RU2482933C2 - Rack-and-pinion drive of tube pilger mill roll - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: proposed drive comprises round constant pitch angle pinion engaged with mill roll and fixed rack engaged therewith. Required ratio between mill stand reciprocation liner speed and roll angular speed is ensured by making rack teeth side surfaces in the zone of mutual contact with pinion teeth side surfaces as conjugated surfaces formed in rolling of round pinion variable-radius centroid line over that of the rack. Note here that at sections corresponding to such angular positions of pinion and roll rigidly engaged therewith whereat tube is reduced in variable-radius roll. Note also that pinion centroid radial coordinate equals roll variable rolling radius to rule out dam of strain in tube billet.

EFFECT: ruled out axial strain in tube cold reduction.

5 dwg, 1 tbl

Description

The invention relates to pipe rolling production, namely to cold longitudinal periodic rolling of pipes.

Known gear rack drive rotation of the roll mill of the longitudinal periodic rolling of pipes (Vinogradov A.G. Pipe production. M., Metallurgy, 1981, 340 S., S. 174, Fig. 92, S. 181, Fig. 95). This drive contains a round gear connected to the roll and having a constant angular pitch of the teeth, and being in mesh with it a fixed gear rack.

The roll of the mill for periodic rolling of pipes with a stream of variable radius cut on it is located in the bed of the working stand, which makes a reciprocating motion. In this case, the roll makes a rotational movement relative to the bed, carried out from the rack-and-pinion drive. The round gear is rigidly connected to the shank of the roll and engages with a fixed rack, also having a constant tooth pitch. In this case, the lateral surfaces of the teeth of the rails are planes having the same angle of inclination to the plane in which the roll axis moves. The angle between the normal to this plane and the planes representing the lateral surfaces of the rack teeth is the angle of engagement of the gear with the rack.

A disadvantage of the known gear-rack drive for rotating the roll is that it sets a constant ratio of the linear speed of the reciprocating movement of the stand to the angular speed of rotation of the roll, different from the variable rolling radius. The rolling radius is related to the variable radius of the stream. As a result, an axial force (tension or support) is formed in the rolled pipe. The presence of axial force negatively affects the surface quality of the rolled pipe and the reliability of the mill mechanisms, which are subject to significant additional loads.

The closest in technical essence and the achieved effect to the proposed device is a rack-and-pinion drive rolls of the mill for periodic rolling of pipes (USSR Author Certificate SU No. 1808431 A1, Bull. No. 14, 04/15/93).

This drive contains a round gear connected to the roller and having a constant angular pitch of the teeth, and being in mesh with the gear fixed gear rack. Moreover, the lateral surfaces of the teeth of the rack are planes, the angles of inclination of which to the plane in which the axis of the roll is moving are made different. Moreover, the angles of inclination of the planes corresponding to the lateral surfaces of the teeth of the rack are selected so that in some positions of the working stand considered, the ratio of the linear speed of the reciprocating movement of the stand to the angular speed of rotation of the roll, equal to the rolling radius, which depends on the variable radius of the stream.

The disadvantage of this gear rack mechanism is that it does not provide a continuous change in the ratio of the linear speed of the stand to the angular speed of the roll. This ratio changes abruptly when the contact of the gear teeth from one tooth of the rack to another passes. In this case, the necessary value of the ratio of the linear speed of the reciprocating movement of the stand to the angular velocity of the roll in all positions of the stand is not ensured and, accordingly, the absence of axial forces in the rolled pipe is not ensured. Considering the fact that the coefficient of frontal overlap in the gearing of the gear with the rack is more than unity, during the movement of the cage there are provisions in which at least two teeth should be in the gearing of the gear with the rack. In these stand positions, with the proposed principle of the formation of flat lateral surfaces of the teeth of the rack, either the transmission is jammed, or it closes with an impact upon contact transition to each subsequent pair of gear and rack teeth.

The technical result of the application of the proposed device is the exclusion of axial forces in the rolled pipe due to the fact that the necessary ratio of the linear speed of the reciprocating movement of the stand and the angular velocity of the roll at any position of the stand during rolling.

The technical result is achieved due to the fact that in the rack-and-pinion drive of the roll of the rolling mill of periodic pipes, containing a round gear connected to the roll and having a constant angular pitch of the teeth, and being locked with it, the fixed gear rack, the side surfaces of the teeth of the rack are made in the zone mutual contact with the lateral surfaces of the gear teeth as mating surfaces formed during the run-in, having a variable radius of the centroid of the round gear on the centroid of the rack. At the same time, in areas corresponding to such angular positions of the gear and the roll rigidly connected to it, at which the pipe is rolled in a stream of variable radius, the radial coordinate R _{C of the} gear centroid is equal to the variable rolling radius of the roll to eliminate back pressure or tension in the pipe billet.

Gear-rack gearing is known from the prior art, the tooth surfaces of the elements of which are profiled as mating surfaces (SU 51250 A, 01/31/1938). In the known technical solution, a rack-and-pinion gear is used, comprising a circular gear with a centroid in the form of a circle and a rack with a constant tooth pitch, the centroid of which is a straight line. This is the simplest option of rack and pinion gearing, the use of which in the roll drive of the periodic rolling mill does not allow to achieve the required technical result, since the use of a gear with a centroid of constant radius does not provide the necessary ratio of the linear speed of the reciprocating movement of the cage and the angular speed of the roll at any position of the stand during the rolling process, and accordingly, it is impossible to exclude the presence of axial forces in the rolled pipe.

Gearing is also known from the prior art (RU 2009386 C1, 03/15/1994), including rack-and-pinion gears, in which not only circles but also other curves can be used as centroid gearing elements. The technical result of this known technical solution is to increase the transmission efficiency by eliminating tooth slippage at the point of mutual contact and ensuring smooth engagement. The listed positive qualities improve the properties of the known gearing as an independent object, but cannot significantly affect the solution of the technical problem of ensuring the necessary ratio of the linear speed of the reciprocating movement of the stand and the angular speed of the roll of the rolling mill at any position of the stand during the rolling process.

In the proposed technical solution, the centroid of a round gear having a constant angular pitch of the teeth is not an arbitrary curve, but a curve defined in a certain way with the geometrical parameters of the roll stream, namely, the radial coordinate of the centroid in the sections corresponding to the angular positions of the gear and the roll rigidly connected to it at which the tube is rolled is equal to the rolling radius of the roll. The presence of this significant relationship between the parameters of the centroid of the gear and the roll, in combination with the execution of the lateral surfaces of the teeth of the gear and the racks mated, allows to provide the necessary technical result in the drive of the roll mill of the periodic rolling of pipes.

At the same time, the analysis of known sources of information did not reveal solutions associated with the use of a periodic gear rolling mill tube with a constant angular tooth pitch with a different centroid than a circle in the roll drive.

The invention is illustrated by drawings, where

- figure 1 presents a General view of the rack-and-pinion drive roll of the rolling mill;

- figure 2 shows a side projection of the drive (arrows indicate the reciprocating movement of the bed and the rotation of the roll);

- figure 3 shows a diagram of a circular gear with a centroid of variable radius;

- figure 4 is a diagram of the engagement of the gear with the rack having a continuously changing tooth pitch;

- figure 5 is a diagram of a two-roll rolling mill, each of the rolls of which has a drive made in accordance with the invention.

The proposed gear-rack drive roll mill periodic pipe rolling (Fig.1, 2) contains a circular gear 1 connected to the roll 2 and having a constant angular pitch of the teeth (Fig.3). Engaged with gear 1 is a fixed gear rack 3.

Round gear 1 (figure 3) has a constant angular pitch of the teeth, the main circle 4 of radius r ₀ , the pitch circle 5 of radius R _D , the circumference of 6 vertices of the teeth of radius R _B.

The lateral surfaces of the teeth of the rack are made in the area of mutual contact with the lateral surfaces of the gear teeth as mating surfaces formed during the running of the gear having a variable radius of the centroid 7 defined by the equation

centroid 8 slats (figure 4), defined in a parametric form

where R _C is the polar radius;

α is the polar angle, varying in the range 0≤α≤α _MAX ;

α = 0 corresponds to the gear position in engagement with the first tooth of the rack;

α = α _MAX corresponds to the position of the gear mesh with the last tooth of the rack.

A centroid is a geometric locus of instantaneous centers of rotation of a body in absolute or relative motion (see, for example, Artobolevsky II, Theory of Mechanisms. Moscow, Nauka, 1965, 776 p., P. 114). For rack and pinion gearing, the combination of the centroid of the gear and the rack completely determines the law of motion of the gear relative to the stationary rack, as well as the shape of the side surfaces of the teeth of the rack and, accordingly, is a structural characteristic of the mechanism.

For gear 1, worn motionlessly and concentrically on the shank of a rolling roll 2 having a stream of variable radius, for example, in the polar coordinate system, equation (1) of centroid 7 is drawn up. In areas corresponding to such angular positions of the gear and the roll rigidly connected to it, at which the pipe is rolled in a stream of variable radius, the radial coordinate R _{C of the} gear centroid 7 is equal to the variable rolling radius of the roll.

In mesh with the gear 1 is the gear rack 3 with a continuously changing tooth pitch (figure 4). For gear rack 3, on the basis of equation (1), the centroids 7 of the gear are determined in the parametric form (parameter α) equation (2) of the centroid 8 of the gear rack.

The lateral surfaces of the teeth of the rack 3 are made in such a way that they are mated to the side surfaces of the teeth of the gear 1. Such lateral surfaces are obtained by running without sliding the centroid 7 of the gear on the centroid 8 of the rack.

Example. A rack-and-pinion drive rotates a roll of a cold periodic rolling mill. The roll has a calibration of a stream of variable radius for rolling the pipe along the route 40 × 2.7 → 22 × 0.75. In the mills of the periodic rolling of pipes, as the name implies, rolling of the pipe occurs periodically. Accordingly, there are angular positions of the gear and the roll rigidly connected to it, at which the pipe is rolled in a stream of variable radius, and angular positions at which rolling does not occur, but other operations are carried out.

In this particular case, the rail is installed in such a way that the angle of rotation of the gear from the angular position of the gear in engagement with the first tooth of the rack to the angular position at which rolling of the pipe begins in a stream of variable radius is 0.43 rad. The angular positions of the gear and the roll rigidly connected to it, at which the pipe is rolled, corresponds to a range of 0.43 rad≤α≤4.51 rad. The sections in this range correspond to the various stages of the pipe rolling process. At angular positions of 4.51 rad <α≤6.30 rad rolling does not occur. The angular position of the gear in engagement with the last tooth of the rack corresponds to α = 6.30 rad.

In the range of angular positions of 0.43 rad≤α≤4.51rad, the rolling radius of the roll varies linearly from 140.0 mm to 144.8 mm. At other angular positions of the gear and the roll, rolling does not occur, respectively, the rolling radius of the roll is not determined. In accordance with the claimed technical solution in areas corresponding to the angular positions of 0.43 rad≤α≤4.51 rad gear and a roll rigidly connected to it, at which the pipe is rolled in a stream of variable radius, the radial coordinate R _{C of the} gear centroid is equal to the rolling variable roll radius. With other angular positions, the shape of the centroid within the framework of this technical solution is not regulated, since it does not affect the technical result, therefore, the shape of the centroid can be selected from any other considerations. At the same time, specifying the shape of the centroid in these areas is necessary to perform the lateral surfaces of the teeth of the rack mated with the side surfaces of the gear teeth along the entire length of the rack. Note that, since we are talking about gearing, the term “mating surfaces” is used in the sense in which it is used in the theory of gears (see, for example, Levitskaya ON, Levitsky NI Course on the theory of mechanisms and machines, M., High School, 1985, p. 179).

In this example, to set the centroid of the gear in the sections corresponding to such angular positions of the gear and the roll, at which the pipe does not roll, circular arcs are adopted: a radius of 140.0 mm in a section of 0.0 rad≤α <0.43 rad and a radius of 144, 8 mm in the area of 4.51 rad <α≤6.30 rad.

In accordance with equation (1) and the first of equations (2), the coordinates y _{P of the} rail centroid are uniquely determined, which vary from -140.0 mm to -144.8 mm.

A certain integral with a variable upper limit on a given function R _C , present in the second of equations (2), is known to be a function of the upper limit (see, for example, G. Fikhtengolts, Differential and integral calculus course, T.II, M ., Science, 1969, S.115). For a given function R _C = R _C (α) (or, equivalently, R _C = R _C (φ)), this integral can be calculated by known methods, as a result of which an unambiguous dependence of the coordinate x _P of the centroid points of the rail on α . In our case, you can use the well-known methods of calculating a certain integral of a function defined by a tabular method (see, for example, Bermant A.F., Aramanovich I.G. Short course in mathematical analysis, M., Nauka, 1966, S.323) .

As a result of the integration of the function R _C , the coordinate x _P coordinates of the rack centroid are unambiguously obtained, which vary from 0.0 to 897.2 mm.

Below, by way of illustration, we show the specific numerical values of the rolling radius of the roll, the radial coordinate R _{C of the} gear centroid and coordinates y _P , x _{P of the} rack centroid corresponding to the specific angular positions of the gear and the roll, defined by the angle α:

α glad 0.00 0.21 0.43 0.94 1.45 1.96 2.47 2.98 Rolling radius, mm - - 140.0 140.6 141.2 141.8 142.4 143.0 R _C , mm 140.0 140.0 140.0 140.6 141.2 141.8 142.4 143.0 y _P mm -140.0 -140.0 -140.0 -140.6 -141.2 -141.8 -142.4 -143.0 x _P mm 0,0 29.4 60,2 131.4 203.6 275.7 348.0 421.3 α glad 3.49 4.00 4,51 5.02 5.53 6.04 6.30 Rolling radius, mm 143.6 144.2 144.8 - - - - R _C , mm 143.6 144.2 144.8 144.8 144.8 144.8 144.8 y _P mm -143.6 -144.2 -144.8 -144.8 -144.8 -144.8 -144.8 x _P mm 493.7 560.9 638.9 712.5 786.1 859.7 897.2

In areas in which the centroid 7 of the gear is a circle of constant radius, the centroid 8 of the rack is parallel to the plane 9 of the movement of the axis of the roll (figure 4). In these sections of the rack, the side surfaces of the teeth are planes having a certain angle of inclination to plane 9. The angle between the normal to plane 9 and the planes representing the side surfaces of the rack teeth is the angle of engagement. The larger the radius of the circle representing the portion of the centroid of the gear 7, the greater the angle of engagement of the gear with the rack and the greater the pitch of the teeth of the rack.

In areas where the centroid 7 is not a circle, the lateral surfaces of the rack teeth are the surfaces of curved cylinders (Fig. 4), the generatrix of which is parallel to plane 9. Due to this shape of the side surfaces of the rack teeth, the necessary ratio of the linear speed of the reciprocating movement of the stand to the angular velocity of the roll at any position of the stand during the rolling process. In addition, there is no jamming of the rack and pinion transmission and no blows during the transition of contact to each subsequent pair of gear teeth and gear rack.

The lateral surfaces of the rack teeth can be constructed (or machined on the machine) based on the specified centroid gears and rack in accordance with the known principles of the theory of gears. The methods of constructing conjugate surfaces, for example, by the method of bending (see, for example, Levitskaya ON, Levitsky NI Course in the theory of mechanisms and machines, M., Higher School, 1985, S.186-187), allow to implement as theoretical building a tooth profile, and practical obtaining a tooth profile on a gear cutting machine. For example, this can be done by choosing the surface of the gear teeth as the producing surface and providing the relative motion of the producing surface and the workpiece of the rack as it is when rolling the centroid of the gear on the centroid of the rack.

The operation of the device will be considered on the example of a two-roll rolling mill, the drive of each of the rolls of which is made in accordance with the invention. This option is preferred.

Figure 5 presents a diagram of the mill stand for cold periodic rolling of pipes. Stationary during the rolling process, the pipe billet 10 is located in rolls 2, on which streams of variable radius are made. The rolls are mounted in the frame 11, making a reciprocating motion. A round gear 1 is put on the shank 12 of each of the rolls, which is meshed with a gear rack 3 having a continuously changing pitch.

Gear rack drive roll mill periodic rolling of pipes works as follows.

The bed 11 with rolls 2 having streams of variable radius, makes a reciprocating motion (in the direction perpendicular to the plane of the drawing). The rollers 2 additionally receive rotation from the round gears 1, worn on the shanks of the 12 rolls, and engaged with the fixed gear racks 3 having a continuously changing tooth pitch. As a result of the movement of the bed 11 in combination with the rotation of the rolls 2 with a stream of variable radius, the rolled billet of the pipe 10 is plastically deformed. This deformation of the billet occurs in a limited area of the complete movement of the bed.

According to the invention, the lateral surfaces of the teeth of the rack 3 are made as mating surfaces formed when the centroid of the gear is run on the centroid of the rack in accordance with dependencies (1) and (2). Due to this, in those positions of the bed in which plastic deformation is carried out by the rolls 1 of the stationary billet of pipe 10, the ratio of the linear speed of the bed 11 to the angular velocity of the rolls 2 (in particular, equal to the rolling radius of the stream in the deformation zone) is ensured, which eliminates the appearance in the workpiece 10 axial force (support or tension).

The consequence of the exclusion of axial forces is an improvement in the surface quality of the rolled pipe and an increase in the durability of the mechanisms of the tube mill by reducing the loads acting on them.

Claims (1)

A rack-and-pinion drive of a roll of a rolling mill of a pipe, comprising a circular gear connected to the roll and having a constant angular pitch of teeth, and being engaged with it, a fixed gear rack, characterized in that the side surfaces of the teeth of the rack are made in the area of mutual contact with the side surfaces gear teeth as mating surfaces formed during running-in of a round gear having a variable radius of a centroid on a centroid of a rack, and in areas corresponding to such angular positions the stubble and the roll rigidly connected to it, at which the pipe is rolled in a stream of variable radius, the radial coordinate of the centroid of the gear is equal to the variable rolling radius of the roll to exclude backwater or tension in the pipe billet.

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