US1913760A

US1913760A - Machine for making well screens from metallic tubes

Info

Publication number: US1913760A
Application number: US397878A
Authority: US
Inventors: Edward E Johnson
Original assignee: EDWARD E JOHNSON Inc
Current assignee: EDWARD E JOHNSON Inc
Priority date: 1929-10-07
Filing date: 1929-10-07
Publication date: 1933-06-13
Anticipated expiration: 1950-06-13

Description

June 13,1933. E. E. JOHNSON 1,913,760

MACHINE FOR MAKING WELL SCREENS FhOM METALLIC TUBES Filed Oct. '7, 1929 6 Sheets-Sheet 1 Inventor: EEJZa/msen. By M l fl ii'orrzeys .11. WP at J J NW I v r II- E g l mm m ww W m [I on June 13, 1933. E. E. JOHNSON MACHINE FOR MAKING WELL SCREENS FROM METALLIC TUBES Filed Oct. '7, 1929 6 Sheets-Sheet 2 y M 1T s wk 9 v a m 2 r M o 1T T NQ- 0N. OW. IV; I mun JwNN vmT I, 1 92 NN I I i I l I I I I l I I I I l I l I l l l l. LPHHHHIH IIHI IH m mm m I. \I o I I m I .0 ou-\ wr r: 9 3w Al m I June 13, 1933. E.AE. JOHNSON MACHINE FOR MAKING WELL SCREENS FROM METALLIC TUBES Filed OQt. 7', 1929 -e Sheets-Sheet 5 /36 In ven for:

EB Jb/znson, 9 w M {tier/legs June 13, 1933. E. E. JOHNSON MACHINE FOR MAKING WELL SCREENS FROM METALLIC TUBES 1 Filed Oct. 7, 1929 S-Sheets-Sheet 4 In verz for. EL? Jbhnson. M1 N/ June 13, 1933. E, JOHNSON 1,913,760

MACHINE FOR MAKING WELL SCREENS FROM METALLIC TUBES Filed Oct. '7, 1929 6 Sheets-Sheet 5 Inventor: =EZTJb/mson.

ti'ornegs.

I June 13, "1933. E. E. JOHNSON MACHINE FOR MAKING WELL SCREENS FROM METALLIC TUBES Filed Opt. 7, 1929 s Sheets-Sheet 6 lh'i/en for. .E. E. (75hr: son By W Patented June 13, 1933 'fiTATES EDWARD E. JOHNSON, OF ST. PAUL, MINNESOTA, ASSIGNOR .TO EDWARD E. JOHNSON,

' INCORPORATED, OF ST. PAUL, MINNESOTA, A CORPORATION MAGHINEFOR MAKING WELL SCREENS FROM METALLIC TUBES Application filed. October 7, 1929. Serial No. 397,878.

I My invention relates to machines for making well screens from metallic tubes. An. obect of the invention is to provide a machme which will operate upon a cylindrical metalall times between the tube and the tap al-.

though the latteris collapsed at intervals to produce an interrupted thread of predetermined form. In the construction particularly shown and described herein, five slots separated by five uncut portions comprise one turn of the helix, and the uncut portions or posts extending longitudinally of the tube give it adequate strength. It is obvious that the number of slots per turn and hence the number of posts may be varied to suit tubes of different diameters by suitable changes of n gearing in the machine. In theembodiment here shown, the tube to be operated on is clamped to the head spindle of the machine and caused to move forward in a helical path by means of a stationary lead screw and past a tap whose ch asers are alternately advanced and retracted in a path transversely of the thread being cut, the timing arrangement being such that an interrupted thread of any determined pattern may be produced.

A particular object of the present invention is to improve upon the machine disclosed and claimed in my prior Patent No. 1,586,311 issued May 25, 1926, by providing a cutting device which taps an interrupted thread to the proper depth progressively so that the cutting eifort'is distributed fairly over all the cutting edges without causing undue strain on any, each tooth of each chaser acting successively in each groove cut. The simultaneone action of the chasers in the periphery of the tube serves to minimize the ill efiect of tuhes that are out of round.

The full objects and advantages of my invention will appear inconnection with the so detaileddescription thereof and the novel features of my inventive idea will be particularly pointed out in the claims. r

In the accompanying drawings which illustrate a practical form of construction in which my invention may be embodied, Fig. 1 is a top plan View partly in section of the rear portion of the machine. Fig. 2 is a top plan view of the front portion of the machine. Fig. 3 is a view in section on the line 3-3 of Fig. 1. Fig. 4 is a reduced front elevational view of the machine. Fig. 5 is aview in section on the line 5 5 of Fig. 2. Fig. 6 is a view in section on the line 66 of Fig. 5. Fig. 7 is an enlarged sectional View of the head of the machine with the saw and chasers out of engagement with the tube. Fig. 8 is a view corresponding to Fig. 7 with the saw and Chasers engaged with the tube. Fig. 9 is a cross sectional View of a tube having five slots per turn out therein; Fig. 10 is a view in section on the line 1010 of Fig. 7 Fig. 11 is a View in section on the line 1111 of Fig. 7. Fig. 12 is a view in section on the line 12-12 of Fig. 7. Fig. 13 is a plan view of the tap. Fig. 14 is a side elevational view of the rear 75 portion of the machine. Fig. 15 (Sheet 2) is a View in cross section of a tube having six slots per turn out therein.

Referring to the drawings, it will be understood from Fig. 1 that a tank 16 is provided near the rear of the machine, while from Fig. 2 it will be understood that a tank 18 is provided toward the front of the machine. These tanks in effect constitute suports for the operating mechanism of the machine. As will be understood from Fig. 4, the bottoms of the two tanks are secured to inverted U-bars 20 which rest upon the floor. The two tanks are connected by a horizontal angle beam 22 which extends out beyond the front tank 18 as shown in Fig. 2. A shelf 24 is secured to the rear tank 16 as best shown in Fig. 4 and serves as a support for an electric motor 26 which is driven from any suitable source of electricity. Secured to the end of the shaft 28 of this motor as shown in Fig. 1,

' there is a large pulley 30 which is connected by a belt 32 with a pulley 34 carried by a shaft 36 which, as will be understood from Fig. 4, extends into the tank 16 and drives a pump located therein. This pump which it is not necessary to refer to in detail is of ordinary construction and serves to pump coolin g agent from the tank 16 for a purpose which will be referred to later. Also secured to the motor shaft 28, as will be understood from Fig. 4, there is a small pulley 38 which is connected by a belt 40 with a pulley 42 secured to a shaft 44 mounted in bearings 46 carried by brackets 48 supported from the beam 22, the front portion of this shaft being mounted in a bearing 49 supported as shown in Fig. 5 by a bracket 51. As shown in Fig. 1, a small gear 50 secured to the rear end of the shaft 44 meshes with a large gear 52 secured to a shaft 54 mounted in bearings 56. Secured to the rear end of the shaft 54 adjacent the gear 52 there is a cam wheel 58 containing a cam groove 60 in which rides a roller 62 which, as shown in Fig. 14, is mounted on the upper end of a swinging arm 64, having a pivot 66 at its lower end. A second swinging arm 68, having a pivot 70 at its lower end, is connected to the arm 64 by

toggle links

72 and 74, having acommon pivot 76. The reduced upper end of a rod 78 extends through the common pivot 76. The lower end of the rod 78 is threaded through a hole formed in a support 80 carried by the bar 22. The rod 78, below its support 80, is provided with

lock nuts

82 and 84 and at its lower end is provided with a cross pin 86 by w iich it may be turned when the lock nuts are loosened. By turning the rod 78, the relative positions of the arms and 68 are adjusted. for a purpose which will appear later. When the rod 78 is screwed upwardly, the upper ends of the

arms

64 and 68 are separated further from each other and vice versa. The upper end of the arm 68 is twisted so as to provide a flat portion at right angles to the flat body portion of this arm, and said upper end is provided with a hole through which a rod 88 passessiidably and is provided at its rear end with adjustable nuts 90. The rod 88 is intermediately threaded to receive a nut 92, while a coiled spring 94 is interposed between the arm 68 and .no nut 92. Forward swinging movement of the arm 68 is imparted to the rod 88 through the spring 94 so that the r d is urged forwardly under resilient action. On the return movement of the arm 68, it engages the adjustable nuts and positively retracts the rod 88. This rod 88 passes through a stuffing box 96 and is weld-ed or otherwise secured to the rear end of a tubular rod 98 which is slidably mounted in a tube 100, having the stuiiin g box 96 secured to the rear end thereof.

The tube 100 is externally threaded as a lead screw for the greater portion of its length for a purpose which will presently appear, and it is fixedly secured near its rear end in a support 102 carried by the bar 22. A split nut device is adapted to engage the threads of the tubular lead screw 100. As

' extensions are adapted to be held in such engagement by a sleeve 118 slipped thereover. The open center member 112 is threaded upon the reduced end of a tubular member 120 slidable on the lead screw 100, the other end of the member 120 being provided with an outwardly extending annular flange 122. A changeable sleeve 124 is secured to the flange 122 by set screws 125 while the rear end of the tube T to be operated upon is secured to said sleeve by set screws 127. Upon opening the split nut, it is obvious that this member and the parts connected therewith may be slid to any desired position along the lead screw 100 according to the length of the tube T which is to be provided with grooves.

Two gears 126 and 128 of different size are secured to the tubular member 120, while the latter member is rotatable in a sleeve 130 formed at one side of a head casting 132 having a sleeve 134 at its other side slidably surrounding the shaft 54. The head casting 132 has an angular shoe 135 adapted to slide on the beam 22 as will be understood from Fig. 3. A plate 136 is secured to the sleeve 134 by a screw bolt 137 passing through a slot in the plate so that the latter may he slid along a keyway when the bolt 137 is loosened. The plate 136 carries a flange 138 whose distance from the sleeve 134 may be varied in the manner just stated. A gear 140, which is feathered on the shaft 34, is held back of the flange 138 so as to be out of mesh with the gear 128 when the machine is set in the manner shown in Fig. 1. At the same time, a gear 142 which is slightly larger than the gear 140 and is also feathered on the shaft 54 engages the front of the flange 138 so as to he in mesh with the gear 126 and thereby rotate the latter. In order to change the gear ratio, the gear 142 is moved out of mesh with the gear 126, while the gear 140 is moved into mesh with the gear 128. This may be readily done upon loosening the bolt 137, it being understood that the

gears

140 and 142 are mounted together on a sleeve 143. As will be seen from Figs. 7 and 8, the front end of the lead screw 100 is provided with internal threads to receive external threads formed on the reduced rear end 144 of a collapsible tap 146. The exterior of the tap is provided with a plurality of longitudinal grooves which receive ohasers 148 which at their rear ends are pivotally mounted on pins 150. In

the embodiment hereinshown, there are five of these chasers comprising the tapping mechanism, of the same pitchas the lead screw and equally spaced around the head. Each of the chasers 148 is provided with a plurality of cutting teeth or edges 152 which are progressively longer toward'the front so as to form internal grooves of the proper depth in the tube T by a progressive tapping action by each tooth of each chaser cutting succesively in each groove. The'tap when in action will of course follow its own lead, but when retracted as is necessary at intervals in cutting an interrupted thread, it is kept in proper position to enter the next succeeding cut by the lead screw 100. The inner surfaces of the chasers 148 are intermediately provided with inclined'surfaces 154, while their outer ends are provided with external inclined surfaces 156, these two sets ofinclined surfaces being for a purposewh'ich will now be explained.

The body of the tap 146 is chambered centrally to

diameters

159, 157 and 165 to receive and support the stem 158 and chaser cams 155 and 164 for the reciprocation as will presently be explained. The stem 158 extends forwardly through the chambers 159,

157 and 165 and is formed intermediately' with a male cam or cone 162 adapted to engage and support the inclined surfaces 154 of the chasers 148 on their outward or cutting stroke. The forward end of the stem 158 is threaded to'the member 164 which is adapted to slide in the chamber 165 and is maintained in its proper adjustment on the stem by a check nut 166 abutting the end thereof. The member 164 is provided with a female cam o-r cone 168 adapted to engage the surfaces 156 of the chasers 148 on their inward or idle stroke. It will be understood that when the stem 158 is moved forwardly by the action of thecam 58 into the position shown in Fig. 8, the male cone 162 will force the cutting teeth 152into engagement with the inner surface of the tube T, and when the cam retracts the stem 158 into the position shown in Fig. 7, the cutting teeth will be with drawn from engagement with the tube T. The cutting teeth do not ordinarily out quite through the tube, and, therefore, in order to complete the cut'so as to form the helical slots, a saw 170 is provided for operating upon the exterior of the tube coincident with the interior cuts. This saw is secured to shaft 172 in well-known manner, this shaft having secured thereto a pulley 174 driven by a belt 176 from a pulley 17 8 secured to the shaft 44. The shaft 172' is rotatably mounted in

bearings

180 and 182 carried by a-swinging frame 184. To support this frame, a bracket 186secured to the beam 22 is provided with spaced

lugs

188 and 190 which have threaded holes for receiving

screw bolts

192 and 194 having pointed ends received in recesses in I the frame 184 so that the latter may rock.

The bracket 186 carries outstanding ears 196 between which a curved lever 198is pivoted. The swinging frame 184 is adjustably attached to the outer end of the lever 198 by I a screw bolt200 which passes through the lever and threads into the frame. A screw bolt'202 which threads through this lever into engagement with the frame serves to in engagement with the lever 198, the saw 17 O V will be swung out of engagement with the tubeT, and when the low portion of the cam is in engagement with this lever, the saw willmove into engagement with the tube T so as to make a cut therein. .It will-be noted fromFig. 6, that the shaft 172 is somewhat inclined so that the saw 170. makes itscut with the same angle of inclination as the rooves which are formed by the cutting teeth of the tap. Byreferring to Figs. 7 and 8, it will be seen that the saw 170 makes its out shortly after the grooves made by the tap have been cut by the tapping action nearly through the tube T. V

The following device is provided to automatically'stop the feeding of the tube when it, has been provided with grooves extending nearly to its rear end. The shaft 44 is provided with a clutch 206 of ordinary construction normally held in clutched position and which, as shown in Fig. 1, is located between the pulley 42 and the gear 50 so that when the clutch is disengaged, rotation of the gear 50 is discontinued. The movable member of the clutch. is engaged by a shifter yoke 208 attached to the upper end ofan arm 210 whose lower end is pivoted between ears carried by the shelf 24 as shown in Fig. 4. Theyoke 208 is continued upwardly in the form of an arm 212 whose upper end is connected by a clutch throw-out rod 214 with the upper end of a lever 216 which is intermediately pivoted to a supporting member.

218 secured to the bracket 51. The lower arm of the lever 216 extends down into the path of the angularv shoe 135 which constitutes partof the casting 132 whichas previously indicated advances with the

split nut members

104 and 106 as the tube T is being fed forwardly. vWhen the rear end of the tube T has nearly reached the cutters, the. shoe 135 comes into engagement with the lower end of the lever 216 and forces the rod 214 rearwardly,'thereby disconnecting the clutch and stopping the feeding movement of the tube T. As shown in Figs. 2 and 6, the rod 214 is resiliently actuated by the lever 216 through the intervention of a coiled spring 220 interposed between the lever and a collar 222 secured to the rod 214, it being noted that the rod 214, after passing through a hole in the upper end of the lever 216, is provided with a collar 224. The tap 146 has been shown as provided with live chasers whereby the tube T is provided with live spiral grooves per turn in the form shown in F ig. 9. It is obvious from an inspection of Figs. 7 and 8 that the tap may be readily removed and replaced by another tap of different size and having a different number of chasers. Fig. 15 shows a larger tube T which has six spiral grooves per turn. It is obvious that for this purpose, a tap having six chasers would be provided. By referring to Fig. 1, it will be understood that the sleeve 124 may be readily replaced by another sleeve of such shape that the rear end of a tube of different size may be secured in place.

In order to support the tube T for its combined rotary and longitudinal movement, a number of guides 226 are secured to the beam 22 as shown in Fig. 2. These guides carry removable cylindrical members 228 in order that tubes of different sizes may be supported. As before .stated, the casting 132 carries a shoe 135 which rests slidably upon the beam 22. In order to additionally support this casting and the parts which move therewith, the casting is provided with a gib 230 as shown in Fig. 3 which engages with a guide bar 232 secured to the beam 22 in spaced relation thereto by studs 234. The pump in the tank 16, which was previously referred to as being driven by the shaft 36, is connected to a delivery pipe 236 provided with a shutoff valve 238. The upper end of the pipe 236 connects with the inner portion of the stuffing box 96 so that cooling agent forced by the pump is delivered into the interior of the threaded tube 100 through which it passes into the tap 146 which is provided with openings 240 through which the coolant passes to the cutting teeth and to the tube as it is being cut. The stream of coolant serves also to carry away the cuttings from the tapping operation. The cupshaped member 164 is also provided with openings 242 through which some of the coolant may escape. By referring to Fig. 2, it will be understood that the coolant, after having served its purpose, runs into the front tank 18. It is apparent that this tank may be provided with a screen to catch chips of metal so that they will be prevented from falling down into the tank. From a point near the upper end of the tank 18, a return pipe 244 leads back to the bank 16, this pipe being downwardly inclined as will be understood from Fig. 4 so that the coolant flows back by gravity.

The operation and advantages of my invention will be understood in connection with the foregoing description. With the machine set as shown in Fig. 1, rotation of the shaft 54 acting through the

meshed gears

126 and 142 causes rotation of the tubular member 120 and the sleeve 124 to which the tube T is secured. The tubular member 120 also carries the split nut device which is rotated thereby, and the rotation of this device by its engagement with the threaded tube 100 causes the tube T to be fed forwardly or longitudinally so that this tube is given a combined rotative and longitudinal movement. At the same time, the cam wheel 58 secured to the shaft 54 is caused to rotate and thereby reciprocate the rod 98 and the attached stem 158 which passes slidably through the tap 146. When the stem 158 moves forwardly, the cone 162 moves along the inclined surfaces 154 of the chasers 148 and causes the cutting teeth 152 to bite into the interior surface of the rotating forwardly moving tube T as shown in Fig. 8 with the result that the teeth 152 will cut helically extending grooves or slots. Since the cone 162 is moved forwardly under the resilient action of the spring 94, the chasers are caused to engage the tube T without shock. Furthermore, if the tube T is not truly cylindrical, the simultaneous action of the chasers serves to minimize the effect of such eccentricity and produce satisfactory results in operation. When the stem 158 moves backwardly, the cone 162 is retracted and the cup member 168 engages the inclined surfaces 156 on the chasers 154 and removes the cutting teeth from engagement with the tube as shown in Fig. 7. As previously indicated, the extent of this retracted movement may be regulated by turning the rod 78 to vary the inclination of the

links

72 and 74 and hence the position of the arm 68 relative to the arm 64. It will also be understood that the nuts 90 and 92 are to be adjusted so as to secure proper action of the chasers. It is apparent from Fig. 14 that the high left hand portion of the cam 58 extends for a much greater distance peripherally than does the high right hand portion thereof, and hence the period of engagement of the cutting teeth with the tube T is much greater than their period of disengagement therefrom. Since the

gears

142 and 126 have a ratio of one to five, there will be five slots per turn of the tube when these gears are in mesh. The

gears

140 and 12 8 have a ratio of one to six, and, hence, when these gears are brought into mesh. there will be six slots per turn of the tube, it being understood that a tap having six chasers is then substituted for the one having five.

It is apparent from Fig. 8, that the cutting action of the teeth 152 is in the nature of a tapping action since the out first made by ashort tooth is followed by a deeper cut made by a longer tooth and so on progressively until the longest tooth of each chaser has operated in the groove which is being cut. It is to be noted that the sets of cutting edges on I with relation to the tube.

, 3-. A machine for making well screens from metallic tubes comprising atapping cutter the respective chasers follow each other during the operation of the machine in such manner as to produce a progressively increasing depth of cut by the helical forward travel of the tube and the'overlapping relation of the sets of cutting edges. The cuttingedges are not made to cut entirely through the wall of the tube, and the saw 170 operates to complete the slot by cutting from the outside of the tube into the slots or grooves which have just beenformed by the tapping teeth 152 so that spirally extending slots are produced piercing entirely through the wall of the tube. The effect of the saw is to produceslots having a uniform width on the exterior of the tube regardless of variations in the thickness of the wall ofthe tube. By referring to Fig. 5, it will be understood that the position of the saw may be readily adjusted to suit the size of the tube which is to be cut. Change of the gear ratio betweenthe shaft'54 and the tubular member 120 rotated thereby does not affect the length of cut made by the saw, and it will be understood that the cam 204 which swings the saw will be set so that the' saw enters at the beginning of an internal groove and leaves at the end of this groove. I In order to change the length of cut made by the saw, it is only necessary torun the saw to greater or less depth of cut. The pump supplies a constant stream of coolant to the cutting teeth and saw so that overheating of these parts is prevented. The coolant-may consist of any liquid suitable for this purpose which can be circulated by the pump. v v

,I' claim: r 1. A machine for making well screens from metallic tubes comprisingatapping cutter,

means for giving the tube and said cutter a relative combined rotative andlongitudinal movement, means for causing said cutter; and

vtube to alternately approach and recede with relation to each other to produce asuccession of helically extending cuts in the wall of the tube, a saw, and mechanism for causing said saw to operate in said cuts. c 2. 'A machine for making well screens from metallic tubes comprising a tapping-cutter, means for giving the tube a combined rotative and longitudinal movement, means for causing said cutter to alternately advance and recede with relation to said tube topro duce a succession of helically-extending cuts in the wall of the tube,'a saw positioned to operate in said cuts, and means for causing said sawto alternatelyadvance and recede positioned to I operate upon the inside of the tube, means for giving the tube a combined rotative and longitudinal movement,

means for causing said cutter to alternately advance and recede with relationto said tube to produce a succession of helically'extendi'ng the tube, and means for causing said saw to alternately advance and recede with relation to the tube. V

' 4. A machine for making well screens from metallic tubes comprising a driven shaft, a stationary externally threaded cylindrical member, a nut member adapted to engage said cylindrical member, means for holding the tube for movement with said nut member, changeable speed gearing between said driven shaft and nut member whereby they tube may be given. a combined rotative and longitudi nal movement at different speeds, a tapping cutter, and means for causing said cutter to alternately approach and recede with relation to the tube to, produce a succession of helically extending separated cuts in the wall thereof. 1

5. A machine for making well screens from metallic tubes comprising a driven shaft, a stationary leadscrew, a nut adapted toengage said lead screw, means for holdingthe tube for movement with saidnut, gearing between said driven shaft and said nut whereby the tube may be given a combined rotative and longitudinal movement, a tapping cutter, and means for'causing said cutter to 'alternately approach and recede with relation to the tube to produce a succession of helically extending separated cuts in the wall thereof. 3'

Y 6. A machine for making well'screens from metallic tubes comprising a driven shaft, a stationary externally threaded cylindrical member, a nutmember adapted to engage said cylindrical member, means for holding the tube for movement with said nut member, a plurality of different sized gears any one of which is adapted to rotate said nut member to give the tube a combined rotative and longitudinal movement, a plurality of different sized gears feathered on said drivenshaft and held for longitudinal movement with said nut member, means whereby any one of said last mentioned gears maybe made to mesh with the corresponding one of said. first mentioned gears to change the gear-ratiO acutting device, and means for causing said cutting device to alternately approach and recede with relation to the tube means for rotating-said nut member from said shaft whereby'the tube is given a combined rotative and longitudinal movement, a cutting device, and means for causing said cutting device to alternately approach and recede with relation to the tube to produce a succession of helically extending cuts in the wall thereof.

8. A machine for making Well screens from metallic tubes comprising a driven shaft, operating connections between said shaft and the tube for giving the latter a combined rotative and longitudinal movement, a tapping cutter, means for causing said cutter to alternately approach and recede with relation to the tube to produce a succession of helically extending cuts in the wall thereof,

a clutch on said driven shaft normally in clutched pos1t1on,and means for automatically disengaging said clutch when the cutting of the tube is completed.

9. A machine for making well screens from metallic tubes comprising a driven shaft, a stationary externally threaded cylindrical member, a nut member adapted to engage said cylindrical. member, means for holding the tube for movement with said nut member, means for rotating said nut member from said shaft whereby the tube is given a combined rotative and longitudinal movement, a cutting device, means for causing said cutting device to alternately approach and recede with relation to said tube to produce a succession of helically extending cuts in the wall thereof, a slide mounted to move longitudinally with said nut member, a clutch on said driven shaft normally in clutched posi tion, and a clutch throw-out device operated by said slide when the cutting of the tube is completed.

10. A machine for making well screens from metallic tubes comprising a front tank, a rear tank in spaced relation thereto, a beam supported by said tanks, means supported by said beam for giving the tube a combined rotative and longitudinal movement, a cutting device located above said front tank, means for causing said cutting device to alternately advance and recede with relation to the tube to produce a succession of helically extending cuts in the wall of the tube, a device for pumping cooling agent from said rear tank for delivery to said cutting device, and a gravity connection between said front and rear tanks for carrying back to said rear tank the cooling agent which has passed said cutting device.

11. A machine for making well screens from metallic tubes comprising means for giving the tube a combined rotative and longitudinal movement, a cam, a swinging arm engaged by said cam for rocking movement thereby, a second swinging arm, an adjustable connection between said arms, a rod attached to said second arm for reciprocation thereby, and a cutting device operated by said rod for causing the cutting device to alternately approach and recede with relation to the tube to produce a series of helically extending cuts in the wall thereof.

12. A machine for making well screens from metallic tubes comprising means for giving the tube a combined rotative and longitudinal movement, a cam, a swinging arm engaged by said cam for rocking movement thereby, a second swinging arm, an adjustable connection between said arms, a rod having one of its ends passing slidably through the free end of said second arm, an enlargement on said end, a spring resiliently holding said second arm in engagement with said enlargement, a cutter head associated with the other end of said rod, and a cutting device carried by said cutter head and caused by reciprocation of said rod to alternately approach and recede with relation to the tube to produce a succession of helically extending cuts in the wall thereof.

13. A machine for making well screens from metallic tubes comprising means for giving the tube a combined rotative and longitudinal movement, a cutter head, a plurality of tapping cutter arms pivotally mounted at one end around said head, said arms having inner and outer inclined surfaces, a reciprocating rod extending slidably through said cutter head, a cone member carried by said rod and which during forward movement thereof moves on said inner surfaces to cause the cutters to engage the tube, and a cuplik-e member carried by 7 said rod having an interior inclinedsurface which during reverse movement of said rod engages said outer inclined surfaces to retract said cutters.

14. In a machine for producing interrupted threads in metallic tubes, a collapsible tapping cutter, means for giving the tube and said tapping cutter a relative rotative movement, and means for alternately collapsing and expanding said tapping cutter to produce a succession of helical cuts in the wall of the tube.

15. In a machine for producing interrupted threads in metallic tubes, a collapsible tapping cutter, means for giving the tube and said tapping cutter a relative combined rotative and longitudinal movement, and

means for alternately collapsing and expanding said tapping cutter to produce a succession of helical cuts in the wall of the tube.

16. In a machine for producing interrupt ed threads in metallic tubes, a collapsible tapping cutter, means for giving the tube a combined rotative and longitudinal movement, and means for alternately collapsing and expanding said tapping cutter to produce a succession of helical cuts in the wall of the tube.

17. In a machine for producing interrupted threads in metallic tubes, a collapsible 1 tapping cutter, means for giving the tubes a combined rotative and longitudinal movement, and a cam for causing said tapping cutter to be alternately collapsed and expanded to produce a succession of helical cuts in the wall of the tube, said cam being so shaped that a period of engagement of said tapping cutter with the tube is greater than its period of disengagement therefrom.

-18. In a machine for producing interrupted threads in metallic tubes, a collapsible tap having a plurality of chasers each with a plu- V rality of thread-cutting edges, means for giving the tube and said tap a relative rotative movement, and means for alternately collapsing and expanding said tap for causing said edges to produce a succession of helical cuts in the wall of the tube.

19. In a machine for producing interrupted threads in metallic tubes, a fixed lead screw adapted to beenveloped by the tube, a

travelling head engaging said lead screw for I movement thereby and carrying the tube, a collapsible tapping cutter carried by the free end of said lead screw, and means for alternately collapsing and expanding said tapping cutter to produce a succession of helical cuts in the wall of the tube.

In testimony whereof I hereuntoaflix my 1 signature.

EDWARD E. JOHNSON.