U.S. patent application number 15/036612 was filed with the patent office on 2016-09-22 for cold header for cryogenic refrigerating machine.
The applicant listed for this patent is OERLIKON LEYBOLD VACUUM GMBH. Invention is credited to Holger Dietz, Gerhard Wilhelm Walter.
Application Number | 20160273809 15/036612 |
Document ID | / |
Family ID | 51900440 |
Filed Date | 2016-09-22 |
United States Patent
Application |
20160273809 |
Kind Code |
A1 |
Walter; Gerhard Wilhelm ; et
al. |
September 22, 2016 |
COLD HEADER FOR CRYOGENIC REFRIGERATING MACHINE
Abstract
A cold head for cryogenic machines comprises a displacer mounted
in a working chamber of a housing. The cold head also has a
high-pressure connection for supplying highly compressed
refrigerant and a low-pressure connection for discharging expanded
refrigerant. Also provided is a control valve arrangement for
controlling the supply and discharge of refrigerant. According to
the invention there is a bypass channel connecting the
high-pressure connection to the low-pressure connection.
Inventors: |
Walter; Gerhard Wilhelm;
(Kerpen, DE) ; Dietz; Holger; (Koeln, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
OERLIKON LEYBOLD VACUUM GMBH |
Koln |
|
DE |
|
|
Family ID: |
51900440 |
Appl. No.: |
15/036612 |
Filed: |
November 14, 2014 |
PCT Filed: |
November 14, 2014 |
PCT NO: |
PCT/EP2014/074623 |
371 Date: |
May 13, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F25B 9/14 20130101; F25B
2309/006 20130101 |
International
Class: |
F25B 9/14 20060101
F25B009/14 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 18, 2013 |
DE |
20 2013 010 352.3 |
Claims
1. Cold head for cryogenic refrigeration machines, comprising a
displacer mounted in a working chamber of a housing, a
high-pressure connection for supplying highly compressed
refrigerant into the working chamber, a low-pressure connection for
discharging expanded refrigerant from the working chamber, and a
control valve device for controlling the supply and discharge of
refrigerant into and from the working chamber, wherein a bypass
channel connecting the high-pressure connection to the low-pressure
connection.
2. Cold head for cryogenic refrigeration machines of claim 1,
wherein a throughflow regulation device is arranged in the bypass
channel.
3. Cold head for cryogenic refrigeration machines of claim 2,
wherein the throughflow regulation device is adjustable in
particular during operation.
4. Cold head for cryogenic refrigeration machines of claim 1,
further comprising a movement device for moving the displacer.
5. Cold head for cryogenic refrigeration machines of claim 4,
wherein the movement device is configured as a piston-cylinder unit
which, for actuation, is connected to the high-pressure connection
and the low-pressure connection.
6. Cold head for cryogenic refrigeration machines of claim 4,
wherein the movement device has a motor.
7. Cold head for cryogenic refrigeration machines of claim 14,
wherein the electric motor drives an eccentric that acts on a
slotted guide to cause a linear movement of the displacer.
8. Cold head for cryogenic refrigeration machines of claim 1,
wherein the control valve device has a cyclically operating,
multi-channel control valve that controls the connection of a
working chamber to a high-pressure connection and to a low-pressure
connection.
9. Cold head for cryogenic refrigeration machines of claim 8,
wherein the control valve controls the connection of the
piston-cylinder unit.
10. Cold head for cryogenic refrigeration machines of claim 1,
further comprising a distributor body in which at least a first
connecting channel is provided for connecting the high-pressure
connection to the working chamber.
11. Cold head for cryogenic refrigeration machines of claim 10,
wherein the first connecting channel is arranged between the
control valve and the working chamber.
12. Cold head for cryogenic refrigeration machines of claim 8,
wherein the distributor body has a second connecting channel
between the control valve and the low-pressure connection.
13. Cold head for cryogenic refrigeration machines of claim 10,
wherein the distributor body has a control channel for supplying
and/or discharging a control medium, in particular a refrigerant,
to and/or from the piston-cylinder unit.
14. Cold head for cryogenic refrigeration machines of claim 6,
wherein the motor is an electric motor.
Description
BACKGROUND
[0001] 1. Field of the Disclosure
[0002] The disclosure relates to a cold head for a cryogenic
refrigerating machine.
[0003] 2. Discussion of the Background Art
[0004] WO 94/29653 describes a cold head for a cryogenic
refrigerating machine, which is operated with helium as the working
gas and is connected to a high-pressure source and a low-pressure
source. The cold head includes a multi-channel control valve that
controls the respective connection of a high-pressure inlet and a
low-pressure inlet to a piston-cylinder unit and to a working
chamber of the cold finger on the warm side. At one of its ends,
the displacer which may include a regenerator, delimits a warm-side
working chamber and at the opposite end it delimits a cold-side
working chamber. While the displacer is periodically reciprocated
by the piston-cylinder unit, heat is constantly drawn from the
housing of the cold head. With a cold head having a single-stage
displacer, temperatures down to about 30 K can be generated. With
two- or three-stage displacers, temperatures below 1 K can be
generated. A thermodynamic cycle process (a Stirling process or a
Gifford-McMahon process) is performed in the cold head using
process gas, generally helium, the process gas being guided in a
closed circuit. As a consequence, heat is drawn from one end region
of the housing enclosing the displacer.
[0005] The cold head is connected to a compressor. Since the
circuit is a closed circuit, both the high-pressure connection and
the low-pressure connection of the cold head are connected to the
compressor. Such compressors typically include an overflow valve.
The same is arranged in a return flow conduit arranged between the
high-pressure side and the low-pressure side. Typically, overflow
valves are spring-loaded check valves generally designed for a
differential pressure between the high and low pressures of the
compressor of 18 bar, for example. When a cold head, whose
resistance is very high, is connected to the compressor the working
pressure increases excessively on the high-pressure side at the
compressor. For discharging this excess energy, the overflow valve
opens so that the refrigerant, in particular helium, flows to the
low-pressure side of the compressor via the return flow conduit.
Due to the cyclic process of the cold head, a pulsed gas supply
from the compressor to the cold head is realized. Here, gas
oscillations may occur. In particular over a longer period, this
may cause a frequent opening and closing of the overflow valve.
Thereby, the overflow valve is subjected to significant overload.
This may lead to damage to the valve seat of the overflow valve or
even to the destruction of the same. Further, this causes the
generation of significant noise and losses in performance. When an
overflow valve is damaged, it may happen that oil gets into the
refrigeration circuit. Another disadvantage is that performance
losses occur due to the existing hysteresis of the overflow valve
between the opening pressure and the closing pressure.
[0006] It is an object of the disclosure to reduce the load on the
overflow valve.
SUMMARY
[0007] The cold head for a cryogenic refrigerating machine of the
present disclosure has a working chamber in a housing, possibly a
multi-part housing. A single- or multi-stage displacer is arranged
in the working chamber. The cold head further comprises a
high-pressure connection for supplying highly compressed
refrigerant to the working chamber and a low-pressure connection
for discharging expanded or low pressure refrigerant. Further, a
control valve device is provided. The control valve device serves
to control the supply and discharge of refrigerant into and from
the working chamber. Here, the control device may comprise a
plurality of valves, for example an inlet valve and an outlet
valve. It is preferred that the control valve device has a
multi-channel control valve which controls the connection between
the high-pressure connection, the low-pressure connection and the
working chamber. According to the disclosure he cold head has a
bypass channel arranged between the high-pressure connection and
the low-pressure connection and connecting the two connections. If
needed, excess refrigerant can flow through said channel directly
from the high-pressure connection to the low-pressure connection
without flowing through the cold head. Such occurring surplus
energy can thus be discharged via the bypass. As a result, the
overflow valve integrated in the compressor is relieved. Possibly,
the overflow valve may be omitted altogether from the compressor or
it may be provided merely as a safety device. As a consequence, it
is possible at least to use a significantly less costly overflow
valve.
[0008] In a particularly preferred development of the disclosure a
throughflow regulation device is arranged in the bypass channel.
This may for example be a nozzle and/or a valve. The throughflow
regulation device may be adjustable. In this context it is possible
that a fixed setting is made prior to operation, so that the valve
opens for example when a pressure difference is exceeded. Further,
it is possible to allow for an adjustment of the throughflow
regulation device from outside, i.e. from outside the cold head. As
such, it may possibly be allowed to make corresponding adjustments
also during operation.
[0009] Since the present disclosure provides a bypass in the cold
head, which preferably includes a pressure regulation device, it is
possible to achieve a significant reduction of costs for the
compressors used. Further, the operating safety of the compressors
can be enhanced and the compressor performance can be increased.
The risk of an oil breakthrough caused by a damaged overflow valve
in the compressor is also reduced. Further, service life is
extended and a constant noise behavior can be achieved.
[0010] In a preferred development of the disclosure the cold head
has a movement device for moving the displacer. The movement device
may be a motor. By means of the motor, which may be an electric
motor, for example, the displacer can be moved using a slotted
guide. This may be effected e.g. through an eccentric so that the
rotational movement of the motor is converted into a longitudinal
movement of the displacer in a simple manner. As an alternative, a
piston/cylinder unit may be provided for moving the displacer. The
piston-cylinder unit may for example be driven via a separate
hydraulic system. However, for the purpose of movement, it is
preferred to connect the piston-cylinder unit to the high-pressure
connection and the low-pressure connection. In a preferred
embodiment, the actuation of the piston-cylinder unit and thus the
movement of the displacer are realized by means of the
refrigerant.
[0011] It is further preferred that the cold head has a distributor
body in which at least a first connecting channel is provided. The
first connecting channel serves to connect the high-pressure
connection to the working chamber. Preferably, this connection is
made via the control valve device so that the first connecting
channel is arranged between the control valve device and the
working chamber. Preferably, the distributor body additionally has
a second connecting channel arranged between the control valve
device and the low-pressure connection.
[0012] In a particularly preferred embodiment the valve body is
designed such that is also comprises a control channel. The control
channel serves to supply and discharge control medium to the
movement device, i.e. in particular to the piston-cylinder unit.
The control medium preferably is the refrigerant.
[0013] The disclosure will be explained in detail hereinafter with
reference to a preferred embodiment and to the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] In the Figures:
[0015] FIG. 1 is a schematic illustration of a cryogenic
refrigeration machine of the prior art,
[0016] FIG. 2 is a schematic illustration of a cryogenic
refrigeration machine of the present disclosure and
[0017] FIG. 3 is a schematic sectional view of an embodiment of a
cold head according to the present disclosure.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0018] A cryogenic refrigeration machine of the prior art (FIG. 1)
comprises a compressor 10 which compresses a refrigerant such as
helium. On the high-pressure side, the compressor 10 is connected
to a high-pressure connection 14 of a cold head 16 via a conduit
12. A low-pressure connection 18 of the cold head 16 is connected
to the low-pressure side of the compressor 10 via a conduit 20. To
avoid an overload on the compressor 10 a check valve 24 is arranged
in a return flow conduit 22 that connects the high-pressure side of
the compressor 10 to the low-pressure side of the compressor
10.
[0019] Inside the cold head 16 a working chamber 26 is provided in
which a displacer piston is arranged that is not illustrated in
FIG. 1. An inlet valve 28 is connected to the high-pressure
connection 14 so that compressed refrigerant flows into the working
chamber 26 when the inlet valve 28 is open. Expanded refrigerant
may be guided to the low-pressure connection 18 via an outlet valve
30.
[0020] In the basic configuration of a system of the present
disclosure illustrated in FIG. 2, similar and identical components
are identified by the same reference numerals.
[0021] According to the disclosure schematically illustrated a
bypass channel 32 is provided between the inlet valve 28 of the
cold head 16 and the outlet valve 30 of the cold head 16, in which
bypass channel a throughflow regulation device may possibly be
arranged. As shown in broken lines in FIG. 2, providing the bypass
channel 32 of the present disclosure makes it possible to omit the
return flow conduit 22 and the overflow valve 24.
[0022] A preferred embodiment of the cold head 16 is illustrated in
a schematic sectional view in FIG. 3.
[0023] The cold head 16 has a housing formed by the two housing
parts 34 and 36. In the housing part 34 two cylindrical cold-side
working chambers 38 and 40 are provided for the two displacer
stages 42 and 44.
[0024] The upper displacer stage 42 delimits a warm-side working
chamber 46 and is provided with a drive piston 48 arranged in a
cylinder 50 of a distributor body 52. Thus, the displacer 42, 44 is
arranged in a working chamber 38, 40, 46 formed by a plurality of
partial chambers.
[0025] The distributor body 52 delimits the warm-side working space
46. It is provided with bores that form a control channel 54, a
first connecting channel 56, as well as a second connecting channel
57. The first connecting channel 56 opens into the working chamber
46 and serves to supply working gas to this chamber. All three
channels are controlled by the control valve 58. The first
connecting channel 56 connects the control valve 58 to the
warm-side working chamber 46, the control channel 54 connects the
valve 58 to the cylinder 50 and the second 57 connects the vale 58
to a low-pressure connection 60. The control valve 58 is further
connected to a chamber 62 that is in communication with a
high-pressure connection 64. The high-pressure connection 64
supplies helium gas at a pressure of ca. 20 bar, while helium at a
pressure of about 5 bar prevails at the low-pressure connection 18.
Both pressures are supplied to corresponding connections (not
illustrated) of the control valve 58 via the chamber 62 and the
second connecting channel 57, respectively. All conduits lead into
the upper side of the distributor body 52 and from there to the
valve 58.
[0026] The housing part 36 accommodates a motor 66 that drives the
control valve 58 via a shaft 68. The valve is acted upon by a
compression spring 70.
[0027] In the embodiment illustrated the process gas subjected to
the thermodynamic cycle process and the drive gas for the
piston-cylinder unit 48, 50 are identical. Suitably, helium is
used. It is possible to use a different gas than the process gas as
the drive gas.
[0028] Instead of the piston-cylinder unit 48, 50 provided in the
embodiment illustrated for moving the displacers 72, 76, the
displacers 72, 76 may also be moved by a motor, e.g. using an
electric motor. For this purpose, the electric motor may be
provided with an eccentric and a slotted guide so that the rotation
of the eccentric is converted into a linear movement.
[0029] In the cylindrical working chamber 46, the displacer stage
42 has a tubular displacer 72 filled with a thermal regenerator 74
that is permeable to gas. The regenerator 74 serves to store cold
and to give off stored cold to the inflowing warm gas.
[0030] Similarly, the displacer stage 44 that has a smaller
diameter than the displacer stage 42, includes a tubular displacer
76 shiftable in the axial direction in the cylindrical working
chamber 40, said displacer being connected to the displacer 72 and
also being filled with a gas-permeable regenerator 78.
[0031] In operation of the cold finger, the working chamber 46 on
the warm side is first connected to the high-pressure connection 64
via the first connecting channel 56 and the control valve 58. At
the same time, high pressure is introduced into the cylinder 50
through the control channel 54. The displacers 72 and 76 are
shifted towards the cold side (downward). The gas under high
pressure flows through the regenerators 74 and 78 to the cold side
as well. In doing so it expands while cooling, with further
expansion being effected by heat exchange with the
regenerators.
[0032] In the second phase the control channel 54 is connected to
the low-pressure connection. Under the effect of the high pressure,
the displacers 72, 76 are shifted towards the warm side so that the
working chamber 46 on the warm side becomes smaller and gas flows
into the working chamber 40 on the cold side through the
regenerators 74 and 78.
[0033] In the third phase the control valve 58 causes the
connection of the working chamber 40 to the low-pressure connection
60 via the conduit 56. Thereby, the gas in all working chambers of
the cold head expands while cooling.
[0034] Thereafter the displacers 72 and 76 are moved to the cold
side, whereby the volume of the cold-side working chamber 40
shrinks so as to be prepared for the next cycle. In this phase the
cold gas flows from the working chamber 40 into the regenerators 74
and 78 which are thereby cooled further.
[0035] The frequency of the working cycle described is about 2
Hz.
[0036] Further, in the embodiment illustrated, a bypass channel 80
according to the disclosure is provided in the distributor body 52.
The bypass channel 80 connects the second control channel 57 to the
chamber 62. The bypass channel 80 thus connects the high-pressure
connection 64 to the low-pressure connection 60. As schematically
illustrated, a throughflow regulation device, such as a valve 82,
is arranged in the bypass channel 80. In case of an undesired high
pressure increase in the chamber 62, a part of the refrigerant thus
flows directly through the bypass channel 80 back into the channel
57 connected to the low-pressure connection 60.
* * * * *