US3910088A

US3910088A - Machine for straightening of round bars or tubes

Info

Publication number: US3910088A
Application number: US515712A
Authority: US
Inventors: Horst Lorenz; Gunter Gerhardt
Original assignee: TH Kieserling and Albrecht GmbH and Co
Current assignee: TH Kieserling and Albrecht GmbH and Co
Priority date: 1973-10-18
Filing date: 1974-10-17
Publication date: 1975-10-07
Anticipated expiration: 1992-10-07
Also published as: JPS5067770A; HU170713B; ES430996A1; DD113702A1; SU561496A3; JPS542196B2; DE2352281A1; FR2248093B1; GB1461859A; CA1024052A; FR2248093A1; IT1022882B; DE2352281B2

Abstract

A straightening machine for long tubular or bar-shaped round workpieces has a row of straightening units into which a fresh workpiece is introduced and from which a straightened workpiece is removed by moving sideways. Each unit has two lower straightening rolls and an upper straightening roll movable between an extended position in which it cooperates with the other rolls of the same unit to straighten a workpiece and a retracted position in which a fresh workpiece can be inserted or a treated workpiece removed. All upper rolls are movable in a synchronism with each other in response to rotation of a crankshaft which is mounted in the frame of the machine and transmits motion to the upper rolls through the medium of double cranks and connecting rods. The crankshaft is rotatable by a drive which has a gear secured to an intermediate portion of the crankshaft and a fluid-operated motor or a set of pulleys for rotating the gear through the medium of one or more additional gears. The crankshaft further serves to raise and lower the upper sections of tubular guides in which the workpiece is confined between neighboring straightening units during treatment by the rolls. The upper sections are lifted simultaneously with the upper rolls to allow for unimpeded insertion of fresh workpieces and removal of straightened workpieces. A further shaft can adjust the positions of upper rolls independently of the crankshaft so that the units can receive workpieces having larger or smaller diameters.

Description

United States Patent Lorenz et al.

Oct. 7, 1975 MACHINE FOR STRAIGHTENING 0F ROUND BARS OR TUBES [75] Inventors: Horst Lorenz, Solingen; Gunter Gerhardt, Wuppertal-Vohwinkel, both of Germany [73] Assignee: TH. Kieserling & Albrecht,

Solingen, Germany [22] Filed: Oct. 17, 1974 [21] Appl. No.: 515,712

[30] Foreign Application Priority Data Oct. 18, 1973 Germany 2352281 [52] US. Cl 72/98; 72/99 [51] Int. Cl? B21D 3/04 [58] Field of Search 72/95, 98, 99, 100

[56] References Cited UNITED STATES PATENTS 1,382,309 6/1921 Moltrup 72/98 3,759,077 9/1973 Hartkopf 72/99 FOREIGN PATENTS OR APPLICATIONS 725,630 9/1942 Germany 72/99 Primary Examiner-Lowell A. Larson Attorney, Agent, or FirmMichael S. Striker [57] ABSTRACT A straightening machine for long tubular or barshaped round workpieces has a row of straightening units into which a fresh workpiece is introduced and from which a straightened workpiece is removed by moving sideways. Each unit has two lower straightening rolls and an upper straightening roll movable between an extended position in which it cooperates with the other rolls of the same unit to straighten a workpiece and a retracted position in which a fresh workpiece can be inserted or a treated workpiece removed. All upper rolls are movable in a synchronism with each other in response to rotation of a crankshaft which is mounted in the frame of the machine and transmits motion to the upper rolls through the medium of double cranks and connecting rods. The crankshaft is rotatable by a drive which has a gear secured to an intermediate portion of the crankshaft and a fluid-operated motor or a set of pulleys for rotating the gear through the medium of one or more additional gears. The crankshaft further serves to raise and lower the upper sections of tubular guides in which the workpiece is confined between neighboring straightening units during treatment by the rolls. The upper sections are lifted simultaneously with the upper rolls'to allow for unimpeded insertion of fresh workpieces and removal of straightened workpieces. A further shaft can adjust the positions of upper rolls independently of the crankshaft so that the units can receive workpieces having larger or smaller diameters.

16 Claims, 9 Drawing Figures U.S. Patfint Oct. 7,1975 Sheet 1 of 5 3,910,088

U.S. Patent Oct. 7,1975 Sheet 2 of5 3,910,088

FIG.2

US. Patent Oct. 7,1975 Sheet 3 of5 3,910,088

FIGA

I "I'I'I'A MACHINE FOR STRAIGIITENING OF ROUND BARS OR TUBES BACKGROUND OF THE INVENTION The present invention relates to improvements in machines for straightening elongated workpieces having a circular outline. More particularly, the invention relates to improvements in machines which are especially suited for the straightening of very long round tubes or bars. Still more particularly, the invention relates to improvements in means for moving selected straightening rolls of a straightening machine into and from engagement with elongated workpieces for the purpose of cooperating with other rolls to straighten a freshly introduced workpiece as well for the purpose of enabling the machine to treat workpieces having different outer diameters.

ln many straightening machines, the workpieces which are to be treated are fed into and removed from the machine by moving axially. This is desirable and practical in connection with the treatment of relatively short workpieces; however, the overall length of the machine increases considerably if the workpieces to be treated are very long. Thus, it is necessary to provide an elongated trough at the inlet end of the machine so that the trough can receive a fresh workpiece in order to guide it during lengthwise movement through one or more straightening units. It is further necessary to provide a second trough at the discharge end of the machine in order to guide a treated workpiece during axial movement beyond the straightening unit or units. Another drawback of axial feeding and removal of very long workpieces is that the leading end of an untreated workpiece is likely to be scored or otherwise damaged in response to initial engagement with the rotating straightening rolls which must rapidly accelerate the workpiece to the full operating (angular) speed. This invariably results in some slippage of straightening rolls with respect to the workpiece or vice versa, especially since the inertia of a long workpiece is substantial so that the workpiece offers a pronounced resistance to rapid acceleration to a normal speed at which the workpiece rotates about its own axis and simmultaneously advances axially through the straightening machine The inertia of a relatively long and hence heavy and bulky workpiece opposes rapid axial acceleration of the workpiece which also contributes to the likelihood of damage to the surface of the workpiece during initial engagement of its leader with the foremost straightening rolls.

Gradual axial and/or angular acceleration of a fresh workpiece is undesirable because the treatment takes up much more time and the machine must be provided with complex drives which control the speed of straightening rolls during the initial stage of introduction of a fresh workpiece. On the other hand, and explained above, rapid axial and angular acceleration of a relatively long workpiece is likely to result in slippage of straightening rolls along the adjacent surface of the workpiece except if the rolls engage the leader of the workpiece with a substantial force which again results in scoring or other deformation of the freshly introduced workpiece so that the latter necessitates a secondary treatment subsequent to completion of the straightening operation.

It was already proposed to feed relatively long workpieces sideways, i.e., to move a fresh workpiece to a position along one side of the straightening machine and to thereupon move the workpiece laterally into the spaces between several groups of straightening rolls. Such machines exhibit the advantage that each group of straightening rolls must treat only a short section of the workpiece, i.e., the axial movement of a workpiece during treatment need not exceed that length which equals the distance between the neighboring groups of straightening rolls. Still further, such machines exhibit the advantage that a freshly introduced workpiece is simultaneously engaged and set in rotary motion (as well as imparted an axial movement) by several groups of rolls so that the likelihood of scoring the external surface in response to rapid acceleration is less pronounced. A machine into which the workpieces are being fed by moving sideways can complete the treatment of a relatively long workpiece within a much shorter interval of time than a machine into and through which the workpieces are fed by moving axially. Furthermore such machine is less likely to be damaged due to excessive swaying of the trailing end of a curved workpiece during combined angular and axial movement through the machine. This will be readily understood since the curvature of a fresh workpiece is reduced considerably as soon as it is properly engaged by the straightening rolls of two or more groups of rolls.

A drawback of presently known straightening machines of the just outlined character is that the introduction of fresh workpieces and the removal of straightenend workpieces take up too much time so that the output of such machines is unsatisfactory in spite of the fact that the necessary axial movement of a workpiece during straightening is only a small fraction of the overall length of the workpiece. In order to introduce a workpiece sideways, at least one roll of each group of straightening rolls must be moved away from the other rolls of the respective group so as to provide room for introduction of the fresh workpiece. The same operation must be repeated prior to removal of a straightened workpiece and the movable roll or rolls of each group must remain in their retracted positions during subsequent introduction of the next-following untreated workpiece. Additional problems arise in connection with adjustment of the machine so that it can treat workpieces having different diameters. Such adjustment also necessitates the movement of at least one roll of each group of straightening rolls so that the rolls define a passage which is larger or smaller than the previously defined passage, depending on the diameters of the next bath of workpieces. Further adjustments in the positions of rolls of each group of straightening rolls are necessary when a series of workpieces consisting of a relatively soft material is followed by a series of workpieces consisting of much harder material, or vice versa. The force with which the rolls engage a relatively soft workpiece should be much less pronounced than the force with which the rolls engage a workpiece whose material is relatively hard and thus less likely to be deformed.

As a rule, adjustments for the purpose of treating workpieces having different diameters or consisting of different materials are much less frequent that the movements of selected rolls between extended and retracted positions preparatory to introduction of fresh workpieces and preparatory to removal of straightened workpieces. The presently known mechanisms for effecting movements of one or more rolls of each group of straightening rolls are not entirely satisfactory because they do not insure that each and every movable roll is displaced to the same extent and also because such known mechanisms are bulky, complex, prone to malfunction and quite expensive. Furthermore, such known mechanisms are rather slow, especially if the machine comprises a substantial number of straightening rolls, so that the ratio of combined intervals of idleness to combined intervals of actual use of the machine is unsatisfactory. The need for accurate synchronization of movements of all movvable rolls is particularly pronounced immediately prior to removal of a freshly treated workpiece, namely, during that stage of retraction of moveable rolls which corresponds to the transition between plastic and elastic deformation of the straightened workpiece.

SUMMARY OF THE INVENTION An object of the invention is to provide a novel and improved machine for the straightening of rod-shaped or tubular workpieces having a circular outline, particularly for straightening of relatively long and bulky workpieces which are fed into and removed from the machine by moving sideways.

Another object of the invention is to provide the machine with novel and improved means for synchronizing the movements of those straightening rolls which must be retracted prior to introduction of a fresh metallic workpiece as well as prior to removal of a straightened metallic workpiece.

A further object of the invention is to provide novel and improved means for actuating sections of guide means in which the workpieces rotate during axial movement as a result of rotation by the straightening rolls.

The invention is embodied in a straightening machine for elongated tubular or bar-shaped workpieces, especially for very long workpieces having a circular outline. The machine comprises an elongated frame, a row of straightening units which are mounted in the frame and each of which comprises a group of straightening rolls at least one of which is movable between an extended position of engagement with a freshly introduced workpiece and a retracted position in which a workpiece is insertable into or removable from the units, and novel means for moving the movable rolls in exact synchronism with each other. The means for moving the moveable rolls comprises a single shaft in (preferably a crank-shaft) which is rotatably mounted in and extends lengthwise of the frame, and means for displacing the movable rolls through identical distances in response to rotation of the shaft.

The machine further comprises drive means for rotating the shaft, and such drive means has an output element (e.g., a gear) which is preferably connected to an intermediate portion of the shaft, most preferably substantially midway between the ends of the shaft. The drive means may comprise a fluid-operated motor and a power train which connects the motor with the shaft, and such power train includes the aforementioned output element. The power train may constitute a transmission. Alternatively, the drive means for the shaft may comprise one or more pulleys which are mounted on a second shaft and are connected thereto by discrete couplings, and a power train which connects the second shaft with the first mentioned shaft and includes the aforementioned output element. The

just described drive means may further comprise one or more brakes for arresting the second shaft in selected angular positions.

The novel features which are considered as characteristic of the invention are set forth in particular in the appendded claims. The improved straightening machine itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an elevational view of a straightening machine which embodies one form of the invention;

FIG. 2 is an enlarged partly vertical sectional view of the first straightening unit in the machine of FIG. 1;

FIG. 3 is an enlarged sectional view as seen in the direction of arrows from the line III-III of FIG. 1;

FIG. 4 is an enlarged sectional view as seen in the direction of arrows from the line IV-IV of FIG. 1;

FIG. 5 is a diagram showing various positions of the crank pin of one of the cranks on the crankshaft which effects movements of selected straightening rolls prior to introduction of fresh workpieces and prior to removal of straightened workpieces;

FIG. 6 is an enlarged fragmentary sectional view as seen in the direction of arrows from the line VI-VI of FIG. 1;

FIG. 7 is a sectional view as seen in the direction of arrows from the line VII-VII of FIG. 6;

FIG. 8 is a fragmentary sectional view, similar to that of FIG. 6, ofa straightening unit in a modified machine; and

FIG. 9 is a horizontal sectional view as seen in the direction of arrows from the line IX-IX of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a straightening machine 1 for elongated tubular or solid bar-shaped or rod-shaped metallic workpieces 60 (FIG. 3) having a circular outline. The machine 1 comprises an elongated frame la which is somewhat longer than the length of a workpiece 60 and supports four discrete straightening units 2, 3, 4, 5 which are equally spaced from each other, as considered in the longitudinal direction of the frame. The length of a workpiece 60 which is to be treated in the machine 1 is equal to or approximates the distance between the left-hand frame member 6 and the last straightening unit 5. This renders it possible to move the rotating workpiece lengthwise during treatment whereby the finished workpiece 62 (FIG. 3) leaves the machine 1 at a time when its front end portion is closely adjacent to the right-hand frame member 6a of the frame. The rolls of each of the four straightening units 2-5 treat a certain length of the workpiece 60 which is fed into the machine 1 by moving sideways from one side of the row of units 2-5 and which is removed from the machine by moving sideways away from the straightening rolls at the other side of the row of units 2-5.

The construction of parts in each of the four straightening units 2-5 is preferably identical. Each of these units comprises two lower straightening rolls 7, 9 and an upper straightening roll 8, 10, ll, 12 respectively.

The rolls 7-9 of the first straightening unit 2 treat that portion of a freshly introduced workpiece 60 which ini' tially extends between the frame member 6 and the unit 2; the

rolls

7, 8, of the unit 3 treat that length of a workpiece which initially extends between the units 2 and 3; and so forth. Thus, the

rolls

7, 8, 12 of the last straightening unit 5 treat that length of a workpiece which initially extends between the units 4 and 5 and which is located between the unit 5 and frame member 6a before the straightening workpiece 62 is removed from the machine 1.

In accordance with a feature of the invention, the upper straightening rolls 8, I0, ll, 12 are movable away from the

lower rolls

7, 9 in the respective unit 2, 3, 4 or 5 in a novel way for the purpose of permitting introductin of fresh workpieces 60 and of removing finished (straightened) workpieces 62, as well as for the purpose of changing the dimensions of the passages between the rolls of the respective units so as to allow for the straightening of workpieces having different diameters. In the embodiment of FIG. '1, the upper rolls 8, 10, l l and 12 are movable up prior to introduction of a fresh workpiece 60 or prior to removal of a straightened workpiece 62, and down prior to straightening of a freshly introduced workpiece 60. The mechanism for effecting up-and-down movements of the

rolls

8, 10, 11 and 12 for the purpose of changing the dimensions of the aforementioned passages comprises a single horizontal adjusting shaft 13 and means (including the

parts

26, 27, 28 and 29 best shown in FIG. 6) for transmitting motion from the shaft 13 to the upper rolls 8, l0, 1 l and 12 in response to angular displacement of the shaft 13.

The mechanism for moving the

upper rolls

8, 10, 11 and 12 up and down for the purpose of introducing fresh workpieces 60 and of removing straightened workpieces 62 comprises a single horizontal crankshaft 14 which is operatively connected with the upper rolls of the four straightening units 25. The crankshaft 14 has four double cranks 14a, one for each of the upper straightening rolls 8, 10, 11 and 12, elongated rodshaped sections 14d which extend between the neighboring units 2, 3, 4, 5, and couplings 14c each of which separably but rigidly connects one end portion of a sec tion 14a to one of two stubs 14b of the adjacent double crank 14a. When the sections 14d are being assembled with the double cranks 14a, one must insure that the upper straightening rolls 8, 10, l1 and 12 are located at the same level in the momentary angular position of the crankshaft 14. The drive 15 for rotating the crankshaft 14 in order to lift or lower the straightening rolls 8, I0, 11 and I2 is preferably mounted somewhere adjacent to a median portion of the crankshaft. As shown in FIG. 1, such drive may be mounted at or close to the strightening unit 3. Each of the units 2, 3, 4 and 5 is mounted on a substantially C-shaped frame member 42 of the machine 1 (see FIGS. 34) and the means for feeding fresh workpieces 60 into the machine 1 (i.e., between the straightening rolls of the units 2-5) comprises a slightly inclined chute 160 having a stop 160a over which the foremost workpiece 60 must be lifted in order to enter the path wherein it moves lengthwise during engagement with and resulting straightening by the rolls of the units 2-5. A finished workpiece 62 can be evacuated from the machine by a conveyor including a series of rollers 63 (one shown in FIG. 3). Such finished workpiece is first moved sideways to leave the units 25 and to descend onto the rollers 63 of the just mentioned conveyor, and thereupon begins to move lengthwise, either to storage or to a further processing station, not shown. However, it is equally within the purview of the invention to use a second chute which is then located to the right of the row of units 2-5, as viewed in FIG. 3, and to cause successive finished workpieces 62 to roll along the upper side of such second chute to be temporarily stored in the machine 1 prior to removal by instrumentalities or conveyor means of any known design.

The drive 15 for the crankshaft 14 is shown in FIG. 6. This drive comprises a fluidoperated motor here shown as a double-acting hydraulic cylinder 17 which is mounted in or on the frame member 42 for the strightening unit 3 and has a piston (not shown) connected with an upwardly extending piston rod 16. The upper end portion of the piston rod 16 is articulately connected with a lever 18 by a pin 16a, and the lever 18 can turn about the axis of a horizontal pivot member 20 which is mounted in the frame member 42. The lever 18 is rigid with a gear 119, here shown as a segment, which is in mesh with an output element or a gear 21 on a stub 14b of the crankshaft 14. The ratio of the power train or transmission including the

gears

19, 21 and/or the length of strokes of the piston rod 16 can be readily selected in such a way that the double cranks 14a of the crankshaft 14 can lift the respective straightening rolls 8, 10, 11, 12 to a level which is needed for unimpeded introduction of fresh workpieces 60 and/or for unimpeded removal of finishes workpieces 62. The chambers of the cylinder 17 receive or discharge fluid by way of

conduits

23 and 24.. FIG. 6 further shows a valve 22 which is installed in the conduit 24 and serves to admit metered quantities of pressurized hydraulic fluid into the upper chamber of the cylinder 17, to permit evacuation of metered quantities of fluid from the upper chamber, or to seal the upper chamber from the source of pressurized fluid and from the tank. The valve 22 may be controlled by a programming device of any known design which is not shown in the drawing. A similar valve may be installed is not shown in the drawing. A similar valve may be installed in the conduit 23 to control the flow of fluid into and from the lower chamber of the cylinder 17.

As shown in FIGS. 2, 3, 6 and 7, the crank pin of each double crank 14a is surrounded by the strap of a connecting rod or displacing means 64 which is aritculately connected to the upper end portion of a reciprocable pushpull rod 25. The lower end portion of the rod 25 carries an inverted U-shaped bearing member 41 for the respective

upper straightening roll

8, 10, 11 or 12. Each rod 25 is guided for vertical movement in the respective frame member 42.

The aforementioned adjusting shaft 13 can adjust the level of upper straightening rolls 8, 10, 11 and 12 independently of the crankshaft 14 in a manner as shown in FIGS. 2 and 6. The shaft 13 carries bevel gears 26, one for each of the units 2-5, which mate with bevel gears 27. Each bevel gear 27 forms part of a gear cluster which further includes a spur gear 28 in mesh with a much longer spur gear 29 on the upper portion 65 of the respective rod 25. The lower end portion of each upper portions 65 constitutes a feed screw which meshes with a spindle nut of the lower portion of the respective rod 25. The lower portion of the rod 25 is held against rotation with respect to the corresponding member membeer 42 so that, when the shaft 13 is rotated to rotate the respective gear 29, the lower portion of the rod 25 and the corresponding bearing member 41 simply move up or down to thereby change the dimensions of the passage for a workpiece 60. The upper portion 65 of the rod 25 is held against axial movement by the corresponding connecting rod 64. The axial length of each gear 29 is sufficient to insure that this gear remains in mesh with the associated gear 28 when the rod 25 is moved up or down in response to angular displacement of the crankshaft 14.

FIGS. 8 and 9 illustrate a modified drive 115 for the crankshaft 14. The frame member 42 of the machine which embodies the drive 115 supports a horizontal shaft 35 which is keyed to a gear 37. The latter can rotate an output element or gear 39 on the adjacent portion of the crankshaft 14 by way of an intermediate gear 38. Each of the

gears

37, 38, 30 may be a twin gear (see FIG. 9). The shaft 35 supports two

pulleys

30, 31 each of which has several peripheral-grooves for V-

belts

32, 33. The

belts

32, 33 are respectively driven by additional pulleys (not shown) which receive torque from a prime mover, e. g., an electric motor which can rotate the

pulleys

30, 31 through angles of preselected magnitude.

The pulley 31 can rotate the shaft 35 through the medium of a disk-shaped coupling member 43 which is keyed to one end portion of the shaft 35 (see FIG. 9), whereby the shaft 35 rotates the gear 37. The reference character 40 denotes in FIG. 8 a push-pull rod which is a functional equivalent of the aforedescribed rods 25. The transmission ratio of

gears

37, 38, 39 is selected with a view to insure that the upper straightening rolls 8, 10, 11 and 12 are lifted simultaneously through a predetermined distance in response to a predetermined angular displacement of the shaft 35 from a starting position in which the

rolls

8, 10, 11 and 12 are nearest to the corresponding

rolls

7, 9 and cooperate therewith to straighten a section of a freshly introduced workpiece 60.

The pulley 30 is drivingly connected with the shaft 35 by a second coupling member 34 which is axially movable therewith so as to move a ring-shaped lining 30a of the pulley 30 into frictional engagement with a brake disk 36 on the frame member 42'. In this manner, the shaft 35 can be arrested in a predetermined angular position by the simple expedient of moving the coupling member 34, pulley 30 and lining 30a in a direction toward the stationary brake disk 36.

When the

rolls

8, 10, 11, 12 are in engagement with a freshly introduced workpiece 60, the pins of all double cranks 14a preferably assume their lowermost positions (see FIG. 8). In lifting the rods 40 and the corresponding upper rolls 8, 10, ll, 12 above and away from a straightened workpiece 62, the pulley 30 preferably alternates with the pulley 31 in transmitting torque to the crankshaft 14. It is preferred to drive the pulley 30 or the

pulleys

30, 31 by an electric motor through the medium of an infinitely variable-speed transmission to thus properly control the disengagement of vertically movable rolls 8, l0, 1 l, 12 within the all-important stage of transition from plastic deformation to elastic deformation of the material of the workpiece. Such transition must be gradual and uniform for all of the workpiece portions which are engaged by the straightening rolls. The motor and transmission may be of conventional design.

The pulley 31 preferably further serves as a flywheel.

It has been found that the transition from plastic to elastic deformation of a workpiece during lifting of rolls 8, 10, ll, 12 should take place while the straightened workpiece 62 performs several revolutions about its own axis; otherwise, the rolls 8, 10, ll, 12 would cause a permanent deformation (bending) of the workpiece 62 during upward movement in response to rotation of the crankshaft 14. A suitable sequence of angular displacements of the crankshaft 14 is shown in FIG. 5. When a

roll

8, 10, 1,1 or 12 engages a workpiece 60 to cooperate with the corresponding

rolls

7, 9 in performing a straightening action, the crank pin of the respective double crank 14a assumes the lower end position 45 of FIG. 5. When the crank 14a is turned through 180 the crank pin assumes the upper end position 44. The reference character 46 denotes an intermediate position of the crank pin.

The rate at which the

rolls

8, 10, 11, 12 are moved downwardly into engagement with a fresh workpiece 60 is of no particular importance because the duration of a straightening action is sufficient to insure repeated flexing of a rotating workpiece during lengthwise movement from the frame member 6 toward the frame member 6a so that the rolls of the units 25 have ample opportunity to straighten the workpiece by flexing it beyond the elastic limit (when necessary) while the workpiece moves lengthwise. On the other hand, the initial lifting of rolls 8, l0, l1 and 12 upon completion of a straightening operation should be gradual and rather slow so that the workpiece 62 can complete several (e.g., three or four) revolutions about its axis while the

rolls

8, 10, 11 and 12 rise above and away from the associated rolls 7,9. This insures a gradual reduction of flexing of the workpiece beyond the elastic limit. The length of the interval which is required to move a crank pin from the position 45 to the position 46 of FIG. 5 is variable because it depends from the diameter of a workpiece 62 (such diameter determines the number of rotations of a workpiece about its own axis per unit of time). Another factor which determines the length of the interval which elapses during movement of a crank pin from the position 45 to the position 46 of FIG. 5' is the speed at which the workpiece moves lengthwise, i.e., the overall length of the time which is alloted for the straightening of a workpiece.

The length of the interval which elapses during movement of a crank pin from the position 46 (when the respective roll 8, l0, 11 or 12 is disengaged from a straightened workpiece 62 or is sufiiciently lifted to cause a mere elastic deformation of such workpiece) to the position 44 and back to the position 45 (engagement with a fresh workpiece 60) depends on the nature of instrumentalities which are used to transfer a workpiece 62 from the four pairs of

rolls

7, 9 onto the rollers 63 and to thereupon place a fresh workpiece 60 onto the four pairs of

rolls

7, 9. Such interval may be extremely short if the means for removing workpieces 62 and feeding workpieces 60 operates automatically and is driven by a high-speed prime mover.

FIGS. 1, 2, 4 and 7 further show tubuler guides which extend between the frame members 6, 6a and are interrupted in the region of each straightening unit. Each of these guides has a semicylindrical upper section or shell 55a which must be lifted with the rolls 8, l0, 1 1, 12 prior to feeding of a workpiece and prior to removal of a workpiece 62. The means for moving the sections 55a derives motion from the crankshaft 14. The crankshaft 14 carries pairs of eccentric cams 54 having tracks 61 for roller followers 60 on straps 56 which are articulately connected to vertically reciprocable coupling bars 59 guided in rails 57 of the respective frame members 42. The bars 59 reciprocate between pairs of rollers 58 in the respective rails 57 and their lower end portions are rigid with the corresponding sections 55a. The lower sections of the guides 55 are mounted in the frame la.

The motor 17 exhibits the advantage that it can change the angular position of the crankshaft 14 with a high degree of accuracy. Moreover, its controls are simple, rugged and reliable. Such motor will be used when the machine comprises one or more additional fluid-operated components so that the provision of a source of pressurized fluid is not necessary solely for the purpose of operating the motor 17. The valve 22 insures that the movements of rolls 8, 10, l l and 12 between their extended and retracted positions can be regulated with a high degree of accuracy and reproducibility, and that the speed of these rolls can be changed during any selected stage of movement between extended and retracted positions. As mentioned above, the

rolls

8, 10, 11, 12 can be rapidly moved to their extended or operative positions as well as during the last stage of movement to retracted positions (i.e., subsequent to disengagement from a straightened workpiece 62). The movements of

rolls

8, 10, 11, 12 during the initial stage of travel from extended positions must be regulated with a high degree of accuracy; for example, the valve 22 of FIG. 6 can be operated by a suitable electronic control unit including a relay 22a. This insures a gradual disengagement of rolls 8, 10, ll, 12 from a straigtened workpiece 62 during the critical stage of aforementioned transition from plastic to elastic deformation.

It has been found that the crankshaft 14 is capable of moving the rolls 8, 10, ll, 12 in exact synchronism with each other and that minor elastic deformations of the cranks 14a as a result of torsional stresses are of no consequence, especially if the crank pins of the cranks 14a are in their lower end positions while the rolls 8, 10, ll, 12 cooperate with the

respective rolls

7, 9 to straighten a workpiece 60. Moreover, the torsional moment is practically zero when the crank pins assume their lower end positions (corresponding to the position 45 shown in FIG.

The means for rotating the

rolls

7, 9 of each of the four units 25 is of conventional design and is not shown in the drawing. The inclination of the axes of the rolls with respect to the axis of a workpiece 60 in the units 2-5 is such that the workpiece is compelled to rotate and to move axially in response to rotation of the rolls.

The placing ofthe

output element

21 or 39 of the

drive

15 or 115 substantially or exactly midway between the ends of the crankshaft 14 reduces the likelihood of twisting of the crankshaft when the piston rod 16 pivots the lever 18 or the

pulleys

30, 31 rotate the shaft 35. This also contributes to more satisfactory synchronization of movements of

upper rolls

8, 10, 11, 12 between extended and retracted positions and reduces in half the magnitude of torque which the crankshaft 14 must transmit in response to rotation by the motor 17 or

pulleys

30, 31.

The

pulley

30 and 31 rotates the shaft 35 at a relatively high speed during rapid movement of rolls 8, l0, l1, 12 to extended positions and during the second stage of movement of such rolls to retracted positions. The

pulley

31 or 30 then rotates the shaft 35 at an accurately controlled speed during the initial stage of movement of rolls 8, 10, l1 and 12 from extended positions, again for the purpose of insuring a gradual transition from plastic to elastic deformation of a workpiece 62. As mentioned before, such transition preferably takes place while the workpiece 62 completes several revolutions about its own axis.

The embodiment of FIGS. 8 and 9 is preferred when the machine does not comprise any parts which must be moved by fluid-operated motor means. The

pulleys

30, 31 are then driven by :a variable-speed electric motor or by a constant-speed motor through the medium of an infinitely variable-speed transmission.

In each embodiment of the invention, the crankshaft 14 preferably completes one-half of a revolution in order to move the rolls 8, l0, 1 l, 12 to extended or operative positions, and one-half of a revolution to move these rolls to the retracted positions in which a workpiece or 62 can be fed into or removed from the units 2-5. As mentioned above, eventual deformation of the crankshaft 14 as a result of torsional stresses is least damaging in the upper and lower end positions of the crank pins. Therefore, the crank pins preferably assume their upper end positions (44 in FIG. 5) in the fully retracted positions of the

rolls

8, 10, 11, 12 and their lower end positions (45 in FIG. 5) in the fully extended positions of the

rolls

8, 10, 11 and 12. Moreover, such mode of operation reduces the energy requirements of the motor 17 or of the motor means which drives the

pulleys

30, 31.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of our contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by letters Patent is set forth in the appended claims.

1. In a straightening machine for elongated tubular or rod-shaped workpieces, a combination comprising an elongated frame; a row of straightening units mounted in said frame, each of said units including a group of straightening rolls, at least one roll of each of said groups being movable between an extended position of engagement with a workpiece: and a retracted position in which a workpiece is insertable into and removable from said units; and means for moving said movable roll between said positions thereof, including a single shaft rotably mounted in and extending lengthwise of said frame, and having a plurality of eccentric portions, one for each unit, connecting rod means between each of said eccentric portions and the movable roll of the respective unit, and drive means for rotating said single shaft through an angle so that said eccentric portions are in one of the dead center positions when said movable rolls are in their extended positions.

2. A combination as defined in claim 1, wherein said single shaft is a crank shaft and each of said eccentric portions is constituted by a double crank.

3. A combination as defined in claim 1, and including means for simultaneously adjusting the length of all of said connecting rod means.

4. A combination as defined in claim 1, wherein each of said connecting rod means comprises a pair of telescoping members, one member of each pair including a screw portion meshing with a spindle in the other member, means for holding said other member against rotation, and means for simultaneously rotating said one member of all connecting rod means and including a second shaft rotatably mounted in and extending lengthwise of said frame, a long spur gear fixedly mounted in said one member of each connecting rod means, a short spur gear for each long spur gear and meshing therewith and tumably mounted on said frame, and gear transmission means on said second shaft for simultaneously rotating all of said short spur gears upon rotation of said second shaft.

5. A combination as defined in claim 1, said drive means having an output element connected with an intermediate portion of said shaft.

6. A combination as defined in claim 5, wherein said drive means further comprises a second shaft, a power train connecting said second shaft with said intermediate portion of said first mentioned shaft, said power train including said output element, and means for rotating said second shaft including at least one pulley on said second shaft, coupling means connecting said pulley to said second shaft, and at least one belt for rotating said pulley.

7. A combination as defined in claim 6, further comprising a brake actuatable to arrest said second shaft in predetermined angular positions thereof.

8. A combination as defined in claim'6, wherein said means for rotating said second shaft comprises two discrete pulleys on said second shaft, discrete couplings connecting said pulleys to said second shaft, and discrete belts for rotating said pulleys.

9. A combination as defined in claim 5, wherein said drive meaans further comprises a fluid-operated motor and a power train connecting said motor with said intermediate portion of said shaft, said power train including said output element.

10. A combination as defined in claim 9, wherein said power train includes a transmission.

11. A combination as defined in claim 9, wherein said drive further comprises means for metering the flow of a pressurized fluid to said motor.

12. A combination as defined in claim 1, said drive means for rotating said shaft including a gear transmission having a first gear rigid with said shaft and a second gear meshing with said first gear.

13. A combination as defined in claim 1, further comprising tubular guides for workpieces in said units, said tubular guides flanking said units and each thereof comprising a first section and a second section movable away from the respective first section to allow for introduction of fresh workpieces and for removal of straightened workpieces, and means for moving said second sections away from the respective first sections in response to rotation of said shaft to move said movable rolls to retracted positions.

14. A combination as defined in claim 13, wherein said means for moving said second sections comprises cams on said shaft and followers connected with said second sections and tracking said cams.

15. A combination as defined in claim 1, further comprising means for feeding workpieces sideways into said straightening units.

16. A combination as defined in claim 1, further comprising means for adjusting said movable rolls with respect to the other rolls of the respective groups independently of said shaft.

Claims

1. In a straightening machine for elongated tubular or rodshaped workpieces, a combination comprising an elongated frame; a row of straightening units mounted in said frame, each of said units including a group of straightening rolls, at least one roll of each of said groups being movable between an extended position of engagement with a workpiece and a retracted position in which a wOrkpiece is insertable into and removable from said units; and means for moving said movable roll between said positions thereof, including a single shaft rotably mounted in and extending lengthwise of said frame, and having a plurality of eccentric portions, one for each unit, connecting rod means between each of said eccentric portions and the movable roll of the respective unit, and drive means for rotating said single shaft through an angle so that said eccentric portions are in one of the dead center positions when said movable rolls are in their extended positions.

4. A combination as defined in claim 1, wherein each of said connecting rod means comprises a pair of telescoping members, one member of each pair including a screw portion meshing with a spindle in the other member, means for holding said other member against rotation, and means for simultaneously rotating said one member of all connecting rod means and including a second shaft rotatably mounted in and extending lengthwise of said frame, a long spur gear fixedly mounted in said one member of each connecting rod means, a short spur gear for each long spur gear and meshing therewith and turnably mounted on said frame, and gear transmission means on said second shaft for simultaneously rotating all of said short spur gears upon rotation of said second shaft.

8. A combination as defined in claim 6, wherein said means for rotating said second shaft comprises two discrete pulleys on said second shaft, discrete couplings connecting said pulleys to said second shaft, and discrete belts for rotating said pulleys.