US2736950A

US2736950A - Method and apparatus for tube expansion

Info

Publication number: US2736950A
Application number: US184743A
Authority: US
Inventors: Harold C Mathews
Original assignee: AIRETOOL Manufacturing CO
Current assignee: AIRETOOL Manufacturing CO
Priority date: 1950-09-14
Filing date: 1950-09-14
Publication date: 1956-03-06
Anticipated expiration: 1973-03-06

Description

March 6, 1956 H. c. MATHEws 2,736,950

METHOD AND APPARATUS FOR TUBE EXPANSION Filed Sept. 14. 1950 5 Sheets-Sheet l lo le l5 ,f

ATTORNEYS.

March 6, 1956 H. c. MA'rHl-:ws 2,736,950

METHOD AND APPARATUS FOR TUBE EXPANSION Filed Sept. 14. 1950 3 Sheets-Sheet 2 INVENToR. l HAROLD C. MATHEws BY 7M f "mimi/m FIG 8 a ATTORNEYS March 6,*1956 H, C, MATHEWS 2,736,950

METHOD AND APPARATUS FOR TUBE EXPANSION Filed Sept. 14, 1950 5 Sheets-Sheet 5 MilfIMIIIIIIIMMALH INVENTOR HAROLD C. MATH EWS BY 7M/M40 M ATTORNEYS.

Unite atea This invention relates to apparatus for expanding tubes into tube sheets such as in condensers and other heat exchangers.

An object of the invention is to provide a tube expander of an improved form by which the degree of expansion of the tubes can be accurately controlled, and particularly wherein the same degree of expansion can be given to a number of tubes of like diameter and like wall thickness.

Another object of the invention is to provide a tube expander wherein the degree of expansion of a tube along the length of its contact with the tube sheet is maintained uniform with a uniform degree of reduction of tube wall thickness throughout the length of the contact of the tube with the tube sheet.

Still another object of the invention is to provide a tube expander With a central mandrel that is driven in one direction to place the expanding rolls into contact with the tube for expanding the same and is driven in an opposite direction to cause withdrawal of the expander from the tube with simultaneous expansion of the tube into engagement with the tube sheet.

Still another object of the invention is vto provide a tube expander in accordance with the foregoing objects wherein the expansion of the tube is carried forward from the inner face of the tube sheet toward the cuter face of the tube sheet.

Still another object of the invention is to provide a tube expander which includes a device to control the position of the expanding rolls of the expander within a tube so that the rolls can be positioned within a series of tubes sequentially at exactly the same depth, and also to provide a device for controlling the position of the mandrel relative to the rolls for regulating the position of the rolls to obtain exactly the same degree of radial expansion in each of the series of tubes.

Another object of the invention is to provide means operating in cooperation with the tube expander to indicate the degree of expansion of a tube in a tube sheet so that a series of tubes in a tube sheet can each be expanded individually with a like degree of expansion yinto engagement with the tube sheet irrespective of dimensional variations of the tube and the hole in the tube sheet receiving the tube.

Still another object of the invention is to provide a method of expanding tubes into a tube sheet by which the tube is placed under tension at the beginning of the tube expanding operation to thereby prevent buckling of the tube between tube sheets placed at opposite ends of the'tube.

Another object of the invention is to provide a method of expanding a tube into a fluid-tight bond with a tube sheet in which the tube is initially expanded into engagement with the tube sheet in proximity of the inner face of the tube sheet with resultant reduction in Wall thickness of the tube, the expansion causing the tube to be initially placed under tension before reducing the wall thickness of the tube, which tension is thereafter at least partially released by the resultant ilow of metal in the tube in both directions axially of the tube.

It is still another object of the invention to provide a method of expanding a tube into a duid-tight bond vwith a tube sheet in accordance with the foregoing object f tent 2,736,950 Patented Mar. 6, 1956 ant ow of metal in the tube axially thereof from rthe inner face of the tube sheet toward the outer face thereof, which is the direction of least resistance to the flow of metal in the tube.

Further objects and advantages will become apparent from the drawings and the following description.

Figure l is a longitudinal cross-sectional view of a tube expander incorporating features of this invention;

Figure la is an elevational View partially in section illustrating the position of the tool of Figure l in the first step of expanding a tube into a tube sheet and wherein the tool and tube are positioned loosely in the seat of the tube sheet.

Figure 1b is a view similar to that of Figure la illustrating the position of the tool in the second step of expanding a tube into a tube sheet and wherein the interior portion of the tube has been expanded against the tube seat by the expanding tool.

Figure lc is a view similar to that of Figure la illustrating the position of the tool in the third and nal step of expanding a tube into a tube sheet with the tool being moved outwardly of the tube and wherein the tube has been expanded into Contact with the tube seat over a portion of the length thereof from the interior face of the tube sheet outwardly.

Figure 2 is an elevational view of a portion of the cage of the tube expander illustrating the rolls of the tube expander as set at a self-feeding angle;

Figure 3 is an elevational view of the locking mechanism for holding the mandrel of the device of Figure l in a predetermined position;

Figure 4 is a cross-sectional view taken along line 4 4 of Figure l;

Figure 5 is a longitudinal cross-sectional view of another arrangement of a tube expander incorporating features of this invention;

Figure 6 is a cross-sectional View taken along line 6 6 of Figure 5;

Figure 7 is a cross-sectional view taken along line 7-7 of Figure 5;

Figure 8 is a composite elevational and cross-sectional view illustrating the rst step in the method of using the tube expander shown in Figure 5;

Figure 8a is a view of a portion of Figure 8 with the parts broken away.

Figure 9 is a view similar to Figure 8 illustrating the expanding step in the method of tube expansion using the tool of Figure 5;

Figure 10 is a view similar to Figure 8 illustrating the completion of the method of expanding a tube.

Figure `ll is an elevational view of a driver and a control for operating the tube expanders illustrated in Figures l and 5.

The tube expander of this invention illustrated in Figures l, 2 and 3 consists of a tube expanding head consisting of a cylindrical cage 10 that has a longitudinal bore 11 extending axially through the cage. The cage 10 has radially disposed

slots

12, 13 and 14 (Fig. 4) each of which receives a roll, 15, 16 and i7, respectively. The slots, 12, 13 and 14 are shaped to prevent the

rolls

15, 16 and 17 from leaving the slots radially of the cage 10, the outer ends of the slots being narrower than the diameter of the rolls.

The

rolls

15, 16 and 17 are set at an angle relative to the axis of the cage 1t?, as illustrated in Fig. 2, whereby the rolls self-,feed a mandrel 20 that extends axially through the bore 11, inwardly of the cagevl upon rotation of the mandrel in one direction and upon reversal of rotation of the mandrel the rolls self-feed the cage outwardly through a tube that is being expanded.

The mandrel 2t? is provided with a long forward tapered end that engages the rolls 15, i6 and 17 to selectively positionvthem radially outwardly of the cage 1t? when the forward end of the cage is placed within a tube, The

rolls

15, 16 and 17 are tapered between their opposite ends to match the tapered end of the mandrel 29. Also, the rolls 1S, 16 and 17 each have their

opposite ends

18 and 19 tapered to thereby eliminate formation of a spiral ridge on the inner surface of a tube as the expander selffeeds itself through the tube.

The rear end of the mandrel 20 has a threaded portion 21 that engages the internal thread 22 of the housing 23. A longitudinal groove 24 extends along the threaded portion 21 of the mandrel 20 to receive the end of a set-screw 25 to lock the mandrel 20 to the housing 23 after suitable adjustment has been made between these members.

The forward end of the housing 23 has a radially anged head 26 that is received within a rotatable collar 27, the flanged head 26 of the housing 23 engaging an inwardly flanged portion 2S on the collar 27 which prevents removal of the housing 23 from the collar 27 in a leftward direction as viewed in Figure l. The collar 27 also has a bayonet lock slot 30 (Fig. 3) in diametrically opposite sides thereof and each of which slots is adapted to engage lock pins 31 extending from the collar 32; the collar 32 is secured to the cage 10 by means of a set-screw 33. The housing 23 has an end portion 34 adapted for engagement by a chuck of a suitable driving device and a ring 23a secured on the housing protrudes slightly above the housing surface between end portion 34.1 and i'iange head 25; this ring is not necessary to the operation but may be utilized to retain rotatable collar 27 on the housing when the collar is disengaged from pins 31. It is thus to be noted that the mandrel 2b and the housing 23 are threadedly engageable and are retained xedly in a desired engaged position by set screw 25. Accordingly housing 23 and mandrel 20 in their operative position are locked against relative axial movement but are rotatable together as a unit.

The collar 27 carried by housing 23 is engageable with pins 31 carried by the collar 32 (Figures l and 3); the collar 32 is secured to cage 16 and hence in the engaged position of collar 27 and pins 31 the cage 1t?, housing 23 and mandrel 2t) are locked together for rotation as a unit, if set screw 25 i-s tight on the mandrel 2i). Also the mandrel and cage are then locked against relative axial movement in either direction of rotation of the 'u mandrel and housing.

lTo permit free rotation of the housing and mandrel with respect to cage l0, as well as longitudinal movement o1'. the same with respect to the cage, it is only necessary to release the collar 27 (Figure l) from the pins 31 and move the collar 27 leftwardly on the housing 23, free of the pins carried by collar 32 (Figure la).

The use of the structure of Figure l in securing a tube in tube sheets will now be described in detail in connection with Figures la, lb and lc, and for the purposes of description it will be assumed that a rst end of the tube has been secured in a tube seat of a rst tube sheet and the second end of the tube is about to be secured in a tube seat of a second tube sheet 101.

Initially, in using the embodiment described, the collar 27 is released (Figure l) from pins 31 to position the collar 27 freely on housing 23; the mandrel 2t? is then threaded into the housing 23 to the desired position and set screw 25 secured, thus locking the housing 23 and mandrel 20 xedly together, the two being rotatable with respect to, and also longitudinally movable with respect to cage 10. Nut 44 prevents complete withdrawal of the mandrel from the cage in one direction while the rolls 15 and housing 23 prevent complete withdrawal of the mandrel in the other direction.

4 With nut 44 against the end of cage 10 and the rolls thus in a contracted position, the cage is inserted into the tube 104) (Figure la) until the rolls are at the inside face of the tube sheet; at this time the tube 160 is of course only loosely positioned within the tube seat.

The stop member 35 is now threaded along cage i6 until it engages the outer face of the tube sheet; the stop member is then secured in position by set screw 37 and thus further entry of the cage 10 into the tube seat is inhibited (Figure la). Mandrel 20 is then urged rightwardly through the positioned cage to contact the rolls l5.

A reversible driver, such as that indicated in Figure ll, Secured to the end portion 34, is rotated then in a clockwise direction and the mandrel 20 also rotates in a clockwise direction as indicated by the arrow (Figure 1b) in engagement with the rolls 15 and due to the self-feeding relationship the mandrel feeds through the rolls further, causing the same to expand against the loosely retained tube ln this initial expansion period the tendency is for cage it) to also feed into the tube 100 but since it is restrained by the stop member the tube 13%', due to the reaction, feeds outwardly of the sheet (Figure 1b) thus placing an initial tension on the tube between tube sheets. As the expansion of the rolls 15 continues with the feeding of the mandrel the tube 160 engages the seat and the thickness of the tube wall is diminished; this causes metal ow inwardly of and outwardly of the tube seat (Figure lb) and this inward flow of metal offsets tensive stress occasioned by the initial tensioning action.

The rotation of the mandrel 2li is continued in a cloclo wise direction until the tube is iirmly against the tube seat.

With the inner portion of the tube iirmly against the seat the ange 26 of the housing 23 abuts the cage end as shown in Figure 1b; the collar 27 which up to this time has been disengaged is then engaged with pins 31 and the cage housing and mandrel are locked for rotation as a unit.

The reversible driver is now reversed in its rotational direction and the mandrel 2t) is driven counterclockwise as per the arrow (Figure lc); the locking of the mandrel to the cage provides that the mandrel may not move axially with respect to the cage in this direction of rotation and therefore the rolls 15 remain in their expanded position and the entire expander self feeds outwardiy of the tube expanding the tube over the length thereof (Figure 1c 3X particular feature of the embodiment of Figure l, relating to the position of the mandrel 2b with respect to the rolls 15, is that when once adjusted the adjustment may be maintained exactly and resetting is not necessary in order to expand a plurality of similar tubes. Thus to repeat the expansion operation described above it is only necessary to slip collar 27 from pins 31 and to retract the mandrel until nut 44 abuts cage 10. The

device may be then inserted in the next tube and the operation repeated.

Surrounding the cage 1t) there is provided a stop member 3S having one portion 36 thereof secured to the cage 1t? by means of a setscrew 37 that engages a longitudinal groove 3b provided in the threaded extension 39 of the cage 10. The other part 4t) of the stop member 35 is secured to the part 36 by means of a C ring 41. The anti-friction ball bearing structure 42 is placed between the parts 3b and 49. The part member 40 is adapted to engage the outer face of a tube sheet to resist movement of the cage l@ into a. tube beyond a predetermined depth and is provided with an axial bore 43 which is adapted to receive the end of a tube that may project from the tube sheet. The mandrel 2i? has a nut 44 on the end thereof that proiects from the cage 10 to prevent thc mandrel from being removed from the cage.

In Figures 5, 6 and 7 there is illustrated another form of tube expander incorporating features of this invention. This form of the invention includes a cage 10a constructedlike the cage lillustrated in Figure. 1. includes the same roll-s illustrated in the forward end of cage 10. The cage a has a stop member 50 that performs the same function as the stop member and includes a recess 51 to receive the end of a tube projecting from a tube sheet. The stop member has asetscrew 52 to tix it in position on the cage 10a.

A mandrel 55 extends through the bore 11a of the cage 10a in the same manner of the mandrel 20, and cooperates with the rolls of the expander in the same manner as described with referencey to Figure 1. The mandrel illustrated in Figure 5, however, is provided with a square head 56 on the rear end thereof for placement within a plug 57. The set-screw' 58 retains the square head 56 within the plug 57.

The plug 57 forms a part of a mandrel driver or driving device 60. The driving device includes a housing 61 having a splined internal bore 62 extending axially of the housing 61. The plug 57 is provided with external splines that cooperate with the internal splines of the bore 62 to permit the plug to move axially of the housing 61.

The housing 61 is provided with

slots

63 and 64 on diametrically opposite sides thereof which receive a pin 65 projecting from opposite sides of the plug 57. The pin 65 is held in the plug 57 by means of a cross fastening pin 66.

Opposite ends of the pin 65 project through the

slots

63 and 64 into engagementwith a collar 67 including annular rings 67a that surround the housing 61 and are freely slid able thereon.

The housing 61 is provided with an exteriorly threaded portion 68 which receives a-nut 69. The nut 69 provides a stop for the collar 67 to prevent leftward movement thereof on the housing 61.

A plug 70 is suitably secured within the end of the housing 61 and has a projection 71 to which a chuck can be attached for driving purposes. The plug 70 is also provided with a tapered bore 72 to receive a tapered'pin of a driving device.

The cage 10a is threadedly received in one end of a sleeve 75 that extends through an opening 76 in a closure cap 77 which is threaded onto the housing 61. The sleeve 75 has a radial flange 78. An anti-friction bearing 79 is placed between the flange 78 and the closure cap 77 and acts as a thrust bearing.

The tube expanders illustrated in Figures l and 5 perform a method of tube expansion that is more clearly illustrated in Figures 8, 9 and 10, the device of Figure 5 being used for the purpose of illustrating the expansion of the end of a tube 100 into a tube sheet 101. The tube sheet has an opening 102 which receives the end of a tube 160.

When the tube expander is to be placed into the tube 100, the nut 69 on the housing 61 is backed off to the left as shown in Figure 8 to allow movement of the collar 67 in a leftward direction, thus withdrawing'the mandrel 55 from within the cage 10a to permit the rolls in the cage to ride upon the smallest diameter of the mandrel 55. This places the expanding rolls at or below the surface of the cage 10a, and the rolls maybe considered as contracted.

The cage 10a with the rolls in the contracted position is then inserted into the tube 100, which tube has previously been placed in the tube sheet 161. r1`he stop member 5i) is threaded upon the cage 16a to place the ex pansion rolis within the tube 100 to the desired depth, as illustrated in Figure 8, that is, with the stop member engaging the outer face of the tube sheet. The set-screw 52. is then tightened to hold the stop member in position on the cage 10a.

A suitable reversible driver is connected to the projection 71 of the tube expander and drives the mandrelv S5 in a clockwise direction. The collar 67 is moved axially over the housing 61 in a rightward direction to advance the mandrel 55 into thecage 10`a-until` the expansion rolls It alsol engagey the internal diameter of the tube 100, thereafter, continued-clockwise rotation of the mandrel causes the mandrel to be fed into the cage 10a by reason of the selffeeding angle at which the

rolls

15, 16 and 17 engage the mandrel. This operation continues until the tube is expanded to the desired degree, whereupon the nut 69 is advanced against the collar 67, as shown in Figure 9.

During the self-feeding of the mandrel into the tube and the initial expansion of the tube 160, the stop member 5i! prevents advancement of the cage 10a into the tube. When the rolls 15, 16 and 17 engage the tube 100 continued clockwise rotation of the mandrel 55 continues the self-feeding of the mandrel between the rolls with. resultant expansion of the tube 100 into engagement with the tube sheet. Since the cage 16a cannot be drawn into the tube 161i, the reaction of the rolls on the tube causes the tube 101i to be drawn in a leftward direction with the result that a tension is placed upon the tube while it is expanded into engagement with the opening 192 in the tube sheet 101, as illustrated in Figure 9. This preliminary tensioning of the tube between tube sheets after the tube has been expanded into engagement with the one tube sheet prevents buckling of the tube under compression between tube sheets while the opposite end of the tube is being expanded into engagement with the other tube sheet.

With the tube 10i) under tension at the time it makes initial engagement with the tube sheet, initial reduction of the wall thickness of the tube causing metal ilow in opposite axial directions in the tube will not cause buckling of the tube between tube sheets but will merely release the tension under which the tube has been placed during the iirst portion of the initial expansion.

The recess 51 in the stop member 519 provides for movement of the end of the tube 1% from the tube sheet 161 during the initial tensioning movement of the tube relative to the tube sheet, and also provides for taking care of any variation in length of the tube between opposite tube sheets as a result of manufacturing tolerances, and also takes care of movement of the tube 10) during the initial expansion into engagement with the tube sheet.

With the tube expander in the position illustrated in Figure 9, the driver is then reversed in its direction of rotation causing the mandrel 55 to be rotated in a counter-clockwise direction. 'Iltis` rotation of the mandrel in the counter-clockwise direction tends to drive the mandrel in a ieftward direction through the cage 10a, but this is prevented at this time because the collar 67 abuts the nut 69. of the mandrel wiil cause rotation of the rolls and of the cage 16a within the tube 10i) with the result that the selffeeding angle at which the expansion rolls 15, 16 and 17 are set wiil cause the expander head to self-feed from the inner toward the outer surface of the tube sheet 191 with simultaneous expansion of thc tube uniformly throughout the length expanded in a continuous operation. With the tube initially expanded into engagement with the tube sheet adjacent the inner face of the tube sheet, ow of metal in the tube resulting from reduction of wall thickness during the expansion operation will be continuously outwardly toward the outer face of the tube sheet, this being the path of least resistance for the metal ow.

At the end of the tube expansion operation, as iilustrated in Figure l0, the nut 69 is rotated to move in a leftward direction on the housing 61 so as to release the collar 67 for movement to the position illustrated in Figure 8, whereupon the tube expander can be placed in another tube and the operation repeated,

While the mandrel 55 has been described as being selffed between the expansion rolls, yet the mandrel can be fed manually or by other mechanism. Also, suitable mechanism can be provided to draw the cage outwardly through the tube for the expansion operation without departingfrom the method of tube expansion disclosed herein.

Therefore, the counter-clockwise rotation- In Figure 11, here is illustrated a driver llt), consisting of conventional reversibly rotatable electric motor, the driver being suitably constructed for hand holding. The driver liti is provided with a chuck ill into which either of the tube expanders of Figure l or Figure can be placed. The electric motor of the driver lili receives electric current through a control apparatus .H2 which measures the amount of current used by the electric motor, a suitable ammeter Il?, being provided on the control 112 to indicate the current being supplied to the motor. A control device 114 may be provided to cut oli the electric current to the electric motor when the current supplied to the motor reaches a certain value.

Since it is a well-known fact that the amount of electric current used by an electric motor is governed by the torque required to drive a given device under load, the amount of torque that is required to drive the mandrel in the initial phase of expanding the tube will reect itself in terms of amperes on the ammeter H3 of the control 112. Thus, a determined amount of expansion of a tube of given diameter will require a given consumption of electric current. Thus, by controlling the maximum current that can be used by the electric motor in the initial phase of tube expansion, control of the maximum amount of tube expansion that can be occasioned by the tube expander under a given set of conditions is obtained, since the torque required by the mandrel 2li reects the force required to expand the tube to a predetermined degree of expansion when the tube is of a given diameter, and of a given material and is being expanded within a tube sheet of a given material. Such a control will expand the tube into engagement with the tube sheet with a predetermined pressure to give a satisfactory bond to the tube sheet without over-stressing the tube or reducing tube wall thickness unnecessarily. A Huid-operated motor and suitable control, therefore, can be used in place of the electric apparatus.

Thus, by making the initial expansion of a tube under control of the

apparatus

13,2, an operator can give to each individual tube individual treatment with the result that each tube will be expanded to exactly the same degree of expansion and pressure engaging the wall of the tube sheet irrespective of dimensional variations of the tube and of the openings in the tube sheet.

While the invention as disclosed and described herein illustrates preferred forms of apparatus and a method of expanding tubes, it will be understood that modifications can be made without departing from the spirit of the invention, and that all modifications that fall within the scope of the appended claims are intended to be included herein.

I claim:

l. A tube expander comprising, a cage having a plurality of rolls positioned about the same with their axes positioned angular to the axis of said cage, a tapered mandrel positioned axially within said cage reversibly rotatable therein and engaging said rolls for radial movement thereot` in said cage upon axial movement of said mandrel in said cage whereby said rolls may be expanded and contracted, a housing rotatably mounted with respect to said cage and releasabiy secured against longitudinal movement with respect thereto, said housing having an end portion of said mandrel secured therein for rotation therewith, said mandrel and housing being rotatable in one direction to move said rolls into an expanded position, said housing and cage having means cooperating to lock said housing, mandrel and cage ragainst relative axial movement in the other direction of rotation of said mandrel in the expanded position of said rolls.

2. A tube expander comprising a cage having a plurality of rolls positioned about the same with their axes positioned angularly to the axis or" said cage, a rotatable mandrel within said cage and having a tapered portion engaging said rolls for radial movement thereof upon axial movement of said mandrel whereby said rolls may be expanded and contracted, stop means on said cage vmovable thereon to restrict the depth of entry of said head into a tube, a housing rotatably secured to said cage against longitudinal movement with respect thereto and having an end portion of said mandrel received therein, means securing said mandrel to said housing for longitudinal movement therein and rotation therewith, said mandrel and housing being rotatable in one direction to move said rolls into an expanded position in the engaged position of the stop means, and means on said housing longitudinally movable therealong and engageable with said securing means to lock the same and said mandrel in one direction of axial movement of said mandrel, said housing and mandrel being rotatable in the opposite direction in the expanded position of said rolls and in the engaged positions of said longitudinally movable means and said stop means whereby said cage, mandrel and housing are axially movable as a unit.

3. ln a tube expander the structure comprising a cage having a plurality of radially movable rolls therein, a tapered, axially movable mandrel, rotatable clockwise and counter-clockwise, in contact with said rolls at an angle therewith for self-feeding of the mandrel through the cage whereby said rolls may be expanded and contracted, said mandrel being rotatable in one direction to move said rolls into an expanded position, and means to lock said mandrel and cage against relative axial movement in the other direction of rotation of said mandrel in the expanded position of said rolls.

4. in a tube expander the structure comprising a cage having a plurality of radially movable rolls therein, a tapered, axially movable mandrel, rotatable clockwise and counter-clockwise, in contact with said rolls at an angle therewith for self-feeding of the mandrel through the cage whereby said rolls may be expanded and contracted, said mandrel being rotatable in one direction to move said rolls into an expanded position, a housing having an end portion of said mandrel received therein, means to secure said end portion and said housing together for rotation of said mandrel and housing as a unit, and means, including said housing, to lock said mandrel and cage against relative axial movement in the other direction of rotation of the said mandrel in the expanded position of the rolls.

5. In a tube expander the structure comprising a cage having a plurality of radially movable rolls therein, a tapered, axially movable mandrel, rotatable clockwise and counter-clockwise, in contact with said rolls at an angle therewith for self-feeding of the mandrel through the cage whereby said rolls may be expanded and contracted, said mandrel being rotatable in one direction to move said rolls into an expanded position, a housing secured against longitudinal movement with respect to said cage and having an end portion of said mandrel secured therein for rotation of said mandrel and housing as a unit, and means to lock said mandrel and cage against relative axial movement in the other direction of rotation of said mandrel in the expanded position of said rolls.

6. ln a tube expander, in combination with a cage having a plurality of movable rolls and a tapered mandrel passing axially through thev cage in contact with the rolls at an angle therewith for self-feeding of the mandrel upon rotation thereof, said mandrel being rotatable in one direction to move said rolls into an expanded position, an exteriorly threaded, slotted housing having an axially movable plug splined therein, said housing being rotatable relative to said cage and secured against longitudinal movement with respect thereto, slidable means on and passing through said slotted housing and secured in said plug, said plug also having an end portion of said mandrel secured therein for movement therewith, and a collar threaded on said housing and engageable with said slidable means to restrict the movement of said slidable means, said plug and said mandrel in an axial direction in an expanded position of the rolls.

7. In a tube expander, in combination witha cage having a plurality of movable rolls and a tapered mandrel passing axially through the cage in contact with the rolls at an angle therewith for self-feeding of the mandrel upon rotation thereof, said mandrel being rotatable in one direction to move said rolls into an expanded position, a slotted, exteriorly threaded, internally splined housing concentric with a prolongation of the axis of said cage, bearing means securing said housing and cage together rotatably and against axial relative movement, said housing having a plug splined therein for rotation therewith, said plug having an end portion of said mandrel secured therein for rotation with the housing, a collar threaded on said housing, said housing and mandrel being rotatable in one direction to self-feed said mandrel and expand said rolls, and means passing through said slotted housing secured to said plug and engageable by said collar for locking the axial movement of said mandrel secured to said plug with respect to said cage in the other direction of rotation of said housing and mandrel.

8. In a tube expander, a cage having a plurality of radially movable rolls therein, a flanged sleeve around an end of said cage, a housing concentric with a prolongation of the axis of said cage and sleeve and having a cap secured on one end thereof and extending over said flanged sleeve to secure said housing and cage against relative axial movement, bearing means between said sleeve and cap for relative rotational movement of said cage and housing, a tapered axially movable mandrel extending axially through said cage and sleeve into said housing and in contact with said rolls for movement thereof into expanded and contracted positions, the rolls and mandrel being set at a self-feeding angle for the mandrel, first means carried by the housing movable axially with the mandrel engaging with and securing an end portion of the mandrel in the housing, and other means carried by said housing engageable with said iirst means to secure said mandrel and first means against axial movement in one direction, said mandrel being rotatable with said housing in one direction of rotation to move said rolls to an expanded position, said mandrel and housing being rotatable in the opposite direction of rotation in the expanded position of the rolls and engaged position of said first means with said other means and in which engaged position said cage and mandrel are locked against relative axial movement.

9. In a tube expander, a cage having a plurality of rolls therein, a tapered axially movable mandrel passing through said cage in contact with said rolls at a selffeeding angle therewith for movement of said rolls to expanded and contracted positions, a housing secured to an end portion of said mandrel in alignment with said cage for rotational movement of said mandrel and housing as a unit in both directions of rotation thereof, and means including a bayonet lock securing said housing and cage in an expanded position of the rolls against relative axial movement in the direction of rotation of said housing and mandrel which would normally self-feed said rolls to a contracted position.

10. In a tube expander, an exteriorly threaded cage having a plurality of rolls therein, a tapered axially movable mandrel passing through said cage in contact with said rolls at a self-feeding angle therewith for movement of said rolls to expanded and contracted positions, a housing secured to an end portion of said mandrel in alignment with said cage for rotational movement of said mandrel and housing as a unit in both directions of rotation thereof, a stop member on said cage between said rolls and housing for engagement with a fixed stop, and means including a bayonet lock securing said housing and cage, in an expanded position of the rolls and an engaged position of said stop member, against relative axial movement in the direction of rotation of said housing and mandrel which would normally self-feed said rolls to a contracted position.

11. In a tube expander, a cage having a plurality of rolls therein, a tapered axially movable mandrel passing through said cage in contact with said rolls at a selffeeding angle therewith for movement of said rolls to expanded and contracted positions, a housing secured to an end portion of said mandrel in alignment with said cage for rotational movement of said mandrel and housing as a unit in both directions of rotation thereof, and locking means releasably securing said housing and cage in an expanded position of the rolls against relative axial movement in the direction of rotation of said housing and mandrel-which would normally self-feed said rolls to a contracted position.

l2. In a method of securing a tube in the second of opposed tube sheets, a first end of which has been secured in a first tube sheet, the method comprising expanding a tool into contact with the second end of the tube only at a location adjacent the interior face of the tube sheet and while expanding the tool tensioning the tube between sheets, expanding the tool further into contact with the tube to cause the tube to be expanded firmly into engagement against the tube seat at said location only, the flow of metal of the tube upon engagement of the tube and seat offsetting the initial tensioning, and thereafter rolling the remaining portion of the tube firmly against the tube seat, said rolling being from the interior face of the sheet outwardly.

13. In a method of securing a tube in the second of opposed tube sheets, a first end of which tube has been secured in a first tube sheet, the method comprising inserting a self-feeding tube expander into the second end of the tube which end is itself freely tted in the second tube sheet, the expander being inserted for expansion only at a location adjacent the interior face of the sheet, actuating the expander into contact with the tube to cause the expander to tend to self-feed into the tube, restricting the limit of movement of the expander into the tube to the location adjacent the interior face while continuing the actuation thereof to cause the expander to engage the tube only at said location and the tube to be drawn into tension between tube sheets by the reaction of the expander on the tube, continuing the actuation of the expander to cause the tube to be expanded firmly against the tube seat at said location, the engagement of the tube with the tube seat occasioning offsetting of the initial tensioning, and thereafter expanding the remainder of the tube into engagement with the tube seat.

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