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1. (WO1986003810) DISPOSITIFS DE FIXATION
Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

CLAIMS

1. A method of increasing the resistance to
pull out of a screw screwed into a receptive
substrate which comprises unscrewing the screw and removing it from the hole and then
5. a) providing a spiral member having an outwardly facing pointed profile and having a cross-section such as to fit between adjacent turns of the thread on the screw, and such that the dimension of a turn perpendicular to the longitudinal axis of the spiral

10. (herein called the radial depth) is greater than the height of the thread of the screw with which that turn will be associated in step c), the spiral
member being of intermediately malleable material
(as defined herein), the spiral member being turned

15. inwardly and back down the axis at one end to afford a drive pin, thus being shaped so as to be
disconnectably engageable by a tool inserted down the centre of the spiral member whereby the force to screw the spiral member into the hole can be exerted

20. from the drive pin or bottom end of the spiral
member,
b) locating the spiral member in the threaded hole with its axis along that of the hole, the
spiral member at least at this stage having an
25. internal diameter less than that of the root of the screw, and
c) screwing the screw into the hole, the spiral member engaging the hole and the screw threadly
engaging the spiral member and forcing the pointed

30. profile into the substrate.

2. A method as claimed in Claim 1 in which the cross-section of the spiral member affords an
outwardly facing projection and an inner thrust face adapted to bear against at least a substantial part

5. of the root of the screw.

3. A spiral member of intermediately malleable material (as defined herein), the spiral member
being turned inwardly and back down the axis at one

10. end to afford a drive pin.

4. A spiral member as claimed in Claim 3 of non-circular cross-section in which each turn
affords an outwardly facing projection, an inner

15. thrust face opposed to the axis of the spiral
member, and at least one longitudinal thrust face.

5. A spiral member as claimed in any one of
Claim 3 or Claim 4 which is made of aluminium or

20. aluminium alloy.

6. A spiral member as claimed in Claim 3, 4 or 5 which is tapered towards the end affording the
drive pin.
25.
7. A tool for inserting a spiral member as
claimed in any one of Claims 3 to 6 which comprises a shaft adapted to extend through the spiral member with engaging means at its bottom end adapted to fit

30. the bottom end of the spiral and a driving means at its other end and stop means near the drive means adapted to prevent the shaft penetrating beyond the bottom of the hole in the sleeper, the engaging
means enabling the tool to releasably engage the
spiral member so as to provide a driving engagement whilst the assembly is being screwed into the
sleeper but a non-driving engagement when the tool is screwed out of the hole, by rotation in the
opposite direction.
10
8. A tool as claimed in Claim 7 provided with means for holding the turns of the spiral member in axially spaced apart relationship.

15. 9. An assembly of a spiral member as claimed in Claim 3 and a tool as claimed in Claim 7 in which the tail of the drive pin is located in an axial
hole in the end of the tool, the relationship of the tail of the drive pin to the hole being such that

20. whilst the assembly is screwed into a hole in a
sleeper from which a screw-spike has been removed it remains in the hole in the tool but the tool can
rotate away from the tail of the drive pin and leave the spiral member in place.
25.