Roll for a radial thread-rolling head

Details Roll for a radial thread-rolling head Roll for a radial thread-rolling head

2000-02-22

2001-10-09

Larson, Lowell A. (Department: 3725)

Metal deforming

By use of tool acting during relative rotation between tool...

During rotation of work

C072S477000

Reexamination Certificate

active

06298703

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a roll for a radial thread-rolling head.
2. Description of the Related Art
In a radial thread-rolling head which has two or three rolls fitted with a thread-forming profile, such rolls are supported in a radially adjustable relationship. The thread-forming profile, as viewed in a circumferential direction, has a flattened area, a thread entry portion, a thread calibrating portion, and a thread exit portion. For reasons of forming and reasons of the torque to be applied by the machine, the aforementioned portions extend over a certain angle. Thus, the flattened area will usually extend over an angle of about 40°, the entry portion over an angle of 160°, the calibrating portion over an angle of 90°, and the exit portion over an angle of 70°. The length of the calibrating portion usually is such as to correspond to a multiple of the circumferential length of the work to be formed.
It is by means of such a radial thread-rolling head that a thread is formed into a work over a restricted length. The rolls, when in their initial position, have a rotational position such that the flattened areas face each other. In this position of the rolls, the work may be inserted in the thread-rolling head. The rolls which are released by hand or automatically by the machine tool are automatically advanced radially towards the work so that the work, while being rotated by the machine tool, is capable of carrying the forming rolls along. The rolling operation will be completed after a single rotation of thread-forming rolls.
The thread-forming rolls are rotated by frictional engagement between the work and thread-forming rolls, and a spring mechanism is tensioned, and a clutch will be locked in place upon completion of the rolling operation so that the thread-forming rolls will release the work again.
Such a thread-rolling head or the forming rolls for such thread-rolling heads are known, for example, from DE 39 30 131 C1 or the Fette company publication “Rollsysteme”.
Fortunately, rolls are of a certain axial length. This cannot be changed any more for a given version of a rolling head. On the other hand, what occurs in a number of applications is that the thread-forming roll is only utilized over a restricted axial area. This area will wear with time whereas the rest of the area remains usable, but is not used because of its position.
Therefore, it is an object of the invention to create a forming roller for a radial thread-rolling head, which is particularly useful in efficiently forming short threaded portions, but permits to be utilized completely.
SUMMARY OF THE INVENTION
In the inventive roll, an annular, continuous groove portion is formed in the longitudinal half of the roll in a radial plane on the circumference. This groove portion does not extend into the flattened area or it is unnecessary to pass it into this area. Formed in the two sides of the groove portion is a thread-forming profile each the pitches of which are opposed, the flattened areas of the thread-forming profiles being directed towards each other. In other words, if one thread-forming profile has been designed for a right-hand thread the other thread-forming profile will be suited for a right-hand thread as well when the roll is turned through 180° in the rolling head. It is possible to form identical threads using identical thread-forming profile portions in the work. However, it is also possible to use different thread-forming profiles such as those having different pitches, but also of different diameters. In addition, the elevation rate of thread-forming profiles may differ. The elevation rate is to be understood as the beginning of the entry portion which is radially displaced inwardly from the profile height in the calibrating portion, the thread-forming portion proper.
The groove portion ensures that the work does not get in engagement with the second thread-forming profile portion while the thread is being produced. Hence, according to a further aspect of the invention, the width of the nut at least corresponds to the pitch of the thread-forming profile plus a certain amount for overrun. Also, the groove is preferably intended to exhibit a minimum depth which is equal to the height of the profile plus a minimum elevation rate for entry.


REFERENCES:
patent: 516764 (1894-03-01), Fairbairn et al.
patent: 23 35 651 (1975-05-01), None
patent: 39 30 131 (1991-03-01), None
patent: 1-215425 (1989-08-01), None

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