wedge element 8, the elastic ring 9 is deformed in the radial direction by the amount <52 of the deformation of the elastic ring (see Fig. 4). After the beginning of high-speed, power cutting, accompanied by intense dynamic effects of cutting forces on the device mechanism, the effective friction coefficients drop on the contact surfaces of the mechanism elements. Moreover, due to the potential energy accumulated by the elastic ring 9 at the fixing stage, the wedge elements 7 and 8 tend to move in the radial direction and move the ramrod 4 in the axial direction, while increasing the tool fixing force on the device, and this effect is manifested to the greatest extent provided that the window surface of the ramrod 5 and the supporting surface of the second wedge element 8 interacting with it are made inclined at an angle of 2-15 ° to the supporting surface of the first wedge element 7. (Value «, f D.2)

In order to determine the effectiveness of introducing an additional angle, we consider the statistical problem of the interaction of the elements of the mechanism of the device for fixing the tool (figure 2).

We accept the following notation Rij (i = 0,1 ... 6; j = 1,2) - the reaction of the i-th bond. C is the stiffness of the elastic ring 9,

Ci - total rigidity of machine tools and mechanism parts,

Νη is the normal component of the reaction of the i-th bond.

T is the tangent component of the reaction of the i-th bond • In this case

Tij = nijtg de;

where <p \ 0 = 1,2) is the angle of friction at the joints of the parts of the mechanism, i.e. tg where Kj is the coefficient of friction.

0 _m j (m = 1,2,3; = 1,2) - displacements • of the elements of the mechanism during its loading and functioning.

and _Roj. 5 _N ij ι Rfy

02) - ^; dz] - ^.

Given the design features of the mechanism and the conditions for its functioning, we accept the following assumptions:

Ci> C,

those. due to the low stiffness of the elastic ring, we consider the remaining elements of the mechanism to be significantly more rigid:

p | / J = 1 = φι = 11 °, where ¢ 4 is the angle of rest friction (statistical angle of friction), then, taking into account (2), we have:

Kj / j = 1 = K1 = 0.2, where K1 is the coefficient of static friction (statistical coefficient of friction) <pl /) = 2 = p2 = 0 °, where (p2 is the dynamic angle of friction that occurs under prolonged exposure to intense dynamic loads on the mechanism in the process of power and high-speed vibration cutting, then taking into account (2) we have:

Kj / J = 2 = K2 = 0, where K2 is the dynamic coefficient of friction.

Therefore, taking into account 1, we have: T y /) = 2 = 0.

those. we believe that with a long-term action on the mechanism of the device to fix the tool of the dynamic components of the cutting forces, the tangential components of the reactions of the connection of the parts of the mechanism are removed and the normal components are redistributed, accompanied by relative movement of the parts of the mechanism and changes in dmj (<5mi ^ <5 _m2 ) the nature of which, along with with a change in the value of R6J in the transition from j = 1 to) = 2, it allows to evaluate the reliability of fixing the tool.

Due to the fact that the contact areas of the parts are significant, i.e. the contact stresses at the joints are much less than the permissible crushing stresses of the product material, and the parts themselves have sufficient rigidity, we assume that the bond reactions are applied at one point, the coordinate of which is not taken into account in the future, since it is enough to consider the relationship of forces to solve the problem, but not their moments.

To solve this problem, we write the control system statics for the component forces acting on parts 7, 8, 4 and 1 of the mechanism pos.7.

pos.7 ί X.Ni-N ₂ cos a + T ₂ sin «= 0

Iy.Ro-TiT ₂ cos a -N2siri (r = 0, or with _g (1)

Ni-N ₂ (cos--sin a tg φ) = 0 (R ₀ -Nitg <p-N2 (cosa tg99 + sina) = 0 (12)

G

X.N2COS a -T2sln a -N ₃ cos αι -T2sln αι-Τ ₅ Ό item З

y.N2Slna + T2C0Sa + N ₃ sln <nT ₃ cos «1-Ν5-0 or, taking into account (1)

N2 (cosa-sin “tg ^>) - N ₃ (cosai + slnatgy)) '-Nstgy“ 0

N2 (sln a + COS a tg φ) + N3 (sln ai + cos fli tg φ)

-N5 = 0

? .N ₃ cos ai-T ₃ sln ai-T4-R6-0 • T ₃ cos Ci-N ₃ sln αι-Ν ^ -Ο or, taking into account (1)

N3 (cos sin-tritgp) = N / itg φ -R6-0 N3 (cos aitg φ -sin i i) -N4 = 0 (14).

fx.R6-Ni + T4 + T5-0 pos. 1 [_y.N5 + N4 + Ti-Ro-0, or c (1)

R6-Ni + N4tgy7 + N5tgy9 = 0 N6 + N4 + Nitg φ -Ro-0 (15)

An analysis of the system of equations (12) - (15) shows that the nature of the deformation of the elastic link (ring 9) substantially depends on the angle (Hz

So, when «1 = 0 N5 Ro. therefore, the value 02- * 0 of Fig. 3, with "1 ^ 10 °, the value of 02 and di become close in value, Fig. 4. Thus, the total potential energy of the elastic deformed link increases with the angle угла 1. At the same time, when the angle «> 15 °, a significant opposition to the movement of the wedge 8 in the process of effective friction coefficients during vibration cutting begins to be exerted by the projection of the force N3 on the ΟΥ axis. At the same time, part of the accumulated potential energy spent on increasing the clamping force of the tool R6 begins to fall, which limits the rationality of a further increase in the angle “1.

More correctly, the effect of changing the angle "1 on the force of fixing the tool shows the graph in figure 5 and 6.

Figure 6 shows the characteristics of the increase in the clamping force of the tool R6 from the fall of the friction coefficient in the process of vibration of one cutting. Here K is the coefficient of friction, R6 is the tool fixing force, expressed in units of the force of interaction of the screw 10 with the device mechanism. It can be seen that when "1 = 0, the initial force of fixing the screw 10 on the wedge 7. After the friction coefficients drop to zero, the force of fixing the tool increases 1.6-2 times, curves 1 and 2, with the values of the angle" 1 close to the optimal value, there is an increase as the initial value of the force R _o . and in particular, its values when the friction coefficients drop during vibration cutting, the ZiL curves. Thus, the introduction of the angle αι makes it possible to increase the gain of the device mechanism from 1.6-2 to 3.5-5.

The graphs of FIG. 6 show a rational range of angle values. So at αι <2 ° its influence is not very noticeable. At "1> 15 °, its introduction gives a negative effect. Thus, the range of angle a is 9-12 °. The use of the proposed device leads to increased durability and lower tool consumption.

Claims (2)

Claim A device for attaching a cutting tool, comprising a housing with a ramrod located in it with a window, in which inclined surfaces interact with each other, and supporting surfaces opposite them, with the surfaces of the window in the ramrod, one of the wedge elements being mounted for radial movement from the screw located in the threaded hole of the elastic ring, mounted to interact with the inner surface with the side surface of the second wedge element, distinguishing it in that, in order to increase the reliability of fastening, the surface of the ramrod window and the supporting surface of the second wedge element interacting with it are made inclined at an angle of 2-15 ° to the supporting surface of the first wedge element. FIG. 2. Aa Tigl FIG. b / - <Ζ = 3β · - g-a = 25 ·, $ -4 = 20 ° 6