US1937644A - Flexible mandrel - Google Patents

Description

Dec. 5, 1933. M EATON 1,937,644

FLEXIBLE MANDREL Filed March 21, 1951 3 Sheets-Sheet l ww-nssscs 17 v INVENTOR 771M541 Z Wxw/Mw Dec. 5, 1933. G EATON 1,937,644

FLEXI BLE MANDREL Filed March 21, 1951 s Sheets- Sheet 2 INVENTOR G. M. EATON FLEXI BLE MANDREL 3 Sheets-Sheet 3 Filed March 21 1931 2% AAA\\\\\\\\\\\ INVENTOR mmxw/MAW Dec. 5, 1933.

VITNESSES 77 WW Patented Dec. 5, 1933 r 1,937,644 FLEXIBLE MANDR L George M. Eaton, Ben Avon, Pa., a'ssignor to Spang, Chalfant & 00., Inc., Pittsburgh, Pa., a corporation of Pennsylvania Application March 21, 1931. Serial 1%.524535 ,7 Claims. (01. 1o '107 My invention relates to the supporting of tubing against deflection or distortion when subjected to exteriorly applied forces, and is particularly applicable to the holding of tubing during the cutting 5 of threads on its surface, or while performing other heavy cutting operations on it.

Much time and effort have been expendedin attempting to cut threads on the exterior of pipe by a hobbing operation, in which, and in certain (10 other thread cutting processes, very heavy cuts are taken at one side only of the pipe. In practice it has been found that. the pressure exerted by the cutting tool against the pipe in taking such cuts is suflicient to deflect or distort the pipe to such extent that when the cutting operation is completed and the pipe returns to its relaxed shape the threads are so distorted and inaccurate that the pipe cannot be used. I

An attempt has been made to overcome this difficulty by inserting a solid cylindrical mandrel in the pipe to support it during the hobbing operation. However, inasmuch as the inner surface of commercial pipe and similar tubular members are ordinarily not accurately cylindrical, a cylindrical mandrel causes the pipe to be deflected out of its normal relaxed shape when it is inserted. Hence, after threads have been out on the surface of the deflected pipe and the mandrel removed, the pipe returns to its originalrelaxed shape, thus destroying the accuracy of the threads.

Mandrels having independent supporting elements actuated by fluid pressure or similar means have been tried, but have also been found to be inadequate to support the pipe in its relaxed shape.

fluid pressure mandrels tend to force the pipe to cylindrical shape, or to permit it to be deflected towards cylindrical shape when acted upon by external force. well known principle that tubular objects tend to assumeoylindrical shape when subjected to internal fluid pressure. For example, if the tube to be supported by a fluid pressure operated mandrel is somewhat elliptical in shape, the mandrel tends to distort it to cylindrical shape. Or, if the mandrel is not sufliciently powerful to do-so, a heavy external force applied along the major axis of the ellipse will distort the tube to a shape more nearly cylindrical. the cross sectional area of the tube is increased and the volume of the space occupied by the fluid is correspondingly increased. This occurs both in cases in which the fluid isapplied'directlyto the tube and in case a mandrel having fluid actuated supporting member is utilized. If the operating Just as in 'lhe case of solid cylindrical mandrels;

This is in accordance with the In so changing shape fluid is confined by non-resilient means, such i ncrease in volume'reduces the working pressure the mandrel and permits further distortion of the tube. I

It is an object of this invention to provide a 6.0 method of accurately cutting threads on pipe wherein the pipe isheld firmly and rigidly in its normal relaxed shape during the thread cutting operation. r

Another object of my invention is to provide 65. a, mandrel for supporting. a tubular body that conforms accurately to the interior shape of the tubular'body and that holds it rigidly in its nor-: mal relaxed position.

. A further object is to provide an expans'ible mandrel that is economical to. manufacture and that is rugged and easily manipulated.

In accordance with my invention, 'Iprovide a mandrel having a plurality of work-engaging members, each member being providedwith two independent contact areas. Means are provided for moving the members tobring all of. the contact areas into engagement with the innersurface of the tubularbody to be supported. The means for moving the supporting membersfinclude a8!) wedge member disposed to exert equal forces on the supporting members;- and .to set up frictional forces between the members and the tubular body," and between itself and the members to lockthem in position.

' I I The foregoing and other objects of the inven tion will become more" fullyiapparent as a better understanding of. the invention is had upon studying the specific structures'd'escribed in this speciflcation and shown in theaccom'pan'ying' draw- 9Q ing's, in which Fig."1 is a view inend elevation of an expansible" mandrel, embodying my invention, disposed within a-tube; Fig. 2 is a view in; section of the mandrel shown in Fig; 1 taken on the plane indicated by theline II-' II therein;

Fig. 3 is a plan view showing in conventional man'- ner a thread hobbing machine in which is mounted a pipe supported by'the mandrel embodying my invention; Fig. 4 n view showing one element of my flexibleman'drel disposed withina 10.0"

.tube; Fig. 5 is a viewjsimilar-to Fig. 4 showing means foradaptingthe mandrel to tubes o1 vari-f' ous diameters; Fig. 61s a view similar to Fig. 4 showing, on a reduced scale,a niodiflcation of'm'y.

invention; Fig. '7 is a'view in section similar to Fig. Zof another modification of my-invention;-

and Fig. 8 is-a view, similar to Fig. 7, of the modi flcation of my invention shown in Fig. 6 taken on the plane representedby the line The thread hobbing machine shown in Fig. 1 1- 3 is of well known'type with which my flexible mandrel is ordinarily utilized. In general the hobbing machine comprises a base 1 upon which is rotatably' mounted a hollow head stock or chuck 2 having clutch jaws for receiving a tubular body hob 4 may be rotated by any suitable means such' as a motor 7 mounted on the carriage and connected to the hob bya transmission mechanism 8. During the cutting operation the carriage 5 is moved longitudinally of the base 1, at proper speed to form threads of the desired pitch onthe rotating pipe 3, by means of a lead screw 9 driven in synchronism with the pipe by a gear train 10 that connects it directly to the rotating head stock 2.

' To'insure that the force exerted by the hob 4 in performing the cuttingoperation willnotdistortthepipe 3, the end of the pipe is reenforced, in accordance with my invention, by an expansible mandrel 15 disposed within the pipe and held-in engagement with it in 'such'manner that the pipe is firmlyand rigidly supported in its normal relaxed position. Themandrel 15 ordinarily may be placed in position manually and operated to engage the interior of thepipe 3 by suitable'operating mechanism actuated by a T-handle' 16. The pipe 3 is shown in the drawings as being of truly circular cross section for simplicity of illustration, but it will be understood that commerciallyaccepted pipe is not made truly cylindrical but-varies from such shape to an appreciable extent. Fora better understanding of the construction of the-mandrel 15 that is adapted to support the pipe in itsnatural shape, reference may be had to Fig. 4 in which one supporting element 1'7 only" is shown in its retracted position within a tubular object 3; As shown, the supportingelement 1'7 comprises a plurality; of rigid members 18,-each of which is provided with two contact areas 19 for with the rigid members 18., the entire element 17 havingbeen cut froma singleplate of suitable 1 metal by a cutting torch or other cutting device! ii To expand the supporting e1ementf1'7 and move the'ccntactareas 19' into engagement with the inner surface of thetube 3, I provide a conical wedge member 22 that engages a seat 23 at theinner, edgeofreach rigid member 18.

' If We assume'that-theielement l'l is'initially out of contactwith the pipeS as shown in Fig". 4, it

may be readily-appreciated that'when the conical member "22 is. advanced axiallybetween the seats 23 0f the rigid members 18 it causes them to move outwardly untilone contact area 19 of one member 18 engages the inner surface of the, pipe. In-' asmuch as there-is no resistanceto movement .of

the other two-members 18' they will continue to move outwardlyuntil at least one contact area of each has also engaged-the pipe 3. 'Uponfurther' axial movement of the cone22 the rigid nembers 18" will pivot about theirinitial'points of contact with the pipe 3"'andwill-slide on the interior of the p pe and on the exterior of the cone 2' until position is reached in which both of the contact areas 19 on each of the members 18 engage the pipe 3.

In bringing the supporting element 1'7 into engagement with the interior of the pipe 3 at all six of thecontact areas only sufficient force need be exerted to overcome the tension in the springs 21, which is small, and to overcome the slight friction between the various members. as one or more of the contact areas 19 has not yet engaged the tubular object 3, the forces within the device are negligible, inasmuch as the mem- .bers not in full engagement with the pipe are free to move without substantial resistance until they do engage thepipe at both contact areas.

However, as soon as all of the contact areas have engaged the pipe 3, further movement of the cone 22 will set up substantial radial forces within the supporting element 1'7 that will oppose external radial forces that may be applied to the pipe during thread cutting or other machining operations and will set up frictional resistance to oppose change of shape of the element. In the preferred practical embodiment of my As long invention, shown in Figs. 1 and 2, I utilize two N in Fig. 2, and will stand in stablemanner while being manipulated toexpand it into engagementwith the tube. To distribute the forces exerted by the elements 17 and 27'about the tube 3, the

contact areas of the two elements are disposed in radial planes at angles of 30 to each other in such manner that twelve'substantially equally spaced contact areas are provided.- The angular relation between the elements 1'7 and- 2? is maintained by a pin 28 securely held in the plate 27 by a nut 29 and extending through a hole 39 in the plate 17. To permit limited relative motion between the plates 1'7 and 2'7, the hole, 30 is made somewhat larger than the pin 28 to provide adequate clearance space.

The flexible element 2'7 may be actuated by a cone 32 similar to the cone 22in the element 1'7 but extending into the element2'7 in the opposite direction. As shown in Fig.2, the elements 1'7 and 2'7 may be expanded simultaneously'by moving the cones 22 and 32 toward each other.

This may be conveniently accomplished by an operating shaft 34 provided with left and right hand threaded portions which cooperate with complementary internal threads in the cones 2 2 and 32, respectively. The shaft 3 is connected to the operating handle 16 by means of which it may 4 toward or away from. each other.

I To hold the elements 1'7 and 2'7 inspaced rela tion, the members 18 of each are provided on their adjacent faces with spacing members 35 1 that bearagainst each other. At the other sides of l the members 18 there are provided similar members 36 which serve to thicken theelements and provide relatively wide tapered faces 23 and 33 for, engaging the cones 22 and 32, respectively.

To prevent the cones from turningwith theoperating shaft 34, keyways 3'7 and 47 are provided in'the seats 23 and 33 of' the elements for co-' operating with keys 38' and 18 on thecones 22 and 32, respectively; The key 48' and the key- 7 be rotated to move the cones22 and 32 tion. However, incrder 'to'permit some-relative.

angular motion between. the elements 17 and," 2'7, the keyway 3'? is made somewhat larger than the key 38 in'the same manner and for the same In operation the mandrel 15 is placed within the tube '3 and the'h'andlelfi'is actuated to turn the shaft 34 in the clockwise. direction, as viewed from the'right end of Fig; 2. 1 This'causes the cones 22 and 32 to approach each other and to force the rigid members 18 of the elements 17 and 27 outwardly. Comparatively small forces 'will be required to turn the shaft 34 at first and the rigid members 18 will shift about slightly as they move outwardly until all of the twelve contact areas 19 engage the inner surface of the tube 3'. After the mandrel 15 has thus adjusteditself to conform to the interior configuration of the tube 3, further rotation of the shaft 34 will build up forces that act radially outward upon the tube 3 through'all of the contact areas 19 to support it inits normal or relaxed position. To effectively support the pipe 3 against distortion, the cones 22 and 32 are advanced to such position that the forces exerted upon the tube 3 by the members 18 are as large as can safely be ap- 25 plied without unduly expanding the tube. Inasmuch as the forces exerted by the cones 22 and 32 upon the rigid members 18 are substantially equal, the forces applied to the tube .3 .by the contact areas 19 are also substantially equal to each other regardless of the configuration of the interior of the tube 3. Further, during the time that the supporting forces are being built up there is practically no relative motion between the various parts of the mandrel, and, as the radial forces increase, tangential frictional resistances are set up tending to lock the elements 17 and 27 securely in position. I

As a result of the radial forces between the H contact areas 19 and the tube, frictional resist-' ances are established therebetween which oppose relative circumferential motion of the tube and the supporting elements 17 and 27. .Relative motion between the elements 17 and. 27 also is opposed by frictional resistance between the spacing members 35'which-results from the opposing longitudinal force exerted by the cones 22 and 32. To assist in locking the mandrel, the surfaces of the cones 22 and 32 are disposed at such angles to their axes as to provide for irreversible action between the cones and the seats of the members 18. Hence, after the cones havebeen moved within the elements to points in which the desired forces'are set up, theyare held from retracting by the frictional forces betweenv them and the seats 23 and 33. Likewise frictional resistances to motion are setup between the threads in the cones 22 and 32, and the threads of the shaft 34.

It is apparent that. afterthe mandrel 15 has been. expanded to apply the required supporting forces to the tube 3, the frictional resistances to motion that are set up between itsvariousparts and between it and the tube 3 are of such nature as to prevent relative motion between the elements of thedevice when the tube issubjected to externally applied forces. In order .to change the shape of the mandrel thus locked it would be necessary to rock or rotate one or more of the rigid members l8 relative tothe other members. Such relative rotationof the members wouldre sult in relative sliding motion between the members and the cones or the pipe. But. as has been explained, such relative sliding motion is effec- Q tively resisted by the large frictional forces setup between'the members and the various surfaces which-they engage. j

.After the mandrel has been expanded to its final position and locked by frictional resistance, it functions substantially as would a solid mandrel that had been carefully fitted to conform to the irregularities of the interiors'of the pipe. However, inasmuch as the mandrel engages the interior of the pipe at twelve separate and distinct positions, there. is a slight tendency to deflect the pipe from its relaxed shape towards'a shape in the nature of a polygon having twelve sides; That is, the pipe is. deflected outwardly; to a slight extent, at each of the points to which pressure is applied by the twelve contact areas of the mandrel. This deflection is. so'slight, however, that it has no appreciable effect uponthe accuracy of'the threads cut on the pipe while thus supported. In view of the negligibleeifect of this slight distortion it may be-saidithat, for.

-vide a mandrel for supporting pipe against the distorting effect of heavy forces applied .to. its

exterior while cutting threads on it. Y

With the mandrel thus locked in position with:

in the tube the exterior of the tubemay be threaded or otherwise worked upon without dan ger of springing or deflecting it and impairing the accuracy of. the work. -Afterthe threading or other operation has been performed the. man-v drel 15 maybe retracted for withdrawal from the tube by turning the operating handle 16 counter-clockwise, which operation causes the cones 22 and 32 to move away from each other. As the cones are separated the working forces within the mandrel l5 vare- 'gradua11yreducedto zero and'as the retracting operation progresses the rigid members 18 are drawn inwardly to their" inactive positions by the springs 21. The mandrel may then be withdrawn leaving the pipe in its original shape with accurately cut threads of true pitch diameter on its surface.

To prevent damage to the mandrel 15 in the event that the operating. handle 16 is actuated when the mandrel is not in .a pipe. that it is adaptedto support, the cones 22 and 32 are made of such length that they will engage each other at the mid-plane of the mandrel before the elements 1'7 and 27 can be expanded to stress the springs 21 beyond their elastic limits. Incidentally, the stresses within the spring 21 during normal use of the mandrel are quite low ihasmuch as the supportingforces are-transmitted directly through the rigid members 18. v

In the event that it is desirable to utilize one mandrel for supporting pipes of different internal dimensions, adapters or' lugs 39 may be applied to;

the rigid members 18, as shown in Fig. 5. In this view the lugs 39 are shown attached by bolts 40 tonne members 18 at each contact position 19. A set of lugs 39 may be provided for adapting the i mandrel 15 to each size-of pipe with which itgis to be utilized. 7 r u Under some conditions'it may be desirable to support the pipe at the ,position in which it is gripped by the clutch jaws of the chuck 2 as well;

as at the position upon whichz th'e cutting tool operates. If such support is provided the clutch jawsmay be disposed to engagethe pipe nearthe to rigidly grip the pipe without danger of distorting it. Apparatus for accomplishing the result is provided by the modification of my invene tion shown in Fig. 7. In this modificationtwo complete mandrel structures or units, ,eachsimilar to that shown in Figs. 1 and 2, are operatively connected to a common operating mechanism. As shown, one mandrel unit a isdisposed near the end of the pipe 3 'to support it against distor tion by forces exerted by the cutting tool 4a. To prevent distortion of the pipe bythe chuck2 another mandrel unit .4500 is disposed, somewhat farther within the pipe 3 at the position engaged by the clutch: jaws 2a of the rotating head stock.

The two mandrel units 1511 and a are spaced or positioned by a hollow compression member or nipple 47a. At the ends of the nipple 47a. are

. operating cones 420;, corresponding to'the cone threads of arelatively long operating shaft 34a that passes through the nipple 47a. As shown,

the cones 52a are at the ends of the apparatus and it is apparent that when they are moved toward each other by the shaft 3% they not only operate the particular element which they engage but also force'the other elements of the mandrel units on the cones 42a. Consequently, when the shaft 34a is actuated by the handle 16a to tighten I the apparatus within the pipe 3 all of the four having cones 42b at their ends, are provided for) vided with'small rollers or wheels 56b mounted areas engage the inner surface'of the pipe.

elements expand Lmtil all twenty-four contact AS the mandrel elements are forced von the cones 42a the entire apparatus is shortened somewhat and the mandrel units 15a and 45a are moved toward'e'ach other. Such motion can readily take place during the adjusting period when there is 'f very little frictional resistance to motion between the contact areas and the pipe; After all the contact areas engage the pipe and pressure is exerted by turning the shaft 34a farther there will be some slight tendency to move the mandrel units toward each other. However, this tendency is readily taken care of by deflection of the resil-. ient elements of themandrel. I 4

- In the event that it is desirable to support the pipe at more than two positions apparatus constructed in accordance with the modification of 'my invention shown in Figs. '6 and 8 maybe utilized. In this modification a plurality of mandrel units 1512,45!) and b, respectively,are all mountedon'a long 'operating'shaft 342); At the ends of the shaft 342) the usual right. and left threads are provided for engaging complementary threads in end cones 5219p Spacing nipples 47b,

separating the mandrel units.

As mandrel apparatus of this type may be made quite long, means areprovided for permitting. some of the units to move longitudinally of the pipe when the endcones-52b are drawn toward each other. To this end, all of the mandrel units" except the one at the endof the pipe are proat each contact position and disposed in radial longitudinal planes of "the pipe 3,-as shown in r Fig. 6.

From the "foregoing description of my. tube supporting mandrel and explanation of the manner in which. it operates, it is selfeevident that I have provided rugged and effective apparatus for firmly supporting 'a tubular object in-its normal or relaxed position to resistdistortion from externally applied forces. I Y 1 Although I have shown only a few specific embodiments of my invention and have described them in detail to adequately disclose the inven- .tion, it will be apparent tothose skilled-in the art that many modifications may be made in the details of the mandrels, as in the types ofspring elements utilized and'in the general configurae tion and number of the rigid members,without departing from the spirit and scope of my invention as defined in the appended claims.

I claim: I;

1. In a mandrel for providing, internal support to a tubular object of approximately circu lar shape in cross section, a plurality of supporting elements disposed in pairs in spaced transverse planes of the object to be supported, each of said elements comprising a plurality of rigid members provided'with a plurality of contact areas for engagingtheinner surfaceof the rigid members of each supporting element outwardly, the cones for-actuating each pair of elements being disposed to move toward each other, rigid means disposed to space the elements of each pair, compression members disposedxbe-r tween the conesat adjacent sides of successive tubular object, a cone disposed to actuate the g pairsto space the-pairs, and means for actuating ing equally all of the elements'of the mandrel.

with rollers disposed in radial transverse planes of the tubular object for .engaging'the inner sur face-thereof, a cone disposed to actuate the rigid members of "each supporting element outwardly, the cones for actuating each pair of elements being disposed to move toward each other, rigid'-- means disposed to space the elementsof each pair, compression members-disposed between the cones at adjacent sides of successive pairs to space the pairs, and means "for actuating the cones at the ends of the mandrelv to move them I toward each other and inv so. doing move the cones in each pairtoward each other for ex panding "equally all of the' elements ofthe mandrel. E

3.-Means for radially supporting a hollow work-piece, comprisinga plurality of engaging members arranged in a circle andmountedfor.

radial-movementand for tilting movement substantially in the plane of the circle, each of said" members having two independent contact areas spaced apart from each other, and means'for ex erting substantially radial pressure" upon said members in a direction towards said work-piece,

whereby each of said members iscaused to seat with both of its surfaces againstsaid work-piece.

4:. Means for radially supporting a hollow work-piece, comprising a plurality of" engaging members arranged in a circle and mounted iorf radial movement and for tiltingimovement sub spaced apart from each other, an axially movable wedge member Contacting said engaging members for moving them in a substantially radial direction, whereby each of said members is caused to seat with both of its surfaces against said work-piece. v

5. A mandrel for interiorly supporting a hollow work-piece, comprising a flat plate having portions thereof removed to produce a group of members arranged in a circle and having outerferentially of the circle, each of said bases having two independent contact areas spaced apart from each other, and their apexes directed toward the center of the circle and integral resilient portions connecting said engaging portions, and

means for exerting substantially radial pressure upon the apexes of'saidengaging-portions.

7. A mandrel for interiorly supporting a hollow work-piece, comprising a plate having por tions thereof removed to produce a group of sub-- sta'ntially triangular engaging; portions arranged in a circle with their bases disposed circumferentially of the circle, each of said bases having two independent contact areas spaced apartfrom each other, the sides of said triangles being con-' cave to produce spaces between said portions and the apexes of said portions being directed toward the center of the circle, and U-shaped integral resilient portions disposed in said spaces and connecting said engaging portions, and means for exerting substantially radial pressure upon the apexes of said engaging portions.

. GEORGE M. EATON.

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