Note: Descriptions are shown in the official language in which they were submitted.
~3~3S~7~
Description
BELLOWS SEAL
Technical Field
This invention relates to hermetic type seals for recipro-
cating shaft mechanisms.
The invention is of general utili-ty but of particular
utility in sterling engines and heat pump apparatus or systems
wherein loss of refrigerant vapor or system gas is to be avoided.
With the system operating or at rest, the high vapor pressure of
the refrigerant results in leakage through conventional shaft
seals. A diaphragm or a bellows seal avoids such leakage.
However, for example, the high pressure on the outer surface of
a thin flexible bellows, the interior of which is at ambient or
atmospheric pressure, in combination with ~he stresses caused by
the expansion and contractLon of the bellows, causes distortion
and rapid failure of the seal.
The present invention avoids this and other difficulties and
disadvantages by providing means for controlling the pressure
differential between the inside and outside of flexible seals,
such as the inside and outside of a bellows type of seal, and
by keeping maximum stress levels in each section caused by
expansion and contraction to a minimum by appropriate division
of the bellows and proper selection of the number of convolutions
in each section and appropriate seleceion of the driving means
for eaoh section, as will now be described.
In the drawing,
Figure 1 is a schematic longitudinal section taken at Sec-
tion 1-1 of Figures 2-4 showing one embodiment of the invention
as applied to the compressor mechanism of a heat pump,
Figures 2, 3 and 4 are partial sectional views taken at
sections 2-2, 3-3 and 4-4 of Figure 1,
Figure 5 is a partial sectional elevation at Section 5-5 of
Figure 4,
:
~3~3~t~j~
Figure 6 is a schematic longitudinal section of a
second embodiment of the invention taken at Section 6-6 of
Figure 8,
Figure 7 represents Section 7-7 of Figure 8,
Figure 8 represents Section 8-8 of the structure
of Figure 5 6,
Figure 9 is a schematic longitudinal section of
another embodiment of the invention,
Figure 10 is a section taken at line 10-10 of
Figure 9,
Figure 11 is a section taken along line 11-11 ln
Figure 9,
Figure 12 is a partial sectional view of a further
embodiment of the invention,
Figure 13 is a schematic view of another
embodiment,
Figure 14 is a sectional view taken along line 14-
14 in Figure 13,
Figure 15 is a sectional view taken along line 15-
15 in Figure 14, and Figure 16 is a fragmentary view of a
compressor piston having two shafts for driving auxiliary
pumps.
In Figures 1-5, piston 10 on shaft 11 operates
within a cylinder 12 in a housing section 9a and actuates a
sub-shaft 13 connected to a piston 14 of a sub-ambient or
vacuum pump 15. Bellows 16, within a chamber 17, is sealed
at its upper end to shaft 11 and at its l.ower end to a wall
extending between chamber 17 and housing wall ~b and forms
a hermetic seal between chamber 12b and the ambient
A ~ ~
~ ~3~3~
atmosphere in the bellows which through its open end, is
exposed to ambient pressure in housing section 9c. The
bellows operates concurrently with the shaft, which extends
through a gland type of seal lla in the wall 12c, the
maximum mechanical stress due to expansion and contraction
of the convolutions of the bellows are drastically reduced
by a lever and tube apparatus 18 in housing section 9c, as
described in my U.S. Patent No. 4,424,008.
Stresses normally introduced by diEferential
pressure are
-2a -
. .
~L3~35~
neutralized in accordance with one of the principles of this
invention, as will now be described.
The pu~lp 15 is connected to sub-ambient pressure or vacuum
chamber or chambers 19 through passageway or line 15a, valve 22
and a check valve 14a. Vacuum established during operation of the
the machine is maintained in chamber 19 during shutdown by
closing valve 22. The chamber 19 need be only large enough to
provide for the starting of the engine, as described hereinafter.
The pump needs only to have enough capacity to provide sufficient
10 vacuum to relieve excessive pressure in chamber 17 during oper-
ation of the engine and to quickly store a vacuum in chamber
19 for starting purposes in case the compressor is subject to
short periods of operation. A line 20 connects chamber 19 to a
sleeve or plunger valve 21. Valve 21 connects with the bellows
15 chamber 17 through a maniEold 23 and line 17a and with cylinder
chamber 12b through line 24 which is restricted by an orifice 25.
A plunger or piston 26, which has at least one bore 26a there-
through, is self-adjusting to variations in pressure around
bellows 16 through bore or bores 26a by a rod connection with a
20 control bellows 27 located in housing section 9b or 9c or in the
atmosphere.
During rest periods, piston 10 is forced to the expansion or
lower position by the pressure of the gas or refrigerant in
chamber 12a, and the bellows 16 is compressed and may be exposed
25 to full gas or vapor pressure, due to leaking by seal lla and
plunger 26. At startup, valve 22 is opened causing the pressure
around bellows 16 to be immediately reduced appro~imately to
ambient. During operation of the compressor, high pressure in
the bellows 27 causes the valve 21 to open line 20a to the vacuum
30 chamber, which is kept evacuated by the pump 15; low pressure
in bellows 27 conversely causes valve 21 to shut off or close
line 20a and connect chamber 17 through manifold 23, line 24 and
orifice 25 to the higher pressure chamber 12b, and the pressure
around bellows 16 is thus maintained substantially ambient.
The lines 15a and 20 in Figure 1 connect with the lines l5a
. ~ ,............. . .
~a3~3~
--4--
and 20 in Figure 5 and the valve 26 is illustrated as being in
its neutral position across both lines 20a and 24. In operation,
plunger or piston 26 will constantly move back and forth as the
bellows 27 responds to increases and decreases in pressure in
chamber 17. The pressure in 12b will always be somewhat higher
than ambient or atmospheric, inside of bellows 16 and housing
section 9c, due to vapor pressure of the refrigerant being
pumped, the principle use of the invention. However, the line
24 could be connec-ted to chamber 12a rather than chamber 12b.
While the primary function of the pump and vacuum chambers
is to relieve pressure in chamber 17 to approximately that in
the bellows, residual vacuum in the chambers 19 is also
useful in starting the engine/compressor. A line (not shown) to
chamber 12a frorn the vacuum chambers may be briefly opened to
lower the cylinder pressure and draw the piston 10 toward its
compressor top dead center position, which action also puts a
charge in the cylinder of the prime mover. The closing of the
line, thus allowing the vapor pressure in chamber 12a to build
up again, will aid in the return of piston lO back toward its
bottom dead center position, thereby compressing the charge
in the prime mover sufficiently for firing. Means may be pro-
vided to move the piston in either or both directions for
starting purposes, and a positive (soft) seal may be provided
around shafts ll and 13 and check valve 14c and line 24 to
prevent leakage when the compressor is at rest to reduce the
size or eliminate the need for chambers 19.
It will be seen that the entire apparatus may be self-
contained with vacuum pump, plunger valve and vacuum chambers
all located within the housing of the compressor which, however,
is of somewhat extended length in the form of Figures 1-5. A
more compact modification is shown in Figures 6-8. Here the
bellows 116 is sealed dlrectly to the piston 110 and to the
lower end wall 112c of the cylinder 112. The action of the
bellows is controlled by a lazytongs 130 of crossed links 130a,
130b and 130c, attached to a support ring 131, extending from
convolutions of the bellows. Crossed links 130a are normally
?3~7~1
long for large intervals and links 130c are short Eor shorter
intervals. ~acuum pump 115 evacuates vacuum chambers 119,
which may have connections through appropriate valves and lines
(not shown) to the cylinder 112 above and below piston 110 in a
manner and for purposes already described with respect to
Figures 1-6.
A second principle of the invention lies in having the
number of identical convolutions in each of a plurality of
sections of the bellows seal decrease sequentially from the
fixed end of the bellows to the movable end-thereof according to
the formula:
~2 = 52
NT ST
Where N2 is the number of convolutions in one of a plural-
ity of sections oE a bellows, NT :is the total number of identical
convolutions in the entire bellows, S2 is the amount of elon-
gation or contraction of the section, ST is the total elongationor contraction of the entire bellows during operation of the
machine in which the seal is used.
Another advantage of the system of Figures 6-~ lies in the
reduced diameter of the bellows, made possible by placing the
mechanism for actuating the intermediate portion or portions
of the bellows on the outside of the bellows.
Since the pressure on the outside and inside surfaces of
the bellows is regulated by the action of the plunger valve 21
to approximately ambient and since a significantly lower
pressure is maintained by the pump 115 in the vacuum chambers,
startup is easily accomplished as previously indicated.
; Another embodiment of the invention is shown in Figures
9-11. It has a bellows seal arrangement similar to that of
Figures 1-5 but having unequal length bellows sections 216a, 216b
and 216c with unequal length levers 230a, 230b and 230c for the
actuating mechanism between the piston rod and the cylinder.
The intermediate portions of the bellows are connected to
,
~3~3~7~
short guide sleeves 231 that are slidable on guide rods 232.
A still further embodiment of the inVentiOn is shown in
Figure 12 wherein bellows 316 is connected to the compressor
piston, and intermediate portions of the bellows are connected
to externally located driving links through short guide sleeves
around movable guide rods 332 connected to piston 310 on
opposite sides of the bellows. This provides a more compact
arrangement than in the modification of Figures 9~
The modification of Figures 13-15 makes use of a pair of
racks, one, 418, connected to piston 410 and the other9 419,
connected to intermediate portion 431 of the bellows 416 and
a large diameter gear 430a engaging rack 418 and an integral
or attached smaller diameter gear 430b engaging the rack 419.
This arrangement provides the same relative movements between
the bellows sections as in the other modifications.
Figure 16 shows how a compressor piston 510 may be designed
to actuate pump shafts 513 through a cylinder end wàll 512c
and seat on a soft pad 512d to prevent leakage through the
wall around the shafts and piston rod.
It is to be understood that other modifications of the
invention could have the ambient pressure on the outside of
the bellows seal with the inside being exposed to the variable
pressure and controlled in a similar manner. Also, in some
applications of the invention, it may be desirable to have
a differential in pressures other than ambient on opposite
sides of the bellows seal so long as they are controlled
p'essures.
: :~
: :
