Note: Descriptions are shown in the official language in which they were submitted.
13336~2
Method for forming a screw thread and tubular body with
a screw thread
The invention relates to a method for the non-cutting
shaping of a screw thread in one side or the surface of a
tubular body member. The invention also relates to a tubular
body with internal threads in the form of an approximately
round screw-thread. The tubular body is used in a screw-
threaded connection between two cylindrical and especially
tubular components, for example, parts of a rock anchor, a
drilling rod or the like.
It is customary to connect together the extension
rods of rock anchors, drilling rods and the like with screw
connections. For this, the two juxtaposed drilling rod or
rock anchor parts to be connected together have an external
thread and are connected by means of a connecting sleeve having
a corresponding internal thread. Especially with drilling
rods, these thread sections serve simultaneously as coupling
regions for coupling a rock hammer or other driving apparatus.
In order to enable easy handling of these threaded connections
in view of the high loads which apply and also with heavy
soiling, it is usual to make use of a round thread or an
approximately round thread.
It is known to manufacture an internal thread on such
connecting sleeves by a cutting process, particularly by screw
thread cutters and so on. Not only is the extent of the
amount o~ cutting involved a disadvantage, but so also is the
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, -2- I333652
transverse weakening of the sleeve caused by the volume of
material cut away as well as the notching effect involved in
the cutting, particularly at the bottom of the separate thread
turns, by which the durability of the sleeve is adversely
; ~ affected.
It is therefore an object of the present invention to
provide a method for the non-cutting forming of a screw thread
and a tubular body carrying a screw thread, which is easy to
carry out or manufacture, is particularly adapted for low
manufacturing costs and enables the preparation of a screw
connection ensuring high strength. This object, insofar as
the method is concerned, is obtained by a method wherein
threaded turns are formed in the other side of the body
member, the copy of which, arising by corresponding
deformation of the other side, produces the screw thread to be
formed.
More particularly, the invention provides a non-cutting
method for forming an internal thread in a tubular body
intended and dimensioned for use as a connecting sleeve for
bore rods and ground anchors, said body having an internal
surface and an external surface, wherein threads are formed in
the external surface of the body by means of cylinders or
rollers, characterized in that: a) the internal thread is
produced by freely displacing material of the body comple-
mentary to the threads on the external surface, as saidthreads on the external surface are being formed, to form an
internal thread of approximately circular cross-section having
a pattern corresponding to the threads formed on the external
surface, b) the threads formed on the external surface of the
body are formed in such a way as to leave smooth, only insig-
nlficantly shaped surface sections between the individual
threads, and c) the depth of the threads formed on the exter-
nal surface is less than the material thickness of the body.
It is essential to the invention that, as with the known
non-cutting forming process, the screw thread to be made is
formed directly by a shaping tool engaging the side of the
basic tubular article, since this formation applies in, for
.
13336S2
- 2a -
instance, an external shaping contact to the resultant
internal formation. In the manufacture of a connecting
sleeve, thus a start can be made from a smooth tubular work-
piece, which by external forming receives an internal screw-
thread, the profile of which is then annealed to a round
thread. The measurements of the original smooth-walled
starting member are dimensioned dependent upon the
measurements of the counter-thread to which the sleeve is to
be screwed, so that a minimum clearance is given between the
threaded turns when brought into engagement with one another.
It is of particular advantage that the internal thread formed
in this way can be made in a single forming step. In
comparison to a screw-cutting process the manufacturing costs
of a sleeve provided with an internal thread are considerably
reduced.
The manufacture of an internal thread in a connecting
sleeve wherein the screw thread is formed on the internal side
- 3 1333652
of the body member and then the threaded turns are formed in
the external side represents the most important application
of the method of the present invention. Fundamentally, all
non-cutting formin~ methods can be used in the manufacture,
including hot forming and also cold forming methods. It is
particularly advantageous, especially in view of the low
tolerances to be achieved as well as the strength of the
work-piece connected with the shaping, to use a cold forming
method.
The features of the method wherein the basic shape
of the screw-thread profile formed by the threaded turns of
the other side or the external side of the body member is
used as the counter profile for a screw connection bring the
advantage that the same method of operation can be used for
both the manufacture of the internal thread and also for the
manufacture of the external thread co-operating with it,
where merely the shaping tool must be somewhat adapted for the
purposes of adapting to the curved screw thread flanks of the
internal thread, as well as for establishing the necessary
clearance between the internal and external threads.
It is particularly advantageous to use the method
according to the invention in the manufacture of connecting
sleeves which are used in the coupling of extension rods to
a rock anchor, a drilling rod or the like. In these cases
which are characterised by an extremely high mechanical loading,
it is particularly effective that the connecting sleeve is
strengthened by the proposed shaping process and consequently
achieves a high strength. Also, because of the heavy soiling
to be expected, a rounded thread or a similar type of thread
is preferred, in order to ensure satisfactory handling in the
extreme conditions of use. Since the method of manufacture
according to the invention is connected with a flow of the
material, it is naturally limited - without reference to the
- actual shaping contour - to the manufacture of such types of
screw-threads in which no sharply angled edges are to be made,
1333652
as occurs for example with a metric screw thread. Preferably,
in the case of drilling rods, the whole outer contour
including that of the connecting sleeve, is provided with
thread formations, so that with narrow bore-holes the external
guidance or discharge of drilling fines is facilitated.
It is very advantageous to use the method according
to the present invention in the manufacture of connecting
sleeves which are inserted into channel struis. It is
particularly advantageous in this connection that the
connecting sleeves according to the invention can, in practice
be constr w ted to any length. Together with good guidance of
the threaded spindles, a most satisfactory constructional
shape is also given.
The object explained at the beginning, insofar as it
relates to a tubular body provided with a thread as well as a
threaded connection as such, is achieved by a tubular body
according to the invention as well as a threaded connection
also according to the invention.
The invention is more closely described with
reference to the embodiment of a threaded connection illustrated
in the drawings in which:
Fig. 1 is a partial view of a rock anchor
simultaneously used as a drilling rod;
Fig. 2 is an enlarged view in elevation of a
connecting sleeve according to the invention;
Fig. 3 is a sectional illustration of the connecting
sleeve according to Fig. 2 in a section plane III-III;
Fig. 4 is a diagrammatic threaded connection according
to the invention representing one section;
Fig. 5 is a connecting sleeve according to the
invention intended for use with a dou~le-sided channel strut.
The bore-hole-side end part of a rock anchor is
indicated by 1 in Fig. 1, which is also used as a drilling rod.
This end part 1 is thus a tubular body, which carries a known
drill head 2 on its end remote from the drill base. The drill
head 2 is provided with a central bore in a manner not shown
- 133365~
-- 5
in the drawing, which serves to guide a drilling medium.
This bore is in communication with the internal space of the
end part 1.
The end part 1 or the tubuIar body 1 has a threaded
section 3, which is connected by means of a connecting sleeve
4 to an extension rod 5. The extension rod 5 carries a
threaded section 6. The extension rod 5 is generally
constructed as a tubular body like the end part 1. Basical-ly,
several of such extension rods 5 can be connected together and
thus the total length of the rock anchor can be adapted to
existing requirements over wide limits. Also, the showing of
the section of the preceding rock anchor located in the region
of the bore-hole-side end, to which a drilling hammer or other
driving device is coupled during the drilling operation, has
been omitted for reasons of clarity in the drawing.
The screw-thread sections 3,6 illustrated as external
threads on the tubular bodies 1,5 as well as the internal
thread of the connecting sleeve 4, not shown in Fig. 1 and
connected with these, are made as approximately round threads
in the embodiment shown, which facilitates trouble-free
handling despite the heavy soiling arising during the drilling
operatisn. According to the invention, the internal thread
of the connecting sleeve 4 is made by a non-cutting shaping,
here by a cold-forming operation, in which the connecting
sleeve 4 is given the profile shown in ~ig.l, by means of a
forming tool on the outside 7, where the internal thread is
formed by internally effective displacement of the material
complementary to the external profile. Further reference is
made to this below in relation to Figs. 2 to 4. As the view
of a connecting sleeve 4 shown in Fig. 2 indicates, the
outside 7 consists of a helically-shaped wound deformation 8
of approximately arcuate shape in cross-section, where
between the separate shaped turns 8, smooth land surface
sections 9 which are only slightly deformed remain.
Fig. 3 indicates that, by the shaping process on the
inside 10 of the threaded sleeve, screw-threaded turns 11 are
-- 1333652
~ formed whose cross-sectional shape agrees essentially with the
~ circular arcs and which can thus be regarded as rounded
threads. These thread turns 11 lie directly opposite the
formations 8. It is essential for the article of the invention
that the formation of these internal threaded turns 11 be
controlled at least accurately enough, both as regards the
depth of the threads and also in relation to the pitch, by
the externally-effective deformation, that the threaded turns
11 can function as internal threads in relation to a given
external thread, which in the present case is formed by the
threaded sections 3,6.
Fig. 4 shows in this way the effective pairing of the
turns of the internal threads of the connecting sleeve 4 on
the one hand and the external threads of the threaded secti~n
3 on the other hand. The threaded sections 3,6 are likewise
made by a cold forming process and consequently exhibit a
profile which corresponds qualitatively to that of the external
part 7 of the connecting sleeve 4.
The invention is not limited to its use with
connecting sleeves for rock anchors. Fundamentally, it can
find advantageous use in all cases in which a tubular starting
body has to be provided internally with a round thread or a
comparable screw thread.
In Fig. 5, an embodiment of a connecting sleeve 4 is
shown, which can be used with a two-sided channel strut
formation and is consequently provided with two different,
namely counter-handed, threaded sections 12,13. In the end
regions of this connecting sleeve, 4 threaded spindles can be
i~serted, which serve in a known manner to support the channel
walls of an excavation. These threaded spindles have an
external profile which corresponds essentially to that of the
tubular bodies 1,5 of Fig. 1, (the threaded spindles are not
represented for reasons of simplicity in the drawing). In order
to carry out, by a relative rotation of the connecting sleeve
4 with respect to the threaded spindles, removal of the latter
or their contact with the channel walls which are to ~e
1333652
supported, the connecting sleeve 4 is provided, in a way,
likewise not shown in the drawing, with means for initiating
a turning movement. In the simplest case, this auxiliary
device can be a hole in which a lever can be inserted. Also a
nut or a shaped tube can be welded to the connecting sleeve 4,
which serves to allow a turning movement in connection with a
corresponding tool. If required, a plastics nut can be cast
or pressed into the exterior of the connecting sleeve 4.
Since the connecting sleeve 4 with the internal thread
made according to the invention can be made to any practical
length, a particularly reliable connecting sleeve which
improves the resistance to bending of threaded spindles of
channel struts is given. Simultaneously, in this way the
separate parts of the channel struts can be made relatively
small by reason of the length of the connecting sleeve.
