FR2688435A1 - Device for tapping on a press - Google Patents

Abstract

Device for tapping on a press (13, 4), this tap for example forming part of a tool to be followed (chased). It includes a lead screw (11) including a ball cage (20) in the form of a column placed between the fixed screw (18) and the driving rotary nut (16) which it drives. Each tap-holder spindle (32, 33) is mounted in a solid sliding component (34). The driving nut (16) causes rotation of a cam (26), the lift of which is transmitted, via a sliding carriage (46) with bearing ramp (52), to rollers (45) secured to this solid component (34), which comes to push the tap (33) toward the orifice (1) to be tapped and engages it therein by just a few turns: it then continues its tapping travel by itself.

Description

PRESS TAPPING DEVICE
The present invention relates to an automatic tapping device on a press, for example on a cutting or stamping press.

 It is known from document EP-A-192586 an automatic tapping device on a cutting or stamping press which comprises a "boss" screw with rapid pitch which is fixed and integral with the upper tool holder of the press, this patron screw being engaged with a nut which is movable only in rotation in a block integral with the lower tool holder of this press.

 Each time the upper plate of this press performs its downward movement, it drives with it this fast-moving boss screw, which rotates this nut. The latter consequently drives, by means of a kinematic transmission with toothed wheels meshing in each other, a hollow spindle in relatively slow rotation. This hollow spindle, whose axis is perpendicular to the press plates and is parallel to that or those of the tap holders and the boss screw, causes, by an internal thread, the displacement along this axis of a single support which carries this or these tap holders and, by an internal toothing, the rotation of this or these tap holders, the teeth and threads being determined so that each tap holder makes a revolution while it moves axially by the value of one step, which is the necessary condition for the execution of the tapping .

 This type of known device has some drawbacks - We know that a portion of the movement cycle of the platens of a press is devoted to the advance of the belt which carries the successive tests. During this portion of the cycle, no tapping can be carried out, but the taps still rotate while continuing to move axially. This makes it necessary to provide, for these taps, a total stroke which is much greater than the truly useful stroke. In addition, during this unnecessary movement of the taps, there is work and therefore unnecessary wear of the mechanics while the strip is advancing. Finally, it is therefore difficult to manage the movements: the assembly of each tool is complex because this unnecessary path must be taken into account to correctly position this tool so that it does not act too early or too late.

- The device cannot be made sufficiently tight to define a crankcase filled with oil, like for example gearboxes. It is indeed a thread which regulates and controls the advance and the retraction of the taps, and it is not possible to ensure such a seal on a thread. The parts are therefore greased, and it is therefore necessary to dismantle the assembly from time to time to put in new grease, which causes detrimental losses of time, and therefore of yield.

- Each tap is guided throughout its movement, while it would be sufficient that it is only during its first turns of tapping. I1 results in early wear of the bell thread which causes and guides its movement. However, if this thread is worn, the thread to be tapped is upset and the tapping is then defective.

- The boss screw drives the associated nut by a friction effect. The efficiency is thus far from being optimum and, the angle of inclination of the propeller relative to the horizontal not being able to exceed 45 degrees under penalty of damage, it is ultimately necessary, in order to obtain sufficient power, to '' opt for a screwdriver of large diameter, and therefore necessarily long stroke. To fix the ideas, it is practically necessary to provide a stroke of 70 to 80 mm to perform the tapping, which requires the use of long-stroke presses and ultimately penalizes the mechanical assembly in dimensions and cost.

- To change the tapping pitch, and therefore the taps, it is necessary to change the entire rotating head which carries and advances the tap holder pins. I1 is therefore necessary to provide as many heads, which are each of the multiple and relatively complex sets, that I 'provides no tapping.

 Note that replacing the boss screw used in this type of device with a commercial ball screw is difficult to imagine. On the one hand indeed, these ball screws are never fast for a reason of practical impossibility of realization. On the other hand, these ball screws require an associated system for recirculating the balls, which makes them quite complex and therefore ultimately rather expensive in terms of acquisition and maintenance costs.

 The invention aims to remedy these drawbacks. It relates to a tapping device on a press, this tapping device being, for example, part of a "tool to be followed", and comprising a device for transforming the translational movement of the movable plate of the press into a rotational movement, this device being of the screw-nut type and therefore comprising a screw-boss which is fixed in rotation and which is secured to the movable plate of the press, and a nut engaged with this vispatronne and movable only in rotation in an integral block of the fixed plate of the press, so that the downward or upward movement of the movable plate of the press causes the correlative rotation of this nut in a first direction or in the other respectively; a device for kinematically transmitting the movement of rotation of this nut in one direction as in the other to at least one tap-holding spindle for rotating the latter in a first and a second direction for respectively tapping the orifice to be tapped and then removing the tap from this orifice which it has just tapped; and means for advancing or retreating each tap spindle in a manner correlated with the rotation of this spindle to perform the tapping at the desired pitch, that is to say so that the tap performs a revolution while they are moving axially from the value of one step.

 According to the present invention, the latter means are distinct from the devices for rotating the tap pin or pins and they comprise at least one cam which is driven in rotation at slow speed by this nut and through another kinematic link. ; a sliding part which serves as support and bearings for this or these tap-holder pins, this part being movable only in translation in the direction of the tapping; transmission means which bear on the cam and which are capable of transforming the lifting of this cam into a correlative action of setting in motion this sliding part towards the orifice or orifices to be tapped, the rise of this cam being consequently calculated to not only cause, in the hole to be tapped, the axial displacement of the corresponding tap by the value of a step while this tap is making a full turn on itself, but also to be just sufficient to push each tap by only a few turns in 1 corresponding orifice, the tapping then continuing by itself and without pushing action on this sliding part, while at the return of the tap, the cam having a reverse movement, it then comes to drive, by 1 effect reverse, the positive guidance of the final movement of return of said sliding part to its starting point, this positive guidance taking place only on said first turns of the ta and thus avoiding the destruction of the nets corresponding to these first turns.

 Advantageously, said boss-screw is a very particular ball screw comprising, between the fixed rotating screw and the nut which it drives, a "ball-carrying column" trapping, like ball cages conventionally equipping certain ball bearings, balls spaced from each other and kept as in this ball-bearing column, this column being free to roll, by means of these balls - on the one hand around this fixed screw in rotation and against the threads of this same screw, the internal part of this column marrying with play the shape of these threads, - and on the other hand inside this nut and against the internal threads of this same nut, the external part of this column marrying with play the shape of these internal threads of the nut, so that finally, according to an operation modeled in reverse on that of the aforementioned ball bearings, the screw rotates this nut with a stroke of tra nslation which, for an equal number of turns of the nut, is equal to half of the stroke that would require carrying out a boss screw which would be in direct engagement with said nut.

 According to another advantageous embodiment, this patron screw consists of a circular cylindrical rod on which are fixed rollers arranged in at least two parallel series, each of these series being distributed from top to bottom of this rod and on a respective helical line winding around this rod at the same pitch as that of the internal threads of the nut, so that these helical series of rollers overlap in these internal threads, provided conjugate accordingly, of the nut and come to roll in the latter during the translational movement of this screw-boss.

In any case, the invention will be well understood, and its advantages and other characteristics will emerge during the following description of a nonlimiting exemplary embodiment, with reference to the appended schematic drawing in which
Figure 1 is an overall view in vertical and partial cross section of this tapping device on press; Figure 2 is an enlarged view, partly in section, of the screw-nut system which is used on this tapping device; Figure 3 is a horizontal and transverse section, taken along III-III of Figure 4, which shows the cam and the down carriage drive system associated therewith; Figure 4 is a vertical and longitudinal section, taken along
IV-IV of Figure 3, which explains the horizontal sliding of this pushing carriage; Figure 5 is a view similar to Figure 3, but showing an embodiment with several taps instead of one; and Figure 6 is a similar to Figure 2, and showing an alternative embodiment of this screw-nut system.

 Referring first to Figures 1 and 2, it is a tapping device on a press which is able to constitute, for example, one of the working elements of a "tool to follow" fixed on this press and performing, on successive tests fixed on the same strip, various other cutting, stamping, etc. operations.

 In this case, the purpose of this tapping machine is to tap an orifice 1 which is already made in a sheet metal plate 2. Although this is not shown in the drawing, the orifice 1 is actually a deep-drawn, or "jog" in terms of the trade, so as to appreciably increase the length of the thread thus tapped, this hole 1 is thus in reality a small tube which forms a protrusion downwards.

 This plate 2 is part of a series of tests which are linked together to form a strip which slides step by step in a groove 3, wide and shallow, provided for this purpose in the lower fixed plate 4 of the hurry. A longitudinal slot 5 is also naturally provided in this plate 4, in alignment with one orifice 1 to allow the crossing of the tap.

 The tapping device consists of two parts which are movable relative to each other a main block 6 which is mounted on the fixed lower plate 4 of the press, and which is therefore itself fixed in position.

Externally, this block 6 is in the form of a sealed casing 7, the interior space 8 of which is, like a gearbox, filled with lubricating oil, a plug 9 and a filling conduit 10 of oil being provided accordingly. This casing 7 is composed of two half-shells 7A and 7B assembled by screws 14 with the interposition of a seal 15.

 A patron screw it of axis perpendicular to the press plates, which is fixed by screws 12 on the movable upper plate 13 of the press, and which has the function of transforming the downward or upward movement of this movable upper plate 13 in a rotational movement, respectively in one direction or in the other, of a rotary nut 16 which is mounted on two rolling bearings 17 and which is mounted fixed in translation in the block 6. The tightness of this nut motor 16 is provided by seals 53 and 54.

 It is however here a particular screw-boss 11, which is shown in enlarged view in Figure 2, and whose very special operation will be understood by recalling the kinematic phenomena which are involved in known ball bearings which include an intermediate ball holding cage, known as a "ball cage".

 This type of known ball bearing has three elements - A central axis which is fixed in rotation and of circular section.

- A "ball cage", annular and madly mounted, which surrounds with play this central axis which can roll on it by means of the balls which it maintains and traps. These balls are crimped in a fixed position in this cage, but they can rotate freely on themselves.

- An outer annular wheel, which is the actual wheel which rolls for example on the ground. This wheel playfully surrounds this ball cage and therefore it rolls on the latter's balls.

 Finally, if the outer wheel rotates at a speed "v", it turns out, because the central axis does not rotate, that the ball cage then rotates at half speed, ie v / 2.

 It is this general property of these ball bearings which is used here, in a simple and original way, to obtain a screw-boss 11 which imposes on the nut 16 its rotational movement by a screw-nut transmission operating by rolling , therefore with a yield very close to 1, and not by friction, which allows the possibility of using a helix pitch of less than 45 degrees and consequently makes it possible to carry out the same work as with the fast-pitch screw. 1 prior art (see for example the screw with rapid pitch according to the document EP-A-192586 cited above) with a much lower stroke, without heating or risk of deterioration.

 Consequently, there is provided, between the fixed screw 18 with helical threads 19 and the rotary nut 16, a ball cage 20, which will rather be called "ball column", in the form of an elongated tube whose inner edges and outside are threaded and correspond, with play, to the helical threads, respectively outside and inside, of the fixed screw 18 on the one hand and of the nut 16 on the other hand.

 This tubular column 20 traps balls 21, which are crimped at equal distances from each other so as to be able to rotate freely on themselves and to slightly protrude from each side, inside and outside: finally, this column 20 is therefore mounted madly between the screw 18 and the nut 16 thanks to the balls 21, as is somewhat the case for ball bearings which include a ball cage, but however this column 20 is not blocked in translation and it can therefore freely move up or down by turning around the fixed screw 18. When the fixed screw 18 goes down or goes up, the ball column turns twice as fast as the nut 16 which it drives.

 One obtains here, in a remarkably simple manner, all the advantages linked to ball screws: efficiency almost equal to 1, negligible wear, possibility of much shorter stroke than for the conventional system, all this being due to the fact that the transmission of movement is done by rolling and not by friction.

 Returning now to Figure 1, the boss screw 11 therefore drives, in its vertical translational movement, the nut 16 in rotation. This nut 16 is provided, on its external part, with a toothed pinion 22 which meshes with another toothed pinion 23, of the same diameter, the shaft 24 of which is carried by two rolling bearings 25. On this shaft 24 is also fixed a cam 26 which will be discussed below.

 The pinion 23 is a simple intermediate pinion which drives another pinion 27 of half diameter, and which therefore rotates at an angular speed which is twice that of the intermediate pinion 23, and therefore also that of the motor pinion 22.

 This small pinion 27 is mounted on a shaft 28, itself carried by two rolling bearings 29, this shaft carrying another pinion 30 of much larger diameter.

 This pinion transmission assembly 23, 27 and 30 therefore constitutes a conventional speed reduction gearbox which drives, by a small pinion 31 which is integral with the tap pin 32 and which meshes on the pinion 30, this tap pin pin 32 at a speed of rotation significantly higher than that of the motor nut 16.

 The spindle 32, which carries the tap 33, is of course fixed in the axis of the orifice to be tapped 1. It is held in a solid part 34, of generally circular section, and in coaxial orifices 35 and 36 of the latter which allow it both to turn on itself with gentle friction as well as to be able, as a safety in the event of a tapping incident, to move slightly by sliding in the axial direction and therefore vertical.

 The pin 32 is in fact placed in a lateral cavity 37 of the solid part 34, where a coaxial spring 38 comes to push it firmly down. The pinion pinion 31 therefore comes to bear on the horizontal bottom of this cavity 37 by means of a sealing ring 39. In the event that the tap 33, during its downward movement towards the orifice 1 , accidentally encounters an unwanted obstacle, the spindle 32 then overcomes the repulsive force of the spring 38, which then compresses, thereby preventing the tap 33 from continuing its downward movement, and therefore from being damaged.

 The solid part 34 is itself vertically sliding mounted in a cylindrical chamber 40 of the casing 7, the seal being ensured by an annular seal 41. It is kept fixed in rotation by cooperation of a key 42 integral with the casing 7 and d 'a sliding groove 43 formed on a portion of its generatrix. This part 34 is normally pushed up by a spring 44 and, as can be seen in Figure 3, a push down, causing its vertical displacement and therefore the descent of the tap 33 can be applied to it 1 two rollers 45 of horizontal axis which are fixed on the part 34, on either side of a narrowed part 34A of the latter.

 This downward pushing results from the movement from right to left of a sliding carriage 46 (see also Figure 4) which passes on either side of the aforementioned part 34A and which, being pushed to the right by two springs 47 (Figure 3), comes to rest on the above-mentioned cam 26.

 In the position shown in Figures 1 and 3, the carriage 46 presses on the concentric part of the cam 26, the "lift" of which is therefore zero, and it is in its position of maximum recoil. I1 is the same for the part 34, and therefore for the tap 33.

 On the shaft 24 is fixed a small pinion 48 which meshes on three other rotary pinions 49 which themselves mesh on an internal toothing 50 of the cam 26, this assembly 48, 49, 50 forming a speed reducer, in itself very conventional, capable of transmitting, from the engine nut 16, a slow rotational movement to the cam 26, in one direction as in the other.

 Note that, apart from the boss screw 11 and the tap 33, the entire device is immersed in oil which fills the space 8, like a gearbox.

When, from the rest position according to the
Figures 1 and 3, the cam 26 is rotated, its lifting 26A pushes the carriage 46 to the left, a slide 51 (Figure 4) being provided to allow its easy sliding.

The thickness of the downstream part 46A of the carriage 46 is much greater than that of its upstream part 46B (see in
Figure 1), and these two parts of different thickness 46A, 46B are connected by two rectilinear ramps 52 at 45 degrees relative to the horizontal.

 By these two ramps 52, the carriage 46 comes, in sliding movement towards the left due to the thrust of the lifting 26A of the cam 26, to push progressively, by means of the rollers 45, the part 34 and therefore finally the tap 33, down. The tap, which is itself rotated by one through the gear transmission 31, 30, 27, 23, 22, then enters the orifice 1, and then begins its tapping operation.

 The lifting 26A of the cam is calculated, and therefore drawn, so that this tapping is carried out according to the required pitch, that is to say so that the tapping makes a full revolution on itself while it is moving axially from the worth a step. Ultimately, to change the tapping pitch, it suffices simply to change the cam 26, which is simpler and less expensive than the devices of the prior art.

 The aforementioned advance of the tap stops when, the ramp 52 having passed, the rollers 45 come to roll on the upstream portion 46B of greater thickness. The cam lift is then at its maximum point 26C. This advance, and therefore the difference in thickness between the parts 46A and 46B of the carriage, is determined so that the tap is then simply engaged with a few threads in the orifice 1.

 The engine nut 16 then continues to rotate, and the tap 33 then continues by itself its tapping operation, without pushing it down, which is no longer necessary at this stage.

 Note that, the lifting point 26C of the cam being exceeded, the carriage 46 then returns back and then no longer presses on the rollers 45, which is immaterial because the force of the spring 44 is not considerable.

 At the end of the downward movement of the boss screw 11, the tapping is finished, and this boss screw rises with the upper plate 13 of the press, thus causing the engine nut 16 to rotate in the opposite direction.

 All reverse phenomena then occur. The tap 33 is unscrewed from the threaded orifice 1 and, when there are only a few threads of the tap engaged in this orifice, the rollers 45 come to bear against the portion of greater thickness 46B of the carriage 46, which has been re-advanced accordingly by lifting the cam. The rotation of the cam 26 continuing, the carriage gradually recedes while the rollers 45 roll on the slopes then descending 52. The carriage 46 then plays a guiding role with retention of the part 34, and therefore of the tap 33, which avoids that the first threads of the tapped orifice 1 are not torn off by this tap 33 due to the repulsive force of the spring 44.

 At the end of the ascent stroke of the boss screw 11, the positions are those of departure which are apparent in FIG. 1.

 FIGS. 1 to 4 which have just been described relate to a tapping machine equipped with a single tap, and therefore with a single tapping spindle 32 driven by a pinion 31.

 It goes without saying that this device can be produced in the same way with several taps, as illustrated in FIG. 5 where one uses four taps, and therefore four tap holder pins 32A to 32B, each with their drive pinion. , respectively 31A to 31D. In such a case, the toothed pinion 30 drives, in itself in a very conventional manner, an auxiliary toothed crown 55 by the external toothing 56 of the latter, while the internal toothing 57 of this crown 55 meshes on the four pinion pinions 31A at 31C.

 The downstream part of the carriage 46 is then, as before, shaped to pass next to the pins 32A, 31A to 32C, 31C: in this case, it passes between these pins (and not on either side as in Figure 3 ) and it carries only one thrust roller 45. The shape of the solid part 34 is there still suitable for letting the carriage 46 pass: it is therefore here pierced with a central groove 58 for passage of this carriage.

 Referring finally to FIG. 6, an alternative embodiment of the screw-nut drive system of FIG. 2 is shown.

 According to this variant, the boss screw 11 consists of a circular cylindrical rod 60 on which are fixed rollers 61 arranged in two parallel series 62,63, each of these series being distributed from top to bottom of the rod 60 and on a respective helical line 64,65 winding around this rod at the same pitch as that of the internal threads 66 of the nut 16, so that these 62,63 series of rollers 61 overlap in these internal threads 66, provided consequently, of the nut 16 and come to roll in the latter during the translational movement of this patron screw 11.

 It goes without saying that the invention is not limited to the embodiment which has just been described, and on the contrary is capable of being implemented by the application of numerous equivalent means. This is how, for example, the kinematic transformation with a carriage 46 of the lifting of the cam 26 into a pushing down, or retaining, force of the part 34 could be carried out by conventional means of hydraulic force transmission. , comprising a piston actuated at the level of the cam lift and a hydraulic transmission of the driving-in movement of this piston under the thrust of the cam rise to another piston capable of exerting downward pressure on the part 34. This is also how the vispatronne according to FIG. 6 could comprise more than two parallel series of rollers 61, the internal threads 66 of the nut 16 then being of course provided conjugated accordingly.

Claims (9)

1 - Tapping device on press (4, 13) comprising a device for transforming the translational movement of the movable plate (13) of the press into a rotational movement, this device being of the screw-nut type and therefore comprising a screw-boss (11) which is fixed in rotation and which is integral with the movable plate (13) of the press, and a nut (16) engaged with this screw-boss and movable only in rotation in a block (6) integral of the fixed plate (4) of the press, so that the downward or upward movement of the movable plate (13) of the press causes the corresponding rotation of this nut (16) in a first direction or in the other respectively; ;  a device (23,27,30,31) for kinematic transmission of the rotational movement of this nut (16) in one direction as in the other to at least one tap-holding spindle (32) for rotating the latter in a first and a second direction for respectively tapping the orifice (1) to be tapped and then removing the tap (33) from this orifice which it has just tapped; and means for advancing or reversing each tap spindle (32) in correlation with the rotation of this spindle to perform the tapping at the desired pitch, that is to say so that the tap (33) makes a turn while it moves axially by the value of one step, characterized in that these latter means are distinct from the device for rotating the tap pin or pins and comprise at least  a cam (26) which is rotated at low speed by this nut (16) and through another kinematic link (23,49,50); a sliding part (34) which serves as support and bearings for this or these tap-holder pins (32), this part (34) being movable only in translation in the direction of the tapping; transmission means (46,52,45) which bear on the cam (26) and which are capable of transforming the lifting (26A) of this cam into a correlative action of setting in motion this sliding part (34) towards the opening (s) (1) to be tapped, the rise of this cam (26) being consequently calculated to not only cause, in the opening (1) to be tapped, the axial displacement of the corresponding tap (33) by the value d '' a step while this tap makes a full turn on itself, but still to be just sufficient to push each tap (33) by only a few turns in 1 corresponding hole, the tapping then continuing by itself and without pushing action on this sliding part (34), while at the return of the tap (33), the cam (26) having a reverse movement, the positive guidance of the final movement of return of said sliding part to its starting point is in reverse provided by this cam and these means of tr ansmission associated, this positive guidance being carried out only on said first turns of the tapping and then making it possible to avoid destruction of the threads corresponding to these first turns. 2 - Tapping device according to claim 1, characterized in that said boss-screw (11) is a very special ball screw comprising, between the fixed rotating screw (18) and the nut (16) which it drives , a "ball-bearing column" (20) trapping, like one ball cages conventionally equipping certain ball bearings, balls (21) spaced apart from one another and maintained as in this ball-bearing column (20), this column (20) being free to roll, by means of these balls (21) on the one hand around this fixed screw in rotation (18) and against the threads (19) of this same screw, the internal part of this column (20) conforming playfully to the shape of these nets,  and on the other hand inside this nut (16) and against the internal threads of this same nut, the external part of this column (20) conforms with play to the shape of these internal threads of the nut (16) . 3 - Tapping device according to claim 1, characterized in that the boss screw (11) consists of a circular cylindrical rod (60) on which are fixed rollers (61) arranged in two parallel series (62,63 ), each of these series being distributed from top to bottom of the rod (60) and on a respective helical line (64,65) winding around this rod at the same pitch as that of the internal threads (66) of 1 nut (16), so that these series (62,63) of rollers (61) overlap in these internal threads (66), provided conjugate accordingly, of the nut (16) and come to roll in the latter during the translational movement of this patron screw (11). 4 - Tapping device according to one of claims 1 to 3, characterized in that said means for transmitting the cam lift (26A) are kinematic means which comprise a carriage (46) capable of sliding transversely and having two parts of different thicknesses, including a downstream part (46A) which is thinner than the upstream part (4613), these two parts being connected by an inclined ramp (52), and the cam (26) causing, in its rotation, the transverse movement of this carriage, so that the latter comes, during the cam lift (26A), push by this ramp (52) on one or more rollers (45) which are integral with said sliding part (34) of support of the tap-holder pins (32) and thereby lower this or these taps (33) in the direction of the orifice (s) to be tapped (1). 5 - Tapping device according to claim 4, characterized in that said ramp (52) is a ramp at 45 degrees relative to the horizontal. 6 - Tapping device according to one of claims 1 to 5, characterized in that, apart from the boss screw (11) and the tap or taps (33), it is placed in a sealed casing (7) which is filled dt lubricating oil like a gearbox. 7 - Tapping device according to one of claims 1 to 6, characterized in that there is provided a set of cams (26) spare, the lift (26A) of each cam being calculated and drawn according to the pitch of desired tapping. 8 - Patron screw (11) for the transformation of a translational movement which is imparted to it into a rotational movement of a nut (16) engaged with this screw (11), in particular for tapping device on press, characterized in that this boss screw (11) is a very special ball screw comprising, between the fixed rotating screw (18) and the nut (16) which it drives, a "ball-carrying column" (20 ) trapping, like ball cages conventionally fitted to certain ball bearings, balls (21) spaced from one another and maintained as in this ball carrier column (20), this column (20) being free to roll, via these balls (21)  d on the one hand around this fixed rotating screw (18) and against the threads (19) of this same screw, the internal part of this column (20) matching the shape of these threads with play,  and on the other hand inside this nut (16) and against the internal threads of this same nut, the external part of this column (20) conforms with play to the shape of these internal threads of the nut (16 ).  9 Dis - Screw-nut device, in particular suitable for equipping a tapping device on a press, and intended to transform a translational movement of a screw-boss (11) fixed in rotation into a rotary movement of a nut (16) engaged on this boss screw (11) and fixed in translation, characterized in that this boss screw (11) consists of a circular cylindrical rod (60) on which are fixed rollers (61) arranged according to two parallel series (62,63), each of these series being distributed from top to bottom of the rod (60) and on a respective helical line (64,65) winding around this rod at the same pitch as that of the internal threads (66) of the nut (16), so that these series (62,63) of rollers (61) overlap in these internal threads (66), provided conjugate accordingly, of the nut (16 ) and come to roll in these during the translational movement of this screw-boss (11)