EP3112044A1

EP3112044A1 - Rolling machine for forming threads on cylindrical bodies and process for phasing together forming rollers of a rolling machine

Info

Publication number: EP3112044A1
Application number: EP16174153.3A
Authority: EP
Inventors: Pietro Farina
Original assignee: Mico Srl
Current assignee: Mico Srl
Priority date: 2015-07-02
Filing date: 2016-06-13
Publication date: 2017-01-04
Anticipated expiration: 2036-06-13
Also published as: EP3112044B1; ITUB20151836A1

Abstract

Rolling machine for forming a thread on cylindrical bodies, which comprises two or more forming rollers (6), mechanically associated with the support structure (2) and adapted to plastically deform a cylindrical body arranged along a central work axis (A) of the machine (1). Each forming roller (6) is provided with a thread (8), is driven to rotate around its rotation axis (Z) by a brushless motor (16) and is driven to be moved along a respective first transverse axis (R) perpendicular to the work axis (A) by a corresponding hydraulic piston (15). Sensor means (30) are provided that are mechanically mounted on the support structure (2) and drivable to be moved by movement means (35) between a non-operative position (P1), in which they are in distal position with respect to the forming rollers (6), and an operative position (P2), in which they are in proximity to at least one forming roller (6) in order to detect the axial position of its thread. The invention also relates to a process for phasing the forming rollers of such a rolling machine.

Description

Field of application

The present invention regards a rolling machine for forming threads on cylindrical bodies and a process for phasing together the provided forming rollers of the aforesaid rolling machine, according to the preamble of the respective independent claims.
The present rolling machine and process are inserted in the industrial field of precision mechanical processing attained by means of cold plastic deformation and capable of conferring high mechanical performances to the metal components, in particular toughness and fatigue strength.
The machine and the process, object of the invention, are advantageously intended to be employed for making threads of any type (metric, whitworth, ISO, GAS, etc.) on metal cylindrical bodies such as shafts, bars, rods etc.

State of the art

The rolling machines of known type, currently available on the market, usually comprise two or more forming rollers mounted on a support structure, each of which provided with a thread. The threads of the rollers cooperate with each other in succession in order to plastically deform the surface of a cylindrical body placed along a central work axis in order to attain the desired thread thereon.
Hereinbelow, the expression "cylindrical body" will indicate the mechanical member or piece, whether a shaft, a bar, a rod or other, on which it is wished to obtain the desired thread.
As is known, the forming by means of cold plastic deformation allows obtaining mechanically threaded bodies that are particularly strong, since the metallic fibers of the body subjected to processing are not cut as in a normal milling process.
During the rolling process, the thread receives forging properties which contribute to considerably increasing the fatigue strength of the material and the static load at the base of the thread. The mechanical strength of the thread obtained via deformation with a rolling machine is on the order of 30% greater than that obtainable with a normal cutting process.
More in detail, each forming roller is mounted on a tool holder shaft or mandrel and is driven to rotate by a corresponding motor; in addition, each forming roller is also controlled to be moved by a corresponding actuator along a transverse axis substantially perpendicular to the work axis in order to impart, by means of compression with its thread, an impression on the metal body to be formed.
The cylindrical body to be formed is supported at the center of the work axis by a suitable support and is cold deformed by the threads of the forming rollers, which compress such body by rotating thereon.
The single forming rollers are adapted to successively form the desired thread on the metal body to be processed, and for such purpose the thread of each roller must follow, in an extremely precise manner, the impression made on the metal body by the thread of the preceding forming roller.
The processing operations are controlled by means of a logic control unit, preferably of numeric control type directed by an external computer (CNC).
The logic control unit receives the instructions from the operator by means of a work program that uses, for example, a standardized ISO code language.
Since the radial compression stresses and axial shear stresses that affect both the cylindrical body and the thread of the forming roller are very high, generally two or more forming rollers are used in a manner such to equally distribute the stresses and avert breakage risks.
Each forming roller, when driven to rotate via motor means, carries out an angular movement that corresponds to an axial movement of the thread on the external lateral surface of the forming roller itself, since the threads are wound as a spiral in the axial direction.
More clearly, as is known, the cylindrical body during its processing advances axially and rotates in contact with the forming rollers. The impression imparted on the cylindrical body by a forming roller carries out an angular and axial movement during the passage to the subsequent forming roller, which must exactly follow the impression of the preceding roller. For such purpose, the axial distance followed by the groove of the cylindrical body, verified following the angular movement of the cylindrical body itself, must be equal to the axial distance between the point of disengagement of the thread of the first forming roller and the point of engagement of the thread of the subsequent forming roller.
It is thus necessary to know the precise axial position of the thread of each forming roller with respect to an angular reference position and hence the mutual axial positions of the threads of the forming rollers.
Currently, machines and processes able to detect the precise position of the thread of the forming rollers are not known.
Therefore, a problem affecting the field of rolling machines is that of defining, with extreme precision, the relative position of the forming rollers such that the impression made by a roller on the cylindrical body is correctly and precisely followed in a precise manner by that made by the subsequent forming roller.
Generally, the process of production of the forming rollers does not provide for references that allow mounting the forming roller on the tool holder shaft in a precise precision.
The seat of the key on the forming roller, for the mounting on the tool holder shaft, is in fact normally obtained without considering the relative position of the thread.
Of course, the angular position of the tool holder shaft is precisely controlled, since it is driven to rotate by electric motors of brushless type, which allow knowing the precise position and angular speed of the drive shaft and hence of the tool holder shaft connected to the drive shaft by means of a transmission such as a universal joint.
In common practice, the operator places the forming rollers in phase with each other, in a manual manner by using suitable adjustment knobs provided for each of the forming rollers that are susceptible of imparting small angular movements to the same rollers.
Such phasing process provides for the use of test pieces, generally made of plastic or soft iron material, on which processing cycles are executed in order to receive the impressions of the threads of the single rollers.
The operator, after each processing cycle, controls the impression generated by the forming rollers on the test piece and makes the suitable corrections in the angular position of the single rollers.
Consequently, the position of the thread of each forming roller for the mutual phasing of the relative threads is defined through impression tests on samples through successive approximations.
In practice, such phasing process for the forming rollers has shown that it does not lack drawbacks.
One drawback lies in the considerable time necessary for defining the precise position of each forming roller. It must also be considered that the forming rollers must be substituted both in order to change processing type with other types with different characteristics, and in order to carry out normal maintenance in case of wear thereof. Therefore, the problem of phasing appears rather frequently.
The position of the forming rollers defined with such process is also not very precise and depends on the experience and capacity of the operator, who must control the impressions on the samples. Hence, the quality attained is hard to repeat and depends on the operator's ability.
Indeed, the control of the groove generated on the test piece or on the finished product is carried out visually by the operator himself/herself.
A further drawback lies in the high costs due to the numerous samples that must be employed in the phasing process or due to the cylindrical bodies with incorrect threads that must be discarded.
The patent DE 10011681 describes a rolling machine of known type, which comprises two forming rollers drivable by motor means to rotate around the rotation axis thereof in order to plastically deform a cylindrical body. In particular, the rolling machine comprises an optical sensor adapted to detect the axial reference coordinates for the processing of the cylindrical body to be formed.
Nevertheless, also the latter rolling machine of known type does not allow defining, in an optimized manner, the position of each forming roller.

Presentation of the invention

In this situation, the problem underlying the present invention is therefore that of overcoming the drawbacks manifested by the abovementioned solutions of known type by providing a rolling machine for forming threads on cylindrical bodies and a process for phasing together forming rollers of a rolling machine, which allow phasing the forming rollers in an automatic and fast manner.
A further of the present invention is to provide a rolling machine for forming threads on cylindrical bodies and a process for phasing together forming rollers of a rolling machine, which are precise and safe.
A further of the present invention is to provide a rolling machine for forming threads on cylindrical bodies and a process for phasing together forming rollers of a rolling machine, which are simple and inexpensive to make.
These and still other objects are all attained by the machine and by the process according to the enclosed claims.

Brief description of the drawings

The technical characteristics of the present invention, according to the aforesaid objects, can be seen in the contents of the below-reported claims and the advantages thereof will be clearer from the following detailed description, made with reference to the enclosed figures, which represent a merely exemplifying and non-limiting embodiment of the invention in which:

figure 1 shows a front perspective view of the rolling machine, object of the present invention;
figure 2 shows a substantially front view of a detail of the rolling machine of figure 1 relative to sensor means arranged in a non-operative position;
figure 3 shows the detail of figure 2 with the sensor means arranged in an operative position;
figure 4 shows the detail of figure 3 in which the sensor means are in operative position and intercept a forming roller;
figure 5 shows a rear perspective view of the rolling machine according to the invention with the motor means underlined;
figure 6 shows a perspective section of a detail of the rolling machine according to the invention relative to actuator means;
figure 7A schematically shows a substantially side view of a detail of the rolling machine according to the invention relative to one of the forming rollers;
figure 7B shows a detail of the forming roller of figure 7A in a longitudinal section view of its thread;
figure 8 schematically shows a detail of the rolling machine, object of the present invention, relative to sensor means with a discoid element thereof in tilted position.

Detailed description of some preferred embodiments

With reference to the enclosed drawings, reference number 1 overall indicates a rolling machine for forming threads on cylindrical bodies in accordance with the present invention.
This is generally intended to be employed for making the aforesaid threads on cylindrical bodies of mechanical members such as shafts, bars, rods etc., for many different applications.
The threads are obtained, in a per se known and conventional manner, by means of cold plastic deformation of the surface of the cylindrical body to be formed, by compressing the latter between multiple forming rollers peripherally placed with respect to the cylindrical body itself.
More in detail, the rolling machine 1 is provided with a support structure 2 intended to be abutted against the ground, mechanically associated with two or more forming rollers 6, which, as described in detail hereinbelow, act with their thread against the peripheral surface of the body to be formed, being driven to machine by rotating substantially parallel to each other in a common rotation sense, in compression against the surface of the cylindrical body to be formed.
Preferably the support structure 2 is obtained by means of a metal framework, closed with paneling which confer a box-like appearance thereto. In such support structure 2, a longitudinal extension can be identified that is parallel to a central work axis A at which the cylindrical body to be formed can be coaxially arranged. Hence, hereinbelow such work axis A must be considered common to the machine and to the cylindrical body.
In accordance with the embodiment of the enclosed figures, the support structure 2 is longitudinally extended between a front wall 3 and a rear wall 4, each provided with a central opening 5, e.g. of circular form.
The central work axis A is arranged orthogonal to the walls 3, 4, and passes through the center of the aforesaid openings 5, which are then traversed by the cylindrical body to be processed.
Each forming roller 6 is constituted by a cylindrical body, preferably made of steel, provided with a central symmetry axis which corresponds with its rotation axis Z, and is provided with a thread 8 formed by at least one thread.
With the term thread, it must be intended hereinbelow a single rib in relief with spiral form, arranged on the external surface of each forming roller 6. The thread 8 of each forming roller 6 can be constituted by a single thread or by multiple side-by-side and parallel threads. With thread 8, it will thus be intended the set of threads (one or more than one) which are extended on the external lateral surface of the forming rollers 6. Only for the sake of description simplicity, hereinbelow the thread 8 composed of a single thread will be considered, so that such terms coincide with the reference number "8"; nevertheless, of course, the thread can be composed of multiple threads without departing from the protective scope of the present patent.
Each thread 8 is extended without interruption with a spiral form, which is extended by winding on the external surface of the forming roller 6, advancing along its longitudinal extension and rotation axis Z.
Each thread 8 can be substantially considered obtained in a longitudinal reading direction parallel to its axis Z, by a succession of profiles 12 which of course are circumferentially joined without interruption in the spiral extension of the thread.
The thread 8 has transverse section with respect to its spiral extension, with roughly triangular or trapezoidal shape with external crests 9 tapered with respect to an enlarged base. At the crests 9, the radius of the forming roller 6 is maximum, while at the bottoms 10 that are alternated with the crests 9, the radius of the forming rollers 6 is minimum.
The crests 9 and the bottoms 10 are connected by tilted sides 11. The pitch P of the thread 8 remains defined by the axial distance between two successive crests 9 while the radial distance between the crests 9 and the bottoms 10 defines the depth L of the thread 9.
The thread 8 is therefore extended on the external peripheral surface of the roller 6 and around the rotation axis Z with a helical extension and with shape and pitch characteristics that vary in accordance with the application needs of the cylindrical body to be formed.
In accordance with the embodiment illustrated in the enclosed figures, the machine 1 provides for three forming rollers 6, placed at 120 degrees from each other, which are adapted to plastically deform under cold conditions the cylindrical body to be formed.
Such body is placed along the central work axis A of the machine and is supported in such position by a suitable support structure (not illustrated), for example constituted by a plate with V-shaped concavity directed upward and fixed to the support structure of the machine 1.
The machine 1 also comprises two or more actuator means 15 mounted on the support structure 2, each mechanically connected to a corresponding forming roller 6 in order to move it along a respective first transverse axis R substantially perpendicular to the work axis A.
Due to such actuator means 15, the forming rollers 6 are capable of translating along the first transverse axes R, close to and away from the central work axis A and consequently with respect to the cylindrical body to be formed.
The forming rollers 6 are positioned around the central work axis A with their extension axes Z preferably parallel to the central work axis A and at an adjustable radial distance due to the actuation of the actuator means 15.
Motor means 16 arranged on the support structure 2 are further provided; these are mechanically connected to the forming rollers 6 in order to drive them in rotation in abutment against the cylindrical body to be formed, so as to impart a cold plastic deformation on the external surface thereof.
For such purpose, the forming rollers 6 have a seat, e.g. a through hole made along the longitudinal extension axis Z thereof, in which a tool holder shaft 14 is inserted in coupling relationship, connected by means of a transmission to the motor means 16.
The latter are for example obtained with electric motors 160 in particular of brushless type, each associated with a corresponding forming roller 6, and provided with drive shaft connected to the tool holder shaft by means of a universal joint transmission.
The motor means 16, and in particular the brushless motors, are capable of precisely controlling the rotation speed of the shafts thereof and their angular position (and hence of the forming roller which they drive in rotation) with respect to an angular reference position.
The universal joints interposed between the drive shafts and the tool holder shafts 14 allow the transmission of the rotation without the necessary condition of alignment of the drive shafts with the axes of the forming rollers 6, which can therefore allow rotating at different distances from the central work axis A, and they can also have a tilt with respect to the rotation axes of the drive shafts.
The combination of the transverse compression action due to the actuator means 15 which compress the forming rollers 6 on the cylindrical body to be formed, and of the rotation motion of the forming rollers 6 around the rotation axis Z due to the motor means 16, allows plastically deforming the cylindrical body placed along the central work axis A, obtaining progressive impressions on its peripheral external surface until the desired thread is obtained.
Advantageously, in accordance with the embodiment of the machine 1 illustrated in the enclosed figures, three forming rollers 6 are provided that are arranged at 120° from each other with respect to the work axis A in a manner such to equally distribute the stresses on the cylindrical body to be formed.
In addition, in accordance with such embodiment illustrated in the enclosed figures, the actuator means 15 are obtained with hydraulic actuators of linear type, oriented with the movement axis aligned with the first transverse movement axis R of the corresponding forming roller 6 and passing through the work axis A.
Each actuator 15 is provided with a hollow cylindrical body 18 fixed to the front wall 3 of the support structure 2 of the machine 1 by means of a support case 19.
Within the cylinder 18, a piston 20 is slidably mounted along the first transverse axis R; such piston 20 is provided with a movable head 21, which mechanically supports a corresponding forming roller 6.
The actuator 15 is connected to a hydraulic plant of pressurized oil capable of moving the piston 20 and the roller supported thereby along such first transverse axis R, and for placing the forming roller 6 under pressure with an adjustable force against the external surface of the cylindrical body to be formed.
Advantageously the mechanical connection between the forming rollers 6 and the actuator means 15 occurs by means of brackets 27, which are mechanically fixed to the movable heads 21 of the pistons 20 by means of bolts and comprise two lateral perforated wings 28 in which support bearings of the forming rollers 6 are housed.
The rotation axes Z of the tool holder shafts 14 (or tool holder mandrels) are susceptible of being tilt-adjusted, in a known manner, with respect to the central work axis A, even if in an initial approximation they can be considered substantially parallel to the work axis A itself of the cylindrical body to be processed.
According to the idea underlying the present invention, sensor means 30 are provided which are mechanically associated with the support structure 2 and movable between at least one non-operative position P1, in which they are in distal position with respect to the forming rollers 6, and at least one operative position P2, in which they are in proximity to at least one forming roller 6, in order to detect the axial position (i.e. the axial coordinate) of the at least one thread 8 thereof.
The axial position of the thread is detected with respect to the axial reference position of the sensor means 30. More in detail, therefore, such position can be determined in relative terms with respect to the sensor means or in absolute terms, e.g. with respect to references on the machine.
The machine 1 also comprises movement means 35 mounted on the support structure 2 and mechanically connected to the sensor means 30, in order to move them between the aforesaid non-operative position P1 and the aforesaid operative position P2 along a second transverse axis R' perpendicular to the work axis A.
Preferably, the sensor means 30 comprise a feeler device 31 mechanically connected to the movement means 35 and susceptible of producing an electrical signal.
The feeler device 31 is mechanically connected to a discoid element 32, e.g. made of metal with the circumferential edge tapered, susceptible of being moved with respect to a position of equilibrium thereof once it comes into contact with the thread 8 of the forming roller 6. Following such movement, the disc 32 drives the feeler device 31, which produces the signal indicative of the contact with the thread 8 of the forming roller 6.
More in detail, the feeler device 31 comprises a stem 33 and a contact sensor 34 mounted on the stem 33.
In operation, the metal disc 32 has a thickness sized such to penetrate for at least 30% of the depth L of the thread 8 of the forming rollers 6 and advantageously up to 75% of the depth L.
Preferably, the feeler device 31 of the sensor means 30 has an operation of on/off type, i.e. it sends an electrical signal to a logic control unit (not illustrated) when the metal disc 32 comes in contact with the thread 8 of the forming roller 6.
More in detail, such contact causes a movement of the discoid element 32, which tilts the stem 33 with respect to its axis Y by moving it from the position of equilibrium and consequently actuating the contact sensor 34, which in turn sends a signal to the logic control unit indicative of the contact with the thread 8 of the forming roller 6.
The abovementioned movement means 35 are mounted on the front wall 3 of the support structure 2 and are extended along a second transverse axis R' perpendicular to the central work axis A. Advantageously, such second transverse axis R' passes through the central work axis A, intercepting it at a known axial reference position.
The machine 1 operates according to pre-established operative steps by means of a logic control unit electrically connected to the sensor means 30, to the actuator means 15, to the motor means 16 and to the movement means 35 and allows phasing the threads 8 of the forming rollers 6 once the position of the threads of the single forming rollers 6 is defined.
The control unit is in fact set to manage all the processing steps of the machine 1 and the phasing process of the forming rollers 6. For such purpose, the logic control unit receives signals from the sensor means 30 and instructions relative to the work or phasing operating modes from a program, e.g. in standardized ISO language, and consequently controls the movement means 35, the actuator means 15 and the motor means 16.
Advantageously, the movement means 35 comprise a linear actuator provided with a movable arm 37 which is extended substantially along the second transverse axis R' and which supports the sensor means 30 at one end.
The linear actuator is advantageously a pneumatic piston without stem, whose travel is preferably defined between two end positions corresponding to the abovementioned non-operative position P1 and operative position P2 of the sensor means 30.
An end stop position of the piston is therefore fixed in a manner such that sensor means 30 are situated on the work axis A at their operative position P2. In this position, the axis of the feeler device 31, which is mechanically connected to the movable arm 37 of the movement means 35, coincides with the work axis A of the machine and symmetry axis of the cylindrical body to be processed.
The sensor means 30 in their operative position P2 are advantageously situated in centered position with respect to the forming rollers 6 arranged all around, which are for example three in number and positioned at 120 degrees from each other.
In accordance with the embodiment illustrated in the enclosed figures, the axial position of the sensor means 30 is taken as a reference along the axial coordinate of the central work axis A and is advantageously employed as relative reference for detecting the axial position of the threads 8 of the forming rollers 6.
Also forming an object of the present invention is a process for phasing the forming rollers 6 of a rolling machine 1, in particular of the abovementioned type; hereinbelow, the same reference numbers will be maintained for description simplicity.
The process according to the present invention provides for repeating the steps described up to now for each forming roller 6, necessary for attaining the pre-established objects.
The process first comprises a step for mutual positioning between the sensor means 30 and a first forming roller 6.
Advantageously the sensor means 30 are moved, which are carried by the movement means 35 to advance along the second transverse axis R' until reaching the operative position P2 on the central work axis A, centered with respect to the forming rollers 6.
Subsequently, the actuator means 15 are actuated and the corresponding forming roller 6 approaches the sensor means 30 by translating along the first transverse axis R. More in detail, the forming roller 6 is moved close to a measurement position M1 (while the other rollers remain in a retreated position M2) until the disc 32 of the sensor means 30 is at least partially inserted between a first and a second profile 12, adjacent to each other, of the thread 8 of the forming roller 6.
In such operative position P2, in which the disc 32 is preferably axially placed on the work axis A at the axial reference coordinate thereof, the radial distance between the rotation axis Z of the forming roller 6 and the circumferential edge of the disc 32 is less than the external radius of the thread 8 of the forming roller 6, in a manner such that the disc 32 is contained between two profiles 12.
The process subsequently provides for a first step for rotating the forming roller 6, which generates an axial movement of its threads 8, until a first profile 12 intercepts the sensor means 30 in the aforesaid axial reference coordinate of the disc 32.
The disc 32 transmits a movement to the contact sensor 34 that is determined by the interception of the first profile 12 of the thread 8, which consequently sends an electrical signal to the logic control unit indicating the effective contact between the thread of the forming rollers 6 and the metal disc 32.
In this manner, the logic control unit acquires a first axial position of the profile 12 of the thread 8 of the first of the forming rollers 6, at a specific angular position of the first profile 12 of the forming roller 6.
At this point, the first forming roller 6 can be brought back to a retreated position M2 by actuating the actuator means 15; at such position, it is spaced from the metal disc 32 and allows a second forming roller 6 to be brought into contact according to the above-indicated steps.
The aforesaid steps are then repeated for each forming roller 6 such that at the end thereof the logic control unit is capable of recognizing the position of the thread 8 of each forming roller 6 and hence also their mutual position.
Consequently, a step is provided for phasing the forming rollers 6, which are actuated by the control unit to carry out rotations starting from the axial coordinates detected by their first profile 12 as mentioned above. The mutual phasing positioning of the forming rollers 6 obtained with the aforesaid rotations will also account for the size of the cylindrical body to be formed, given that by varying the path completed by the impression impressed by a forming roller 6 on the body to be processed, in accordance with the size of the body itself, the position at which such impression must be followed by the thread of the subsequent forming roller 6 will vary.
Preferably, the process provides for, after the first step for rotating the forming roller 6, also a second step for rotating in opposite sense with respect to the first rotation and until the second profile 12 adjacent to the first intercepts the sensor means 30 at the axial reference coordinates thereof, thus acquiring a first axial position also of the second profile 12 in a corresponding angular position of the forming roller 6.
The logic control unit then defines, in a subsequent calculation step, a first intermediate position between the two profiles 12 of the thread 8, and controls the rotation of the forming roller 6 so that the sensor means 30 are arranged at such defined intermediate position.
At this point, there is a subsequent step for accurate positioning, in which the sensor means 30 are inserted between the first and the second profile 12 at a depth L of at least 30% of the height of the thread 8 at the first intermediate position and preferably at about 75%.
A third step then follows for rotating the forming roller 6 until a profile 12 of the two adjacent profiles 12 of the thread 8 once again intercepts the sensor means 30 at the axial reference coordinate thereof.
The disc 32 then actuates the contact sensor 31 following the interception against it of one of the two profiles 12 of the thread 8 of the forming roller 6, sending an electrical signal to the logic control unit for the acquisition of the axial position of the profile 12, in this case particularly accurate.
By means of a third step for rotating in the same sense as the first, the logic control unit acquires a second axial position of the first profile 12. In a subsequent fourth rotation of the forming roller 6, in opposite sense with respect to the third rotation, the second profile 12 once again intercepts the sensor means 30 at the axial reference coordinate, and the control unit consequently acquires a second axial position of the second profile 12 at a detectable angular position of the forming roller 6. The angular positions of the forming roller 6 are in fact detectable due to the actuation electronics of the motor means 16 which drive them in rotation.
The advantage in performing the aforesaid steps in which the metal disc 32 is situated at a depth of at least 30% of the thread 8 lies in being able to acquire the axial positions of the two profiles 12 in an increasingly accurate manner, and calculate a second intermediate position that is more precise than the first intermediate position, with errors under one degree. Indeed, unlike the detections carried out in proximity to the crests 9 of the profiles 12 of the thread 8, less precise due to the irregularities of the same crests 9, the detections on the sides 11 of the profiles 12 are more accurate since the sides 11 of the profiles 12 ensure the interception of the metal disc 32 at a single point.
The aforesaid steps are repeated for each forming roller 6 and, for such purpose, the forming roller 6 on which the measurements have already been completed is moved away from the sensor means 30 by making it translate along the relative transverse axis R to the retracted position M2, due to the actuation of the corresponding actuator means 15, such that a second forming roller 6 can approach the sensor means 30 until reaching its measurement position M1 in order to once again execute the abovementioned steps aimed to identify the position of the thread 8 thereof.
Advantageously, after having acquired the positions of the threads of the single forming rollers 6, and advantageously having acquired the second intermediate positions for the threads 8 of each forming roller 6, and also having moved the sensor means 30 along the transverse axis R', moving them into the non-operative position P1, the aforesaid step for phasing the forming rollers 6 takes place by means of their mutual angular positioning.
In controlling the rotations of the single forming rollers 6 for the phasing thereof, the logic control unit considers at least the mutual arrangement thereof, e.g. at 120° in case of three symmetric forming rollers, the diameter of the forming rollers 6, the diameter of the cylindrical body to be processed, and the pitch of the thread 8.
Such phasing process only requires a few minutes to be completed and ensures high precision in the mutual positioning of the forming rollers 6; therefore, the invention thus conceived attains the pre-established objects.
Of course, in the practical attainment thereof, the invention can assume forms and configurations that are also different from that described above, without departing from the present protective scope.

Claims

Rolling machine for forming a thread on cylindrical bodies, which comprises:
- a support structure (2);

- two or more forming rollers (6), mechanically associated with said support structure (2), each of which driven to rotate around its rotation axis (Z) and provided with a thread (8) having at least one thread extended around said rotation axis (Z), said forming rollers (6) being susceptible of plastically deforming a cylindrical body available along a central work axis (A) of said machine (1);

- two or more actuator means (15) mounted on said support structure (2), each mechanically connected to a corresponding said forming roller (6) in order to move it along a respective first transverse axis (R) perpendicular to said work axis (A);

- motor means (16) arranged on said support structure (2), mechanically connected to said forming rollers (6) and adapted to drive in rotation said forming rollers (6) on said cylindrical body in order to plastically deform it;
characterized in that it also comprises:
- sensor means (30) mechanically mounted on said support structure (2) and movable between at least one non-operative position (P1), in which they are in distal position with respect to said forming rollers (6), and at least one operative position (P2), in which they are susceptible to be placed in proximity to at least one said forming roller (6), and detect the axial coordinate of the at least one thread of said forming roller (6);

- movement means (35) mounted on said support structure (2) and mechanically connected to said sensor means (30), in order to move them between said non-operative position (P1) and said operative position (P2), along a second transverse axis (R') perpendicular to said work axis (A).
Rolling machine according to claim 1, characterized in that said sensor means (30) comprise:
- a feeler device (31) mechanically connected to said movement means (35) and susceptible of producing an electrical signal;

- a disc (32) mechanically connected to said feeler device (31) and susceptible of being moved in contact with said thread (8) in order to drive said feeler device (31).
Machine according to claim 1, characterized in that it comprises a logic control unit electrically connected to said sensor means (30), to said actuator means (15), to said motor means (16) and to said movement means (35) in order to phase the threads (8) of said forming rollers (6).
Machine according to claim 1, characterized in that said movement means (35) comprise a linear actuator provided with a movable arm (37) which is extended substantially along said second transverse axis (R') and which supports said sensor means (30).
Machine according to claim 4, characterized in that said linear actuator is a pneumatic piston without stem, whose travel is defined between two end positions corresponding with the non-operative (P1) and operative (P2) positions of said sensor means (30).
Machine according to claim 1, characterized in that there are three said two or more forming rollers (6) and they are angularly positioned at 120° from each other.
Machine according to claim 1, characterized in that said second transverse axis (R') intercepts said work axis (A).
Process for phasing the forming rollers of a rolling machine according to claim 1, which provides for the following steps to be repeated for each forming roller (6):
- a step for positioning said sensor means (30) with respect to one of said forming rollers (6), in which said sensor means (30) are inserted between a first profile (12) and a second profile (12) adjacent to the first of said at least one thread (8) of said forming roller (6);

- at least one first step for rotating said forming roller (6) with consequent axial movement of said at least one thread (8), until said first profile (12) intercepts said sensor means (30) at an axial reference coordinate thereof.
Process for phasing the forming rollers of a rolling machine according to claims 3 and 8, characterized in that it comprises a step for phasing said forming rollers (6) by means of their rotations commanded by said logic control unit starting from the axial coordinates of said at least one first thread (8) of each said forming roller (6).
Process for phasing the forming rollers of a rolling machine according to claim 9, characterized in that it also comprises:
- a second rotation of said forming roller (6) in an opposite sense with respect to said first rotation, until the second profile (12) of the thread (8) of said forming roller (6) is brought to intercept said sensor means (30) at the axial reference coordinate thereof,

- a calculation step in which said logic control unit defines at least one first intermediate position between said profiles (12), and controls the rotation of said forming roller (6) so that said sensor means (30) are arranged at said intermediate position,

- a subsequent step of accurate positioning, in which said sensor means (30) are inserted between said first and said second profile (12) at a depth of at least 30% of the height (L) of the thread (8) at said first intermediate position;

- at least one third step for rotating said forming roller (6) until said at least one profile (12) intercepts said sensor means (30) at said axial reference coordinate.
Process for phasing the forming rollers of a rolling machine according to claims 2 and 8, characterized in that said disc (32) drives said feeler device (31) following the abutment against said at least one profile (12) of said at least one thread (8) of said forming roller (6), sending an electrical signal to said logic control unit for the acquisition of the axial position of said profile (8).