A refrigerator-operated apparatus having a housing adapted to accept components to be cooled. The housing is connected to a refrigerator housing via a connecting pipe, and the refrigerator includes a refrigerator generator extending through the housing and the connecting pipe, and encompassing at least one refrigerator stage that carries the components to be cooled. The apparatus further includes a damping mechanism for inhibiting vibrations generated by the refrigerator from being transmitted to the housing. The damping mechanism includes a separation space dividing the refrigerator housing into first and second connecting sections, and an elastic connecting ring connecting the first section to the second section. In one embodiment, the connecting ring extends across the separation space and is surrounded by a cover tube. In a second embodiment, the connecting ring is secured directly to one of the connecting sections, and is secured to the other connecting section via an adaptor pipe. Detent structure may be provided between the adaptor pipe and one of the connecting sections to cause the connecting ring to be pre-stressed.

TECHNICAL FIELD 
The invention is directed to a refrigerator-operated apparatus such as a 
cryogenic pump, cryostat, or the like, including a housing that accepts 
the component parts to be cooled, a refrigerator housing, a connecting 
pipe connecting the component housing to the refrigerator housing, and 
damping apparatus inhibiting vibrations generated by the refrigerator from 
being transmitted to the component housing. 
BACKGROUND OF THE INVENTION 
Refrigerators can be defined as temperature-cooling machines in which 
thermal dynamic cyclic processes occur (see, for example, U.S. Pat. No. 
2,906,101). A "single-stage"refrigerator includes a single cylindrical 
work chamber encompassing a displacement member. The chamber is connected 
in alternation to high-pressure and low-pressure gas sources for 
predetermined periods, so that the desired thermal dynamic cyclic process 
(e.g., Stirling process or Gifford/McMahon process) occurs during 
reciprocation of the displacement member. As a consequence of this 
reciprocation, heat is withdrawn from a specific region of the work 
chamber. In two-stage refrigerators (having dual work chambers) employing 
such cyclic processes, temperatures down to about 10K can be generated 
using helium as a working gas in the work chamber. 
Two-stage refrigerators are often used to operate cryogenic pumps and 
cryostats. In such devices, the cryogenic pump or cryostat usually 
includes a housing that receives component parts to be cooled. The 
refrigerator includes a housing that is connected to the component housing 
using a connecting pipe. The refrigerator may further include a 
refrigerating generator having at least one cylindrical work chamber (two 
in the case of a two-stage refrigerator) with a displacement member 
oscillating therein. The refrigerating generator extends through the 
refrigerator housing and the connecting pipe, into the component housing. 
The portion (usually the cold end) of the refrigerating generator that 
extends into the component housing carries a plurality of pump surfaces. 
In a cryogenic pump operated with a two-stage refrigerator, the first, 
warmer refrigerator stage carries a pot-shaped pump surface that serves as 
a radiation shield for the pump surfaces of the second, colder stage. In 
the work chambers of the first and second refrigerator stages, the 
displacement members oscillate at a frequency that usually amounts to a 
few Hertz, for example 2 to 3 Hertz. This oscillation generates vibrations 
that may be transmitted from the refrigerator through the pump housing and 
eventually to a recipient connected to the pump housing. In many 
environments in which cryogenic pumps are commonly used (for example, in 
electron microscopes), such vibrations are particularly troublesome. 
It has therefore already been proposed to provide damping structure that 
prevents vibrations from the refrigerator from being transmitted through 
the pump housing to the recipient. German OS No. 36 90 477 and U.S. Pat. 
No. 4,363,217 disclose damping structure that includes bellows systems 
combined with various damping agents (for example elastomers, damping 
material surrounding the bellows, wire suspension systems, and magnetic 
fields). Damping mechanisms of the type disclosed in these publications 
are relatively technically complex, and require excessive amounts of 
space. 
European Application No. 19 426 discloses an apparatus in which a cryogenic 
pump is suspended from an associated recipient in a pendulum arrangement, 
using a spring bellows. This design, like those previously described, uses 
an expensive and delicate bellows. Furthermore, such an arrangement is 
ineffective when the displacement members of the refrigerator reciprocate 
or oscillate along the axis of distension of the spring bellows. 
It can thus be seen that there exists a need for a refrigerator operated 
apparatus of the type described in which the cryogenic pump housing is 
coupled to the refrigerator housing with a structure that includes a 
simple, yet efficient, damping mechanism. 
SUMMARY OF THE INVENTION 
The present invention provides a refrigerator operated apparatus that 
solves the shortcomings of previously known arrangements by providing, 
between the housing of the cryogenic pump and the refrigerator housing, a 
generally cylindrical member that is separated into two substantially 
coaxial connecting sections by a separation space. The separation can 
occur in the refrigerator housing itself, or in a connecting pipe between 
the pump housing and the refrigerator housing. The connecting sections are 
connected to one another using an elastic connecting ring. In such an 
arrangement, the connecting ring performs two primary functions: first, it 
functions as a damping element; second, it provides a vacuum-tight 
connection between the two connecting sections. The connecting ring may be 
formed from an elastomeric material such as perbunane, polyurethane, or 
rubber (either natural rubber or silicone rubber). The material, however, 
should be selected such that vibrations generated by the refrigerator are 
not transmitted to the pump housing. In other words, the elastomeric 
properties of the material chosen should be adapted to the mass of the 
vibrating system. 
Other objects and advantages of the present invention will become apparent 
upon reference to the accompanying description when taken in conjunction 
with the following drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a cryogenic pump 1 having a pump housing 2 that is attached to 
a two-stage refrigerator 3. The refrigerator 3 includes a first, warmer 
stage 4 and a second, colder stage 5. A pot-shaped pump surface or 
enclosure 6 is secured in thermally conductive contact with the first 
refrigerator stage 4. The enclosure 6, along with a baffle assembly 7, 
defines an interior space 8 of the cryogenic pump 1. A plurality of pump 
surfaces 9 are secured in thermally conductive contact with the second 
refrigerator stage 5, and are located in the interior 8 of the cryogenic 
pump 1. The pump housing 2 is provided with a flange 11 that forms an 
entrance aperture for the cryogenic pump 1, at which a recipient (not 
shown) may be connected. A valve (not shown) may be interposed between the 
pump and the recipient. 
During operation of the cryogenic pump 1, gases having relatively high 
boiling points agglomerate at the baffle 7 and the enclosure 6. Gases 
having lower boiling points (predominantly argon) and light gases 
(predominantly hydrogen) proceed through the baffle assembly 7 into the 
interior 8 of the cryogenic pump 1. The gases entering into the interior 8 
are agglomerated at the pump surfaces 9. 
The pump housing 2 is provided with a connecting pipe 12 that carries a 
flange 13. A cylindrical housing 14 of the refrigerator 3 includes a 
flange 15 that is secured in vacuum-tight engagement with the flange 13. 
The refrigerator stages 4 and 5 extend axially through the cylindrical 
refrigerator housing 14, through the connecting pipe 12, and into the 
interior 8 of the cryogenic pump 1. 
In the illustrated embodiment, a control assembly 16 is disposed 
immediately beneath the refrigerator stages 4 and 5. The control assembly 
16 serves to supply the work chambers with working gas in order to drive 
the respective displacement members 17, 18 of the refrigerator stages 4, 
5. The working gas may be supplied with a compressor (not shown). 
In the cryogenic pump 1 shown in FIG. 1, the housing 14 of the refrigerator 
3 is divided into housing sections 21 and 22 joined together by a 
connecting ring 23 made of elastomeric material. The sections 21 and 22 
are separated by a separation space 24 that occurs along the height of the 
first refrigerator stage 4. The annular connecting ring 23 is generally 
rectangular in cross section, and includes an inner annular surface that 
is connected to the sections 21, 22 by gluing or vulcanization. The outer 
surface of the connecting ring 23 is secured, also by gluing or 
vulcanization, to a cover tube 26. As a result of this arrangement, a 
"double-thrust" spring element is formed, and the ring 23 performs both 
damping and vacuum sealing functions. The vibrating unit of the cryogenic 
pump 1 (including, for example, refrigerator stages 4 and 5 of the 
refrigerator 3, the control assembly 16, the pump surfaces 6 and 8, and 
the baffle assembly 7) are vibrationally isolated from the housing section 
21 by the connecting ring 23. Consequently, vibrations generated by 
operation of the refrigerator 3 are inhibited from being transmitted to 
the pump housing 2 of the cryogenic pump 1. Alternatively, the connecting 
pipe 12 could be divided into two sections by a separation space 24, and 
provided with structure similar to connecting ring 23 and cover tube 26. 
The damping effect of the ring 23 depends upon certain characteristics of 
the ring itself. For example, the elasticity and damping effect of the 
ring depends on the material from which it is made, and the spring 
stiffness of the ring depends upon geometrical design. The damping effect 
of the connecting ring 23 also depends upon the mass of the vibrating 
portions of the cryogenic pump. The natural frequency of the vibrating 
unit is reduced by increasing the mass, and vibration transmission is 
minimized, given the equation: 
EQU (W/W.sub.c) .ltoreq.1 
where: 
W equals the frequency of the oscillating displacement members; and 
W.sub.c equals the natural frequency of the vibrating unit. 
For these reasons, it may therefore be advantageous to equip the vibrating 
unit of the pump with an auxiliary weight 25, as shown in FIG. 1. The 
auxiliary weight 25 is annular, and surrounds (but does not contact) the 
connecting ring 23 and the cover tube 26. The auxiliary weight 25 is 
supported on a flange 27 at a lower section 22 of the refrigerator housing 
14, and thus may be considered to be part of the vibrating unit of the 
cryogenic.pump 1. An auxiliary weight of this type is relatively space 
efficient, and is especially advantageous when the control assembly 16 for 
the cryogenic pump 1 is disposed at a location remote from the other pump 
components. 
In the embodiment shown in FIG. 2, the lower section 22 of the refrigerator 
housing 14 is provided with an outwardly extending annular disc 28 
adjacent the separation space 24. The annular disc 28 serves to secure the 
lower section 22 to an adaptor pipe 29 that concentrically surrounds the 
upper housing section 21 of the refrigerator housing 14. A connecting ring 
23 is disposed in an annular space 31 between the housing section 21 and 
the adaptor pipe 29. The connecting ring 23 is secured to the outer 
surface of the connecting section 21, and to the inner surface of the 
adaptor pipe 29, either by gluing or by vulcanization. During operation of 
the cryogenic pump, the connecting ring 23 is subjected to shearing 
forces. Optimal spring and damping properties of the connecting ring 23 
can be achieved with suitable selection of the ring material and ring 
height. 
When the cryogenic pump 1 is in an inoperative state, the connecting 
section 21 and the adaptor pipe 29 assume the relative positions shown in 
FIG. 2. In this position, a clamp ring 32 is provided on an inside groove 
33 on the inside of the adaptor pipe 29. Adjacent to the clamp ring 32, an 
annular disc 34 is secured (for example, by welding) to the outside 
surface of the connecting section 21. The contact between the clamp ring 
32 and the annular disc 34 limits the downward displacement of the 
vibrating unit of the cryogenic pump 1. Such displacement occurs due to 
the spring bias of the connecting ring 23 exerted in the direction of 
arrow 35. The clamp ring 32 and the annular disc 34 thereby pre-stress the 
connecting ring 23 at about 80 to 90% of the vacuum force accompanying 
complete evacuation of the refrigerator housing. 
During operation of the cryogenic pump 1, a vacuum is generated within the 
pump housing 2. When the force of the vacuum exceeds the pre-stress forces 
on the connecting ring 23, a gap forms between the clamp ring 32 and the 
annular disc 34. This gap is of sufficient width to prevent vibrations of 
the vibrating unit from causing the clamp ring and the annular disc to 
strike one another. Due to the pre-stressing of the connecting ring 23, 
the vacuum force required to separate the clamp ring 32 and the annular 
disc 34 is extremely small, and thus the connecting ring 23 may be 
fabricated from an extremely soft material. 
It may also be desirable to provide additional structure for damping 
vibrations. In order to be effective, such structure should be supported 
between the vibrating unit and stationary portions of the cryogenic pump. 
In the exemplary embodiment shown in FIG. 1, such additional damping 
structure is provided in the form of a ring 37. The ring 37 may be made 
from metal wool, and is shown between the stationary flange connection 
13/15, and the upper edge of the connecting ring 23. The ring 37 is 
structurally simple, takes up little space, and contributes to damping of 
vibrations. 
In the exemplary embodiment of FIG. 2, an essentially annular membrane 36 
is provided adjacent the underside of the connecting ring 23. The inside 
edge of the membrane 36 is secured to the connecting section 21, and the 
outer edge of the membrane 36 is secured to the adaptor pipe 29. The 
membrane 36 may be secured in place by welding, and serves to protect the 
elastomeric material of the connecting ring 32 against corrosive gases 
that may be present in the pump. 
Although the present invention has been described with reference to a 
specific embodiment, those of skill in the art will recognize that changes 
may be made thereto without departing from the scope and spirit of the 
invention as set forth in the appended claims.