Multistage side channel compressor

An improved side channel compressor wherein the compressor comprises first and second compressor stages each including first and second housing halves. In accordance with the invention, the inner housing halves (i.e., the second housing half of the first stage and the adjacently arranged first housing half of the second stage) are each provided with inlet and outlet openings of the same size and shape and with sealing rims surrounding these openings. In further accord with the invention, the second housing half of the first stage is provided with a further sealing rim arranged in the circumferential direction ahead of the outlet opening of that housing half and the first housing half with a further sealing rim arranged in the circumferential direction behind the inlet opening of that housing half. The further sealing rim of the second housing half is further arranged so that the distance between its center and the center of the outlet opening of that housing is equal to the distance between the centers of the rims surrounding the outlet and inlet openings of the housing half. Similarly, the further sealing rim of the first housing half is arranged so the distance between its center and the center of the inlet opening of that housing half is equal to the distance between the centers of the rims surrounding the inlet and outlet openings of the housing half.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a side channel compressor wherein the compressor 
comprises first and second compressor stages each including first and 
second housing halves axially arranged in side by side relationship and 
wherein the inner adjacently arranged housing halves of each stage include 
at least one inlet or outlet opening for forming a passage for connecting 
the stages. 
2. Description of the Prior Art 
A multistage side channel compressor of the above type is disclosed in U.S. 
Pat. No. 3,545,890. As above indicated, the inner housing halves of the 
compressor stages are each provided with only one inlet or outlet opening. 
The outlet opening of the inner housing half of one of the compressor 
stages, in turn, is connected to the inlet opening of the inner housing 
half of the other compressor stage via a passage opening provided in an 
intermediate element arranged between the two stages. In this manner, the 
two compressor stages are connected in series and the compressor is 
thereby capable of producing about twice the pressure at about the same 
output. If, on the other hand, a larger output at a lower pressure rather 
than at a higher pressure is required, the individual compressor stages 
have to be connected in parallel. Such a parallel connection, however, is 
not possible in the above described known side channel compressor. 
Another type of a side channel compressor is also known in which separate 
deflecting devices are mounted at the inlet and outlet openings of the 
individual compressor stages, for deflecting the flow so as to effect 
parallel or series connection of the individual stages. For modifying 
compressors which do not have the latter capability, the appropriate 
deflection devices must be bought and mounted as separate components. 
It is an object of the present invention to provide a side channel 
compressor having first and second compressor stages designed to permit 
series or parallel connection thereof as desired. 
SUMMARY OF THE INVENTION 
In accordance with the principles of the present invention, the above and 
other objectives are accomplished in a compressor of the above type by 
providing each inner housing half with inlet and outlet openings of the 
same shape and size and with sealing rims each in surrounding relationship 
with one of the inlet and outlet openings. Each inner housing half is 
further provided with an additional sealing rim, where the additional 
sealing rim in the inner housing half of the first compressor stage is 
arranged circumferentially ahead of the outlet opening of that stage, and 
the additional sealing rim in the inner housing half of the second 
compressor stage is arranged circumferentially behind the inlet opening of 
that housing half. Each additional rim is further arranged so that the 
distance between its center and the center of the sealing rim of the 
adjacent inlet or outlet opening of its respective housing half is equal 
to the distance between the centers of the sealing rims surrounding the 
inlet and outlet openings of that housing half. 
With the inner housing halves provided with such additional rims the first 
and second compressor stages can be shifted in the circumferential 
direction relative to each other. Thus, for parallel connection of the 
stages, the inlet openings of both inner housing halves are made to 
coincide as are the outlet openings of both housing halves. For series 
connection, however, the compressor stages are shifted relative to each 
other such that the outlet opening of one inner housing half coincides 
with the inlet opening of the other inner housing half, and the remaining 
inlet opening of the one half and outlet opening of the other half are 
covered by the additional sealing rims provided in the housing halves. 
In the embodiment of the invention to be disclosed hereinafter, the housing 
halves of each stage are further provided with connecting points uniformly 
distributed over their circumferences. In this embodiment, the sealing 
rims surrounding the inlet and outlet openings of each compressor stage 
are arranged so that the angle included between axes running from the 
centers of the rims to the center of the stage is equal to or a multiple 
of the angle included between axes running from two adjacent connecting 
points to the stage center. In a further aspect of the invention, the 
inner housing half of the first stage is provided with yet an additional 
sealing rim arranged circumferentially behind the inlet opening of that 
stage and the inner housing half of the second stage with still a further 
sealing rim arranged circumferentially ahead of the outlet opening of that 
stage. This permits shifting of the inner housing halves relative to one 
another in either direction.

DETAILED DESCRIPTION 
FIG. 1 shows a side channel compressor comprised of first and second 
compressor stages 1 and 2 arranged on a common shaft 3. The compressor 
stage 1 includes an outer housing half 4 and an inner housing half 5. 
Similarly, the compressor stage 2 includes an inner housing half 6 and an 
outer housing half 7. Supported within the housings of the stages 1 and 2 
are impellers 8 and 9, respectively. 
As can be seen in FIG. 2, the inner housing half 5 is provided with an 
inlet opening 10 and an outlet opening 11. The openings 10 and 11 are 
surrounded by sealing rims 12 and 13, respectively. The housing half 5 is 
also provided with a further sealing rim 14 arranged ahead of the outlet 
opening 11 and whose center is at a distance from the sealing rim 13 which 
is equal to the distance between the centers of the sealing rims 12 and 
13. Several connecting points 15 are also arranged around the 
circumference of the inner housing half 5; these points being spaced at a 
uniform distance from each other. As can be seen, each adjacent pair of 
connecting points 15 form an an angle .alpha. with the center 16 of the 
housing. Similarly, the axes through the housing center 16 and the centers 
of each two adjacent sealing rims 12 and 13 or 13 and 14 form an angle 
.beta.. As shown, the angles .alpha. and .beta. are equal. 
As shown in FIG. 3, the inner housing half 6 of the compressor stage 2 also 
is provided with inlet and outlet openings 16 and 17 and also with sealing 
rims 18 and 19, respectively, surrounding these openings. The inner 
housing half 6 furthermore is also provided with a further sealing rim 20 
which, in this case, is arranged behind the inlet opening 16. 
Inlet and outlet openings 21 and 22, respectively, are formed in the outer 
housing half 4 of the stage 1, while similar inlet and outlet openings 23 
and 24 are formed in the outer housing half 7 of the compressor stage 2. 
In FIGS 3 and 4 arrow lines 25 indicate the entrance path and arrow lines 
26 the exit path of the medium to be transported by the compressor. 
In FIG. 3, the housings of the compressor stages 1 and 2 are connected to 
each other so that the inlet opening 10 of the inner housing half 5 of the 
compressor stage 1 coincides with the inlet opening 16 of the inner 
housing half 6 of the compressor stage 2. Similarly, the outlet opening 11 
of the inner housing half 5 coincides with the outlet opening 17 of the 
inner housing half 6. With this type of connection, the two compressor 
stages 1 and 2 are connected in parallel. Hence, as indicated by the arrow 
lines 25, the medium to be transported can enter the compressor stages 
through both the inlet opening 21 and the inlet opening 23. Alternatively, 
one of the inlet openings 21 and 23 can be covered up by a cover so that 
the medium to be transported then enters via only one opening and finds 
its way into the other compressor stage via the inlet openings 10 and 16 
of the two inner housing halves 5 and 6. As indicated by arrow lines 26, 
the medium to be transported leaves the compressor stages via both the 
outlet openings 22 and 24. Here, again, in the alternative, the outlet 
opening of one of the compressor stages can be covered up or closed off. 
In such case, the medium to be transported then passes via the outlet 
openings 11 and 17 into the respective other compressor stage and leaves 
the side channel compressor via the outlet opening thereof. It should be 
noted that the inlet and outlet openings of the compressor stages may also 
be arranged in the compressor so as to extend radially as is indicated by 
the outlet opening 28 shown in FIGS. 3 and 4 in broken line. 
In FIG. 4, the two compressor stages 1 and 2 have been shifted or rotated 
in the circumferential direction relative to each other so as to connect 
the compressors in series. In particular, the compressor stages 1 and 2 
have been rotated relative to one another by the angle .alpha.. As the 
angles .alpha. and .beta. are equal such rotation causes the outlet 
opening 11 of the inner housing half 5 to now coincide with the inlet 
opening 16 of the inner housing half 6. The inlet opening 10 of the inner 
housing half 5, on the other hand, is covered by the further sealing rim 
20 of the inner housing half 6. Similarly, the outlet opening 17 of the 
inner housing half 6 is covered or closed off by the further sealing rim 
14 of the inner housing half 5. Additionally, the outlet opening 22 of the 
outer housing half 4 and the inlet opening 23 of the outer housing half 7 
have been closed off by means of covers. 
As indicated by arrow lines 27, the medium to be transported enters the 
side channel compressor through the inlet opening 21 in the outer housing 
half 4. After one revolution of the compressor stage 1, the medium passes 
into the compressor stage 2 via the outlet opening 11 and the inlet 
opening 16 in the inner housing halves 5 and 6. After another revolution 
in the compressor stage 2, the medium leaves the side channel compressor 
via the outlet opening 24 in the outer housing half 7. The medium, 
therefore, traverses the two compressor stages 1 and 2 sequentially and is 
thus compressed to a higher pressure. 
The first stage inner housing half illustrated in FIG. 5 has yet another 
sealing rim 14 arranged in the circumferential direction behind the inlet 
opening 10. This permits shifting of this housing half in either 
direction. A like modification of the inner housing half of the second 
stage with another sealing rim arranged ahead of the outlet opening of 
that stage will permit shifting of the inner housing halves relative to 
one another in either direction. 
As can be appreciated, with the present invention, parallel or series 
connection of the compressor stages 1 and 2 is accomplished by appropriate 
rotational arrangement of the stages. Moreover, since formation of the 
inlet and outlet openings as well as the further sealing rims of the inner 
housing halves occurs at the same time, there is no additional cost to the 
formation of the compressor. Furthermore, since no additional mechanisms 
are required for chaning from one mode to the other mode of operation, 
such a change-over is possible at any time.