Crane Computer

Abstract

A crane load angle computer having a load cell to indicate the actual instantaneous load being sustained by a crane and for developing an electrical signal in response thereto. Means are also provided to develop an electrical signal which is indicative of the actual instantaneous angle of inclination of the crane, and means are provided to develop a signal indicative of the desired maximum loading of the crane at any specified angle. The circuit of the present invention combines the actual load signal with the instantaneous desired maximum signal at a specified angle and utilizes the resulting information to determine whether an alarm should be triggered. An angle potentiometer is provided which has a pair of resistor windings and associated movable contacts which are operated by a pendulum-type actuator. The contacts or wipers move along the respective resistors in accordance with the actual instantaneous angle of inclination of the crane. One of the angle resistors may have its output coupled directly to a meter so as to directly indicate the angle of the crane. The other angle resistor has a plurality of contacts spaced along the length thereof, and a series of potentiometers are coupled to each of these contacts. Each potentiometer provides an output signal which is indicative of the desired maximum loading of the crane at a specified angle which corresponds to the respective points of contact along the angle resistor. Therefore, as the pendulum-operated wiper moves along the resistor, it picks off the signal values which indicate the desired maximum loading at the respective angles of inclination. The alarm is triggered when this load-angle information exceeds a given relationship to the signal at the output of the load cell.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The field of art to which this invention pertains is load-determining systems for a crane and in particular to circuit means for generating a signal indicative of the desired maximum loading of a crane at specified crane angles and for comparing the desired maximum loading with the actual instantaneous loading to determine whether an alarm should be triggered.

SUMMARY OF THE INVENTION

It is an important feature of the present invention to provide an improved crane angle computer.

It is another feature of the present invention to provide an improved system for signalling an alarm during crane overload conditions.

It is an important object of the present invention to provide a circuit for computing the instantaneous desired loading for a crane as the angle of inclination of the crane varies between extreme horizontal and extreme vertical positions.

It is another object of the present invention to provide a circuit for generating a signal in response to the actual loading being sustained by a crane and for comparing that signal with another signal which is indicative of the desired loading of the crane at any specified crane angle.

It is a further object of the present invention to provide an improved angle indicating and computing circuit for delivering a signal to a circuit summation point which is indicative of the desired maximum load signal to be received from a load cell which measures the actual loading being sustained by the crane.

It is a further object of the present invention to provide a computer circuit as described above wherein a plug-in board may be employed in a principal circuit to vary the desired loading-angle relationship for different crane systems.

These and other objects, features and advantages of the invention will be readily apparent from the following description of a preferred embodiment 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.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial block diagram and partial schematic showing the computer circuitry of the present invention and in particular illustrating the circuitry of the plug-in board which is used to produce an output signal indicative of the desired loading of the crane at any specified crane-angle of inclination,

FIG. 2 is a top view of a potentiometer which is operated by a moving pendulum of the type which may be employed in the circuit of the present invention, and

FIG. 3 is a partially sectioned view illustrating the operation of such a potentiometer.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The crane computer circuit of the present invention has means for developing an instantaneous signal which is indicative of the actual loading being sustained by the crane. The circuit also develops a signal which is indicative of the instantaneous desired maximum loading for the crane at any specified angle of inclination. These two signals are then combined and are utilized to determine whether an alarm should be triggered to indicate an overload condition for the crane.

The circuit portion which develops the desired maximum-loading signals for crane angle comprises a plurality of potentiometers or current sources which are coupled in parallel. Each of these potentiometers or current sources are connected to different spaced points along a resistor which may be referred to as an angle-measuring resistor. The angle-measuring resistor is part of an angle potentiometer which is operated by a pendulum-type operator. Essentially, as the crane angle increases or decreases, the pendulum operator moves a contact along the angle-measuring resistor so that the desired maximum-loading signal for a specified angle may be coupled to a current summation point to compare that loading signal with the actual loading signal as provided by a properly positioned load cell.

The angle-measuring potentiometer may also have a separate winding so that the actual instantaneous angle of the crane can be measured directly on an angle-calibrated meter.

An oscillator is provided of a suitable high frequency such as 2,500 Hz. This oscillator is used to power the load cell and to supply power to the series of parallel-coupled resistors to generate the desired current source to be compared with the load cell output.

The oscillator provides output signals of phase A and phase B which are 180.degree. apart. The load cell provides an output signal of phase A and phase B is coupled to the series of parallel resistors to provide an output signal of phase B. Accordingly, when the load cell output signal equals the desired maximum-loading signal, a null condition is reached which triggers an operational amplifier and in turn triggers an indicator light to a phase detector and a differential amplifier.

The angle potentiometer may be of any form which is capable of moving a wiper or contact along the resistor associated with the desired maximum-loading signals. One form of the angle potentiometer consists of a pendulum-operated device wherein the weight of a pendulum actuator arm is used for generating the desired motion of the wiper or movable contact of the angle-measuring resistor.

Referring to the drawings in greater detail, an oscillator 10 has an output signal which may be in the order of 2,500 cycles or some other suitable frequency. The output signal is divided into phase A which is available at terminal 11 and phase B which is available at terminal 12. Phases A and B are generally in the order of 180.degree. apart.

The outputs 11 and 12 are coupled through circuit lines 13 and 14 respectively directly to a load cell 15. The load cell may be conventional in structure and produces an output signal of phase A at its output terminal 16. As is well understood in the load cell art, the output signal 16 is directly related to the actual load being sustained by the load cell.

The load cell 15 may be positioned at some point on the crane which is sensitive to the net weight being sustained by the crane.

Any forces being sustained by the load cell when the crane is in an unloaded state may be balanced by a subtracted potentiometer 17. The balance potentiometer 17 includes a resistor 18 and a movable contact 19. The resistor 18 is coupled directly across the circuit lines 13 and 14 as at contact points 20 and 21 respectively. The movable contact 19 is connected to a resistor 22 and a circuit line 23 to a current summation point 24. Also, the output of the load cell at 16 is likewise coupled to the current summation point 24.

The output from the current summation point 24 is coupled through an operational amplifier 25 having a feedback resistor 26 and to a phase detector 27.

The output of the oscillator 10 is also coupled to the phase detector 27 through circuit lines 28 and 29 respectively.

The phase detector 27 compares the phase of the oscillator with the phase of the signal at the input 30 to the phase detector and generates a direct current output signal at 31 in response thereto. By using the phase detector 27, spurious signals may be prevented from triggering the alarm system.

The output of the phase detector at 31 is then coupled to a differential amplifier 32 as is well understood and the output of the differential amplifier is coupled to a signal lamp 33.

The angle potentiometer or angle transducer is indicated generally by reference numeral 34 and includes a pendulum 35 which operates a pair of movable contacts or wipers 36 and 37.

The contact 37 operates in conjunction with the resistor 38 which is coupled from a suitable voltage source at 39 to ground as at 40. An adjustable potentiometer 41 is coupled in series with the contact 37 and couples energy from the contact 37 to a meter 42 which is grounded as at 43.

The potentiometer 37-38 is used directly as an indicator of angle of the crane. The contact 37 is moved along the resistor 38 in accordance with the actual instantaneous angle of the crane. The output signal from the movable contact 37 registers on the meter 42 which is calibrated in terms of degrees of angle.

The program or plug-in board which is utilized to develop the respective current sources indicative of the desired maximum loading of the crane at respective angles is indicated generally by reference numeral 44.

The program board 44 consists of a plurality of resistors 45 through 50. These resistors are connected in parallel from a circuit point 51 on the circuit line 14 to circuit ground as at 52. While six such resistors are shown in the drawing, more or less resistors may be utilized as desired and as indicated by the broken circuit line as at 53.

Each of the resistors 45 through 50 has a movable contact associated therewith such as the contacts 54 through 59. These contacts may be varied to provide the desired current signal output at the respective angle of inclination of the crane.

Each of these movable contacts 54 through 59 have their outputs connected as at 60 through 65 to an angle-measuring resistor 66. The angle-measuring resistor 66 operates in conjunction with the movable contact or wiper 36 which in turn is driven by the pendulum 35.

Accordingly, it is apparent that as the angle of the crane changes and the wiper 36 moves along the length of the resistor 66, a program set of current sources are coupled to the output of the contact 36. As explained, these current sources reflect the desired maximum loading of the crane at the given angle which is reflected by the mechanical positioning of the movable contact 36 of the resistor 66.

The output of the contact 36 is coupled to a scaling resistor 67 which in turn is coupled as at 68 directly to the current summation point 24.

Since the current supplied by the movable contact 36 is opposite in phase to the current supplied by the line 16 at the load cell 15, these two signals will subtract from one another at the current summation point 24. Accordingly, as the actual load on the cell 15 equals the desired maximum loading as determined by the setting of the potentiometers 54 through 59, the signal at the current summation point will be zero and the differential amplifier 32 will be triggered to produce an alarm at the indicator 33.

If an actual reading of the load being sustained by the crane is desired, a push button 69 may be actuated to disconnect the movable contact 36 from the current summation point 24. When this occurs, the output of the operational amplifier and phase detector is directly indicative of the load being sustained by the load cell. This may be measured by a meter 70 which is operated by a meter range switch 71. As shown by the dashed line 72, the switch 69 may be part of the meter range switch 71.

The angle transducer may be of any desired form, and one such form is shown generally in FIGS. 2 and 3. The angle transducer generally comprises a casing or housing 73 which has a movable weight 74 pivotally mounted therein as at 75. A mass 76 may be coupled to the weight as shown in FIG. 3, and the entire assembly may be so mounted on the crane such that increased angle of the crane causes the weight of the member 76 to pivot the blade 74 about its pivot point 75. The potentiometer is shown as at 77, and as well understood, the movement of the blade 74 will cause the contacts on the potentiometer, the contacts 36 and 37 of FIG. 1, to advance along their respective resistors, 66 and 38 respectively. The output from the angle transducer may be coupled through a cable as at 78.

Through the circuit features of this invention, a continuous automatic monitoring of the critical loading of the crane is achieved, and at the same time means are provided for specific load and angle readings for manual checking of the load-angle relationship.

Claims

I claim as my invention:

1. A crane load angle computer comprising:

a load cell and means for producing a first signal therefrom representative of the instantaneous load being sustained by a crane,

means for producing a second signal representative of the desired maximum-loading of said crane at specified angles of inclination thereof,

means for combining said first and second signals, and

means for triggering an alarm when the actual load as measured by said first signal exceeds the desired maximum load as determined by said second signal, said means for producing said second signal comprising a series of parallel-coupled maximum-loading potentiometers, each having a predetermined signal output corresponding to the desired maximum crane loading at a specific different crane inclination angle.

2. A crane load-angle computer in accordance with claim 1 wherein said maximum-loading potentiometers are assembled on a plug-in board to have the desired characteristics for the specified crane being utilized and wherein the plug-in board couples each of said maximum-loading potentiometers to the respective desired points on the angle-measuring resistor.

3. A crane load-angle computer in accordance with claim 2 wherein the signal developed at said movable contact is out of phase with said first signal at the output of said load cell and wherein means are provided for summing said out-of-phase signal to produce a null condition when the actual loading at a specific angle equals the desired maximum loading at that angle.

4. A crane load angle computer comprising:

a load cell for producing a signal representative of the load sustained by the crane,

computer means for producing a desired maximum-loading signal that varies with crane angle,

means for comparing the load-cell output signal with the desired maximum-loading signal and for generating an alarm when a given relationship between the actual load signal and the desired maximum-loading signal is reached,

said oscillator having a first signal coupled to said load cell and a second out-of-phase signal coupled to said computer means and wherein a circuit current-summing point is provided to combine the load cell output current with the out-of-phase computer output current.

5. A crane load-angle computer in accordance with claim 4 wherein said computer means comprises a series of current sources representative of a desired loading at given angles of inclination of said crane and means responsive to the instantaneous angle of said crane for coupling the associated one of said current sources to said comparison means.