Slide ring seal

A slide ring seal for sealing a gap between a rotatable and non-rotatable machine part. The seal comprises at least one static seal ring to be attached to the non-rotatable machine part and provided with a slide ring and at least one counter ring to be fastened to the rotatable machine part and provided with a slide ring. The static seal ring and the counter ring are thereby arranged to be fastened in such a way that the slide surfaces of the slide rings are tightly pressed against each other. In order to simplify the structure of the seal the counter ring and the static seal ring are mutually replaceable sealing modules.

BACKGROUND OF THE INVENTION 
The invention relates to a slide ring seal for sealing a gap between a 
rotatable and a non-rotatable machine part, comprising at least one static 
seal ring to be fastened to the non-rotatable machine part and provided 
with a slide ring and at least one counter ring to be attached to the 
rotatable machine part and provided with a slide ring, the static seal 
ring and the counter ring being arranged to be fastened so that the slide 
surfaces of the slide rings are pressed tightly against each other. 
Slide ring seals are known from various technical fields. They are used, 
e.g., in gearboxes, pumps and other such devices to prevent liquid from 
leaking from the contact points between a rotatable machine part and an 
immovable machine part. There are two types of axially sealing slide ring 
seals. Single-acting seals comprise two rings rotating with respect to 
each other, one of which is attached to and sealed on the rotatable 
machine part and the other is attached to and sealed on the immovable 
machine part. The rings are pressed into sealing contact with each other 
by means of slide surfaces formed thereon. In single-acting slide ring 
seals, the lubrication is wholly carried out by means of a liquid to be 
pumped, wherefore single-acting seals are not suited for use with liquids 
that contain mechanically wearing particles. In their simplest form, 
double-acting seals are formed by two single-acting seals which define 
therebetween a space into which a separate sealing liquid is introduced, 
mainly for lubricating the slide surfaces of the rings rotating with 
respect to each other. 
A disadvantage of prior known slide ring seals is that they are formed by 
several different parts, such as a body, a seal ring or seal rings, a 
counter ring or counter rings, a spring, springs or a bellow, auxiliary 
seals, etc. As a result of the great number of the requisite parts, the 
seal is complicated in structure, which complicates the storing of 
replacement parts, the production control and the assembly of the seals. 
Moreover, the complexity also often makes the seal unreliable, because, 
simultaneously as the number of parts increases, disturbances become more 
likely. 
Known solutions include the slide ring disclosed in Finnish Patent 
Specification No. 61,558. This known seal solution comprises eight 
separate and dissimilar parts, excluding O-rings, screws and springs, 
namely a counter ring, a seal ring, a body, another seal ring, another 
counter ring, a supporting ring, a press ring and a flange. In addition to 
these parts, at least 8 to 10 O-rings, 9 to 10 screws and 10 to 20 
separate springs are needed. Accordingly, 40 to 50 parts, of which 20 to 
30 are unlike, have to be handled during the assembly of the seal. 
Attempts have been made to achieve improvement in this matter by 
standardization, e.g. DIN 24960. Thereby, the counter rings, for instance, 
are made similar. The seal itself, however, may be very complicated. 
SUMMARY OF THE INVENTION 
The object of the invention is to provide a slide ring seal by means of 
which the disadvantages of the prior art can be eliminated. This is 
achieved by means of a slide ring seal according to the invention which is 
characterized in that the counter ring and the static seal ring are 
mutually replaceable sealing modules. 
The invention is advantageous mainly in that the number of the different 
parts comprised in the seal will be reduced as compared with prior 
solutions. Thereby, the storing of replacement parts, the production 
control, as well as the assembly, are essentially simplified as compared 
with prior solutions. The assembly can thereby be automated in an 
advantageous manner and the production costs can be reduced.

DETAILED DESCRIPTION 
FIG. 1 shows generally a slide ring seal intended for sealing a gap between 
a rotatable and non-rotatable machine part. For the sake of clarity, only 
the basic parts of the seal are shown in FIG. 1; accordingly, the 
non-rotatable machine part, such as the pump housing, and the rotatable 
machine part, such as the shaft, are not shown in the figure. 
The slide ring seal is formed of, e.g., two seal rings in a conventional 
way by attaching a counter ring to the rotatable machine part and a static 
seal ring to the non-rotatable machine part so that the slide surfaces of 
the counter ring and those of the slide rings provided in the seal ring 
are tightly pressed against each other. The counter ring thus rotates with 
the rotatable machine part, and the static seal ring stays in place with 
respect to the non-rotatable machine part. These matters are completely 
obvious to one skilled in the art, so they are not more closely discussed 
here. 
In the example of FIG. 1, the left-hand seal ring is arranged to act as a 
counter ring fitted on the rotatable machine part, and the right-hand seal 
ring correspondingly as a static seal ring to be fitted on the 
non-rotatable machine part. 
According to the invention, the counter ring and the seal ring are mutually 
replaceable sealing modules. As appears from FIG. 1, the basic parts of 
the module include a fastening element 1 for fastening the seal either to 
the shaft or in a sealing space according to DIN 24960, a resilient 
element 3, in the example of FIG. 1 a metal bellows and, a slide ring 4. 
In FIG. 1, the module is indicated generally by the letter M. 
As shown in FIG. 1, the modules M may be completely identical parts so that 
both modules M are resilient in the axial direction 
In addition to the basic parts of the modules M, O-rings 2 and 5 are shown 
in FIG. 1. When the module M is used as a counter ring to be fitted on the 
rotatable machine part, the O-ring 2 is positioned on the inner diameter 
of the module M. When the module M is used as a static seal ring to be 
fastened to the non-rotatable machine part, the O-ring 5 is positioned on 
the outer diameter of the module M. 
An advantage of this solution is that the same module M can be used both as 
a counter ring and as a static seal ring. 
The embodiment of FIG. 2 corresponds to that of FIG. 1. The only difference 
is that the resilient element 3' is formed by a rubber bellows. The module 
is indicated generally by the letter M' in FIG. 2. Apart from the 
resilient element 3' the module M' comprises a fastening element 1' and a 
slide ring 4'. The O-rings are indicated similarly as in FIG. 1. 
Different kinds of modules can be assembled from the modules M ,M' of the 
examples of FIG. 1 and 2 in various ways. FIG. 3 shows generally a 
double-acting slide ring seal when the modules M of FIG. 1 are used. The 
reference numerals of FIG. 3 correspond to those of FIG. 1. In FIG. 3, the 
reference numeral 6 further indicates a separate fastening module by means 
of which the module M can be fastened e.g. by means of a shaft or a 
separate sleeve. The reference numeral 7 indicates a fastening screw and 
the numeral 8 an O-ring which is fitted between the fastening module 6 and 
the module M. In FIG. 3, the reference numeral 9 indicates a stationary 
machine part, such as a part of the housing structure or the like, which 
is further provided with means for feeding a separate sealing liquid. 
The operation of the slide ring seal of FIG. 3 corresponds to the operation 
of the seal of Finnish Patent Specification No. 61,558. The O-rings and 
screws and the like excluded, parts of three types only are required in 
the seal according to the invention to form the modules M. Similarly 
excluding the O-rings, screws, etc., the solution of Finnish Patent 
Specification No. 61,558 requires eight different parts. 
The user and seller of the product, in particular, gain advantage from the 
small number of the different parts, because they can do with an extremely 
small store of replacement parts. Furthermore, repair operations can be 
carried out rapidly because of the simple replacement of a worn or damaged 
part with another. The manufacture, in turn, benefits from the module 
structure mainly in that it enables larger production series, thus 
reducing the production costs. 
FIG. 4 shows another embodiment in which a single-acting seal is assembled 
of the modules M. In addition to the sealing modules M, the figure shows 
generally a flange module 10. Accordingly, only two different modules are 
used in this example, i.e., the sealing module M and the flange module 10. 
The embodiments described above are by no means intended to restrict the 
invention, but the invention can, of course, be modified within the scope 
of the claims in various ways. Accordingly, it is apparent that the 
modules can likewise be formed in a manner different form that disclosed 
in the examples. Also, the number of the modules in the seal can be 
rapidly chosen as required.