US2974707A - Table drive for rotary metal forming machines - Google Patents

Description

March 14, 1961 G. H. PERKINS 2,974,707

TABLE DRIVE FOR ROTARY METAL FORMING MACHINES Filed Feb. 10, 1959 5 Sheets-Sheet 1 N INVENTOR. M 1!. yxflaw BY 2 S Q ATTORNEY G. H. PERKINS 2,974,707

TABLE DRIVE FOR ROTARY METAL FORMING MACHINES March 14, 1961 5 Sheets-Sheet 2 Filed Feb. 10, 1959 ill 255::-

HEET

March 14, 1961 G. H. PERKINS 2,974,707

TABLE DRIVE FOR ROTARY METAL FORMING MACHINES Filed Feb. 10, 1959 5 Sheets-Sheet 3 4 A TTOENEK March '14, 1961 G. H. PERKINS. 2,974,707

TABLE DRIVE FOR ROTARY METAL FORMING MACHINES Filed Feb. 10, 1959 5 Sheets-Sheet 4 INVENT OR.

March 14, 1961 G. H. PERKINS 2,974,707

TABLE DRIVE FOR ROTARY METAL FORMING MACHINES Filed Feb. 10, 1959 5 Sheets-Sheet 5 INVENTOR.

A ATTOENEY.

United States Patent TABLE DRIVE FOR ROTARY METAL FORMING George H. Perkins, Euclid, Ohio, assignor to The Cyril Bath Company, Solon, Ohio, a corporation of Ohio Filed Feb. 10, 19s9,ser. No. 792,304 sclaims. cl. 153-540 This invention relates tometal forming machines of the type disclosed inU.S. Letters Patent No. 2,514,830, issued July 11, 1950, to Cyril l-Bath, and particularly to anew and improveddrive for the rotarydie-supporting table thereof.

'As disclosed in the above entitled patent,'it is a common practice to drive the rotary table of such machines with a ring gear coaxial with the axis of rotation of the table, and in engagement with, and driven by, a suitable external pinion gear which, in turn, is driven through a speed reduction transmission from a conventional source of-motive power.

At the time of the invention'of the machine disclosed inthe above patent, the metals customarily drawn were relatively narrow strips, and small "diameter'rods and tubes, of ordinary steels, stainless steels, and the like, and of the gauges commonly used in connection with automobile manufacture. In these particular metals, the elastic limit, yield point, and-ultimate strength are spread a considerable distance apart so that, 'even though the yield point be exceeded an "appreciable amount tempo-v rarily during stretch forming, there is no danger of approaching too closely, or of passing beyond, the ultimate strength of the metal and'seriously damaging the crystalline structure or breaking the work piece. I

At' the same time, since the machines were relatively small compared to the present machines, the static inertia 2,974,707 Patented Mar. 14,

For example, in present machines, tables which 'themselves weight four to five tons are not uncommon, and to start such amass and its driving mechanism without a sudden jerk has become'increasingly difficult and,'.in fact, almost impossible by the means heretofore used;

Consequently, it is apparent that the utility of the machines would be circumscribed considerably unless some means could be provided by which this sudden increase in tension, due to the starting jerk of the heavy table and machine, could be overcome, and the starting of the heavy tables and the moving parts could be effected gradually and smoothly. The optimum desired, of course, is to start the table with such small successive increments of movement and applied power that there is no jerk of the table and no sudden increase in the stress on the workpiece.

One problem is to hold the table stationary while applying, by the yieldable tensioning' means, the initial stretch forming force to tension the stock to its yield point and then, gradually reducing this tension to a'selected tensioning force below the yield point but above the elastic limit, and then to start the table smoothly, without of the parts was low in relation to the stresses necessary for causing damage to, and breakage of,'the workpiece. Accordingly, thetables of such machines could be started readily and, though the starting vof the table'would impose a sudden and rapid increase in the tension applied after the stock had been stressed up beyond the elastic limit and to, or close to, or slightly beyond, the yield point, nevertheless the increase would not be so great as to endanger the stock seriously or to change greatly its crystalline structure. However, as the machines have become heavier for forming strip and sheet stock of heavier gauges and greater widths, and rods and'tubes 'of' gr'ea'ter diameter, the inertial stresses of the machines have increased, and it has become increasingly difficult, after gradually bringinglthe metal up to the yield point and dropping back below the yield point to a 'selected forming tension between the yield point and elastic limit, prior to starting the table, to maintain the selected forming tension within proper limits as the table is started and brought up to speed. Invariably, due to the weight ofthe table and driving mechanisms and slack in the transmission, the table starts suddenlywith a jerk and a resultant pull, which the stock is totally inadequate to withstand without'damage. I i Furthermore, at about the time that'this problem was becoming of some importance inconnection with the ordinary steels and the like, the high alloy metals were inultimate strength are relatively close'together.

a sudden jerk, and gradually to increase its speed.

The present invention is operative to overcome these difficulties and other problems in connection with formation of stock. Furthermore, the present invention contemplates a drive of such a nature that, when used in combination with wipe and stretch forming machines, the. driving means are engaged with the table in a direc tion generally radially of the table and opposite to the direction of thrust of the wipe forming shoe, 'thus, to some extent, counteracting the thrust and balancing the stresses on the table. I

Again, the present invention contemplates a drive by virtue of which a part only of'the drive need be used for light work and the entire drive can be used for heavy work. In addition, the driving means is such that one or a number of duplicate drives can be supplied for each machine for driving the table, depending upon the power required for theiuses to which the particular machine is to be put, thus providing power means more nearly in the proper relation to the majority of the work contemplated by the customer. This arrangement also makes possible the conversion of a machine originally acquired for lighter work into a machine capable of heavier work,

Various other objects and advantages of the present invention will become apparent from the following description wherein reference is made to the drawings, in which: H

Fig. 1 is a diagrammatic graph illustrating one of the principal problems in connection with such machines;

Fig. 2 is a top plan view of a combined wipe andstretch forming machine embodying the principles of the present invention, part thereof being broken away for clearness in illustration;

Fig. 3 is a front elevation of .the apparatus illustrated in Fig. 2;

' Fig. 4 is a top plan view of the apparatus illustrated in Fig. 2 with the driving mechanism embodying the principles of the present invention installed; I

Fig. 5 is-a right end elevation of the apparatus illus trated in Fig. 4; I

. Fig.6 is a front elevation of a brake. and clutch mech anism utilized in the present invention; i Fig. 7 is a right-end elevation of the structure ll us tratedinFig. 6;, 1 Fig.8 is aperspective view of'a clutch portion of .,the

7o b k a s tchmssha ma Fig. 9'is a fragmentary :view. illustrating the operation ot/che clutchg-and T .[Q

Fig. is a hydraulic circuit and flow diagram i1lustrating a control for the present invention.

Referring to Fig. 1, a graph is shown in which the pull exerted on the stock is plotted on the ordinate as against time on the abscissa. A curve 1 indicates the pull applied to the stock at difierent times during the forming operation. Starting at the origin, it is assumed that the table is stationary, the stock has been placed under tension sufficient to determine its yield point and the tension has been decreased to a selected point between the yield point and the elastic limit, at which the stock is to be formed. Thus, power has been applied to the stock by the yieldable stretch forming means for initially stretching it to its yield point. This power has been reduced to that desired for stretch forminga point above the elastic limit.

Thereupon, the table is started at point 2 on the curve. Due to the inertial stresses, the table cannot be started without a sudden jerk, particularly inasmuch as tension is being applied to the stock tending to rotate the table in the direction opposite to that in which it is to be rotated for stretch forming. Accordingly, this sudden jerk applied on the stock causes an abrupt rise in the pull exerted on the stock, so that the curve rises rapidly to a point indicated at 3. By this time, the static inertia of the table has been overcome and the continued application of power maintains the table at the proper speed. The sudden jerk imposed by the starting of the table does not continue but drops off rapidly to a point indicated at 4, at which point the table has steadied down to the proper forming speed, and thereafter the pull is maintained substantially steady during the remainder of the operation, or, if increased or decreased to adjust to changes in configuration of the die and the like, the increase or decrease is gradual. These changes in latter tension are predetermined and gradually applied and can be allowed for, and are not sudden changes.

Specifically, therefore, it may be said that one of the principal objects of the present invention is to so apply power to the table that the parts of the curve between points 2 and 3, and 3 and 4, are eliminated and, instead, the curve passes smoothly from the point 210 the point 4 without any appreciable change. Thus, the stress applied to the stock throughout the entire forming operation does not exceed the predetermined pull that is desired.

Referring therefore to the specific apparatus for carrying out this procedure, a combined wipe and stretch forming machine, such as illustrated in the above entitled identified patent, is shown for purposes of illustration. The machine comprises a frame 10 having a main portion 10a on which is mounted a stretch forming piston and cylinder assemblage and a lateral portion 10b on which is mounted a wipe forming piston and cylinder assemblage, so that the stock can be subjected either to wipe forming or stretch forming, or to both concurrently.

Mounted on the frame 10 for rotation about an upright axis or post 11 is a rotary table 12 on which is mounted a side face die 13. A suitable clamp 14 is provided on the table for securing one end of a length of stock S to be formed in fixed position relative to the die.

For stretch forming the stock, a stretch forming piston and cylinder assemblage 15 is provided on the frame main portion 10a. As described in greater detail in the above entitled patent, this stretch forming assemblage comprises a cylinder 16 in which is reciprocably mounted including the slide 19, is mounted on .a carriage 23 which is rotatable about an upright pivot 24 so that the assemblage can align itself properly with the point of tangency between the stock and the side face die during stretch forming.

Mounted on the frame portion 10b is a wipe forming piston and cylinder assemblage 30 comprising a cylinder 31 with a piston 32 reciprocable therein and having a rod 33 connected to :a pedestal 34 of a slide 35. The slide 35 is mounted in a slideway 36 for movement in a direction parallel to the axis of the piston and cylinder assemblage 30. A suitable wipe forming shoe 37 is mounted on the pedestal 34.

In order to drive the table 12 in opposite directions about its axis, as desired, the table is provided with a ring gear 38 coaxial with the bearing post 11.

The structure thus far described is fully disclosed in the above entitled Patent No. 2,514,830.

In accordance with the present invention, the ring gear 38 is in mesh with a plurality of pinion gears 40 which are distributed circurnferentially of the table 12. In the form illustrated, two such gears 40 are used, though more may be used, depending upon the torque .to .be applied to the table. The gears 40 are positioned across the table fromthe wipe forming assemblage 30 ,so that the thrust of that assemblage against the die tending to tilt the table toward the gears Wis-resisted by the gears, and the .stresses imposed by the two are to some [extent balanced and better distributed. The two gears 40 shown are arranged at opposite sides of a plane through the axis of the table and the axis of the assemblage 30 in the normal centered operating position of the assemblage 30, the gears 40 being placed about 37 to each side of such plane.

It is desirable that the driving mechanism of each gear 40 be identical with that of each other gear 40, and that each one of the driving mechanisms be such that it can provide adequate power .to drive the table for the light forming requirements of the .machine. Thus, to provide :a machine of increased tonnage from one of light tonnage, up to the full .capacity of which its physical structure is capable, all that is necessary is to add additional identical driving mechanisms and distribute them circum-ferentially of the machine.

Pressure fluid for operating the piston and cylinder assemblages is supplied from a suitable pump 41 driven by an electric motor 42, which may be the motor which drives a pump forsupplying pressure fluid for operating the gears 40.

The assemblage 15 is connected to the pressure source supplied by the pump through a suitable control valve 43, and the assemblage 30 correspondingly is connected through a suitable valve 44, these valves being the customary valves by which pressure fluid can be supplied to either end-of the associated assemblage ,and the opposite end vented concurrently, and, by which, when desired, both ends can be vented or blocked, concurrently, in accordance with the desires of the customer. The specific manipulations of the piston and cylinders for the forming operation are ,fully set forth in the above entitled patent and form no part of the present invention.

As mentioned, the tables in machines of this type have reached large sizes, four to five tons and largerbeing not uncommon. Likewise, these tables are of large diameter. Since they are designed to form various large sheets of metal and subject it to extremely high forces, they are'usually driven at comparatively slow speeds. and, for economical drive, are driven through reduced speed transmissions in which the speed reduction from the driving motor to the table may be reduced to as much as one revolution of the table .to 4.3100 revolutions, or more, of the motor.

Each driving mechanism, as best illustrated in Figs. 4 and 5, comprises a speed reduction power'transmission 45 which may be o'f the--conventional reduction 'geartypc.

The transmission 45 has a driving shaft 46, one end of which, indicated at 46a, extends out of the one side of the transmission housingand the other end of which, indicated at 46b, extends out of the opposite side. The transmission has an output shaft 47 which is drivingly connected to a worm gear 48 to which, in turn, is drivingly connected a pinion gear 49 keyed to a shaft 50 to which the gear 40 is also keyed in coaxialrelation. Thus the drive of the table is through the speed reduction transmission 45, and if the shaft 46 is turning 4300 revolutions per minute,- the speed of the gear 40 is such that the table 12 is turned one revolution per minute. The transmission 45 is driven by a. pair of. hydraulic motors the line 56, and, again, both of them are responsive t6 the valve 58.

Mounted on the shaft 46 is a tachometer 64 which supplies electric signals in accordance with the speed of the motors 51 and 52 through an amplifier 65 to a signal responsive control 66 on the pump 54, thus changing the volumetric delivery of the pump in accordance with the tachometer reading. This control is of a well known type which can readily be set so that, if the speed signal indicated -by the tachometer varies appreciably from that preselected, the volumetric discharge of the'pump 54 will be varied accordingly so as to increase or decrease 51 and 52 which are connected in coaxial relation on the same shaft extension 46a.

As herein more fully set forth, the hydraulic circuit leading from the pump to the motors is such that the motors can be connected in parallel, or one of the motors can be used alone, thus providing'motive power more in keeping with extremely heavy forming operations and relatively light forming operations, respectively. Fluid pressure is supplied to the motors, as will be more fully described hereinafter.

At this point, it should be noted that there is' another distinctive advantage in having a plurality of the identical driving mechanisms, and having a plurality of identical motors for driving each mechanism. The inertial stresses due to the starting of the table are not merely due to the weight of the table itself but are augmented by the additional weight of all of the driving parts back to,-and including, the hydraulic motors 51 and 52. Thus the inertial forces to be overcome are reduced if only one of the driving mechanisms is employed, whereas it is increased ifa number are employed. Furthermore, if only one mechanism is employed, inertial forces are further reduced if only one motor of the mechanism is employed. All of these factors enter into providing a power source in keeping with the operation and in providing smoother operation. Obviously, the less .the inertial forces, the less is the danger of causing a sudden jerk in the table, and the morenearly can the optimum of starting the table with almost microscopic increments in the speed of rotation and in applied power, both of which gradually increase until the proper power and table speed, be obtained. It is desired that the hydraulic motors operate, however, at the proper speed and, for this purpose, suitable controls may be, provided. As illustrated, the power supplied to the motors is from a variable volumetric delivery hydraulic pump 54 driven by an electric motor 55. The preselected pressure fluid supplied by the pump is delivered to the main lines 56 and 57 through a suitable reversing valve 58. A suitable supplementary pump 59 may be provided for maintaining v the system loaded with pressure fluid during periods when it is inoperative or idling. The pressure fluid is conducted from the lines 56 and 57 to suitable control valves 61 arranged one control valve for each one of the driving mechanisms. Since the driving units are the same in form and function, one only will be described.

Each valve 61 is arranged to connect its associated motors 51 and 52 hydraulically in parallel with each other, or to connect the motor 52 to the source and the motor 51 for idling. In the form illustrated, the valve 61 has a plug 62 which normally is in the position shown, the plug portion 62a being operative. The plug portion 62a, when in the position illustrated, blocks the lines 56 and 57 at a point between the motor 51 and pump 54 and beyond the leads to the motor 52. At the same time, it connects the input and discharge of'the motor 51 together so that the motor 51 can idle. Thus, only the motor 52 is operable in response to valve 58. When, however, the plug 62 is shifted so that the portions 62b become operative, then both of-the motors 51 and. 52 are connected in parallel to the'pressure' line 57 and to the pump delivery, and'bring the'motors 51 and 52 to the proper speed. The pressure of the delivered fluid is preselected and set by a pressure control valve 67 which may, if desired, be set to different values during stretch forming if dictated by the requirements of the partic: ular piece being formed.

Since it isdesirable to operate the apparatus from a central control panel, the valve 61 may be operated by a suitable solenoid, such as indicated at 68, and the valve 58 may be operated by a suitable solenoid such as indicated at 69.

As mentioned, it is desirable to preload all of thedriving mechanisms including the motors 51 and 52, the speed reduction transmission 45, the mechanism connected between it and the gear 40, the gear 40, the'ring gear 38, and table 12. This can be accomplished by supplying pressure .flu idto the motors 51 and 52 in a quantity sufiicient to drive them in the selected table driving direction sufliciently torotate the table slightly. Since reduction is 4300 motor revolutions to one table revolution, the motors can operate slowly to drive without moving the table appreciably. Thus slack is eliminated and static inertia is partially overcome. Accordingly, the startingof the table can be 'efiected by gradually increasing the delivery of the variable delivery pump 54. While this pressure is being maintained and the table either is creeping by negligible increments, or is merely subject to slight torque sufiicient only' to balance the friction, the stock is connected at one end to the clamp 14 'and'at the other end to the stretch forming head 21. In this condition, pressure is admitted to the rod end of the stretch forming piston and cylinder assemblage 15,

for applying tension on the stock to bring the-stock up to its yield point. However, when this pressure is applied, the resulting tension on the stock tends to rotate the table in a direction opposite to that in which it is rotated by the motors 51 and 52. For example, in Fig. 2, the drive to be maintained for the particular stretching operation is such as to urge the table in a counterclockwise direction, whereas the tension on the stock is such as to urge the table in a clockwise direction.

.At this point, it should be noted that the power adequate onlyto maintain the table rotating by negligible increments so that it is practically static but with all the slack eliminated in its drive and with its static inertia overcome, all the way from the motors through to the ring gear 38, is insuflicient to hold the table against the pull exerted through the stock by the assemblage 15. If, before applying tension by the assemblage 15, the table driving power were increased to withstand its contemplated pull, then the table would be rotated at an appreciable speed and the stock would be subject to a severe jerk as the assemblage 15 became efiective or slack in the stock were eliminated. It is necessary, therefore, that the drive to the table be arranged so that, while the table and its driving mechanism has no, or only a slight, forward rotation free from slack, it has'a braking resistance to rotation in theopposite direction by the tension applied to the stock greater than will be applied by the assemblage 15. For this purpose, a one-way braking clutch deviceisused. Referring to the Figs. 2 through 9, the braking clutch device, indicated at 70, .is connected to the speed reduction transmission 45, preferably on the input shaft extension 46b of the transmission. It is to be noted that two one-way braking devices are provided and these operate in opposite directions, respectively, the purpose being that onedevice can operate when the table is driven in one direction and the other when the table is driven in the opposite direction, the table drive, of course, being reversed by the reversal of the motors 51 and 52. In each case, the one of the devices which is not functioning for its intended purpose is idling. Each of the devices comprises one member driven by the extension shaft 46b and another member which is secured fixedly to the frame of the machine or housing of the transmission 45. In the form illustrated, each device has a drum 71 which is fixedly connected to the shaft 46b, and an .outer drum 72 which, as will later be described, can rotate in one direction with the drum 71 but is prevented from rotation in the opposite direction relative thereto. The drum 72, in turn, is engaged by brake shoes 73 pivotally mounted on a frame 74 of the transmission and which can be operated to arrest rotation of the drum 72 and release the drum 72, respectively. The brake shoes 73 are released by a suitable solenoid 75 and applied by a spring 76. A suitable adjusting screw is provided for adjusting the tension of the spring 76 so as to control the shoe applying power.

Interposed between the drums 71 and 72 are a plurality of .cams 80. These cams are arranged so that when the shaft or drum 71 is driven in one direction, they interlock the drum 71 and the drum 72. When the 71 is driven in the opposite direction, they release the drum 71 from the drum 72.

As best illustrated in Figs. 6 and 7, for example, if the drum 72 is constrained from rotation by the brake shoes 73, and the drum 71 is driven as indicated by the arrow 81, for driving the table 12 in the stretching direction, then the cams 80 rock so that their peaks 82 are released from the drum 72, in which case the drum 71 and the shaft 46 can turn unrestrained and drive the table for stretching. On the other hand, if the pull on the table by the assemblage 15, through the stock, is such as to tend to reverse the direction of rotation of the table 12, and thereby the rotation of the shaft 46, .then the drum 71 would be turned in a clockwise direction, and if the drum 72 is then held by the brake shoe 73, the cams 80 are rocked, as indicated by the arrows 83, so as to wedge the peak 82 firmly against the drum 72 and lock the drums together. Thus, the brake mechanism 70 is operative through the drum 72 to permit the drum 71, and therefore the shaft 46, to turn freely in the table driving direction and to prevent its return in the opposite direction. This amounts, in effect, to a ratchet connection which permits the shaft 46 to turn in the proper direction for driving the table against the pull exerted by the stretch forming assemblage, but which locks to prevent the return in the opposite direction, the teeth of such a ratchet being, in fact, infinitely small, .since the relative circumferential displacement of the drums 71 and 72 is so slight for eifecting the .wedging and releasing action of the cams 80 that it might be said to be instantaneous. For example, the trelativerotation of the drums .through a circumferential distance of a .very small fraction of an inch is all that is necessary to move the cams from released position into firm locking position, thus the ,drum 71 and the shaft 46 may turn freelyinone direction hut, upon avery, very slight movement in the opposite direction,-they are latched. Since thisslight movement ,must be reflected to the table through a reduction gearing which supplies a reduction in the neighborhood of 4300 to 1, the slight relative rotation of the two drums for causing the release andengagement of the cams 80 is not reflected in any noticeable or measureable movementpn the table, being, for example, one forty-.threehundredthof one sixteenth of aninch at the most. If only one one-way clutch 8 reversible drive, then the brake is not essential, but, instead the drum 72 is permanently secured to the frame 74 in a non-rotative position.

The two. clutches of each driving mechanism are arranged so that each operates in an opposite direction to the other, as mentioned, so that the shaft is free to drive the table in one direction and prevent its return in the opposite direction by virtue of locking of one of the drums 72 and releasing of the other. Therefore, the brakes are provided. The clutches preferably are located on the inp t shaft of the transmission so that the torque to which they are subjected is relatively small compared to the torque applied to the table 12. If it is desired to reverse the'entire driving mechanism, the drum 72 originally looked is released by its brake and the opposite drum 72 of the same driving mechanism is latched by its brake. Thereafter the clutch works, in its driving cycle, in the proper direction for latching the table against rotation bythe application of stretch forming tension by the piston and cylinder assemblage 15, and, at the same time, for preloading and very slightly rotating the table by the driving mechanism so that there is no objectional jerk on the stock due to the starting of the table, the jerk being so very minute so as to be negligible so far as the present metals such as the high titanium alloys and the like are concerned. By increasing the number of driving mechanisms, smoothness of operation can be increased for higher power machines, but ordinarily two or three drive mechanisms are suflicient.

Referring to Fig. l, the dotted line joining the points 2 and 4 indicates that there is a very slight, almost imperceptible, increase in tension on the stock due to the starting of the table 12. However, since the table is already preloaded and ready to move, or is moving,

is required, as when the table is not equipped with a 1" there is no jerk due to the inertia of the parts but the table starts slowly and its speed gradually increases by minute increments to that for which the volumetric delivery of the pump is set, as determined by the tachometers 64. Accordingly, with the present invention, the parts in which high inertial stresses arise are reduced to a minimum for the particular job by virtue of using only the number of individual drive mechanisms required for the forces involved. Thus, the inertial stresses can be reduced to the point where one driving mechanism with one motor thereof supplies the power. Thereby, the power applied and the inertial stresses due to that power can he proportioned more nearly to the power that is necessary for the stretch forming operation. Furthermore, due to the positioning of the individual units about the axis of the table, heavy forces imposed by the wipe forming assemblage can be to some extent equalized and counterbalance so that the overall stresses imposed on the table and tending to tilt it are better distributed. This becomes important with the large sheets of the higher alloys in which the stresses imposed on the table by the wipe forming assemblage are extremely great.

Furthermore, by virtue of the one-way clutches and brakes, operation of the table can be obtained in either direction and the table preloaded so that the initial stretch forming tension can be applied without rotating the table, opposite to the forming direction, and 'the table can be started forwardly without a sudden jerk, all of the slack having been eliminated prior thereto and a substantial pressure built onthe table ,Whichcan thereby then be increased gradually and smoothly by small increments.

The words horizontal, vertical, horizontally, and vertically-' and the like, are used in the description and claims for convenience in describing the relative positions of theparts and not as absolutes, inasmuch as the invention has been illustrated as used with a machine in which a turntable is arranged with its axis extending vertically. Obviously, theentire machine can be disposed so that the axis of the turntable is other than vertical so long as the relative positions of the parts are maintained.

Having thus described my invention, I claim:

1. In a stretch forming machine, a frame, a turntable mounted on the frame for rotation about an upright axis and adapted to support a side face die, means rotatable with the table and adapted for clamping one end of the stock for holding the clamped end in fixed position relative to the die, a stretch forming assemblage on the frame and connectable to the opposite end of the stock for applying yieldable stretch forming tension thereto, driving means connected to the table, said driving means including a rotatable power transmission shaft drivingly connected to the table and operative, when rotatably driven in one direction, to drive the table in a stretching direction for stretching the stock, a oneway braking device including one member connected to the shaft for rotation by, and in fixed relation to, the shaft, a braking member, means interposed between the members and rendered operative by slight initial rotation of said one member by the shaft, when the shaft is rotated in a direction opposite to said one direction by rotation of the table opposite to the stretching direction, for locking the members together to prevent rotation of the table opposite to the stretching direction, and rendered operative by rotation of said one member by the shaft, when the shaft is rotated in said one direction, for releasing said one member for rotation relative to the braking member so that the shaft can rotate unrest-rained and drive the table in said stretching direction.

2. The structure according to claim 1 wherein said braking member is normally rotatable in said opposite directions, and the braking device includes a braking means which is operable to constrain the braking member from rotation and to release it for rotation, selectively.

3. The structure according to claim 2 characterized in that at least two of said one-way braking devices are dr-ivingly connected to ,said shaft, one being operable in one direction and releasable in the opposite direction, and the other, being operable in said opposite direction and releasable in said one direction, and means to render said devices operable and inoperable, selectively.

References Cited in the file of this patent UNITED STATES PATENTS 2,514,830 Bath July ll, 1950 2,514,831 Bath July 11, 1950

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