AU613110B2 - Refrigeration system expansion device - Google Patents

Description

alr'1141UT 1 Lieclarr(s) (no attesLation 1equired).

Note: Initial all alkraions.

By: a y Timothy J. an, Vice Presidcnt Secretary DAVIES COLLISON,. MELBOIJRNE ind CANBERRA.

r AU-AI-25326/88 I 1P'~ SWORLNTELLECTL PROPERTY GAATION INTERNATIONAL APPLICATION BLI E NDIR TH PA T COOPERATION TREATY (PCT) (51) International Patent Classification 4 (11) International Publication Number: WO 89/02556 F16K 15/02 Al (43) International Publication Date: 23 March 1989 (23.03,89) (21) International Application Number: PCT/US88/03107 (22) nternationnl Filing Date: 9 September 1988 (09.09.88) (31) Priority Application Number: 096,979 (32) Priority Date: (33) Priority Country: i4 Scptember 1987 (14,09.87)1 (71) Applicant: ROBERTSHAW CONTROLS COMPANY [US/US]; 1701 Byrd Avenue, Richmond, VA 23261

(US).

(72) Inventors: SEPSO, Roger, P. 115 Middlebrook Road, Stratford, CT 06497 HALMOSE, John, M. 47 Manhattan Avenue, Bridgeport, CT 06606 (US).

(74) Agents: BECKER, Robert, Becker Becker, Inc., Suite 820, 211 S. Main Street, Dayton, OH 45402 (US) et al.

(81) Designated States: AT (European patent), AU, BE (European patent), BR, CH (European patent), DE, DE (Utility model), DE (European patent), FR (European patent), GB, GB (European patent), IT (European patent), JP, LU (European patent), NL (European patent), SE (European patent), Published With international search report.

With amended claims.

P. 2 5 MAY 198

AUSTRALIAN

17 APR 1989 PATENT OFFICE (54) Title: REFRIGERATION SYSTEM EXPANSION DEVICE (57) Abstract An. expansion device for a refrigeration system, comprising a housing (21) having opposed ports (22, 23) separated from each other by an internal valve seat (30) of the housing The housing contains ti movable piston (44) having a first end surface (45) adapted to engage against a valve seat (30) to tend to close the same when the piston (44) is disposed in a first position, and a second end surface (46) for engaging against an annular shoulder (40) when the piston (44) is disposed in a second position. The piston (44) has.a passage (47) passing therethrough for interconnecIig the opposed ports (22, 23) together in a restricted manner when the piston (44) is in the first position thereof, and an outer peripheral surface (49) having a plurality of grooves (48) therein for Interconnaecting the opposed ports (22, 23) together in a substantially nonrestricted manner when the piston (44) is in the second position thereof, The piston (44) comprises a one-piece member of polymeric material, the first end surface (45) of the piston (44) comprising a substantially hemispherical section EXPANSION DEVICE FOR A REFRIGERATION SYSTEM.

PISTON THEREFOR AND METHODS OF MAKING THE SAME This invention relates to a new expansion device for a refrigeration system and to a new piston for such an expansion device, as well as to new methods of making such a piston.

Previously, it has been suggested to provide an expansion device f or a ref rigeration system and comprising a housing means having opposed port means for coupling the device in the system and being separated *from each other by an internal vralve seat means of the *.:housing means, and a movable piston disposed in the housing means and having a first end surface means 15 adapted to engage against the valve seat means to tend to close the same when the piston is disposed in a f irst position thereof in the housing means, the housing means having an annular shoulder means, the piston having a second end surface means for engaging against the shoulder means when the piston is disposed in a secondI 0*S**position thereof in the housing means, the piston having a paigsage means passing therethrough and through the end ft surf ace means thereof for interconnecting the opposed port means together in a restricted manner when the pisto'n is in the first position thereof, the piston also h n sraemen oete n bigpovd~ it~ *having an outer peripheral surface means interconnectingI plurlityof grooves therein for Interconnecting the opposed port means together in a substantially nonrestricted manner when the piston is in the second position thereof. For example, see the U.S. patent to Duell et al, No. 3,992,898.

Also, see the U.S. patent to Lovingham, No.

3,805,825, wherein it appears that the movable piston check valve means thereof comiprises a one-piece member formed of polymeric materiala 91041;rcnpo.00 1 2.32&cIa1 -2- Also see the U.S. patent to Genbauffe et al, No.

4,431,117, wherein a hemispherical end is disposed in a self-aligning manner into a frusto-conical seat.

It is one preferred object of this invention to provide a new expansion device for a refrigeration system and wherein a tendency for the movable piston thereof to chatter is substantially reduce.

Accordingly, it is another object of this invention to provide a new expansion device for a refrigeration system.

For example, pursuant to one aspect of this invention there is provided an expansion device for a i refrigeration system comprising a housing means having opposed port means for coupling said device in said system and being separated from each other by an internal valve seat means of said housing means, and a movable piston disposed in said housing means and having a first end surface means adapted to engage against said valve seat means to tend to close the same when said piston is 20 disposed in a first position thereof in said housing 4 0 means, said housing means having an annular shoulder o. o means, said piston having a second end surface means for engaging against said shoulder means when said piston is disposed in a second position thereof in said housing means, said piston having a passage means passing therethrough and through said end surface means thereof for interconnecting said opposed port means together in a restricted manner when said piston is in said first position thereof, said piston also having an outer peripheral surface means interconnecting said end surface means together and being provided with a plurality of grooves therein for interconnecting said opposed port means together in a substantially non-restricted manner when said piston is in said second position thereof, said piston comprising a one-piece member of polymeric material, said first end surface means of said piston 9141gjnspe.32 a,2

I

-3having a substantially hemispherical section that is the part thereof that is adapted to engage said valve( seat means when said piston is in said first position thereof, said housing means having a cylindrical chamber therein that leads to said valve seat means and has substantially the same sized circular transverse cross-sectional configuration from one end thereof to the other end thereof, said valve seat means being substantially frusto-conical with the larger base thereof being the same size as said circular transverse cross-sectional configuration and joining with said chamber at one of said ends thereof, said piston being disposed in said chamber for movement therein between said positions S- thereof.

Sj.. 15 According to a second aspect of the invention there is provided a piston for an expansion device for a refrigeration system wherein the device has a housing means provided with opposed port means for coupling said device in said system and being separated from each other by an internal valve seat means of said housing means, said piston being adapted to be disposed in said housing means and have a first end surface means adapted to engage against said vaive seat means to tend to close the same when said piston is disposed in a first position thereof in said housing means, said piston having a second and surface means adapted to engage against an annular shoulder means of said housing means wherein said piston is disposed in a second position thereof in said housing means, s.id piston having a passage means passing therethrough and through said end surface means thereof for interconnecting said opposed port means together in a restricted manner when said piston is in said first position thereof, said piston having an outer peripheral surface means interconnecting said end surface means together and being provided with a plurality of grooves therein for interconnecting said opposed port means RA4,2 9104l2,gnspiOO8,25326.da,3 ii L

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0I 0 S 0S S 4* 5* 0~ 4* 4 5 4 4e 4. 0 *4 0* 0* 4 4.

S. 0 .4 0 0 S -4together in a substantially non-restricted manner when said piston is in said second position thereof, said piston comprising a one-piece member of polymeric material and said first end surface means of said piston having a substantially hemispherical section that is the part thereof that is adapted to engage said valve seat means when said piston is in said first position thereof, said grooves each interrupting said first end surface means and said second end surface means of said piston, 10 said second end surface means of said piston being substantially flat and being disposed substantially transverse to a longitudinal axis of said piston, said grooves each having a bottom surface that has two substantially straight sections, one of which is disposed 15 substantially parallel with the axis of said piston as said one section extends from said first end surface means to the other section, which is angled toward said axis of said piston as said other section extends from said one section thereof to said second end surface means 20 of said piston.

According to a third aspect of the invention there is provided a method for making a piston for an expansion device for a refrigeration system when the device has a housing means provided with opposed port means for coupling said device in said system and being separated from each other by an internal valve seat means of said housing means, said piston being adapted to be disposed in said housing means and have a first end surface means adapted to engage against said valve seat means to tend to close the same when said piston is disposed in a first position thereof in said housing means, said piston having a second end surface means adapted to engage against an annular shoulder means of said housing means when said piston is disposed in a second position thereof in said housing means, said piston having a passage means passing therethrough and through said end surface means

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4'1." 910412,gjnspe.O8,20 25c,44 -4a- *0 *i a a a a a.

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a. S a sa a a 9* *0 4 4 thereof for interconnecting said opposed port means together in a restricted manner when said piston is in said first position thereof, said piston having an outer peripheral surface means interconnecting said end surface means together and being provided with a plurality of grooves therein for interconnecting said opposed port means together in a substantially non-restricted manner when said piston is in said second position thereof, the method comprising the steps of forming said piston to comprise a one-piece member of polymerical material, forming said first end surface means of said piston to comprise a substantially hemispherical section that is the part thereof that is adapted to engage said valve 15 seat means when said piston is in said first position thereof, forming said grooves to each interrupt said first end surface means and said second end surface means of said piston, forming said second end surface means of said piston to be substantially flat and to be disposed substantially transverse to a longitudinal axis of said piston, and forming said grooves to each have a bottom surface that has two substantially straight sections, one of which is disposed substantially parallel with the axis of said piston as said one section extends from said first end surface means to the other section, which is angled toward said axis of said piston as said other section extends from said one section thereof to said second end surface means of said piston.

Another object of this invention is to provide a new piston for an expansion device for a refrigeration system.

Another object of this invention is to provide a new method for making such a piston.

Embodiments of the invention will now be described by way of example only wi.'h reference to the accompanying drawings in which:- 910412gjnspe008,25326.ca,5 .a *i a a 9a

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ii i~ -4b- The features of the invention, and its technical advantages, can be seen from the following description of preferred embodiments, together with the claims and the accompanying drawings, in which: FIG. 1 is a perspective view of one exemplary embodiment of the new expansion device of this invention; FIG. 2 is a cross-sectional view taken on line 2-2 of FIG. 1, FIG. 2 illustrating the piston of the expansion device in one operating position thereof; FIG. 3 is a view similar to FIG. 2 and illustrates the piston of the expansion device in another operating position thereof; FIG. 4 is a cross-sectional view taken on line 4-4 15 of FIG. 2; FIG. 5 is an enlarged longitudinal cross-sectional view of the new piston of this invention that is used in the expansion device of FIGS. 1-4; FIG. 6 is an exploded perspective view of the various parts of the expansion device of FIGS.

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9lo4 ZgjnspP008,5326la,6 -iL~y YY LI -Y i _1- WO 89/02556 PCT/US88/03107 FIG. 7 is a fragmentary view similar to FIG. 1 and illustrates another exemplary embodiment of the expansion device of this invention; and FIG. 8 is a fragmentary cross-sectional view taken along line 8-8 of FIG. 7.

While the various featureF of this invention are hereinafter illustrated and described as being particularly adapted to provide an expansion device for a refrigeration system, it is to be understood that the various features of this invention can be utilized singly or in various combinations thereof to provide a device for other types of apparatus as desired.

Therefore, this invention is not to be limited to only the embodiments illustrated in the drawings, because the drawings are'merely utilized to illustrate one of the wide variety of uses of this invention.

Referring now to FIGS. 1-6, the new expansion device f is generally indicated by the reference numeral 20 and comprises a housing means 21 that has opposed port means 22 and 23 for coupling the device 20 in a refrigeration system (not shown), such as by having the port mens 23 at the end 24 of the housing means 21 coupled to a conduit means (not shown) that is threadedly interconnected to external threads thereof, while the port means 22 is adapted to be interconnected to one or more capillary tubes 26 of the system that are secured in respective passages 27' of the housing means 21 that lead to the port means 22 in the manner illustrated in FIG. 2.

The housing means 21 of the expansion

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WO 8902556PCT/US88/03107 -6device 20 comprises a first housing member 27 having an end 28 that leads to an opening means 29 therein that interconnects with the port means 22 by an internal annular frusto-conica. valve seat means 30 as illustrated, with the opening means 29 defining a substantially smooth cylindrical internal peripheral surface 31 that has a suhbstantial ly circular cross-sectional configuration throughout the length thereof and eitonds from the open end 28 to the valve seat means 30 as illustrated. The opening means 29 is intarnally threaded at 32 to be threadedly interconnected to a threaded end 33 of another housing member 34 of the housing means 21. The housing member 34 has the end 33 externally threaded by threads 35 which threadedly interconnect with the internal threads 32 of the housing member 27 while cooperating shoulder means 36 and 37 of the housing members 27 and 34 interconnect in abutting relation as illustrated and sandwich a sealing gasket means. 38 therebetween, In this manner, a passage 39 of the housing member 34 that extends between the ends 24 and 33 thereof is disposed in al.igned and fluid communication with the opening means 29 in the member 21, with the end 33 of the housing member 34 cooperating with the housing member 27 to define an annular shoulder means 40 for a purpose hereinafter described.

A suitable screen-like filter means 41. is disposed in the opening or passage 39 of *the: housing member 34 and has an end 42 that abuts against an internal shoulder 43 of the housing member 34, whereby the shoul.der 43 holds the filter WO 89/02556 PCT/US88/03107 7 means 41 therein as illustrated.

The expansion device 20 has a movable piston 44 disposed therein that is movable from a first position thereof, wherein a first end surface means 45 thereof is adapted to engage against the valve seat means 30 as illustrated in FIG. 2, to another or second position thereof, wherein a second end surface means 46 thereof is adapted to engage against the shoulder means 40 as illustrated in FIG. 3. The piston 44 has a passage means 47 formed centrally therethrough and interrupting the end surface means 45 and 46 thereof so as to provide a restricted flow path between the ports 23 and 22 when the piston 44 is disposed in the first position thereof as illustrated in FIG. 2. The piston 44 is adapted to provide a substantially nonrestricted flow path between the ports 23 and 22 when the piston 44 is disposed in the second position as illustrated in FIG. 3 because a plurality of grooves 48 are formed in an outer peripheral surface means 49 thereof, with said grooves 48 interconnecting the first end surface means 45 to the second end surface means 46 in a manner hereinafter set forth.

Since the operation and use of an expansion device in a refrigeration system is well known in the art, such as set forth in the aforementioned U.S. patent to Duell et al, No.

3,992,898, whereby this patent is being incorporated into this disclosure by this reference thereto, further details of the operation of the expansion device 20 in a refrigeration system will not be set forth.

The piston 44 of this invention comprises a one-piece member made of a suitablo polymeric

-A

WO 8902556PCT/US88/03107 -8material, such as a high temperature thermoplastic that has an inherent low coefficient of friction and is sold under the trademark or trade name IVECTflAI b- The Celanese Corporation.

The piston 44 of this invention can be formed of such a polymeric material by a molding operation, if desired, or can be machined from a block thereof, if desired.

in any event, it c,?n be seen that the piston 44 of this invention hais the first end surface means 45 thereof formed with a central section 70 that defines a substantially hemispherical configuration so that the section is aatapted to self-align, or self-seat on the frusto-conical valve seat means 30 to seal closed the same when the piston 44 is in the first position thereof as illustrated in.FIG. 2.

The first end surface means 45 of the piston 44 also includes an outer annular section 51 that deheines a substantially frusto-conical configuration that has the smaller base 52 thereof interconnecting with the hemispherical section and the larger base 53 thereof interconnecting with the outer peripheral surface means 49 as illustrated.

The second end surf ace meanL 46 of the piston 44 is substantially f lat and is disposed transverse to the long'itudinal axis of the piston 44, with this axcis of the piston 44 being indicated by the refeorence numeral 54 in FIG, Th outer peripheral surface 49 of the, piston 44 is disposed closely adjacent the internal peripheral surface 31 of the housing means 21 so as to tend to dampen vibration and Chatter 3S therebetween during the operation of the ex~pansion WO 89!02556 PCT/US88/03107 device 20. For example, in one workin e.ibodiment of the expansion device 20 of this invention, the internal diameter that is defined by the surface 31 of the housing means 21 is approximately 1.168 cm (0.460 of an inch), while the outer diameter of the piston 44 that defines the external peripheral surface 49 thereof is approximately 1.162 cm (0.4575 of an inch). Such one working embodiment of the piston 44 of this invention has the hemispherical section 50 defined by a radius of approximately 0.427 cm (0.168 of an inch), and the frusto-conical surface 51 of the piston 44 is disposed substantially at an angle of 450 to the longitudinal axis 54.

Such one working embodiment of the piston 44 of this invention can have different selected dimensions for the length and diameter of the passage 47 passing therethrough so that a plurality of pistons 44 can be provided and mere selection of the one having the desired sized passage 47 therethrough will control the performance o the particular expansion device 20 using that selected piston 44 in a manner well known in the art.

For example, the passage 47 passing through the piston 44 can have a frusto-conical defining section 55 and a substantially straight section 56, with the frusto-conical section having its larger end 57 interrupting the first end surface 45, and with the straight -ection 56 interrupting the second end surface 46 as illustrated. ,In one working embodiment of the piston, 44 of this invention that has the previous dimensions set forth, the straight section 56 has a length of approximately 0,4925 cm (0.1939 of an inch) and a diameter of approximately 0.1067 cm WO 89/02556 PCT/US88/310 7 (0.0420 of an inch), while the larger base 57 of the frusto-conical section 55 has a diameter of approximately 0.1374 cm (0.0541 of an inch) and the longttudinal length of the piston member is approximately 1.27 cm (0.500 of an inch).

Of course, it is to be understood that the various dimensions previously set forth are merely examples of one working embodiment of one piston 44 of this invention and are not to be limitations on this invention.

The grooves 48 in the piston 44 are disposed in a spaced apart circular array as illustrated in the drawings, and in the one working embodiment of the piston 44 of this invention previously set forth comprise five such grooves 48, each having a width of approximately 0.157 cm (0.062 of an inch) and having a first straight section 58 thereof that has a deptbi of approximately 0.157 cm (0.062 of an inch), and thereby only interrupts the frusto-conical annular section 51 of the first end face 45, and has a bottom 59 that is spaced outwardly £rom the smaller base 52 thereof as illustrated, the bottom 59 of each groove 48 being substantially flat even though the same may be described on a ro 1 ius entending from the longitudinal axis 54 of j p Di~ton 44 so that the section 58 of each groove 49 has a substantially rectangular cross-sectional configuration throughout the length thereof.

Each groove 48 of the piston 44 has another straight section 60 that Joins with the section 58 and itterrupts the flat end surface 46 in such a manner that the bot13om 61 of the section is disposed at an angle relative to the longitudinal axis 54, and in one working embodiment S89/0256 PCT/US88/03107 WO 89/02556 11of the piston 44 previously set forth makes an angle of approximately 45' with the axis 54. Thus, it can be seen that the section 60 of each groove 48 also has a substantially rectangular crosssectional configuration throughout the length thereof.

In this manner, when the piston 44 is disposed in the second position illustrated in FIG, 3, it can be seen that the annular shoulder 40 of the housing means 21 will not close off the grooves 48, go that a free flow of fluid is provided through the grooves 48 between the por., 22 and 23 as illustrated. Also, when the piston 44 is disposed in the first position illustrated in FIG.

2, it can be seen that the hemispherical section of the piston 44 seals closed against the frustoconical valve seat means 30, so that no fluid flow through the grooves 48 can be provided between the ports 23 and 22, so that the only fluid flow provided between the ports 23 and 22 is through the restricted passage 47 of the piston for a purpose well known in the art.

As previously stated, the number of capillary tubes 26 which can be intercornected, to the port 22 of the expansion device ZO can be any desired number within reason, and the embodiment illustrated in FIGS. 1-6 has four capillary tubes 26. However, it can be seen in FIGS, 7 and 8 that a single capillary tube 26 can rcovided, and the same can be disposed in axially aligned relation with the longitudinal axis 54 of the piston member 44 as illustrated, if desired.

In any event, it can be seen that the housing members 27 and 34 can be formed of any suitable metallic material, and the capillary tubes WO 89/02556 PTU8/30 -12 26 can be secured in the respective openings 27' by silver soldering or the like when the capillary tubes 26 are formed of copper as is well known in the art.

It can be seen that thA-e sxpansion device is adapted to operate in such a manner that when the fluid flow is from the port 23 to the port 22, such fluid flow acts against the piston 44 to force the same to the position illustrated in FIG. 2, whereby the first end surface 45 of the piston 44 closes against the valve seat 30 so that all fluid flow from the port 23 to the port 22 and, thu~s, to the capillary tubes 26, is through the restricted passage 47 of the piston 44. Howe-er, when the fluid flow through -the expansion device 20 is reversed so as to flow from the port 22 ko the port 2.3, such fluid flow causes the piston, 44 to move from the first position illustrated i~n FIG. 2 to its second position illustrated in FIG. 3, wherein the second end surface 46 is now disposed against the shoulder 40 of the housing means 21 and the fluid flow is now adapted to flow in a substantially unrestricted, manner through the grooves 48 of the piston member 44 from the port 22 to the port 23.

It can be seen that the sliding movement of the piston 44 against the internal peripheral surface 31 of the housing means 21 is in a smooth manner because of -the inherent low coefficient of 4 30 friction of the polymeric material ot the piston 44 acting on the smooth internal peripheral surface 31.

of the. housing means 21. In addition, because a re! .S1a-t rely large surface is provided by the ungr, ed portion of t1\e external peripheral surf ace 49 of the piston 44 in contrast to the formed of polymeric material.

i i 910412,gnspe.o008,25326.cIaI l -13width of the grooves 48, a tendency of the piston 44 to vibrate and thereby chatter in the housing means 21 is substantially reduced over the prior known arrangements.

Therefore, it can be, seen that this invention not only provides a new expansion device for a refrigeration system and a new piston for such an expansion device, but also this invention provides a new method of making such an expansion device and a new method of making such a piston.

While the forms and methods of this invention now preferred have been illustrated and described as required, it is to be understood that other forms and method steps can be utilized and still fall within the scope of appended claims.

0* 0 0 0 So et 0 0• 0 0 0 *Ol 0, 00000 0 9lO4l2gjnsp.008,25326.cla,13

Claims (16)

1. An expansion device fcr a refrigeration system comprising a housing means having opposed port means for coupling said device in said system and being separated from each other by an internal valve seat means of said housing means, and a movable piston disposed in said housing means and having a first end surface means adapted to engage against said valve seat means to tend to close the same when said piston is disposed in a first position thereof in said housing means, said housing means havin an annular shoulder means, said piston having a second end surface means for engaging against said shoulder means when said piston is disposed in a second position thereof in said housing means, said piston having a passage means passing therethrough and through said end surface means thereof for interconnecting said opposed port means together in a restricted manner when said piston is in said first position thereof, said piston also having an outer peripheral surface means interconnecting said end surface means together and being provided with a plurality of grooves therein for interconnecting said opposed port mn ans together in a substantially non-restricted manner when said piston is in said second position thereof, said piston comprising a one-piece member of polymeric material, said first end surface means of said piston having a substantially hemispherical section that is the part thereof that is adapted to engage said valve seat means when said piston is in said first position thereof, said housing means having a cyiindrical chamber therein that leads to said valve seat means and has substantially the same sized circular transverse cross-sectional configuration from one end thereof to the other end thereof, said valve seat means being substantially frusto-conical with the larger base thereof being the SW 910412nspe.008,25326.claJ4 -L same size as said circular transverse cross-sectional configuration and joining with said chamber at one of said ends thereof, said piston being disposed in said chamber for movement therein between said positions thereof.

2. An expansion device as set forth in claim 1, wherein said grooves each interrupt said first end surface means and said second end surface means of said piston. said first end surface means of said piston comprises an outer annular section surrounding said hemispherical f section.

4. An expansion device as set forth in claim 3, wherein said outer section of said first end surface means of said piston is frusto-conical with the smaller base thereof joining said hemispherical section and the larger base thereof joining said outer peripheral surface means. o: 5. An expansion device as set forth in claim 4, wherein said grooves interrupt only said outer annular section of said first end surface means of said piston.

6. An expansion device as set forth in claim 5, wherein said grooves each has a bottom that is spaced outwardly from the larger base of said hemispherical section of said first end surface means of said piston at the point where the respective groove interrupts said outer annular section thereof.

7. An expansion device as set forth in claim 2, wherein said second end surface means of said piston is substantially flat and is disposed substantially transverse to a longitudinal axis of said piston. 9o4Zg insp.o82332&cl,15 -16-

8. An expansion device as set forth in claim 7, wherein said grooves each has a bottom surface that has two substantially straight sections one of which is disposed substantially parallel with the axis of said piston as said one section extends from said first end surface means to the other section which is angled toward said axis of said piston as said other section extends from said one section thereof to said second end surface means of said piston.

9. An expansion device as set forth in claim 8, wherein said grooves each has a substantially rectangular transverse cross-sectional configuration throughout the length thereof. i. 10. An expansion device as set forth in claim 9, wherein said grooves each has a width that is narrower than the transverse arcuate distance on said outer peripheral surface means between adjacent grooves.

11. An expansion device as set forth in claim 9, wherein the length of the diameter of said outer peripheral surface means is approximately seven times the length of the width of each of said grooves.

12. An expansion device as set forth in claim 9, wherein said grooves each has a width that is approximately 0.062 of an inch.

13. An expansion device as set forth in claim 12, wherein said piston has five of said grooves, said outer peripheral surface means having a diameter of approximately 0.460 of an inch, said piston having a length of approximately 0.500 of an inch. i\ 14. A piston for an expansion device for a refrigeration 910412 spe. ,2532 16 91O4IZL~Jn.oSpC.08226d16 AO_ I -17- system wherein the device has a housing means provided with opposed port means for coupling said device in said system and being separated from each other by an internal valve seat means of said housing means, said piston being adapted to be disposed in said housing means and have a first end surface means adapted to engage against said valve seat means to tenc to close the same when said piston is disposed in a first position thereof in said housing means, said piston having a second end surface means adapted to engage against an annular shoulder means c9 said housing means wherein said piston is disposed in I a second position thereof in said housing means, said piston having a passage means passing therethrough and through said end surface means thereof for interconnecting said opposed port means together in a restricted manner when said piston is in said first .i *position thereof, said piston having an outer peripheral surface means interconnecting said end surface means together and being provided with a plurality of grooves therein for interconnecting said opposed port means •together in a substantially non-restricted manner when e said piston is in said second position thereof, said piston comprising a one-piece member of polymeric material and said first end surface means of said piston having a substantially hemispherical section that is the part thereof that is adapted to engage said valve seat means when said piston is in said first position thereof, -said grooves each interrupting said first end surface means and said second end surface means of said piston, said second end surface means of said piston being substantially flat and being disposed substantially transverse to a longitudinal axis of said piston, said grooves each having a bottom surface that has two substantially straight sections, one of which is disposed substantially parallel with the axis of said piston as said one section extends from said first end surface Q914ZMlgjnspe.008,5326.1a,17 v -18- means to the other section, which is angled toward said axis of said piston as said other section extends from said one section thereof to said second end surface means of said piston. A piston for an expansion device as set forth in claim 14, wherein said grooves each has a substantially rectangular cross-sectional configuration throughout the length thereof.

16. A piston for an expansion device as set forth in claim 14, wherein said first end surface means of said a piston comprises an outer annular section surrounding r said hemispherical section.

17. A piston for an expansion device as set forth in claim 16, wherein said outer section of said first end surface means of said piston is frusto-conical with the smaller base thereof joining said hemispherical section and the larger base thereof joining said outer peripheral eI surface means.

18. A piston for an expansion device as set forth in claim 17, wherein said grooves interrupt only said outer annular section of said first end surface means of said piston. *19. A piston for an expansion device as set forth in claim 18, wherein said grooves each has a bottom that is spaced outwardly from the larger base of said hemispherical section of said first end surface means of said piston at the point where the respective groove interrupts said outer annular section thereof. A method for making a piston for an expansion device for a refrigeration system when the device has a housing N" S9141ZJnspe,0 2532cIa18 "a tr; aouts against an internal shoulder 43 of the housing member 34, whereby the shoulder 43 holds the filter J/ ~Y I_ i i -i -19- 6 6, *O *E 6 *i. 6 means provided with opposed port means for coupling said device in said system and being separated from each other by an internal valve seat means of said housing means, said piston being adapted to be disposed in said housing means and have a first end surface means adapted to engage against said valve seat means to tend to close the same when said piston is disposed in a first position thereof in said housing means, said piston having a second end surface means adapted to engage aga ,nst an annular shoulder means of said housing means when said piston is disposed in a second position thereof in said housing means, said piston having a passage means passing therethrough and through said end surface means thereof for interconnecting said opposed port means together in a restricted manner when said piston is in said first position thereof, said piston having an outer peripheral surface means interconnecting said end surface means together and being provided with a plurality of grooves therein for interconnecting said opposed port means together in a substantially non-restricted manner when said piston is in said second position thereof, the method comprising the steps of forming said piston to comprise a one-piece member of polymerical material, forming said first end surface means of said piston to comprise a substantially hemispherical section that is the part thereof that is adapted to engage said valve seat means when said piston is in said first position thereof, forming said grooves to each interrupt said first end surface means and said second end surface means of said piston, forming said second end surface means of said piston to be substantially flat and to be disposed substantially transverse to a longitudinal axis of said piston, and forming said grooves to each have a bottom surface that has two substantially straight sections, one of which is disposed substantially parallel with the axis of said piston as said one section extends from said I f \Fs 91041,g8ns.pe.00S326,cj!9 A first end surface means to the other section, which is angled toward said axis of said piston as said other section extends from said one section thereof to said second end surface means of said piston.

21. An expansion device substantially as hereinbefore described with reference to the accompanying drawings.

22. A piston substantially as hereinbefore described with reference to the accompanying drawings.

23. A method for making a piston substantially as hereinbefore described with reference to the accompanying *e drawings. e* '91 9 4 5 DATED this 12th day of April 1991 5 Robertshaw Controls Company By Its Patent Attorneys DAVIES COLLISON o So•oeo S 5.5. SeO S 5 S* S S 9104lgjrp.008,2532ca,20