US2772716A

US2772716A - Tube-expanding tool

Info

Publication number: US2772716A
Application number: US452571A
Authority: US
Inventors: Walter E Stary
Original assignee: Individual
Current assignee: Individual
Priority date: 1954-08-27
Filing date: 1954-08-27
Publication date: 1956-12-04
Anticipated expiration: 1973-12-04

Description

13% 1956 w. E. STARY TUBE-EXPANDING TOOL Filed Aug. 27, 1954 2 Sheets-Sheet J i I INVENTOR.

Dec. 4, 1956 w. E. STARY 2,772,716

TUBE-EXPANDING TOOL Filed Aug. 27, 1954 2.Sheets-Sheet 2 IN VEN TOR.

United States Patent TUBE-EXPANDING TOOL Walter E. Star-y, Levittown, Pa. Application August '27, 1954, Serial No. 452,571 9 Claims. (Cl. 153-82) This invention relates to improvements in the rollertype tube-expanding tool. This tool is used to expand a linear portion of a metallic tube by a .rolling action to flow the metal so as to thin the tube wall and diametrically enlarge the tube portion to bring it into tight engagement with the tube-hole in which it is being assembled.

A principal use for this tube-expanding tool is to make pressure-tight tube-joints between tubes and headers or between tubes and tube-sheets in heat-exchange apparatus. The tubes in this apparatus range in size from some 10 in'ches to At-inch'outside diameter. However, the greatest portion of the total volume of this tube-expanding work is on tubes 1%-inches, or less, 0. D. A great many of these tubes are /2 or -%-inches 0. D., and for these tubes the tool assemblies are to -inches 0. D.

The usual method of driving the tube-expanding tool is to power rotate thetapered mandrel of the tool while the mandrel is being advanced. The frictional contact between the mandrel and the rollers of the tool transmits rolling forces through the rollers to the tube wall. An apparatus such as shown in my co-pending application, Method and apparatus for expanding tubes, serial number 172,941, filed July 10, 1950, and issued September 28,-19'54, as Pa-tent'No. 2,690,205, may be used to precisely control the actions of the tool so as to obtain uniformly tight tube-joints.

The rolling forces required tothin the tube-wall re main relatively constant-for any particular metal alloy, tube-Wall thickness, and tube-joint length, for a range of tube-diameters. As the tube-diameter decreases, the size of the tool assembly which is to be insertedinto the tube must be decreased and the cross-sectional area of the various tool members decreases. But since the compressive and tensile forces imposed upon the tool parts remain substantially constant the stresses developed in the tool members increases as the tool size decreases.

The more corrosion-resistant alloy tubes with their higher physical-strength properties are becoming increasingly popular. Greater work-producing forces are required to expand these tubes. Also, the continued desire to perform the tube-expanding operation more quickly results in increases in the work-producing forces, because as the time to perform the operation is decreased the magnitude of the force performing the work must increase.

Obviously, as the' forces imposed upon the tool parts increase the stresses developed in the tool members increase proportionately.

A principal object of this invention is to provide an improved design for the roller-cage whereby the crosssectional area of 'the cage is increased to thus obtain a roller-cage of increased strength.

A second advantage resulting from this improved crosssectional shape of the roller-cage is that the rollers may be made smaller and the mandrel proportionately larger to thus obtain a stronger mandrel.

The resultant of the above advantages is that the probability of failure of the tool due to breakage of one of the members is reduced and {the useful life of the tool members is lengthened.

lce

()ther objects and advantages of this improved design will become apparent from the following description. The accompanying drawings illustrate how'this improvement is applied to some of the various styles of rollertype tube-expanding tool assemblies.

Referring to the drawings:

Fig. 1 is a longitudinal section through a tube-expanding tool which can be used to roll and expand a portion of the tube-end together with the members used to 'connect the tool to an apparatus, not shown, for driving and controlling the tool, with the tool inserted in a tube in a tube-hole.

Fig. 2 is a side elevation of a tool generally applied and used the same as the tool shown in Fig. 1, except that the Fig. 2 tool can be used to roll a portion of the tube a preselected distance away from the face of the tubesheet adjacent to the tube-end.

Fig. 3 is a conventional self-feeding type of tubeexpanding tool which can be used to roll a portion of the tube a preselected distance away from the face of the tube-sheet'adjacent to the tube-end.

Fig. 4 is a cross section of the tool assembly of Fig. -1, on the line 44t, with the tool shown entered intoa'tube in its tube-hole in a tube-sheet.

Fig. 5 is the same section as shown in Fig. 4, showing the tube and tool parts, substantially to scale, at the moment during the tube-expanding cycle when the tubewall thinning act-ion is to start. l

Fig. 6 is a cross section of the roller-cage only, taken on the line 66 of Fig. 2 and Fig. 3, showing, to an enlarged scale, the improved shape of the roller-cage, as set forth in this invention.

The tube 1, in Pig. 1, is shown expanded into its tubehole 2-71 in tube-sheet 2 astheexpanding-tool assembly completes the -expandingoperation. Tapered mandrel "3 is advanced to move the several rollers 4 outward radially in roller-cage 5. Rollers 4 are of such a length that the portion in front of (to the left of) the face 5f of theenlarged shank-portion Es-of cage 5 reaches int-o the'tube far enough to roll'the desired maximum-length tube portion. The front end of rollers 4 is formed, in the converi tional manner, to give a gradual transition between the rolled and unrolled portions of the tube. The groove 5g in shank 5s provides a seat for the circular-band portion of spring unit 6 to thus restrict spring unit 6 from axially slipping out of position. The fingers 6 on spring unit 6 bear against and push rollers 4 inwardly to keep them in contact with the mandrel at all times. Thus rollers4 are prevented from falling out of the slots in roller-edge 5.

Threaded shank-portion 5s of roller-cage 5 provides the support for stop-collar assembly 7, and it provides a means of adjus'ting the axial position of stop-collar assembly 7 to thus control the reach of rollers 4 beyond the face of the tube-sheet. Said stop-collar assembly 7 is axially adjusted on'roller-cage '5 by rotating internallythreaded thrust member 8 relative to cage 5. Thus the reach of the tool and the corresponding rolling depth beyond the fatcebf'tube-s-heet 2 may be adjusted from a maximum-depth position with stop-collar assembly 7 rotated to'bring it toward the rear of shank-portion Sr of cage 5 to a minimum-depth position when stopcollar assembly 7 is rotated to bring it: to the forward limit of the thread. Obviously, the furthermost usable rearward position of the's'top-collar assembly is that which brings face 5f of shank 5s on roller-cage 5 near to the face of tube-sheet Z'bu't' clear of the projecting end'of tube 1. Stop-collar assembly 7 is held in the desired position by locking set-screw 9.

Stop-collar assembly 7 is of conventional design with thrust member 8 threadably connected to threaded shank is of roller-cages. Sleeve It? is rotatably vconne'cted to thrust member with an annular seriesof balls 11, be-

tween the mating faces of thrust member 8 and sleeve 14 providing an anti-friction bearing for the axial loads developed when the tool assembly is pushed into the tube or when it is pulled into the tube as the tube is being rolled and expanded. Snap-ring 12 keeps the assembly of sleeve 19, thrust member 8, and the annular series of balls 11 together while providing for relative rotation between sleeve 10 and thrust member 8.

Bearing-flange 13, threadably connected to the rear end of roller-cage 5, serves to connect roller-cage 5, of the tool assembly, to an apparatus for driving and controlling the tool. This driving and controlling apparatus may be one such as is shown in Patent No. 2,690,205, hereinbefore described. With an apparatus of this type, rollercage 5 connects to one member of the apparatus while mandrel 3 connects to some other member of said apparatus. As the apparatus works to drive and control the tool, the mandrel is axially moved relative to the roller-cage, and when these movements occur while a tube-portion is being expanded axial loads of considerable magnitude are imposed on the members connecting rollercage 5 with said driving and controlling apparatus.

Bearing-sleeve 14 provides a connecting means between roller-cage 5 and the above described tube-expanding apparatus. The two axially-spaced annular series of balls, 15, and 16, provide anti-friction bearings for the axial loads in both directions. Back-up ring 17 and snap-ring 18 serve to complete the bearing-unit assembly and to transmit the axial loads developed when the tube-expanding apparatus is pulling the mandrel back to retract the mandrel at the completion of a tube-rolling cycle.

Bearing-sleeve 14 may be threaded, with a thread such as the internal thread shown, to connect to a coupling member 19 which may be used to connect the roller-cage portion of the tool assembly to said tube-expanding apparatus.

Shaft 20 and caging-nut 21 may be used to connect mandrel 3 to said tube-expanding apparatus so as to push and pull the mandrel to produce the axial movements of said mandrel relative to roller-cage 5.

The Fig. 2 tool assembly differs from Fig. l in one principal respect. In Fig. 2, roller-cage 25 is shaped so that a tube-portion some distance away from the tubeend can be rolled and expanded. The entire length of rollers 24 may be inside the tube and some distance from the end of said tube thus preventing the use of a springtype roller retaining device, such as used for the Fig. 1 type of tool assembly. The usual method of retaining the rollers, in this Fig. 2 type of tool assembly, so they do not drop out of the roller-cage slots is to provide caginglips on the edges of the roller-slots, at the outer edges of said slots.

Tapered mandrel 23, in Fig. 2, may be connected to and moved axially by a tube-expanding apparatus, not shown, such as heretofore described in connection with Fig. 1. Stop-collar assembly 27 is threadably connected to threaded shank 25s of roller-cage 25. A groove 25x along threaded shank 25s of roller-cage 25 serves as a seat for set-screw 29 in stop-collar assembly 27 so that setscrew 29 can be locked at various positions along the length of threaded shank 25s without damaging the thread on said shank.

Bearing-flange 13 may be threadably connected to shank 25s to connect roller-cage 25 of this tool assembly to a tube-expanding apparatus, not shown. Bearingsleeve 14, the two axially spaced annular series of balls, 15 and 16, back-up ring 17, and snap-ring 18, serve as in Fig. 1, to connect to parts not shown.

The Fig. 3 tool assembly differs from Fig. 2 in one principal respect. In Fig. 3, the several rollers 34 are caged in slots in roller-cage 35 at a self-feeding angle. This is a conventional type of tool with mandrel 33 being rotated by a power device. In operation, the operator pushes, usually directly on the power device, to advance mandrel 33 to obtain frictional contact between the mandrel, rollers 34, and the inner surface of the tube portion to be expanded. Then, as the mandrel is power rotated, the planetary action of the tool parts and the angular line of contact between rollers and mandrel pulls the mandrel axially forward to expand the rollers and produce the tube-wall thinning action. The mandrel is axially moved backward so as to release the tool at the termination of the tube-expanding operation by rotating said mandrel in a reverse direction.

Fig. 4 shows, to an enlarged scale, a cross-section of tube 1 in tube-hole 2h in tube-sheet 2 before expanding, with clearance between the tube 0. D. and the surface of the the tube-hole. The ligaments, between rollers, of roller-cage 5 are shown in the tube with rollers 4 retracted. The outer surface of the portions of the rollercage shown in Fig. 4 is the conventional circular shape. The usual arrangement is to have rollers 4, in their retracted position, be movable inward, radially, so as to be substantially tangent with the circle describing the outer surface of the roller-cage. Obviously, the diameter of the roller-cage, and the collapsed roller assembly, must be smaller than the inside diameter of the tube in order to easily enter the tool into said tube.

Fig. 5 shows the same cross section as is shown in Fig. 4 with mandrel 3 advanced to move rollers 4 radially outward so as to expand tube portion 1 to bring the several angularly spaced areas on the outer surface of said tube portion into firm contact with the surface of the tube-hole. Further advancing of mandrel 3, and consequent radially outward movement of rollers 4, produces the thinning and enlarging of the tube portion. This is all as described in Patent No. 2,690,205, heretofore described.

As shown in Fig. 5, as the tube is distorted and expanded, the shape of the tube is changed to a somewhat triangular shape, when the conventional three rollers are used, and portions of the tube move to bring portions of the inner surface of the tube inwardly toward the outer surface of the ligaments of roller-cage 5 between rollers 4. The points of least clearance between the distorted tube and the surface of the roller-cage ligaments is at the midpoint of each ligament, half way between each pair of rollers. Obviously, the greater the clearance between the tube-hole and the outer surface of the tube, the more pronounced the triangular effect produced in the tube and the more inward movement of the tube-wall. Thus as the clearance between tube and tube-hole increases, the diameter of the roller-cage ligaments must decrease to maintain clearance between the tube inner surface and the roller-cage outer surface if the tube is to be kept clear of the roller-cage surface during the tube-expanding operation.

Fig. 6 shows a cross-section of an improved form of the roller-cage, to an enlarged scale, taken on the line 6-6 of Fig. 2 or Fig. 3, through the ligaments between roller-slots. In Fig. 6, the circular line C shows the location of the ligament surface of a conventional round roller-cage sized to get caging-lips. The preferred form of this invention has the ligament surfaces, between rollerslots, curved to radius R. The radius R, of this curve, is such that the desired amount of additional clearance D is obtained at the midpoint of each ligament surface and so that the curve intersects the circle circumscribing the roller-cage to give a narrow land F at each side of each of the roller-slots.

The caging-lips L, as shown in Fig. 6 on each side of each of the roller-slots, close in the width of the rollerslots so as to prevent rollers in said slots from falling out. These caging-lips are usually obtained by a milling or a forging operation.

The caging-lips must be formed so as to allow the rollers to move outward radially to get the desired expansion range for the tool. Circular line E represents the circle describing the expansion range. Thus for a conventional tool with circular outer surface of thediameter represented by circular line C, of Fig. 6, with expansion range as represented by circular line B, and

rollers closely fitting the rollerslots, the maximum available'width of the caging-lips is width LC.

As hereinbefore mentioned, the :diameter of the rollercag'e, and of the collapsed roller assembly, must 'be smaller than the inside diameter of the tube in order to easily enter the tool into said tube. The clearance between the tool retracted O. D. and the tube '1. D., on tools :for the smaller size tubes, is usually on the orderof V 2 of an inch. A principal reason for this amount of clearance being needed is because of the frequent ovality of the tubes. A second reason is that the clearance is needed to prevent the dirt particles or metallic chips which occasionally get into the tube ends from becoming jammed between the tool and tube when the tool is being entered into the tube.

A roller cage of the improved form, as shown in Fig. 6, gives a tool assembly having a somewhat triangular shape. A tool having a roller cage of the improved form can be slightly larger in diameter, by the radial amount A of Fig. 6, and still enter the tube to be rolled as easily as a round tool of diameter C. There are three principal reasons for this being possible. One, the triangularshape tool can have better clearance in an oval tube. Two, the flattened portions of the cage surface :give additional clearance for the dirt or chips. the tool is a close fit in the tube, the triangular-shape tool has less area in contact with the tube inner surface thus giving less drag.

As shown in Fig. 6, the caging lips of this improved .form, enlarged by the radial amount A, are of the width LC plus LA. LA represents the gain in caging-lip width resulting from the A radial increase in size. A rollercage having this improved form, with the wider cagi'ng lips, gives improved performance because of the better retaining of the rollers since such a roller-cage :has a longer useful life before the caging lips wear so as to drop the rolls.

An inspection of Fig. 5 and Fig. 6 shows that arolleu cage of the conventional'round shape which hasthe same working clearance as the Fig. 6 form Would be of a diameter represented by the circular line B. Thus shap ing the outer surface of the ligament portion ofthe rollercage'to this improved form, as shown in Fig. 6, increases the cross-sectional area of the ligaments for any set of' working-clearance conditions. The increase in the-cresssectional area of the ligaments is that portion of the'a-rea outside a circle of diameter as represented by circular line B. Thus the strength of the ligaments and the strength of the roller-cage is increased.

The intersection of circular line B-and the curved inner surface of a caging-lip L, in Fig. 6, shows tha't a rollercage of the diameter ofcircular line B having an expansion range as represented by line E and rollers closely fitting the roller-slots would have practically-no width available for caging-lips. This is a result oft-he expansion range and roller diameter bringing the roller centerline nearly tangent with the roller-cage outer surface.

As previously mentioned, the preferred form of relief on the outer surface of the roller-cage givesa curved surface on the ligaments With a narrow land L alongside the roller-slots. The roller-slots are always tapered when caging-lips are used to retain the rollers. The taper on the roller-slots is substantially the same as the taper on the rollers, a nominal amount, usually, of some .005 to .015- inch per inch, and the length of the rollers and slots is some Z-inchcs, or less, on the expanding tools normally used for tubes 1-inch and smaller 0. D. On these tools, relieving the roller-cage surface to a curved form-Which is uniform and generated by a straight lineso moving in a path that the line is always parallel to the axis of said roller-cage produces lands with a slight taper which has no adverse effect on the improved performance of the tool, and the uniform relief produced for "the full length of the ligaments is adequate for the usual conditions.

Lands ZSL straddling the slots for rollers'24, in Fig.' 2,

And three, if I are slightly tapered and they illustrate a condition when the relief :is uniformly formed the full length of the liga ments so as to be parallel to the intersections of the radial projections of the adjacent roller-slot centerlin'es with the surface of a cylinder circumscribing said portion of the roller-cage. In Fig. 2, the relief-form is carried beyond both ends of the roller-slots so as to run out the ends of the head portion of the roller-cage. Continuing the relief-form beyond the ends of the roller-slots is usually satisfactory and les difficult to produce, but the relief-form is needed only along the working length of the rollers.

When the roller-slots are angled to give a considerable cocking of the rollers, as is the usual condition .in a self-feeding expanding-tool, as shown :in Fig. 3, it is generally desirable to generate "the relief on the outer surface of each of the ligaments :so that the relief-form lies in a helical path along the length of the roller-"cage to get lands 35L with a nominal taper and so that the axes of said relief-form parallel the intersections of the radial projections of the adjacent roller-slot 'centerlines with the surface of a cylinder oircumscribing said portion :of the roller-cage.

Again in the Fig. 3 illustration, .it-is usually not necessary to change the radius of the curved form of .the 'relief to get a more uniform land-width since, on the normallyused roller-cage, the length of the roller-slots and the difference in Width of the roller slots at the two ends of said slots gives but'a slightdifference'in land width. 'Obviously, for a tool assembly having a considerable taper onthe roller-slots, the preferred form of relief :would be that'with radius changing to give a substantially constant land-width and uniform working-clearance 'alon-g'therentire length of the roller-slots.

Rolling and expanding the smaller diameter tube joints is a quantity production operation, and there are :often thousands of tube-holes'in one-tube-shcet. Occasionally, some tubeeholes are damaged, when being made, -:so that it becomes necessary to ream .them :oversizeto-get the proper quality of tube-hole surface',.r oun'dness, and uniformity of size,lfor thefull length of the-,tube hole. :Aiso, .rnany'assemblies Y are made .withtubesclassified as fmin-imum-wall for tube-wall thickness. These minimum- -wall tubes vary in theirl. 13,, a considerable amount, because of the broad-tolerance allowed-on.thetube-wall thickness. The usual I requirement for tanrexpandingetool for such a job is that it be small-enough .in..-i=ts.,col-lapsed diameter to easily enter the sma'llest L'D. tube which may be included in the assembly landalso that it be =constructed so that it has an expansion range which -Wi1l enable the tool to rollfand expand a tube having the thinnest wall, and thus therla-rgestI. D.,rin.;the.largest hole in the tube-sheet.

It is generalpractice to have the :O. D. of the-expanding tool small enough to keep the outer-surface of 1he:-rollercagecl-ear of the inner surface of the tubewh'en'theFig. 5 condition exists, because undesirable effects .are produced when the roller-cage surface interferes with the free movement of the tube. .Since the tube-is stationary and-'the roller-cage of the tool assembly is-revolving,interference between the two surfacesproducesa rubbing action which may scratch and tear the tube inner surface. -Whenusing a tube-expanding apparatus such tas is .showninlatent No. 2,690,205, hereinbefore described, .-interference-:between the tube inner surfaceand the surface of ,the rollercage may producev er-roneousresults when part or all. of an increase in the .force' requiredto advance the mandrel, which normally-indicates-that the tube ismakingfi-rm contact with its tube-hole,-may be used to abnormally defleet and stretch the tube-.wall.

Thus it is evident that a roller-wage, which has adequate clearance to suit. the work-requirements,= having; th-isimproved form-on the ligamentaportion ofnsaid cage is stronger because of the increased crosssectional.area .-of the ligaments. 'This is as previously described in that. the conventional round cage would have a cross-sectional 7 area of the ligaments as contained inside a circle of the diameter represented by the circular line B, the diameter represented by the circular line B being the diameter giving the desired working-clearance conditions.

Examining Fig. 6 shows that my improved form for the outer surface of the ligament portion of the rollercage permits the maximum allowance for caging-lips on the edges of the roller-slots. It is often difiicult, on these small-diameter tool assemblies with the conventional round exteriors, to get the desired minimum working diameter and an adequate expansion-range and still have space for caging-lips, because rollers of the preferred diameter, when in their expanded position, have their centerlines nearly tangent with the outer surface of the roller-cage. Obviously, when the roller centerline approaches the circle bounding the roller-cage O. 3)., there is no space available for caging-lips. The rollers must be large enough in diameter to keep the roller centerline well inside of the circle bounding the roller-cage O. D., when the rollers are at their outward radial-travel limit position so that there is space available for caging lips. Obviously, the greater the A increment added at the edges of the roller-slots, the greater the space available for caging-lips, for any given roller diameter and expansion range.

This improvement in the shape of the outer surface of the ligament portion of the roller-cage is shown in its preferred form, in the drawings. However, it is recognized that the ligament portion of the roller-cage can be formed to other non-circular shapes and still get a measure of the benefits described. Any form on this outer surface that gives clearance between the roller-cage and the tube, when the tube is in the Fig. 5 condition during the expanding operation, more than the clearance obtained with the conventional circular outer surface, would be an improvement within the scope of this invention. Similarly, any non-circular form on this outer surface which gives better caging of the rollers than can be obtained with the conventional round shape would be an improvement as set forth herein.

The improvement has been described in connection with rolling and expanding tubes to make tube-joints in heat-exchange apparatus. It is apparent that the same principles apply when a roller-tool of this type is used to make -a tube-joint for any other purpose.

While the invention has been described with reference to the particular devices illustrated, it is to be appreciated that it is not so limited. It is rather of a scope commensurate with the scope of the subj-oined claims.

What -I claim as my invention is:

l. A roller-type tube-expanding tool having a tapered mandrel, a plurality of rollers, and a roller-cage, with the roller-cage having a plurality of angular-1y spaced roller-slots separated by ligaments, and with the rollers being guided in said roller-slots so as to be rotatable about the mandrel and radially movable as said mandrel is axially advanced relative to said roller-cage so that, as the tool works, rolling forces are applied on the inner surface of a tube portion to thin the tube wall and expand and enlarge said tube portion, in which the outer surface of each ligament, in said roller-cage, is flattened by being formed to a curved shape with the profile of said curved shape being a curve with a radius larger than one-half the external diameter of the ligament portion of said roller-cage, and with said profiles being formed so that the point of maximum clearance between the outer surface of each of said ligaments and the normal surface of said tube portion is at the mid-points of said ligaments to thus increase the working clearance between said outer surfaces of said ligaments and said tube-portion inner surface when said tube portion is expanded and distorted to bring the several angularly spaced areas on the outer surface of said tube portion into firm contact with the tube-hole in which said tube portion is being expanded.

2. A roller-type tube-expanding toolhaving a tapered mandrel, three rollers, and :a roller-cage, with the rollercage having three angularly spaced roller-slots separated by ligaments, with the rollers being guided in said rollerslots so as to be rotatable about the mandrel and radially movable as said mandrel is axially advanced relative to said roller-cage, and with said mandrel being axially advanced, relative to said roller-cage, by a tube-expanding apparatus, so that, as said mandrel is axially advanced and said tool works, rolling forces are applied on the inner surface of a tube portion to thin the tube wall and expand and enlarge said tube portion, in which the outer surface of each ligament, in said rollercage, is flattened by being formed to a curved shape with the profile of said curved shape being a curve with radius larger than one-half the external diameter of the ligament portion of said roller-cage, and with said profiles being formed so that the point of maximum clearance between the outer surface of each of said ligaments and the normal surface of said tube portion is at the mid-points of said ligaments to thus increase the working clearance between said outer surfaces of said ligaments and said tube-portion inner surface when said tube portion is expanded and distorted to bring the several angularly spaced areas on the outer surface of said tube portion into firm contact with the tube-hole in which said tube portion is being expanded.

3. A roller-type tube-expanding tool having a tapered mandrel, three rollers, and a roller-cage, with the rollercage having three angularly spaced roller-slots separated by ligaments, with the rollers being guided in said rollerslots so as to be rotatable about the mandrel and radially movable as said mandrel is axially advanced relative to said roller-cage, with the outer edges of the sides of said roller-slots being formed inwardly so as to narrow said slots to thus limit the outward radial movement of said rollers confined in said slots, and with said mandrel being axially advanced, relative to said roller-cage, by a tubeexpanding apparatus, so that, as said mandrel is axially advanced and said tool works, rolling forces are applied on the inner surface of a tube portion to thin the tube wall and expand and enlarge said tube portion, in which the outer surface of each ligament, in said roller-cage, is flattened by being formed to a curved shape with the profile of said curved shape being a curve with radius larger than one-half the external diameter of the ligament portion of said roller-cage, and with said profiles being formed so that the point of maximum clearance between the outer surface of each of said ligaments and the normal surface of said tube portion is at the mid points of said ligaments to thus increase the working clearance between said outer surfaces of said ligaments and said tube-portion inner surface when said tube portion is expanded and distorted to bring the several angularly spaced areas on the outer surface of said tube portion into rfinn contact with the tube ho-le in which said tube portion is being expanded.

4. A roller-type tube-expanding tool having a tapered mandrel, three rollers, and a roller-cage, with the rollercage having three angularly spaced roller-slots separated by ligaments, with the rollers being guided in said rollerslots so as to be rotatable about the mandrel and radially movable as said mandrel is axially advanced relative to said roller cage, with the outer edges of the sides of said roller slots being formed inwardly so as to narrow said slots to thus limit the outward radial movement of said rollers confined in said slots, with at least some of said roller-slots angled so that the rollers confined in said angled slots contact the tube inner surface to give lines of contact between said rollers and said tube inner surface which are angular relative to the longitudinal axis of said tube so that the corresponding angular lines of contact between said rollers and said mandrel gives the tool a self-feeding action which can axially advance said mandrel, relative to said -rollercage, as said tool works, so that, as said mandrel is axially advance-d and said tool works, rolling forces are applied on the inner surface of a tube portion to thin the tube wall and expand and enlarge said tube portion, in which the outer surface of each ligament, in said roller-cage, is flattened by being [formed to a curved shape with the profile of said curved shape being a curve with radius larger than one-half the external diameter of the ligament portion of said roller-cage, and with said profiles being formed so that the point of maximum clearance between the outer surface of each of said ligaments and the normal surface of said tube portion is at the mid-points of said ligaments to thus increase the working clearance between said outer surfaces of said ligaments and said tube-portion inner surface when said tube portion is expanded and distorted to bring the several angulanly spaced areas on the outer surface of said tube portion into firm contact with the tube-hole in which said tube portion is being expanded.

5. A roller-cage, for 1a roller-type tube-expanding tool, having a plurality of :angularly spaced roller-slots in which the rollers of said tool may be contained and guided so that said rollers may be rotatable about the tapered mandrel of said tool and radially movable as said mandrel is axially advanced relative to said roller-cage, with said roller-"cage having a clearance hole extending longitudinally through said cage to provide for the axial movement of said mandrel, relative to said roller-cage, with said angularly spaced roller-slots being separated by ligaments; wherein the outer surface of each of said ligaments, in said roller-cage, is flattened by being formed to a curved shape with the profile of said curved shape being a curve with radius larger than one half the external diameter of the ligament portion of said roller-cage.

6. A roller-type tube-expanding tool as in claim 1; wherein said curved shape formed on the outer surface of each of said ligaments is restricted longitudinally to the portion of the length of said ligaments substantially equal to the work-contacting length of said rollers.

7. A roller-cage, for a roller-type tube-expanding tool, having a plurality of angularly spaced roller-slots in which the rollers of said tool may be contained and guided so that said rollers may be rotatable about the tapered mandrel of said tool and radially movable as said mandrel is axially advanced relative to said rollercage, with said roller cage having a clearance hole extending longitudinally through said cage to provide :for the axial movement of said mandrel, relative to said roller-cage, with said angularly spaced roller-slots being separated by ligaments, and with the outer edges of the sides of said roller-slots being formed inwardly so 'as to narrow said slots to thus limit the outward radial movement of said rollers which may be contained in said slots; wherein the outer surfiace of each of said ligaments, in said roller-cage, is flattened by being formed to a curved shape with the profile of said curved shape being a curve with radius larger than one-half the external diameter of the ligament portion of said roller-cage.

8. A roller-oage, for a roller-type tube-expanding tool, as in claim 5; wherein said curved shape formed on the outer surface of each of said ligaments is restricted longitudinally to the portion of the length of said ligaments substantially equal to the work contacting length of said rollers.

9. A roller-cage, for a roller-type tube-expanding tool, as in claim 7; wherein said curved shape formed on the outer surface of each of said ligaments is restricted longitudinally to the portion of the length of said ligaments substantially equal to the work-contacting length of said rollers.

References Cited in the file of this patent UNETED STATES PATENTS 383,11 1. Duffy May 22, 1888 2,375,235 Maxwell May 8, 1945 2,690,205 Stary Sept. 28, 1954 FOREIGN PATENTS 3,628 Great Britain Sept. 7, 18-80 15,579 Great Britain Oct. 4, 1889 5,396 Great Britain Mar. 18, 1892 525,549 Germany May 26, 1931 560,205 Great Britain Mar. 24, 1944