US3525247A - Stretch bending machine with segmental die,tolerance detector,and safety shock absorber - Google Patents

Description

Aug. 25, 1970 Q RAUER ET AL 3,525,247

TOLERANCE STRETCH BENDING MACHINE WITH SEGMENTAL DIE,

DETECTOR, AND SAFETY SHOCK ABSORBER .4 Sheets-Sheet 1 Filed Jan. 8, 1968 Aug. 25, 1970 E H BRAUER ET AL 3,525,247

STRETCH BENDING MACHINE WITH SEGMENTAL DIE, TOLERANCE DETECTOR, AND SAFETY SHOCK ABSORBER Filed Jan. 8, 1968 .4 Sheets-Sheet 2 INVENTOR. I 'm% I I 44 ATTORNEY Aug. 25, 1970 E H. BRAUER ETAL STRETCH SENDING MACHINE WITH SEGMENTAL DIE, TOLERANCE Filed Jan. 8, 1968 DETECTOR, AND SAFETY SHOCK ABSORBER .4 Sheets-Sheet 5 C v SUPPLY INVENTOR.

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I 3 22 ATTOENEK 3,525,247 TOLERANCE 25, 1970 E. H, BRAUER E STRETCH BENDING MACH]:

NE WITH SEGMENTAL DIE,

DETECTOR, AND SAFETY SHOCK ABSORBER .4 Shegts-Sheet 4.

Filed Jan. 8, 1968 INVENTOR. M 71 ,4

9+ ATTOEWEK United States Patent ABSTRACT on THE DISCLOSURE The present machine is one by which a structural member, such as an I-beam, channel, plate, or the like, can be formed into curvilinear shape by bending it transversely of its length into conformance with a segmental curvilinear die while tensioning it endwise into its yield range. Tension applying devices grip opposite ends of the member for applying the required tension and are movable back and forth in a path extending transversely of the length of the die so as to lay the member onto the diesegments while the tension is maintained. The segments are adjustable to different positions, for forming bends of different radii, by power devices controlled by a numerical control or programmer such that repositioning of the die segments for each different selected shape can be effected quickly.

The improvements herein are as follows:

A shock absorbing device combined with a tension applying device for reducing shocks in the event of breakage of the member being tensioned.

Error indicator means which, when the member is formed, checks the shape of the member at a number of stations, such as at each die segment, and indicates conformance and non-conformance, and the extent to which the non-conformance is above or below tolerance limits. This checking may be effected while the member remains under tension or after the tension is relieved.

Brakes are provided for locking each die segment against creepage upon its reaching its programmed position.

This invention is an improvement on the invention disclosed in the co-pending application of Edwin H. Brauer and T. Virgil Huggett, Ser. No. 612,982, filed Jan. 31, 1967, now Pat. No. 3,426,569, and entitled Stretch Forming Machine and Segmental Adjustable Die Combination. This invention relates to a stretching machine, and particularly to a stretch bending machine for bending rolled structural members, such as I-beams, channels, bulb beams, and the like.

As more fully disclosed in the above-entitled application, the machine is one by which the structural members can be bent transversely of their length against a curvilinear segmental die into curvilinear form while tensioned into their yield range. The segments are adjustable, each to its desired position, by power means controlled by numerical control, and the segment faces can be positioned thereby to define selectively curves which are concave at one side only or are in the form of S or reverse curves.

In such machines, upon release of the member after bending, there is a tendency for spring-back to a degree beyond selected tolerances. Even during forming it may occur that certain portions of the piece do not engage the die segments as intended. In accordance with the present invention, the failure to engage any selected one of hte die segments or to spring back from engagement therewith beyond tolerable limits upon release of the tensioning forces is detected at each of a plurality of stations along 3,525,241 Patented Aug. 25, 1970 the die, selectively, usually one station at each die segment. Whether the beam engages the particular segment, or springs back, within the preselected tolerance limits, and whether the error is above or below tolerance, is indicated. This detection may be effected either during tensioning and bending or upon release of the tensioning force, as desired.

Again, since the heavy beams, such as ship ribs and the like, are being stretched and bent, extremely high forces are developed which, upon breakage of the member, release tremendous absorbed energy which is reflected in the stretching devices. In accordance with the present invention these forces are absorbed by shock absorbers operable by the fluid in the hydraulic stretching devices.

There also exists the tendency of vibration occurring as a result of stretching and releasing of the workpiece and the like to cause the die segments to creep along the driving screws which move them to their respective positions. This creepage is eliminated.

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

FIG. 1 is a diagrammatic top plan view of a machine embodying the principles of the present invention;

FIG. 2 is an enlarged fragmentary longitudinal sectional view of one of the stretching piston and cylinder assemblages of the invention;

FIG. 3 is an enlarged fragmentary side elevation of one of the die segments and supporting equipment, as indicated by the line 33 in FIG. 1, part thereof being shown in section to disclose the error detector mechanism;

FIG. 4 is a diagrammatic illustration of the electrical circuitry used in the present invention;

FIG. 5 is an enlarged wiring diagram showing in more detail the electrical circuitry and connections of the detecting and indicating devices illustrated generally in FIG. 4; and

FIG. 6 is a diagrammatical illustration of a modified form of shock absorber used in the present invention.

Referring to the drawings, the machine comprises a rigid bed 1 which supports a segmental die and stretch units. The segmental die comprises a plurality of individually adjustable die segments 2 each of Which is to be adjusted along a lineal path transversely of the bed 1 to a position selected in accordance with the curvatures desired in the member to be stretch bent. To provide for such adjustment, suitable guideways 3 are mounted on the bed extending transversely thereof, and die carriages 4 are mounted in the guideways for movement lineally therealong. Each of the carriages 4 carries a die segment 5 having an operating face 6 against which a structural member or beam S is to be bent. For adjusting each carriage along the guideways 3, a feed screw 7, driven by a reversible D-C servo-motor 8, is drivingly connected to a follower 9 on the carriage.

As described in the above co-pending application, the servo-motors 8 are controlled by a numerical control or a programmer for positioning the carriages 4, and hence the die segment 5, in their respective positions.

Each of the reversible servo-motors 8 rotates its associated one of the feed screws 7 at selected speeds for a predetermined number of rotations dictated by the programmer. The shaft of the motor 8, in turn, drives a feedback unit 11. The feed-back unit supplies signals through a conduit 12 to a numerical control unit which includes a servo amplifier 13, a tape reader 14, through which a tape 15 is fed, and an interpolator 16. The servo amplifier 13 receives the signal from the feed-back unit 11 and receives command signals from the interpolator 16. The tape has been prepared for a predetermined setting of the die segments and its output command signals are a function of perforations in the pre-programmed tape. The servo amplifier 13 compares the command signals from the interpolator 16 with the output signals from the motor feed-back unit 11 and controls the motor accordingly in a well known manner. This particular type of numerical control is well known and available on the market. Adjustment of each carrier, and hence its associated die segment, is continued by the control until the command and feed-back signals are in balance, whereupon the associated carrier 4 is stopped. Conventional switch means, not shown, are built into the numerical control unit and arranged so that, as each servo-motor 8 drives its follower to dictated position, the switch means connect the numerical control unit to the next succeeding servo-motor 8 and associated feed-back 11. Thus, the functions of the motors 8 are carried out successively until all of the segments are in their preselected positions. Thus they may be readily moved to the proper position, and stopped therein, in response to the tape.

The feed screw is preferably self-locking against rotation by forces imposed on the carrier 4 and by vibrations and the like in the machine. However, in order to eliminate any possible creepage due to slight rotation of the screw 7 under the influence of these vibrations, brakes 18 are connected to the screws 7, respectively.

Each brake 18 may be a conventional spring applied magnetically released brake with the coil connected in parallel with the associated motor 8 through a suitable time delay (not shown) so that the coil of the brake is energized and the brake released so long as the motor is energized, and is applied, after a slight time delay, when the motor 8 is deenergized.

The specific brake structure and the wiring for this arrangement and for controlling the motor by a numerical control may be conventional.

In order to apply tensioning forces to the ends of the workpiece S, stretching assemblages 18 are mounted on the bed 1, one at each end, as more fully set forth in the above-mentioned co-pending application.

Briefly, each stretch forming assemblage comprises a supporting carriage 20 having suitable rollers 21 operated in trackways 22 on the bed 1 and extending lineally transversely in the bed so that the carriage 20 can be driven transversely of the bed. Each carriage 20 is driven transversely of the bed by a suitable screw 23 driven, in turn, by a reversible motor 24 through reduction gearing 25. Each carriage carries a platform 27 which is secured to the carriage by an upright pivot 28 so that the platform 27 can swing about the axis of the pivot 28 relative to the carriage 20. The rear of the platform 27 rides on suitable slideways 29.

Secured in fixed position on the platform 27 for swinging therewith about the axis of the pivot 28 is a horizontal reversible piston and cylinder assemblage 30 comprising a cylinder 31 in which is disposed a piston 32 having a rod 33. A stretch head 34 for gripping the end of the member S to be bent and applying tension thereto is connected by suitable yoke and pivot device 35 to the piston rod 33. Thus, for bending the workpiece, tension into the yield range of the member S is applied by the head 34 and, while the tension is applied, the carriage 20 is moved transversely of the bed in the direction or of tensioning force so as to lay the stock against the faces of the die segments. The stretch forming assemblages 18 are identical.

If desired, tension controls may be provided, in which case the gripping heads would be supported as described in U.S. Pat. No. 3,052,119 to Cyril J. Bath and No. 3,302,437 to Stanley M. Dolney.

As mentioned heretofore, it is desirable in the event of breakage of the member S, that the shock be absorbed. As best illustrated in FIG. 2, pressure fluid is applied to the reversible piston and cylinder assemblage 30 by a pump 37 driven by a motor 38. The supply is controlled by a stop and reversing valve 39. A pipe line 40 leads from one port of the valve to the rod end of the cylinder 31, and a line 41 leads from the other port of the valve to the head end of the piston 32. The intake and outlet ports of the pump are connected to the valve 39, and a sump 42 is also connected to the pump intake port. In normal operation, the piston 32 can be advanced, retracted, or stopped and locked hydraulically, all by operation of the valve 39. The Valve preferably is solenoid operated for remote control.

It is apparent that when the workpiece is under extremely high tensioning forces due to the introduction of pressure fluid into the rod end of the cylinder 31, a tremendous amount of energy is stored in the member S and the various stressed parts of the machine, particularly the stretch assemblage. If, while in this condition, the member S should break, or slip out of the gripping jaws, this energy would be reflected in driving of the piston 32 rapidly to the head end of its cylinder 31, which is to the left in FIG. 2. Normally the piston 32 would strike the head end of the cylinder 31 or the yoke and pivot device 35 would strike the rod end with a severe impact, thus transferring or applying destructive forces to the stretch forming assemblages and supporting parts.

In order to relieve shocks if either of these conditions should occur, a check valve device 45 is interposed in the line 41 between the valve 39 and the head end of the cylinder 31. The device 45 is one of which the valve is normally closed, but can be opened by pressure delivered through the line 41 from the valve 39 to the head end of the cylinder 31. However, a conventional control de vice 46 is provided and is connected in the circuit to the cylinder 31 and the check device 45 so as to maintain the check valve of the device 45 open so long as the tensioning pressure in the rod end of the cylinder 31 is greater than the return pressure in the head end of the cylinder 31. Thus, in normal operation, the stretch head of the piston 32 can be retracted for applying tensioning forces by admission of pressure fluid through the line 40 to the rod end of the cylinder and discharge of fluid from the head end through the then open check valve device 45 and line 41.

To restore the piston 32 to the right in FIG. 2, the valve 39 is operated to reverse the flow of fluid from the pump 37, and deliver pressure fluid through the line 41 which unseats the value 45, and allows the return of pressure through the line 40 to the sump 42 or pump 37.

In the event of release of stored energy and inertial forces upon breakage of the workpiece, the piston 32, rod 33, and head 34 would begin rapid movement to the left in FIG. 2, and the pressure in the rod end of the cylinder 30 would drop suddenly below normal. This drop in pressure, however, would cause the check valve device 45 to stop, or greatly reduce, instantly, the escape of pressure fluid through the line 41 from the head end of the cylinder 31, so that the fluid at the head end is, in operating effect, entrapped totally or to a suflicient degree to cause a rapid build up of pressure in the head end of the cylinder 101.

This entrapped fluid is used in absorbing shocks. For this purpose, the head end of the cylinder 31 is provided with a passage 50 which leads into an adjacent end of a supplemental cylinder 51. A piston 52 is reciprocable in the cylinder 51 and is normally held in sealing relation to the outer end of the passage 50 by means of high pressure expansible and contractible fluid, such as nitrogen which is entrapped in the cylinder 51 behind the piston 52. Thus, as the piston 32 starts to travel to the left, the otherwise trapped fluid in the head end of the cylinder 31 is applied to the piston 52 and drives it to the left against the increasing pressure of the entrapped initially high pressure nitrogen. The resistance of the piston 52 to movement to the left increases as it approaches the closed end of the cylinder 51 and progressively increases the compression of the fluid therein. As

a result, the piston 32 is constrained to return toward the head end of the cylinder 31 against the resistance of a relatively heavy pressure which progressively increases as the piston 32 approaches the head end of the cylinder 31. By this arrangement severe shocks are eliminated.

It is desirable also to check the condition of the workpiece or member S to determine whether or not it is within the proper tolerances and, if not, to adjust the die segments to bring it within such tolerance. For this purpose, an error indicting means, as shown in FIGS. 3, 4, and 5, is provided and comprises a plurality of sensing devices, preferably one for each die segment. Each device includes a sensing pin or probe 60 reciprocable in a bore in its associated segment 5. The probe 60 is urged by a spring 61 endwise so that its forward end, if unresisted, can pass outwardly beyond the operating face 6 of its associated die segment 5. The probe 60 is connected to signal producing means such as a linear variable differential transducer 62. The transducer 62 has an armature 63 which is connected to the probe in coaxial relation thereto and for movement therewith. The transducer may be of the conventional type having a primary winding 65 connected across the low voltage A-C source, indicated by the lines Al-AZ. The transducer has a secondary 66, the terminals of which are connected by conductors 67 and 68, respectively, to the opposite terminals of an A-C signal coil 69 of a signal responsive means. A resistance 70 is connected across the conductors 67 and 68. The signal responsive means includes an error indicator 71 having a coil 72, one terminal of which is connected by a conductor 73 to a 115 volt D-C supply 74 which may be of a conventional type. The other terminal of the coil 72 is connected to a pivoted conductor 75 which swings, in accordance with the signals received from the coil 69, clockwise and counterclockwise, respectively. The conductor 75 carries a contact 76 which is engageable with stationary contacts 77 and 78, respectively, depending upon whether the conductor arm 75 swings beyond a predetermined distance clockwise or counter-clockwise in response to the signals received from the transducer. The contacts 77 and 78 are connected in parallel to a conductor 79 connected to the D-C supply 74. The coil 80 of a control relay is connected in series with one terminal of the supply 74 and the stationary contacts 77 and 78.

A selector switch 85 is provided and has a swinging contact arm 86 connected to the conductor 68 between the error indicator 71 and the transducer 62. The switch 85 has a plurality of individual contacts 87 each of which is connected to one of the conductors 68 leading to one of the transducers 62. Thus, upon swinging of the arm 86 into contact with any selected contact 87, a circuit is established between the error indicator 71 and the selected one of the transducers 62 associated with the particular contact 87. Then, if the selected transducer is moved by its spring 62 to a position beyond that allowed or to a position less than that allowed, a signal is produced which is transmitted to the error indicator 71 and which, if the signal is due to exceeding and falling short of the tolerance preselected, causes the conductor arm 75 to swing to one side or the other of its normal position midway between the stationary contacts 77 and 78. If the signal is great enough in either instance so that the contactor 76 makes contact with one of the stationary contacts 77 or 78, the control relay coil 80 is energized for closing a circuit which indicates that an error in tolerance occurs. For indicating the occurrence of an error, a plurality of error indicating lights 88, one for each transducer, are provided. These lights are connectable across 115 volt, 60 cycle A-C source, indicated by the lines L1L2. Each light 88 has one terminal connected to the line L2 and the other terminal connected to a common line 89 which in turn is connectable to the line L1 through a normally open contact 90 of the control relay 80 when both the contact 90 and a normally open ON and OFF switch 91 are closed. Interposed between the terminal of each light 88 and the line 89 is a switch portion of the connector switch which comprises a common selector swinging arm contact 92 connected to the line 89 and operable to engage the contacts 93, respectively, which are connected to the terminals of the lights 88, respectively, so that each light selectively can be connected across the lines L1 and L2 upon closure of the common contact 92 with the particular contact 83 associated with the light. However, if there is insufficient signal to make contact between the contact 76 and one of the contacts 77 and 78, the normally open relay contacts 90 remain open and no error is indicated. If the signal is beyond tolerance, then contact by the contactor 76 with either contactor 77 or 78 energizes the control relay closing its contacts and establishing through the selected one of the lights 88.

Preferably the arms 86 and 92 are mounted on a common shaft and hence rotate together in fixed position relative to each other so that the circuit established by the arm 92 and contact 93 and any particular light 88 is established at the same time that a circuit is established through the contact 86 and the contact 87 to the transducer represented by the particular light. Thus, either when the formed member S is under tension or after the tension is relieved so that spring-back can occur, the member can be checked as to shape to see Whether it is within the tolerance limits permitted. For this purpose, each given die segment 5 can be checked selectively, relative to the workpiece by operating the indicator switch to select the transducer for the selected one of the segments.

If the light 88 thereof does not operate, the member S falls within the tolerances permitted. If the light operates, then the tolerance is beyond the limits permitted.

By viewing the error indicator, it can be determined whether the error in the finished workpiece is due to its being overbent or underbent at each particular location.

With the tension still released, the die segment at the particular location at which the error is indicated may be adjusted accordingly, and the tension reapplied until the piece conforms to the tolerance limits at each die segment.

Generally the members S are so constant that when the die segments have been set to the proper place so that upon the first stretching the required shape is obtained in one member, succeeding members may be formed without changing the position of the die segments. However, even then the selector switch should be operated for each segment to confirm the fact that the piece is within tolerances or to indicate at what point, if any, and to what degree, it exceeds the tolerances. All of this contributes to production of a better and more precise final shape, and a recordable history as to some variations from the norm. If in any instance a member must be re-bent at some location, after the re-bending, as described above, the tolerances at each of the die segments should be checked a second time. Again, a check may be made and if some particular segment is not in contact with the die, that segment should be repositioned to compensate for the error. When all of the die segments have been brought to proper position, the part may be regripped and restretched across the new die setting.

A modified type of shock absorber is illustrated in FIG. 6. For example, a stretch forming piston and cylinder assemblage 100, comparable to the assemblage 30 and having a cylinder 10.1 with a piston 102 operable therein, may be used. At the head end of the cylinder 101 is the usual port 103 which may be connected to a check valve, check device, and stop and reversing valve, such as heretofore described. The head end of the cylinder 101 is provided with a shock absorbing fixture 104 which comprises a cylinder 105 which, at its head end, is provided with a flange 106 by which it is secured to the head end of the cylinder 101. The cylinder 105 has a neck portion 107 which is secured in sealed relation within the head end closure of the cylinder 101 and which has a bore 108 extending therethrough and communicating the interior of the cylinder 105 with the interior of the cylinder 101 at the head end of the latter. Within the cylinder 105 is a valving sleeve 109 which is coaxial with the cylinder and spaced inwardly from the circumferential wall of the cylinder to provide a surrounding chamber 110. A spring restored piston 1'11 is reciprocable within the sleeve 109 and is provided with a stem 112 which is exposed in the head end of the cylinder 101. When, due to breakage of a workpiece, the piston 102 moves suddenly toward the head end of the cylinder 101, as hereinbefore described, in connection with BIG. 2, the rod 112 is forced by fluid pressure in the head end of the cylinder 101, or by engagement by the piston 102, to force the piston 111 to the left within the sleeve 109. The sleeve 109 has a plurality of ports 113 communicating the interior of the sleeve with the chamber 110. The chamber 110 has a port 114 which connects the chamber 110 with a suitable pressure tank 115. The ports 113 are graduated either in size, number, or both, or spacing, so that as the piston 111 is driven to the left within the sleeve 109, the resistance to the escape of fluid from the cylinder 109 increases progressively as the piston 111 approaches the left end of the sleeve 109. This operates in effect to reduce gradually the released forces and energy tending to drive the piston 102 to the left, thus reducing the shock for the purposes hereinbefore described. The tank 115 is one in which the pressure fluid is maintained under sufiicient air pressure to cause return of the piston 111 to the right in FIG. 6, due to the dilferential in the total effective pressure on the head and rod sides of the piston 111, after the pressure in the head end of the cylinder 101 is reduced to normal.

Having thus described our invention, we claim:

1. In a stretch bending machine:

an elongated curvilinear bending die;

stretching means at the opposite ends of the die, re-

spectively, operable to grip the opposite ends of an elongated member and tension the member endwise into its yield range, at least one of the stretching means being power driven transversely of the tensioning dimension so as to bend the tensioned member into engagement with a forward forming face of the die;

a plurality of sensing devices distributed along the length of the die, each device being operative to sense the deviation of an adjacent portion of a bent member from conformance with the preselected shape to be produced by the die at said portion; and

deviation indicating means rendered operative by the sensing devices.

2. The structure according to claim 1 wherein each device includes a signal producing means operative to produce signals representing changes in a preselected condition of the sensing device imposed by changes in the shape of the bent member, and the indicating means include signal responsive means which are rendered operative by said signals to indicate changes in said preselected condition, and thereby changes of the shape of the workpiece.

3. The structure according to claim 2 wherein each device includes a probe movable toward and away from the forward face of the die along a predetermined path;

resilient means biasing said probe along said path forwardly from the forming face into positions in which it can be engaged by a member bent about the die and moved thereby back toward the forming face, and said preselected condition being the positions of said probe;

said signal producing means are operated by the probe and reflect the position of the probe along said path, and

the signal responsive means are rendered operative by said signals to indicate when the probe has moved along said path beyond preselected limited positions.

4. The structure according to claim 2 wherein a selector switch is connected to said devices and to said signal responsive means and is operable to connect said devices, one at a time, selectively, to said signal responsive means.

'5. The structure according to claim 1 wherein the die is a segmental die having segments which are individually adjustable to selected positions to change the shape defined by the die;

means are provided for the individual segments, re-

spectively, each operable for moving its associated segment to preselected positions independently of the movement of the other segments; and

said devices are connected to the segments, respectively, each device for movement as a unit with its associated segment as its associated segment is moved to adjusted positions.

References Cited UNITED STATES PATENTS 2,850,071 9/1958 Kraybill 7297 3,365,921 1/1968 Dolney 72-12 2,457,483 12/1948 Martin 72297 2,553,092 5/1951 Hubbert 72-10 3,328,995 7/1967 Rohlfs 72297 3,426,569 2/1969 Brauer et a1. 72295 CHARLES W. LANHAM, Primary Examiner M. J. KEENAN, Assistant Examiner US. Cl. X.R.

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