US2591085A

US2591085A - Machine for bending sheets

Info

Publication number: US2591085A
Application number: US97369A
Authority: US
Inventors: Donald O Mccall
Original assignee: Basalt Rock Co Inc
Current assignee: Basalt Rock Co Inc
Priority date: 1949-06-06
Filing date: 1949-06-06
Publication date: 1952-04-01
Anticipated expiration: 1969-04-01

Description

April 1, 1952 D. o. M CALL 2,591,085

MACHINE FOR BENDING SHEETS Filed June 6, 1949 5 Sheets-Sheet 2 :EIE E INVENTOR. 00mm 0. MC CALL BY 4 %W mg W April 1, 1952 D. o. M CALL MACHINE FOR BENDING SHEETS 5 Sheets-Sheet 5 Filed June 6, 1949 INVENTOR.

April 1, 1952 D. o. M CALL 259L MACHINE FOR BENDING SHEETS Filed June 6, 1849 5 Sheets-Sheet 4 fIE 5 IN V EN TOR.

DON/9&0 0. Ma 64.!

April 1952 D. o. MCCALL 2,591,085

MACHINE FOR BENDING SHEETS Filed June 6, 1949 5 Sheets-Sheet 5 N 3h :7 fIFjJ5fi C 50 "4 33 I a 33 fIE ED fIli E E] TIEJTZIE IN VEN TOR. QONALD 0- Mc CALL BY W Patented Apr. 1, 1952 2,591,085 MACHINE FOR BENDING SHEETS Donald 0. McCall, Napa, Calif., assignor to Basalt Rock Company, Inc., Napa, Calif., a corpcration of California Application June 6, 1949, Serial No. 97,369

15 Claims.

This invention relates to improvements in the art of bending sheets, particularly metal blanks which are substantially flat into elongated or tube-like shapes to form objects such as channels, pipes, masts, and similar cylindrical or tapered tubular articles of various cross-sectional shapes, or'to form blanks which may be subjected to a subsequent bending operation. The invention refers especially to the operation of bending the sheets about an elongated mandrel by forming members, such as brake rollers which are moved toward each other to force the sheet against the mandrel.

Although certain subcombinations f the mechanisms and operations disclosed herein are generally applicable to sheet-bending operations, e. g., to the forming of tubular articles of various geometrical shapes, with the longitudinal margins in varying degrees of proximity, such as spaced apart Widely or closely contiguous in readiness for welding the scam, the invention will be described herein as embodied in a method and machine especially designed to carry out a Ueing operation, i. e., an operation wherein substantially flat blanks (which may be entirely fiat or which may have certain parts not directly involved in the U-ing operation, such as the margins, already shaped or crimped) to a generally U-shaped cross-section to produce a trough-like article hereinafter for convenience called a channel. Such an operation involves bending the blankpartly about a mandrel, which may have any cross-sectional shape depending on the crosssectional shape of the desired product. The term channel isintended to denote only articles having a longitudinal opening, as distinguished from circumferentially closed tubes.

More particularly, the specific embodiment described herein asillustrative of the broader in vention is intended to be used in the second operation of a pipe-manufacturing process wherein welded pipe sections are fabricated from flat metal blanks. The main operations in such a process are: (1) A fiat metal blank having straight, parallel, smooth, longitudinal side edges, is passed through a crimping machine wherein rollers engage the margins and bend them upwardly. Typically, marginal strips each about 0.159 as wide as the blank, are curved upwardly to form arcs tangent to the intermediate part of the sheet and having a constant radius of curvatureworresponding to that of the finished pipe; these arcs will, therefore, each extend through about 57. (2) The crimped blank is fed through a U-ing machine, such as that described in this specification, to form a channel of cross-section that has, at its intermediate portion an are extending through slightly over a semicircle, and substantially straight portions converging slightly from the arc to the crimped marginal portions which converge more sharply toward each other. (3) The channel is placed in a forming press wherein two female die members having similar longitudinal forming cavities or grooves, each of semicircular cross-section, are forced together, thereby bending the channel into a closed tube of circular shape, with the longitudinal edges in abutment. (4) The edges are welded together and the seam is finished. A final straightening operation may follow.

U-ing operations used heretofore for forming such channels have usually employed female half-rounded die members into which the metal blank was forced by a power driven, elongated mandrel or bulb. Such practice has the drawback that great force is required for moving the mandrel and that the frictional engagement of the metal blank with the edges of the forming grooves of the die inherently results in a waste of power and frequently injures the metal blank by scuffing. Machines which use rollers or movable forming members to bend the metal blanks about a mandrel have generally been extremely complex in their construction and have necessitated the use of very heavy movable structural members to provide the strength required to move the rollers for bending the comparatively heavyv metal blanks; such machines have, moreover, usually involved elaborate mechanism for supplying power to the various parts of the machine at the proper times to synchronize the movements of the elements thereof.

Another difficulty in the design and operation of such machines has been that of conveying the blanks to the machine and of discharging the channels therefrom. For example, when pipes of 40-foot lengths and 12-inch diameter are to be fabricated from metal blanks inch in thickness, each blank weighs about one and a quarter tons, and it is important to provide a conveyor system which is reliable and is capable of handling such heavy blanks without manual assistance. In fact, in sheet bending machines, especially when heavy articles are to be shaped, the conveyor system is an essential part of the machine and cannot be regarded as a separate adjunct.

The need for conveyor systems has, in most prior machines, led to the provision of mechanism and associated driving gear for lowering the conveyor elements out of the way of the moving elements of the bending machine proper, and for re-elevating the conveyor elements thereafter for discharging the channel; or, in other instances, it has made it necessary to bend the blank from its position on the conveyor by an upward motion of the rollers relative to a stationary mandrel, an arrangement which has greatly increased the engineering and design difficulties because the rollers must move upwardly and toward each other along definite paths and yet be capable of exerting a large force for bending the metal.

It is an object of this invention to provide a comparatively simple machine of robust construction for bending sheet material about a mandrel which has laterally movable forming members, such as brake rollers, instead of a female die, wherein the forming members are reciprocably mounted, e. g., on slides, and the mandrel and forming members are mounted for relative movement causing the mandrel to move into and out of the mandrel opening between the forming members. Ancillary thereto, it is an object to move the forming members in translatory motion in or substantially in a common plane and to mount the mandrel for movement in a plane perpendicular thereto. A further related object is to adapt the machine for forming channels of different sizes, that is, for use with mandrels of different sizes, by mounting the forming members on movable slides the motion of which is coordinated with the movement of the mandrel, the forming members being adjustable with respect to the slides.

Another object of the invention is to provide a sheet-bending machine wherein the forming members are moved nearer together durin the movement of the mandrel into the mandrel opening between the forming members and the motion of these members is coordinated with that of the mandrel so that a highly favorable bending leverage acting on the blank is realized at all times and the power required for the bending operation is less subject to great variations during the power stroke of the mandrel. Ancillary thereto, it is an object to provide an improved driving mechanism for the forming members which requires no external source of power or control devices, but which derives power, both for advancing the forming members toward each other during the bending operation and for retracting the forming members to their separated positions, from the mandrel through a saddle or sheet follower in engagement with the sheet blank on the side thereof away from the mandrel, whereby the driving mechanism and the power system of the machine are simplified to an important extent. A specific object is to provide a hydraulic system and a gas pressure accumulator for storing energy during the movement of the mandrel into the mandrel opening and for expending the stored energy to move the forming members apart when the mandrel is moved out of the mandrel opening.

It is a further object of the invention to provide a sheet-bending machine havin a conveyor system'for feeding blanks to the machine and for discharging the resulting channels therefrom, preferably in the same direction of movement, wherein the conveyor system comprises a plurality of rollers rotatable about transverse axes (which may be horizontal or inclined in pairs in a V-like formation) and are supported by vertically movable supports which are yieldably urged to-raised positions and are adapted to be pushed downward by the downward movement of the 4 mandrel during the bending operation, whereby no additional power need be supplied to the conveyor supports and their movements are automatically synchronized with that of the mandrel. A specific object is to arrange the conveyor system with vertically movable roller supports (which may move up and down in translatory motion in a sliding frame or may be pivoted), wherein the supports are urged to raised position by hydraulic means pressurized from an accumulator.

A further object of the invention is to provide an improved method of bending sheet material into channels wherein such sheet material is bent partly about a mandrel by means of elongated forming members, preferably rollers, which are spaced apart initially and are held immobile and against which the blank is forced during the initial movement of the mandrel into the mandrel opening, and which are thereafter moved toward each other at a progressively increasing rate of travel in relation to the movement of the mandrel, whereby the total power applied at any moment during the bending operation is subject to lesser fluctuations than would otherwise be experienced, and the bending operation can be effected with a goven available power (energy per unit time) in a relatively short time.

Still a further object is to provide an improved method of bending pipe wherein the power is supplied entirely to the mandrel and the auxiliary elements of the machine, such as the laterally movable forming members and conveyor supports, are driven by the mandrel; wherein energy is stored in resilient means, preferably gas pressure accumulators, during the movement of such auxiliary parts during the bending operation; and where such stored energy is utilized for restoring the auxiliary parts to their normal positions during the retraction of the mandrel.

Still other objects of the invention will become apparent from the following description.

Although certain of the method steps and arrangements of parts are useful and operative regardless of their disposition with regard to the vertical, in the following summary of the invention the terms up, down, horizontal, vertical, etc., will be used merely for convenience and because they apply to the embodiment shown on the drawings, it being understood that such'directional expressions are intended only to denote relations between the various directions, movements, and parts. 1 Similarly, when movement of the mandrel downwardly into the mandrel opening between the forming members or rollers is referred to, it is evident that this is merely a simple way of describing the relative motion, and that such expressions are not intended to exclude equivalent arrangements, e. g., wherein the forming rollers move toward the mandrel.

In summary, according to the invention a substantially fiat blank (which may have crimped edges) is first positioned over a mandrel opening between a pair of relatively movable, longitudinally elongated forming members, preferably rollers. The forming members are spaced apart to provide a mandrel opening between them having a width less than the initial width of the blank and materially greater than the final width thereof, i. e., than that of the channel to be formed. The forming members defining the sides of the mandrel opening will be parallel when cylindrical channels are to be formed. A mandrel is then engaged with the upper side of the blank and moved progressively downward, thereby bringing the blank into engagement with the forming members (if it was initially positioned above them) and forcing the intermediate por tion of the blank into the mandrel opening and curving or bending the blank about the bottom of the mandrel. During the initial part of this movement the forming members are held substantially stationary, i. e., the width of the mandrel opening is maintained constant, or altered to a negligible extent. After the mandrel has completed a substantial part of its movement, e. g., between about one-third to two-thirdsof its movement, the forming members are moved toward each other while the movement of the mandrel is continued, the rate of motion of the forming members toward each other being increased relatively to the rate of movement of the mandrel, thereby forcing the side portions of the blank inwardly. Preferably, the inward ,movement of the forming members is such that no appreciable movement, viz., not more than about one-fifth of such inward movement, takes place until the mandrel has completed one-third of its downward movement. The inward movement is continued slightly beyond the distance necessary to bend the blank to its final shapeso as to allow for a slight spring-back in the blank. It will be understood that the invention is not limited to the forming of channels of any particular crosssectional shape, and that the outer edges of the blank may be brought together to any desired extent.

The invention will be described in greaterdetail by reference to the accompanying drawings forming a part of this specification and illustrating onepreferred embodiment of :the method and machine, wherein:

Fig. lis aside elevation View, partly in section, of themachine as emplaced in ,a pit;

Fig.2 is a plan view;

Fig. ,3 is a transverse sectional view taken on line.33 of Fig.1;

Fig. 4 is a fragmentary, transverse sectional view taken on line 44 of Fig. l;

' Fig. 5 is a diagrammatic plan view showing the piping to the accumulators; and

Figs. 6A to BE, inclusive, are diagrammatic end elevational views with the end conveyor roller (I removed, showing the successive steps in the operation of the mandrel.

A.-Frames and mandrel The machine is conveniently mounted in a pit H] to permit the blanks to be fed and discharged horizontally on "the conveyor rollers H, and Ila mounted at the ends near the ground level I2. The machine comprises a pair of upright frames l3 and 14 joined at the top by longitudinal girders l5 and i6 and supporting hydraulic press cylinders I"! and I 8 within which are doubleacting pistons for lowering and raising the mandrel or punch bulb when oil under pressure is admitted to the upper or lower ends of the cylinders by conventional piping, not shown. The machine is symmetrical about a transverse plane intermediate the upright frames (except for the piping) and only the mechanism at the frame l3, appearing in Fig. 3 will, therefore, be described in detail. This symmetry applies also to the movable conveyor rollers and their supports, to be described.

Referring to Fig. 3, the piston rod l-9 depending from the cylinder I! has a bifurcated end accommodating a connector 20 which is pivotally connected by a pin 2|. A mandrel girder 22, extending the full length of themachine, is bolted to the connectors' The girder has a vertical web 22a, suitably stiffened, carrying at the bottom acylindrical mandrel or punch bulb 23 which also extends the fulllength of the machine. The mandrel may have any cross-sectional shape, e. g., circular, conforming to the desired shape of the channel to be formed, and may be built up to the required size when a larger diameter is required by sliding a jacket 24 over the inner mandrel 23.

B.F0Tmz'ng roller girders and actuatin linkage Each frame has a pair of transverse openings 25 and 26 for accommodating slides 21 and 28, respectively, which are further slidably supported on

bed plates

29 and 3!] carried by the frame. The slides are fixed to brake roller girders 3| and 32, respectively. These girders extend for the full length of the machine and are supported by similar slides at the other upright frame, whereby they may move horizontally toward each other in a common plane. The girders carry a plurality of brake rollers 33 at their inner edges, the rollers being journalled for free rotation on pins 34 carried by the girders by brackets 34a and being arranged end to end to provide a row of individual rollers rotatable on separate, parallel journals and constituting a substantially continuous forming member for each girder. The upper faces of the rollers lie slightly above the upper faces of the girders. The girders carry a plurality of guide rollers 35 spaced longitudinally and mounted on vertical spindles which are mounted on laterally adjustable plates 36 to permit the horizontal interval between guide rollers on the opposite girders to be varied. These guide rollers maintain the blank 37 centered when it is fed into the machine, and the adjustment is desirable to adapt the machine to accommodate blanks of different widths.

Referring to Figs. 2 and 3, the slides 21, 28, are of cellular construction and carry horizontal rods 38 having threaded engagement with end plates 39 which are fixed to the slides. The rods 33 have square outer ends for receiving a wrench and enlarged heads at their inner ends which are rotatably housed in circular wells in blocks 40. The heads are secured to the blocks by threaded glands 4!. Blocks 6'] are movable with respect to the slide 21 or 28 in a direction parallel to the axis of the rods. These blocks are pivotally connected to connecting rods 42 and 43 by means of pins 4 3. The connecting rods are of equal lengths and bifurcated at their inner ends, the bifurcations on rod 42 being spaced apart to fit over the bifurcations of rod 43 as shown in Fig. 1. These bifurcations have eyes, whereby the inner ends of these rods are pivotally connected to a vertically movable piston rod 45 by .means of a pin 46. The piston rod has flattened sides to accommodate the inner faces of the bifurcations on the rod 43. The rods are connected symmetrically to the piston, whereby the thrust between the piston rod and connecting rods will lie in a common vertical plane.

It is evident that when the piston rod. 45 is depressed from the position shown in Fig. 3 the connecting rods will pull the blocks 40 toward each other; this movement is transmitted through the glands 4| and rods 38 to the respective slides 21, 28, thereby causing the brake roller girders 3l 32, to move toward each other. Conversely, when the piston rod is raised from a lower position to the position of the drawing the blocks 40 are moved apart, thereby moving the slides and girdersapart, toward the sides of the machine.

The greatest thrust in opposition to these motions occurs when the girders are pulled together to bend a blank about the mandrel, and during this movement the connecting rods and the rods 38 are under tension. It will be further noted that the horizontal distance between the girders, i. e., the width of the mandrel opening between the brake rollers, can be adjusted by turning the rods 38 to adapt the machine for forming channels of different widths; the rods rotate freely with respect to the blocks 48 but move axially with respect to the plates 39 because of the threaded engagement. Suitable lock or jamb nuts, not shown, may be provided on the rods 38 to lock them in adjusted position. Thus, the pin 46, rods 42 and i3, pins 44, girders 3i and 32 and brackets 34a constitute means interconnecting the movable blank-engaging piston rod 45 to the journals 34 for moving the rollers 33 toward their final, inner positions when said piston rod is driven downwardly by the continued movement of the mandrel after the lower side of the blank has engaged the top of the piston rod;

The piston rod G is vertically slidable within a cylinder 41 and is capped by a bolster 45a to which are secured a pair of vertically movable stops 48 (see Fig. 1). Engagement of these stops with the flange at the top of the stiffening frame 41b of the cylinder limits the upward movement of'the piston rod. Spacer plates 49 and a saddle or engaging member 56 are bolted to' the top of the bolster 45a. The saddle preferably has a cylindrical upper surface curved to conform to the lower outer surface of the channel to be formed. By changing the number of spacers 49 and/or by substituting spacers of different thicknesses the saddle 59 can be brought to the desired height, which is preferably below the blank 31 in its initial shape, so that the latter may be fed to the machine above the saddle. In most cases, moreover, the saddle will be spaced an appreciable distance beneath the blank when the blank is initially engaged with the brake rollers and the piston is at its highest position; this will be explained hereinafter under E. operation.

.C'.-Accumulator system is filled with a hydraulic fluid, such as oil maintalned under a suitable pressure, e. g., 50 to 400 lbs. per sq. inch, by an accumulator 5| connected to the cylinder by a pipe 52. The accumulator may be of any form and is known per se; it may, for example, be of the form described by Mercier in U. S. Patent No. 2,387,598, and have a rigid, metallic outer shell containing a rubber container or partition 53. A gas under pressure, such as air or nitrogen, is initially pumped into the compartment 54 on one side of the partition and the oil acts against the other side thereof. It is evident that when the piston 45?) is depressed by a sufiicient force acting against the saddle oil is forced through pipe 52. into the accumulator, thereby compressing the gas in the compartment 54 and accumulating energy. This energy is capable of raising the piston 4519 when downward force on the saddle is reduced. The pipin is shown in greater detail in Fig. 5, which shows that the cylinders ll and Ha, associated with me frames l3 and it, respectively, have their oil pipes interconnected by a pipe 55, so that the pressures are always equalized. To minimize flow of oil through the long pipe 55, and to permit the use of a smaller accumulator within the space available in the pit I0, it is preferred to provide a second accumulator 5la near the cylinder 41a and connected to the system by a pipe 52a, to act in parallel with the accumulator 5|. A tap 56 and valve 51 are provided for charging oil into the system.

D.-Conveyor system The conveyor system comprises vertically movable rollers located both between the upright frames and to each end of the frames, and supported so that, when in their raised positions, they are at the level of the rollers H and Ha mounted on the ground at each end of the pit Ill. The conveyor rollers between the frames will be first described, those beyond the ends being optional.

, Referring to Figs. 1, 2 and 4, a horizontal, longitudinal support girder 58, formed of a pair of structural channels, is disposed between the brake roller girders and extends between the upright frames. It is just short enough to be freely depressible without interference by the mechanism at the frames, such as the pins 46, the cylinders 4'! and 41a, and the saddles 50. The support girder is supported and guided for vertical movement by two vertical rods 59 and 59a which are connected to the girder at their upper ends by transverse pins and which are vertically reciprocable within

cylinders

60 and 60a, respectively, together with pistons (not shown) contained therein. These cylinders are supported at their lower ends by transverse pins. The cylinders are maintained in the desired vertical positions by rigid vertical guide posts BI and Gla. These posts have three vertical walls engaging the cylinders but are open on their mutually nearer sides to permit the cylinders to be pivoted upwardly into position during assembly. It will be seen that While both guide posts are effective to prevent lateral movement of the cylinder, each is effective in restraining the cylinder associated therewith against pivotal movement in the vertical longitudinal plane only toward the respectively nearer end of the machine. The upper ends of the cylinders are closed by collars 62 and 52a, which are not sealed to the rods 59 and 59a, but permit the passage of air into and from the space within the cylinder above the piston, and which limit the upward movement of these rods by engagement therewith of the upper ends of the pistons (not shown) carried by the rods within the cylinders.

The cylinders are filled with oil beneath the pistons. As is shown in Fig. 5, the lower ends of these cylinders are interconnected by a pipe 63 and short sections 63a and 63b of flexible hose.

The pipe 63 extends to the bottom of an accumulator 64, of the type previously described. (During normal operation valve Si is closed.) When the girder 58 is depressed the rods 59 and 59a cause their pistons to displace oil from their cylinders, thereby compressing gas within the accumulator 64 and storing energy which is available for raising the girder subsequently.

The support girder carries a plurality of idler rollers 65 and power driven rollers 66, all mounted on horizontal shafts extending transversely and having opposed frusto-conical sections, so that the rollers are tapered toward the centers thereof. These rollers are, therefore, capable of supporting fiat blanks resting on the widest portions 'at the ends thereof, as shown in Figs. 4 and 6A, and also capable of guidingly supporting channels resulting from the bending operation, as shown in Fig. 6E, for discharging the latter from the machine. The brake rollers 33 are mounted with theirhighest points slightly below the highest parts of .theconveyor rollers -65 and 66, so that flat blanks can be rolled into the machine without binding on the brake rollers. ltshould be noted .thatthe rollers ll mounted at the feed end of the machine are not taperedbut consistof a numberofdiscs on a common jourfor handling substantially fiat blanks; the rollers I Id, at the discharge end of the machine, are tapered to support and center the formed blank, such as channels, having rounded lower walls and upstanding sides. The power-driven conveyor rollers 56 at the feed end of the support girderare driven by means of sprockets fixed to their shafts and meshing with a sprocket chain 8'! which is, in turn, driven by a sprocket filo on a rotatable shaft. This shaft is driven by an electric motor 69 through drive sprocket 65, chain 68c and sprocket Hi. The machine being symmetrical, a similar motor and sprocket, not

shown, is provided for the power-driven rollers at the other end of glrdert'e.

The conveyor rollers 71 and Na at the ends of the machine are journalledon inclined booms 2 Ilia, respectively, having pivotal-supports at their lower ends as shown at 12b. The rollers are urged to raised position by oil pressure within cylinders 13 and 7311, having pistons (not shown) on piston rods 3'4 and Ma which .are pivotally con neotedto the booms near their upper ends. The nylinders are also pivotally supported at bottom of the pit as shown at 13?). Upward motionof the rollers is limited by engagement of the pistons with thecollars 15 closing the upper ends of the cylinders. These collars are not sealed to the piston rods but permit the escape of air from the space above the pistons. These cylin ders are filled with oil beneath their pistons. As

shown in Fig. 5, the cylinders .13 13s are provided with .flexiblehose l? and Ho, interconheated by a pipe is which is also connected to an accumulator lethrough a branch its, the accumulator being of the type previously disclosed. When .thebooms l2 and licare lowered by pivotal motion about their supports "5 2 3, the rods i i and flea enter the cylinders and the oil within the cylinders is displaced into the accumulator l9, therebycompressing gas within the accumu lator and storing energy which is available for subsequently raising the booms and their rollers.

The

pipes

63 and 78 are interconnected by a branch pipe 80 and valve 8! A tap t2 and valve .33 are connected to the branch pipe lilo. When charging thesystem, valves 81 and83 are openand oil is pumped into the system through tap 82. When the desired pressure has been reached the valves 6! and 33 are both closed. thereby isolating the accumulators 64 and 79. It is evident that the valve 81 and the provisionof separate accumulators E i and 79 for the two parts of the piping system associated with the conveyor rollers are optional, and that the conveyors may, if desired, be urged upwardly by a common accumulator.

E.--Opercttion The operation will be described a U-ing operation for forming a channel having the crosssection shown in Fig. 6!], it being understood that this example is merely illustrative of one particular type bending operation. When such a channel .is intended to be subsequently fed to a press wherein it is changed into pipe of circular crosssection, the radius of the lower, rounded part of the channel of Fig. 6E will be slightly less 10 than that of the final pipe. The initial blank 3! is substantially fiat but is shown to have crimped margins 31a and 31b curved with a radius of curvature corresponding tothat of the final pipe, and curving through an angle of one radian.

The mandrel Z3 is first built up to the requisite size by means of the jacket 24 to have a-radius slightly less than that of the lower, rounded portion of the desired channel, so to allow for a slight spring-back. The relation between the final channel and the mandrel is shown in Fig. 615;, wherein the spring-back is somewhat exaggerated for clarity.

The horizontal interval between the brake roller girders 3| and 32 is adjusted by means of the rods 38 so that the rollers 33 are spaced apart in the relation shown in Fig. 6A, leaving between them a mandrel opening which is ma terially in excess of the ultimate width of the blank as shown in Fig. 6E but smaller than the initial width of the blank. The height of the saddle 5c is also adjusted to a distance below the upper faces of the forming or brake rollers 33 to effect the proper vertical travel of the piston rod 45 required for moving the rollers 33 together to the desired interval, shown in EigfiD, at the end of the downward strokeof the mandrel. This is effected by increasing or decreasing .the number of spacers 49. Using less or thinner spacers lowers the saddle, whereby the saddle will be engaged at a later part of the downward stroke, and the resultant downward motion of the piston and the inward motion of th rollers 33 are reduced. Finally, the plates 35 are adjusted to space the guide rollers 35 apart slight- 1y more than the width of the initial blank 31; this is shown in Fig. 3.

At the start of the operation mandrel 23 is raised, and the conveyor supports and their rollersiiS, 56, H and Ha are at their elevated positions, at the level of the rollers II and Ho. The operations are then as follows:

1. A blank 3'! is fed longitudinally from the rollers ll over the conveyor rollers of the machine. The motors 69 are operated until the blank has reached a position centered in the machine, and the movement of the blank is then stopped by stopping the motor. The parts are now in the relation shown in Fig. 6A.

Gil is admitted to the upper sides of the main cylinders l7 and [B to move the mandrel irder and the mandrel 23 downward. This brings the mandrel into engagement with the upper face of the blank, and depresses the blank and the conveyor rollers and their supports. soon as the blank has been depressed sufficiently to bring its lower face into engagement with the upper faces of the rollers 33 the blank is forced into the mandrel opening and is progressively bent about the lower side of the mandrel. The rollers 33 remain stationary until the lower side of the blank comes into engagement with the saddles 50, as shown in Fig. 6B. The main bending force is, during this part of the operation, caused by the upward thrust of the rollers and the downward thrust of the mandrel, acting through a leverage determined by the horizontal distance between the lines of contact of the blank.

3. Continued downward movement of the mandrel continues the bending or" the blank about the mandrel and further depression of the conveyor rollers. The saddles 50 andpistons are now also moved downwardly, causing the connectingrods 42 and A3 to pull the slides 2i and 28 and the rollers 33 horizontally toward each other. This movement of the rollers is very gradual at first, and when the mandrel is at the level of the rollers they have thepositions shown in Fig. 66.

4. The downward movement of the mandrel is continued to the position shown in Fig. 6D, still further depressing the conveyor rollers and saddles, causing the rollers 33 to bend the upstanding sheets of the blank against the sides of the mandrel. The portions 310 and 31d above the point of tangency with the mandrel remain substantially flat. It will be noted that in this part of the operation the rate of travel of the rollers relative to the downward rate of travel of the mandrel is greater because the connecting rods 42 and 43 are inclined farther from the horizontal. Further, the main bending force is now caused by the horizontal thrust of the rollers and the mandrel, acting through a leverage determined by the vertical distance between the points of contact of the blank. The change from the relation of bending forces described in step 2 to this relation is gradual, and the bending forces in step 3 are due to both causes. This manner of bending the blank makes efficient use of the downward force of the mandrel during all stages of the bending operation and permits the blank to be bent about the mandrel through an are greater than 180, as is indicated in Fig. 6D.

, 5. The mandrel raised by admitting oil to the lower sides of the cylinders H and I8, to the position shown in Fig. 651. This permits the accumulators to elevate the pistons 45, thereby moving the rollers 33 apart, and also to elevate the conveyor supports and their conveyor rollers. The blank will spring back away from the mandrel to a slight extent when the rollers 33 are moved apart. At the completion of this step the U-ed blank is resting on the conveyor rollers and the bottom of the mandrel is spaced slightly from the blank.

6. The U-ed blank is discharged from the machine by operation of the motors 69, in the same direction as in step 1, whereby the blank will pass over the roller Ha.

In the foregoing operations, as illustrated in Figs. 6A-6E, the saddles i) were not engaged until the mandrel completed about one fifth of saddles 59 with the blank is also possible by em.

ploying a thicker spacer 49; for example, engagement of the blank with the saddles may occur simultaneously with'or even slightly prior to engagement of the blank with the rollers 33. In such casesthe rollers 33, while not entirely stationary during the initial part of the bending stroke, are still substantially so because the con necting rods 42 and cause only a very slow rate of inward travel during the first part of the downward travel of the piston 25. Hence, it is in these cases still possible to realize the preferred condition that the rollers 33 shall be substantially stationary, i. e., complete not over one fifth of their total inward travel during the first third of the bending stroke of the mandrel.

I claim as m invention:

1. A machine for bending substantially flat blanks comprising, in combination, a frame; a pair of opposed slides on said frame disposed for movement toward and away from each other;

a longitudinally elongated forming member on each slide, said forming members being substantially coplanar and disposed so as to provide between them a mandrel opening having, in one position of the slides, a width materially in excess of the final width of the blank; amandrel movable between the forming members into and out of the mandrel opening and in its outer position permitting a-blank to be placed between the forming members and the mandrel; means for forcing the mandrel into the mandrel opening; a movable blank-engaging member in the path of movement of the mandrel disposed to be engaged by the side of the blank away from the mandrel while the mandrel is forced into the mandrel opening and to be moved thereby in a driving stroke; linkage means connecting said engaging member and said slides for moving said slides and forming members toward each other during said driving stroke of the engaging member and for moving said slides and forming members apart during a reverse stroke of the engaging member; and means for movingsaid engaging member in said reverse stroke.

2. The machine according to claim 1 wherein the linkage means is arranged to move said slides toward each other at an accelerating speed in relation to the speed of said driving stroke.

3. The machine according'to claim 1 wherein the blank-engaging member is disposed to begin its driving stroke after the mandrel has entered said mandrel opening, and the linkage comprises a pair of transversely extending connecting rods in pivotal engagement with the engaging member and with the respective slides, whereb said slides and forming members are moved toward each other only after the mandrel has completed a part of its movement and the ratio of the speed of the slides to the speed of the engaging member is increased as said driving stroke progresses.

4. The machine according to claim 1 wherein the slides are mounted on said frame for movement in a common plane.

5. The machine according to claim 1 wherein the forming members are movable with respect to the slides toward and away from one another to permit the width of the mandrel opening to be varied for a given position of the slides said slides having securing means for fixing said forming members to said slides in any adjusted relative position.

6. A U-ing press for bending substantially flat blanks to form channels with rounded lower portions and upstanding, converging side walls comprising, in combination: an upright frame; a pair of opposed slides on said frame disposed for movement toward and away from each other; a longitudinally elongated forming roller on each slide, said rollers being substantially coplanar and disposed to provide between them a mandrel opening having, in one position of the slides, a width materially in excess of the width of the channel to be formed; a mandrel having rounded bottom and side portions movable into and out of the mandrel opening and in its outer position permitting a blank to be placed between the rollers and the mandrel; means forforcing the mandrel into the mandrel opening; a movable elongated mandrel;

blank-engaging member in the path of movement of the mandrel disposed to be engaged by the side of the blank awa from the mandrel while said mandrel is forced into the mandrel opening and to be moved thereby in a driving stroke; a pair of lateral links pivotally connected at their inner ends to said engaging member and at their outer ends to said slides for moving said slides and rollers together during said driving stroke at an accelerating speed in relation to the speed of said driving stroke, and for moving said slides and rollers apart during a reverse stroke of the engaging member, and means for moving said engaging member in said reverse stroke automatically when said mandrel is moved out of said mandrel opening.

7. A machine for bending substantially flat blanks comprising, in combination, upright frame means providing a passageway for longitudinal movement of a blank; a longitudinally elongated mandrel movable vertically with respect to said frame; forming means on each side of said frame and spaced apart laterally to provide a longitudinal mandrel opening, each forming means being adapted to engage a blank. at a plurality of longitudinally spaced points, the width of said mandrel opening being in excess of the width of the mandrel and said forming means being movably mounted on said frame means for movement to decrease the width of the mandrel opening; means for forcing the mandrel downward into the mandrel opening; conveyor means comprising rollers and vertically movable support means therefor disposed in said mandrel opening; means urging said conveyor means upwardly to a position for supporting a blank above the forming means; and means for moving said forming means to decrease the width of the mandrel opening as said mandrel is forced downwardly in said mandrel opening.

8. A machine for bending substantially fiat blanks comprising, in combination, a plurality of longitudinally spaced upright frames providing openings therein for longitudinal movement of a blank; a vertically movable, longitudinally gated forming members disposed to provide between them a mandrel opening having a width in excess of the width of the mandrel and movably mounted on said frames for movement to decrease the width of the mandrel opening; means for forcing the mandrel downward into the mandrel opening; conveyor means comprising rollers and vertically movable support means therefor disposed in said mandrel opening between said frames; means yieldably urging said conveyor means upwardly to a position for yieldably supporting a blank above the forming members; and means for moving said forming members toward each other as said mandrel is forced downwardly in said mandrel opening.

9. The machine according to claim 8 wherein the vertically movable support means comprises a longitudinally elongated girder .provided with guide means fo rvertical rectilinear motion and at least one of said rollers is provided with drive means for rotating the roller to move the blank longitudinally.

10. The machine according to claim 8 wherein the mandrel and forming members extend longitudinally through and beyond at least one of said frames to form an end portion of the mandrel opening, and a second conveyor means is provided in said end of the mandrel opening, said a pair of longitudinally elon- 14 second conveyor means comprising a vertically movable conveyor roller.

11. The machine according to claim 10 wherein said second conveyor means comprises a strut pivotally supported and journalling said roller in combination withv means yieldably urging said strut to a raised position for yieldably supporting a blank above the forming members.

12. The machine according to claim 8 wherein the means for moving said forming members toward each other comprises a vertically movable blank-engaging member in the path of movement of the mandrel disposed to be engaged by the lowerside of the blank during the downward movement of the mandrel and to be moved thereby in a driving stroke; and linkage means connecting said engaging member and the forming members for forcing the forming members toward each other during the driving stroke of the engaging member.

13. A machine for bending substantially flat lanks to form channels comprising, in combination, a plurality of longitudinally spaced upright frames providing openings therein for longitudinal movement of a blank and for movement of forming rollers and a mandrel; posed slides in each frame disposed for substan tially horizontal movement toward and away from each other; a longitudinal roller girder on each side of the machine connected to slides on the respective slides and transversely adjustable on said slides, said girders extending between said frames and through and beyond said frames; a longitudinal forming roller on each roller girder and substantially coextensive therewith, said forming rollers being substantially coplanar and disposed to provide between them a mandrel opening having, in one position of the slides, a width materially in excess of the width of the channel to be formed; a mandrel substantially coextensive withv the forming rollers vertically movable into and'out of the mandrel opening and in its outer position permitting a blank to be placed between the forming rollers and the mandrel; a vertically movable blank-engaging member at each frame beneath and in the path of the mandrel having its upper end below the upper level of the forming rollers when in. its upper position so as to be engaged by the lower side of the blank during the downward movement of the mandrel only after the mandrel has entered the mandrelopening; a pair of connecting rods for each engaging member pivotally connected to said engaging member and to the slides at the respective frame extending transversely for moving said slides toward each other when the engaging member is moved downwardly; pressure means for urging said engaging member to said upper position and adapted to store energy for raising said engaging member and moving said slides apart when the mandrel is retracted; conveyor means comprising rollers and vertically movable support means disposed in said mandrel opening between said frames; and pressure means for urging said conveyor means upwardly to a position for supporting a blank above the forming rollers and adapted to store energy for raising said conveyor means when the mandrel is retracted.

14. A machine for bending substantially flat blanks to form channels comprising, in combination, a frame; a pair of longitudinal rows of brake rollers, each row comprising a plurality of individual rollers rotatable on separate, parallel journals, said journals being movably supported a pair of opopening before the blank has 15 from said frame to afford movement to said rollers between initial, outer positions wherein the rollers of opposed rows are spaced apart to provide between them a mandrel opening having a width materially in excess of the final width of the channel to be formed and less than the initial width of the blank, and final, inner positions with rows; a longitudinally elongated mandrel having a'face with a transverse cross section convex toward said mandrel opening and movably mounted for movement into and out of said mandrel opening and in its outer position permitting a blank to be placed between the rollers and the mandrel; means for forcing the mandrel into the mandrel opening to bend the intermediate part of the blank about said face of the mandrel; movable blank-engaging means within the mandrel opening and in the path of movement of the mandrel disposed to be engaged by the side of the blank away from the mandrel during the initial part of the movement of the mandrel into the mandrel been bent about more than a minor portion, substantially less than 180, of said face and to be driven thereby; and means interconnecting said movable blankengaging means and said journals for moving said rollers to their final, inner positions when said blank-engaging member is driven by the continued movement of the mandrel into the mandrel opening for forcing the sides of the blank toward each other and against the sides of the mandrel. l

15. A machine for bending substantially fiat blanks to form channels comprising, in combination, a frame; a pair of longitudinal rows of brake rollers, each row comprising a plurality of individual rollers rotatable on separate, parallel journals, said journals being movably supported from said frame to afford movement to said rollers between initial, outer positions wherein the rollers of opposed rows are spaced apart to provide between them a mandrel opening having a width materially in excess of the final width of the channel to be formed and less than the initial width of the blank, and final, inner positions with decreased interval between rollers of opposed rows; a longitudinally elongated mandrel having a face with a transverse cross section convex toward said mandrel opening and movably mounted for movement into and out of said mandrel opening and in its outer position permitting a blank to be placed between the rollers and the vdecreased interval between rollers of opposed mandrel; means for forcing the mandrel into the mandrel opening to bend the intermediate part of the blank about said face of the mandrel; movable blank-engaging means within the mandrel opening and in the path of movement of the mandrel disposed to be engaged by the side of the blank away from the mandrel after entry of the mandrel into the mandrel opening and when the blank has been bent about only a minor portion, substantially less than 180, of said face and to be driven thereby; and means interconnecting said movable blank-engaging means and said journals for moving said rollers toward each other toward their final, inner positions only when said blank-engaging member is driven by the continued movement of the mandrel into the mandrel opening for forcing the sides of the blank toward each other and bending them about the remaining portions of the sides of the mandrel.

DONALD O. MoC'ALL.

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

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