Mechanical tensioner

A mechanical tensioner for elongating and relaxing a stud having an axis and arranged in an object, comprises at least two parts including a first part connectable with the stud and a second part connected with the first part, and a friction element which cooperates with at least one of the parts so as to change a coefficient of friction between the parts so that one of the parts has a higher coefficient of friction than another part and when a force is applied to at least one of the parts in a transverse direction to the axis, the second part moves only in the transverse direction and the first part moves only in an axial direction to move the stud in the axial direction.

BACKGROUND OF THE INVENTION 
The present invention relates to a mechanical tensioner for elongating and 
relaxing a stud arranged in an object, such as for example a flange and 
the like. 
Tensioners of the above mentioned general type are known in form for 
example of a mechanical nut which has two elements movable relative to one 
another in opposite axial directions to elongate or relax a stud. There 
are however many applications where no gaskets are used to seal the two 
flange portions or where the stud is oversized relative to the required 
clamping force. Therefore, with a steel-to-steel flange connection there 
is no compression feasible, and with an oversized stud there is no stud 
elongation feasible, and thus axial movement of one of the parts becomes 
possible. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a 
mechanical tensioner which is a further improvement of known tensioners 
and eliminates the disadvantages of the prior art. 
In keeping with these objects and with others which will become apparent 
hereinafter, one feature of the present invention resides, briefly stated, 
in a mechanical tensioner for elongating and relaxing a stud having an 
axis and arranged in an object, having at last two parts including a first 
part connectable with said stud and a second part connected with said 
first part, and a friction element which cooperates with at least one of 
said parts so as to change a coefficient of friction between said parts so 
that one of said parts has a higher coefficient of friction than another 
part and when a force is applied to at least one of said parts in a 
transverse direction to said axis, said second part moves only in said 
transverse direction and said first part moves only in an axial direction 
to move said stud in said axial direction. 
The novel features which are considered as characteristic for the invention 
are set forth in particular in the appended claims. The invention itself, 
however, both as to its construction and its method of operation, together 
with additional objects and advantages thereof, will be best understood 
from the following description of specific embodiments when read in 
connection with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
A mechanical tensioner in accordance with the present invention is used for 
elongating and relaxing a stud 1 which is arranged in an outside object 
such as a flange 2 and the like. The mechanical tensioner has an outer 
part which is identified as a whole with reference numeral 3, an inner 
part which is identified as a whole with reference number 4, and a 
friction element which is identified as a whole with reference numeral 5. 
The outer part 3 has an end portion 7 facing away of the flange 2 and 
provided with engaging formations, for example splines 8, to be engaged by 
a tool. The outer part 3 also has a portion 9 which faces toward the 
flange 2 and has a surface 10 arranged to abut against the friction 
element 5. Finally, the outer part 3 has an inner thread 11. The outer 
part 3 is formed as a tubular member provided with the above specified 
formations. 
The inner part 4 has an end portion 12 which faces away of the flange 2 and 
is provided with a plurality of engaging formations, for example splines 
13, to be engaged by a tool. It also has an outer surface provided with a 
thread 14 which engages with the thread 11 of the inner surface of the 
outer part 3. The inner part 4 has a portion 15 which is located inside 
the cooperating part 4 and has an outer surface provided with engaging 
formations, for example splines 16. Finally, the inner part 4 has an inner 
surface provided with engaging formations formed for example as an inner 
thread 17, for engaging with the stud 1. The inner part 4 is also formed 
as a tubular member. 
The friction element is disc shaped. It is located between the end portion 
9 of the outer part 3 and the flange 2 on the one hand, and surrounds the 
portion 15 of the inner part 4 on the other hand. The friction element 5 
has an inner surface 18 provided with a plurality of engaging formations, 
for example splines 18, which engage with the splines 16 of the portion 15 
of the inner part 4. The friction element 5 has a surface 19 against which 
the surface 10 of the outer part 3 abuts, and also an opposite surface 20 
which abuts against the outer surface of the flange 2. 
The thread 11 of the outer part 3 and the thread 14 of the inner part 4 
have one direction, while the thread 17 of the inner part 4 has another 
direction. For example, the thread 17 is a right-hand thread, while the 
threads 11 and 14 are left-hand threads. 
It can be seen that the inner part 4 has four surfaces cooperating with 
other parts and subjectable to friction. In particular, it has the surface 
of the inner thread 17, the surface of the other thread 14, the end 
surface abutting against the friction element 5, and the end surface 
abutting against the flange 2. In contract, the outer part 3 has only two 
surfaces which are subjectable to friction, namely the surface of the 
inner thread 11, and the surface 19 abutting against the friction element 
5. 
During operation a tool is applied to the mechanical tensioner so that it 
engages the splines 8 of the outer part 3 to move the latter and also 
engages the splines 13 of the inner part so as to at least hole the part 
4. When the outer part 3 is moved in a direction which is transverse to an 
axis of the tensioner and the stud or more particularly is turned about 
this axis, its surface 10 abuts against the surface 19 of the friction 
element 5 and therefore the outer part 3 cannot move further onto the 
friction element 5 in the axial direction. Under the action of turning of 
the outer part 3 and due to the cooperation between the threads 11, 14 the 
inner part 4 is displaced in the axial direction, upwardly in the 
drawings, and at the same time does not displace in the transverse 
direction or in other words does not turn around the axis. During these 
movements the friction element 5 is neither displayed in the transverse 
direction (turned around the axis) nor in the axial direction. It is 
immovable relative to the flange 2. The axial upward displacement of the 
inner part 4 without the transverse displacement (turning around the axis) 
causes pulling of the stud 1 upwardly and therefore its elongating. 
Thus due to inventive cooperation of the parts 3 and 4 and the friction 
element 5 which imparts a higher friction to the inner part 4 than the 
outer part 3, when a force is applied to one of the parts 3, 4 in a 
transverse direction to the axis (by applying a force to one part, by 
holding one part and turning another part, by turning both parts in 
opposite directions with equal forces), after elimination of the gaps in 
the assembly the outer part 3 moves only in the transverse direction to 
the axis (rotates) while the inner part 4 moves only in an axial direction 
to pull the stud 1 upwardly in the axial direction. 
It is to be understood that in order to relax the stud 1 the outer part 3 
must be displaced in an opposite transverse direction (turned around the 
axis in an opposite direction) so that the inner part 4 is displaced 
axially downwardly and the stud is therefore relaxed. 
It will be understood that each of the elements described above, or two or 
more together, may also find a useful application in other types of 
constructions differing from the types described above. 
While the invention has been illustrated and described as embodied in a 
mechanical fastener for elongating and relaxing a stud, it is not intended 
to be limited to the details shown, since various modifications and 
structural changes may be made without departing in any way from the 
spirit of the present invention. 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute essential 
characteristics of the generic or specific aspects of this invention. 
What is claimed as new and desired to be protected by Letters Patent is set 
forth in the appended claims.