US2514507A - Method and machine for pointing tubes - Google Patents

Description

P. MUELLER METHOD AND MACHINE FOR POINTING TUBES July 11, 1950 4 shee'ts sheet 1 Filed D90. 8, 1944 INVENTOR ZATTORNEYj July 11, 1950 P. MUELLER METHOD AND MACHINE FOR POINTING TUBES 4 Sheets-Sheet 2 Filed Dec. 8, 1944 INVENTO R ZZZ/Z July 11, 1950 P. MUELLER 2,514,507

METHOD AND MACHINE FOR POINTING TUBES Filed Dec. 8, 1944 4 Sheets-Sheet 5 INVENTOR BY W July 11, 1950 P. MUELLER 2,514,507

METHOD AND MACHINE FOR POINTING TUBES Filed Dec. 8, 1944 4 Sheets-Sheet 4 INVENTOR BY t M A TQRNEY;

Patented July 11, 1950 UNITED STATES PATENT OFFICE METHOD AND MACHINE FOR POINTING TUBES Claims.

This invention relates to method and apparatus for pointing tubes that are to be drawn.

One object of the invention is to provide a more eflicient and more effective method, for pointing tubes. The invention collapses the end portion of a tube by the application of pressure at a number of spaced points around the circumference of the tube, and the. pressure for the complete pointing operation is, applied in successive stages. In the preferred method of applying the invention the tube is collapsed by pressure at four equally spaced points to form a cross section that has four lobes, that is, a clover leaf shape. In a second stage of the pointing operation pressure is applied to the lobes to fold them inwardso that the final point has eight lobes folded in upon each other to make a point that is substantially solid. The invention is not limited to forming with four and eight lobes, but such forming produces a point of minimum transverse dimensions and one that is of generally square section which fits readily into alligator jaws such as commonly employed with drawing tongs.

An important advantage in this invention is that the point'formed is of such small cross section that two draws can be made before repointing. This not only saves time, but it reduces the scrap losses because the end of the tube has to be cut-off prior to each subsequent pointing.

Another object of the invention is to provide improved apparatus for pointing tubes by means of punches that squeeze the tube from several directions instead of hammering from opposite ends of one diameter. Both noise and maintenance are reduced.

Other objects are to provide pointing apparatus that can be used on tubes having different wall thicknesses and a wide variety of diameters, without adjustment or change of parts, and to provide apparatus for pointing tubes at higher rates of production.

Other features of the invention relate to mechanism for operating the punches of the pointing :die, to automatic control means responsive to the insertion of a tube into the die, and to adjustments for controlling the force that the die exerts against the tube.

Other objects, features and advantages of the invention will appear or be pointed out as the description proceeds.

In the drawings forming a part hereof in which like reference characters indicate corresponding parts in all the views:

Figure l is a rear elevation of a tube pointing machine embodying this invention.

Figure 2 is a side elevation of the machine shown in Figure 1.

Figure 3v is a fragmentary front elevation of the die and part of the operating mechanism .of the machine shown in Figure 1, the centering chuck and. its operating mechanism being omitted.

Figure 4 is a sectional view taken on the line- 4-4 of Figure 3, with a tube in place and ready to be pointed.

Figure 5 is a detail sectional view taken on the line 5-5 of Figure 4.

Figure 6 is a side elevation ofthe tube of Fig-,

ure. iafter the tube has been pointed.

Figure 7 is an enlarged view, mostly in section, of the cycle control valve shown in Figure 1.

Figure 8 is an enlarged end view of the tube after thefirst collapsing operation of this invention.

Figure 9 is an enlarged end view of the tube shown in Figure 6, this figure being also a view of the end of the tube of Figure 8 after the tube has been subjected to the second stage of the pointing operation, the position of the tube being turned 45 in Figure 9 from the position shown in Figure 8.

Figure 10 is a fragmentary sectional view taken on a vertical plane coincident with the axis of the work receiving opening of the machine.

The machine shown in Figure 1 includes a housing II supported by a pedestal I2. Within the housing I I there is a cam wheel I4 with gear teeth around its periphery. These gear teeth mesh with the teeth of racks I5 and I6 located on opposite sides'of the cam wheel I4. The racks I5 and I6 slide in stationary bearings in the housing I I and are-connected at their lower ends 25 respectively by fastening means such as rivets 28. The outside surface of the ram guides 25 and 21 are flush with the outside surface of the face plates 24 and 25, but the ram guides extend inward beyond the face plates 24 and 25 and have channels 30 in which are guided the rams that hold the punches for pointing the end ofatube.

4 die is intended to be used that the sides of the tube are not bent into contact with one another before the highest portions of the cam sections 45 have passed over the rollers 4|.

Further clockwise movement of the cam wheel i4 causes the cam sections 45 to pass to the rollers 41 of the rams by which the second set of punches 33 are carried. During this continued movement of the cam wheel l4, :the rams that carry the punches 32 of the first set are returned to their original positions, by means toms against the end of the channel. Retaining pins 31 merely prevent the punches'from drop,- ping out of the channels. fit loosely into recesses in the punches and do not take any shearing stress.

In the operation of the apparatuatheipimches 32 move inward simultaneously against the side These retaining pins.

which will be explained, and the cam sections 45 displace the rollers 4| which control the movement of the second set of punches.

It is a feature of the invention that punches 33 are of such length that they collapse the end of the tube as solidly as'possible before the high points of the cam sections 45 have fully displaced the rollers of a tube 39 and deform. the tube into a four lobe or clover leaf form such as shown in Figure 8. The original full diameter of the'tube is shown in the background. The punches 52 are returned to their original positions, shown in Figure 3, and the second set of punches 33 are then moved against the surface of the tube at points intermediate the regions where the force was applied by the first set of punches 32-.

The punches 33 have center points that strike the lobes of the tube end and indent the mid portions of each lobe and push down also on the metal of the lobe to either side of the center point so as to crush the lobe and force its outer sides into contact with the outer sides of the adjacent lobes so as to obtain the deep and closed folds shown in Figure 9. The same crushing pressure applied to the lobes forces the outside surfaces of the indented portions into contact with the inside surfaces of the respective lobes on which the indented portions are folded back, to produce the cross section shown in Figure 9. In Figure 8 the tube is folded to a contour in' which the collapsed walls are in contact with'one another. Whether or not the first stage of the pointing operation brings the inside walls of the tube into contact depends upon'the wall thickness of the tube. The second stage of the pomp ing operation always collapses the tube to a -sub-' stantially solid section, that is,; a section in which the various folds are brought as close together as possible. i

The rams are guided on both sides by the channels or guidestll of the ram guides 26 and 21. Each of the rains 35 has a roller 4| supported from the ram by an axle 42-. The force for moving the rams 35 inward to exert pressure against the tube is applied to the rollers '4! by a cam face 44 on the inside surface of the cam wheel 14. The contour of this inside surface is shown in Figure 3. The surface is circular, with its center of curvature coincident with the axis of the tube 39, except for four cam sections 45. As the. cam Wheel Mrotates clockwise (Figure 3), the cam sections 45 first striketherollers 4! of the rams 35 that carry the-first set of punches 32. The cam sections 45 displace these rollers 41 and cause the first set of punches 32 to move inward simultaneously far enough to collapse the tube into the clover leaf contour. It is a featu re, of the invention that the first set of punches 32 do not move to their limit of travel before the highest points of the cam sections 45 pass, over the rollers M of the'rams that operate the first set of punches. This means that thelength of the punches 32 mustbe'so chosen with respect to the maximum wall thickness with whi'c'ht-he 4| that control this second stage of the pointing operation. The cam wheel I4 is therefore stalled by the pressure of the punches 33 against the tube 39; and the cam wheel I4 is made with a heavy section so that it operates as" a flywheel and transmits a substantial amount 'of energy for crushing the tube-in the final stage of the pointing operation.

The invention 'is not limited to the use of four punches for each stage. Three punches may be employed in-each set, but the result is not as satisfactory as with four becausethe size of the final point is larger when-three punches are used in each set, and the. shape of the point is not as Well adapted to use in. conventional alligator jaws such as. commonly employed for tube drawi g tools.v One of .the principal advantages of the use of four punches for each stageof the pointing operation is that the final point, as shown in Figure 9,v has as uare outline that is easily and effectively gripped by alligator jaws. This formhas four lobes with each lobe folded inward at its mid-point to make the original lobes double. 5

The structure for returning each of the rams 35 to its original position, after the punches have been thrust inward against the tube, is. shown in Figure 3. and 4. The cam wheel [4 has a cam track 46 in its rearward face and each of the rams 35 has an extension on one side that supports a cam follower roller 4: that runs in the cam track 45. An axle 48 connects the cam follower 41 to the ram 35. The portions of the cam track 48 that overlie' the cam sections 45 are chords of thecam track circle. The cam followers 4'! receive no support from the middle portions of these chord sections 49 of the cam track 45 and the rams 35 are, therefore, free to move inward when displaced by the cam sections 45.

The portions of the cam track 45 intermediate the chord sections 49 are circular about the axis oftthe tube as a center and these circular portions of the cam track. 46 hold the rams 35back from the tube 39. As the end portions of the chord sections 49 pass under the rollers '47. after the punches have, beenthrust inward against'a tube, the rollers and their associated rams 35: are pulled back away from the tube and reach such-as screws 52. Chuck jaws 53 slidein guides 54 in the body portion of the chuck and are aerate? moved radially by cam followers 56 that extend into cam slots 51 (Figure 5) in a cam plate 53. The chuck 53 has a hub portion that serves as the supporting bearing for the cam plate 58. Extending into the front end of the center opening through the chuck is a bushing 59 into which the tube fits. This bushing is retained in the end of the chuck as a holder by detachable fastening means comprising a set screw 68, and when the machine is to be used for tubes of different diameters, a bushing 59 to fit the particular size of tube is preferably put into the end of the chuck and secured in place by the set screw 69. No other change or adjustment is necessary, and this bushing is not essentialif the tubes are inserted carefully.

The cam plate 58 has a limited angle of movement and this movement is imparted to it by an arm 62 that extends upward from the cam plate 58. A pin fifiattached to the upper end or" the arm 62 extends through a slot t l in the face plate 24. The end of the pin 63 extends between downwardly extending lugs 65 of a friction band 61 which is made of Spring material and confined in a groove 68 in the front face of the cam wheel 14 opposite the cam track 46.

The friction band Bl rotates with the cam wheel it through a limited angle and further rotation is prevented by the pin (it which can move only as far as the limits of movement imposed by the travel of the chuck jaws 53. This means that initial rotation of the cam wheel it turns the cam plate 58 to make the jaws grip the tube when the cam wheel is making its working stroke and release the tube when the cam wheel i4 begins to turn in th opposite direction.

As soon as the jaws 53 have reached their limit of movement, the pin 63 cannot move further and the friction band El slips with respect to the cam wheel It during the remainder of the rotation of the cam wheel in the same direction. This construction has the advantage of operating the centering clutch 50 during the first part of the rotary movement of the cam wheel it no matter which way the cam wheel turns, and regardless of how far the cam wheel has turned before being stalled by the second state of the pointing operation.

The cam wheel i4 is turned clockwise in Figure 3 by downward movement of the rack l5 and upward movement of the rack 56. Movement of the racks in the opposite direction causes counterclockwise rotation of the cam wheel It. In the illustrated embodiment of the invention the cam wheel M turns clockwise during the working stroke, that is, the operation of the punches 3 and 33 by clockwise movement of the cam sections 45 applies force to the tube to form the point. The first set of punches 32 are also operated through an idling stroke during the return movement of the cam sections 45 but this idle operation does not take place until after the tube is removed from the apparatus, special provision being'made for returning the cam wheel hi at a slower rate than its movement during the pointing operation.

Working fluid flows to and from the head end of the motor 20 through piping "it. Working fluid flows to and from the crank end of the cylinders of motors I9 and 2% through piping H and 12 respectively. A valve element for controlling the ilow of working fluid, preferably compressed air, is located in the housing of a cycle control valve 15.

The supply of air for. operating the. motors L 3, and 26 comes to the cycle control valve 15, through,

opposite ends of the housing of the. cycle control valve '15 through piping 83 and 84.

By regulating the delivery pressure at which air is supplied to the cycle control valve. '15 from the pressure reducing valve 18, the speed and pressure of the motors I9 and 20 can be adjusted to govern the striking force of the cam wheel M in operating the punches for the second stage of the pointing operation. It isthis second stage that stalls the cam wheel. A heavy wall tube of maximum diameter for. which the apparatus is intended may require the full line pressure of 89 lbs. per square inch, but a x .020 tube can be pointed in the same apparatus with air pressure of only 15 lbs. per square inch.

The control air supplied to the master valve til is always kept at high pressure in order to give rigidity to the automatic stop and to avoid changing the timing of the cycle of the pointing machine.

Figure 7 shows the construction of the cycle control valve l5. The piping 84 which connects the right-hand end of the cycle'control valve with the master valve 8t is unobstructed and permits rapid flow of air. The piping 83 which connects the other end of the cycle control valve with the master valve 8! is obstructed by a disc 8% in which there is an orifice 8'! for permitting a reduced flow of air to the left-hand end of the cycle control valve 15. The disc 85 can be replaced with another disc having a smaller or larger orifice Bl if it becomes desirable to change the timing of the cycle of the machine. A needle valve can be used in place of the disc 86.

Within the-housing of the cycle control valve it there is a valve element $9 of the piston type with several sections of reduced diameter for controlling the flow of air to the various ports in the wall of the valve housing. There are ports at and 92 which communicate with the piping i2 and it respectively, and there is a center port St at the top of the valve housing through which air from the motor is exhausted to the atmosphere.

Air supplied to the cycle control valve 75 by the piping ll enters the cycle control valve housing through the inlet port which is ahead of the plane of section of Figure '7 but indicated by dot and dash lines. In the left-hand end of the housing of the control valve '55 there is a spring at that urges the valve element 89 toward the right.

When the master valve 8! is operated to supply air to the cycle control valve 75, air flows through the piping 84 faster than it flows through the piping 83 and builds up sufficient pressure behind the right-hand end of the valve element 39 to move this valve element to the left against the pressure of the spring 9i; and puts the valve port 9| in communication with the ex haust port 9 3, and an inlet port 95 in communication with the port 92 through which air fiows to both motors l9 and 20. With the valve element S9 at the left-hand end of its housing,

therefore, the' motor l9 and 20 operate the apparatus through its working stroke.

When the valve element 89 is moved back to the. position shown in Figure 7, air from the inlet 95 flows through the port 9| to the piping I2.

This supply of air causes the piston rod II of motor 20 to move downward. Such motion resets the machine to initial. or starting position. The valve element 89 in Figure 7 i in position to permit exhaust air from the piping ID to flow through the port 92 and out through the exhaust port 94.

The-motor I9 is only single acting and does not work during the. return movement of the apparatus.

In the. head-end; of the cylinder of motor I9, there is a port 96 through which that end of the cylinder is in communication with the atmosphere at all, times. Much less work is required forthe return stroke of the apparatus than for the; working stroke and the power of one motor i suflicient.

It. is desirable that the return stroke be made slowly enough so that the operator will have time to remove the tube before the first set of punches are operated through an idling stroke by the returning cam, sections. No production time is lost by this slow return stroke because the operator mustbe given time to remove one tube from themachine, place the pointed tube on a conveyer or otherwise dispose of it, and then reach for a new, tube and insertthe new tube into the machine.

The working stroke of the machine requires approximately one second, and experience has shown that a period of five seconds is satisfactory for the return stroke. These figures are given as illustrative only, and the. machine can be made to operate with different timing.

Figure 1 shows a disc 93' for obstructing the how of air to the crank-end of the cylinder of motor 28. There is an orifice in this disc just large enough to permit the motor 20 to make its return stroke in five seconds, or such other time as is selected for the return stroke. In order to prevent the disc Eli-from obstructing the exhaust air from motor 26 during the powerstroke, a bypass 89 is provided around the disc 93. A check valve I prevents air from flowing into the motor 2a. through the by-pass 99.

After the valve element 89- (Figure '7) has been pushed to the left, against the pressure of the spring 96 by the initial flow of air through the piping 84, air will continue to bleed through the orifice 81 and build up the pressure behind the left-hand end of the valve element 89 until the air pressure difference at opposite ends of the valve is sufficiently reduced for the spring 96 to push the valve element 8i! back to the righthand end of the housing. This time interval between the movement of the valve element 89 to the right, and its subsequent return, is long enough to permit the apparatus to make its working stroke.

Figure 10 shows the construction of the master valve 8!. This valve includes a housing 154 secured to the front of the ram guide 22'. Within the housing I94 there is a piston I85 that has a conical end which extends into the path of the punches 32 and 33. The piston 35 is connected to one end of a valve element IQ'I that extends forward and through a plug I68 that forms the front wall of the housing I04.-

A spring III). urges the piston IE toward the right. There is a handle I'II'attached to the 8 left-hand end of the valve element l0! by a screw H2 and this handle contacts with the outside face of the plug I08 and limits the movement of the piston I35 to the right under influence of the spring Ill]. The handle III is used to pull the valve element Hi1 and piston I05 to the left, against the pressure of the spring Ill], When operating the master valve by hand. In the ordinary operation of the machine, however, the piston I65 is moved to the left automatically, first by the insertion of a tube and second by the punches 32 when they move inward and strike against the conical face at the endof the piston- This conical face acts as a cam surface registers with an inlet port that opens through the valve housing and communicates with the compressed air supply line 86. The annular recess II l has a number of ports Hi5 opening through the wall of the bore in which the valve element I07 slides. Within the valve element Iill there is a hollow chamber I l I. This chamber i ll communicates with the interior of the housing I04, behind the piston IE5, through ports H8. The

chamber ill has other ports H9 that open intoan annular groove I20 in the outside surface of the valve element IIJ'I.

When the valve element Iill is in its normal osition, as illustrated in Figure 10, no air can flow from the ports H5 into the interior of the valve housing I0 2. When a tube 39 is inserted into the machine, the operator pushes the tube forward until it strikes the piston I05.

After the tube 39 strikes the piston I05, the operator continues to push the tube forward until the piston Illfi and the valve element Ifll'have moved back far enough to bring the annular groove I20 into register with the ports H5. When the valve element I0? reaches this position, air from the supply line 81] flows through the ports H5 and H9 into the chamber II'I Within the valve element and out through the ports IIB into the space behind the piston I65. This air pressure prevents the piston I05 from moving backany further unless the piston i subjected to considerably more force than that exerted by the operator pushing the tube into the machine.

The compressed air supplied to the interior of the valve housing liirl behind the piston I85 flows through an outlet at the bottom of the housing and into the piping which leads to the cycle control valve 75. This supply of air operates the cycle control valve, as explained in connection with Figure '7, and causes the motors to operate the machine and move the punches 32 inward against the tube 39. Inward movement of the punches 32 brings the end portions of the punches into contact with the conical surface of the piston IE5 and pushes the piston further to the left and entirely out of the path of the dies 32. The annular groove I 2&3 is made suificiently wide so that this additional movement of the piston I05 and valve element Iill does not move the annular groove I26 beyond the ports H5. When the punches 32 return to theiroriginal starting position, the spring Ilfl-moves the piston I05 back against the end of the partially-pointed tube, but the piston is again pushed back, without affecting the compressed airsupply to the motors,

bythe second set of punches 33.

One important advantage of the piston lildas a stop for. the: tube is that the end of the tube is located in a position back from the sides of thepunches and there is, therefore, no enlargement or flare at the tubepoint such as would occur if the tube extended to the ends of the punches. I

The referred embodiment of this invention has been described, but changes and modifications can be made and some'features of the inof atube into the machine for moving the control valve in one direction, and timing apparatus for causing the control valve to move in the oppo'site direction.

2 A tube-pointing machine including a'die with unches for coliapsing the walls of a tube,

mechanism for moving the punches against the tube, gas-operated motor means for actuating said mechanism,'a cycle control valve for supplying working fluid to the motor means and for controlling the direction of movement-f the motor meansmaster valve means for supplying compressed gas to the cycle control valve to operate said cycle control valve, a compressed gas conduit leading to the master valve means, a branch conduit for supplying compressed 'gas to the motor means through the cycle control valve, and a pressure regulator in the branch conduit for regulating the speed and power of the motor means.

3. Apparatus for pointing tubes of various diameters, said apparatus comprising a centering chuck, a holder with detachable fastening means for gripping a bushing of a size to fit a particular diameter of tube, jaws in the centering chuck for gripping the tube, cam mechanism for moving the jaws, an operating arm for the cam mechanism, face plates comprising a frame with an opening through which an end of the tube extends, fastenings connecting the centering chuck to the outside of the frame in line with said opening, ram guides connected to the inside of the frame and extending radially from the axis of the tube at angularly spaced regions around the outside of the tube, rams slidable in the guides, a punch carried by each ram at its inner end, cam followers on the rams, a flywheel within the frame and surrounding a portion of each of the rams including said cam followers, gear teeth around the periphery of the flywheel, cam surfaces on the inside surface of the flywheel for thrusting the cam followers and rains inward to move the punches against the tube, racks in mesh with the teeth of the flywheel, cylinder and piston motors for moving the racks to rotate the flywheel, a friction connection between the flywheel and the operating arm of the clutch jaw cam mechanism for moving said arm to operate the clutch jaws in response to the initial movement of the flywheel in either direction, a stop against which the end of the tube abuts when pushed through the jaw clutch and the lobes'on opposite sides of the points of iritime the frame, valve means operated by displacement of the'stop for supplying working fluid tome motors, and means for reversing the position of the'valve means after a predetermined lapse of time. Y Y

4, The method of pointing a tube in preparationfor a drawing operation, which method comprises applyingpre'ssure to the sides of a tube at regions spaced angularly around the circumference of the tube, and by suchpressure deforming the wall ofthe tube with inwardly extending bends that'jare adjacent to one another near the center of the tube and that are separated from oneanother circumferentially by lobes of the'tube' wall," and then indenting the lobes by applyirig pressure to them at points intermediate said regions and with sufficient force to make permanently deformed inwardly extendingbends at themid portions of the lobes, and simultaneously applying pressure to all of dentation with sufiicie'nt force to bring the sides of all of the bends substantially into contact with their next adjacent" bends to obtain a point of minimum cross section.

5. In the pointing of tubes for drawing, the

improvementthat comprises collapsing the tube togetherinto a substantially solid point. 1 6. The tube. pointing process comprising collapsing the end -0f! a tube to form a clover leaf section, and then reducing the section-by indenting the middle portions of the lobes and crushing the. lobes until their sides come into contact with one another, and applying pressure against the tube wall of both sides of the indentation and until the indented portion of the lobe is forced into contact with the confrontin inside surface of the lobe.

'7. The method of making a substantially solid point of generally square cross section on an end of a round tube preparatory to a drawing operation, which method comprises applying force to the outside of the tube at four spaced locations and by such force deforming the tube wall to a clover leaf cross section with inwardly extending bends that substantially touch one another near the center of the tube and that are circumferentially separated by lobes of the tube Wall, then applying force simultaneously to each of the lobes, first at the mid point of each lobe of the clover leaf to indent the lobe into a shallow bend and thereafter to the portions of the tube wall on both sides of the indentation until the metal is collapsed far enough to bring the outside walls of adjacent lobes into contact with one another and to bring the walls of the indentations into contact with the inside walls of the lobes.

8. Tube pointing apparatus comprising a device into which a tube end is inserted, pointed punches at spaced regions around the tube, mechanism for moving the punches against the tube and through a stroke that deforms the side walls into deep bends in the first stage of the pointing operation, other punches pointed at regions intermediate the first punches, said other punches including points that indent the portions of the tube wall between the bends into other bends of less depth than the bends made by the first punches, and said other punches also having surfaces that apply pressure on both sides of the indentations in directions to collapse the portions of the tube between the bendsand bring the sides of the adjacent bendstogether, and mechanism for moving said. other punches into contact with the tube. i

9. A tube pointing machine including two sets of punches, one set comprising angularly spaced devices with pointed ends for deforming the-tube wall into inwardly extending hendsicircumferentially spaced by lobes of the tube wall between them, and the other set comprising devices angularly spaced from one another and located substantially midway between the bunches of .the first section, each .of the devices having a point that imparts a reverse bendto thelobe beneath it and each of said devices having surfaces that contact with the surfaces of the lobe on both sides of the point that imparts the reverse ,bend, mechanism for moving the punch devices of the second set through a strolge that collapses the lobes and brings the confronting inside surfaces of a ja e e d nto b tantial c n ac with one. an he u e. n n ap a a us omp isin a e of punches movable inward against a tube at spaced points around the circumference of the tube, mechanism for moving the punches through a stroke sufiicient to deform deep bends in the tube wall separated by lobes, a second set of punches angularly spaced'from one another and located substantially 'midway between the punches of the first'set, each of the punches of the second set including a point that indents a bend in the lobe beneath it and including surfaces that contact with the metal 'on both sides of the lobe for collapsing said lobe 'so that the sides of adjacent lobes are forced together, mechanism for operating the second set of punches 12 including a flywheel and cam wheels that thrust the punches inward against the tube, the throw of said cam wheels being so correlated with the cross section and wall thickness of the tube that the sides of the bends made by the first set of punches are pressed together and the portions of the lobes indented by the second set of punches are pressed into contact with the inside surfaces of the lobes before the punches of the second set have moved through a stroke corresponding to the full throw of the cam wheels, and the apparatus is thus stalled by the resistance encountered by the second set of punches.

PAUL MUELLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 434,431 Dayton Aug. 19, 1890 439,951 Hendey Nov. 4, 1890 440,304 Collins Nov. 11, 1890 569,431 Sergeant Oct. 13, 1896 810,241 Wikstrom Jan. 16, 1906 952,298 Berg Mar. 15, 1910 1,031,000 Higgin July 2, 1912 1,070,379 Summey Aug. 12, 1913 1,157,852 Diekmann Oct. 26, 1915 1,480,077 Johnson Jan. 8, 1924 1,493,515 Berthold May 13, 1924 1,580,949 Berg Apr. 13, 1926 1,777,728 Kumpf Oct. 7, 1930 1,819,376. Muller Aug. 18, 1931 1,979,430 Wright Nov. 6, 1934 1,983,074 Durell Nov. 6, 1934 1,994,725 Offutt Mar. 19, 1935 2,055,771 McLaughlin Sept. 29, 1936 FOREIGN PATENTS Number Country Date 4,362 Great Britain of 1908

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