Crane Load And Radius Indicating System

Abstract

Separate modular units, including a main tensiometer, a boom angle transducer, a control logic module, a combined boom radius readout and a degree of safe load meter unit, and combined actual load and allowable load readout unit, are operatively connected to a boom-type crane. The units are electrically interconnected by suitable cables that are shielded and insulated from the crane. The control logic module contains a transistorized solid-state circuit that receives, amplifies, and converts analog signals from the boom angle transducer and from a selected one of the tensiometer units, to corresponding digital signals that are continuously and automatically processed with data read from a selected memory module in which information based on the configuration of the crane in use is stored. Digital signals are produced for use in operating the digital radius readout, the allowable load readout, and the actual load readout, respectively, as well as digital signals corresponding to the ratio of the allowable loads. The resulting digital safe load signals are then converted to corresponding analog signals for use in operating the degree of safe load meter.

Description

BACKGROUND OF THE INVENTION

In the operation of heavy cranes, a substantial number of serious accidents occur through the hoisting of large weights and changing the boom angle. As the angle subtended between the horizontal surface on which the crane rests and the boom is decreased, the moment of force exerted on the crane by the boom increases, thereby increasing the tendency of the crane to tip over. Thus, a very real need exists for clear and accurate information being readily provided to the crane operator, which will improve his ability to operate the crane. Such information must be calculated from data based on the geometrical configuation of the particular crane in use, as well as on the relative weight of the load and boom angle existing at the time the desired information is provided.

Of primary interest to the crane operator for safe operation of the crane, in addition to the radius of the load, is an indication of the percent of safe load at which he is operating his crane. Such percent of safe load and boom radius change, as the boom moves upwardly and downwardly in handling each load, requires almost instant calculation which is continuous as the crane operates.

Various safety factors are required by legal regulations for the cable, boom, and sheaves used in crane hoist apparatus. Also, visual and audible warnings are necessary to assist the operator in safely operating his crane. But mainly, the crane operator needs accurate and continuous information relating to the vital conditions affecting safe crane operation, before safe limits are exceeded, i.e., before such warnings actually go into operation, or as the unsafe conditions bringing about such warnings are approached. In cable load carrying boom types of cranes, the geometry of the crane configuration requires automatic trigonometric calculations for the percent safe load and load radius, which are varying functions of the boom angle which change as the load is handled. Also, the parameter configuration data for such calculations must always be taken into consideration in the processing thereof for each crane, and this varies with different crane manufacturer's specifications.

Thus, the desired information must be based on data which conforms to the configuration of the crane in use. It is desirable to provide a modular system which can be adapted for use with any desired one of a plurality of different presently available crane configurations. In accordance with the present invention, this is accomplished by a universally applicable system which can be preset manually and equipped with a selected memory module such that the system is automatically programmed to handle the configuration of any boom type of crane that is presently on the market.

There is also a present great need for a universal system having modular units that can be made in production, with each suitable for use with any known boom type of crane. This is accomplished by the present system which comprises, in addition to several sensors, a programmable logic and control unit, and at least one display unit, that are easily mounted on the crane with which the system is to be used.

The use and handling of as few analog components as possible is also highly desirable in systems that are exposed to severe weather and operating conditions, since they are subject to error and drifting due to wide variations in heat, cold, and age. The maximum use of digital type equipment is a feature of the present invention, along with the use of a minimal amount of analog equipment, as only the boom angle, load, and percent safe load indicator units use analog signal circuits.

SUMMARY OF THE INVENTION

In accordance with illustrative embodiments demonstrating features and advantages of the present invention, there is provided sensor instruments for continuously monitoring the actual load and angle of a boom. Signals are transmitted therefrom to a control and logic unit having an transistorized, solid state electronic circuit means which automatically computes the required digital data, including output signals for operating large, brightly illuminated indicators for use by the operator of the crane. There is provided a bold-faced percent of safe load meter, and a large, digital display unit for showing the actual load radius. Other safety features including a digital display of the actual and allowable loads, and suitable, audible and visual warning signals are also provided.

The electronic system converts analog signals, which are proportional to selected crane operating parameters, into digital and analog displays in the crane cab. The information thus displayed in the crane cab is used by the operator as an operational aid, such that he is able to determine the degree of how close the crane may be to maximum load as a percent of safe load indication, the actual load, the allowable load as a function of boom length and load radius, and the actual operating radius.

BRIEF DESCRIPTION OF THE DRAWINGS

The above brief description, as well as further objects, features, and advantages of the present invention will be more fully appreciated by reference to the following detailed description of a presently preferred but nonetheless illustrative embodiment in accordance with the present invention, when taken in connection with the accompanying drawings wherein:

FIG. 1 is a elevational view of a load handling boom type crane equipped with a modular safe load information indicating system of the present invention;

FIG. 2 is a circuit block diagram of the modular safe load information indicating system, with the broken lines indicating the connection to the crane of FIG. 1;

FIG. 3 is an elevational view of the control and logic circuit unit;

FIG. 4 is an elevational view of the percent safe load indicator and digital radius display unit;

FIG. 5 is an elevational view of the boom angle transducer unit;

FIG. 6 is a block diagram of the boom angle load radius circuit;

FIG. 7 is a circuit diagram of the bridge circuit of a load line tensiometer;

FIG. 8 is a block diagram of the percent of safe load to allowable load circuit of the control logic unit;

FIG. 9 is a circuit and block diagram of the line tensiometer and actual load circuit;

FIG. 10 is an elevational view of the allowable and actual load display unit;

FIG. 11 is a perspective view of a memory module; and

FIG. 12 is an elevational view showing the basic gemoetry involved in the operation of a crane.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 1, there is shown a load-hoisting crane 10, which includes a tractor 12 on which a cab housing 14 is mounted for horizontal rotation about a vertical axis 16 by suitable power means including a large annular drive gear 18. A boom 20 is pivoted to the front of housing 14 at 22, for movement thereabout upwardly and downwardly in a vertical plane as the crane is operated. A jib 24 is similarly pivoted at 26, near the free end of the boom 20 and the jib 24 and boom 20 are provided with sheaves 28 and 30, respectively, near their free ends. The sheaves 28 and 30 are provided with load-carrying lines or cables 32 and 34 having load hooks 36 and 38 depending from the free ends of the jib 24 and boom 20, respectively.

Mounted in a convenient location on the boom 20 is a boom angle transducer unit 40 which is shown in FIG. 5. The transducer unit 40 is for continuously sensing the angle of the longitudinal axis of the boom with the horizontal axis of the crane 10 and supplying an analog output signal corresponding to such angle. Also, load handling cables 32 and 34 are provided with tensiometer units 42 and 43, respectively, the output signal of a selected one of which corresponds to the weight of the load on hook 36 or hook 38, as the case may be. Located in housing 14 is a cab 46 for the operator of crane 10, and conveniently mounted in front of such operator is a safe load information indicator and digital display unit 48, which is shown in FIG. 4. Also mounted on a side wall of cab 46 is a control and logic module unit 50, which is shown in FIG. 3. The logic module 50 is for calculating the desired safety information from storage data based on crane configuration in conjunction with those provided by signals from manual sets and the angle transducer output and a selected one of the cable tensiometers, for automatically controlling the display unit 48.

To summarize, the system per se comprises the combination of line tension transducers or sensors 42, 43, boom angle transducer or sensor 40, control and logic module unit 50, and operator display unit 48 for continuously indicating safe load and radius conditions occurring while the crane is in operation. An auxiliary readout unit 51, as shown in FIG. 10, is also provided. Such auxiliary readout unit 51 can be mounted in cab 46 adjacent to the unit 48, and is provided with a digital readout or display 80 of the allowable load, and a similar display 96 of the actual load being handled by the selected load line in pounds.

Referring to FIG. 4, the percent safe load and radius indicator unit 48, is provided with a digital display or readout 68 of the load radius in feet, and a bold-faced meter 102 having a rotary moving hand or pointer 100 for continuously indicating on an arcuate dial 104, the percent of safe load being handled as the crane 10 is operated. The front of the unit 48 is also provided with a rotary knob 231 adapted to be manually adjusted to any selected one of four stations 234, 236, 238 and 240 corresponding to Lamp Test, Main Line, Jib/Whip Line, and "OFF" switch positions. As the pointer 100 of indicator 102 approaches unsafe load conditions for the crane 10, the corresponding dial warning area 244 is colored yellow and the dial danger area 246 is colored red in the area of danger.

As shown in FIG. 6, signals from the boom angle transducer unit 40 go through shielded circuit 52 to a solid-state amplifier circuit 54 then to an analog-to-digital converter network 56. A cosine (COS) read-only-memory (ROM) circuit 58, programmed with the cosine of 0 to 90 degrees in discrete increments, receives digital output signals from the converter 56, and produces a digital output signal proportional to the cosine of the operating boom angle. The signal is then multiplied in a solid-state multiplier (X) circuit 60, by a second digital signal from circuit 62, that is manually set by means of knob 232 (FIG. 3), to be directly proportional to the actual length of the boom 20 (FIG. 1), thereby producing a digital output signal which is proportional to the load radius in a horizontal plane. The resulting signal is corrected in an additive circuit 64 by the adding from circuit 66, a signal proportional to a constant C, FIG. 1, proportional to the radius of rotation of pivot 22 about the center line 16. This results in a digital output signal representing the actual working load radius, which controls the digital radius display 68 comprising convenient units of length, such as feet.

As shown in FIG. 2 the digital output signal of A/D converter 56 is also applied to a load read-only memory (ROM) circuit 70 via circuit 76. The output of the load ROM memory circuit is supplied to a solid-state comparator circuit 74 by a connecting circuit 77. As shown in FIG. 2, the comparator circuit 74 is provided with a manual load set input circuit 78, which is controlled by the thumb set 230. The resulting output signal of the comparator circuit 74 of FIG. 2 is applied to the input of an allowable load digital display circuit 80 by a circuit 82, as well as to a solid-state dividing (.div.) circuit 84 by a circuit 86. The dividing circuit 84 also receives a digital load signal from the line tensiometer unit 43, for example, by way of shielded cable circuit 87, amplifier (G) circuit 88, converter 90, and multiplier (X) circuit 92, and lead 94. A manually operated jib selector switch 89, (FIG. 3), is used to select the tensiometer 42 in the whip/jib line 32 when the latter is in use. A branch 96, (FIG. 2), of lead 94 also carries the digital output signal of the multiplier circuit 92 to an actual load display circuit 96.

The dividing circuit 84 computes the percentage relationship of the allowable load signal from comparator circuit 74 with respect to the digital load signal from multiplier circuit 92; and the digital percent of safe load signal output then is converted in a solid-state digital/analog (D/A) circuit 98 for moving the pointer 100 of the percent safe load meter 102 over an arcuate dial 104 calibrated in percentages (0 to 120%).

As shown in FIG. 6, the boom angle transducer unit 40 comprises a pendulum 106 driven potentiometer 108 mounted directly on the boom 20 of the crane 10. The transducer 40, is designed to provide a zero output at zero degree boom angle, as measured from the horizontal, and an increasing output signal as the boom is moved toward vertical position. The pendulum 106, used to drive a potentiometer contact slide 110, provides a minimum sensitivity of 0.35.degree.. Thus, an incremental change in angle of the boom as small as 20 minutes is detected with a corresponding output signal change to the control and logic module. Such high degree of sensitivity is provided for dealing with relatively long boom lengths operating at or near maximum boom angles.

The analog input signal from the boom angle transducer 40 is transmitted to the control and logic module 50 of FIG. 3, where it is automatically processed as shown in FIG. 6. Both terminals 112, 114 of the potentiometer 108 in the boom angle transducer are connected directly to a temperature stable .+-.12 volt DC power supply 116 (which, in turn, may be powered by the 24v battery, not shown). One terminal 114 is connected to +12 vdc and the other terminal 112 is connected to -12 vdc thereof. The potentiometer slide 110 has a total travel of 340.degree. proportional to -12 to +12 vdc. Inasmuch as the transducer 40 only operates over a 90.degree. arc, the voltage span is approximately 6.4 volts, for zero vdc output at zero degree boom angle, and 90/340x(+24vdc), or +6.35 vdc output signal at 90.degree. rotation.

The analog signal from the boom angle transducer 40 is cabled by circuit 52 to the control and logic module 50 of FIG. 3, where it is internally connected as the analog input signal to the buffer (BA--1) amplifier 154, of FIG. 6. The circuit 52 contains a suitable resistor 118 and is grounded at 120 through a capacitor 122. An adjustable feed-back gain control circuit 124 is also provided for the buffering amplifier 154, comprising parallel connected capacitor 126 and resistor 128, and an adjustable resistor 130, a terminal of which is grounded at 132. The buffered-amplified signal output of amplifier 154 is conducted by circuit 134 to an 8 bit A/D (analog to digital converter) solid-state network 56 wherein a digital signal proportional to boom angle is developed. The digital signal from the A/D network 56 is used to address the selectively programmable read-only memory circuit 58 which has been previously programmed with the cosine of 0.degree. to 90.degree. in 256 increments. The output of the A/D network 56 is also used to address via circuit 76 programmed "load" tables as will be hereinafter described.

The output signal from the COS ROM circuit 58 is a digital signal proportional to the cosine of the boom angle. This signal is multiplied in circuit 60 by a second digital signal from circuit 62, which is directly proportional to the length of the boom in use. The resulting digital signal is now proportional to the radius of the boom along the horizontal and is applied to a summation calculating circuit 64. By adding or subtracting, depending on the crane design, a digital signal is generated through circuit 66 proportional to the distance C between the boom pivot pin and the center of rotation of the crane, and a digital signal is calculated by circuit 64 which represents the true "load radius." This signal is conducted by cable 136, (FIG. 6), to multiplex circuit 138 wherein the signal is multiplexed (the "load radius" signal represents a three digit number) and cabled to the operator display unit 68 where it is demultiplexed by circuit 140 into three separate digital signals. The three signals are individually connected to standard "latch" and decoder/driver circuit 142 and 144. The output of the decoder/drivers are connected to the "radius" display which comprises three separate seven segment BCD display units.

Considering only the main line load transducer 43 of FIG. 1 (the fast or whip line transducer 42 functions essentially in the same manner), the output thereof is an analog signal directly proportional to load. As shown in FIG. 7, the load transducer 42 comprises a load cell 146 in the line carrying the hook for the load being hoisted. An excitation voltage from a suitable source is applied across the tensiometer, comprising strain responsive metal alloy resistors 147 arranged to form a Wheatstone Bridge circuit at terminals 148, 150 thereof. The load transducer 42 is operatively connected to the cable, such that the load on the cable is transmitted to load cell 146. The load cell 146 thus produces an output voltage between voltage leads 152 and 154 in cable 87, that is directly proportional to the load line tension which is in turn directly proportional to the load being carried by the hook thereon. The excitation voltage is provided by an adjustable voltage source 156 connected across the terminals 148, 150.

As shown in FIG. 9, the signal from the load transducer tensiometer 146 is connected by shielded cable 87 to the control and logic module where it is internally connected as the input of load amplifier LA-1 circuit 160. The analog output signal from the load transducer 146 is linear with applied load. However, the magnitude of such signal can be varied by adjusting the excitation voltage from source 156. Therefore, dispensed with is any discussion on actual signal levels.

Amplifier LA-1 circuit 160 is provided with a DC power circuit +V, -V and with a gain control feed back circuit 161 connected to input lead of LA-1 and to a manually adjustable contact slide 165 of a potentiometer 167 that is in turn connected to the output circuit 164 through a resistor 169 and to ground at 171. Lead 158 is provided with a resistor 173 and a ground circuit 175 containing parallel connected resistor component 177 and capacitor component 179. The gain of amplifier 160 is selected such that at maximum line tension a 10 vdc signal is developed at the input of A/D converter 162 via lead 164. The A/D converter 162 is weighted such that the maximum load is broken down into 1024 increments (10 bits).

To obtain the hook load with which the operator is most interested, it is necessary to multiply the line tension developed by the tensiometer by the parts of lines (number of lines with which the block is rigged). This is provided by a manually set (parts of line) circuit 166, and multiplier (X) circuit 92 into which the digital signals to be multiplied are fed through leads 170 and 172.

The signal from multiplier (X) circuit 92 is then applied through a connecting circuit 174 to a multiplexer circuit 176, and such multiplexer signal is then transmitted via cable 178 to the digital display 96 of unit 51 of FIG. 10, where it is demultiplexed by circuit 180 into six separate signals. Each of these signals is in turn connected to a corresponding latch 182, decoder/driver 184 and finally into an individual seven-segment digital readout 96 to display the "actual load" to the operator in large illuminated digits. The signal "B" from the multiplier 92 is also used as an input to divider circuit 84 for eventual use by the "percent safe load" circuit 102 via lead 94 of FIG. 8.

As shown in FIG. 8, signal "A" which is proportional to boom angle, is used by way of lead 76 to address a previously programmed table 188 of load ROMS 70. Each load ROM circuit 70 is programmed to contain the crane manufacturer's load table for a specific crane configuration (i.e., boom length, counterweight, crawler position, etc.). The output of the selected load ROM circuit 70 is a digital signal proportional to allowable load. This signal and a signal from the manual load limit set circuit 190 are fed, via circuits 77 and 78, into the comparator circuit 74 which for safety automatically selects the lower signal. Such lower signal is then used in the divider network 84 as the divisor and in the allowable load display 80. The dividend, Signal "B," is proportional to hook load. Therefore, dividing the hook load by allowable load, a digital signal is obtained that is proportional to percent of safe load. This signal is next processed through the digital to analog D/C converter 98 and converted into an equivalent analog voltage which is then displayed directly by the "percent of safe load" meter 102.

The digital "allowable load" signal is processed in a manner similar to the "Actual Load" signal and displayed digitally to the crane operator by display 80. Such processing is accomplished by the automatic operation of multiplexer circuit 192 having an input circuit 194. The output of the circuit 192 is applied to demultiplexer circuit 196 to latch circuit 198, then to decoder/driver 200, and finally to the digital allowable load display 80.

The above description has dealt primarily with main line loads such that the radius displays the radius to the load suspended by the main line. Similarly, the "allowable loads" previously discussed are those that relate to the main line. However, the present system also provides "load" and "radius" information to the operator when using the fast or whip line 32 of FIG. 1. This is accomplished by programming into the memory bank 70, of FIG. 8, the safe or allowable data, as published or otherwise provided by the crane manufacturer. Boom angle offset information is likewise programmed into the memory bank 70, thus allowing the system to generate accurate load radius information when operating from the jib or whip line.

The importance of taking into account offset angles in the operation is shown in FIG. 12. The use of imaginary boom length BL equal to the distance between the boom pivot pin 22 and the point 201 of intersection of a line 202 drawn vertically through the jib sheave 28 and a line 204 extending from the centerline CL of the boom 20, would not require dealing with equivalent boom length and boom offset angles. However, on further investigation it becomes apparent that the imaginary boom length BL soon approaches an infinite length as the boom angle .theta.1, approaches 90.degree. and the line 202 drawn vertically through the jib sheave 28 would not intersect the line 204 extending outwardly from the boom 20.

The present system takes into account the complex trigonometry involved when the jib 24 and whip line or cable 32 are being used for handling loads carried by hook 36. This is accomplished by developing an equivalent boom length BLEQ, of FIG. 12 and a corresponding boom angle offset .theta.2. The system is programmed to automatically calculate the difference between such boom angle .theta.1 and boom angle offset .theta.2, and then process such data to thereby produce accurate load radius information to the operator. By virtue of the programming feature of the present system, these and similar difficult calculations are made almost instantaneously and with precise accuracy, even when the crane jib is being used.

Referring to FIG. 3, the front switch panel 206 of the control/logic unit 50, which is preferably mounted on an inner wall of the cab of the crane 10 within easy reach of the operator, is provided with separate knobs 210, 212, 213 and 214 for adjusting corresponding potentiometers for calibrating and zero setting of signal circuits corresponding to the main load and jib/whip lines. Test jacks 216, 218, 220 and 222 are provided in the panel for checking the main line, jib/whip line, common ground, and boom angle circuits, respectively. A safety fuse 224 is located at one side of a manually adjustable drum type thumb set 226 for adjusting the parts of line involved in producing a corresponding digital signal input for the circuit 78 to the multiplier 92 of FIG. 2. To the right of such set 226 on the panel 206 of FIG. 3 there is a lever 228 for toggle type jib/whip switch 89 for manually switching the tensiometer output depending on configuration of the crane.

The panel 206 also is provided with a drum-type digital main load limit thumb wheel set 230 that is manually adjustable to the desired number of pounds corresponding to the maximum main load line times the parts of line involved, at the option of the operator for safe operation of the crane. A corresponding digital signal is applied to the comparator 74 of FIG. 2. A boom length selector switch knob 232, provided with six stations, is located on panel 206 to the left of an instruction label 234 containing corresponding information relating to the length of the boom in use as shown on the label 234 of FIG. 3.

The following table provides a list of specifications illustrative of the present system:

SPECIFICATIONS ______________________________________ LOAD Sensitivity/Resolution 100 pounds Accuracy + 5 percent of rated load for configuration in use Indicator (Optional) Six-digit display indicating to 999,900 pounds Limit Set (Optional) Thumbwheel switches (main line only) ______________________________________ RADIUS Type Pendulum mass Boom Angle Range 0.degree. to +90.degree. Accuracy Meets SAE 375a Indicator Three-digit display Limit Sets Optional ______________________________________ OPERATION Input Voltage Nominal 24 volts dc Operating Temperature -20.degree.F to + 130.degree.F Line Selection Boom or jib/whip selector switch Parts of Line Selector switch to select parts of line (maximum positions on switch equal to maximum number of parts of line of particular crane) ______________________________________ WARNING Visual Flashing radius display -- black/white-digital (when operating outside load table) Audible Medium Frequency audible warning device Auxiliary Set of SPDT relay contacts (for auxiliary warning unit, such as may be required by law) ______________________________________

In accordance with the present invention, the control and logic module constitutes the heart of the system. Regardless of the type of load sensor selected for a particular system, the control and logic module processes the incoming signal and transmits the correct data to the operator display unit. The latest engineering technology of this unit ensures its reliability and effectiveness in an automated system. For ease of maintenance, most of the circuitry within the module is on printed circuit boards which are constructed and mounted to withstand the rugged operating environment of a crane. The complete assembly is constructed to withstand extreme weather conditions.

The load tables for a particular crane configuration are programmed into read-only memory modules which are installed in the control and logic module. Each system is furnished with six such modules programmed for crane configurations specified by the customer. When a crane configuration is changed, the preprogrammed memory module applicable to the new rigging is chosen by positioning a switch on the control and logic module. Additional memory modules can be furnished to satisfy more crane configurations and existing modules can be reprogammed if a particular configuration is modified or completely eliminated.

The operator display unit is a compact, rugged piece of equipment that can easily be installed in a crane cab at a location which is accessible to and in view of the operator.

The data displayed on the unit is easy to read and understand. A bold-faced meter makes the operator aware of when he is approaching the safe-load limit; the exact condition for the specific crane configuration in use can be seen at a glance. An accurate radius reading from the crane to the load is shown in feet as a digital display and, therefore, requires no interpretation. An optional module used with the operator display unit includes digital displays for allowable load and actual load readings; the allowable load feature makes the crane load chart readily available to the operator. The addition of the optional display module also permits the use of the system as a weighing device.

It should be noted that all digital displays comprise series of individual light segments. These segments are bright enough to make the digital displays clearly visible in direct sunlight.

Another advantage of the present system is the self-test feature which is incorporated in the system. This feature permits the simulation of load conditions thereby checking that all system circuitry is functioning properly. A lamp test is included to ensure that all light segments of the digital displays are operational.

The boom angle transducer used in the present system is a rugged, yet precise, piece of equipment. This unit uses a pendulum-driven potentiometer to measure the angle of the boom with the horizontal. To ensure its reliability, the transducer is made to operate under severe environmental and operating conditions.

The following table is an example of the type of load information which is stored in each different memory module 250, FIG. 11:

LOAD TABLE STORED IN MEMORY MODULE FOR BOOM LENGTH OF 140 FEET Capacity: Capacity: Operating Boom Angle: Crawlers Crawlers Radius: Feet Degrees Retracted Extended ______________________________________ 36 76.8 108,100 124,500 38 75.9 100,300 115,200 40 75.1 93,500 107,200 45 73.0 79,600 90,900 50 70.8 69,000 78,600 55 68.6 60,600 68,900 60 66.4 53,800 61,100 65 64.2 48,200 54,700 70 61.9 43,500 49,400 75 59.5 39,500 44,900 80 57.1 36,000 41,000 85 54.6 33,000 37,600 90 52.1 30,400 34,600 95 49.5 28,000 32,000 100 46.7 25,900 29,700 105 43.8 24,000 27,600 110 40.8 22,400 25,700 115 37.5 20,800 24,000 120 34.0 19,400 22,400 125 30.2 18,200 21,000 130 25.8 17,000 19,700 135 20.7 15,900 18,500 ______________________________________

The system of the present invention provides information to a crane operator which will improve his ability to safely operate the crane. A typical system consists of instrumentation mounted on a crane boom, a control and logic module, and an operator display unit. The load and the angle of the boom are continuously monitored by the instruments mounted on the boom; these are special sensors designed for this particular purpose. Signals are transmitted from the sensors to the control and logic unit which computes the data and sends it on to the operator display unit. Of primary interest to the operator is the indication of the percent of safe load at which he is operating his crane; and other information is also displayed which will allow him to operate the equipment more efficiently.

A typical system is assembled from a family of specifically designed modular building blocks. These include different types of load measuring sensors, the control and logic module which includes most of the system circuitry, the cab-mounted operator display unit which can be used with other optional units for additional data, and a boom angle transducer. The system provides safety indicator equipment of great flexibility in that modules and/or units can be installed to increase the range of capability thereof. Also, the installed system can be easily calibrated in the field to meet existing operational requirements of the crane.

The manually adjustable load (limit) set, boom length and boom radius (constant) signals may be programmed in the control/logic unit, if desired; and the allowable and/or actual load digital readouts may be omitted without departing from the basic concept of the invention. Also, a digital percent safe load indicator may be substituted for the preferred analog meter of the invention.

A latitude of modification, change and substitution is intended in the foregoing disclosure and in some instances some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the spirit and scope of the invention herein.

Claims

What is claimed is:

1. An automatic load and radius indicating system for boom type cranes comprising, a degree of safe load indicator, a load radius display, a line tensiometer, a boom angle transducer, control/logic circuit means including memory means programmable with data based on the configuration of the crane in use, and control circuit means for continuously calculating from signals based on the outputs of said angle transducer and of said tensiometer, and of the memory circuit means, signals corresponding to the load radius and degree of safe load being handled by the crane at the time for operating the corresponding indicator and display in accordance therewith.

2. The system as defined by claim 1, in which the safe load indicator comprises an arcuate dial calibrated in percent of safe load corresponding to the ratio of actual load to allowable hook load on the line in use multiplied by 100, and a pointer rotatable about an axis at the center of said dial which is controlled by an analog signal from said control circuit, the logic circuit comprises an analog/digital (A/D) converter circuit for receiving the output signal of said transducer, a load table memory circuit connected to said converter circuit, an allowable load computer-calculating circuit connected to said memory circuit, an analog/digital converter circuit for receiving the digital output signal of said tensiometer, and a solid state divider circuit for dividing the digital output of said allowable load circuit by the digital output of the converter circuit and multiplying the resulting ratio by 100 for controlling the rotation of said pointer to indicate on said dial the percent of safe load.

3. The system as defined by claim 2, in which the configuration of the crane programmed into the memory circuit means includes operation of a jib pivoted to the free end of the boom, and the corresponding jib line for hoisting lighter loads than those normally handled by the boom per se, whereby the indicator shows the percent of safe load and the true load radius notwithstanding the complicated trigonometric functions involved in the automatic process of calculating the desired information, said jib/whip line comprising a part having the tensiometer associated therewith for continuously measuring the tension thereon corresponding to the relative hook load on such line; and a buffered amplifier circuit for amplifying the corresponding analog output of said tensiometer before application to the corresponding A/D circuit.

4. The system as defined by claim 3, in which the memory circuit means comprises a selected one of a plurality of separate memory modules, each corresponding to an individual crane configuration, and switch circuit means for supplying a desired crane parameter for use in said logic circuit as may be desired for safe operation by the crane operator.

5. The system as defined by claim 4, in which a digital display of allowable crane load is also provided along with a circuit connected to said comparator for conducting digital signals therefrom to the allowable load digital display for operating the latter to show the allowable load for safe operation of the crane under the existing conditions of operation thereof.

6. The system as defined by claim 1, in which the digital load radius display comprises, bold-faced individual digits indicating the number of feet of the actual load radius, and flashing illumination means for warning the operator of the crane that he is operating outside the load table.

7. The system as defined by claim 5, in which the allowable load display comprises, bold-faced individual digits indicating the number of pounds of the allowable load.

8. The system as defined by claim 3, in which the upper range of calibration of the percent of safe load indicator dial is colored yellow and then red to show when the allowable load limit is approached by the moving pointer of the indicator.

9. The system as defined by claim 2, in which the allowable load circuit comprises, a lower load selecting solid state comparator circuit provided with a manual load set input circuit for providing a digital signal corresponding to a desired load limit for comparison with the digital signal output and producing a digital signal corresponding to the allowable load.

10. The system as defined by claim 2, in which the allowable load circuit comprises a multiplexer circuit connected the output of said comparator circuit, a de-multiplexer connected to the output of said multiplexer, a latch circuit connected to the output of said de-multiplexer circuit, a decoder/driver circuit connected to latch circuit, and an allowable load display operated by said decoder/driver circuit, comprising bold-faced numbers corresponding to the load in pounds.

11. A load and radius indicating system for boom type cranes, comprising:

a boom angle transducer unit adapted to be mounted on the boom of the crane,

a load line tensiometer unit adapted to be associated with a selected load bearing line of such crane,

a control/logic unit adapted to be mounted on an inner wall of the cab of such crane responsive to outputs of said angle transducer and load line tensiometer for producing signals indicative of load radius and percent of safe load,

a load and radius indicator unit responsive to said control/logic outputs, comprising a percent of safe load meter and continuous load radius digital readout in appropriate units, adapted to be mounted within such cab in front of the operator, and insulated and shielded cable means for electrically interconnecting said units.

12. The system as defined by claim 11, including an auxiliary allowable load and an actual load indicator unit adapted to be mounted within such end adjacent to the percent of safe load and load radius indicator unit, comprising, a continuous digital readout in pounds of the allowable load, a continuous digital readout in pounds of the actual load as the latter is hoisted by the crane, and connector means for electrically connecting said auxiliary unit to the main display unit.

13. A system as defined by claim 11, in which the control/logic unit comprises, a front panel provided with potentiometer adjusting screws for calibrating different functions of the system, test jacks for checking different parts of the system, a digital parts-of-line selector, a digital signal generating manual load limit set selector, and an instruction card corresponding to the particular configuration of the crane with which the system is to be used.

14. A system as defined by claim 11, in which the load and radius indicator unit comprises, a front panel provided with a manually adjustable rotary control knob having separate lamp test, main line, jib/whip, and OFF stations.

15. A load and radius indicating system as defined by claim 11, in which the boom angle transducer unit comprises, a pendulum oriented arcuate potentiometer providing zero output of zero degree boom angle, as measured from the horizontal, and a maximum output signal when the boom is near a vertical position, a slide-contact on said potentiometer for providing a linear voltage output with a minimum sensitivity of 35.degree., whereby an incremental change in the angle of the boom as small as 20 minutes is detected with a corresponding output signal change to the control/logic unit.

16. A system as defined by claim 15, in which the control/logic unit comprises, an adjustable-gain buffered amplifier connected to the output of said potentiometer for amplifying such voltage output, an analog/digital converter connected to the output of said amplifier for continuously converting the analog signal from said transducer as the boom angle changes during operation of the crane, and cosine ROM and load ROM circuits programmed to automatically calculate digital outputs corresponding to the load radius and allowable load continuously during load hoisting operation of the crane.

17. The system as defined by claim 16, in which the control/logic unit also comprises, a comparator circuit for developing from the manual load set signals and digital signals from said load ROM circuit, the lower of the two for use by the allowable load digital readout.

18. The system as defined by claim 17, in which the control/logic unit includes an adjustable gain buffered amplifier connected to the output of said tensiometer unit for amplifying the load signal, an analog/digital converter for converting such amplified load signal from an analog to a digital mode, a multiplier for multiplying the digital load signals by a digital signal corresponding to the-line-parts, which digital signal product corresponds to the actual line load on the tensiometer unit, for display by said actual load readout, a divider for dividing such actual load digital signal corresponding to the allowable load signal from said comparator, and a digital/analog converter for converting the resulting digital signal to the analog mode which is used to operate said percent of load meter.

19. A system as defined by claim 13, in which the control/logic unit front panel includes a jib/whip switch, a jib/whip load line tensiometer unit, and circuit means for connecting said jib/whip tensiometer into the system.

20. A safe load indicator system for cranes comprising, a solid-state control/logic module unit including transistorized amplifier circuit means for amplifying analog signals corresponding to operating conditions of the crane, transistorized converter circuit means for substantially instantaneously changing such signals to corresponding digital signals, transistorized computer calculating circuit means for automatically processing such signals to produce digital signals based on the configuration of the crane for use by different indicators of desired safe load operating conditions of the crane during operation thereof, said system further including; a boom angle transducer for providing analog signals corresponding to the boom angle of the crane, main line and jib/whip line tensiometers measuring line tension for providing analog signals corresponding to selected main hook and swing hook loads on the crane, and switch means for manually selecting one or the other of such hook load signals as may be required for proper operation of the system.

21. A system as defined by claim 20, in which the system includes memory storage means comprising modules programmed to correspond to the parameters of configuration of the different cranes with which the system can be used, which are necessary for the correct operation of the control logic circuit, whereby the system can be quickly adapted to a selected one of a plurality of cranes of varying configuration.

22. A system as defined by claim 20, in which an information display unit is located in the crane cab comprising, an analog signal responsive bold-faced moving indicator for showing the percent of safe load as an actual load is handled by the selected hook, a large illuminated digital readout for showing the load radius in feet, and solid state circuit means for converting the corresponding digital signals to analog signals for use by said indicator.

23. A system as defined by claim 22, in which illuminated digital readouts are provided for the actual load and allowable load in appropriate units during operation of the crane.

24. A system as defined by claim 23, in which the control/logic module unit comprises, a circuit testing and manually adjustable means for setting the boom length, parts-of-line, main load limit, and calibration of main load and jib/whip line tensiometer circuits.

25. The system of claim 20, in which the line tensiometer and boom angle transducer units supply the analog signals to the input of the control/logic units, and said control/logic unit includes separate solid state circuit means for first amplifying and then converting the analog signals to corresponding ditigal signals, solid state circuit means for continuously processing the digital boom angle signals to thereby produce corresponding digital signals for operating said digital load radius readout, additional solid state circuit means for further processing the digital boom angle signals with the digital line tensiometer signals to produce digital signals corresponding to the percent of safe load on the crane, and solid state circuit means for then converting such digital percent of safe load signals to corresponding analog signals for operating said percent of safe load meter.