Attachment mechanism for two-stage cold head

Abstract

An attachment mechanism for connecting a first-stage displacer of a two-stage cold head to a second-stage displacer of the two-stage cold head. The attachment mechanism includes a plug attachable to an end of the first-stage displacer. The plug includes a recess for receiving an end of the second-stage displacer. The attachment mechanism further includes a retaining device configured to be mounted at least partially around the end of the second-stage displacer and to retain the end of the second-stage displacer within the recess of the plug by engaging at least one formation extending from a radially outer surface of the second-stage displacer. The attachment mechanism further includes a device for securing the retaining device to the plug.

Description

Technical Field

[0001] The field of this invention relates to an attachment mechanism for connecting a first-stage displacer of a two-stage cold head to a second-stage displacer. Background Technology

[0002] A two-stage cold head (such as those used in Gifford McMahon refrigeration units) comprises a first-stage displacement device and a second-stage displacement device. Both the first-stage and second-stage displacement devices contain a refrigerant accumulator. The displacement device is configured to move within the housing to allow refrigerant to pass through the accumulator for cooling. An attachment mechanism is used to attach the second-stage displacement device to the first-stage displacement device.

[0003] Conventionally, a two-pin attachment mechanism has been used to connect a first-stage replacement to a second-stage replacement. The two-pin attachment mechanism includes a first pin received through a hole defined in the first-stage replacement, such that the first pin extends across the diameter of the first-stage replacement. A second pin of the attachment mechanism is received through a hole defined in the second-stage replacement, such that the second pin extends across the diameter of the second-stage replacement. An end of the second-stage replacement may be received within an end of the first-stage replacement, such that the first pin can pass through a hole defined in the second pin to lock the first-stage replacement to the second-stage replacement. US11156214 B2 discloses examples of two-pin attachment mechanisms as known in the prior art.

[0004] While conventional two-pin connector attachment mechanisms are simple and have a long lifespan, they occupy a large volume of space between the first and second stage displacer, where refrigerant (such as helium) flows. Therefore, the two-pin connector attachment mechanism contributes to hydraulic losses and results in a significant dead volume between the first and second displacer stages. Consequently, the efficiency of the two-stage cold head is reduced.

[0005] Providing an improved attachment mechanism for two-stage cooling heads would be beneficial. Summary of the Invention

[0006] According to one aspect, an attachment mechanism is provided for connecting a first-stage displacement device of a two-stage cold head to a second-stage displacement device of the two-stage cold head, the attachment mechanism comprising: a plug attachable to an end of the first-stage displacement device, the plug including a recess for receiving an end of the second-stage displacement device; a retaining device configured to be mounted at least partially around the end of the second-stage displacement device and retaining the end of the second-stage displacement device within the recess of the plug by engaging at least one formation extending from a radially outer surface of the second-stage displacement device; and a means for securing the retaining device to the plug.

[0007] This attachment mechanism can be advantageous because the retaining bracket can be mounted externally around the end of the second-stage displacer to attach the second-stage displacer to the plug. In this way, all components of the attachment mechanism are positioned radially outward of the second-stage displacer. In contrast, the two-pin connector includes two interlocking pins extending through the diameter of the second-stage displacer, which occupy space within the second-stage displacer and impede refrigerant flow, thereby reducing its efficiency. The proposed attachment mechanism removes this obstruction, thereby allowing improved refrigerant flow into the second-stage displacer. It also avoids occupying volume within the second-stage displacer, allowing more refrigerant accumulator material to be contained within it, where the interlocking pins would have previously been positioned. If more refrigerant accumulator is not desired, a more compact second-stage displacer can be provided without sacrificing performance.

[0008] In some embodiments, the retaining device includes a retaining ring. In this way, the retaining device can extend around the entire circumference of the second-stage displacer. This can help provide a uniformly distributed force to retain the second-stage displacer.

[0009] In some embodiments, the retaining device includes at least one pin, and wherein the retaining device and the plug each include at least one corresponding hole for receiving the at least one pin. This provides an easy-to-manufacture and cost-effective way to secure the retaining device to the plug.

[0010] In some embodiments, the at least one pin of the retaining device is secured to the retaining device and / or the plug by press-fit or by thread. For example, the retaining device may include at least one tenon configured to connect the retaining device to the plug. For example, the retaining device may include at least one screw.

[0011] In some embodiments, the retaining device includes adhesive. Adhesive eliminates the need for additional components for the attachment mechanism, thus providing a simple and effective way to secure the retaining device to the plug. Adhesive may be used in addition to another retaining device, such as the at least one pin.

[0012] In some embodiments, when the retaining device is secured to the plug, the at least one corresponding hole of the retaining device and the plug is aligned with a radial central axis defined by the plug. In some embodiments, the at least one corresponding hole of the retaining device and the plug extends substantially parallel to the axis. In this way, when the retaining device is secured to the plug, the at least one pin and the at least one corresponding hole are positioned axially rather than radially. In use in a cold head, they are aligned with an axis defined by a first and a second displacement device. This arrangement allows for a compact retaining device, in contrast to known two-pin joint mechanisms, which are positioned entirely around the exterior of the second-stage displacement device.

[0013] In some embodiments, the at least one pin includes a plurality of pins, and the at least one corresponding hole includes a plurality of corresponding holes. Having a plurality of pins provides a more secure connection.

[0014] In some embodiments, the plurality of corresponding holes are circumferentially spaced at equal intervals around the axis on the plug and the retaining device. In this way, the retaining devices are uniformly spaced around the second-stage displacement device.

[0015] In some embodiments, when the retaining device is secured to the plug, the retaining device is positioned within the recess of the plug. In use, this provides a compact attachment mechanism.

[0016] In some embodiments, the retaining device includes one or more through-holes to allow refrigerant used to cool the cold head to enter the recess of the plug. In this way, refrigerant flowing from the first-stage displacement device to the second-stage displacement device is allowed to flow through the retaining device.

[0017] In some embodiments, the one or more through-holes include a plurality of through-holes. This reduces obstruction to refrigerant flow, thereby improving displacement efficiency.

[0018] In some embodiments, the plurality of through-holes are circumferentially spaced at equal intervals around the retaining device. In this way, a uniformly distributed refrigerant flow can be provided around the ends of the second-stage displacer. This can improve the refrigerant flow to the second-stage displacer, thereby improving its efficiency.

[0019] In some embodiments, the attachment mechanism further includes a spacer configured to at least partially surround the end of the second-stage displacement device to space the end of the second-stage displacement device from the end surface of the recess of the plug. In this way, a space exists between the end surface of the recess of the plug and the end of the second-stage displacement device. This space allows refrigerant to flow smoothly into the second-stage displacement device in the axial direction.

[0020] In some embodiments, the spacer at least partially defines at least one channel configured to allow refrigerant for cooling the cold head to enter the region of the recess directly adjacent to the end of the second-stage displacer. In this way, the displacer's obstruction of refrigerant flow to the second-stage displacer can be reduced or minimized.

[0021] In some embodiments, the at least one channel includes multiple channels.

[0022] In some embodiments, the plurality of channels are circumferentially spaced at equal intervals around the spacer. This provides a uniformly distributed refrigerant flow from around the second-stage displacement device into the space created by the spacer.

[0023] In some embodiments, the at least one channel extends perpendicular to the axis.

[0024] In some embodiments, the spacer includes a first spring configured to mount around the end of the second-stage displacement device to bias the at least one forming portion away from the end surface of the recess of the plug. In this way, the spacer naturally includes a gap defining a channel for refrigerant flow, while providing a degree of flexibility to the joint between the first-stage and second-stage displacement devices. This flexibility allows for some axial offset between the axes of the first-stage and second-stage displacement devices. This flexibility also provides some axial degrees of freedom, allowing for axial compression of both the first-stage and second-stage displacement devices when the second-stage displacement device engages the end of the second cylinder of the cold head.

[0025] In some embodiments, the attachment mechanism includes a second spring configured to be mounted around the end of the second-stage displacement device to bias the retaining device away from the at least one forming portion. Having two springs on two sides of the at least one forming portion allows the second-stage displacement device to have some axial degree of freedom (if this is necessary for the operation of the cold head, for example, to help reduce vibration).

[0026] In some embodiments, the recess of the plug includes an inner bore for allowing refrigerant to pass between the ends of the first-stage displacer and the second-stage displacer. This inner bore allows refrigerant to pass directly between the first-stage and second-stage displacers in an axial direction. In some embodiments, the inner bore is defined through the end wall of the plug defining the recess. In some embodiments, the axial length of the plug is less than 5 mm, and in some embodiments, the axial length is less than 3 mm. In some embodiments, the axial length of the inner bore is less than 1 mm. In some embodiments, the end wall of the plug is less than 1 mm thick.

[0027] In some embodiments, the inner hole is defined in the end surface of the recess.

[0028] In some embodiments, the inner bore is located at the radial center of the plug.

[0029] In some embodiments, the attachment mechanism further includes a washer configured to mount around the end of the second-stage replacement. The washer may be configured to be positioned between the plug and the at least one formed portion. When the attachment mechanism includes a spacer, the washer may be configured to be positioned between the spacer and the at least one formed portion. The washer may help reduce wear on components of the attachment mechanism and / or the second-stage replacement.

[0030] In some embodiments, the gasket includes an angled surface adapted to correspond to the inclined surface of the at least one forming portion. In this way, the gasket can be adapted to adjust for any angled surface on the at least one forming portion, thereby enabling a robust engagement between the plug or spacer and the at least one forming portion.

[0031] According to another aspect, a two-stage cold head is provided, comprising: a first cylinder receiving a first-stage displacement device; and a second cylinder attached to an end of the first cylinder to receive a second-stage displacement device, the second-stage displacement device including at least one forming portion extending from a radially outer surface of the second-stage displacement device, wherein the first-stage displacement device and the second-stage displacement device each include a refrigerant accumulator and are configured to move within the first cylinder and the second cylinder respectively to allow refrigerant to pass through each of the refrigerant accumulators to cool the refrigerant, wherein the second-stage displacement device is attached to the first-stage displacement device by an attachment mechanism according to any of the preceding claims, the plug being attached to the end of the first-stage displacement device, and a retaining device being mounted and secured to the plug around the end of the second-stage displacement device such that it engages with the at least one forming portion to retain the end of the second-stage displacement device within the recess of the plug.

[0032] In this way, the cold head is equipped with an attachment mechanism in which no connector pin penetrates the displacer body and the helium flow path, thereby reducing dead volume and hydraulic losses. This attachment mechanism further allows the second-stage displacer to hold more refrigerant for a displacer of the same total length. Alternatively, if more refrigerant is not desired, the length of the displacer and the corresponding cylinder can be reduced, resulting in a more compact size while achieving the same performance.

[0033] In this type of cold head, the tolerances of the attachment mechanism allow for some axial alignment misalignment between the first and second displacement units. This is particularly relevant for horizontally operating two-stage cold heads, where the displacement units can have slight axial misalignment due to the weight acting on the displacement units perpendicular to the axis of the cold head.

[0034] In some embodiments, a portion of the plug defining the recess is received within the cavity of the first-stage displacement device. In this way, the axial space occupied by the attachment mechanism between the first-stage and second-stage displacement devices can be reduced, thereby providing a compact attachment mechanism.

[0035] In some embodiments, the plug is attached to the end of the first-stage displacement device by adhesive. This may be the only attachment device used, or it may be an attachment device other than at least one pin. Adhesive eliminates the need for additional components for the cold head, and thus provides a simple and effective way to attach the plug to the first-stage displacement device.

[0036] In some embodiments, the plug is attached to the end of the first-stage replacement device by at least one pin extending between a corresponding recess formed in the plug and the first-stage replacement device. This provides an easy-to-manufacture and cost-effective way to secure the plug to the first-stage replacement device.

[0037] In some embodiments, the at least one pin includes a plurality of pins, and the corresponding recess includes a plurality of corresponding recesses. The plurality of pins improves the connection between the plug and the first-stage displacement device.

[0038] In some embodiments, the at least one pin is press-fitted or threaded to the first-stage displacement device and / or the plug. For example, the securing device may include at least one tenon configured to connect the retaining device to the plug. For example, the securing device may include at least one screw.

[0039] In some embodiments, the at least one forming portion includes a forming portion that extends circumferentially around the end of the second-stage displacement device, either partially or completely.

[0040] In some embodiments, the at least one forming portion includes a plurality of forming portions.

[0041] In some embodiments, the at least one formed portion includes at least one protrusion integrally formed with the second-stage displacement device. Integrating the at least one formed portion simplifies the manufacturing process of the displacement device because it eliminates the need for additional parts or components.

[0042] In some embodiments, the at least one forming portion includes at least one pin extending from at least one corresponding recess or through-hole defined in the second-stage replacement device. In contrast to integrally formed forming portions, manufacturing forming portions using separate components allows for the retrofitting of forming portions onto existing replacement devices.

[0043] In some embodiments, the at least one pin is secured to the second-stage replacement device by press fit or by thread. For example, the at least one pin includes at least one tenon. For example, the at least one pin includes at least one screw.

[0044] In some embodiments, the at least one forming portion includes at least one screw extending from a through hole defined in the second-stage displacement device.

[0045] In some embodiments, the at least one forming portion comprises a rectangular cross-section or a truncated conical cross-section. Compared to a truncated conical cross-section, a rectangular cross-section is simpler to manufacture and allows for better engagement between the device and the forming portion. A truncated conical cross-section allows for a slight angle or offset between the axis of the first displacer and the axis of the second displacer. This can be particularly useful for cold heads configured for horizontal operation, in which the cold head may not be perfectly aligned with the first displacer under the weight of the second displacer.

[0046] In some embodiments, when the at least one forming portion includes a truncated conical cross section, the edge of the conical cross section of the at least one forming portion defines an angle between 0 degrees and 10 degrees with respect to the radial direction.

[0047] In some embodiments, the first-stage displacement device is configured to operate in an approximate temperature range of room temperature to 15 K. In some embodiments, the second-stage displacement device is configured to operate in an approximate temperature range of 20 K to 1 K.

[0048] In some embodiments, when the attachment mechanism includes the spring, the spring is mounted around the end of the second-stage displacement device between the at least one forming portion and the end surface of the recess of the plug to bias the second-stage displacement device away from the end surface of the recess of the plug. This can be a bias toward the cold end of the second cylinder. In some embodiments, when the attachment mechanism includes the second spring, the spring is mounted around the end of the second-stage displacement device between the at least one forming portion and the retaining device to bias the second-stage displacement device away from the end surface of the recess of the plug. This can be a bias toward the cold end of the second cylinder.

[0049] In some embodiments, the cold head further includes: a first demagnetized magnetic ring mounted rotatably around the end of the second stage displacement device and a second demagnetized magnetic ring mounted rotatably around the second cylinder, the first magnetic ring and the second magnetic ring being oriented such that the opposite magnetic poles of the first magnetic ring and the second magnetic ring are aligned; and an actuator configured to rotate the second magnetic ring.

[0050] According to another aspect, a Gifford-McMahon (GM) refrigeration unit is provided, which includes a cold head according to another aspect.

[0051] According to one aspect, a cryogenic pump, a utility tool for liquefying gases, or a utility tool for cooling a quantum computer is provided, comprising a GM refrigerator according to another aspect.

[0052] According to another aspect, a method is provided for attaching a first-stage displacement device of a two-stage cold head to a second-stage displacement device of the two-stage cold head using an attachment mechanism, the method comprising: attaching a plug of the attachment mechanism to an end of the first-stage displacement device; mounting a retaining device of the attachment mechanism around the end of the second-stage displacement device; and securing the retaining device to the plug using a device for securing the attachment mechanism such that the end of the second-stage displacement device is held within a recess of the plug, the retaining device engaging with at least one forming portion extending from a radially outer surface of the second-stage displacement device.

[0053] While this method can be implemented during the manufacturing of the cold head, it can also be implemented by retrofitting the attachment mechanism onto the first and second stage displacement devices of an existing cold head to provide the advantages discussed above in various aspects.

[0054] Further specific and preferred aspects are set forth in the appended independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims where appropriate, and in combinations other than those expressly stated in the claims.

[0055] When a device feature is described as operable to provide a function, it will be understood that this includes device features that provide that function or are adapted or configured to provide that function. Attached Figure Description

[0056] Embodiments of the invention will now be described further with reference to the accompanying drawings, in which: Figure 1 A cold head according to an embodiment is shown; Figure 2 An exploded view and an assembly view of a displacement device for a cold head including an attachment mechanism, according to an embodiment, are shown; Figure 3 It shows Figure 2 An enlarged view of the attachment mechanism; Figure 4 The cross-section of the plug in a plane perpendicular to the axis of the cold head is shown; Figure 5 The cross-section of the holding device in a plane perpendicular to the axis of the cold head is shown; Figure 6 An exploded view and an assembly view of a displacement device for a cold head including an attachment mechanism, according to an embodiment, are shown; Figure 7 It shows Figure 6 An enlarged view of the attachment mechanism; Figure 8 An exploded view, an assembly view, and a cross-section of a displacement device for a cold head including an attachment mechanism, according to an embodiment, are shown; Figure 9 It shows Figure 8 An enlarged view of the attachment mechanism; Figure 10 An exploded view, an assembly view, and a cross-section of a cold head displacement device including an attachment mechanism according to an embodiment are shown; Figure 11 It shows Figure 10 An enlarged view of the attachment mechanism; Figure 12 An attachment mechanism according to an embodiment is shown; Figure 13 The steps in the method according to an embodiment are illustrated. Detailed Implementation

[0057] Before discussing the embodiments in any further detail, an overview will first be provided.

[0058] Two-pin connectors are widely used coupling devices for linking a first-stage displacement device to a second-stage displacement device. In this connector, two pins are orthogonal to each other and allow movement within the connector along each pin in a plane perpendicular to the displacement device axis. Two-pin connectors have the following disadvantages: in the critical region of the connection between the cold head stages (where helium refrigerant flows between the two stages), the two-pin connector requires a relatively large working volume. Furthermore, the pins extend across and within the displacement device stages, thereby impeding refrigerant flow. Therefore, this type of connection contributes to hydraulic losses and results in an increase in dead volume between the first and second stages. Dead volume and hydraulic losses are known to reduce the efficiency of the cold head in GM refrigerators.

[0059] The embodiment provides a coupling device between subsequent stages in a two-stage cold head for a GM cryogenic refrigerator. This coupling device or attachment mechanism includes a plug configured to be disposed within a cavity at the end of a first-stage displacer. The plug includes a recess for receiving a second-stage displacer. A retaining device or retaining ring is configured to be mounted around the exterior of the second-stage displacer and secured to the plug. The retaining device engages a formation on the second-stage displacer to retain the second-stage displacer within the recess of the plug attached to the first-stage displacer, thereby coupling the second-stage displacer to the first-stage displacer. This configuration is configured to allow some lateral movement of the displacers relative to each other. In the proposed configuration, there are no joint parts in the main helium flow path between the first and second stages of the GM cryogenic refrigerator. Therefore, dead volume and hydraulic losses in this area can be reduced compared to a conventional two-pin joint. The space occupied by the pins can at least partially accommodate more regenerators. Therefore, for displacers of the same size, more regenerators can be contained within the displacer compared to a conventional displacer. If the amount of cold accumulator does not need to be increased, the length of the displacement device and the corresponding cylinder can be reduced while producing the same performance, thus allowing for a more compact cold head, which is advantageous for some applications.

[0060] Figure 1 A cross-section of a two-stage cold head 10 according to an embodiment is shown. The cold head 10 includes: a first cylinder 11 housing a first-stage displacement device 12; and a second cylinder 13 attached to the end of the first cylinder 11 housing a second-stage displacement device 14. The first-stage displacement device 12 and the second-stage displacement device 14 each include a refrigerant accumulator 15 and are configured to move within the first cylinder 11 and the second cylinder 13, respectively, to allow refrigerant to pass through the refrigerant accumulator 15 for cooling the refrigerant, as is known. A motor 18 is configured to drive the movement of the first-stage displacement device 12 and the second-stage displacement device 14. The second-stage displacement device 14 is attached to the first-stage displacement device 12 via an attachment mechanism 20 according to an embodiment.

[0061] Figure 2 and Figure 3 The attachment mechanism 20 is illustrated in more detail. For simplicity, the accumulator 15 and the first cylinder 11 and the second cylinder 13 have been omitted, but it should be assumed that in use, all the displacement devices shown in the figures are contained within the cold head housing (such as the first and second cylinders) and will be positioned similarly to... Figure 1 The displacement device shown is filled with a cold storage unit. Figure 2 and Figure 3 The left-hand view shows an exploded view of the cold head 10 including the attachment mechanism 20. The right-hand view shows the cold head 10 and the attachment mechanism 20 in an assembled state. The attachment mechanism 20 includes a plug 21, a retaining device 24, a spacer 27, and a device for securing the retaining device 24 to the plug 21.

[0062] The plug 21 may be attached to the end of the first-stage displacement device 12. In this embodiment, a portion of the plug 21, which defines a recess 22 for receiving the end of the second-stage displacement device 14, is received within the cavity 16 of the first-stage displacement device 14.

[0063] The plug 21 can be attached to the first-stage displacement device 12 by any suitable attachment device. For example, the plug 21 can be attached to the first-stage displacement device 12 by one or more pins 35 extending between corresponding recesses or holes formed in the plug 21 and the first-stage displacement device 12, such as... Figure 12 As shown in the diagram. The one or more pins may be press-fitted or threaded to the plug 21 and / or the first-stage displacement device 12. For example, a screw may be used to secure the plug 21 to the first-stage displacement device 12. Alternatively or additionally, the plug 21 may be glued to the first-stage displacement device 12.

[0064] The retaining device 24 includes a retaining ring configured to be externally mounted around the second-stage displacementr 14. During assembly, the retaining device 24 engages at least one formed portion 30 defined by the second-stage displacementr 14 to retain the second-stage displacementr 14 within a recess 22 of the plug 21. The retaining device 24 is secured to the plug 21 by a fixing device, for example, configured to connect the retaining device 24 to the plug 21. Figure 3 The pin 29 shown in the left-hand diagram is discussed below. It will be understood that one or more pins may be present. The one or more pins may be press-fitted or threaded to the plug 21 and / or retaining device 24. Alternatively or additionally, the retaining device 24 may be glued to the plug 21.

[0065] Figure 4 A cross-section of the plug 21 in a lateral plane (i.e., a plane perpendicular to the axis of the cold head 10) is shown. Holes 25a are configured to receive a corresponding one of the plurality of pins 29 to secure the retaining device 24 to the plug 21. These holes are evenly distributed circumferentially within the recess 22 around the plug 21.

[0066] The plug 21 further includes a radially centered inner bore 23 for allowing refrigerant to flow directly from the end of the first-stage displacementr 12 to the second-stage displacementr 14. The inner bore 23 is optional and is not included in some embodiments. In this case, during use, refrigerant can flow out of the first-stage displacementr 12 via orifices 17 circumferentially distributed around the end of the second-stage displacementr 14. The refrigerant then flows around the outside of the displacementr (but within the cylinders 11, 13) and into the second-stage displacementr 14 via the attachment mechanism 20, as if by… Figure 3As indicated by the arrow in the right-hand diagram. Specifically, the refrigerant flows through one or more axially oriented through-holes 26 defined in the retaining device 24, and then through one or more lateral channels 28 defined between the end surfaces of the recesses 22 of the spacer 27 and the plug 21, to reach the second-stage displacement device 14 and the accumulator 15 contained therein.

[0067] Figure 5 A cross-section of the retaining device 24 in a lateral plane (i.e., a plane perpendicular to the axis of the cold head 10) is shown. The retaining device 24 includes a hole 25b for receiving a pin 29. Thus, the pin extends from the hole 25b of the retaining device 24 to the hole 25a of the plug 21 to secure the retaining device 24 to the plug 21. In this embodiment, the hole 25b includes a countersunk hole to receive the head of a screw. It will be understood that this is optional. When the retaining device 24 is secured to the plug 21, the retaining device 24 is positioned within a recess 22 of the plug 21. In this way, a compact attachment mechanism can be provided.

[0068] The retaining device 24 further includes through holes 26 that allow refrigerant for cooling the cold head to approach the recess of the plug and subsequently approach the second-stage displacement device 14, as described above.

[0069] Return to Figure 2 and Figure 3 The attachment mechanism 20 includes a spacer 27. The spacer 27 includes an annular spacer configured to be mounted around the exterior of the second-stage displacementr 14, such that it is positioned between the plug 21 and a formation 30 formed on the second-stage displacementr 14. The spacer 27 maintains a gap between the end surface of the recess 22 of the plug 21 and the end of the second-stage displacementr 14, allowing refrigerant to flow between the plug 21 and the second-stage displacementr 14. The spacer 27, together with the end surface of the recess 22 of the plug 21, defines a plurality of channels 28 for allowing refrigerant to pass through the spacer 27, as described above.

[0070] In this embodiment, the forming portion 30 of the second-stage displacementr 14 includes a ring extending radially outward around the entire circumference of the second-stage displacementr and is integrally formed with the second-stage displacementr 14. The forming portion 30 has a rectangular cross-section. However, it will be understood that the forming portion 30 may vary in form. In some embodiments, the forming portion 30 includes a plurality of forming portions circumferentially distributed around the second-stage displacementr 14. In some embodiments, at least one forming portion is not integrally formed, as discussed in more detail below.

[0071] Figure 6 and Figure 7 The diagram illustrates the relationship between... Figure 2 and Figure 3A similar manner is used to connect the first-stage and second-stage displacement devices via an attachment mechanism, except that the forming portion 30b includes a truncated conical cross-section and the attachment mechanism includes a washer 31 positioned between the spacer 27 and the at least one forming portion 30. The washer 31 helps reduce wear on the spacer 27 and the forming portion 30. A second washer (not shown) may be disposed between the retaining device 24 and the forming portion 30b. It will be understood that in other embodiments (e.g., ...), ... Figure 2 and Figure 3 The gasket is implemented in the embodiment shown.

[0072] The truncated conical section may have sides inclined at up to 15 degrees, up to 10 degrees, or up to 5 degrees from a plane perpendicular to the axis of the displacer. The truncated conical section of the forming portion 30b allows for a slight misalignment between the axis of the second-stage displacer 14 and the axis defined by the first-stage displacer 12. In other words, if the second-stage displacer 14 is not perfectly parallel to the first stage, the inclined sides compensate for any tilt of the displacer. This allowance can be particularly helpful for cold heads configured for horizontal operation, as the weight of the displacer or other mounting components can cause misalignment between displacers. Alternatively, misalignment may be caused by manufacturing tolerances. In some embodiments, the axial end surfaces of the gaskets are not parallel. For example, the end surface of the gasket configured to engage the spacer 27 may extend perpendicular to the axis of the displacer, and the opposing end surfaces configured to engage the forming portion 30b may be inclined at an angle matching the slope of the forming portion 30b to facilitate a strong engagement between the spacer 27 and the forming portion 30b.

[0073] Figure 8 and Figure 9 The illustration shows a first-stage displacement device and a second-stage displacement device connected via an attachment mechanism in a manner similar to the previous embodiment, except that the attachment mechanism does not include a spacer and the at least one forming portion includes a pin 30c. The pin 30c extends radially outward from a corresponding hole 32 in the second-stage displacement device 14 and is configured to engage a shoulder defined in a recess 22 of the plug 21. The shoulder may include a hole for receiving a screw for securing a retaining device 24 to the plug 21. A washer 31 is positioned between the shoulder and the pin 30c. The pin 30c can be press-fitted or threaded to the second-stage displacement device 14. It will be understood that any number of pins can be used to create the forming portion of the second-stage displacement device. For example, one pin or multiple pins may be used.

[0074] Figure 10 and Figure 11 The diagram illustrates the relationship between... Figure 8 and Figure 9The first and second stage displacement devices are connected in a similar manner via an attachment mechanism, except that there is no washer and the pin 30c does not extend all the way through the wall of the second stage displacement device. Instead, the pin 30c is received in a recess 33 and a retaining device 24 formed in the second stage displacement device 14. The pin 30c can be secured to the second stage displacement device 14 by press fit or by thread. In some embodiments, only one pin is present. In some embodiments, two pins are present. In some embodiments, more than two pins may be present, circumferentially distributed around the second stage displacement device.

[0075] Figure 12 An embodiment of the attachment mechanism is illustrated, in which the spacer includes a spring 34. The spring 34 is configured to be externally mounted around the end of the second-stage displacer 14 to bias the forming portion 30 away from the end surface of the recess 22 of the plug 21. This biasing of the spring 34 creates a channel for refrigerant flow and also provides a degree of flexibility to the joint between the first-stage and second-stage displacers. This flexibility helps reduce vibrations transmitted through the attachment mechanism and helps allow the axis of the second-stage displacer 14 to be slightly offset from the axis of the first-stage displacer 12.

[0076] In some embodiments, the attachment mechanism includes a second spring mounted around the exterior of the second-stage displacementr 14 to bias the retaining device away from the forming portion 30. By providing two springs on the two sides of the forming portion 30, the second-stage displacementr 14 may have some axial degrees of freedom (if this is necessary for the operation of the cold head, for example, to help reduce vibration).

[0077] exist Figure 12 In the embodiment shown, the plug 12 is attached to the first-stage displacement device 12 by a pin 35. It will be understood that one or more pins may be used. The pin 35 may be press-fitted or threaded to the first-stage displacement device 12 and / or the plug 21. In addition to the pin 35, adhesive may be used to secure the plug 21 to the first-stage displacement device.

[0078] In some embodiments, the cold head further includes a first demagnetized magnetic ring rotatably mounted around the outer side of the end of the second-stage displacement device and a second demagnetized magnetic ring rotatably mounted around the second cylinder. The first and second magnetic rings are oriented relative to each other, i.e., the opposite poles of the first and second magnetic rings are aligned along the axis of the cold head. An actuator is used to rotate the second magnetic ring. The first magnetic ring is attracted to the second magnetic ring and therefore rotates with the second magnetic ring. Given that the first magnetic ring is rotatably fixed to the second-stage displacement device, the actuator is capable of rotating the second-stage displacement device. This can be useful if there is increased friction between the second-stage displacement device and the second cylinder under certain orientations of the displacement device. The actuator can be used to rotate the second displacement device away from these orientations to reduce or minimize friction. It should be noted that the friction of the second-stage displacement device can be observed by measuring the temperature of the second stage of the cold head.

[0079] Figure 13 The steps of a method for attaching a first-stage displacement device of a two-stage cold head to a second-stage displacement device using an attachment mechanism according to an embodiment are shown.

[0080] In step S10, the method includes attaching the plug of the attachment mechanism to the end of the first-stage displacement device.

[0081] In step S20, a retaining device for the attachment mechanism is installed around the end of the second-stage displacement device.

[0082] In step S30, a retaining device is secured to the plug using a device for fixing (such as a screw), such that the end of the second-stage displacement device is held within the recess of the plug, and the retaining device engages with at least one forming portion extending from the radial outer surface of the second-stage displacement device.

[0083] The embodiments described above offer the following advantages: • No connector pin penetrates the body of the replacement device; • The dead volume between each level is relatively small; For displacement devices of the same overall length, more regenerator packing can be placed inside the displacement device compared to a cold head with two pin joints; or • It can reduce the length of the displacement device and cylinder without compromising performance, because an additional accumulator can be used for the same length of displacement device compared to a cold head with a two-pin joint.

[0084] Although illustrative embodiments of the invention have been disclosed in detail herein with reference to the accompanying drawings, it should be understood that the invention is not limited to the precise embodiments, and that various changes and modifications can be made therein by those skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.

[0085] Figure Labels 10 Two-stage cooling block 11 First Cylinder 12 First-stage displacement device 13 Second Cylinder 14 Second-stage displacement device 15. Cold accumulator 16. Cavity 17 holes 18 motors 20 Attachment mechanisms 21. Plug 22 recess 23 inner hole 24 Holding devices Holes 25a and 25b 26 Through Holes 27 Spacer 28 channels 29 sales 30 Formation section 31 Washer 32 holes 33 recess 34 Springs 35 sales

Claims

1. An attachment mechanism for connecting a first-stage displacement device of a two-stage cold head to a second-stage displacement device of the two-stage cold head, the attachment mechanism comprising: A plug that can be attached to the end of the first-stage displacement device, the plug including a recess for receiving the end of the second-stage displacement device; A retaining device configured to be mounted at least partially around the end of the second-stage displacement device and to retain the end of the second-stage displacement device within the recess of the plug by engaging at least one forming portion extending from the radially outer surface of the second-stage displacement device; as well as Device for securing the retaining device to the plug.

2. The attachment mechanism according to claim 1, wherein, The fixing device includes at least one pin, and wherein the retaining device and the plug each include at least one corresponding hole for receiving the at least one pin.

3. The attachment mechanism according to claim 2, wherein, The at least one pin of the fixing device is fixed to the retaining device and / or the plug by press fit or by thread.

4. The attachment mechanism according to any of the preceding claims, wherein, The retaining device includes one or more through holes to allow refrigerant used to cool the cold head to enter the recess of the plug.

5. The attachment mechanism according to any of the preceding claims, further comprising a spacer configured to be mounted at least partially around the end of the second-stage displacer to space the end of the second-stage displacer from the end surface of the recess of the plug.

6. The attachment mechanism according to claim 5, wherein, The spacer at least partially defines at least one channel, the at least one channel being configured to allow refrigerant for cooling the cold head to enter the region of the recess directly adjacent to the end of the second-stage displacement device.

7. The attachment mechanism according to claim 5 or claim 6, wherein, The spacer includes a first spring configured to be mounted around the end of the second-stage displacement device to bias the at least one forming portion away from the end surface of the recess of the plug.

8. The attachment mechanism according to any of the preceding claims, wherein, The recess of the plug includes an inner hole for allowing refrigerant to pass between the end of the first-stage displacement device and the end of the second-stage displacement device.

9. A two-stage cooling block, comprising: The first cylinder houses the first-stage displacement device; as well as A second cylinder, attached to the end of the first cylinder, houses a second-stage displacement device, the second-stage displacement device including at least one formed portion extending from the radially outer surface of the second-stage displacement device. The first-stage displacement device and the second-stage displacement device each include a refrigerant accumulator and are configured to move within the first cylinder and the second cylinder, respectively, to allow refrigerant to pass through each of the refrigerant accumulators in order to cool the refrigerant. The second-stage displacement device is attached to the first-stage displacement device via the attachment mechanism according to any of the preceding claims. The plug is attached to the end of the first-stage displacement device, and the retaining device is mounted and secured to the plug around the end of the second-stage displacement device such that it engages with the at least one forming portion to retain the end of the second-stage displacement device within the recess of the plug.

10. The cold block according to claim 9, wherein, The plug is attached to the end of the first-stage replacement device with glue.

11. The cold head according to claim 9 or claim 10, wherein, The plug is attached to the end of the first-stage displacement device by at least one pin, the at least one pin extending between a corresponding recess formed in the plug and in the first-stage displacement device.

12. The cold head according to any one of claims 9 to 11, wherein, The at least one forming portion includes at least one protrusion integrally formed with the second-stage displacement device.

13. The cold head according to any one of claims 9 to 11, wherein, The at least one forming portion includes at least one pin extending from at least one corresponding recess or through-hole defined in the second-stage displacement device.

14. The cold head according to any one of claims 9 to 13, wherein, The at least one forming portion includes a rectangular cross section or a truncated conical cross section.

15. A Gifford-McMahon (GM) refrigerator comprising a cold head according to any one of claims 9 to 14.

16. A cryogenic pump, a utility tool for liquefying gases, or a utility tool for cooling a quantum computer, comprising the GM chiller according to claim 15.

17. A method for attaching a first-stage displacement device of a two-stage cold head to a second-stage displacement device of the two-stage cold head using an attachment mechanism, the method comprising: The plug of the attachment mechanism is attached to the end of the first-stage displacement device; A retaining device for the attachment mechanism is mounted around the end of the second-stage displacement device; The retaining device is secured to the plug using a device for securing the attachment mechanism, such that the end of the second-stage displacement device is held within the recess of the plug, and the retaining device engages with at least one forming portion extending from the radial outer surface of the second-stage displacement device.

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