Piston rod support

A mechanism for supporting a piston rod in a cylinder head includes a bearing bushing surrounding the piston rod and secured in a through opening in the cylinder head. A sleeve of elastic material is arranged between the bearing bushing and the wall of the through opening and surrounds the bearing bushing.

FIELD OF THE INVENTION 
The invention relates to a mechanism for supporting a piston rod in a 
cylinder head with a bearing sleeve which surrounds the piston rod and is 
secured in a through opening of the cylinder head. 
BACKGROUND OF THE INVENTION 
Such piston rod supports are known in pneumatic and hydraulic working 
cylinders, in which the piston and with it the piston rod are moved back 
and forth by suitably loading the piston with a pneumatic or hydraulic 
working medium. Said movement is often used to drive an article which is 
fixedly connected to the outer end of the piston rod. In this case one 
obtains for the unit which is formed by the piston and the piston rod a 
so-called three-point bearing, since the piston is guided in the cylinder 
and the piston rod is guided in the cylinder head and in addition the 
piston rod is secured on the article to be driven. This three-point 
bearing represents a redundancy in guidance, which in previous working 
cylinders, in which the piston rod is supported rigidly in the cylinder 
head, leads to considerable disadvantages. 
If for example the axis of the movement of the driven article does not 
exactly coincide with the cylinder axis, the piston rod is slightly tilted 
during its back and forth movement, which results in a canting of the 
piston rod in the area of the bearing bushing. This results in increased 
friction, which produces not only wear of the bearing bushing, but also an 
energy loss. This friction also brings about, particularly at low speeds, 
a suddenly occurring, or jerky, movement of the piston rod. 
Therefore, the basic purpose of the present invention is to produce a 
piston rod support, in which a canting of the piston rod on the bearing 
bushing is avoided. 
This purpose is attained inventively by arranging a sleeve of elastic 
material between the bearing bushing and the wall of the through opening, 
which elastic sleeve encloses the bearing bushing. 
In this manner one obtains so to speak a floating support of the bearing 
bushing and thus also of the piston rod in the through opening, so that 
the piston rod tilts as permitted by an elastic deformation of the elastic 
sleeve and can be adjusted to the axis of movement of the driven article, 
without canting of the piston rod with respect to the bearing bushing. 
Advantageously, the sleeve projects axially beyond both sides of the 
bearing bushing, wherein the two projecting end sections of the sleeve are 
constructed as seals which rest on the piston rod. Thus in this exemplary 
embodiment the sleeve serves not only for supporting the bearing bushing, 
but it forms also an inner and outer seal, of which the outer seal serves, 
aside from its sealing action, also to wipe off dirt particles from the 
piston rod. 
The two end sections of the sleeve can radially grip over the ends of the 
bearing bushing, wherein the two end sections of the sleeve together with 
the center sleeve section, which extends between them, define a recess 
which receives the bearing bushing, so that the bearing bushing is also 
held securely in axial direction by the sleeve. 
If the bearing bushing is held in a snap fit in the recess, the bearing 
bushing can be inserted simply and yet permanently into the sleeve. In 
this case it is also possible, depending on use conditions, to insert 
bearing bushings of different material into the same sleeve. If necessary 
it is also possible to easily take apart the sleeve and the bearing 
bushing, so that for example a worn sleeve can be replaced without 
replacing the bearing bushing. 
A further advantageous measure consists in the two end sections of the 
sleeve being constructed as lip seals, in which each end section has a leg 
forming a sealing lip, which leg is directed away from the bearing sleeve 
and extends slightly inclined inwardly toward the piston rod.

DETAILED DESCRIPTION 
The working cylinder which is illustrated in FIG. 1 has a cylinder head 10 
as a front-side closure, which is connected to the cylinder wall 34 in any 
conventional manner, for example by screws (not shown). A piston 36 is 
guided inside of the working cylinder, which piston is connected fixedly 
to a piston rod 16. Said piston rod 16 penetrates through a through 
opening 12 of the cylinder head 10. The outer end 38 of the piston rod 16 
is threaded for fastening an article, or load, which is to be driven by 
the working cylinder. 
The piston rod 16 is supported and guided in the cylinder head 10 with the 
help of a device 14, which comprises a bearing bushing 20 which receives 
the piston rod. The bearing bushing consists for example of a sintered 
material, a plastic material of low sliding friction, bearing bronze or a 
different suitable bearing material. A sleeve 18 of elastic material, for 
example of rubber, is arranged between the bearing bushing 20 and the wall 
of the through opening 12, which sleeve encloses the bearing bushing 20. 
Due to this elastic sleeve, the bearing bushing 20 rests over its entire 
length always on the piston rod, even when the piston rod is slightly 
tilted with respect to the cylinder head 10, since the tilting is absorbed 
by the elastic sleeve. 
The sleeve 18 of the exemplary embodiment illustrated in FIG. 1 has end 
sections 22, 24 which are formed in one piece with the sleeve 18, and by 
which the sleeve 18 axially projects on both ends over the bearing bushing 
20. Said end sections 22, 24 are constructed as seals, here as lip seals, 
which rest on the piston rod 16. Both the outer end section 22 and the 
inner end section 24 have for this purpose a leg 26 constituting a sealing 
lip, which extends away from the bearing bushing and is slightly inclined 
upwardly toward the piston rod 16. Of these two sealing lips 26, the 
sealing lip of the sleeve inner end section 24 serves to seal off the 
inside of the cylinder, while the sealing lip of the sleeve outer end 
section 22 serves mainly for wiping off of dirt particles from the piston 
rod 16, when same is moved into the cylinder. The sealing action of the 
sealing lip of the inner end section 24 is increased additionally by its 
sealing edge 28 being pressed against the piston rod 16 not only by its 
own elastic pretension but also by the pressure existing in the cylinder. 
The two end sections 22, 24 of the sleeve 18 radially grip over the bearing 
bushing 20, so that the two end sections 22, 24, together with the sleeve 
section 30 which extends between them, define a recess 32 which receives 
the bearing bushing 20. The bearing bushing 20 is positioned without 
clearance in the axial direction in said recess 32. The bearing bushing 20 
is thereby seated with a snap fit in the recess 32, such that the sleeve 
18 and the bearing bushing 20 are connected releasably, but still fixedly 
to one another. This type of connection is substantially less expensive 
than a connection which is for example created by vulcanization. 
During installation it is possible to insert the bearing bushing 20 into 
the sleeve 18 by elastic bending of such sleeve 18, with the parts 18 and 
20 still outside of the cylinder head 10. Thereafter, the mechanism 14 
formed by these two parts 18 and 20 is introduced into the through opening 
12 of the cylinder head. Fastening of the mechanism 14 in the cylinder 
head 10 can take place in various ways, for example with the help of 
fastening plates 40, 41 shown in broken lines and placed from both ends 
onto the cylinder head 10 and which radially project into overlapping 
relation with the sleeve 18 and fix same axially of the cylinder head 10. 
FIG. 2 illustrates in a fragmentary view a modification of the piston rod 
support. The only difference from the embodiment of FIG. 1 is that the 
sleeve 18a does not have end sections formed in one piece thereon. Rather, 
separate seals 42, 44 are provided which have approximately the same 
design as the end sections 22, 24 of the sleeve 18 of FIG. 1. 
Although a particular preferred embodiment of the invention has been 
disclosed in detail for illustrative purposes, it will be recognized that 
variations or modifications of the disclosed apparatus, including the 
rearrangement of parts, lie within the scope of the present invention.