Tool for making rivet or expansion nails

A tool for making a rivet or expansion nail, i.e. a nail that has at least at one end a laterally expandable portion and is made by cutting off and stamping a nail wire in a single working stroke, wherein the tool includes a guide for a nail wire for guiding the wire in a plane perpendicular to the wire, a cutter having edges disposed in V-fashion, a stamping mandrel arranged in the plane of symmetry of the cutting edges and positioned on the open side of and facing away from the converging point of the V-arrayed cutting edges, and resilient applicators which are pressed by the nail wire during a working stroke of the tool against the action of a spring and lift the nail from the cutter and stamping mandrel during a return stroke of the tool.

The present invention relates to a tool for making so-called rivet nails or 
expansion nails, i.e. a nail that has at least at one end a laterally 
expandible portion. The nail is made by cutting off and stamping a nail 
wire. 
Various tools have been designed for the manufacture of rivet nails but 
they have not proved able to attain the high speeds required for a 
rational production, i.e. at least about 200 nails per minute. This 
depends int. al. on the fact that the nails get stuck in the tool or are 
difficult to remove rapidly from the tool since that part of the tool 
which makes the expandible portion of the nail by stamping tends to retain 
the nail in the tool. 
Complicated and expensive tools, including a plurality of mobile 
components, have been built in order to solve this problem. However, these 
tools have not been able to attain the high production rate necessary for 
an econimical manufacture of rivet or expansion nails. 
The object of the present invention is to overcome the above-mentioned 
disadvantages and to produce a tool which can be run at a high production 
rate without functional disorder due to the fact that it will be very 
simple although it produces one completely finished expansion nail per 
working stroke. The manufacture also takes place without wastage of 
material, thus eliminating the problems of collecting and removing wastage 
as well as the costs entailed therewith. Thanks to the simplicity of the 
tool it will also become amazingly cheap. 
This object is realised by the tool according to the invention which 
effects cutting off the point of the nail and stamping the expandible 
portion of the nail during a single working stroke because the tool 
comprises a guide for the nail wire for guiding the wire in a plane 
perpendicular to the wire, a cutting-off means having cutting edges 
disposed in V-fashion, a stamping means arranged in the symmetry plane of 
said V-shaped cutting edge arrangement on the "open" side of the edges 
facing away from the point, and resilient applicators for the wire adapted 
to be pressed by the nail wire during the working stroke of the tool in a 
direction opposite to the working direction of the tool against the action 
of a spring and to lift the nail wire from the cutting-off means and 
stamping means during the return stroke of the tool. 
In a second embodiment of the invention the tool comprises two identical 
tool sections including each a nail wire guide, a cutting-off edge, a wire 
applicator and a stamping means which are arranged straight opposite each 
other on those surfaces or ends of the tool sections which face each other 
and are perpendicular to the direction of motion of the working stroke of 
the tool, said applicators being adapted during the working stroke to be 
brought to bear against each other around the nail wire and to be pressed 
downwards, against the action of a spring means, in the tool frame 
slidably supporting the applicator, and at the end of the working stroke 
the cutting-off edges and the stamping means are carried close to each 
other in order to effect cutting-off and stamping of the nail wire. 
In a third embodiment of the invention the stamping means consists of a 
mandrel having a stamping edge situated in the symmetry plane and 
generally parallel to the nail wire, top surfaces or top facets inclined 
obliquely downwardly-outwardly from the edge on either side of the 
symmetry plane, and side facets adjoining the top facets and arranged 
further away from the symmetry plane, said side facets having a smaller 
angle of inclination than have the top facets relative to the symmetry 
plane and extending down to the end surface of the tool body. 
In a fourth embodiment each top facet consists of a generally plane and 
triangular surface defined by lines between the end points of the stamping 
edge and a point situated on or immediately above the plane of the end 
surfaces and between the end points of the stamping edge, while in a fifth 
embodiment said point is situated on the end surface of the tool body 
half-way between the end points of the stamping edge. 
In a sixth embodiment the top facet, at that portion of it which is 
remotest from the stamping edge, is defined by a line situated in the end 
surface of the body, while in a seventh embodiment the side facets at the 
outer portions of the stamping mandrel are defined by front and back edges 
which extend between the front end point of the stamping edge and a front 
point situated on the end surface in the symmetry plane, and respectively 
between the back end point of the stamping edge and a back point situated 
on the end surface in the symmetry plane. 
In an eighth embodiment said front and back points are situated outside the 
respective end points of the stamping edge while in a ninth embodiment the 
top facet has, at that edge of it which is remotest from the stamping 
edge, a smaller angle of inclination than the angle of inclination of the 
facet at the stamping edge. 
In a tenth embodiment the top facet has a cam which rises above the top 
facet and extends generally perpendicular to the stamping edge. 
In a final embodiment the cutting-off edge has a generally triangular 
cross-section in order to give the nail a pyramid-shaped point.

In FIG. 1, 1 represents tool sections 3, 4 for cutting-off and stamping the 
end of an expansion nail and 2 is a tool for upsetting the end of the nail 
wire 5 so as to form a head. To this effect the nail wire is clamped by 
two laterally movable jaws 6 and 7 while a stamp or die 8, which is 
movable in the longitudinal direction of the nail wire, with a recess 9 
upsets the end of the nail wire 5 so as to form a round head. 
As the two tool sections 3 and 4 are identical only the lower section 3 is 
described below with reference to FIG. 2. From this figure it appears that 
the tool is symmetrical about a vertical plane through line 10. The 
uppermost surface 11 of the tool sections constitutes an abutment surface 
and a guide pin 13 and a guide hole 12 situated at the same distance from 
the symmetry plane. When the tool section 4 is placed on the top of the 
tool section 3 according to FIG. 1, the guide pin 13 of one tool section 
coacts with the guide hole 12 of the other tool section and vice versa. In 
this way the symmetry planes of the tool sections will coincide. 
During the manufacture the nail wire is carried through the tool in the 
symmetry plane. The wire is guided transversely of its longitudinal 
direction by a guide 14 in the form of a recess, adapted to half the 
cross-section of the wire, in an applicator plate 15 which is slidably 
guided by means of rules 16 in guiding means in the body 17 of the tool 
section 3. The applicator plate 15 has projecting abutments 18 which are 
pressed against the abutment edge 19 in the body 17 by a spring 20 in the 
form of a plate of elastomeric material. In this position the applicator 
plate 15 projects upwards a distance 21 above the abutment surface 11. The 
bottom of the guide 14, which carries the nail wire 5, lies in this 
position so high that the wire lies above both the stamping mandrel 30 and 
the cutting edge 50 which will be described in more detail below. 
The spring 20 lies inserted in a groove in the body 17 and is pressed in 
slightly between the edges 21 of the groove where it is retained. The 
spring is at its lower part supported by a support 22 which is attached to 
the body 17 by means of a screw. When the tool sections 3 and 4 are 
brought together the two applicator plates 15 will first come in contact 
with each other and the guides 14 grasp the nail wire 5. During the 
continued movement of the tool the applicator plates are displaced against 
the action of the spring plate 20 which can expand laterally in the recess 
23. The edges 24 of the recess are situated outside the points of the 
abutments 18 so that the applicator plate 15 can be introduced into the 
recess 23. 
Symmetrically arranged around the symmetry plane through the line 10 are a 
stamping mandrel 30 and a cutting-off edge 50. Prior to the working stroke 
the nail wire 5 is situated immediately above the mandrel 30 and the edge 
50. During the working stroke the edges 50 of the two tool sections are 
brought together so that they will lie quite close to each other or bear 
against each other at the end of the working stroke, while the nail wire 
is cut off and ends in a V-shaped point, a so-called chisel cut which, 
when the cutting edges are straight, takes the form of a wedge. It is 
advantageous to give the cutting-off edge 50 a triangular cross-section, 
as is shown in FIG. 7, where also the tool sections 3 and 4 appear as well 
as the nail wire 5. If the edges 50 are carried out in the mentioned 
manner the nail will have a pyramid-shaped point 51, which is advantageous 
within certain fields of use. This shape also contributes to making it 
easier for the cut-off nail to leave the tool at a high production rate. 
As indicated at the tool 2 in FIG. 1, the cut-off end of the nail wire has 
edges on its sides which have formed during the cutting-off of the point 
in the tool 1. As the jaws 6 and 7 grasp the nail wire very firmly it is 
possible to upset an end, cut off in the mentioned manner, so as to form a 
nail head. This means that during the production no wastage whatsoever 
will be obtained, which wastage would have to be carried away or might 
block the function of the tool. This contributes to a rapid and safe 
production. 
The stamping mandrel 30 has an upper edge 31 which extends in parallel with 
the line 10 and is situated in the symmetry plane of the tool. The height 
of the edge 31 above the end surface 25 of the tool section 3 is somewhat 
smaller than the height of the cutting edge 50 above the end surface 25. 
This means that the edges 31 of the tool sections 3, 4 are situated at a 
small distance from each other at the end of the working stroke. This, 
however, is sufficient to bend out and stamp the expandible portion of the 
nail and to make a slot in its centre so as not to prevent the expansion 
of the portion. This is shown in FIG. 8, which will be described in 
greater detail below. 
The stamping mandrel 30 is formed in a specific manner in order to 
facilitate detachment of the nail wire from the stamping mandrel 30 during 
the return stroke of the tool. Thus the mandrel has surfaces or facets of 
generally triangular shape arranged at angles to each other. The facets 
are preferably symmetrically arranged about the symmetry plane of the 
tool. For the sake of simplicity only that side of the stamping mandrel 30 
which is shown in FIG. 2 is described here. From the edge 31 a top facet 
32 extends outwardly-downwardly towards the end surface 25. The facet 32 
is defined by substantially straight lines between the end points 33 and 
34 of the edge 31 and between these points and a point 36 which is 
situated on the end surface 25 or slightly above this and preferably 
half-way between the end points 33 and 34 of the edge 31. 
From these points 33 and 34 a front edge 36 and a back edge 37 extend 
obliquely downwardly-outwardly in the symmetry plane to front and back 
points 38 and 39, respectively on the end surface 25. A front facet 40 is 
defined by substantially straight lines between the points 33, 35 and 38 
and a back facet is defined in the same way by lines between the points 
34, 35 and 39. 
The form of the stamping mandrel 30 can be modified. Thus, for instance, 
one or both the points 38 and 39 may lie straight below the points 33 and 
34, respectively. The point 35 may lie closer to the stamping edge 31 so 
that the facets 40 and 41 meet along a line of intersection with the end 
surface 25. 
The form of the stamping mandrel 30 is elucidated in FIGS. 3-6 which show 
sections of the mandrel 30 in planes III, IV, V and V (in a modified form 
of the mandrel). FIG. 3 shows the triangle-shaped section outside the end 
points 33 and 34 of the edge 31. FIG. 4 shows a section through a portion 
of the mandrel 30, which is defined by the top facet 32 and side facets 40 
or 41. It appears from the figure that the angle .alpha. of the top facet 
32 relative to the symmetry plane is greater than the angle .beta. of the 
side facets 40, 41 relative to the same plane. All the sections are 
perpendicular to the stamping edge 31. 
To permit pressing out the expandible portion 52 of the nail (see FIG. 2) 
somewhat more, the facets are provided with small cams 42 projecting 
slightly above the facet and extending substantially at right angles to 
the stamping edge 31, as appears from FIGS. 2, 6 and 8. 
FIG. 5 shows an alternative embodiment of the top facet. In this case the 
angle .alpha..sub.2 to the symmetry plane at the facet portion adjacent 
the edge 31 is greater than the angle .alpha..sub.1 at the facet portion 
adjacent the side facet 40, 41. This embodiment may be favourable in 
certain cases in order to detach the nail from the tool very rapidly. 
FIG. 7 shows a section through the cutting edges 50 when the tool sections 
3 and 4 are in the end position of the working stroke and have cut off the 
nail wire 5 so that the nail ends in a pyramid-shaped point. 
FIG. 8 shows a section through the stamping mandrels 30 when the tool 
sections 3 and 4 are in the end position of the working stroke and the 
nail wire 5 has been slit up to obtain the expandible portion 52 shown in 
FIG. 2. 
Some preferred embodiments have been shown and described above to exemplify 
the invention which, however, can be modified in accordance with other 
embodiments within the scope of the appended claims.