US2419870A

US2419870A - Metal drawing apparatus

Info

Publication number: US2419870A
Application number: US341697A
Authority: US
Inventors: Jr Raynal W Andrews; Arthur T Deily
Original assignee: Aluminum Company of America
Current assignee: Howmet Aerospace Inc
Priority date: 1939-08-03
Filing date: 1940-06-21
Publication date: 1947-04-29
Anticipated expiration: 1964-04-29

Description

April 29, 1947.

R. W. ANDREWS, JR, ET AL METAL DRAWING APPARATUS Original Filed Aug. 3, 1939 5 Sheets-Sheet l M 5 R w m V m Ray/ml M Andrews, J7.-

QW'EORNEY Ap i 29, 1947. R. w. ANDREWS, JR., ETAL 2,419,870

METAL DRAWING APPARATUS 3 Sheets-Sheet 2 Original Filed Aug. 3, 1939 III all! I! III lll mvu-rons MAndmmgi at Arthur 731781151.

ATTORNEY April 1947. R. ANDREWS, JR, ET AL 2,419,870

METAL DRAWING APPARATUS Original Filed Aug. 5, 1959 3 Sheets-Sheet 3 INVENTORS Raynai w. AndrewgJr. amy Ar-Mur 71' Daily ATTORNEY Patented Apr. 29, 1947 2,419,870 METAL DRAWING APPARATUS Raynal W. Andrews, Jr., New Kensin'gton, and Arthur T. Deily, Pittsburgh, Pa., assignors to Aluminum Company of America, Pittsburgh, -Pa., a corporation of Pennsylvania Original application August 3, 1939, Serial No.

288,163, now Patent No. 2,331,953, dated October 19, 1943. Divided and this application June 21, 1940, Serial No. 341,697

This application is a division of our application Serial No. 288,163, filed August 3, 1939, now Patent No. 2,331,953, issued Oct. 19, 1943, for improvements in Metal working apparatus, and

relates particularly to control of the drivingv means and to means for attaching a carriage thereto in a metal drawing apparatus. Our application, Serial No. 341,696, filed June 21, 1940, for improvements in Carriage for metal drawing apparatus is also a division of our above-mentioned application.

This invention relates to apparatus for working metal shapes, and more particularly to draw benches for drawing tubular shapes, rods and the like through a die.

The usual draw bench for tube drawing comprises a supporting frame or frames upon which are mounted a die, a mandrel and bulb, a draw chain or the like, and a carriage having jaws for gripping the work after it has been passed over the mandrel and bulb and inserted through the die. The carriage must be moved to draw the work through the die, and for this motion generally engages with, and receives its drawing force from, a draw chain or similar device.

It has been customary for draw chains to be driven continuously and at constant speeds; and it has further been customary for a carriage to be engaged with the chain while it is in motion at such constant speed, thus accelerating the work almost instantaneously.

The jerking and shock of such rapid acceleration of the work frequently causes breakage in the work and results in waste of material and loss of useful production time. A further cause of breakage, waste, and poor work has been the fact that the gripping jaws of the drawing carriages of prior apparatus have not been designed to engage the work at points other than along the axis of the draw, and work-pieces pointed for engagement by the jaws often have pointed ends which are bent ofi center or otherwise disposed out of alignment with their normal axes;

Also informer practices, production has been limited by the time required for the return of the drawing carriage to the die head and by the time required for passing new work over a mandrel rod and bulb. I

The general object of this invention is to improve the drawing devices of the prior artto produce draw benches or similar apparatus in which the drawing operation may be performed with less loss of useful production time and less wastage of material than is now usually obtained. Specifically, this general object is obtained, in

i Claim. (01. 205-3) z whole or in part, by the realization, singly or combination, of the following more specific obects: The provision in a draw bench 011 a variable speed draw chain which may be stopped or slowed perceptibly, as the jaws clamp the work, for engagement therewith of the hook supported by the drawing carriage. The provision of a power source actuating such draw chain which is capable of quickly and evenly bringing the work up to a relatively high drawing speed without undue shock. The provision of means for automatically K reducingv the speed of said draw chain and stopping the drawing carriage upon completion of a drawing operation. The provision of a draw chain assembly which will uniformly transmitdrawing energy from the power source to the workpiece with a minimum of variation in actual drawing speed. The provision in a drawing carriage of work-engaging Jaws adapted to engage such portions of the work-piece as may be located out of the axis of the draw, and of jaw-actuating means adapted to this purpose. The provision of a system or means capable of accelerating and decelerating the drawing carriage during its movement on return to the die head after the completion of a drawing cycle, and the provision of such a system or means capable of actuating said car riage without undue shock.

These and further objects and advantages of this invention, either singly or in combination, are for purposes of convenience illustrated with respect to a specific mechanism which embodies all of the specific features of the invention. It will be understood, however, that these features may be available for single use, or in any suitable combination, to improve the operation of draw benches or similar apparatus which do not include all of said features.

'In the drawings:

Fig. 1 is a partial plan view of the preferred form of a mechanism embodying the features of the invention, and showing two mandrel rods,

the die head, the drawing carriage, the draw engaging hook is in a lowered position, in its first engagement with the draw chain;

Fig. 4 is a fragmentary view, partly in section, of the jaw-actuating crank, Jaw-actuating levers, and associated parts, taken along the line IV-iV of Fig. 3, the crank and levers being rotated into vertical position for simplicity of illustration;

Fig. is a plan view of the drawing carriage shown in Fig. 3, and to the same enlarged scale, in which one-half is a section taken as indicated by the reference line V-V of Fig. 4.

Briefly, the apparatus as shown comprises a draw bench frame, a drawing head or carriage, a drawing die, and two work supporting mandrels. A hollow shape may be passed over one mandrel within a protecting shell or other guiding support by hand or by suitable mechanical loading mechanism (not shown); the mandrels may be'rotated to align one work-piece and mandrel with the die; the.point of the work-piece may be inserted through the die; and the mandrel and work-piece may be forced into registry with the die conjunctive with the beginning of the drawing action. The drawing carriage and its work gripping jaws may be actuated to clamp the point of the hollow-shaped work-piece, and may be moved along the draw bench by suitable engagement with a draw chain to draw the workpiece through the die. Upon completion of a draw, the work-piece may be released to aconvenient rack or removal apparatus (not shown).

Endless return means are provided for automatically traversing the drawing carriage back to the die head after completion of a drawing operation. Such endless return means are preferably operable independently of the drawing chain and preferably are adapted to control the position and rate of speed of the drawing carriage during its return movement.

As will appear more fully in the detailed description of the apparatus as shown, means have been provided throughout for automatic operation of the draw bench during at least one complete drawing cycle.

Die section The die section of the draw bench will now be described with special reference to Figs. 1 and 2 of the drawings. By the die section is meant that portion of the apparatus immediately adjacent, or associated with, the drawing die. A main piece. Bulbs II and i3 are secured to mandrel rods l0 and I2, respectively, by suitable threaded nuts l4, preferably tapered outwardly to facilitate passing of tubular and hollow-shaped stock thereover.

Means not necessarily forming part of this invention may be provided for placing a workpiece on the mandrel when it is in the position of mandrel l2. Means may be provided for rotatframe I is secured on foundation 2; and at one end of the main frame (to the left as viewed in Figs. 1 and 2) is mounted a removable die head 3, incorporating drawing die 4, die retaining block 5, and retaining pin 3. The die 4 is removably mounted to facilitate change or replacement of dies to take care of different sizes and shapes of material to be drawn. The die head 3 may be removed from the frame by engagement of acrane hook with an eye -bolt I. The die head may be suitably shimmed for alignment about the axis of draw in one or more planes, or a tilting die head, adjustable about either vertical or horizontal axes, can be employed if desired.

The work-piece, here a tube 8, is shown with its pointed end 3 inserted through die 4. As shown in the sectioned portion of Fig. 2, the drawing operation has not started, and, therefore, mandrel rod Ill and bulb ii are not shown in full registry with I I2 and bulb [3, are located above and behind mandrel rod Ill and bulb ll. Said second mandie 4. A second mandrel rod ing the mandrel rods to bring the mandrel rod and work-piece from the position of mandrel rod l2 to the lateral position of mandrel rod iii; and means may be provided for advancing a mandrel rod and its work-piece to the die to occupy the position of mandrel rod l0, bulb II, and tubular work-piece 8, as shown.

Means are provided for protecting and supporting a work-piece passed over a mandrel rod and bulb. These means preferably take the form of tubular shells 18 supported at convenient intervals along their length by mandrel supports 24 (one of which is shown to best advantage in Fig. 2) comprising bases 25 attached to foundation 2. Adjacent die head 3 suitable bellmouthed guide bushings l8 are mounted within end portions of shells IE to facilitate the entry of a hollow shape over a mandrel rod and within the protective and supporting shell. Looking bands 20', adapted to compress tubular shells I. on bushings l8, may be readily loosened for interchange of bushings of various size depending on the size of tube to be drawn, With respect to the mandrel rod, bulb, and hollow-shaped work-piece, each guide bushing is arranged to partially support the work-piece at a point adjacent the die head when the bulb is forced into registry with the die by means of the mandrel rod. Additional guide bushings 22 are located at suitable intervals within the shells l6 and provide further points of support for the work-piece. Tubular shells iii are designed to protect the work against scratching and dirt and, with bushings l8 and 22, to support work of considerable length. Where protection of the work from dirt is not a primary problem, the shells 13 may take the form of spaced sections or rings rather than continuous lengths of tubing as shown.

Drawing section Referring to the drawings, the drawing section of the draw bench is now described. This section of the bench is defined as that portion of the bench, including the associated apparatus, over which the stock is pulled or drawn 'from the die I. The drawing section comprises generally frame I, draw head 30, and tracks or rails 3i along which the carriage may move on carriage wheels 32. Gripping jaws 33 and 34 are located in draw head 30 and are adapted to engage the pointed end 9 of the tubular work-piece 3. Carriage hook 35 is adapted to engage endless draw chain 36. A pair of suitable return .chains or other endless driving means 31 and 23 are connected to carriage 30 on either. side thereof and adapted to return the carriage to die head 3 upon completion of a drawing operation.

Means are provided upon carriage Ill, here in the form of trip arm 39, for actuating a plurality of limit switches 40, ll, 42, 43. 44, and II, which are located along the main frame I, as shown. These limit switches are arranged to control acceleration and deceleration of drawing carriage 30 during its forward drawing and return movements, and further to control various other operations to be hereinafter described.

Draw chain 36 is centrally located within frame I and is supported over drive sprocket 46 and idler sprocket 41. Drive sprocket 46 is preferably driven by either one or both of two m otors (preferably hydraulic, but not shown) connected to a drive coupling 48 at the extreme forward end of the bench (to the right as viewed in Figs. 1 and 2), which drive coupling 48 is connected to the draw chain drive sprocket 46 through a drive shaft 49 held in frame I by bearings 50 and 5|. The draw chain may be lubricated by continuous immersion in a suitable oil reservoir located in the path of the under portion of the chain, but not here shown. The idler sprocket I1 is located adjacent the die end of frame I and is mounted on an idle shaft 52 journalled in adjustable bearings 53. These bearings may be moved longitudinally of the draw bench by means of nuts 54 on screw threaded rods 55, for adjustment of the draw chain tension or for removal of the draw chain.

The draw chain 36 has preferably a short pitch, that is, the links are made as short as possible so that variation in linear velocity of the chain will be kept at a minimum; and the drive motors for the drawing chain preferably have rigid speed control so as to produce as nearly constant drawing velocities as are feasible. By means of this preferred form of apparatus, the drawing speed may be varied from practically a stop up to normal speed, under no load up to heavy drawing load, with rapid and even acceleration, initiated by electrical control operable through limit switch 43.

Return chains

31 and 38 are fixed to carriage 30, through tie plates 56, and,are supported and located on either side of frame I, being engaged by drive sprockets 51 adjacent the die end of said frame and by idle sprockets 58 at the opposite end of said frame. Drive sprockets 51 are mounted on a common drive shaft 59, which carries belt pulley or sprocket 50, and is journalled in suitable bearings 6|. The drive shaft and sprockets are driven by electric motor 52 through drive belt or endless chain '53 and belt pulley or sprocket 60. The return chain idle sprockets 58 are located on common idle shaft 54 joumalled in adjustable bearings 55. Means for adjusting the tension of return chains and for permitting their ready removal are here provided in the form of threaded rods 55 and adjusting nuts 51 provided thereon.

Return chains

31 and 38 are recessed in chain guards 58 for protection of both chains cam 59 (Fig. 2) located adjacent the die head of the drawing section of the draw bench, or of stop cam .10 located at the other extremity of the draw'bench. At either cam the action of release lever 1| and its roller 12 is to lift hook 35 out of engagement with drawing chain 36, thereby bringing carriage to rest.

Cam 69 is provided for the purpose of releasin the carriage hook from the draw chain when the carriage jaws have failed to engage the workpiece or in case of breakage of the work-piece during forward travel of carriage 30. In either event, there is no drawing tension on thechaiu.

and operator. Suitable means may be provided for lubricating such chains where desirable. The electric motor 52 operating said return chains is preferably adapted to be used as an a electric brake upon the draw carriage 30 as it approaches the die head 3. In this way the movement of the carriage on its return to the die head is positively controlled, thus eliminating the If the carriage 30 has engaged work-piece 8 through the proper clamping engagement of jaws 33and 34 upon the work, the drawing tension exerted on draw chain 35 will lift the chain and the engaging carriage hook 35-sufliciently 'high to permit hook release lever II and roller 12 to clear the cam 69. Thus the normal drawing operation will continue until the work-piece is free of drawing die 4. At this point, drawing tension is immediately released and the draw chain tends to fall and disengage itself from the hook 35. Cam 10 functions as a safety device and hook adjusting mechanism in the event that hook 35 does not, at the end of the drawing operation and when drawing tension is released, release itself from the chain but falls therewith. In such case, the release .lever 1| and its cam follower 12 contact cam 10, with the result that the hook 35 is positively raised and disengaged from the chain 33, and reset in its raised posi- I tion, thus preventing the continuously traveling .chain 35 from dragging the draw head 30 off the end of the bench, or preventing other injury to the assembly.

Draw head With reference especially to Figs. 3 through 5, the draw head or carriage 30 will now be particularly described. In the carriage are the aforev work-piece at the die head 3. These jaws are so necessity for employing previously used shock absorbers or cushioning devices to stop the carriage at the die head. The two

return chains

31, 38 are preferably provided to insure align ment of the drawing carriage with the die head upon its approach thereto,'but a single chain or cable may be used with satisfactory results. The acceleration and deceleration of the drawing carriage 30 on its return travel may be accurately controlled through one or more of the aforementioned limit switches," as here shown by switches 40, II, and 42, which switches are actu-J 1 is arcuate in form (see Fig. 2) to conform with ated by the drawing carriage trip arm 39. I

Other elements of the drawing section of the arranged that one jaw may advance or adjust itself relative to the other, and relative to the work-piece to grip the pointed end 8 thereof and exert an axial drawing force thereon despite any irregular formation or non-axial alignment of said work-piece end. Further it may be noted that the jaws are actuated through a, linkage,v

which will be described hereinafter, by means of the forces exerted by the draw chain engaging hook 35.

The carriage or draw head 30 is provided with a transverse shaft 15 journalled in the frame thereof. Centrally on said shaft is keyed the olevised end (see Fig. 5) of carriage hook 35. Thishook has a link-engaging portion 16 which a link of the draw chain, the said arcuate portion 'draw bench which should be noted at this point being preferably adapted to engage somewhat chain 35 on the 7 more than 90 of are on any particular link. Also keyed to shaft 15, at one end thereof, and located outside the frame of carriage 38, is the hook release lever 1| and its cam contacting roller" 12. The keyed angular relationship of hook 35 and hook release lever H on through shaft 15 is such that when lever 1| is in its lower position, its roller 12 would engage cam 69 or stop cam 18, on approach thereto, and rise thereon, thereby raising hook 35.

Also keyed to shaft 15 between forked portions of the clevised end of hook 35 is a crank lever 11 extending in a generally vertical direction above top plate 18 of carriage 38, said hook 35 and crank lever 11 substantially forming a bell crank oscillatable with said shaft 15, in accordance with the forces imparted to the hook by means of the draw chain 36, or to the hook release lever 1| by means of the cams 69 or 18.

Disposed laterally and approximately centrally of carriage 38, above top plate 18, is pin 19 supported and retained in bearing blocks 88, 8|. oscillatable on pin 19 is a centrally disposed crank 82 which extends upwardly therefrom in a generally vertical direction. Adjustable link 83 connects the upper extremities of crank 82 to crank lever 11, whereby crank lever 11, adjustable link 83, and crank arm 82 form, with the frame of the carriage, a quadric-crank linkage.

Preferably integrally formed with the lower portion of crank 82 is a projection forming a latch 84 adapted to be engaged by pawl 85, whereby the quadric-crank linkage actuated by hook 35 or release lever 1| may be latched with the hook in its raised position in a manner which will be more fully described hereinafter.

Also oscillatably mounted on pin 19, on either side of crank 82, are jaw-

actuating levers

86 and 81, which levers have portions extending in a I generally vertical direction above pin 18 in normally parallel relationship with crank arm 82, and jaw-actuatin portions extending below pin 18 to act as lever arms. Jaw-

actuating levers

86 and 81 are independently oscillatable On pin 18 and are inter-related in their action by a doubleacting spring 88 and associated parts. At the lower extremities of said jaw-actuating levers are

adjustable links

89 and 98 connecting to workengaging jaws 33 and 34, respectively. Said jaws are slidable on converging ways 9I (see Fig. The latterly described portion of the actuating linkage for each jaw may be referred to as a slider-crank linkage, said linkage comprising a jaw-actuating lever, an adjustable link, and a jaw slidable on a converging way.

To provide for convergence of the jaws, and for the angular movement of adjustable links 88. 98 with respect to levers 86, B1 and the jaws 33, 34, suitable ball-and socket connections 92 have been provided between each of said levers and each of said adjustable links and between each of said links .and each of said jaws.

Approximately central of the length of the crank 82 on either side, and in the directions of oscillation thereof, are recessed, concave bearing portions or seats 83. substantially semi-cylindrical in form. On the upper extremities of jawactuating levers 86, 81 on either side, and in the directions of oscillation thereof, are similar recessed, concave bearing portions 84, substantially semi-cylindrical in form and adapted to lateral alignment with the corresponding bearing portions 83 on crank 82. Crank 82, at the level of recessed bearing portions 93, has an aperture 85 extending therethrouzh in a direction substantially tangential to the arc of rotation thereof. Extending through aperture 95, in approximately the same plane as contains the quadriccrank linkage and normally perpendicular to crank 82, is adjustable tie-bolt 96 threaded at either end, to receive adjusting nuts 81. Mounted preferably on the forward end of the tie-bolt 96, in the direction of draw, is bearing member 98 engaging crank 82 and jaw-actuating levers 86. 81 in the aforedescribed bearing portions 83 and 84, respectively. The said bearing member 88, which is axially slidable on tie-bolt 86 and positionable thereon by means of nuts 91, extends laterally across crank 82 and across the jawactuating levers 86, 81, and is adapted to engage with either of said jaw-actuating levers or said crank independently, or at times with all of them simultaneously. For engaging the opposite bearing portion of crank 82, or the opposite bearing portions in jaw-

actuating levers

86, 81, is a second bearing member 98 similarly mounted on said tie-bolt 96. The two bearing members 88 and 99 are provided with semi-cylindrical or convex bearing surfaces adapted to engage in the aforesaid semi-cylindrical or concave bearing recesses of the crank and the levers.

The bearing member 98, slidable on tie-bolt 86, serves further as a spring seat for double-actin spring 88, which spring is mounted surrounding the said tie-bolt 86 on that portion of the tie-bolt which extends, to the left as viewed in Fig. 3, toward the jaw portion of the draw head 38. An opposing spring seat I 88 is located at the end of tie-bolt 86 and is slidable thereon, being adjustable for position by means of adjusting nuts 91.

Levers

86, 81 and crank 82 are cooperatively related by means of the aforementioned doubleacting spring, tie-bolt, spring seats, and bearing members. The two-fold purpose of the spring and associated elements is, briefly, (1) to tend to keep levers and crank in the same axial line so that they may function substantially as one split lever oscillatable on the pin 19, and yet permit the levers to advance or retract relative to each other in response to movement of the' crank, and in response to the relative positions assumed by the work-engaging jaws as they positively and separately engage the work; and (2) to store jaw-opening energy by compression in the spring whereby the spring may effectuate movement of the levers to assist in the opening of the jaws, as will hereinafter be specifically explained. Adjustabilities afforded in the various links, and the yieldability of the spring permit ready accommodation of the apparatus to work of varying size and shape.

For engaging the aforementioned latch 84, the pawl is pivotally mounted on pin I8I, fitted in suitable bearings I82 located in the base of carriage or draw head 38. A spring I83 connects pawl 85 and an anchoring pin I84, and tends to hold the pawl against either latch 84 (Fig. 3), or the base of crank 82 under the said latch. For moving said pawl from its latched position under latch 84, a.longitudinally-extending trip rod I85 is mounted in bearings I86 on top plate 18 of carriage 38. The said trip rod is adjustable for length, as indicated in the drawing, and is so mounted upon the carriage as to contact die head 3 as the carriage approaches said die head. Upon contacting die head 3, trip rod I85 moves against pawl 85, thereby unlatching crank 82 and allowing movement of the said quadric-crank linkage to take place.

The operation of the carriage will not be enlarged upon since it will be found fully set forth in our application, Serial No. 341,696, abovementioned. 1

Mandrel section of the bench located on the stock feeding side of the die head 3, are a plurality of mandrel-supporting members 24.

Operation Assuming a tube on a mandrel rod in the loading position, the carriage30 on the tracks 3| at some distance from the die head 3, and the draw chain moving, such as would be the case following completion of a previous drawing operation, a cycle of operations may be instituted by the closing of a control switch (not shown) adapted to initially energize the return chain operating motor 82.

Upon energization of the carriage return motor 62' movement of the carriage 33 toward the die head 3 will begin. The limit switch dog 39 on carriage 38 will first strike the limit switch 45 which, because of the previous closing of limit switch 44, will cause means not shown to index the mandrels to present a tube opposite the die.

At a position along the main frame of the draw bench nearer the die head 3, the limit switch dog 33 on the carriage 30 engages and operates limit switch 48. Upon the movement of limit switch 40, the field control of the return drive motor 52 is, in the operation here described, modified to bring the return speed of the carriage to a substantially constant base value.

At a position along the main frame of the draw bench still nearer the die head, the said limit switch dog 38 engages and operates limit switch 44. Upon the movement of limit switch 44, means not shown are adapted to push the mandrel into the die. At this position the pointed end 9 of the tube extends through die 4 for engagement by the jaws 33 and 34 of the drawing carriage 33.

Upon further approach of the carriage 30 to the die head the limit switch dog 39 strikes and actuates successive limit switches 4|, 43, and 42, which in that order respectively decrease the speed of the return drive motor 62 by armature shunt control, decrease the speed of the draw chain 36 to a pre-set initial drawing speed, and stop the motion of the drawing carriage as it approaches the die head by applying dynamic braking through the drive motor 52.

As carriage 30 comes to rest at die head 3, trip rod )5 contacts the die head and releases pawl 85 irom under latch 84, whereupon hook 35 falls into and engages its arcuate portion 16 with a link of chain 36. The falling motion of the hook 35 imparts a closing movement to the jaws 33, 34 as described above, whereupon the Jaws engage and grip the pointed end 3 of a properly positioned tube 3.

The draw chain 36 may be moving at a slow speed or stopped as controlled by thalimit switch 43. It stopped the draw chain would then be started by a manually actuated switch or other device (not shown). Assuming that it is movingat a slow speed as here provided, immediately upon the engagement of the hook 35 with the draw chain, the carriage 38 begins its travel away from the die head and the drawing of the tube begins. Drawing tension through the chain, hook,

carriage, jaws, tube, mandrel rod bulb, and man- 5 drel rod raises the hook 35 to its normal position, where crank 82 is latched by pawl 85, clamps the jaws 33 and 34 upon the po'intedend' 3 of the tube 8, and brings the mandrel rod bulb ll into final registry with the die 4.

Before continuing with the description of the operation, it may be pointed'out that if the laws should fail to engage the end of the tube there will be no tension on the chain 36 and the hook 35 will not be substantially raised. Rather than permit the carriage 33 to travel out the full length 01' the frame, means for stopping the carriage and returning it again to the die head are provided. The roller follower 12 of hook release lever II will strike the cam 65, which will raise the hook release lever and will release the hook from the chain, whereupon the carriage 38 may have a short return travel back to the die head to re engage tube 8.

Assuming, however, that the jaws have engaged the end of the tube upon the falling of book 35 into the draw chain, the motion 01' the carriage outward under drawing tension will continue as first described. The hook will be raised and latched by the tension on the chain, but the laws will remain closed under the force exerted by the work tending to draw them into tighter engagement therewith despite the fact that compression of spring 88 aioredescribed will also tend to open the same. I,

The limit switch dog 33 on the carriage 36 will firstactuate and engage limit switch 42, resetting the same and electrically disconnecting from circuit the return drive motor 52 so that the return chains 3'! and 38, fixedly connected to the carriage, may cause reverse rotation of the drive motor 62 against no electromagnetic forces.

The limit switch dog 36 will next reset the limit switch 43 and cause acceleration of the drive chain 36 from its initial slow speed to normal 45 drawing speed.

The next limit switch 4| will be merely reset without eflect upon the cycle of operations.

Likewise the next limit switch 44 will be reset, to its first position, causing means not shown to become operative for tending to withdraw a mandrel rod, e. g. [8, and bulb, e. g. H, from registry with die 4. This tendency, however, will remain ineffective while there is drawing" tension on a tube 8, but will be adapted to withdraw the mandrel rod and bulg upon completion of the drawing operation.

The next limit switch 40 will be merely reset without eflect upon the cycle of operations.

The final limit switch 45 will be reset to an an ineffective position without affecting the cycle 01' operations, whereupon the electric and pneumatic control system will be then in condition W for operation as described at the beginning of this drawing cycle.

After passing these limit switches, preferably located within a distance from the die head corresponding to the minimum length oi tubeto be handled, the carriage 38 will continue to be drawn out along tracks 3! on main frame I by draw chain 35 until tube 8 is drawn-completely through die 4. When tube 8 makes it exit from die 4, there will be an immediate release of drawing tension throughout the draw bench: and the recoiling eflect of the tube 8 in connection with 15 the stored energy in the spring 88-will immediately open the Jaws 33 and 34 or carriage 30, whereupon thetube 8 will be released and allowed to fall onto any suitable unloading devices arranged therebeneath (not shown). At the same time the release of tension in the draw chain 36 will permit the chain to fall from engagement with the hook 35 and the carriage will come to rest, Also the pressure or air against the piston in the manipulating mechanism, will then be eiiective to move the mandrel rod and bulb out of registry with die I and to retract the same into and within its protective tubular shell It.

It will also be apparent from the foregoing description that this apparatus is adapted to the drawing of rods and bars not necessitating the use of mandrel rods and bulbs, upon the provision of a push rod in place or each, mandrel rod, which push rod would be adapted to advance the work into registry with the die. modification a fixed mandrel could be employed for drawing substantially hollow shapes.

It should be understood that many or the auxiliary devices with which this draw bench has been described are not essential to its useful operation, and that many other combinations and relations of the parts and associated devices may be employed without departing from the nature and scope of this invention as defined in the appended claim.

What is claimed is:

In a draw bench, a die, a bench irame extending from said die, a draw head movable on said frame toward and away from said die, a continuous drawing member, attaching means on said draw head for engagement with said drawing member and adapted to be raised thereby under drawing tension, means for locking said attaching means in raised position, means associated with said locking means adapted to release the same as the draw head reaches the die,

Also, in a similar whereby the attaching means is freed to engage the drawing member, thereby to initiate a drawing operation, an arm associated with said attaching means for raising the same when not lifted by said drawing member, said arm being disposed at one side of said draw head, a cam means on said frame near said :iie'ior engagement by said arm only when there is no load on said drawing member, said arm normally clearing said cam means when said attaching means is raised under drawing, tension, and cam means on said frame near the end thereof opposite said die for engagement by said arm to disengage said attaching means from said drawing member if said draw head should be moved thereto by said drawing member, said attaching means being raised into position to be held by the locking means when said arm is actuated by engagement with either of the cam means.

' RAYNAL W. ANDREWS. Ja.

ARTHUR T. DEILY.

aernaancas crrnn The following references are oi record in the tile of this patent:

UNITED STATES PATENTS Number Name Date 1,496,125 Larson June 3, 1924- 1,568,'793 Atkins Jan. 5, 1926 1,951,073 Wallis Mar. 13, 1934 1,541,424 Linderme June 9, 1925 2,196,646 Smith Apr. 9, 1940 FOREIGN PATENTS Number .Country Date 451,481 British Aug. 6, 1936 798,144 French May 9, 1936 4,622 French Sept. 2, 1905 489,388 British July 26, 198B