GB2153034A

GB2153034A - Nut manufacture

Info

Publication number: GB2153034A
Application number: GB08500943A
Authority: GB
Inventors: Andrea Bazzurro
Original assignee: BARGE BULLONERIA; BULLONERIA BARGE SpA
Current assignee: BARGE BULLONERIA; BULLONERIA BARGE SpA
Priority date: 1984-01-20
Filing date: 1985-01-15
Publication date: 1985-08-14
Also published as: SE8500247D0; IT8467059A0; FR2558545A1; FR2558545B1; GB8500943D0; BE901514A; DE3501566A1; SE8500247L; DE3501566C2; GB2153034B; NL8500107A; IT1178832B

Abstract

A method for manufacturing a nut adapted to remove any paint layer covering a threaded shank as it is screwed onto this shank includes the pressing of a series of equiangularly-spaced radial recesses (9) on the inner surface of the nut before this inner surface is tapped. The recesses (9) extend axially from the end of the nut which feeds onto the threaded shank, and have a radial depth at least equal to the radial dimension of the thread of the nut. <IMAGE>

Description

SPECIFICATION Nut manufacture This invention relates to the manufacture of nuts.

in mechanical industries generally, and in particular in the automobile industry, in the earth moving equipment industry and the railway and tramway locomotion industries, it is common to form the bodywork by assembling prefabricated components.

In many cases the preparation of components for final assembly is effected by the welding to the various components of threaded studs for use in interconnecting the components. In particular use is made more and more frequently of studs in the form of screws with heads provided with bosses or beads for the welding of the heads to a support member on the component in question. Before these threaded studs are used, that is, before the assembly, the various components, after their fabrication and working has been completed, are sent to a painting station.

In order to prevent the threaded shanks of the studs, for example, the said screws mentioned above, becoming covered with paint, which would make the subsequent screwing of the nut difficult, the threaded shanks are usually protected by being masked with a plastics or rubber hood or by wrapping with adhesive tape. This preventive operation involves considerable expense including the cost of the hood or tape used for masking the threads, these being only partly recoverable, the cost of the time needed for the masking operation, and the cost of the time needed to remove the masking after painting. This latter operation is longer and more difficult than the preceding one because of the presence of dried paint on the workpieces and on the masking.

The object of the present invention is to provide a nut, and a method of manufacturing a nut, which is able to remove any paint layer covering a threaded shank before the but is screwed onto this threaded shank.

The method according to the present invention is characterised mainly in that, before the tapping of the inner surface, there are formed by pressing on the inner surface a series of equiangularly spaced radial recesses extending axially from the end of the nut which feeds onto the threaded shank, the recesses having a radial depth at least equal to the radial dimension of the thread of the nut.

By virtue of this characteristic, a nut is obtained simply and economically with cutting edges capable of removing the paint from the threaded shank during the screwing of the nut onto the threaded shank.

A further object of the present invention is a nut made by the method mentioned above.

In use of the nut according to the invention, it is not necessary to mask the threads of the screw-threaded shanks before painting, since the nut is able to scrape excess paint deposits from the thread during screwing. A certain thickness of paint will remain by virtue of the screw-nut clearance, and this will act as a means for resisting unscrewing of the nut.

Further characteristics and advantages of the present invention will become apparent from the description which follows, with reference to the appended drawings, provided purely by way of non-limiting example, in which: Figures 1 to 5 illustrate five successive steps in the method of manufacture of a nut according to the present invention, Figure 6 is a side view of a punch used in the method illustrated in Fig. 4, Figure 7 is an end view of the punch of Fig.

6, Figures 8 to 10 illustrate three variants of Fig. 7, Figure ii is a plan view of a nut according to the present invention, Figure 12 is a section taken on the line XII Xill of Fig. 11, and Figure 13 is a variant of Fig. 1 2.

As will be clear from the following description, the manufacturing method according to the present invention may be achieved with the use of conventional pressing machines with four or five cutting dies and the usual automatic tapping machines currently used for the manufacture of ordinary standardised nuts.

With reference to the drawings, the method provides first of all for the cutting of an off-cut 1 from a bar, the off-cut subsequently being located at a first, preforming station for the radiussing of one face 2 and the smoothing of the opposite face 3 by a conventional method.

The element thus formed is taken to a second station for preforming in a dye of hexagonal, square or any other desired shape for forming the end face profiles 4 (see Fig. 2) and the corners of the side faces of the nut so as to obtain the element indicated 5 in Fig. 2.

In a known method the operation described above for making the element 5 may be carried out at three stations. The element 5 is then brought to a third station for preforming in a hexagonal, square or other shaped die for forming the profiles 6 (see Fig. 3) for receiving the punch for pressing and extrusion which is carried out during the fourth operation described below. The bearing planes of the nut are then practically 100 per cent finished.

The element thus obtained (indicated 7 in Fig. 3) is brought to a fourth station where a special punch (indicated 8 in Fig. 6) forms a circular impression in the element 7 with a diameter d1 substantially equal to the diameter d of the hole which is formed in the piece in the subsequent punching operation (illustrated in Fig. 5).

The punch 8 is shaped so as to form three or more radial recesses 9 of width L (see Fig.

11) the bottom of which identifies a cylindrical surface having a radius E (see Fig. 12) and a corresponding diameter 2E which is equal to or greater than the outer diameter D of the threading. The sides 10 of the axial ribs 11 of the punch which form the recesses 9 may be inclined at any angle to the radial planes passing through the axis of the punch. Preferably the sides 10 of each rib 11 are parallel to a plane of symmetry of the rib passing through the axis of the punch.

Figs. 8 to 10 illustrate possible variants of the punch 8 which allow different shapes and different numbers of grooves to be made.

The element made at the end of the operation carried out at the fourth station, indicated by the reference numeral 12 in Fig. 4, is brought to a fifth station where a piercing punch forms a through-hole of diameter d passing through the nut. This operation results in the removal from the nut of a waste portion 1 3 in the form of a disc of thickness S.

An additional advantage of the method according to the invention lies in the fact that the particular combination of pressing and extrusion described above results in a waste piece of less than usual thickness S.

The method according to the invention may be carried out with the user of one of the usual pressing stations for carrying out the said upsetting and extrusion operation in combination with the pressing so as to reduce the working waste considerably and up to 50%.

The piece obtained at the end of the operation illustrated in Fig. 5 is finally subjected to a tapping operation so as to obtain a nut having a the following specific features: a) the nut has three or more recesses 9 of width L and depth h. The outer diameter 2E of the recesses is equal to or greater than the outer diameter D of the threading.

b) The bottom surfaces 1 3 (see Fig. 12) of the recesses 9 may be of any form and any inclination. Preferably they lie in planes parallel to the axis of the nut and inclined at an angle a (see Fig. 11) to radial planes passing through the axis of the nut.

c) The surfaces 1 3 of the recesses cut the threading of the nut entirely and beyond its depth thus creating teeth 14 the profiles whereof define a cutting thread which has the function of scraping excess paint off a threaded shank when the nut is screwed onto the shank.

d) The recesses 9 also have the function of collecting the excess paint scraped off by the cutting teeth 1 4 which does not leave the piece during the screwing of the nut.

e) The overall height H of the nut is such that the thread of the nut has a sufficient shear strength. Preferably the height H of the nut is equal to the nominal diameter D (see Fig. 12).

The nut according to the invention may be formed of any material and may be subjected to cleaning and hardening.

In order to facilitate the supply of the nut by means of automatic loaders it is convenient to form the nut with two different bearing planes. For example, the end of the nut opposite that provided with the recesses 9 may be conical as indicated at 1 5 in Fig. 1 3.

Claims

1. A method of manufacturing a nut adapted to remove, at least partially, any paint layer covering a threaded shank as the nut is screwed onto the shank, in which, before the tapping of the internal surface of the nut, a plurality of radial recesses are formed in said internal surface, extending axially from the end of the nut which feeds onto the threaded shank, the radial recesses having a radial depth at least equal to the radial depth of the thread of the nut.

2. A nut adapted to remove, at least partially, any paint layer covering a threaded shank as the nut is screwed onto the shank, in which the internal threaded surface of the nut is formed with a plurality of radial recesses extending axially from the end of the nut which feeds onto the threaded shank, the said recesses having a radial depth at least equal to the radial depth of the thread on said internal surface.

3. A nut according to Claim 2, in which the said recesses are equiangularly spaced.

4. A nut according to Claim 2 or Claim 3, made by the method defined in Claim 1.

5. A paint-removing nut substantially as herein described with reference to and as shown in Figs. 11 and 1 2*or Fig. 13 of the accompanying drawings.

6. Any novel feature or combination of features described herein.