US1955728A

US1955728A - Chilling method and tool for expansion fits

Info

Publication number: US1955728A
Application number: US604270A
Authority: US
Inventors: Scott E Allen; Ozro N Wiswell
Original assignee: COLONY MAN CORP
Current assignee: COLONY MAN CORP; COLONY MANAGEMENT Corp
Priority date: 1932-04-09
Filing date: 1932-04-09
Publication date: 1934-04-24
Anticipated expiration: 1951-04-24

Description

April 24, 1934. s. E. ALLEN ET AL CHILLING METHOD AND TOOL FOR EXPANSION FITS Filed April 9, 1952 I 2 Sheets-Sheet l INVENTOR. Scorr E. ALLEN 02/?0 M W/SWELL April 24, 1934. s. E. ALLEN El AL 1,955,728

CHILLING METHOD AND TOOL FOR EXPANSION FITS Filed April 9, 1932 2 Sheets-Sheet 2 A n 7 I J I /0 I06 l a L. I" "341E v 6 i I r INVENTOR. 67/ H 5 Scorr f. ALLEN 65 L OZRO /V. W/SWELL 94 3 5 ATTORNEY.

' then is introduced into the outer member.

- of carbon dioxide.

Patented Apr. 24, 1934 UNITED STATES CHILLING METHOD AND TOOL FOR EXPANSION FITS Scott E. Allen and Ozro N. Wiswell, Los Angeles,

Calif., assignors to Colony Management Corporation, a corporation of New York Application April 9, 1932, Serial No. 604,270

44 Claims.

The present invention relates to the fitting of one member tightly within another or theseparation of members thus fitted together, and has to do more particularly with expansion fits as distinguished from shrink" fits.

A shrink fit is made by thermally expanding an outer member until an inner member can be inserted therein, and then permitting the outer member to cool so that it will shrink upon the inner member. The parts may be separated by reheating and thus expanding the outer member so as to release its hold on the inner member. In making an expansion fit, on the other hand, the inner member is contracted by chilling it and The inner member is then allowed to absorb heat from its surroundings so that it will expand to its normal dimensions and fit tightly within the outer member. To separate the parts the inner member is again chilled and thereby contracted until it can be drawn or forced out of the outer member. Obviously this method of separating the parts by refrigeration of the inner member may be em ployed whether the fit was originally made shrinkage or expansion.

The present invention has for an object to provide a novel method of chilling an inner member and thereby contracting the same, either to make an expansion fit or to separate the inner member from an outer member in which it is tightly seated whether it was so seated by expansion thereof or by contraction of said outer member.

The usual refrigerant employed in chilling an inner member is carbon dioxide liquefied under pressure. As is well-known a jet of this liquid on being released into the atmosphere flashes instantly into gas and in so doing absorbs an enormous amount of heat. Heretofore such jets have been used in chilling the inner members either in making or separating expansion fits.

In separating an expansiqn fit, it is essential that the inner member be chilled very rapidly so that it will cool much more rapidly than the outer member. The joint between the two members is a bar to the transfer of heat from one member to the other, and this bar becomes incrcasingly effective as the inner member shrinks away from the outer member and opens up said joint. While rapid chilling may be obtained by blowing streams of the gas against the inner member, so that the latter will be constantly brushed by fresh volumes of frigid gas, such a procedure necessarily involves considerable waste We have found that a more efiicient method is to employ the refrigerant not in the form of a gas, but in the form of a wet snow. We are aware that efiorts have been made to convert the carbon dioxide into snow for shrinkage purposes by using screens or other means to restrict the free .discharge of the jets, but carbon dioxide snow loses much ofits efficiency as a chilling medium because it is apt to be very dry.

An object of the present invention is to provide a novel method of producing a dense and wet snowof very low temperature and forming it in intimate contact with the member to be contracted, so as to effect a rapid transfer of heat therefrom. We have found that with such a snow not only will the member be more rapidly chilled, but it will also be reduced to a lower temperature with a correspondingly greater shrinkage. Such a wet snow, we produce by mixing with the carbon dioxide certain liquids of low freezing point such, for instance, as alcohol, ether, etc.

However, while we prefer to use carbon dioxide our invention also contemplates the use of other highly compressed refrigerants, such as are well known in the art, and with which liquids of low freezing point may be mixed to produce a dense wet snow.

Another object of our invention is to provide a method of preventing condensation of atmospheric moisture on the member that is chilled preparatory to insertion thereof into the outer member, so as to prevent corrosion after the expansion fit has been made.

Our invention has for a further object to provide means for producing the desired mixture and applying it in the form of snow upon the member to be shrunk.

Another object of the invention is to provide a novel chilling tool adapted to be applied to the member to be shrunk and in which the actual contact between the tool and the member is reduced to a minimum.

Another object of the invention is to provide novel means for securing the member to the tool so that it can be introduced into and removed from the outer member.

Other objects and advantages of the invention will appear in the following description of our improved method and several embodiments of the means for carrying out the same, and thereafter the novelty and scope of the invention will be pointed out in the claims.

In the accompanying drawings;

Figure 1 is a view in section of a chilling tool employed in removing or inserting an expansion fit bushing;

Fig. 2 is a view in section taken on the line 2--2 of Fig. 1;

Fig. 3 is a fragmental view in section illustrating a manually controlled means for holding the bushing on the tool; v

Fig. 4 is a view in section taken on the line trating a pneumatic means for controlling the holding device;

Fig. 6 is a view in longitudinal section of a different form of chilling tool;

Fig. 7 is a view in section of another form of tool head;

Fig. 8 is a view in transverse section of still another form of tool head, the section being taken on the irregular line 8-8 of Fig. 9;

Fig. 9 is a view in section taken substantially on the line 9-9 of Fig. 8;

Fig. 10 is a view in longitudinal section of a tool for removing long bushings or liners; and

Fig. 11 is a view in section taken on the line 11--11 of Fig. 10.

The chilling tool shown in Figs. 1 and 2 is adapted to remove a bushing 15 from or insert it into a seat in an outer member 16. The body 18 of the chilling tool is provided with a pair of spaced annular flanges 19 and 20 respectively and between these flanges is formed an annular recess 21. As will be explained hereinafter, this recess serves as an expansion chamber in which the snow is formed. The outer flange 19 is of a diameter to pass freely through the bushing, while the inner flange 20 is formed with an outwardly flaring annular shield or apron 22 which is adapted to bear against the adjacent edge of the bushing. The bushing isheld upon the tool head by means of a number of balls 23 which are movable in sockets 24 formed in the flange 19. These balls are urged outwardly by springs 2411, but are prevented from escaping from the sockets by peening the sockets slightly at their outer edges. The arrangement is such that when the tool head is inserted into the bushing the balls will be depressed into the sockets and then, as they clear the farther edge of the bushing, will snap outwardly to overlap and retain the bushing on the tool head. However, the hold of the balls on the bushings will not be such as to prevent the tool from being withdrawn from the bushing by the exercise of a certain amount of force.

The tool head is provided with a central'mixing chamber 25. This chamber is formed by boring or otherwise forming a recess in the tool head on the under side thereof, as shown in Fig. 1, and then closing the mouth of the recess by means of a screw plug 26. A cup-shaped strainer 27 is preferably fitted into the chamber 25 and a quantity of absorbent material 28 is packed within the strainer. An inlet pipe 29 is screwed into the plug and it communicates through an inlet port 30 with the chamber 25. Through this pipe the carbon dioxide is admitted to the mixing chamber from a source (not shown) of liquefied carbon dioxide' An inlet port 31 is provided in the outer wall of the chamber. A nipple 32 is screwed into this .port and carries a spring-pressedcheck valve 33 which opens toward the chamber. This provides means for introducing alcohol, or other liquid into the absorbent material. Leading radially outwardly from the mixing chamber are two opposed nozzles 34 through which the mixture in the chamber 25 may be directed into the annular snow chamber 21. A pair of vents 35 are provided through which the fluid introduced into the snow chamber may escape. These vents are preferably disposed at angles of substantially degrees from the nozzles 34 and diverge from parallel to the axis of the tool so as to direct the discharge under the apron 22. The divergence of these vents and their relation to the apron is illustrated in Figs. 3 and 5.

It is desirable to provide as little actual contact between the bushing and the tool head as possible, so that the bushing will be substantially heat insulated from the tool head and the transfer of heat will take place from the bushing directly into the snow formed in the expansion chamber 21. The particular bushing chosen for illustration is one which is formed with a bevelled lower edge and the angle of the apron 22 conforms substantially to the angle of this bevel. However, grooves 36 are cut in the outer face of the apron so as to provide line contacts between the apron and the bushing. The upper flange 19 is also preferably formed with a groove 37 so as to reduce as much as possible the area of contact between this flange and the bushing.

To assist in holding thetool a handle 38 is provided which is threaded into a socket formed in the upper part of the tool head. The socket for the handle extends into the mixing chamber and may be of the same diameter and thread as that of the socket for the inlet pipe 29, so that whenever desired the tool head may be reversed by screwing the handle into the socket for the inlet pipe and the inlet pipe into the socket for the handle.

In operation, assuming that it is desired to remove the bushing 15 from its seat in the member 16, the tool head is forced through the bushing until the balls 23 snap past the upper edge of the bushing. The mixing chamber having been previously charged with a small amount of ethyl alcohol, or other suitable liquid of low freezing point, carbon dioxide is then admitted into the mixing chamber through the inlet pipe and it streams out in jets from the mixing chamber through the nozzles 34. The carbon dioxide carries with it a vaporous charge of the liquid in the mixing chamber and immediately produces a dense wet snow in the recess 21. The surplus gas escapes through the vents 35 and is directed by the apron 22 away from the outer member 16, so that the latter is not chilled by this expanding gas. The recess 21 very rapidly becomes packed with snow, and since this snow is in direct contact with the bushing the latter is immediately chilled. In a few seconds time, depending upon the size and shape of the bushing, the latter will be shrunk sufficiently to permit of withdrawing it from its seat. The grooved surfaces of the flanges 19 and 20 do not form gas tight joints with the bushing, particularly before the latter has been shrunk, but, they are quickly closed by the mass of snow formed in the recess. As the bushing shrinks it clings more tightly to the tool head, but because of the poor contact between the bushing and the tool head there is little transfer of heat between the tool head and the bushing and most of the heat transfer takes place between the bushing and the snow in the recess 21. In other words, because of the

grooves

36 and 37 it is not necessary to chill the entire tool head before the bushing itself is chilled sufficiently to release it from its tight fit in the member 16.

To introduce a bushing into its seat in the member 16, said bushing is shrunk, in the manner described above, upon the tool head, after which the feed of carbon dioxide into the tool'is cut off by means not shown. The bushing is then inserted into its seat, and is allowed to remain in position until it has expanded sufliciently to grip its seat before the tool head is withdrawn.

When chilling the bushing 15 preparatory to inserting it in its seat in the member 16 atmospheric, moisture will condense thereon and accumulate in the form of frost. This frost if allowed to remain on the bushing is likely. to cause corrosion after the bushing has been fitted in its seat. We have found that the frost can be removed by wiping the bushing with a cloth wet with alcohol, and also that if the bushing is wet with alcohol before the chilling process no frost will form thereon. It is therefore a part of our process either to remove the frost or prevent its formation on the bushing by the use of a suitable liquid whose freezing point is lower than the temperature of the object.

When removing a bushing from its seat, it may be necessary to exert considerable force, even after the bushing has been shrunk, and instead of relying upon spring-pressed balls to hold the tool upon the bushing it is sometimes necessary to employ a more positive holding means. Such a means is shown in Figs. 3 and 4. The tool head in this case is similar to that shown in Fig. 1, but in place of the balls 23 round-ended pins or plungers are used, which are slidable in radially disposed sockets 41. These pins are normally held in retracted position by flat springs 42 which engage notches in the pins and are seated in an annular recess 43 formed in the upper face of the tool head. Each pin 40 may be forced outwardly against the tension of the spring by means of an adjusting screw 44 threaded into a hole 45 passing through the tool head and into which the inner end of the pin 40 normally projects. The screw 44 has a pointed end which engages the rounded inner end of the pin so that as the screw is fed into the hold 45 it will force the pin 40 outwardly. A cover plate 46 is secured to the tool head to close the recess 43 and the holes 45. With a tool head of this sort the screws 44 are turned back, permitting the pins 40 to recede under the urge of the springs 42. With the pins thus retracted the tool head may be inserted into the bushing and thereafter the screws 44 may be turned up to force the pins outwardly so as to clamp the bushings between said pins and the apron of the tool head. With the bushing thus clamped considerable force may be exerted to withdrawit from its seat.

Another method of forcing the pins outwardly into clamping position is shown in Fig. 5. Here instead of employing adjusting screws, the pressure of the refrigerant is used to force the pins outwardly. "The construction of the head is the same as that shown in Figs. 3 and 4 except that the holes 45 and screws 44 are dispensed with. The pins 40 slide with a close fit in sockets 41 and from the annular snow chamber 21 a small passage 47 leads to the inner end of each socket 41.

Thus, when the refrigerant is admitted into the mixing chamber 25 it will generate a pressure in the sockets 41 back of the pins 40, forcing the latter outwardly against the pressure of the springs 42. As long as the gas pressure is applied these pins will be forced outwardly under high pressure and considerable force may be exercised to withdraw the bushing from its seat. However,

when it is desired to release the tool head from.

shown in Figs. 1 and 2, mainly in the fact that a lafger mixing chamber is provided, said chamber being formed in a stem of the tool rather than in the tool head itself. The tool head is similar in general construction to the one previously described, comprising upper and lower flanges 49 and 50, between which is formed an annular recess or snow chamber 51. Four ports 52 lead radially from a central distributing chamber 53 to the snow chamber 51. The mixing chamber is formed in a tubular stem 55 which is screwed into the under side of the tool head, as viewed in Fig. 6. A nozzle 56 opens from the mixing chamber into the distributing chamber 53. The mixing chamber is filled with absorbent material 57 and ,to prevent this from blowing into and clogging the nozzle the latter is protected by a screen 58. Threaded into one side of the casing 55 is a cup 60 through which alcohol or other liquid may be introduced into the absorbent material 57. A valve 61 normally closes communication between the cup and the magazine chamber. Carbon dioxide is led into the mixing chamber from a bottle of liquefied carbon dioxide through a flexible tube 62 which is provided with a coupling nipple 63 screwed into the lower end of the casing 55. On the side of the tool head opposite the casing 55 is a threaded socket which opens into the distributing chamber and in this socket is screwed a handle 64.

The operation of this tool is like that described above. Carbon dioxide passing through the mixing chamber 57, picks up a certain amount of the liquid contained therein and carries it through the nozzle 56 into the chamber 53, whence it is discharged through the ports 52 into the annular recess 51 where it forms a dense wet snow against the inner periphery of the bushing. It will be understood that the snow chamber is provided with vents (not shown) for the escape of surplus gas. The principal difference between the construction shown in Fig. 6 and that in Figs. 1 and 2 is that a larger mixing chamber is provided and more space is provided for expansion of the refrigerant in the tool head. A single nozzle discharges into the central distributing chamber 53, so that some expansion takes place before the snow chamber 51 is reached. With this arrangement a snow chamber of greater radial depth is permissible and the space in which the mixture can expand is much greater than that provided in the construction shown in Figs. 1 and 2, so that for certain purposes a somewhat more efficient use of the refrigerant may be obtained.

The tool shown in Fig. 7 is in some respects similar to that shown in Fig. 6. However, a more compact mixing chamber is provided and the mixture is fed without appreciable expansion up into the tool head, whence it is discharged through a plurality of ports directly into the annular recess or expansion chamber. The tool head has a central intake port '71 into which is screwed a bell-shape fitting 72. Within this fitting, the mouth of which is closed by a plug 73, is the mixing chamber. Screwed into this plug is an intake pipe 74 through which carbon dioxide is fed into the mixing chamber. The mixing chamber is filled with absorbent material and a screen '75 in the neck of the fitting serves to retain the absorbent material in the mixing chamber. At one side of the fitting there is an inlet port closed by a thumb screw 76 and through this port may be admitted the liquid which is to be mixed with the carbon dioxide.

Four small ports or nozzles 77 lead from the port '71 radially into the annular expansion chamber 78. Vents 79 lead from the expansion chamber downwardly (as shown in Fig. 7) and outwardly to discharge surplus gas from the expansion chamber. These vents are shown in the drawings as lying in the plane of the ports '77, but they may also be arranged in staggered relation therewith. As shown in the drawings the vents open just within the apron 80 of the tool head and the latter serves to shield the member 16 from the cooling effect of the expanding gas.

The tool shown in Figs. 8 and 9 differs from the tools described above, mainly in the provision of jacketing chambers at opposite sides of the snow chamber. The tool comprises a head formed with inner and outer flanges and 86 respectively, between which is an annular recess 8'7 constituting the snow chamber. The inner flange 85 is formed with a bevelled edge adapted to bear against the edge of the bushing 15 while the outer flange 86 is of a diameter to pass readily through the bushing. In the drawings no means for attaching this tool to the bushing is shown, but any suitable attachment devices may be employed, such, for instance, as the spring-pressed balls 23 of Fig. 1 or the pins 40 of Figs. 3 to 5.

The outer flange 86 is recessed to form a cooling chamber 88 which is closed by a plate 89. The latter may be secured in any suitable man ner to the body of the tool, as for instance by welding. The inner flange is similarly formed with a recess to provide a cooling chamber 90 which is closed by a plate 91. The latter may be clamped to the tool head by a nut 92 threaded upon a central boss 93 projecting from the tool body through an aperture in said plate.

The boss 93 is centrally bored and internally threaded to receive the threaded neck of a fitting 94. The latter may be of the same construction as the fitting '72 in Fig. 7, and provides a mixing chamber for the highly compressed refrigerant and the liquid of low freezing point. The bore of the boss 93 is extended into the body of the tool and the mixture from the mixing chamber is led through this bore to a nozzle 95 which opens into the snow chamber 87. Ports 96 and 9'7 lead from the chamber 87 to the

chambers

88 and 90 respectively. Ducts 98 lead through the body of the tool from chamber 88 to chamber 90, and discharge ports 99 are formed in the plate 91.

In operation, the mixture which issues from the nozzle 95 expands first in the snow chamber 8'? and then expands further in

chambers

88 and 90. Obviously, the size of the snow chamber is limited by the size of bushing to be chilled, but in this tool the

auxiliary expansion chambers

88 and 90 provide for increased expansion of the refrigerant and the cooling effect of the expansion in the auxiliary chambers results in a more rapid chilling of the main chamber and a more rapid production of snow therein. In fact, snow also forms in the auxiliary chambers. The excess gas in chamber 88 escapes through the vents 98 which, being formed in the body of the tool head are kept comparatively warm and hence do not clog with snow. The excess gas from chamber 90 discharges directly into the atmosphere through the ports or vents 99.

The combined volume of the main expansion chamber 8'7 and the auxiliary expansion chambers is proportioned to provide almost complete expansion of the mixture issuing through the nozzle 95, so that there is very little pressure left in the gas that discharges from the vents 99.

As a result, this tool is very eflicient in its use of refrigerant and will chill the ring 15 to a lower temperature in a given time than will the tool shown in Fig. 7. Furthermore, the expansion by stages and the lower final pressure in the discharge permits of using thinner chamber walls, and consequently there is a smaller mass of metal in the tool head to be chilled.

The construction shown in Figs. 10 and 11 is particularly adapted for shrinking long bushings or sleeves. member 100 within which is fitted a long tubular bushing 101. The head of the chilling tool used in fitting the bushing into the member 101 or removing it therefrom, comprises a cylindrical body 102 formed with flutes 103 between which are disposed flutes 103a. The body 102 is of a size to be passed freely through the bushing 101 and is formed near its inner end with a shoulder 104 which is adapted to bear against the adjacent end of the bushing. The opposite end of the body 102 has an extension 105 of reduced diameter upon which'is threaded a removable cap 106. This cap overlaps and bears against the outer end of the bushing 101 so that the bushing is thus clamped between the cap 106 and the shoulder 104. The flutes 103 and 1030. are shorter than the bushing and are covered thereby. At their outer ends the flutes are intercepted by an annu- In the drawings, I show an outer lar channel 107. At their inner ends flutes 103 are provided with discharge vents 108 which lead outwardly and rearwardly from the tool head, while the intermediate flutes 103a are provided at their inner ends with inlet nozzles 109 which are connected by ports 110 to a mixing chamber 112. The latter is similar in every respect to the mixing chamber shown in Fig. 7.

In operation, the mixture of carbon dioxide and the liquid introduced into the mixing chamber, is forced by the pressure of the carbon dioxide, through the nozzles 109 into the flutes 103a. The refrigerant expands into a gas which flows to the outer ends of these flutes and thence passes through the annular groove 10'? into the other flutes 103 and returns to the rear end of the tool, discharging through the vents 108. The course of the refrigerant is indicated by the arrows in Fig. 10. As a result of this expansion, the flutes are soon filled with a densely packed wet snow which chills the bushing 101 uniformly throughout its length and permits of withdrawing it from the member 100. Because the bushing is firmly clamped between the cap 106 and the shoulder 104, considerable force may be exerted to drive the bushing out of the member 100 should it not contract suffioiently to permit of easy withdrawal.

While we have described a number of tools with which our improved method can be carried out, these are to be taken as illustrative and not limitative and we reserve the right to make various changes in form, construction and arrangement of parts, as well as in mode of operation and in refrigerants employed, without departing from the spirit and scope of the following claims.

We claim:

1. A method of contracting an object to permit of introducing it into or removing it from a tight fitting seat, which consists in mixing a fluid of low freezing point with a highly compressed fluid refrigerant, and expanding the mixture in thermal contact with the object to form a snow and thereby chill the object.

2. A method of contracting an object to permit of introducing it into or removing it from a tight fitting seat, which consists in mixing a liquid of 16w freezing point with liquefied -carbon dioxide,.

expanding the mixture in'thermal contact .with the object to form a snow, and thereby chilling the object.

i 3. A method of contracting an object to permit of introducing it into or removing it from a tight fitting seat, which consists in conducting to the vicinity of the object a refrigerant liquefied under pressure, introducing into the refrigerant an- 1 other liquid of low freezing point, and expanding the mixture in contact with the object so that at least part of the mixture will solidify in the form of snow upon the object and thereby chill the same.

S 4. A method of contracting an object to permit of introducing it into or removing it from a tight fitting seat, which consists in conducting liquefied carbon dioxide to the vicinity of the object, introducing into the carbon dioxide a flud of low freezing point, and expanding the mixture in contact with the object so that at least part of the mixture will solidify in the form of snow upon the object and thereby chill the same.

5. A method of contracting an object to permit 5 of introducing it into or removing it from a tight fitting seat, which consists in forming a jet of liquefied carbon dioxide, introducing into the jet a fluid of lower freezing point than that of the carbon dioxide, and applying the jet to the object 1 so as to form snow on the object and chill the same.

6. A method of contracting an object to permit of introducing it into or removing it from a tight fitting seat, which consists in passing a stream of 5 highly compressed carbon dioxide through a i same.

'7. A method of contracting an object to permit of introducing it into or removing it froma tight fitting seat, which consists in conducting a stream of carbon dioxide to the vicinity of the object 5 from a body of carbon dioxide maintained as a liquid under pressure, introducing into said stream a liquid 'of low freezing point, and thereafter expanding the stream in contact with the object to form snow onthe object and thereby i chill the same.

8. A method of contracting an object to permit of introducing it into or removing it from a tight fitting seat, which consists in conducting a stream of carbon dioxide to the vicinity of the object 3 from a body of carbon dioxide maintained as a liquid under pressure, introducing into the stream a quantity of alcohol, and thereafter expanding the stream in contact with the object to form snow on the object and thereby chill the same.

i. 9. A method of contracting an object to permit of introducing it into or removing it from a tight fitting seat which consists in mixing ethyl alcohol with liquefied carbon dioxide, and expanding the mixture in contact with the object to form snow thereon and thereby chill the object.

10. A method of contracting an object to permit of introducing it into or removing it from a tight fitting seat which consists in mixing ether with liquefied carbon dioxide, and expanding the mixture in contact with the object to form snow thereon and. thereby chill the object.

'11. A method of contracting a hollow object which consists in mixing a liquid of low freezing point with a highly compressed refrigerant, and expanding the mixture within the object to form snow on the interior surface of the object and thereby chill said object.

12. A method of contracting an object to permit of introducing it into or removing it from a tight fitting seat, which consists in expanding a highly compressed fluid refrigerant in a plurality of stages, exposing the object directly to the expanding refrigerant in the first stage so as to chill the object, and using the expanding refrjgerant in the subsequent stages to jacket and thereby super-refrigerate the refrigerant eipanding in the first stage.

13. A method of contracting an object to permit of introducing it into or removing it from a. tight fitting seat, which consists in introducing into a highly compressed fluid refrigerant a liquid of low freezing point higher than that of the refrigerant, expanding the refrigerant in a plurality of stages, exposing the object to the expanding refrigerant in the first stage to form snow on the object and thereby chill the same, and using the refrigerant expanded in the subsequent stages to jacket and thereby superrtefrigerate the refrigerant expanding in the first s age.

14. A tool for contracting an object by chilling the same, said tool comprising a head formed with a normally open chamber adapted to be closed by the object, means for conducting a stream of refrigerant into the chamber, and means for introducing a fluid of low freezing point into the stream.

15. A tool for contracting an object by chilling the same, said tool being formed with a mixing chamber and with a normally open expansion chamber adapted to be closed by the object, a conduit for leading a stream of highly compressed fluid refrigerant into the mixing chamber, means for introducing another fluid of low freezing point into the mixing chamber, and a port leading from the mixing chamber into the expansion chamber.

16. A tool for contracting an object by chilling the same, said tool comprising a head formed with a mixing chamber therein and with a normally open expansion chamber adapted to be closed by the object, a conduit for leading a. stream of highly compressed fluid refrigerant into the mixing chamber, means for introducing a liquid of low freezing point into the chamber, a port leading from the mixing chamber into the expansion chamber.

17.' A tool for contracting an object by chilling the same, said tool comprising a. head formed with a normally open expansion chamber adapted to be'closed by the object, the tool being also formed with a mixing chamber adapted. to contain a quantity of absorbent material, means for introducing a liquid into the absorbent material, and means for passing a stream of highly compressed fiuid refrigerant through the mixing chamber into the expansion chamber.

18. A tool for contracting an object by chilling the same, said tool comprising a head formed with a normally open expansionchamber adapted to be closed by the object, the tool being also formed with a mixing chamber adapted to contain a quantity of absorbent material, a port connecting the two chambers, a screen for said port, a filling port through which liquid may be 145 introduced into the absorbent material, and means for conducting highly compressed fluid refrigerant into the mixingchamber.

19. A tool for contracting an object by chilling the same, said tool comprising a head formed 150 with a normally open expansion chamber adapted to be closed by the object and with vents leading out of said chamber, the tool being also formed with a mixing chamber adapted to contain a quantity of absorbent material; a port connecting the two chambers, a screen for said port, an inlet port through which liquid may be introduced into the absorbent material, and means for conducting highly compressed fluid refrigerant into the mixing chamber.

20. A tool for contracting an object by chilling the same, said tool comp-rising a head formed with a normally open expansion chamber adapted to be closed by the object and with vents leading out of said chamber, the tool being also formed with a mixing chamber adapted to contain a quantity of absorbent material, a port connecting the two chambers, a screen for said port, an inlet port through which liquid may be introduced into the absorbent material, means for conducting highly compressed fluid refrigerant into the mixing chamber, and means for attaching the tool to the object.

21. A tool for contracting a hollow object by chilling the same, said tool comprising a head adapted to be fitted within the object, said head being formed with an annular recess constituting an expansion chamber and adapted to be closed by the object, said tool being also formed with a mixing chamber, means for charging the mixing chamber with a liquid, and means for passing the highly compressed fluid refrigerant through the mixing chamber into the expansion chamber.

22. A tool for contracting a hollow object by chilling the same, said tool comprising a head adapted to be fitted within the object, said head being formed with an annular recess constituting an expansion chamber and adapted to be closed by the object, said tool being also formed with a mixing chamber, means for charging the mixing chamber with a liquid, means for passing the highly compressed fluid refrigerant through the mixing chamber into the expansion chamber, and means in the mixing chamber for intermixing said liquid and said refrigerant.

23. A tool for contracting a hollow object by chilling the same, said tool comprising a head adapted to be fitted within the object, said head being formed with an annular recess constituting an expansion chamber and adapted to be closed by the object, a hollow casing secured to the head and providing a mixing chamber adapted to be filled with absorbent material, a port providing a communication between the mixing chamber and expansion chamber, a filling port for the mixing chamber, and means for conducting highly compressed fluid refrigerant into the mixing chamber.

24. A tool for contracting a hollow object by chilling the same, said tool comprising a head adapted to be fitted Within the object, said head being formed with an annular recess constituting an expansion chamber and adapted to be closed by the object, a hollow casing secured to the head and providing a mixing chamber adapted to be filled with absorbent material, a port providing communication between the mixing chamber and expansion chamber, a screen over the port in the mixing chamber, a filling port for the mixing chamber, and means for conducting highly compressed fluid refrigerant into the mixing chamber.

25. A tool for chilling an annular object, said tool comprising a head adapted to be inserted in the object and having a shoulder adapted to seat against one end of the object, clamping means on the head for engaging the opposite end of the object, the head being formed with a peripheral recess adapted to be closed by the object and constituting an expansion chamber, the head being also formed with a threaded opening extending through opposite faces thereof, and with a passage leading from said opening into the expansion chamber, a refrigerant supply means adapted to be screwed into said opening from either face of the head, and a handle adapted to be screwed into the opening from the opposite face of the head.

26. A tool for chilling an annular object, said tool comprising a head adapted to be inserted into the object and formed with grooved bearing surfaces adapted to engage the object, the head being formed with a peripheral recess between said surfaces and adapted to be closed by the object to form a refrigerating chamber, and means for introducing a fluid refrigerant into said chamber.

27. A tool for chilling an annular object, said tool comprising a head formed with spaced peripheral flanges providing therebetween, a refrigerating chamber adapted to be closed by the object, one flange having a grooved seating surface adapted to engage one edge of the object, the other flange being of a size to pass through the object, spring-pressed means carried by the latter flange and adapted to overlap the other edge of the object, and means for introducing a fluid refrigerant into said chamber.

28. A chilling tool for removing a bushing from its seat in an encircling member, said tool comprising a head adapted to be inserted into the bushing, said tool being formed with a peripheral expansion chamber opening against the inner periphery of the bushing and with vents for said chamber opening through one face of the head, means for introducing a highly compressed fluid refrigerant into said chamber, and means on said face of the head to shield said member from'the refrigerant discharging from said vents.

29. A tool for chilling an annular object, said tool comprising a head adapted to be inserted into the object and formed with a shoulder adapted to seat against one end of the object, plungers carried by the head and movable to overlap the opposite end of the object, resilient means normally holding the plungers in retracted position, and means for advancing the plungers to overlapping position, the head being formed with a refrigerating chamber and with means for introducing a refrigerant therein.

30. A tool for chilling an annuar object, said tool comprising a head adaptedto be inserted into the object and formed with a shoulder adapted to seat against one end of the object, plungers carried by the head and movable to overlap the opposite end of the object, resilient means normally holding the plungers in retracted position, and manually operable means for advancing each plunger to overlapping position, the head being formed with a refrigerating chamber and with means for introducing a refrigerant therein.

31. A tool for chilling an annular object, said tool comprising a head adapted to be inserted into the object and formed with a shoulder adapted to seat against one end of the object, plungers movable to overlap the opposite end of the object, the head being formed with cylindrical sockets in which the plungers are fitted to slide, spring means urging the plungers to retracted position, the head being also formed with a peripheral expansion chamber adapted to be closed by said object and with ports leading from the chamber to the inner end of each socket, and means for injecting a highly compressed fluid refrigerant into said chamber.

32. A tool for chilling an object, said tool comprising a head formed with a normally open main expansion chamber adapted to be closed by the object, the head being also formed with an aux iliary expansion chamber jacketing the main expansion chamber, each chamber being provided with a discharge port, and means for imecting highly compressed fluid refrigerant into said chambers.

33. A tool for chilling an object, said tool comprising a head formed with a normally open main expansion chamber adapted to be closed by the object, the head being also formed with a pair of auxiliary expansion chambers jacketing the main chamber on opposite sides thereof, discharge ports leading from the main chamber into the auxiliary chambers and discharge ports leading out of the auxiliary chambers, and means for injecting a highly compressed fluid refrigerant into the main chamber.

.34. A tool for chilling an annular object, said tool comprising a head adapted to be inserted in q the object and formed with a peripheral recess adapted to be closed by the object to form a main expansion chamber, the head being also formed with auxiliary expansion chambers disposed on opposite sides of the main chamber and with ports opening from the main chamber into the auxiliary chambers, the latter being also provided with discharge ports, and means for injecting a highly compressed fluid refrigerant into the main chamber.

35. A tool for chilling an annular object, said tool comprising a head adapted to be inserted in the object and formed with a peripheral recess adapted to be closed by the object to form a .main expansion chamber, the head being also formed with auxiliary expansion chambers disposed on opposite sides of the main chamber and with ports opening from the main chamber into the auxiliary chambers, the latter being also provided with discharge ports, a nozzle opening into the main expansion chamber, and means for injecting a highly compressed fluid refrigerant into the nozzle.

36. A tool for chilling an annular object, said tool comprising a head adapted to be inserted in the object and formed with a peripheral recess adapted to be closed by the object to form a main expansion chamber, the head being also formed with auxiliary expansion chambers disthe object, the head being also formed with an annular recess interconnecting the flutes at their f outer ends, intake ports opening into certain of the flutes at their inner ends, discharge ports leading from the other flutes at their inner ends, and means for feeding a highly compressed fluid refrigerant to said intake ports.

38. A tool for chilling a tubular object, said tool comprising a cylindrical head adapted to be fitted into the object and having a shoulder to engage one end of the object, clamping means removably secured upon the head to engage the opposite end of the object, the surface of the head within the object being formed with flutes and with an annular recess interconnecting the flutes at the outer end thereof, nozzles opening into alternate flutes at the inner end thereof, discharge ports leading from the intermediate flutes at the inner end thereof, and means including a magazine chamber for feeding highly compressed fluid refrigerant to said nozzles.

39. A method of making an expansion flt of an object within a member, which consists in conducting a highly compressed fluid refrigerant to the immediate vicinity of the object, expanding the refrigerant in thermal communication with the object to chill and thereby contract the latter, removing any atmospheric moisture condensed and frozen on the chilled object with a liquid whose freezing point is lower than the temperature of the chilled object, and inserting the object while contracted into said member, whereby the object will absorb heat from said member and expand therein.

40. A method of making an expansion fit of an object within a member, which consists in conducting'a highly compressed fluid refrigerant to the immediate vicinity of the object, expand- 11 ing the refrigerant in thermal communication with the object to chill and thereby contract the latter, removing any atmospheric moisture condensed and frozen on the chilled object with alcohol, and inserting the object while contracted into said member, whereby the object will absorb heat from said member and expand therein.

41. A method of making an expansion fit of an object within a member, which consists in moistening the object with a liquid, expanding a highly compressed fluid refrigerant in contact with the object to chill and contract the same, the freezing point of the liquid being lower than the temperature of the chilled object, and inserting the object while contracted in said member, whereby the object will absorb heat from said member and expand therein.

42. A method of making an expansion fit of an object within a member, which consists in moistening the object with alcohol, expanding a highly compressed fluid refrigerant in contact with the object to chill and contract the same, and inserting the object while contracted in said member, whereby the object will absorb heat from said member and expand therein.

43. A method of contracting an object to permit of introducing it into or removing it from a tight fitting seat, which consists in mixing a liquid of low freezing point with liquefied carbon dioxide, expanding the mixture in thermal contact ethyl alcohol with liquefied carbon dioxide, and

expanding the mixture in contact with the object and thereby chilling the object.

SCOTT E. ALLEN.

OZRO N. WISWELL. 15G