CA1053413A - Device for multistage forming of screws - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

The invention relates to a device for the multistage forming of screws which have a head of which at least one di-mension does not exceed, in the direction normal to the axis of the screw shank, the diameter of the shank. The device includes, a slide carrying punch and a turret head carrying dies. The slide carries a planishing press tool for the screw head, the tool being mounted adjustably and resiliently in the direction of pressing. In the turret head carrying dies is arranged a knock-out pin mounted positively slidably in two phases towards the slide. The planishing press tool of the screw head com-prises a supporting body adjustable by a wedge relative to the slide and carrying a punch mounted in a guiding plate adjust-able normally to the direction of pressing. The supporting body including a movable system resiliently supporting the punch.

Description

lQ534:~3 The invention relates to the manufacture of screws with finished heads, i.e. without flashes, by multistage forming and particularly to a device adapted for the manufacture of screws having a head of the kind, where at least one dimension does not substantially exceed in the direction normal to the axis of the screw shank the diameter thereof. Such screws are used, for example, for railway purposes.
Screws having a head exceeding in all dimensions the diameter of the shank may be formed without flashes by providing the die with a projecting portion, the contour of which equals the contour of the screw head, A cavity is also formed in the punch, the contour of which likewise equals the contour of the head of the screw being pressed. The projecting portion of the die enters into the punch cavity during the pressing process and thereby closes the cavity and thus enables the forming of screws without flashes.
In cases where the size of the screw head in one or more directions does not substantially exceed the size of the shank, it is not possible to close the cavity in which the head is formed in the above described manner. It is therefore not possible to press screws of this kind without flashes in the commonly known devices, It has been already suggested to press such screws without flashes by forming the cavity corresponding to the shape of the screw head in the die and closing this cavity by the punch entering this cavity. The disadvantage of this procedure, however, is that the material being formed can not be prevented from penetrating into the gap between the two pressing tools, whereby an undesirable overflow on the screw head is produced.
This overflow reduces the utilization value OL the screw and must be removed under circumstances by a separato operation carried out additionally outside the pressing device.

lOS341;~
The present invention overcomes these disadvantages by providing, in a device for multistage forming of screws, a slide which carries a head planishing tool, said tool beiny mounted adjustably and resiliently in the direction of pressing and a knock-out pin arranged in the die head and mounted posi-tively slidably in two phases in the direction towards the slide.
According to a further feature of the invention the head planishing tool comprises a support body which is adjust-able by means of a wedge with respect to the slide. The sup-port body carries a punch mounted in a guiding plate which is adjustable normally to the direction of pressing. A movable system resiliently supports the punch and is arranged in said supporting body.
The invention will now be described with reference to the accompanying drawings which show a preferred form thereof and wh rein:
Fig. 1 is a sectional view through the pressing tool in elevation, and Fig. 2 is a front view of the pressing tool.
Referring to the drawings, the slide 1 is movable along the axis x ~figure 2) which is the axis of rotation of a turret head 2 which carries the dies. The slide is disposed in a groove of a support body 3 of the pressing tool, the rear portion of said support body 3 bearing against a wedge 4 and being slidably mounted in the slide 1. The support body 3 is secured in the slide 1 by screws 5.
A bushing 7 is inserted in the support body 3 and a guiding sleeve 8 is arranged in a recess of the bushing. The guiding sleeve 8 is fixed in the bushing 7 by a screw 9. On th~ support body 3 at the side facing the turret head 2, a guide 105~13 plate 10 is fi~ed by screws 11 passing through the corresponding openings in the guide plate 10 with some clearance. The above described elements constitute, within the press tool, a system which during the pressing process is immovable relative to the slide 1.
A pin 12 is slidably mounted in a cavity in the guiding sleeve 8, and between the head and shoulder of pin 12 are fitted Belleville springs 13. On the outer surface of the guiding sleeve 8 an outer sleeve 14 is slidably mounted, said outer sleeve being provided at one end with an inner collar 6. Between the inner collar 6 and the shoulder of the guiding sleeve 8 is inserted a plastic ring to dampen the impact of the outer sleeve 14 on the guiding sleeve 8. The other end of the outer sleeve 14 is provided with an outer thread on which is threaded a cap nut 15, and with an inner thread in which a screw 16 is screwed in such a way that the outer sleeve 14 is mounted on the guiding sleeve 8 without any axial clearance and is loaded by said Belleville springs 13.
In the guide plate 10 is mounted the punch 17 proper.
The punch is slidable in the axial direction and immovable in the radial direction and bears against a rest 18, the elements being blocked against rotation by a pin and key. A small amount of clearance remains between the rest 18 and the cap nut 15.
In the turret head 2 is mounted the die 19 in which is placed the finished screw bearing against the knock-out pin 20 guided in the rest 21.
The device according to the inven.:ion operates as follows.
When the slide 1 moves towards the turret head 2 the knock-out pin 20 pushes out the screw in front of the die 19 in such a way that the screw head projects over the face of the die by a portion of its height. The slide 1 acts through parts 1053~3 3, 7 and 8 by means of springs 13 on the parts 12, 14, 15, 16, 17 and 18 and in the forward dead center the punch 17 meets the projecting screw head, which it planishes. The slide 1 returns to the rear dead center and the screw after rotation of the turret head 2 is knocked out of the die 19.
The described device may be also used with multistage machines for ~orming other components than screws. The ma-chines may be either of the kind where the die carrying body rotates in respect to the slide ~ith punches, as it is the case with the above described embodiment, or of the kind where the slide and the die carrying body are immovable relative to each other and the component being formed is transferred between the individual tool pairs,

Claims (4)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. In a punch and die system for deforming a screw blank into a finished product, a die unit aligned along a first axis and having an upper screw blank-receiving cavity, a punch hous-ing coaxially supportable relative to the die unit, means for slidably mounting the punch housing for movement along the first axis downwardly toward the upper cavity of the die unit, a guide plate fixedly connected to a portion of the housing, a planishing tool supported for axial sliding movement within the guide plate at an adjustable position about the first axis, the tool adapted to engage a portion of a screw blank projecting out of the cav-ity of the die unit, and resilient means independent of the slidable mounting means for axially biasing the tool through the guide plate.

2. A system as defined in claim 1, in which the die unit further comprises a lower cavity disposed in coaxial abutting relation with and below the upper cavity and having a smaller cross-section, and in which the system further comprises, in combination, a knock-out pin slidably mounted in the second cavity for engagement with the lower end of a screw blank in the upper cavity, and means for reciprocating the pin within the second cavity.

3. A system as defined in claim 1, in which the biasing means comprises, in combination, a bushing supporting within the punch housing above the guide plate and having an aperture dis-posed in a lower end thereof, a pin slidably supported within the aperture of the bushing and having a head on a lower end thereof, a spring extending upwardly between the upper surface of the pin head and the bottom of the aperture in the bushing, and means for coupling the lower surface of the pin head to the rear surface of the tool.

4. A system as defined in claim 1, in which the system further comprises wedge means for adjusting the position of the punch housing relative to the slidable supporting means.