Sealing plug device for a refrigerant compressor

A removable sealing plug device for protecting the interior of a refrigerant compressor from dust, dirt, and corrosion during storage and/or transport of the compressor before it is assembled into a refrigerating system, including a plug element made of a rubber material and having a body portion suitable for being sealingly fitted in an inlet and/or outlet port of the compressor and a columnar head portion formed in an upper face of the body portion, and a base plate having a through-hole in which the columnar head of the plug element is press-fitted, the through-hole of the base plate being provided with sawtooth-like projections to non-removably hold the columnar portion of the plug element and secure it to the outer portion of the compressor, by using an existing threaded hole and a screw bolt, to hold the plug element between the base plate element and the outer circumference of the compressor. The plug element and the base plate of the sealing plug device are concurrently removed from the inlet port and/or outlet port of the compressor due to a tight engagement of the plug element and the base plate provided by the sawtooth-like projections.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to a refrigerant compressor and, 
more particularly, relates to a sealing plug device for tightly closing 
each of inlet and outlet ports of a refrigerant compressor so as to 
isolate the interior of the compressor from the atmosphere during either 
the storage of the compressors in a warehouse or the transporting of the 
compressors from e.g., the warehouse or the manufacturing factory to an 
automobile assembling site where the compressors are assembled in 
automobile refrigerating systems, for the purpose of protecting the 
interior of the compressor against corrosion, dirt and dust. 
2. Description of the Related Art 
Generally, refrigerant compressors are manufactured and assembled, as an 
important component of an automobile refrigerating system, in a compressor 
manufacturing factory. During the final stage of the assembly of 
respective compressors, each compressor is filled with lubricating oil 
used for lubricating the interior of the compressor during the operation 
of the compressor, and also preventing the interior of the compressor from 
being corroded. For example, as shown in FIG. 6, an inlet port 40a of the 
refrigerant compressor is formed in an outer portion of the compressor, 
i.e., a pipe connecting portion 40 to which suction and delivery pipes of 
a refrigerating system are connected. Therefore, after the filling of the 
lubricating oil into the interior of the compressor, the inlet port 40a of 
the compressor is covered with a cap member 50 made of a rubber to seal 
and isolate the interior of the compressor from the atmosphere. An outlet 
port (not shown in FIG. 6) of the compressor is also covered by a similar 
cap member or a plug member. Then, the compressors are transported from 
the manufacturing and assembling factory to an automobile manufacturing 
and assembling factory where each of the compressors is assembled in an 
automobile refrigerating system. Namely, during the assembly of the 
automobile refrigerating system, the compressor is connected to a 
condenser and an evaporator of the refrigerating system via the suction 
and delivery pipes, and pipe joints. Therefore, before assembling the 
compressor into the refrigerating system, the cap members 50 covering the 
inlet port and/or the outlet port must be removed so that the suction pipe 
can be connected to the inlet port 40a via the pipe connector. Similarly, 
the delivery pipe is connected to the outlet port of the compressor via 
the pipe connector after the removal of the cap from the outlet port. 
FIG. 7 illustrates a different conventional sealing device used for sealing 
a port of a refrigerating fluid flowing passage, which is disclosed in 
Japanese Examined Utility Model Publication (Kokoku) No. 4-10478 published 
on Mar. 16, 1992. In FIG. 7, a sealing member 62 includes a stem portion 
62a fitted in a mounting hole of a base plate 63, a sealing portion 62b 
arranged at an end of the stem portion 62a for closing a port end of the 
refrigerating fluid flowing passage 61 (a tapered portion of the port of 
the refrigerating fluid flowing passage) in a sealing condition, and a 
stop head portion 62c arranged at an opposite end of the stem portion 62a 
and formed as a large diameter portion capable of preventing the seal 
member 62 from coming out of the mounting hole of the base plate 63. When 
the seal member 62 is attached to a portion of a machine body in which the 
refrigerating fluid flowing passage 61 is formed, the base plate 63 having 
several through-holes 64 is fixed to the machine body by means of screws 
66 threadedly engaged, via the through-holes 64, into screw holes 65 bored 
in the machine body around the refrigerating fluid flowing passage 61. 
Nevertheless, the afore-described cap member 50 of the prior art is 
securely attached to the suction port 40a of the connecting portion 40 by 
using only the elasticity of the cap member 50 itself, and therefore, 
during the transportation of the compressor, the cap member 50 might be 
loosened due to vibration and shocks, and eventually might come out of the 
suction port 40a. Further, it often occurs that the compressors must be 
stocked in a store house before they are assembled in automobile 
refrigerating systems for a rather long time. Thus, when the compressors 
are stocked, they are filled with gas to protect the interior of each 
compressor from dust and dirt, and corrosion. The gas used for this 
purpose is either helium gas or nitrogen gas which is filled into the 
interior of the compressors after the respective compressors are evacuated 
so that the pressure of the gas is higher than the atmospheric pressure. 
Therefore, the high pressure of the gas may cause the loosening of the cap 
member 50, and allows the cap member 50 to come out of the suction port 
40a. 
Further, in the case of the afore-mentioned sealing device of JU-B-4-10478, 
prevention of the sealing member 62 from coming out of the mounting hole 
of the base plate 63 relies on only provision of a large-diameter-portion 
62c at the end of the stem portion 62a. When the assembly of the sealing 
member 62 and the base plate 63 should be removed from the machine body 60 
by unscrewing the screws 66 at the assembling site, since the shape of the 
tapered port of the refrigerating fluid passage 61 is very simple, the 
sealing portion 62b of the sealing member 62 can be easily disengaged from 
the tapered port. Nevertheless, if the sealing device of JU-B-4-10478 is 
applied to a refrigerant compressor for sealing an inlet and/or outlet 
port of a flange joint to which an external pipe is joined, the inlet and 
outlet ports of the flange joint are formed as bores having a generally 
complicated shape such as a multi-stage counter bores. Thus, the sealing 
portion 62b of the sealing member 62 once press-fitted in the inlet and/or 
outlet port cannot be easily removed. Therefore, the large-diameter 
portion 62c of the sealing member 62 might be unable to prevent the 
sealing member 62 from being separated from the base plate 63 when the 
assembly of the sealing member 62 and the base plate 63 is forcedly pulled 
away from the inlet and/or outlet port of the flange joint to disengage 
the sealing portion 62b from the port against a large frictional 
resistance. Thus, when the sealing device of JU-B-4-10478 is employed for 
sealing the inlet and/or outlet port of the flange joint of the 
refrigerant compressor, the diameter of the large-diameter portion 62c 
must be increased. However, an increase in the diameter of the 
large-diameter portion 62c of the sealing member 62 will make it difficult 
or impossible to mount the stem portion 62a of the sealing member 62 in 
the mounting bore of the base plate 63 even if the large-diameter portion 
62c is made of an elastic material so that the portion 62c is elastically 
shrunk. 
SUMMARY OF THE INVENTION 
Therefore, an object of the present invention is to provide a sealing plug 
device, for a refrigerant compressor, having a reliable sealing 
performance able to surely close an inlet and/or outlet port of the 
refrigerant compressor and a dismounting performance allowing easy 
dismounting from the compressor without breakage. 
Another object of the present invention is to provide a sealing plug device 
for a refrigerant compressor, formed as an assembly of a base element 
permitting the assembly to be firmly attached to a joint portion of the 
compressor, and a reliably plug element easily mounted on the base plate 
with an ability of strongly preventing itself from coming out of the base 
plate during the dismounting of the assembly from the compressor, and 
exhibiting a reliable sealing performance. 
In accordance with the present invention, there is provided a sealing plug 
device for fluid-tightly closing at least one of inlet and outlet ports of 
a refrigerant compressor in which the inlet and outlet ports for 
refrigerant are formed in an outer part of the compressor so as to be 
connectable to suction and delivery pipes via pipe joints, the outer 
portion of the compressor being further provided with threaded holes 
formed at respective positions adjacent to the inlet and outlet ports so 
as to be used for fixing the pipe joints, the sealing plug device 
protecting the interior of the compressor from dust, dirt and corrosion, 
and comprising: 
a plug element made of rubber material and including a body portion adapted 
to being tightly fitted in at least one of the inlet and outlet ports, and 
a columnar head formed in an upper surface of the body portion to be 
vertically projected from the upper surface; and 
a base plate element adapted for being mounted on the plug element to 
secure the plug element to the outer portion of the compressor by using 
one of the threaded holes, the base plate having a through-hole in which 
the columnar head of the plug element is fitted, 
wherein the through-hole of the base plate has a substantially cylindrical 
inner wall in which at least one substantially circular inward projection 
is formed to include a circularly extending innermost end having an inner 
diameter smaller than an outer diameter of the columnar head of the plug 
element, the circular projection further including a face portion tightly 
engageable with the columnar head when the columnar head is forcedly 
fitted in the through-hole in a predetermined direction to thereby prevent 
the columnar head from moving in a direction reverse to the predetermined 
direction, and an adjacent rear portion permitting the columnar head to be 
smoothly moved into the through-hole, the face portion and rear portion 
forming therebetween the innermost end of the circular projection. 
Preferably, the through-hole of the base plate has a plurality of 
substantially circular inward projections formed in the cylindrical inner 
wall of the through-hole, and the circular projections are arranged one 
after another in a direction corresponding to the predetermined direction 
and provided with respective circular innermost ends having an identical 
inner diameter smaller than the outer diameter of the columnar head of the 
plug element. Each of the circular projections includes the face portion 
tightly engageable with the columnar head when the columnar head is 
forcedly fitted in the through-hole in the predetermined direction, to 
thereby prevent the columnar head from moving in the direction reverse to 
the predetermined direction, and the adjacent rear portion permitting the 
columnar head to be smoothly moved into the through-hole, the face portion 
and rear portion forming therebetween the innermost end of each circular 
projection. 
Preferably, the circular inward projection of the through-hole of the base 
plate is formed as a single sawtooth-like projection having the face 
portion formed to extend substantially perpendicularly to a central axis 
of the through-hole, and the rear portion formed as an inclined surface 
portion with respect to the central axis of the through-hole, an 
inclination of the rear portion being selected so as to permit the 
columnar head of the plug element to be smoothly moved into the 
through-hole of the base plate. 
Further, the plurality of circular projections of the through-hole of the 
base plate may preferably comprise a plurality of sawtooth-like parallel 
projections arranged one after another in the predetermined direction, and 
each of the sawtooth-like parallel projections has the face portion formed 
to extend substantially perpendicularly to a central axis of the 
through-hole and the rear portion formed as an inclined surface portion 
with respect to the central axis of the through-hole, an inclination of 
the rear portion being selected so as to permit the columnar head of the 
plug element to be smoothly moved into the through-hole of the base plate. 
Alternatively, the plurality of circular projections of the through-hole of 
the base plate may comprise sawtooth-like threads formed by a projection 
extending spirally and continuously around a central axis of the 
through-hole of the base plate, each of the sawtooth-like threads has the 
face portion formed to extend substantially perpendicularly to the central 
axis of the through-hole and the rear portion formed as an inclined 
surface portion with respect to the central axis of the through-hole, an 
inclination of the rear portion being selected so as to permit the 
columnar head of the plug element to be smoothly moved into the 
through-hole of the base plate. 
Preferably, the columnar portion of the plug element is provided with a 
tapered end formed at a top thereof for permitting the columnar portion of 
the plug element to be brought into a registration with the through-hole 
of the base plate when the plug element is mounted in the base plate.

THE DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1, a refrigerant compressor 100 is provided with a 
housing assembly including a cylinder block, a front housing, and a rear 
housing. The housing assembly forms an outer framework of the refrigerant 
compressor and is provided with a compression mechanism therein for 
sucking and compressing a refrigerant gas within cylinder bores when the 
refrigerant gas returns from an external refrigerating system via a 
suction pipe. The compressed refrigerant gas is discharged by the 
compressing mechanism into a discharge chamber within the housing 
assembly, and is then delivered toward an external refrigerating system 
via a delivery pipe. The housing assembly is further provided with an 
outer portion formed as a pipe connecting portion 1 to which the suction 
pipe and the delivery pipe (not shown) of the refrigerating system, e.g., 
an automobile refrigerating system are connected. The connecting portion 1 
has a mount 1a in which an inlet port 2 and a delivery port 2' are opened. 
The inlet and delivery ports 2 and 2' are arranged for being connected to 
the suction and delivery pipes via respective pipe joints to introduce a 
refrigerant gas for compression from, and to deliver the compressed 
refrigerant gas to, the external refrigerating system. The respective pipe 
joints are secured to the mount 1a by suitable screw bolts (not shown) 
threadedly engaged in threaded holes 3 formed in the mount 1a and arranged 
adjacent to the inlet and delivery ports 2 and 2'. 
Description of a sealing plug device according to an embodiment of the 
present invention will be provided hereinbelow. However, it should be 
generally understood that a sealing plug device according to the present 
invention may be used for sealingly closing either one of the inlet and 
outlet ports 2 and 2' of the refrigerant compressor 100 or both of the 
ports 2 and 2' in order to protect the interior of the compressor from 
dust, dirt and corrosion before it is assembled into a refrigerating 
system. 
FIGS. 2 through 5 illustrate one typical case where the sealing plug device 
according to the first embodiment of the present invention is used for 
closing the inlet port 2 of the refrigerant compressor 100. 
Referring to FIGS. 2 through 5, the sealing plug device includes a plug 
element 10 made of rubber material. The plug element 10 is provided with a 
body portion 11 in the shape of a cylindrical bulge capable of being 
tightly fitted in the inlet port 2, and a columnar head portion 12 
projecting from an upper face of the body portion 11. The columnar head 
portion 12 has a tapered end 12a formed at its uppermost end. 
As best shown in FIG. 3, the suction port 2 formed as a flange port is 
provided with a multi-step counter bore having at least a first uppermost 
shallow counter bore portion 2a in which a cylindrical base portion of the 
pipe joint is fitted, a second deep counter bore portion 2b in which a 
sealing element of the pipe joint is closely seated, and a third deeper 
counter portion 2c in which a cylindrical end of the pipe joint is fitted. 
The first through third counter bore portions 2a through 2c are chamfered 
at their lowest corners, respectively. It should be noted that the inlet 
port 2 of the pipe connecting portion 1 is sealingly closed by the plug 
element 10 of the sealing plug device when the body portion 11 is tightly 
fitted in the second counter bore 2b. Thus, an innermost end portion 11a 
of the body portion 11 which has a smaller diameter, as shown in FIG. 5, 
is formed as a supplemental support portion having no sealing function. 
The sealing plug device of the first embodiment further includes a base 
plate 20 cooperating with the above-mentioned plug element 10. The base 
plate 20 is provided with a cylindrical boss 21 formed so as to be fitted 
in the first uppermost counter bore 2a of the port 2 of the pipe 
connecting portion 1 and a mounting bore 16 through which a screw bolt 15 
is threadedly engaged in one of the threaded holes 3 of the pipe 
connecting portion 1 to fix the base plate 20 to the pipe connecting 
portion 1. The base plate 20 is further provided with a through-hole 13 
formed to be coaxial with the cylindrical boss 21 and having a chamfered 
open end formed in the cylindrical boss portion 21 and an opposite 
counter-bored open end. The through-hole 13 is provided for receiving the 
columnar head portion 12 of the plug element 10 so that the columnar head 
portion 12 is press-fitted or interference-fitted in the through-hole 13 
when the plug element 10 is forcedly inserted into the through-hole 13 so 
that the same element 10 is moved from the chamfered end of the 
through-hole 13 toward the counter bore end of the through-hole 13. The 
through-hole 13 of the base plate 20 has a bore diameter which is smaller 
than an outer diameter of the columnar head portion 12 of the plug element 
10 before the same element 10 is fitted in the through-hole 13. Thus, the 
columnar head portion 12 of the plug element 10 can be elastically 
deformed and press-fitted in the through-hole 13 of the base plate 20. 
Further, the inner cylindrical wall of the through-hole 13 of the base 
plate is provided with one or more inward projections 14 typically formed 
as one or more saw teeth in which each tooth has a face portion 14a 
extending substantially perpendicularly to a central axis of the 
through-hole 13, a rear portion 14b arranged to be inclined with respect 
to the same central axis of the through-hole 13, and a gullet 14c 
extending between the rear portion 14b and a neighboring face edge 14a. 
When a plurality of projections 14 are arranged in the inner cylindrical 
wall of the through-hole 13, the projections 14 may be either circularly 
extending saw teeth arranged to be parallel with one another or spirally 
and continuously extending sawtooth-like threads which may be more easily 
formed by the use of a screw lathe. 
As is understood from the enlarged cross-sectional view of the projections 
14 of FIG. 4B, the face portion 14a of each projection 14 functions to be 
firmly engaged with the columnar head portion 12 of the plug element 10 
when the latter element 10 is press-fitted in the through-hole 13 so as to 
prevent the columnar head portion 12 from loosening and coming out of the 
through-hole 13 even if a strong pulling force is applied to the plug 
element 10 press-fitted in the base plate 20. Further, the inclined rear 
portion 14b of the projection 14 of the through-hole 13 has a function 
permitting the columnar head portion 12 of the plug element 10 to be 
smoothly moved into the through-hole 13 of the base plate 20 along an 
arrow "p" in FIG. 4B. 
When the sealing plug device according to the embodiment of the present 
invention is assembled before it is attached to the inlet port 2 of the 
mount 1a of the refrigerant compressor, the tapered end 12a of the 
columnar head portion 12 of the plug element 10 is initially brought into 
registration with the chamfered open end of the through-hole 13 of the 
base plate 20, and the columnar head portion 12 is subsequently 
press-fitted into the through-hole 13. The tapered end 12a of the columnar 
head portion 12 is effective for centering the columnar head portion 12 
with the through-hole 13, so that the press-fitting of the plug element 10 
in the base plate 20 can be made easy and sure in response to an elastic 
reduction in the outer diameter of the columnar head portion 12. 
When the assembly of the plug element 10 and the base plate 20 is 
completed, the sealing-plug device is sealingly attached to the compressor 
100 by press-fitting the body portion 11 of the plug element 10 in the 
inlet port 2 of the compressor 100 in which a suitable amount of 
lubricating oil is supplied. At this stage, the mounting bore 16 of the 
base plate 20 is appropriately brought into registration with the threaded 
hole 3 of the mount 1a, so that the screw bolt 15 can be threadedly 
engaged in the threaded hole 3. Subsequently, the body portion 11 of the 
plug element 10 is press-fitted in the second counter bore 2b of the inlet 
port 2 of the mount 1a. At this stage, the cylindrical boss 21 of the base 
plate 20 is concurrently fitted in the first counter bore 2a of the inlet 
port 2, so that the lower face of the base plate 20 is closely seated on 
the upper face of the mount 1a of the pipe connecting portion 1. Then, the 
screw bolt 15 is threadedly engaged in the threaded hole 3 in order to 
tightly and stably fix the base plate 20 and the plug element 10 to the 
pipe connecting portion 1 of the compressor. Subsequently, a needle of the 
syringe (not shown) can pierce through the plug element 10 into the 
interior of the housing assembly of the compressor 100 and the evacuation 
of the interior of the housing assembly and the filling of a specific gas 
for protecting against corrosion of the interior of compressor 100 can be 
conducted. When the evacuation and filling of the specific gas are 
completed, the protection of the interior of the compressor against dust 
and dirt is also completed. 
The refrigerant compressors protected by the sealing plug device from the 
dust, dirt and corrosion are forwarded to either a subsequent stage of 
assembling the compressors into refrigerating systems or a warehouse, as 
stock, as required. 
When each of the compressors provided with the sealing plug devices is 
transported to the site of assembling it into a designated refrigerating 
system, the sealing plug device must be removed so that the suction and 
delivery pipes are connected to the inlet and outlet ports 2 and 2' of the 
compressor. The removal of the sealing plug device can be simply conducted 
by simultaneously pulling the base plate 20 together with the plug element 
10 from the inlet port 2 and/or the outlet port 2' of the compressor 100 
by using a suitable handle portion provided in a portion of the base plate 
20. Even if the quality of the rubber material of which the plug element 
10 is degraded so as to reduce an elasticity of the plug element 10 due to 
e.g., the storage in the warehouse for a long time, a tight engagement of 
the columnar head portion 12 of the plug element 10 with the projections 
14 of the through-hole 13 of the base plate 20 can surely prevent the plug 
element 10 from being separated from the base plate 20 during the removal 
of the sealing plug device from the mount 1a of the compressor 100. 
Consequently, the sealing plug device consisting of the assembly of the 
plug element 10 and the base plate 20 can be surely taken out of the pipe 
connecting portion 1 of the compressor 100. Then, the inlet and outlet 
ports 2 and 2' of the compressor from which the sealing plug device is 
removed are connected to the suction and delivery pipes by using the pipe 
joints. 
Various changes and modifications to the sealing plug device according to 
the described embodiment may be made by persons skilled in the art. For 
example, the cylindrical boss 21 of the base plate 20 may be omitted to 
form a flat bottom face of the base plate 20 if a corresponding boss 
portion is formed in the plug element 10 at a position between the base 
portion of the columnar head portion 12 and the body portion 11. 
From the foregoing description of the preferred embodiments of the present 
invention, it will be understood that, in accordance with the present 
invention, the sealing plug device for protecting the interior of a 
refrigerant compressor can be an easily and removably attached device and 
can surely and reliably seal the inlet and/or outlet port of the 
compressor without unpredictably being loosened and coming out of these 
ports even if vibrations and shocks are applied to the sealing plug device 
during the transportation of the refrigerant compressor.