US3075636A

US3075636A - Draw bench loading measurements

Info

Publication number: US3075636A
Application number: US856112A
Authority: US
Inventors: Ralph M Manning; William J Schultz
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1959-11-30
Filing date: 1959-11-30
Publication date: 1963-01-29
Anticipated expiration: 1980-01-29

Description

Jan. 29, 1963 R. M. MANNING ETAL ,0

DRAW BENCH LOADING MEASUREMENTS Filed Nov. 50, 1959 2 sheets -sheet 1 25 23 i3 7 4 24 2 2 VARIABLE-SPEED ll 2 I9 1 REVERSIBLE I 0.0 MOTOR 2 I8 20 ii [4 l2 6 33 [Q I v I 5 0c. INPUT 3 4 35 40 I8 32 A v RECTIFIER 5Q 30 3 8 52 A x x 40 Y Y 2 2 FIG I f V C! o 0.

(I L|J+ o T I? i g .IIXX w ,0 9.1 W (I 0 SPEED O)F DRAW F|G.2 62 M W INVENTORS RALPH M. MANNING BYWILLIAM J..SCHULTZ THElR ATTORNEY V Jan. 29, 1963 R. M. MANNING ETAL 3,075,636

DRAW BENCH LOADING MEASUREMENTS Filed Nov. 30, 1959 2 Sheets-Sheet 2 3O TACHOMETER GENERATOR SERVO MECHANISM INVENTORS RALPH M. MANNING BY WILLIAM J. SCHULTZ "MFFMLW THEIR ATTORNEY 3,h75,636 DRAW BENCH L UADENG MEAfiUEEMENTS Ralph M. Manning, Winchester, and William .li. Schultz,

Lynnfield, Mass, assignors to General Electric Company, a cerporation of New Yorlr Filed Nov. 30, 1959, Ser. No. 856,112 12 Claims. (Ci. Edd-3) This invention relates to draw benches of the type used to draw metal tubing or bars down to desired crosssectional dimensions, and more particularly, to an arrangernent for indicating and recording deviations from the maximum allowable loading or stress which may be exerted on the draw bench as a result of the drawing operation, and to a method for utilizing such deviations in the operation of a draw bench.

I has been found that mechanical overloading of draw benches can occur without electrical overloading of the draw bench electric drive motor. The loading and stresses exerted on a draw bench during a drawing operation varies both with the speed of the draw and the instantaneous power provided by the drive motor. In the absence of means to instantaneously coordinate the two variables, control of the draw bench in the past has been largely a matter of operator experience and judgment.

However, draw benches are frequently large and expensive pieces of equipment. For example, the draw bench to which the subject invention has been successfully applied utilized a 250 horsepower direct current motor with draw bench speeds of 80 feet per minute to 240 feet per minute. In one plant it was found that mechanical overloading of draw benches was found to cause frequent damage to the gearing and breakage of draw chains, and in one case a bench was actually pulled oif the factory floor causing many thousands of dollars of damage to the bench, plus the loss of production during equipment downtime.

It is an object of this invention to provide an arrangement to instantaneously indicate mechanical overloads of a draw bench over a variable speed range.

it is a further object of this invention to provide an improved method of indicating and recording the times at which a draw bench is overloaded during operation.

it is yet another object of this invention to indicate and utilize deviations from the maximum allowable mechanical loading of a draw bench.

Other objects and advantages of the invention will be come apparent as the following description proceeds and the features of novelty which characterize the invention will be pointed out with particularity in the claims an nexed to and forming a part of this specification.

In accordance with one form of the invention, means are provided to produce an electrical signal which is proportional to the power applied to the draw bench, means are provided to produce an electrical signal proportional to the speed of movement of the draw bench, and means are provided for combining the electrical signals and indicating mechanical loading placed on the draw bench relative to the maximum allowable loading.

More particularly, an electrical signal is developed proportional to the electrical input of the motor driving the draw bench, and a tachometer generator is utilized to provide an electrical signal which is proportional to the speed of the draw bench. The two signals provide electric currents which are proportioned by adjusting means such that their eifects upon the indicating instrument are made equal and opposite for combinations of speed of the draw bench and the instantaneous power of the drive motor which result from a given loading on the draw bench. If the given loading is the maximum allowable, the electric instrument will indicate deviations of draw bench loading below or above the maximum allowable. In the preferred embodiment, the electric instrument is incorporated as part of a recorder to maintain a record of the bench loading.

For a better understanding of this invention, reference may be had to the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a schematic representation of a draw bench incorporating the invention;

FIG. 2 is a plot of the instantaneous draw bench drive motor power versus the speed of the draw illustrating the linear relationship of constant load curves which result;

FIG. 3 is a preferred embodiment of an instrument which combines the electrical signals representing the variables of FIG. 2 to provide a single indication of the deviation of the loading applied to the draw bench from the maximum allowable loading;

FIG. 4 illustrates relationships between the variables of FIG. 2 which are desirable in the instrument of FIG. 3;

FIG. 5 is an alternate embodiment of the instrument shown in FIG. 3;

FIG. 6 is an enlarged View of the die shown in FIG. 1; and

FIG. 7 is an alternate embodiment of the invention.

Referring to FIG. 1, a draw bench is illustrated schematically comprising a movable chassis or driven member I mounted on wheels 2 for linear movement along rails 3 and 4 an fastened to the draw chain 5 through connecting member 6.

The draw chain 5 moves between sprocket wheels 7 and 3 which along with rails 3 and i are securely fastened to the factory floor. One of the sprocket wheels 7 is rotatably driven by a direct current or DC. drive motor 18 through intermediate reduction gearing such as gears 11 and i2 and their associated shafts l3 and 1 respectively. Different speed ranges may be provided through use of change gears in the gearing. The speed and direction of travel of the chassis l for a given ratio of gears 11 and 12 are determined by the speed and direction of rotation of the motor iii. A direct current motor is utilized since the direction of rotation may be readily controlled through the polarity of the applied voltage and the speed of rotation may be varied through control of the magnitude of the field current.

The pipe, tubing, or bar 18 which is being drawn or reduced in cross section is drawn through die 19 to provide a bar of reduced diameter 18'. Die 19, as best shown in FIG. 6, is attached to the factory floor by support 2% and contains a tapered opening 21 through which the bar passes. The bar 18 is drawn through the opening 21 of the die by clamping one end 23 of the pipe to the clamp member 24 carried by a chassis 1 and moving the chassis away from the die in the direction indicated by the arrows of FIG. 1. In operation a continuous drawing process is accomplished by moving chassis 1 through control of motor 10 to the region of die 19, clamping the pipe 18' to clamp member 24 and propelling the chassis 1 along the rails 3 and d in the direction of the arrows until the stop or end of the rails 25 is reached. The clamp member 24 is then loosened, the chassis l is returned to the region of the die and the process repeated.

In order to appreciate the magnitude of the stresses involved in the drawing operation, it may be noted that a draw bench to which the subject invention has been applied provides pulls of up to 50,000 lbs. with a linear speed of draw or movement of chassis 1 being feet per minute to 240 feet per minute through field current control of a 250 horsepower motor.

To obtain maximum bench output the bench speed should be as rapid as possible, limited however by the aoreese loading capabilities of the draw bench. Draw speeds will therefore vary for different types of metals or metals havinng a variable range of alloys in accordance with manufacturing tolerances. Also, through use of a plurality of dies, a plurality of pipes are often drawn at the same time by a single bench. The mechanical stresses or loading imposed upon the draw bench are a function of both the speed of the draw and the power input to the draw bench delivered by the motor Jill. In practice, a draw bench operator has been guided by indications of draw bench speed or power input. However, because of the relatively fast and variable speeds of the draw, it has been found difficult and impractical for the operator to note and correlate one or more readings in order to determine if the maximum allowable loading of the draw bench were being exceeded. Also, it has been found that draw benches are often overloaded by an operator attempting to obtain maximum bench output.

In accordance with the present invention, electrical signals are developed which represent the speed of movement of the chassis 1 and the instantaneous power of the motor 10. The two signals are combined in an instrument to visually and/ or audibly indicate mechanical overloading of the draw bench.

An electrical signal proportional to the speed of the draw is obtained by coupling the rotor of a tachometer generator 30 to the shaft 31 of sprocket wheel 8. The tachometer generator provides the electrical signal indicated as YY in FIG. 1 which is proportional to the speed of rotation of shaft 31 which is in turn proportional to the speed of travel of the chassis 1.

An electrical signal representing the instantaneous power of the motor is obtained through use of a direct current transformer 32 associated with the D.C.

power input lines

33 and 34. In order to provide a pure DC. signal which may be readily combined with the D.C. voltage output provided by the tachometer generator 39, the output of the D.C. transformer 32 is fed throuugh rectifier 35 to provide an output XX which is proportional to the power of the motor 18. The voltages XX and YY provide currents I and l respectively, when applied in circuit with an indicating instrument.

It has been found that if the signal I representing the drive motor input power, is plotted against the signal I representing the speed of the draw, a linear plot results for constant mechanical stress on the draw bench as shown in FIG. 2.

This relationship is utilized in an instrument 40 for combining the current I and l A preferred embodiment of such an instrument is indicated schemactially in FIG. 3.

Referring to FIG. 3, the voltage XX is fed to a pair of series connected

stator windings

41 and 42 while the voltage YY is fed to a pair of series connected stator windings 43 and 4-4. A pair of rotor windings 45 and 4-6 are wound upon rotor 39 which carries pointer 47 to cooperate with scale 48 to indicate the angular deflection of the rotor windings. Spring 38 biases rotor 3? to a central position relative to scale 48. The

rotor windings

45 and 46 are electrically connected in series and energized by a D.C. voltage provided by rectifier 48'. The rectifier 48 is energized by an alternating current source 50 and the output thereof is controllable by current limiting resistor as. The

stator windings

41 and 42 and the polarity of the applied voltage XX is selected such that the rotational torque provided by the interaction of the magnetic fluxes provided by current flow through

windings

41, 42 and 45 is opposite to the rotational torque provided by the interaction of the magnetic fluxes between

windings

43, 44 and 46. The angular deflection of the

rotor windings

45 and 46 and therefore of the pointer 47 is determined by the difference in the torques provided by the current I and that provided by the current I FIG. 4 illustrates the desired relationship between the rotational torques provided in response to the currents I and I The torque versus current characteristic produced by the voltage YY may be adjusted by rheostat 52 connected in series with the tachometer generator 34) as shown in FIG. 1. t is desirable to adjust the two torque characteristics, so that they are mirror images of each other to make it possible to calibrate the instrument 49 to show the approximate amount of deviation from the maximum mechanical loading curve. The torque characteristics are made to be equal and opposite for all conditions of draw bench power and draw bench speed which combine to provide the maximum allowable draw bench mechanical loading, or some other given loading related thereto. Hence, an instrument such as a Zero center deflection instrument may be utilized to indicate the maximum allowable or safe mechanical load on the draw bench at the center position with deflections from the center position indicating loads which are below or above the maximum allowable.

The instrument as may then be used as an indication of how much additional stress can safely be put on the draw bench at any given time. The instrument 49 may conveniently comprise the deflection mechanism of a strip chart recorder to provide a record of the mechanical stresswhich has been applied to the draw bench during operation in addition to instantaneous loading indications. The strip chart recorder is indicated schematically as 43' in FIG. 1 with reference line 50 indicating the maximum safe mechanical loading of the draw bench. Contacts associated with the recorder can be utilized to energize an audible alarm when the maximum allowable loading is exceeded.

When the torque characteristic curves of FIG. 4 have been adjusted as described above, a given change in either the current input of the motor It or the speed of the carriage 1 of the draw bench will represent a definite change in the stress applied to the draw bench. An increase in the current input of motor 10 will produce an increase in instrument torque resulting from the increase of current I which tends to drive the instrument upscale while an increase in the speed of travel of the carriage 1 will provide an increase in current l which produces an increased torque which tends to drive the instrument downscale. Any time that the two torques are in balance, the draw bench will be operating at maximum capacity without overloading. If the speed of travel of the carriage 1 should increase without an increase of current being supplied to the motor 1f}, the instrument 40' will deflect downscale against the bias of spring 38 indicating that the mechanical load on the draw bench has been reduced. Conversely, if the speed of travel of the chassislshould decrease without a decrease in the current supplied to the motor 10, the instrument 40 will deflect upscale indicating an increase in load on the draw bench.

FIG. 5 illustrates an alternate embodiment of the instrument 49. Referring to FIG. 5, it will be seen that the

stators

55 and 56 comprise permanent magnets. The

rotor windings

57 and 58 are wound upon armature 54. The voltages YY and XX are connected to the moving

coil windings

57 and 58 and the poles of

stators

55 and 56 are arranged such that the torques developed between the interaction of the permanent magnet stators and the magnetic field provided by current flow through the

windings

58 and 57, respectively, tend to produce deflections in opposite directions in a manner similar to that described in connection with FIG. 3. The pointer 59 is attached to the armature 54 around which the

rotor windings

57 and 58 are wound and cooperates with scale 60 to indicate the mechanical loading of the draw bench relative to the maximum allowable loading 62. Spring 61 establishes the center position of pointer 59 in the absence of a net deflection torque.

While the subject arrangement has been shown in corn bination with direct current circuits, the invention can readily be applied to alternating current circuits.

FIG. 7 illustrates an alternate embodiment of the invention which enables the direct calibration of the indicator in the magnitude of the loading imposed upon the draw bench rather than an indication of the approximate magnitude of deviation item a predetermined or maximum allowable loading. To enable a direct calibration of the instrument it the product of the electrical signals In and IYY should be realized.

Referring to FIG. 7, it will be seen that the output YY of tachometer generator 3% is used to control the positioning of the wiper 65 of potentiometer 66 through the servo mechanism 57 which rotates the wiper an amount proportional to the voltage YY. A battery 68 is connected across the potentiometer 66 and the voltage YY provided between one end of the potentiometer 66 and the position of arm 65 relative to one end thereof is proportional to The voltage YY is used to energize the rotor 69 of the instrument Iii while the series connected

stator windings

71 and 72 of the instrument are energized by the voltage XX. The deflection of pointer '73 in response to the combined torque of I I I and I is indicated on scale 74 which may be directly calibrated in pounds loading of the draw bench.

However, it has been found that the arrangement shown in FIG. 7 is more expensive and complex than that of the previously described embodiments of the invention which indicate loading deviations above and below the maximum. Such indications have been found to be satisfactory, even though the relative magnitudes thereof are only approximate and may vary under certain conditions, since the maximum allowable loading is adjusted to be accurate over the range of operating conditions.

Therefore, while particular embodiments of the subject invention have been shown and described herein, they are in the nature of description rather than limitation, and it will occur to those skilled in the art that various changes, modifications, and combinations may be made within the province of the appended claims without departing either in spirit or scope from this invention in its broader aspects.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An instrument for indicating the mechanical loading of a draw bench of the type in which a driven member draws material through a die comprising: means to provide a first signal proportional to the speed of the driven member of the draw bench, means to provide a second signal proportional to the instantaneous power of the means which drive said driven member, means to combine said first and second signals, means to indicate the resultant of said combined signals, and means to adjust the relative efiects of said first and second signals upon said indicating means to provide the same indication for combinations of speed of the driven member and power of the drive means which result from a given loading on said draw bench, said given loading being related to the maximum allowable loading of said draw bench.

2. An instrument for indicating the mechanical loading of a draw bench of the type in which a member draws material through a die comprising: means to provide a first electrical signal proportional to the speed of the driven member of the draw bench, means to provide a second electrical signal proportional to the instantaneous power of the means which drive said driven member, means to combine said first and second electrical signals 6 and to indicate the resultant of said combination, and means to adjust the relative effects of said first and second electrical signals upon said indicating means to provide the same indication for combinations of speed of the driven member and power of the drive means which result from a given loading on said draw bench, said given loading being related to the maximum allowable loading of said draw bench.

3. An instrument for indicating the mechanical loading of a draw bench of the type in which a member driven by an electric motor draws material through a die comprising: means to provide a first electrical signal proportional to the speed of the driven member of the draw bench, means to provide a second electrical signal proportional to the electrical input of the motor which drives said driven member, means to combine said first and second electrical signals and to indicate the resultant of said combination, and means to adjust the relative eiiects of said first and second electrical signals upon said indicating means to provide the same indication for combinations of speed of the driven member and power of the drive means which result from a given loading on said draw bench, said given loading being related to the maximum allowable loading of said draw bench.

4. An instrument for indicating the mechanical loading of a draw bench of the type in which a driven member draws material through a die comprising: means to provide a first signal proportional to the speed of the driven member of the draw bench, means to provide a second electrical signal proportional to the instantaneous power of the means which drive said driven member, means to combine said first and second signals, and to indicate the resultant of said combination, and means to adjust the relative effects of said first and second signals upon said indicating means to provide effects which are equal and opposite for combinations of speed of the driven member and power of the drive means which result from a given loading on said draw bench, said adjustment providing an indication of a loading which is releated to the maximum allowable loading of said draw bench.

5. An instrument for indicating the mechanical loading of a draw bench of the type in which a member driven by an electric motor draws material through a die comprising: a tachometer generator to provide a first electrical signal proportional to the speed of the driven member of the draw bench, means to provide a second electrical signal proportional to the electrical input of the motor which drives said driven member, means to produce and combine torques which are proportional to said first and second electrical signals and to indicate the difference therebetween, and means to adjust the relative effects of said first and second electrical signals upon said indicating means to provide torques which are equal and opposite for combinations of speed of the driven member and power of the drive means which result from a given loading on said draw bench, said given loading being related to the maximum allowable loading of said draw bench, said indicating means indicating draw bench loadings above and below said maximum allowable loading.

6. An instrument for indicating the mechanical loading of a draw bench of the type in which a driven member of the draw bench draws material through a die comprising: means to provide a first signal proportional to the speed of the driven member of the draw bench, means to provide a second signal proportional to the instantaneous power of the means which drive said driven member, means to provide a third signal which is the reciprocal of one of said first mentioned signals, means to combine said third signal and the other of said first mentioned signals and to indicate the product thereof, said indicating means being calibrated to provide indications of the mechanical loading of said draw bench.

7. A method of providing material of a desired cross section comprising: passing a portion of material of a cross section greater than that desired through a fixed die a 7 of the desired cross section, securing a movable member to the said portion, driving the said movable member away from said die by driving means, deriving a first signal representing the speed of said movable member relative to said fixed die, deriving a second signal representing the power input to said driving means, combining the efiects of said first and second signal and indicating the resultant thereof, and controlling the speed of said movable member in accordance with the indication of the combined efiects of said signals.

8. A method of drawing a material to a desired cross section through a fixed die without exceeding the maximum allowable loading of the draw bench comprising: securing a movable member to the material being drawn, drawing the movable member away from the fixed die by a driven member, deriving a first electrical signal proportional to the speed of said driven member, deriving a second electrical signal proportional to the instantaneous power of the means which drive said drive member, combining said first and second signals and indicating the resultant thereof, adjusting the relative effects of the first and second signals to provide the same indication for combinations of speed of the driven member and power of the drive means which result from a given loading on the draw bench and which is related to the maximum allowable loading on the draw bench, and controlling the speed of said driven member in accordance with said indications.

9. A method of drawing a material to a desired cross section through a fixed die without exceeding the maximum allowable loading of the draw bench comprising: securing a movable member to the material being drawn, drawing the movable member away from the fixed die by a member driven by an electric motor, deriving a first electrical signal proportional to the speed of said driven member, deriving a second electrical signal proportional to the electrical input of the motor which drives said driven member, combining said first and second signals and indicating the resultant thereof, adjusting the relative effects of the first and second signals to provide a predetermined indication for combinations of speed of the driven member and power of the drive means which result from a given loading on the draw bench and which is related to the maximum allowable loading on the draw bench, and controlling the speed of said driven member in accordance with said indications.

10. A method of drawing a material to a desired cross ection through a fixed die without exceeding the maximum allowable loading of the draw bench comprising: securing a movable member to the material being drawn, drawing the movable member away from the fixed die by a driven member, deriving a first electrical signal proportional to the speed of said driven member, deriving a sec- 3 end electrical signal proportional to the instantaneous power of the means which drive said driven member, combining said first and second signals and indicating the resultant thereof, adjusting the relative effects of the first and second signals upon the indicator to provide effects which are equal and opposite for combinations of speed of the driven member and power of the drive means which result from a given loading on the draw bench and which are related to the maximum allowable loading on the draw bench, and controlling the speed of said driven member in accordance with said indications.

11. A method of drawing a material to a desired cross section through a fixed die without exceeding the maximum allowable loading of the draw bench comprising: securing a movable member to the material being drawn, drawing the movable member away from the die by a member driven by an electric motor, deriving a first electrical signal by a tachometer generator proportional to the speed of said driven member, deriving a second electrical signal proportional to the electrical input of the motor which drives said driven member, providing and cornbinin torques which are proportional to said first and second signals and indicating the difierence therebetween, adjusting the relative effects of the first and second signals upon said indicating mean to provide torques which are equal and opposite for combinations of speed of the driven member and power of the drive means which result from a given loading on the draw bench to indicate draw bench loading above and below the maximum allowable loading, and controlling the speed of said driven member in accordance with said indications.

12. A method of drawing a material to a desired cross section through a fixed die without exceeding the maximum allowable loading of the draw bench comprising: securing a movable member to the material being drawn, drawing the movable member away from the fixed die by a driven member, deriving a first electrical signal proportional to the speed of said driven member, deriving a second electrical signai proportional to the instantaneous power of the means which drive said member, deriving a third signal which is the reciprocal of one of said firstmentioned signals, combining said third signal with the other of said first-mentioned signals and indicating the product thereof, and controlling the speed of said driven member in accordance with said indications.

References Cited in the file of this patent UNITED STATES PATENTS 2,452,244 Knudsen Get. 26, 1948 2,602,538 Bimba et al. July 8, 1952 2,640,352 Ellison et al. June 2, 1953 2,886,170 Kerr May 12, 1959

Claims

1. AN INSTRUMENT FOR INDICATING THE MECHANICAL LOADING OF A DRAW BENCH OF THE TYPE IN WHICH A DRIVEN MEMBER DRAWS MATERIAL THROUGH A DIE COMPRISING: MEANS TO PROVIDE A FIRST SIGNAL PROPORTIONAL TO THE SPEED OF THE DRIVEN MEMBER OF THE DRAW BENCH, MEANS TO PROVIDE A SECOND SIGNAL PROPORTIONAL TO THE INSTANTANEOUS POWER OF THE MEANS WHICH DRIVE SAID DRIVEN MEMBER, MEANS TO COMBINE SAID FIRST AND SECOND SIGNALS, MEANS TO INDICATE THE RESULTANT OF SAID COMBINED SIGNALS, AND MEANS TO ADJUST THE RELATIVE EFFECTS OF SAID FIRST AND SECOND SIGNALS UPON SAID INDICATING MEANS TO PROVIDE THE SAME INDICATION FOR COMBINATIONS OF SPEED OF THE DRIVEN MEMBER AND POWER OF THE DRIVE MEANS WHICH RESULT FROM A GIVEN LOADING ON