Device for installing threaded bushes

A device for installing a threaded bush into a work piece has a housing containing a rotatable threaded rod. A pressure responsive piston in the housing axially moves the threaded rod with respect to the housing. A rotatable abutment sleeve is provided between the housing and the threaded rod. The bush is initially threaded on the rod and then screwed in the workpiece by rotation of the rod until a collar of the bush contacts the surface of the workpiece. Thereafter the rod is axially retracted to cause the abutment sleeve to deform a smooth walled portion of the bush to complete the installation.

BACKGROUND OF THE INVENTION 
The invention relates to device for installing externally threaded hollow 
bushes having torsional locking and devices for fitting such bushes. 
Such threaded bushes are known in various designs. 
In the case of a threaded bush whose external thread itself cuts the 
corresponding internal thread in the workpiece, the torsional locking is 
achieved by a radial pinning. With this torsional locking, after screwing 
in the self-tapping threaded bush, drilling has to be carried out across 
the junction between the threaded bush and workpiece and a securing pin 
inserted in the drilled hole. Such an arrangement is very expensive. The 
threaded bush is expensive in itself, since not only the actual bush body 
has to be provided but also the securing pin. 
Threaded bushes are also known having an external thread in which 
longitudinal grooves are provided. Wedges are driven into these 
longitudinal grooves which wedges project beyond the longitudinal grooves 
and engage in the material of the workpiece. Here also, the fitting of the 
bushes is very expensive and the threaded bush itself is correspondingly 
expensive because of its multi-component nature. 
In another kind of threaded bush, a toothed securing ring (such as shown in 
U.S. Pat. No. 2,452,262) is pressed in over the neck of the inserted bush. 
The object of the invention is to provide a one-piece threaded bush with 
torsional locking. 
SUMMARY OF THE INVENTION 
According to the invention there is provided an externally threaded hollow 
bush having an integrally formed, surrounding collar of non-circular 
peripheral shape, and an adjoining, essentially smooth-walled portion 
having a lower wall thickness than an externally threaded portion of the 
bush adjoining the smooth-walled portion, so that after screwing the 
threaded bush into a receiving hole of a workpiece until the collar comes 
to rest on the surface of the workpiece, the collar can be pressed into 
the surface of the workpiece by axial loading of the collar, entailing a 
reduction in the axial length of the smooth-walled portion. 
In use, the threaded bush is screwed into a hole in the workpiece until the 
collar rests on the upper side of the workpiece. Subsequently, the collar 
is pressed into the workpiece until the upper side of the collar is flush 
with the surface of the workpiece. The opposing force for the compression 
occurring on pressing the collar into the workpiece is preferably not 
derived, in the case of non-self-tapping external threads, by the 
engagement of the external thread with the internal thread of the 
workpiece, but by a traction force exerted on the threaded portion of the 
bush, so that play in the thread engagement between workpiece and bush is 
taken up. The provision of a special space for compression in the relevant 
portion of the internal thread of the workpiece is not necessary. 
Preferably, the non-circular peripheral shape of the collar is achieved in 
that the collar is provided with fissures extending forwards and backwards 
in a radial direction like, e.g. toothing, milling or the like. 
Alternatively, the peripheral edge of the collar may be polygonal, for 
example hexagonal. 
Where the application is for hydraulic purposes and with other applications 
where a completely tight connection is necessary between the threaded bush 
and the workpiece, it is practical to surround the smooth-walled portion 
by a sealing ring, preferably an O-ring. 
The threaded bush may feature an internal thread into which, after the 
threaded bush has been inserted into a workpiece, another threaded member 
can be screwed. On the other hand, it is also possible for the threaded 
bush to feature a screw fitted in it coaxially, the threaded portion of 
which screw protrudes beyond the collar at one end of the bush. 
With threaded bushes of this kind, and also with threaded bushes having an 
internal thread, it is extremely advantageous if the essentially 
smooth-walled portion is so arranged that it always deforms outwardly. 
Thus, in a practical embodiment of the invention, it is provided that the 
centre line of the wall thickness of the smooth-walled portion is domed 
outwards with respect to the axis of the bush as it extends axially of the 
bush. 
By deviating the centre line of the wall thickness from a direction 
parallel to the bush axis, it is achieved that during the pressing of the 
collar into the workpiece and the consequent compression of the 
smooth-walled portion, the smooth-walled portion deforms away from the 
axis of the threaded bush so that danger of restricting the internal 
cross-section does not arise and, especially in the case of threaded 
bushes with an internal thread, screw members can be screwed into the 
internal thread without difficulty and threaded members which are to be 
screwed onto the threaded bushes with bolts can be brought into screwed 
engagement. 
The invention more particularly provides a device with which the threaded 
bush can be rapidly installed in a simple manner. 
Accordingly, the invention provides a device, for the fitting of threaded 
bushes, comprising a housing, a threaded rod rotatably located in the 
housing, which rod can be displaced axially by a piston which is subjected 
to pressure and is arranged to execute relative movement with respect to 
the housing. Known devices for fitting threaded bushes are not suitable 
for fitting the threaded bushes according to the invention as fouling of 
the threaded bush held by the thread against a fixed adjacent section of 
the housing would occur. 
For this reason, according to the invention, it is provided that a 
rotatable abutment sleeve is provided between the housing and the threaded 
rod. 
In the following, preferred embodiments of threaded bushes according to the 
invention, and a device for fitting these threaded bushes, are described 
in greater detail.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The threaded bush B shown in FIGS. 1 to 3 consists of a collar 1 formed 
peripherally with six sides, a threaded portion 2 and a tube-like portion 
3, essentially smooth-walled, arranged between the collar and the threaded 
portion and having a wall thickness less than the core cross-section of 
the threaded portion 2, which is provided with an internal thread 2a and 
an external thread 2b. As can be seen from FIG. 3, the maximum diameter of 
the collar 1 is so selected that it protrudes beyond the peripheral edge 
of a threaded hole 5c in a workpiece 5. 
To insert the threaded bush B into the workpiece 5, the bush B is first 
screwed into the hole 5c, by means of a threaded rod 6 which features an 
external thread 6a on one of its ends, until the lower side of the collar 
1 rests on the surface 5a of the workpiece 5 (see FIG. 2). Subsequently, 
an abutment 7, formed as a ring encircling the rod 6 and having a bearing 
surface 7a, is urged into contact with the upper side of the collar 1 so 
as to press the collar 1 into the workpiece. To achieve this, traction 
forces are applied to the threaded rod 6 in the direction of the arrow 6b 
and pressure forces are applied to the abutment 7 in the direction of the 
arrows 7b. Since the thread 6a on the rod 6 is engaged with the internal 
thread 2a of the threaded portion 2, as the collar 1 is pressed into the 
workpiece, the play between the external thread 2b and the threaded hole 
5c in the workpiece is taken up. 
On pressing in the collar 1, the smooth-walled portion 3 is compressed and 
receives the shape which can be seen in the upper right hand part of FIG. 
3. 
The material from which the threaded bush B is made is harder than the 
material of the workpiece 5; for example, the bush may be of steel and the 
workpiece of cast aluminium. On pressing in the collar 1, the displaced 
workpiece material closes tightly around the peripheral surface 5b of the 
collar 1, so that a practically uninterrupted transition is achieved 
between the peripheral surface of the collar 1 and the material of the 
workpiece 5. 
In order to ensure deformation of the smooth-walled portion 3 in a 
direction outwardly away from the axis of the threaded bush B, regardless 
of the shape of the threaded rod 6, the distribution of wall-thickness of 
the smooth-walled portion 3, in the axial direction of the threaded bush, 
can be so selected that the centre line M.sub.3 of the portion 3 (see FIG. 
3a) is domed outwards with respect to the axis of the threaded bush. 
An embodiment of the threaded bush is shown in FIG. 3a in which the 
internal surface 3a as well as the external surface 3b of the portion 3 
are domed outwards. 
In the alternative embodiment according to FIG. 3b, the internal surface 3a 
is domed outwards, whilst the outer surface 3b is a cylindrical surface 
parallel to the axis of the threaded bush B. 
In both embodiments, the centre line M.sub.3 of the wall is domed outwards 
with respect to the axis of the threaded bush. The centre line need not 
necessarily exhibit a constant curvature, such as for example a catenary, 
but can also follow a polygonal course. In FIGS. 3a and 3b, the height of 
the smooth-walled portion 3 is indicated by h and the thickness of the 
collar 1 by d. On deformation, the height h is reduced by the thickness d. 
The height h must be at least equal to the thickness d plus the required 
remaining height of deformation h.sub.R, as shown for example in FIG. 3. 
This remaining height of deformation h.sub.R is determined by the wall 
thickness of the smooth-walled portion and by the extent of the desired 
and permissible deformation. 
In the embodiment according to FIGS. 4 to 6, the smooth-walled portion 3 is 
surrounded by a sealing O-ring 3c, which, in the installed condition of 
the threaded bush, lies between the internal thread of the threaded hole 
5c and the compressed smooth-walled portion 3 and is correspondingly 
deformed. For installation purposes, the tools which are employed for 
installing the threaded bush according to FIGS. 1 to 3 can also be used. 
In the embodiment according to FIG. 7, the internal thread in the threaded 
portion 2' has been replaced by a smooth-walled stepped hole 4, the 
widened section of the hole being at the opposite end to the collar 1'. A 
threaded bolt 8 with a head 8a is passed into the threaded bush B' from 
the end having the widened section, the threaded shaft 8b of the bolt 
protruding beyond the upper side of the collar 1'. The head 8a of the bolt 
rests on the step 4a of the stepped hole 4 and is spot welded to the 
threaded portion 2', as shown at 9 in FIG. 7. 
The embodiment according to FIG. 8 differs from that of FIG. 7 in that the 
stepped hole 4' is provided with a thread 4b' in its smaller diameter 
section, which thread cooperates with the external thread of a 
correspondingly formed screw 8' having a head 8a'. The screw 8' is screwed 
into the threaded bush from the end having the wider diameter section 
until the head 8a' rests on the step 4a'. The axial length of the wider 
diameter section of the stepped hole 4' is sufficiently large so that the 
free rim of the stepped hole can still be turned over to form a lip 10, 
which firmly retains the screw against rotation in the bush. 
In FIGS. 7 and 8, a sealing ring 3c' is also shown, although this is not 
absolutely necessary. 
In order to install the threaded bushes according to FIGS. 7 and 8, the 
leading end of the threaded rod 6 must be correspondingly modified, i.e. 
the rod must be shortened and the external thread 6a must be replaced by a 
corresponding internal thread. This is explained further below with the 
aid of FIG. 10. 
In FIGS. 9 and 9a, a device for installing the threaded bushes according to 
FIGS. 1 to 6 is shown. 
In a housing 10 provided with a through bore 10a, a cylinder chamber 11 is 
formed at one end, which chamber is open at one side and, at the other 
side can be subjected to a pressure medium by means of a pressure feed 
passage 12 formed in the housing and opening into the bottom of the 
cylinder chamber. 
The through bore 10a is provided with an internal thread 13 at the opposite 
end of the housing 10 to the cylinder chamber 11. 
In the cylinder chamber 11 is disposed a piston 14 having an annular 
working surface 14a which can be subjected to pressure and which faces the 
bottom of the chamber 11, which surface, in the rest position of the 
piston 14 shown in FIG. 9, is held at a predetermined distance from the 
bottom surface of the cylinder chamber 11. The piston 14 consists of a 
hollow piston head 14b and a hollow guide extension 14c engaging in the 
through bore 10a. The internal diameter of the piston head 14b is larger 
than the internal diameter of the guide extension 14c so that a step 14d 
is formed between the two chambers defined within said members. 
The outer diameter of the piston head 14b is stepped in the manner shown in 
FIG. 9. The section of the piston head 14b with the larger diameter 
cooperates with the wall of the cylinder chamber 11. A sealing ring 15 is 
located between the through bore and the outer surface of the hollow guide 
extension 14c, and between the wall of the cylinder chamber 11 and the 
increased diameter section of the piston head 14b. 
A hollow mouth-piece 16 provided with an external thread is screwed into 
the thread 13. The internal diameter of the mouth-piece 16 corresponds to 
the internal diameter of the hollow guide extension 14c. The mouth-piece 
is releasably connected to the housing 10 by means of the screw connection 
to enable various threaded bushes to be installed. The mouth-piece 16 is 
provided with an external thread on to which a locking ring 17 is screwed 
so that the mouth-piece 16 can be secured to the housing by the locking 
ring 17 so as to be free from play and secured against rotation. A rod 20, 
having a threaded portion 23 at one end, extends coaxially through the 
mouth-piece 16 and the hollow guide extension 14c of the piston and up to 
the internal chamber of the piston head 14b. Between the outer surface of 
the rod 20 and the internal surfaces of the mouth-piece 16 and the guide 
extension 14c, an abutment sleeve 21 is arranged the outer surface of 
which contacts the inner surfaces of the mouth-piece 16 and the guide 
extension 14c, whilst its internal surface is spaced by a predetermined 
amount from the outer surface of the rod 20. 
As can be seen from FIG. 9, a free space is provided in the through bore 
10a between the end of the mouth-piece 16 and the end of the guide 
extension 14c. An O-ring or an oil seal 21a is arranged in this free space 
between the housing 10 and the abutment sleeve 21, and retains the sleeve 
21 in the housing. 
At its end protruding from the mouth-piece, the abutment sleeve is provided 
with a radially extending abutment flange 21b the dimensions of which 
correspond to those of the collar 1 of the threaded bush. As further 
explained below, the length of the abutment sleeve is predetermined to be 
greater than the distance between the end of the mouth-piece 16 protruding 
from the housing 10 and the step 14d of the piston in its rest position. 
The threaded rod 20 is provided with a head 22 on its end which protrudes 
into the interior of the piston head 14b, the radial dimensions of which 
head 22 are so selected that it can come into contact with the step 14d of 
the piston and against the end surface of the abutment sleeve 21. 
The piston head 14b of the piston 14 protrudes in an axial direction out of 
the cylinder chamber 11 and is provided with an internal thread 14e at its 
end remote from the guide extension 14c. A compression spring 24 is 
arranged around the smaller diameter section of the piston head 14b and 
engages the step between the smaller diameter section and the larger 
diameter section of the piston head 14b. 
The housing of a drive motor 25 is screwed into the thread 14e. In the head 
22, there is formed a hexagon-shaped recess 22a into which a 
hexagon-shaped drive element 25a of the drive motor 25 engages. 
At the end of the housing 10 containing the cylinder chamber 11, the 
housing is provided with an external thread 10b on to which a closure cap 
26 provided with an internal thread is screwed. The cap 26 is provided in 
the bottom 26a thereof with an opening 26b through which the casing of the 
drive motor 25 protrudes. For locating the closure cap 26 on the housing 
10, a lock nut 27 is arranged on the thread 10b. The other end of the 
pressure spring 24 engages the bottom 26a of the closure cap and presses 
the piston into contact with the bottom of the cylinder chamber 11. The 
length of stroke of the piston 24 is determined by adjustment of the 
closure cap 26 on the thread 10b. 
On the drive motor a switch lever 31 is provided with which the motor can 
be switched on and off, whilst with the help of a change-over button 32 
the rotational direction of the drive element 25a can be determined. It is 
possible that also, together with the switch function of the switch lever, 
a speed regulating function can be assigned to it, depending on the degree 
of depression of the lever. 
The device shown in FIG. 9 operates as follows. When it is wished to 
install a threaded bush B into a workpiece 5, the threaded bush B is first 
threaded onto the threaded section 23 of the rod 20 one or two turns by 
hand, so that the threaded bush B is held for a short time on the threaded 
section 23 of the rotating rod 20, with the motor turning clockwise. 
Whereupon, the bush B is placed on the threaded hole 5c of the workpiece 5 
and the threaded bush rotating with the rod 20 is screwed into the 
threaded hole 5c. During this process, the threaded bush is first screwed 
on to the threaded section 23 of the rod 20 until the collar 1 contacts 
the abutment 21b of the abutment sleeve 21 and, on further rotational 
movement, the bush B is screwed into the threaded hole 5c. Since the 
abutment sleeve 21 can rotate with the rod 20, locking of the threaded 
bush B with the mouth-piece 16 fixed to the housing is prevented. The 
length of the abutment sleeve 21, already emphasised above, which provides 
axial spacing a between the abutment flange 21b and the end surface of the 
mouth-piece 16, is thus especially important. It is also possible to 
arrange a thrust bearing between the abutment 21b and the opposing end 
face of the mouth-piece 16, in order to permit the rotation of the 
abutment sleeve 21 with respect to the mouth-piece and thus with respect 
to the housing 10. 
When the threaded bush has been screwed in until the collar 1 contacts the 
surface of the workpiece 5, the drive motor 25 is switched off and the 
pressure feed 12 is connected to a source of pressure medium by means of a 
valve which is not shown, so that the working surface 14a of the piston 
head 14 is subjected to pressure. Since the threaded section 23 of the rod 
20 is screwed into the internal threading 2a of the bush, and the bush is 
held in the workpiece, relative movement takes place between the piston 
14, engaging the head 22 of the threaded rod 20 by way of the step 14d, 
and the housing 10 and the mouth-piece 16. During this movement, the 
surface of the mouth-piece 16 facing the abutment flange 21b comes into 
engagement with the abutment flange so that a transference of force occurs 
from the collar 1 of the threaded bush B by way of the abutment flange 21b 
directly onto the mouth-piece 16 and thus the housing 10, without the 
cylindrical hollow portion of the abutment sleeve 21 being subjected to 
load. In this manner it is ensured that the abutment sleeve 21, especially 
in the area of the through bore 10a between the facing ends of the 
mouth-piece 16 and the guide extension 14c of the piston, cannot deform 
thus possibly also destroying the O-ring 21a. The supply of pressure by 
way of the pressure line is maintained until the insertion and pressing-in 
process of the collar 1 of the threaded bush B is completed and its upper 
side is flush with the surface of the workpiece 5. The final position of 
the tool and the deformed bush B are shown in FIG. 9a. 
After pressing-in the collar 1, the drive motor 25 is rotated anticlockwise 
by corresponding actuation of the lever 31 and the change-over button 32, 
and the threaded portion 23 of the rod 20 is unscrewed from the internal 
thread 2a of the threaded bush B. The piston 14 and the motor carried by 
it are moved back by the pressure spring 24 into the position relative to 
the housing 10 shown in FIG. 9. 
It should be mentioned here that the drive motor 25 may be of the kind 
driven by a pressure medium, pressure being fed to the motor through a 
pressure line which is not shown. However, it is also possible to employ 
an electric motor. 
For inserting the threaded bushes according to FIGS. 7 and 8, the rod 20 of 
the device of FIG. 9 is replaced by a rod 20' of the kind shown in FIG. 
10. The rod 20' is provided on its working end with an internal thread 
23', which is screwed onto the external thread 8b of the bolt 8. If need 
be, also with this embodiment, by reason of the rotatability of the 
abutment sleeve 21 with respect to the housing 10 and the mouth-piece 16 
locking of the threaded bush with the bolt to the fixed mouth-piece 16 is 
prevented. 
The construction of the device shown enables a simple replacement of the 
rods 20 and 20' in which the drive motor 25 is screwed out of the piston 
and after removing one rod, the other rod is inserted and then the drive 
motor is screwed in again. Even if an exchange of rods is not intended, 
the embodiment of the tool shown enables an economic production of tools 
for the two types of threaded bushes in question.