US 3833932 A
A system for use with cranes which have booms that may be varied in length and angular relationship which continuously displays the operating radius and provides for a display of the boom length by pressing a button and which provides alarms to the operator for both radius and length of boom.
Description (OCR text may contain errors)
United States Patent Hamilton Sept. 3, 1974  B OM LEN TH OPERATING RADIUS 3,269,560 8/1966 Knight 212/39 R INDICATOR AND WARNING DEVICE 3,489,294 l/l970 Greb et al..... 340/267 C 3,549,876 12/1970 Hamilton 340/267 c Martin W. Hamilton, Arlington Heights, Ill.
Eaton Corporation, Cleveland, Ohio Oct. 12, 1972 Inventor:
US. Cl. 340/267 C, 212/39 A Int. Cl G08b 21/00, B66c 15/00 Field of Search 340/267 C; 212/39 A, 39' R Mason 340/267 C 57] ABSTRACT A system for use with cranes which have booms that may be varied in length and angular relationship which continuously displays the operating radius and provides for a display of the boom length by pressing a button and which provides alarms to the operator for both radius and length of boom.
2 Claims, 3 Drawing Figures Fl-T' P 24 33 27 r paws/2 Kg 25 SW/TQI/ wane: wn/e2 D/FE AMP 1. Field of the Invention This invention relatesin general to indicating and warning systems for cranes and in particular to indicator and warning systems which continuously indicate the operating radius of the boom and the length of the boom.
2. Description of the Prior Art Prior systems have been developed which include load cells for monitoring the crane load and transducers for monitoring the angle of the boom and produce a warning when preset maximum criteria are exceeded.
SUMMARY OF THE INVENTION The present invention comprises a computer which continuously solves the equation for the operating radius of the crane based on the angle of the boom and the length of the boom as well as the offset from the pivot point of the boom relative to the vertical pivot point of the crane. The cosine of the angle of the boom is obtained from an angle potentiometerof the type controlled by a pendulum which drives a cosine potentiometer to produce an output of the cosine of the boom angle-A boom length transducer produces an output which continually monitors the length of the boom and the lengthof the boom signal is combined with the cosine 0 signal. The operating radius of the boom is continuously indicated by a meterand an alarm system receives inputs so as to produce alarms under conditions which are deemed dangerous. Switching means are provided so as to convert the radius indication to a length of boom readout when desired.
BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and advantages of the invention will be readily apparent from the following description of certain preferred embodiments thereof taken in conjunction with the accompanying drawings although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure and in which:
FIG. 1 is a side view of the crane with the system of the invention installed;
FIG. 2 is a schematic diagram of the indicating and warning system of the invention; and
FIG. 3 illustrates the relationships of the boom angle and length to the crane pivot point.
DESCRIPTION or THE PREFERRED EMBODIMENTS FIG. 1 is a view of a crane which is mounted on a truck bed 8 such that the crane pivots about a vertical pivot axis 9. The boom 11 is extensible and pivotable about a horizontal axis. The hook 12 is mounted at the end of boom for supporting loads.
As shown in FIG. 3, the operating radius R of the crane is the distance from the vertical pivot axis 9 to the projection on the horizontal plane of the end of the crane beneath the hook 12. The distance K is the offset from the vertical pivot axis 9 and the horizontal pivot axis of the crane and can be or depending upon the relationship of the crane relative to the vertical pivot axis 9. The length of the boom is indicated as L and the 2 crane angle is indicated by the angle 0. The operating radius R is equal to (L cos. 6) K, where R is the operating radius in feet measured from the center rotation of the cab. horizontally to the hook. K is the boom pivot to cab pivot distance which is a constant for any given machine.
The boom 11 has mounted therein a boom length transducer 14 and an angle potentiometer 13 which may be a pendulum controlled device.
FIG. '2 is a schematic view of the indicating and warn- I ing system of this invention. The cosine angle potentiometer 13. has one side connected to ground and includes a winding R and a wiper contact 18 which is controlled by a pendulum 19- so. as to produce an output equal to the cosine 0. The ungrounded side of winding R is connected to one end of a variable resistor R for calibrating purposes which has its other side connected to terminal 16 that is connected to a suitable B+ supply. A switch S normally engages contact 15 which is connected to wiper contact 18 but can be moved to engage contact 17 which is. connected to the junction point between resistors R and R A voltage follower circuit 21 is connected to switch S and has an output terminal connected to one end of. the length potentiometer 14. indicated as R in FIG. 2. The other end of the length potentiometer R is connected to one end of a resistor R which is a calibrating resistor which'has its other end connected to ground. A wiper contact 20 moves in-response to the variation in the length of the boom ll and supplies aninput to a-voltage follower 22. The calibrating resistor R is also connected to the output of the voltage follower 21 and has its other side connected to an alarm switch for setting the length alarm which is designated as R The other side of resistor R is connected to ground. A wiper contact 29 engages resistor and supplies an input to a differential amplifier 2,4 which also receives an input from wiper contact 20. A terminal 25 is connected to 8+ and has its other side connected to' acalibrating resistor R which has its other side connected to a resistor R form,- ing a potentiometer which has its other side connected to ground. A wiper contact 28 allows the radius alarm end of a resistor R which has its other end connected to a calibrating resistor R whose other side is connected to a radius-length meter 31. A condenser C is connected from a junction point between resistors R and R and ground. Switch S normally engages contact 32 at the junction point between resistor R and meter 31 and is movable to engage an open circuit 4 contact 33. A resistor R is connected to switch contact S and has its other side connected to wiper contact 36 which engages a slide resistor R The contact 36 allows the boom pivot to cab pivot distance to be set into the computer. One end of the resistor R is connected to resistor R which has its opposite side grounded. A resistor R is connected to the other end of resistor R and has its other side connected to terminal 34 which is connected to B+.
A gate circuit 26 receives inputs from the differential amplifiers 23 and 24 and has an output terminal 37 which is normally engaged by switch 5 which is movable to engage an open circuit contact 38. A power 3 switch 27 receives an input from switch S and supplies an output to an alarm 28 which might be an audible alarm and which has its other side connected to ground and to a visible alarm 29 which might be a light, which has its opposite side connected to ground.
A push botton 41 is connected by mechanical linkages 42, 43 and 44 to the switches S S and 8;, so as to move them from their normal position as shown in FIG. 2 to their second positions wherein the switch S engages contact 17, switch S engages contact 33, and the switch S engages contact 38.
In operation, the circuitry of FIG. 2 comprises a simple analog computer for solving the equation R L cos.0+ K. The output of the voltage follower 21 consists of a signal cos.6 when switch S engages wiper contact 18. The signal is supplied to one end of resistor R and the signal on wiper contact 20 is equal to L cos.0. This signal is equal to the actual radius of the boom 11 rather than the operating radius R and is fed to the meter 31 through the voltage follower operational amplifier 22 which is offset by the constant current sources R and R to provide the value K in the computer. Value K is the boom pivot to cab pivot distance and is a constant for any machine and once set need not be further adjusted for any particular crane. The meter 31 will continuously read the operating radius R as the length and the angle of the boom 1 1 is varied by the operator.
If it is desired to obtain a readout of the length of the boom the push button switch 41 is depressed thus moving the switches S S and S to respectively engage contacts 17, 33 and 38, and the meter 31 will provide a direct readout of the length of the boom. This is because when switch S is moved to engage contact 17, the cos. 6 from the cosine potentiometer 13 is equal to 1 and K is equal to because switch S has been opened thus removing the K offset to the meter 31. It is to be realized, of course, that the meter 31 should be calibrated in the same units for both radius and length as, for example, feet.
When the push button 41 is released, the switches S S and S return to the position shown in FIG. 2 so that the meter 31 again reads operating radius.
The alarm circuits may be digital type circuits as, for example, to provide direct reading and alarm settings. The radius alarm is set by the wiper contact 28 and the calibration resistor R so that the gate 26 will energize the power switch 27 to turn on the alarms 28- and 29 if the operating radius exceeds the preset limit.
The length alarm is established by the wiper contact 29 which receives a signal proportional to the L cos 6 from which is substracted in the differential amplifier 24 L cos Osignal. The outputs of the amplifiers 23 and 24 are both supplied to the gate circuit 26 such that the alarms 28 and 29 will be energized in the event either or both of the operating radius or length maximums are exceeded. 1
It is seen that this invention continuously monitors the operating radius and indicates to an operator the operating radius. The computer will also indicate the length of the boom when the switches S S and S are energized by the push button 41 and thus the operator can continually monitor the operating radius and observe the boom length by merely pushing the push button 41.
Although the invention has been described with respect to preferred embodiments it is not to be so limited as changes and modifications may be made which are within the full intended scope as defined by the appended claims.
1. An operating radius and length indicator for a crane having an adjustable angle and length boom comprising: first means mounted on the boom for producing a signal cos 0 proportional to the cosine of the angle of the boom relative to the horizontal; and second means variable "in response to the length of the boom receiving the output of said first means to produce a signal L cos 0 proportional to the length of the projection of the boom on the horizontal plane, means for setting a first threshold representation of a maximum L cos 0 signal, a first differential amplifier receiving said L cos 0 from said second means and a signal maximum L cos 0 signal from said first threshold means, means for setting a second threshold corresponding to a maximum length of the boom, a second differential amplifier receiving signals from said second means and said means for setting said second threshold; a gate receiving the outputs of said first and second differential amplifiers, and an alarm connected to the output of said gate such that an alarm is given if either threshold is reached.
2. An operating radius and length indicator for a crane according to claim 1 including first, second, and third switches with the first switch connected to said first means for producing said cos 6 signal to convert its output to one and wherein said boom is supported by a horizontal pivot axis from a cab which is rotatable about a vertical axis of said crane, means producing a signal K proportional to the horizontal offset distance from said vertical axis to said horizontal pivot axis and an indicator means receiving'inputs from said means producing said K signal and said second means producing said fL cos 6 signal to produce an indication of theoperating radius, said second switch connected between said indicator and said means proproduces an indication of boom length.