Method for the manufacture of a control disc or a control shield for a liquid-ring machine

A first control disc or plate part of a liquid ring machine referred to herein as a bearing disc, is cast or, more particularly, burned-out of ordinary steel without an end face wall but having an outer circular edge and partitions within the circular outer edge. The outer circular edge and partitions of the bearing disc are ground off so that edges of a front side facing the liquid ring lie in one plane. This bearing disc is then welded to a second separately fabricated flat cover disc of alloy steel, into which cover disc, suction and pressure slots, an operating liquid passage, and a shaft opening have been previously formed, the alloy steel cover disc forming the end face wall of the bearing disc.

BACKGROUND OF THE INVENTION 
The invention relates to the field of manufacturing a control disc or a 
control plate for a liquid-ring machine and, more particularly, to the 
economical manufacture of such a control disc or plate for withstanding 
corrosive media. 
Electric machines known in the art as liquid ring machines generally are 
employed as pumps for a gaseous medium. A housing for such a pump 
surrounds a ring of rotating liquid which is caused to rotate by an 
eccentrically mounted vane wheel turned by a revolving shaft. The shaft, 
in turn, is supported at each end in an end bell having inlet and outlet 
ports for the gaseous medium to be pumped as well as at least one inlet 
for operating liquid which replenishes any liquid lost, for example, 
through evaporation into the pumped medium. Because of the eccentric 
mounting of the vane wheel, operating liquid on one side Of the vane wheel 
creates a suction zone in which zone the pumped gaseous medium is sucked 
into the pump by way of the inlet ports in the end bells. On the other 
side of the eccentrically mounted vane wheel, a pressure zone is created 
where the pumped gaseous medium is forced to exit the pump by way of the 
outlet ports in the end bells. 
Between the end bells and the vane wheel housing or comprising a part of 
the end bell itself is a control disc or plate which partitions the end 
bell into separate chambers for operating liquid and pumped gaseous medium 
as well as provides control openings for the entry and exit of both 
operating liquid and gaseous medium. The control disc is typically sealed 
with the end bell on one side and seals the housing on the other side. At 
the same time, the control disc is designed to comprise separate pressure 
and suction slots in an end face wall facing the liquid ring for the 
pumped gaseous medium, the pressure and suction slots being concentrically 
arranged outside a hub of the vane wheel. Also, an opening for operating 
liquid is typically arranged in the vicinity of the vane wheel hub so that 
the operating liquid further fulfills the function of a gap sealing liquid 
sealing the gap between the vane wheel hub and the control disc. 
In known methods of manufacture of such control discs, at least one of the 
two end bells is designed as including a side shield abutment with inlets 
and outlets for a medium to be transported as Well as with connections for 
supplying cooling and gap-sealing operating liquid. Also, between the side 
shield abutment and the housing, a control disc with suction and pressure 
slots on its end face (facing the liquid ring) as well as at least one 
passage for the operating liquid through the end face wall is provided, 
where the various openings in the end face wall Of the control disc facing 
the liquid ring are further in communication with chambers bounded between 
the side shield abutment and the control disc by means of partitions on 
the back of the control disc and/or in the side shield abutment of the end 
bell. 
It is further known from the manufacture of liquid-ring machines such as 
the Siemens type 2BB to combine the control disc and the side shield 
abutment to form a structural unit referred to hereinafter as a control 
plate. 
Both control discs and control plates are commonly cast of steel in 
expensive molds where the end face wall must be relatively thick because 
of the requirements of casting processes of present foundry technology. In 
addition, the outside surface of the end face wall facing the vane wheel 
must be machine planed smooth and the edges of the openings must be 
deburred and brought to accurate dimensions in order to obtain a uniform 
gap width between the end face wall and the vane edges of the vane wheel 
to permit a flow through the openings of the end face wall that is as 
undisturbed as possible. 
With more corrosive media, increased corrosion occurs when ordinary steel 
is employed for constructing the end face wall at the openings. Such 
corrosion leads to a premature, noticeable degradation of the efficiency 
of such machines because of increased gap losses and disturbed flow 
conditions through the openings in the end face wall. 
For such aggressive media, control discs made of substantially more 
expensive corrosion resistant steel alloys are known, either manufactured 
by a casting process or by burning-out the spaces and openings from a 
correspondingly thick-walled alloy steel plate, the latter method 
resulting in a considerable loss of expensive material. 
In cast control plates for withstanding a corrosive medium of the Siemens 
type 2BB, a relatively thin-walled alloy steel cover disc with preformed 
openings is typically screwed on to an end face wall of a pre-cast steel 
side shield abutment after a chip-removing machining of the outside 
surface of the end face wall and preforming a circular edge in the cover 
disc. Also, the space between the outer circumference of the end face wall 
and the circular edge of the cover disc is typically cast with hardenable 
casting resin so that no corrosive medium can get between the cover disc 
and the cast end face wall. 
With this Siemens control shield, the edges of the aligned openings in the 
end face wall and in the cover disc must be reworked together in a final 
operation. 
Thus, it is desirable to provide a method of manufacture of a control disc 
or a control plate for a liquid-ring machine for withstanding more 
corrosive media which results in a lower cost for material and a greater 
simplicity of manufacture and obtains practically the same service life 
for the control disc or plate obtained with the designs cast wholly of 
corrosion resistant steel alloy, or designs made using a burn out process. 
SUMMARY OF THE INVENTION 
A successful solution of the stated problem is possible through a 
manufacturing method according to the features of the present invention in 
a particularly simple Way, where the burning-out operation is of lower 
cost, especially since in the casting process as well as in the 
burning-out process, it is not necessary to cast an especially thick end 
face wall or to submit the disc or shield to an excessive burning-out 
operation. 
In particular, the method according to the present invention includes the 
steps of forming a bearing disc of ordinary steel having a circular edge 
and partitions within the perimeters of the circular edge including a 
circular support for the vane wheel shaft, grinding off a side of the 
bearing disc facing the liquid ring so that the circular edge and 
partitions lie in one plane, forming a flat plate cover disc of steel 
alloy with openings for the suction and pressure slots, the operating 
liquid passage and the vane wheel shaft, and welding the flat plate cover 
disc to the ground off side of the bearing disc such that the cover disc 
forms the end face wall of the thus fabricated control disc or plate. 
The manufacture of the control disc or plate is thus accomplished more 
simply and economically by a casting and burning-out method since the 
expenditures in previously known processes for providing a facing and 
chip-removing machining of the surface of the end face wall facing the 
liquid ring, for casting a circular edge with hardenable synthetic resin 
or for a final step of reworking all the openings after the end face wall 
and disc are aligned can be eliminated.

DETAILED DESCRIPTION OF THE DRAWINGS 
The following description of a double flow liquid-ring machine applies 
logically also to a single-flow design of such a machine. 
Referring to FIG. 1, a typical liquid ring machine is shown in accordance 
with teachings of the prior art for a double flow design. The housing 1 
with a vane wheel 2 arranged eccentrically therein is covered on both 
sides by a control disc 3 and each control disc is covered by a side 
shield abutment 4, in the depicted example, comprising a portion of an end 
bell. 
The vane wheel shaft, not shown, goes through a shaft opening 5 in each 
control disc 3 as well as through an opening in the side shield abutments 
and is supported at the ends in the two side shield abutments 4. The 
control discs 3 furthermore each have in their end face wall facing the 
liquid ring a suction and pressure slot 6 and 7, respectively, as well as 
a passage 8 for operating liquid. On their respective back sides facing 
the side shield abutments, partitions 9 are provided. The side shield 
abutments 4 each have an inlet and outlet 10, 11 for a medium as well as 
an inlet 12 for the operating liquid. Instead of the usual separate design 
shown of the control disc and adjacent end bell, a control plate of 
unitary design can also be provided. 
In the Siemens 2BB type cast structural control plate, not shown, a 
separate corrosion resistant steel alloy cover disc including suction and 
pressure slots and the operating-liquid passage is screwed on to an end 
face wall of a side shield abutment with correspondingly similar openings. 
Any unwanted gaps between the end face wall and the cover disc are sealed 
by casting resin. The following described method of manufacture may be 
applied in the manufacture of such a control plate as well as to the 
manufacture of a control disc. 
In FIGS. 2 and 3, a partial control disc 3 or plate cast of ordinary steel 
or, in particular, by being burned out without an end face wall formed by 
cover disc 13 according to the present invention is shown. The partial 
disc 3 may be hereinafter described as a bearing disc since it comprises 
partitions for chambers including a circular bearing partition for 
supporting the shaft of the vane wheel. A separately fabricated flat cover 
disc 13 made of corrosion resistant steel alloy is welded to a front side 
of the bearing disc facing the vane wheel as shown in a side view along a 
section III--III of FIG. 2 as depicted in FIG. 3. From FIG. 2, it can be 
seen that the relatively thin-walled cover disc 13 has punched, milled or 
burned-out openings (suction and pressure slots 6 and 7, respectively; 
operating liquid passage 8, and shaft opening 5). With respect to the 
bearing disc 3, the end faces 9A of the partitions 9 and end faces of the 
circular edge 3A are ground off on the front side to lie in one plane. 
Referring further to FIG. 3, it can be seen that end faces 9A of the 
partitions 9, and the end faces of the circular edge 3A of the control 
disc part 3 are then welded to the alloy steel cover disc 13. The shaping 
of the partitions 9 and thereby of the rear chambers in the end bell 
separated from each other is performed in a manner known per se, depending 
on the required operating conditions of the control disc or plate. The 
chambers formed by the partitions 9 are covered by the cover disc 13.