US2080211A

US2080211A - Method of shaping metal

Info

Publication number: US2080211A
Application number: US614266A
Authority: US
Inventors: Joseph G C Mantle
Original assignee: BRIDGEPORT THERMOSTAT Co
Current assignee: BRIDGEPORT THERMOSTAT Co; BRIDGEPORT THERMOSTAT COMPANY Inc
Priority date: 1932-05-28
Filing date: 1932-05-28
Publication date: 1937-05-11
Anticipated expiration: 1954-05-11

Description

May l1, 1937.

J. G. C, MANTLE METHOD oF SHAPING METAL Filed May 28, 1952 s sheets-sheet 1- V vlll/III A'ITORNEY May l1, 1937. J. G. c., MANTLE METHOD OF SHAPI NG METAL' Filed May 28, 1932 5 Sheets-Sheet 2 lll Illll ATTORNEYS VMay 11, 1937.. 1 Q MANTLE 2,080,211

METHOD OF SHAPING METAL Filed May 28, 1932 5 Sheets-Sheet 3 uw E 91 mu: F

l F I mi fm Patented May 11, 1937 UNITED STATES METHOD OF SHAPING METAL Joseph G. C. Mantle, Leonia, J., assignor, by mcsne assignments, to Bridgeport Thermostat Company, Inc., Bridgeport, Conn., a corporation .of Delaware Application May 428, 1932, Serial No. 614,266

2 Claims.

The present invention relates to improvements in methods of shaping metal and is especially adapted to the production from metal tubing of a great variety of articles such as metal bellows usable for the expansible and contractible elements in thermostats and in pumps and for other purposes wherever suitable` This application is filed as a continuation in part of `my pending United States patent application, Ser. No. 726,671 filed July 18, 1924, Patent #2,044,710, dated June 16, 1936, entitled Method of and apparatus for making hollow articles, and Ser. No. 749,208 filed Nov. 11, 1924, Patent #2,044,711, dated June 16, 193,6, entitled Corrugated diaphragm and method of making the same. In addition to which my present application discloses other forms of .apparatus for practicing the invention.

The herein method is capable of making metal bellows from thin wall tubing with specially .deep corrugations for the bellows folds, the walls of which have the proper temper and cross sectional thickness in the metal thereof to be properly flexible and elastic for efficient operation .25 and long life. Further the method is adapted to make the folds substantially uniform one with another so that the working of the bellows will be distributed substantially equally among all the folds without being .concentrated more in some folds than in others to the ,detriment of the eiiiciency and life of the bellows.

The herein method comprises initially locking the dies (interchangeably known 4as dies, dieplates and forming members) to the tube or shell in desired spaced relation by differences in diameter of the shell at and `between the dies, which may for example, consist of circumfercntial creasings or grooves formed in the shell by prebulging or prerolling or in any other suitable manner; and the method further comprises then folding the metal of the shell outwardly between the dies by the combined action of internal fluid pressure and an axial contracting pressure on the shell; and this, without operating, governing or restraining the die plates by any positive means but on the contrary permitting them to fioat and move toward each other substantially unrestrained except for their aforesaid initial interlocked relation with the shell.

As stated, the die plates may be said to float with the shell whereby any section of the shell is free to form into bellows folds ahead of others, and the adjacent dies are free to come together without restraint by any positive means other than that imposed by the shell itself and by the anchorage of the dies in the creasings thereof.

By prebulging is meant initially expanding the shell against the surrounding dies by internal fluid pressure to form differences in diameter in the shell at and between the dies 'Sufficient to lock the dies to the shell. i

By prerolling is meant mechanically forming the differences in diameter of the shell by a,...

In this specication various preferred forms I of apparatus are diagrammatically shown for practicing the invention. VIn one form springs are used between the dies but their resistance to the floating movement of the dies is a freely yielding resistance which is insignicant irelatively to the magnitude of the axial shell-contracting pressure and the internal expanding pressure; and is not the resistance of a positive rigidly acting device.

Another form shows shouldered spacing rods which in their initial position engage the die plates and automatically space them evenly and properly along the tube or shell. However, `these spacer rods during the subsequent bellows fold operation are moved out of contact with the die-plates and therefore, have no restraining effect upon their movement; and this is irrespective of whether one pair of dies may move toward each other to form a bellows fold ahead of others.

In still another form, spacer blocks ,are temporarily located between the dies to position them evenly and properly along the tube or shell until it has been prebulged by internal iluid pressure; but after that these spacer blocks are removed and the subsequent bellows-fold forming operation takes place while the dies are fr ee to move toward one another unrestrained by any positive means other than the creasings or differences in diameter of the shell with which they are interlocked.

Mantle, Serial No. 726,671,1iled July 18, 1924 Except for typographical and immaterial corrections, the following excerpts pertaining to the present invention are quoted from this application as led. Also Figs. 1 to 9 inclusive, in the drawings are copied from said application as filed.

This invention is a method of and apparatus for the formation of articles from shells or tubes of ductile material. The shells and tubes are usually drawn from sheet material and are either flanged or plain.

The object of this invention is to rapidly and economically transform them into such shapes which, in general, could only hitherto be done by repeated annealings and operations, or, by first forming portions and then joining them together to form the whole.

In the drawings:

Figures 1, 2 and 3 show a flanged shell at different stages of the operation.

Figures 4, 5 and 6 are separate views of parts of the contractible mold shown in Figures 1, 2 and 3.

Figures 7, 8 and 9 show a flanged shell at diierent stages of the operation, the whole so arranged that the internal fluid pressure may be applied and the contraction of the contractible mold elected by the punch holder or slide of an ordinary power press.

Referring to Figure l: The iianged shell I is supported in a contractible-mold consisting of parts 2, 3 and 4. Each of the parts 3 and d consists of two complemental pieces, as shown in Figure 4, and they are supported and held together in holders 5 and 6. Figure 5 shows a holder; each holder has an annular portion and is provided with cut-away portions 'I corresponding to lugs 8 on the mold-parts 3 and 4, so that they may be placed therein and when given a slight twist they are supported and held together or prevented from spreading apart. Each holder has an attached set of springs 9, the free ends of which are adapted to fit into grooves I0 on the upper surfaces of the holders 5 and the mold-part 2. These springs sustain the holders in correct relation to each other, and also act as guides in preventing lateral movement. The holder 6 is secured to a top-plate II which is provided with a tube I2 which telescopes into a reservoir I3 containing uid under pressure. Between the reservoir I3 and the top plate II is a removable stop-piece Id. The stop-piece I4 having been removed, the top plate slid up to the reservoir, the holders with their mold-parts assembled on the mold-part 2, the shell placed therein, the holder 6 secured to the top plate and the stop-piece slid into place, the whole is ready for the operation, which is as follows:

Fluid, usually water, under a pressure varying in accordance to the nature of the shell, is permitted to pass through the tube I2 and ll the shell, and then by reason thereof and on account of the shell being longitudinally conf-ined, a change in shape occurs, as shown in Figure 2, viz., bulgings of the shell between the contacts of the mold-parts and creasings of the shell at the intermediate parts in contact with the moldparts, as respectively shown at I5 and I6 in Figure 2. Subsequently and whilst under sustained uid pressure the contractible-mold is compressed, preferably by a downward pressure y and applied by mechanical means to the top plate II, until the parts are positioned as shown in Figure 3, or, to any desired intermediate position. In the example shown, the mold-parts are equi-distant, and on account of the creasings I6 they approach each other equi-distantly during the whole of the compression of the contractiblemold.

In certain instances it is preferable to form these creasings (by rolling or otherwise) prior to the placement of the shell in the contractiblemold operation, in which case the compression of the contractible-mold may commence at the same time as the internal fluid pressure.

The shell or tube filled with a liquid, usually water, is placed in the contractible-mold and the internal fluid pressure is produced in the Figs. 1-3 apparatus by the downward movement of a plunger carried by the punch-holder or slide of the press, against and into the water or other liquid contained in the shell and at the same time the punch-holder or slide of the press operates mechanism which immediately afterwards compresses the contractible mold.

Referring to Figures 7, 8 and 9, the top plate II is provided with a sleeve I 'I through which operates the plunger I8 attached to the punchholder of the press. The sleeve II is provided with lugs I9 adapted to be acted upon by mechanism operated by the punch-holder of the press.

In the examples so far described, leakage of the iiuid is prevented by the nipping of the flange of the shell between the top plate and the uppermost holder. When a flangeless shell is used, some other suitable adaptation or arnangement as shown may be employed to prevent leakage.

The mold-parts may be positioned at their correct, though unequal, distances by means as shown in Figure l, for the creasings of the shell tend and usually suiiice to retain the correct proportionate spacings during the closing together of the mold-parts. even necessary, to provide means which positively or rigidly control this spacing of the moldparts throughout the operation.

Mantle, Serial No. 749,208, filed November 11, 1924 Except for typographical and immaterial corrections, the following excerpts pertaining to the present invention are quoted from this application as filed. Also Figs. l0 to 14 inclusive in the drawings are copied from said application as filed, except for immaterial omissions in some of said figures.

This invention relates to expansible-contractible metal elements such as are adapted for use in pumps, motors, or in pressure-sensitive or heatsensitive devices in general.

The method of manufacture consists in rst forming a shell from sheet metal, then forming the outwardly projecting gasket-flange, and then converting the shell to its final shape by the method and apparatus described in my pending application Serial No. 726,671, entitled Method of and apparatus for making hollow articles, and as will be further hereinafter described in connection with the accompanying drawings.

Figure l() shows the gasket-flanged shell after having undergone a. rolling operation.

Figures l1 to 14, inclusive, show diiferent forms of the complete articles when converted into iinal shape (by my Method of and apparatus. for making hollow articles) When the inner curves of the eorrugations are nearer the axis of the diaphragm than the inner surface of the opening IIB', then the shell is recessed inwardly, as is shown at I I6 in Figure l0 by a rolling operation. The manner and means for rolling these recesses is well known, and needs no explanation.

To convert either of the shells shown in Figure 9 (this is not Fig. 9 of the present application but refers to a ligure in Ser. 749,298, here omitted, showing an ungrooved cylindrical shell) and Figure 10 (showing pregrooved shell) to either one of the final shapes shown in Figures ll, l2., 13 and But it is often desirable, or

t'il

14, reference is made to my aforesaid prior application.

It can be readily understood that with a shell of given diameter and material, a deeper nal corrugation may be obtained by a p-rior corrugating of the shell, as shown in- Figure 10. Also, as a rolling operation increases the hardness, a higher temper is induced in the corrugation nearest the axis. By inspection of Figure 8 in my prior application for Method of and apparatus for making hollow articles, Serial No. 726,671, it will be seen that when the shell is placed in a contractible-mold subjected to internal Huid pressure there is an analogy to a uniformly loaded and equidistantly supported beam, and that the stress is greatest, and consequently the shell is thinnest and hardest, at the portions midway between the supporting surface of the mold parts of the contractible mold and is thicker and softer the nearer it is to the mold parts. Now, the degree of this variation of hardness, due to the thinning of the material, is of course dependent upon the nature of the material and upon the applied pressura Were the material soft pure rubber, there would be practically no variation in thickness. With low brass (low percentage of zinc), it is found that there is but a very gradual increase in thickness and decrease in hardness of the material from the outer to the inner corrugations, and that they are fairly uniform throughout their lengths. By the prior rolling of the inner corrugations, as in Figure 10 of this application, and by suitably adjusting the internal uid pressure, the inner and outer corrugations may be given any relative degree of hardness as may be desired. At the completion of the operation of corrugating the diaphragm, the thickness of the material throughout the length of the corrugations is appreciably less than that of the original wall. The amount of this diminution isl dependent upon the kind of material. It is found that brass consisting of 85% copper, 15% zinc, may be safely stretched fully or, in other words, until its thickness is about 83% of its original thickness (by my Method of and apparatus for making hollow articles). This amount of stretch is well within its safe limit, for a series of diaphragme so made have already performed over 700,000,000 pumping operations (in extension and contraction), and are now apparently still in sound condition.

In forming a diaphragm where the corrugations are required to be equidistant, it has" been found to be unnecessary to provide means for positively controlling the relative movements of the mold parts towards each other during the operation of forming the corrugations, but, when they are required to be unequally spaced, or are of varying forms, then such positively controlling means are necessary.

It is to be understood that these diaphragms may be made of any suitable material for the purpose required.

Method in re Figures 15-17 inclusive Figs. 15-17 inclusive show diagrammatically another form of apparatus or collapsible mold, for practicing the invention wherein:

Fig. 15 is a front elevation, partly in vertical section, of the apparatus, with the parts hinged .open and indicates a shell in position by the full lines ready for the parts to be closed and locked and for the prebulging operation, and after that for the bellows-fold forming operation.

Fig. 16 is a plan view of the lower head plate,

the buiging-open thereof being indicated by the dotted lines, this View also indicating the spacer blocks in plan; and

Fig. 17 is a diagrammatic view showing, in vertical section partly in elevation, a form of fluid pressure creating means shown connected to a fragment of the head portion of the apparatus of Fig. l5.

The apparatus comprises a base plate 40, the top of which may be formed with a circular recess il adapted to receive the bottom of the cupshaped shell 42. The head of the apparatus consists of two superposed plates 43 and 44 adapted to clamp between them the flange 42a at the mouth of the shell and the rubber gasket 45.

Parallel rods 46 pass through aligned holes in the head and base plates. The ends of these rods are screw threaded to receive nuts as shown. The nuts 4l and pins 48 serve to clamp the flange of the shell and the gasket 45 as aforesaid, fluide tight between the two head plates 43 and 44. These rods 46 slide freely through the holes in the base plate 4E); and the nuts 49 on their lower ends serve to hold this plate from separating from the rods.

The lower head plate 43 is made in two partable hinged together sections. What may be termed the main section 43a is the section through which the rods 45 pass. The other section 43h is hinged or pivoted at 5B to the main section to swing in the plane of the other section. This lower head plate 43 is also a die and for this purpose its two sections are formed with complementary circular recesses whose rims 5l when the sections are together, bellows-fold forming member or die circumferentiallysurrounding the shell 42. 52 is a latch for releasably locking together the free ends of the two sections of the lower head plate. This latch is located in a groove in the end of the main section 43a and swings or pivots in the plane thereof on a pin 53. The latch is notched at 52a to engage a pin 54 in the grooved end of the other section 43h.

The detail of the hinge connection between the sections 43a and 4312 is best shown in Fig. 16 when compared with Fig. l5 from which it will be seen that the swinging section 43h has a thinner rigid extension 43e extending at a right angle therefrom, swinging about the pin and receivable like a knife blade snugly in and out of a groove in the end of the main section 43a. This construction gives rigidity to the two sections of the lower base plate in the plane thereof as does also the latch 52 locatable also like a knife-blade snugly in its groove as above de` scribed.

When the sections 43a and 43D are latched together they abut along their inner edges as shown by the full lines in Fig. 16. Again referring to the plan View Fig. 16, it will be seen that one section, which as shown may be the swinging section li3b, is formed at its inner longitudinal edge with a projecting portion or portions 55 shaped to be received snugly into a correspondconstitute a circular ing recess or recesses in the inner longitudinal edge of the other section 43a, whereby these sections when in latched together relation are restrained from longitudinal movement or slip on each other.

Hinged partable die plates 56 are slidably mounted on the guide rods 46. Generally speaking, each of these is constructed similarly to the lower head plate 43 just described. Thus, each die plate comprises a main section 56a (through which are the holes for the guide rods 46), and further comprises another section 58h hinged to the main section at 5l to swing in the plane of the main section. Also the two sections of each die plate are formed with complementary circular recesses whose rims 58 together make a circular bellows-fold forming member or die circumferentially surrounding the shell when positioned in the apparatus. Also latch means 5S is provided in connection with each die plate for releasably latching together its two sections. Also the details of the hinge connection between the sections 55a. and 56h of the die plates is or may be the same as already shown and described in connection with the lower head plate; and the same is true as to the details of the aforesaid latch means 59; and as to the interlocking of the inner longitudinal edges of the sections against longitudinal slip on each other.

With this form of the apparatus, the shell is preferably initially pre-bulged in the apparatus before forming the bellows folds. In order that the prebulgling shall lock the die plates to the shell properly spaced along the shell, I provide and insert suitable spacer blocks or rectangular cross-sectioned members @il between them. After the shell has been prebulged by the internal uid pressure into interlocking relation with the dies, it will be understood that these spacer blocks 6B are removed preparatory to the next operation which is the forming of the bellows folds.

6| designates a plug screwed into a threaded hole through the upper head plate 44, located over the mouth of the shell when the latter is in position in the apparatus. This plug has an axial hole through it or bore arranged to seat a ball or other suitable valve 62 at or towards the outer end of the plug backed up by a spring 63 for normally seating the valve against its seat. The hollow plug 6| is provided with pins B4 for coupling it and the shell with a liquid or fluid pressure creating device or means 65. One simple kind of such means usable for the purposes of the invention is conventionally shown in Figs. and 17, and is commonly known as a grease gun. It comprises a cylinder A and a piston B having a screw-threaded piston rod C which projects through a correspondingly threaded hole in the head of the cylinder and is provided with an operating handle D at its free end. Connected with the other end of the cylinder is a flexible non-collapsible tube E having a coupling F at its free end. This coupling is a tubular member receivable over the plug 6| and has bayonet slots G in its walls engageable with the pins 64 on the plug whereby due to this and an intervening gasket and other well known adaptations not necessary to be shown a liquid tight under pressure connection is made between the grease gun 65 and the interior of the shell in the apparatus. Assuming that the grease gun is connected as described with the tubular plug 6| of the apparatus, and that it is filled with grease or oil and that the shell 42 is similarly lled, the gun is operated by turning the handle D to screw the piston forward to force more of the contents of the cylinder past the valve 62 of the plug and into the shell to create the desired hydraulic pressure therein as and for the purposes of the invention as hereinafter described.

The aforesaid apparatus of Figs. 15-17 inclusive is used to practice the invention with prebulging as follows.

The nuts 41 will be removed and the upper head plate 44 taken off. The spacer blocks 60 will then be inserted as shown in Fig. 15 to space the dies properly, which is usually equidistantly from one another along the shell. Also the lower head plate 43 and all of the die plates 56 will be unlatched and opened up on their hinges or pivots. The flanged cup or shell 42, either then or later lled with a suitable liquid, oil or grease, is then inserted in the apparatus as in Fig. 15 with its flange 42a supported by the die portion 5| of the lower head plate 43 and with its bottom located either somewhat above or in the recess 4| of the base plate. The sections of the die plates and of the lower head plate will then be closed about the shell and latched. The upper head plate 44 can now be put into position and the nuts 41 applied and screwed down so as to clamp fluidtight the flange 42a. of the shell and the gasket 45 between the upper and lower head plates. The liquid or fluid pressure creating device 65 will then be operated to creat-e an internal fluid pressure within the shell just sufficient to bulge or expand its walls outwardly against the dies to crease said walls at the dies suciently to lock the die plates to the shell. The dotted lines 42h in Fig. 15 indicate these creasings which for purposes of clear illustration have been exaggerated. The die plates being now locked to the shell by the aforesaid so-called prebulging operation in the space-d relation accomplished by the spacer blocks 6?, these latter having then served their purpose are removed so that thereafter the die plates are free to float unrestrained by any means other than the shell to which they are locked by the creasings thereof. The pressure creating device 55 may then be uncoupled from the plug 6| without, however, affecting the fluid pressure in the shell which will be maintained by the automatically closing valve 62 of the plug.

The head of the apparatus will now be forced toward the base by the use of any means suitable for the purpose such as a press whereby the shell becomes bulged or expanded outwardly into corrugations or bellows folds between the dies by the combined forces of the axial contracting pressure due to the press and the internal fluid pressure. During this endwise contraction of the shell, the internal pressure therein is maintained in suicient amount to keep the walls of the shell in tension and compel the metal between the dies to roll or fold outwardly along curved lines. Crimping of the corrugations between the dies is thus avoided. As the tube or shell contracts in length and the folds are formed, its capacity is deer-eased and the fluid pressure therein rises. The valve E2 may be momentarily opened at intervals by pressing it inwardly so as suitably to relieve excessive fluid pressure within the shell. It is preferable to maintain this pressure substantially uniform during the bellows-fold forming operation and substantially as it was during the prebulging step. However, it will be understood that there is considerable latitude as to the pressures which may be used.

Because the spacer blocks have been removed as a preliminary to the bellows-fold forming operation, and because there is no other positive means except the creasings in the shell restraining the free movement of the die plates, it will be evident that any of the bellows folds is free to form ahead of the others unrestrained except for its interlocked relation with the creased shell.

Method in re Figures 18-20 inclusive These figures show diagrammatically still snugly through it the base of the pressure relief device 9|. In eiect the gasket is an inverted cone, in other words, its lower side inclines upwardly and outwardly from the center towards the periphery. y

` To practice the invention with this apparatus,

Figs. 18 to 20, the nuts 8|, and the upper part l5 of the head will be removed. The apparatus being assumed to be resting on a table or bench 10 in vertical position as in Fig. 18, the rods 'I3 loose in the base 1D with their lower ends bearing against vthe top of the table will uphold the lower plate 'I6 of the head; and at this time the shoulders 81a of the spacer rods 81 will uphold the die-plates 83 as indicated in Fig. 18 in properly spaced relation. The swinging sections of the die-plates 83 and of the lower head plate 'I6 being assumed to be open, the pregrooved shell 12 can then be inserted laterally into the appa- 2Q ratus into the position shown in Fig. 18 with the grooves 12b of the shell tting and receiving the

bellows-fold forming rims

80 and 85 of the main sections of the die-plates and of the lower head plate. The hinged sections of all of these will 25 then be closed and latched to the main sections. The shell or cup will then be filled with kerosene or any other suitable liquid. 'Ihe upper l part 15 of the head will then be placed in position on the rods 'I3 and the nuts 8l will be 30 applied 4and tightened to clamp the gasket 82 and the flange 72a of the shell fluid-tight between the upper and lower parts of the head. During the foregoing, liquid will be displaced from the cup by the dipping of the pressure relief device 35 9| therein and will overflow at the brim of the cup leaving the cup including the space covered over by the gasket entirely lled with the liquid when the gasket 82 begins to be compressed, after which time no more liquid can escape at the brim or ange of the cup. During the subsequent tightening of the nuts 80, the further compression of the thick rubber gasket 82 puts said liquid under compression and applies an initial hydraulic pressure to the interior of the cup.

The apparatus may now be stood on the bed plate of a drill press or the like with the lower ends of the rods 13 located to pass freely through holes or slots in said bed plate and so that the lower ends of the spacer rods 81 can do likewise. At this time, because the rods i3 are no longer supported at their lower ends, the shell or cup bottoms itself in the recess 'Il of the base of the apparatus. The stem 15a of the head of 55 the apparatus will then be inserted in the toolholding chuck of the press.

` The bellows-fold forming operation can now take place by operating the press to force down the head of the apparatus towards the base. This applies axial contracting force to the shell; and at the same time hydraulic pressure within the shell acts outwardly against the walls. 'I'he result is that the walls of the shellfold outwardly between the dies into bellows folds 12e. 65 Coincident with the formation of these folds, the 1 descending head shortens the overall height of the shell; and the dies, due solely to their engagement with the grooves of the shell, are carried closer together until they are collapsed, one on top of the other, at the bottom of the apparatus when all of the bellows-folds have been formed.

In this forming operation, one bellows fold is entirely free to form independently and ahead 75 of others without any restraint other than that imposed by the shell itself and the anchorage of the dies in the grooves thereof. The shouldered spacer rods by their design and mode of operation have no effective contact with the die-plates after the head starts to descend, because immediately the shoulders of the rods progressively move further and further away from any supporting contact with the die plates.

As the shell shortens, its capacity is decreased and the internal hydraulic pressure increases; and this is automatically relieved by the pressure relief `device 8l to prevent an excessive pressure from overstretching or rupturing the metal. To this end, the spring 95 of the pressure relief device is initially set by adjusting the hollow screw plug 91 so as to permit the valve 94 to open and relieve the hydraulic pressure whenever it exceeds that necessary, suitable or preferred to properly form the bellows folds acting in conjunction with the axial contracting pressure on the shell.

It will be seen that in the method practiced as described with all forms of the apparatus, the dies are initially interlocked with the tube or shell by differences in diameter formed therein by a prebulging or prerolling or other suitable operation; and then in the subsequent bellowsfol-d forming operation, the dies float with the tube unrestrained by any positive means other than their aforesaid interlocked relation with the tube.

An advantage of prerolling is that it is a means of satisfactorily adding to the deepness of the folds and imparting desirable temper thereto as explained. An advantage of prebulging is that it permits the successive steps of the method to be practiced in one and the same apparatus to produce the complete product.

The use of this method is not restricted to shells and tubes of a circular cross section. Moreover by modifications well known in the art, the apparatus may be modified to take bottomless tubes or shells. It is also obvious that the contractible mold made up of the described die plates and head and base members may have any suitable transverse or longitudinal internal form either curved or rectilinear. Neither is the method limited to uniform or concentric enlargements around the axis of a shell or tube. In other words, the method is not restricted to producing symmetrical shapes only. Instead of liquid pressure, it is possible to use fluid gaseous pressure.

It will be understood that a pregrooved or prerolled shell may be used with the apparatus of Fig. 15; and that the prebulging process described in connection with Fig. 15 may be carried out with the apparatus of Fig. 18.

It will be appreciated that the above disclosures are given by way of example and that the foregoing and other modifications may be made without departing from the scope and spirit of the invention.

What I claim is:

1. A method of making hollow metal corrugated articles, which comprises placing a tube in a vertically arranged contractible mold having movable and spaced mold parts and locating the, mold parts without positively holding the mold parts before the mold parts are locked to the tube, bulging the tube by applying internal fluid pressure thereto to form differences in diameter in the tube sufficient to interlock with the mold parts, and then contracting the tube in length to `form corrugations therein by the combined another form of apparatus or collapsible mold for practicing the invention wherein:-

Figure 18 is a front elevation partly in vertical section of this apparatus, with the parts hinged open and further shows a pregrooved shell in position ready to have 'the mold parts closed together and locked to the shell preparatory to the bellows-fold forming operation.

Figure 19 sho-ws the apparatus or mold of Fig. 18 'collapsed and shows the walls of the shell formed into bellows folds; and,

Figure 20 shows the pressure relief valve of Fig. 18 in vertical section and on a larger scale in connection with a fragment of 'the head Vof the apparatus.

This apparatus is similar in many respects to that just described, but provides shouldered spacing rods 81 for initially automatically spacing the'dies to correspond with-and t into prerolled grooves or creasings of the shell when inserted in the apparatus. Moreover during the bellowsfold 'forming operation, these shouldered spacing rods are automatically moved and kept out of any interfering position with the die plates.

Briefly, this apparatus, like the other, comprises a base 1G in the'topof which is formed a circular recess 1l wherein to bottom the oupshaped shell 12. The'head of the apparatus, as

. before, is supported on parallel rods 13-13 which are 'slidable in vertical holes through the base on opposite sides of the recess therein. The head 14, as before, `consists of two superposed parts, van upper cylindrical part 15 loose on the rods 13 .and a lower part or plate 16 pinned at 11 or otherwise permanently fastened to the rods.

The :lower head-'plate 16, as before, consists of two `hinged partable sections. The main section 16a, as before, is the vpart through which rods 13 pass and which is permanently fastened tothe rods. The other section 1Gb, as before, is hinged at 18 to the `main section to swing vin the same plane. A latch lgreleasably locks together the sections of the lower Vhead plate. The sections, 'as before, have complementary 'circular recesses whose rims 811, when the sections are togethenconstitute a circular bellows-fold forming member or die surrounding the shell.

vAs before, the flange k12a at themouth of the shell'is adapted to be received and clamped between the upper and lower head parts by taking upon the nuts 8l on the screw-threaded upper ends 'of the rods. A rubber gasket 82, although differing in detail, is interposed as in the other apparatus to'make the joint fluid tight.

surround the shell.

As before, hinged partable die-plates '83 are slidably mounted on the guide rods 13. Also each die-plate consists of a main section 83a wherein are the holes for the guide rods; and further consists lof `another `section 83h `hinged to the main Vsection vatli to swing in the same plane. Also the'two sections 'of each die-plate are Yformed with complementary recesses whose rims 85 together make a circular bellows-fold forming member or die adapted to enclose and As before, latch means 86 including related parts is provided in connection with each die plate for releas'ably locking together itstwo sections, like the latch'SZ and related partsinFig. 16.

' As stated, the tube or shell 12 preferably used with this type of apparatus will be 'of the prerolled type, (compare Figure 10) in vother words, will have been already inwardly 'grooved by a rolling operation or the like with v'grooves 12b corresponding in spacing with the requirements of the finished article, which in the case of a bellows will be usually an equidistant spacing. In this casethere will be as many die-plates as there are grooves in the prerolled shell; and preferably means will be provided for automatically properly spacing the dies relatively to one another so that when the pregrooved shell is inserted in the apparatus and the partable die-plates are closed, these will automatically seat themselves in the grooves.

Such automatic spacing means mayof course take a variety of forms. That shown consists of a pair of shouldered rods 81 depending from the head of the yapparatus to which the rods are secured between shoulders on the rods and nuts on their screw-threaded upper ends. These rods pass through holes 88 in the main sections of all of the die-plates, said holes progressively increasing in ydiameter as shown from the top die to the bottom die. The rods are provided with shoulders 81a., one for each die-plate, which similarly increase in diameter so that each shoulder can pass freely throughthe hole in the die-plate below it whereas it is too large to pass through the hole in its own die-plate, namely the die which it is intended to support. The result is that when the head of the apparatus has been raised into its starting position preliminary .to the bellows-fold forming operation, .it supports the shouldered spacer rods 81 in a position (compare Fig. 18) wherein the shoulders of these rods in turn support and properly space the die plates 83 so as to t automatically into the grooves of the prerolled shell when the latter is inserted sidewise into the apparatus.

`811 is a duct extending through the lhead-part 15 from its bottom through to itsperiphery. This duct is for relieving the hydraulic pressure within the shell during the bellows-fold forming operation, and for this purpose its inner end is screw-threaded to make tight connection with the externally threaded stem 90 of a pressure-relief device of any desired or preferred form. The particular pressure-relief device 9| shown diagrammatically herein, comprises an axially hollow casing 32 formed at its lower end with a seat 93 for the ball valve Sli. In this casing is located a coil spring 95, adjustable as to compression, looselysurrounding the rod 98 and located between a peripherally serrated collar 96a on said rodand an axially hollow plug S1 in the upper end of the casing 92, said plug for up and down adjustment having screw-threaded .connection with internal screw threads of the casing in order to adjust the compression of the spring. This hollow plug S1 at its upper end has ascrew driver slot 91a .for adjusting it. The serrated collar 96a bearson the ball Valve.

The following .further details in connection with the particular apparatus illustrated in Figs. 18-2'0 should be mentioned. Thus the base 1D has vertical holes 10a for loosely receiving the lower ends of the shouldered rods 81 through them. The rods 13 are preferably long enough so that when the apparatus is `supported uprightly on va table or bench, these .rods upheld by the bench in turn support the head of the apparatus .as well as the shouldered spacer rods 81 and the diepla'tes 83, .as indicate-d in Fig. 18, whereby the pregrooved shell 12 can be ins-erted laterally into position in the previously opened dies with its bottom preferably clearingthe recess in the loottom plate '18 so as topermit the direct lateral insertion of the shell. The gasket 82 .is .a rather thick rubber disk having a center hole receiving encircling relation with a hollow article by means of differences in diameter in the hollow article at and between the mold parts, and then forming the portions of the hollow article between the mold parts into corrugations by the combined action of an internal fluid pressure within the hollow article and an axial contracting pressure applied to one end of the hollow article while permitting movement of the mold parts with the hollow article during contracting 10 thereof.

JOSEPH G. C. MANTLE.