Expansion fastener

The utility of an expansion fastener including an externally threaded shaft having a head shaped so as to be capable of being engaged by a manipulative tool, a generally cylindrical longitudinally split sleeve located around the shaft, a nut threaded on the shaft, the sleeve and the nut including coacting surfaces capable of expanding the sleeve as the nut is moved on the shaft can be improved by utilizing coacting structures on the end of the sleeve remote from the head and on the nut for preventing relative rotation between the sleeve and the nut as the shaft is turned. Preferably the sleeve is twisted slightly in a spiral-like manner so that an end of the sleeve serves as one of the coacting structures which engages an adjacent ridged or other not smooth surface of the nut serving as the other coacting structure. An edge or an irregular surface of both at the other end of the sleeve can effectively be utilized to hold the sleeve against rotation relative to a panel or similar member as the shaft is turned relative to the nut.

BACKGROUND OF THE INVENTION 
The invention set forth in this specification pertains to new and improved 
expansion fasteners. More specifically the invention set forth in this 
specification pertains to an expansion fastener each of which is adapted 
to be supported within a hole in a first member in such a manner so as to 
be capable of being inserted into a hole in a second member and which is 
adapted to be manipulated when a part of it is within the hole in the 
second member so as to be expanded into engagement with the interior of 
the hole in the second member. Expansion fasteners of this category may be 
utilized with a wide variety of different applications. They are primarily 
utilized in various different locations where that it is only possible to 
gain access to the hole in the second member from one side or surface of 
the second member. 
It is possible to construct expansion fasteners capable of being utilized 
in the manner indicated in the preceding paragraph in a number of 
different ways. It is considered that it has been most advantageous to 
construct expansion fasteners capable of being utilized as discussed in 
the preceding in the manner indicated in the Pitzer U.S. Pat. No. 
3,373,648, issued Mar. 19, 1968 entitled "Fasteners with Expansion 
Sleeve". Fasteners of the type referred to in this discussion and in this 
patent have normally been constructed so as to utilize an externally 
threaded shaft provided with a head capable of being engaged with a 
manipulative tool so as to turn the shaft, a generally cylindrical, 
longitudinally split sleeve located around the shaft and a nut threaded on 
the shaft. In such a structure the sleeve and the nut include coacting 
conical surfaces serving to expand the sleeve as the nut is moved on the 
shaft towards the head. Because of their functions these surfaces can be 
referred to as expansion surfaces. 
Fasteners of this type are normally constructed so that the shaft is 
capable of fitting through a hole in a first member but so that neither 
the head on the shaft nor the sleeve is capable of passing through this 
hole. A fastener of the type described herein is normally assembled on 
such a first member with the head and the sleeve on opposites sides of the 
first member so that both the sleeve and the nut extend outwardly around 
the shaft from one side of the first member. In this type of fastener 
normally both the nut and the unexpanded sleeve are dimensioned so as to 
be capable of fitting through a hole in a second member as previously 
indicated. Further these parts are dimensioned so that only a 
comparatively limited amount of rotation of the threaded shaft is 
necessary in order to expand the exterior of the sleeve into contact with 
the interior of the hole in the second member. 
One of the major problems encountered with prior expansion fasteners of the 
type discussed in the preceding concerns the fact that dimensions of the 
parts with the sleeve in an unexpanded configuration should be such that 
there will be no relative rotation between the sleeve and the hole in the 
second member. When such relative rotation occurs the fastener will not 
expand as it is used but will rotate freely as the head of the shaft is 
turned. This, of course, is undesirable. In order to insure adequate 
friction to insure expansion it has been very important to dimension the 
parts so that there is a degree of contact between them sufficient to 
inhibit such relative rotation. This, of course, is somewhat expensive 
and, hence, undesirable. 
BRIEF SUMMARY OF THE INVENTION 
From the preceding it is believed that it will be apparent that there is a 
need for new and improved expansion fasteners of the type previously 
identified. The invention is intended to fulfill this need. The invention 
is intended to provide fasteners of the type indicated which are not apt 
to rotate freely instead of expanding during normal conditions of its use. 
A closely related objective of the invention is to provide fasteners as 
indicated which are constructed in such a manner that rotation of the 
threaded shaft in the fastener will always result in expansion of the 
fastener under normal conditions of use. The invention is further intended 
to provide expansion fasteners as noted which can be conveniently and 
easily manufactured at a comparatively nominal cost and which are capable 
of giving prolonged, reliable, satisfactory service. 
The various objectives of this invention are achieved by providing: An 
expansion fastener which is adapted to be supported within a hole in a 
first member in such a manner as to extend from said first member and to 
be inserted into a hole in a second member and manipulated so as to be 
expanded into engagement with the interior of said hole in said second 
member, said fastener including, an externally threaded shaft, a head 
shaped so as to be capable of being engaged by a manipulative tool located 
at one end of said shaft, a longitudinally generally split, cylindrical 
sleeve located around said shaft, a nut threaded on said shaft, said 
sleeve and said nut including coacting expansion surfaces serving to 
expand said sleeve as said nut is moved on said shaft towards said head in 
which the improvement comprises: a holding means for preventing rotation 
of said sleeve by engagement with said first member when said fastener is 
located so that said shaft extends through said hole in said first member 
with said head on one side of said first member and said sleeve on the 
other side of said first member, said holding means being located on the 
end of said sleeve closest adjacent to said head so as to be capable of 
being drawn into engagement with said first member, coacting rotation 
preventing means, one of said coacting rotation preventing means being 
located on the end of said sleeve remote from said head, the other of said 
coacting rotation preventing means being located on said nut adjacent to 
said sleeve, said coacting rotation preventing means serving to prevent 
relative rotation between said sleeve and said nut when said sleeve and 
said nut are in contact with one another.

DETAILED DESCRIPTION 
In the drawing there is shown an expansion fastener 10 in accordance with 
this invention in which all of the parts are formed of a metal such as 
steel. This fastener 10 includes an externally threaded shaft 12 carrying 
an enlarged conventional head 14 which is adapted to be engaged by a 
manipulative tool such as, for example, a screw driver (not shown) when 
this shaft 12 is to be turned. If desired the shaft 12 and the head 14 may 
be referred to as a machine screw. It is considered preferable, however, 
to utilize the terminology employed in the preceding because it is 
conceivable that the fastener 10 of the present invention may be formed 
sufficiently large so as to not have the appearance of a conventional 
machine screw. 
This fastener 10 includes a nut 16 having an internally threaded hole 18 
which is threaded upon the shaft 12. This nut 16 is provided with a 
generally conical expansion surface 20 located symmetrically around the 
hole 18. When the nut 16 is located on the shaft 12 this expansion surface 
20 increases in dimension according with the distance away from the head 
14. If desired the nut 16 can have a somewhat domelike end 22 adjacent to 
the expansion surface 20 which will serve to reinforce the periphery 24 of 
the nut 16 against deformation as the fastener 10 is used. 
The fastener 10 also includes a sleeve 26 of a generally cylindrical shape. 
This sleeve includes a longitudinally extending slot or slit 28. 
Preferably the sleeve 26 differs from a cylindrical shape slightly in that 
it is deformed or twisted substantially as illustrated in FIG. 1 of the 
drawing. If desired this particular configuration may be referred to as a 
partially spiral or helical configuration. As a result of being twisted as 
shown the sleeve 26 may be regarded as a type of elongated coil spring 
which includes two end edge portions 30 and 32 which extend generally 
outwardly away from one another on opposites of the slit 28 as illustrated 
in FIG. 1. Preferably the internal diameter of the sleeve 26 is sufficient 
that it will fit relatively loosely around the shaft 14. The internal 
diameter of this sleeve 26 should, however, be sufficiently small so that 
the sleeve 26 will fit generally against the surface 20 adjacent to the 
hole 18. This will permit expansion of the sleeve 26 subsequently 
described. 
Prior to the use of the fastener 10 the shaft 12 is inserted through a hole 
34 in a first member or panel 36 so that the head 14 rests against this 
first member 36. The sleve 36 and the nut 14 are then assembled on the 
shaft 26 as indicated in FIG. 1. Preferably the nut 16 is tightened down 
during such assembly to a sufficient extent so that the portion 30 
frictionally engages the first member 36 and so that the portion 32 
frictionally engages the surface 20 approximately as illustrated in FIG. 
1. At this point the portion 30 will serve as a holding means which will 
prevent rotation of the sleeve 26 relative to the first member 36. The 
portion 30 will, of course, continue to serve this function as the sleeve 
26 is thereafter tightened down upon the shaft 12. 
Also the portion 32 on the sleeve 26 will engage the surface 20 and tend to 
"bite" into this surface to a sufficient extent to prevent relative 
rotation between the sleeve 26 and the nut 16 as this nut 16 is tightened 
down upon the shaft 12. Because of this the portion 32 can be referred to 
as a "rotation preventing means" which coacts with the surface 20 as this 
surface serves as another "rotation preventing means". In the event that 
the nut 16 is formed of a sufficient hard material that the portion 32 
will not bite into the nut 16 so as to block such relative rotation it is 
desirable to utilize a nonsmooth surface 38 on the surface 20 as a 
rotation preventing means which cooperates with the portion 32. This 
surface 38 extends in a band around the surface 20 which is transverse to 
the axis of the hole 18. Preferably it consists of a series of logitudinal 
extending ridges 40 located immediately adjacent to one another as shown. 
In the event that either the sleeve 26 or the first member 36 are of such 
relative hardness that the portion 30 will not adequately "bite" into and 
hold the first member 36 it is possible to locate a nonsmooth surface 42 
such as a knurled surface on the sleeve 26 adjacent to the portion 30 so 
as to increase the relative friction between the sleeve 26 and the member 
36. A similar surface 44 can be located on the sleeve 26 adjacent to the 
portion 32 for engaging the surface 20 for the same purpose. 
After the fastener 10 has been assembled as described it can be used by 
inserting through a hole 46 in a second member 48 as indicated in FIGS. 1 
and 2 of the drawings. This hole 46 should be sufficiently large so as to 
pass around the periphery 24 of the nut 16 and the exterior 50 of the 
sleeve 26. Also this hole 46 should be of a dimension reasonably 
corresponding to slightly less than the maximum amount that the sleeve 26 
can be expanded as subsequently described as the fastener 10 is used. Such 
use of the fastener 10 is rather simple. 
After the second member 48 has been located generally around the sleeve 26 
such use involves applying a manipulative tool (not shown) to the head 14 
so as to rotate the shaft 12. As this occurs the nut 16 will draw down on 
the shaft 12 generally towards the sleeve 26. This will cause the portion 
30 to firmly engage the first member 36 so as to secure the sleeve 26 
against rotation and will cause the portion 32 to also engage the surface 
20 and the ridge 40 so as to firmly secure the nut 16 against relative 
rotation with respect to the sleeve 26. 
Concurrently an internal terminal edge 52 on the sleeve 26 will move 
against the surface 20 so as to coact with this surface 20 in order to 
expand the sleeve 26. The edge 52 is preferably slightly rounded to 
prevent any possibility of it biting into the surface 20. If desired this 
edge 52 can be replaced with a beveled surface (not shown). Because of its 
function this edge 52 may be referred to as an expansion surface which 
coacts with the surface 20. As the sleeve 26 expands it, of course, will 
be compressed so as to be placed under compression while concurrently it 
will be expanded outwardly. Such outward expansion will increase its 
effective diameter to a sufficient point that the interior of the hole 46 
will be firmly engaged so as to secure the second member 48 in a location 
as shown in FIG. 2 of the drawings.