Apparatus using vibrationally isolating stirling cooler system

Abstract

A vibration isolation system for mounting a Stirling cooler on a base. The system may include a number of cushioning elements for connecting the Stirling cooler to the base. The system also may include balance mass spring connected to the Stirling cooler and a balance mass connected to the balance mass spring.

Description

FIELD OF INVENTION

[0002] The present invention relates generally to refrigeration systems and more specifically relates to refrigeration systems with one or more Stirling coolers mounted therein in a manner so as to reduce internal vibrations.

BACKGROUND OF THE INVENTION

[0003] In the beverage industry and elsewhere, refrigeration systems are found in vending machines, glass door merchandisers (“GDM's”), and other types of dispensers and coolers. These systems generally have used a conventional vapor compression (Rankine cycle) refrigeration apparatus to chill beverages or other products therein. In the Rankine cycle apparatus, the refrigerant in the vapor phase is compressed in a compressor so as to cause an increase in temperature. The hot, high-pressure refrigerant is then circulated through a heat exchanger, called a condenser, where it is cooled by heat transfer to the surrounding environment. As a result, the refrigerant condenses from a gas back to a liquid. After leaving the condenser, the refrigerant passes through a throttling device where the pressure and the temperature of the refrigerant are reduced. The cold refrigerant leaves the throttling device and enters a second heat exchanger, called an evaporator, located in or near the refrigerated space. Heat transfer with the evaporator and the refrigerated space causes the refrigerant to evaporate or to change state from a saturated mixture of liquid and vapor into a superheated vapor. The vapor then leaves the evaporator and is drawn back into the compressor so as to repeat the cycle.

[0004] Although the Rankine cycle systems adequately chill the products therein and are in widespread use, there are several known disadvantages involved. First, the systems are generally large and heavy. Second, the systems may be noisy to operate. Third, the systems may have a significant power draw. Further, conventional Rankine systems generally use refrigerants for their working medium. These refrigerants are known to be harmful to the environment. The refrigerants may in some cases be noxious. The commonly used HFC refrigerant (134a) is generally assumed not to be noxious, though there have been claims to the contrary. This refrigerant, however, is known to be a powerful “greenhouse” gas.

[0005] One alternative to the use of a Rankine cycle system is a Stirling cycle cooler. The Stirling cycle cooler is also a wellknown heat transfer mechanism. Briefly described, a Stirling cycle cooler compresses and expands a gas (typically helium) to produce cooling. This gas shuttles back and forth through a regenerator bed to develop much greater temperature differentials than may be produced through the normal Rankine compression and expansion process. Specifically, a Stirling cooler may use a displacer to force the gas back and forth through the regenerator bed and a piston to compress and expand the gas. The regenerator bed may be a porous element with significant thermal inertia. During operation, the regenerator bed develops a temperature gradient. One end of the device thus becomes hot and the other end becomes cold. See David Bergeron, Heat Pump Technology Recommendation for a Terrestrial Battery-Free Solar Refrigerator, September 1998. Patents relating to Stirling coolers include U.S. Pat. Nos. 5,678,409; 5,647,217; 5,638,684; 5,596,875 and 4,922,722, all incorporated herein by reference.

[0006] Stirling cooler units are desirable because they are nonpolluting, efficient, and have very few moving parts. The use of Stirling coolers units has been proposed for conventional refrigerators. See U.S. Pat. No. 5,438,848, incorporated herein by reference. The integration of a free-piston Stirling cooler into a w conventional refrigerated cabinet, however, requires different manufacturing, installation, and operational techniques than those used for conventional compressor systems. See D. M. Berchowitz et al., Test Results for Stirling Cycle Cooler Domestic Refrigerators, Second International Conference. As a result, the use of the Stirling coolers in, for example, beverage vending machines, GDM's, and other types of dispensers, coolers, or refrigerators is not well known.

[0007] One difficulty in the use of a Stirling cooler is the constant vibration produced by the operation of the internal free piston. In order to avoid transmitting the vibrations to the products or to the other components of the refrigeration unit, it is desirable to isolate these vibrations from the refrigeration unit as a whole. If not isolated, such constant vibrations may cause an unwanted noise or even reduce the life of the refrigeration unit or the components therein.

[0008] There is a desire, therefore, for adapting Stirling cooler technology to conventional beverage vending machines, GDM's, dispensers, and similar types of refrigeration units. Likewise, there is a desire for isolating the Stirling coolers within these units so as to extend the life of the units and make the units more attractive to consumers.

SUMMARY OF THE INVENTION

[0009] The present invention thus provides a vibration isolation system for mounting a Stirling cooler on a base. The system may include a number of cushioning elements for connecting the Stirling cooler to the base. The system also may include balance mass spring connected to the Stirling cooler and a balance mass connected to the balance mass spring.

[0010] Specific embodiments of the invention may include that the Stirling cooler vibrates with a given frequency. The balance mass spring may vibrate at about the given frequency and about one hundred eighty (180) degrees out of phase. The balance mass and the balance mass spring may be resonant at about sixty (60) to about seventy-five (75) cycles per second.

[0011] The isolation system may include a frame. The frame may be positioned between the Stirling cooler and the balance mass spring. The isolation system may include a support plate. The support plate may be positioned between the Stirling cooler and the cushioning elements. The support plate may include a thermoplastic. The cushioning elements may include one or more elastomeric members or compression springs. The cushioning elements may include a central member. The central member may be surrounded by the elastomeric members. The cushioning elements may include one or more fastening members. The fastening members may be positioned about the elastomeric members. The cushioning elements may include a first end cushioning element positioned about a first end of the Stirling cooler and a second end cushioning element positioned about a second end of the Stirling cooler.

[0012] A further embodiment of the present invention may provide for a refrigeration system. The refrigeration system may include a refrigeration deck and a Stirling cooler. The Stirling cooler may be mounted on the refrigeration deck by an isolation system so as to reduce the amount of vibration transmitted by the Stirling cooler to the refrigeration deck.

[0013] The isolation system may include a balance mass system connected to said Stirling cooler. The balance mass system may include a balance mass spring connected to the Stirling cooler and a balance mass connected to the balance mass spring. The Stirling cooler may vibrate with a given frequency. The balance mass spring may vibrate at about the given frequency and about one hundred eighty (180) degrees out of phase. The balance mass and the balance mass spring may be resonant at about sixty (60) to about seventy-five (75) cycles per second.

[0014] The isolation system herein may include a number of cushioning members positioned between the Stirling cooler and the refrigeration deck. These cushioning members may include one or more elastomeric members or compression springs. The cushioning members may include a first end cushioning member positioned about a first end of the Stirling cooler and a second end cushioning member positioned about a second end of the Stirling cooler.

[0015] The refrigeration system also may include a hot air exhaust system positioned about the refrigeration deck. The hot air exhaust system may include a shroud surrounding the Stirling cooler. The hot air exhaust system may include an air movement device in communication with the shroud so as to define an air flow path through the shroud and past the Stirling cooler for hot air exhaust.

[0016] Other features of the present invention will become apparent upon review of the following detailed description of the embodiments when taken in conjunction with the drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 is a side plan view of a beverage dispenser.

[0018] FIG. 2 is a side cross sectional view of a Stirling cooler unit as mounted within the beverage dispenser of FIG. 1.

[0019] FIG. 3 is a top perspective view of a Stirling cooler unit for use within the beverage dispenser of FIG. 1.

[0020] FIG. 4 is a perspective view of a Stirling cooler unit mounted within the beverage dispenser of FIG. 1

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

[0021] Referring now to the drawings, in which like numerals indicate like elements throughout the several views, FIG. 1 shows a refrigeration device 100. The refrigeration device 100 may be any type of refrigerated space, such as a refrigerator, a merchandiser, a vending machine, a cooler, or similar types of devices. For the purpose of example, the refrigeration device 100 shown herein may largely be in the form of a beverage dispenser 110. The beverage dispenser 110 generally may be of conventional design and may take any desired size, shape, or capacity. The design and organization of the refrigeration device 100 or the beverage dispenser 110 as described herein should not limit the scope or adaptability of the components described in detail below. Specifically, any type of configuration of the refrigeration device 100, the beverage dispenser 110, or other structure may be used herein. Alternatively to the refrigeration device 100, the present invention also may be used with a means to heat a given space.

[0022] The refrigeration device 100 in general and the beverage dispenser 110 in specific may have a refrigeration deck area 120 and a product area 130. The refrigeration deck components, as will be described in more detail below, may be positioned largely within the refrigeration deck area 120. The items or fluids to be chilled may be positioned within the product area 130. The refrigeration deck area 120 may be at the top or the bottom of the refrigeration device 100 or the beverage dispenser 110. Access to the refrigerated deck area 120 may be provided through the product area 130 or through an access area 140 positioned anywhere along the refrigeration deck area 120. One or more frame members 145 may define the refrigeration deck area 120 and the product area 130.

[0023] As is shown in FIG. 2, refrigeration deck 150 may be positioned within the refrigeration deck area 120. The refrigeration deck 150 may include a base plate 155. The refrigeration deck 150 and the base plate 155 may be made out of stainless steel, aluminum, or similar types of materials. The dimensions of the refrigeration deck 150 and the base plate 155 may depend upon the size of the refrigeration deck area 120 and the refrigeration device 100 as a whole.

[0024] The refrigeration deck 150 may include a plurality of refrigeration components 160. Generally described, the refrigeration components 160 may include one or more Stirling coolers 170. As is well known, a Stirling cooler may include a cold end 180 and a hot end 190. The Stirling cooler 170 may be driven by a free piston (not shown) positioned within a casing 200. By way of example, the Global Cooling Company of Athens, Ohio may manufacture a Stirling cooler 170 suitable for use with the present invention. Any conventional type of Stirling cooler 170, however, may be used herein. Further, any number of Stirling coolers 170 may be used herein.

[0025] The cold end 180 of the Stirling cooler 170 may be connected to a heat transfer device 185. The heat transfer device 185 may transfer heat from the product area 130 in a manner well known to those skilled in the art. The heat transfer device 185 may be a heat exchanger, a thermosiphon, a condenser and evaporator, or any similar type of transfer system. An air movement device (not shown) and one or more pumps (not shown) may be used in cooperation with the heat transfer device 185. The heat transfer device 185 also may be used to transport heat to the product area 130 if desired. Further, multiple heat transfer devices 185 may be used.

[0026] A heat exchanger 195 may surround the hot end 190 of the Stirling cooler 170. The heat exchanger 195 may include a plurality of heat-conducting fins 202. The heat-conducting fins 202 may be made out of aluminum or similar types of materials with good heat transfer characteristics. The fins 202 may be aligned in a substantially circular pattern with an air gap adjacent to each fin 202 so as to permit the flow of air therethrough. The fins 202 and the heat exchanger 195 in general, however, may be arranged in any convenient form.

[0027] A fan shroud 204 may surround the Stirling cooler 170. The fan shroud 204 may extend from the hot end heat exchanger 195 to the refrigeration deck 150. The fan shroud 204 may be made out of plastic, aluminum, or similar types of materials. The fan shroud 204 may be insulated. The fan shroud 204 may have an air movement device 206 positioned thereon. The air movement device 206 may be a conventional fan. Alternatively, a bellows, a pump, a screw, or the like known to those skilled in the art may be used. The fan shroud 204 may define an airflow path 208 through the hot end heat exchanger 195 and out via the air movement device 206. The fan shroud 204 thus directs a flow of warm air away from the Stirling cooler 170.

[0028] As is shown in FIGS. 2-4, the Stirling cooler(s) 170 may be positioned within the refrigeration deck 150 via a vibration control system 210. The vibration control system 210 may include a balance mass system 220. The balance mass system 220 may include a balance mass bracket 230 that surrounds one end of the casing 200 of the Stirling cooler 170. The balance mass bracket 230 may be made out of substantially rigid materials such as steel, aluminum, or similar types of materials. Attached to the bracket 230 may be a balance mass spring 240. The balance mass spring 240 may be pre-calibrated so as to provide a resonance to the balance mass system 220 at a specific frequency such that the system 220 will respond to motion with a vibration at a given frequency and phase.

[0029] Attached to the balance mass spring 240 may be a balance mass 250. As is well known, the balance mass 250 may be a substantially tubular structure that is mounted on the balance mass spring 240 for vibration therewith. The balance mass 250 may be positioned above the base plate 155 of the refrigeration deck 150. The balance mass 250 generally does not come into contact with the base plate 155. Rather, an aperture 255 may be positioned within the base plate 155 so as to permit the balance mass 250 to extend below the level of the base plate 155 if needed. The mass of the balance mass 250 and the calibration of the balance mass spring 240 may be predetermined so as to counteract or reduce the vibrations produced by the Stirling cooler 170. In other words, the balance mass 250 and the balance mass spring 240 may be tuned so that their resonant frequency equals the operating frequency of the Stirling cooler 170.

[0030] For example, if the Stirling cooler 170 vibrates at about sixty (60) to about seventy-five (75) cycles per second, then the balance mass 250 and the balance mass spring 240 also may be calibrated to vibrate at about sixty (60) to about seventy-five (75) cycles per second. The balance mass 250 and the balance mass spring 240, however, may be out of phase with the Stirling cooler 170 by about one hundred eighty degrees (180°). This phase change may cause the opposing vibrations substantially to cancel each other out.

[0031] The resonant frequency may or may not be set at the operating frequency depending upon the desired system response. In this case, the balance mass 250 and the balance mass spring 240 (i.e., the spring rate) may have a resonance chosen to be at the operating frequency of the Stirling cooler 170. By doing so, the balance mass 250 will balance the casing motion (in the ideal case) of the Stirling cooler 170 and the residual vibration of the Stirling cooler 170 may be reduced to minimum levels. In practice, however, there may be some residual vibration.

[0032] The calibration of the balance mass 250 and the balance mass spring 240 is well known to those skilled in the art. Specifically, the balance mass spring 240 may be chosen so that its spring rate (force per unit deflection) is such that when it is attached to a particular mass it may form a spring-mass system resonance at a particular frequency or range. The resonant frequency (in radians per second) generally equals the square root of the spring rate (in Newtons per meter) divided by the mass (in kilograms).

[0033] The vibration control system 210 also may include a mounting system 260 for the Stirling cooler 170. The mounting system 260 may include a mounting plate 270. The mounting plate 270 may surround and substantially support the balance mass bracket 230. The mounting plate 270 may be made out of a thermoplastic such as Delrin (an acetal resin), Nylon, or similar types of materials. The use of a thermoplastic may be preferred in that it may absorb or dampen somewhat more of the vibrations produced by the Stirling cooler 170 as compared to a metal or a similar type of material.

[0034] The mounting system 260 may include a number of lower vibration isolation mounts 280. The lower vibration isolation mounts 280 may connect and support the Stirling cooler 170 and the vibration control system 210 on the base plate 155 of the refrigeration deck 150. The lower vibration isolation mounts 280 may be mounted onto the base plate 155 of the refrigeration deck 150 in any convenient manner. Specifically, the lower vibration isolation mounts 280 may extend through or about an aperture 290 in the base plate 155 to an aperture 300 in the mounting plate 270 or otherwise be positioned in any convenient location.

[0035] Each lower vibration isolation mount 280 may include a central pin 310 and a number of cushioning members 320. The pin 310 may include a shaft 330 with an aperture 340 on one end and a flange 350 on the other. The pin 310 may be made out of steel, aluminum, or similar types of materials. The flange 350 may be positioned about the aperture 290 within the base plate 155 of the refrigeration deck 150 while the aperture 340 may clear the mounting plate 270. A cotter pin 360 or a similar type of locking device may extend through the aperture 340 so as to hold the pin 310 in place. The lower vibration isolation mounts 280 also may use any other type of positioning means.

[0036] The cushioning members 320 may be made out of rubber, polyurethane, Neoprene, Sorbothane, or other types of soft compliant elastomeric materials. By way of example, Sorbothane is a highly damped, viscoelastic material useful over a wide range of temperatures and frequencies. Sorbothane is a proprietary polymer available from Sorbothane, Inc. of Kent, Ohio. The cushioning members 320 may have a durometer of about forty (40) to seventy (70). The cushioning members 320 may be substantially in the form of one or more washers or similar types of toroidal shapes. The cushioning members 320 also could be in the form of compression springs. In this embodiment, three (3) cushioning members 320 may be used per pin 310. Any desired number of cushioning members 320, however, may be used. Likewise, four (4) lower vibration isolation mounts 280 are used herein. Any number of vibration isolation mounts 280, however, may be used as desired.

[0037] The mounting system 260 also may include an upper vibration isolation mount 390. The upper vibration isolation mount 390 may maintain the Stirling cooler 170 and the other elements herein in a substantially vertical position without transmitting vibration to the refrigeration device 100 as a whole. The upper vibration isolation mount 390 may be connected between an aperture 400 in the fan shroud 370 and an aperture 410 in the frame 145 of the refrigeration device 100 or in any other convenient location.

[0038] The upper vibration isolation mount 390 may include a threaded cylinder 420 positioned on either end of a cylinder of elastic material 430. The cylinder 430 may be made out of rubber, polyurethane, Neoprene, Sorbothane, or other types of soft compliant elastomeric materials. The cylinder 430 may have a durometer of about forty (40) to seventy (70). Each thread 420 may be attached to the cylinder 430 via an attachment flange 435. The attachment flange 435 may be bonded to the cylinder 430. The thread 420 may be secured by one or more bolts 440 or similar types of fastening devices. The upper vibration isolation mount 390 also may be similar to the lower vibration isolation mounts 280. The upper vibration isolation mounts 390 also may use any other type of positioning means.

[0039] In use, the refrigeration deck 150 may be positioned within the refrigeration deck area 120. The heat transfer device 185 may be connected in communication with the cold end 180 of the Stirling cooler 170. The Stirling cooler 170 then may be operated so as to cool the product area 130 of the refrigeration device 100. Exhaust heat may be removed from the refrigeration device 100 via the air movement device 206.

[0040] The vibrations produced by the Stirling cooler 170 may largely be isolated through the use of the vibration control system 210. Specifically, the use of the balance mass system 220 and the mounting system 260. The vibrations produced by the Stirling cooler 170 largely may be cancelled out by the balance mass system 220 or absorbed by the mounting system 260. The use of the balance mass 250 and the balance mass spring 240 may counteract larger amplitude vibrations. Specifically, most of the vibrations may be cancelled out by the balance mass system 220 operating out of phase with the Stirling cooler 170. The use of the lower and upper vibration isolation mounts 280, 390 also may reduce the amount of other or residual vibrations transmitted from the Stirling cooler 170 to the frame 145 of the refrigeration device 100.

[0041] The use of the vibration control system 210 may reduce the amount of vibration transmitted from the Stirling cooler 170 to the frame 145 of the refrigerated device 100 by about seventy-five percent (75%) to about ninety-five percent (95%) as compared to a hard mounted system. The Stirling cooler 170 or coolers 170 are thus substantially vibrationally isolated from the remainder of the refrigerated device 100.

[0042] It should be apparent that the foregoing relates only to the preferred embodiments of the present invention and that numerous changes and modifications may be made herein without departing from the spirit and scope of the invention as defined by the following claims.

Claims

1. A vibration isolation system for mounting a Stirling cooler on a base, comprising: a plurality of cushioning elements connecting said Stirling cooler to said base; a balance mass spring connected to said Stirling cooler; and a balance mass connected to said balance mass spring.

2. The vibration isolation system of claim 1, wherein said Stirling cooler vibrates with a given frequency and wherein said balance mass spring vibrates at about said given frequency and about one hundred eighty (180) degrees out of phase.

3. The vibration isolation system of claim 1, wherein said balance mass and said balance mass spring are resonant at about sixty (60) to about seventy-five (75) cycles per second.

4. The vibration isolation system of claim 1, further comprising a frame, said frame positioned between said Stirling cooler and said balance mass spring.

5. The vibration isolation system of claim 1, further comprising a support plate, said support plate positioned between said Stirling cooler and said plurality of cushioning elements.

6. The vibration isolation system of claim 5, wherein said support plate comprises a thermoplastic.

7. The vibration isolation system of claim 1, wherein said plurality of cushioning elements comprises one or more elastomeric members.

8. The vibration isolation system of claim 7, wherein said plurality of cushioning elements comprises a central member, said central member surrounded by said one or more elastomeric members.

9. The vibration isolation system of claim 7, wherein said plurality of cushioning elements comprises one or more fastening members, said one or more fastening members positioned about said one or more elastomeric members.

10. The vibration isolation system of claim 1, wherein said plurality of cushioning elements comprises one or more compression springs.

11. The vibration isolation system of claim 1, wherein said plurality of cushioning elements comprises a first end cushioning element positioned about a first end of said Stirling cooler and a second end cushioning element positioned about a second end of said Stirling cooler.

12. A refrigeration system, comprising: a refrigeration deck; a Stirling cooler; said Stirling cooler mounted on said refrigeration deck by an isolation system so as to reduce the amount of vibration transmitted by said Stirling cooler to said refrigeration deck.

13. The refrigeration system of claim 12, wherein said isolation system comprises a balance mass system connected to said Stirling cooler.

14. The refrigeration system of claim 13, wherein said balance mass system comprises a balance mass spring connected to said Stirling cooler.

15. The refrigeration system of claim 14, wherein said balance mass system comprises a balance mass connected to said balance mass spring.

16. The refrigeration system of claim 15, wherein said Stirling cooler vibrates with a given frequency and wherein said balance mass spring vibrates at about said given frequency and about one hundred eighty (180) degrees out of phase.

17. The refrigeration system of claim 15, wherein said balance mass and said balance mass spring are resonant at about sixty (60) to about seventy-five (75) cycles per second.

18. The refrigeration system of claim 12, wherein said isolation system comprises a plurality of cushioning members positioned between said Stirling cooler and said refrigeration deck.

19. The refrigeration system of claim 18, wherein said plurality of cushioning members comprises one or more elastomeric members.

20. The refrigeration system of claim 18, wherein said plurality of cushioning members comprises a first end cushioning member positioned about a first end of said Stirling cooler and a second end cushioning member positioned about a second end of said Stirling cooler.

21. The refrigeration system of claim 12, further comprising a hot air exhaust system positioned about said refrigeration deck.

22. The refrigeration system of claim 21, wherein said hot air exhaust system comprises a shroud surrounding said Stirling cooler.

23. The refrigeration system of claim 22, wherein said hot air exhaust system comprises an air movement device in communication with said shroud so as to define an air flow path through said shroud and past said Stirling cooler.