US 3612294 A
Description (OCR text may contain errors)
United States Patent 72 Inventor Alvin H. Wilkinson Tillala, Okla. [2l| Appl. No. 846,387  Filed July 31, I969  Patented Oct. 12, I971 [7 3] Assignee Auto Crane Company Tulsa, Okla.
 LOAD CONTROL APPARATUS FOR CRANES 2 Claims, 6 Drawing Figs.
 U.S. Cl 212/39 MS, 2l2/39 B, 2l2/39  int. Cl B66c 13/50  Field otSearch 2l2/39,39 B, 39 MG, 39 l l References Cited UNITED STATES PATENTS 3,072,264 l/l963 Sennebogen 2l2/39 MS 3,200,963 8/1965 Vermes 2 I 2/39 MS FORElGN PATENTS 562,004 ll/l957 Belgium 2l2/39 [149,974 l l/l960 France 212/39 B l,l39,257 ll/l962 Germany... 2l2/39 [255,263 ll/l967 Germany 2l2/39 Primary Examiner-Harvey Cv Hornsby Assirtan! ExaminerMerle F. Maflei Attorney-william S. Dorman PATENTEnncnzrsn 3,612,294 SHEET 10F 2 2000 LBS FIG. I
ALVIN H. WILKINSON INVENTOR ATTORNEY PATENTEU UUIZIQTI 3812294 SHEET 2 BF 2 ALVIN H WILKINSON INVENTOR ATTORNE Y LOAD CONTROL APPARATUS FOR CRANES The present invention relates to a safety device for preventing the tipping over of cranes or the like. More particularly, this invention involves means for sensing the pitching or tilting moment with means for preventing a further increase in the tilting moment beyond a predetermined value thereof.
The desirability of preventing cranes or the like from tipping over is well recognized. To this end, it is conventional to provide hoisting equipment with means for measuring the pitching moment with further means to prevent the pitching moment from exceeding a predetermined value as soon as that value is reached. However, the prior art teaches the use of rather complicated devices to accomplish this purpose. As will hereinafter appear, the present invention represents a simpler and more accurate method of determining and controlling the pitching moment.
Briefly stated, the present invention should be considered in terms of a crane having a boom pivotally supported thereon at what will be determined as a hinge point; a boom support means which is variable in length and which can be a cable or hydraulic cylinders will connect at its upper end to the free or crown end of the boom. The other end of the boom support means will connect to an anchor point on the superstructure of the crane. The hinge point, the crown point and the anchor point form a triangle. The plane of this triangle is a vertical plane in which the boom moves. In one form of the invention, a cantilever beam is located at the anchor point and, in fact, the free end of this cantilever beam actually becomes the anchor point. The beam is connected to the superstructure in such a manner that its longitudinal axis is colinear with the line connecting from the hinge point to the anchor point; by placing an electrical switch adjacent the anchor point and/or cantilever beam and by causing this switch to open or close, depending upon the deflection at the end of the beam, the tilting moment can be limited. In another form of the invention, the beam is pivotally connected to the superstructure of the crane but its longitudinal axis still falls along the line connecting between the hinge point and the anchor point; at the anchor point the beam is connected to one part of a hydraulic pistoncylinder combination and the other portion of the pistoncylinder combination is secured to the superstructure; in this instance, the deflection at the anchor point end of the beam will cause a change in hydraulic pressure within the pistoncylinder combination which can be used to control the tilting moment.
It is a principal object of the present invention to provide a safety device to prevent the tilting moment on a crane or the like from exceeding a predetemiined value.
It is another object of the present invention to provide a safety device of the type referred to above which includes a rigid beam disposed along a line connecting between the hinge point and the anchor point, the outer end of the beam constituting the anchor point, with means responsive to the deflection of the anchor point end of the beam for limiting the tilting moment.
It is a further object of the present invention to provide a safety device of the type referred to above wherein the rigid beam is a cantilever beam, the free end of which is the anchor point with electrical switch means disposed adjacent the anchor point end of the beam for limiting the tilting moment.
It is a further object of the present invention to provide a safety device of the type referred to above which includes an additional safety means to prevent structural overload.
It is still a further object of the present invention to provide a safety device of the type referred to above wherein the rigid beam is pivotally connected to the superstructure wherein the other end of the beam is the anchor point, the anchor point being connected to one end of a piston-cylinder hydraulic unit, the other end of the hydraulic unit being connected to the superstructure with means responsive to the increase in pressure within the hydraulic unit as a result of the deflection of the anchor point end of the beam to limit the tilting moment.
Other and further objects and advantageous features of the present invention will hereinafter more fully appear in connection with a detailed description of the drawings in which;
FIG. I is a semidiagrammatic view of a hoisting apparatus having a pivotal boom;
FIG. 2 is a diagram showing the plane of movement of the boom of FIG. 1 with respect to the hinge point and the anchor point;
FIG. 3 is a moment diagram;
FIG. 4 is an elevation of one fonn of a sensing and control device made in accordance with one embodiment of the present invention;
FIG. 5 is an end view of the switch and associated beam structure shown in FIG. 4; and
FIG. 6 shows a safety device which is a modified form of the present invention.
Referring to the drawings in detail, FIG. I shows a crane carrier 10 having a boom 11 connected to the superstructure of the apparatus at point H" which will sometimes hereinafter be referred to as the hinge point. A boom support means 12, which is of variable length and which can constitute cables or hydraulic cylinders, connects from the upper end of the boom at point C" which will sometimes hereinafler be referred to as the crown point. The lower end of the boom support means 12 connects with the superstructure at point A" which will sometimes hereinafter be referred to as the anchor point. The center of gravity of the entire unit is indicated by the reference character "G" to provide additional stability, outriggers 13 are included.
As the boom support means 12 is shortened with relation to the diagram shown in FIG. 1, the boom 11 will be lifted to a more vertical position; conversely, as the boom support means is relatively lengthened, the boom II will be lowered to a more horizontal position with respect to FIG. 1. Details of the boom support means are not shown; in the event that the boom support means were a cable, a pulley or pulleys could be located on the crown end of the boom with an additional line (not shown) leading to a winch (not shown) mounted on the superstructure for varying the length of the boom support means 12. In the event that the boom support means 12 were hydraulic cylinders, obviously, hydraulic controls would be provided to permit an increase or decrease in the length of the boom support means.
In order to support a load from the end of the boom ll, there is provided a hook 14 which is connected to the outer end of a cable 15. The cable 15 passes around a pulley (not shown) located at the crown end of the boom 11 and a line leads from this pulley to a winch (not shown) on the hoisting apparatus for winding in or letting out the cable 15 and lifting or lowering the hook 14.
The hinge point H, the crown point C and the anchor point A form a triangle structure H-C-A commonly referred to as a truss. As the plane is passed through the points H-C-A, there results a vertical plane (see now FIG. 2) in which the segment of the truss H-A is fixed as to length and position while the boom structure 11 can rotate about the hinge point H between points "B" and D, for example. The support means 12 as indicated heretofore, will be of variable length.
The line segments A-H and I-l-D of FIG. 2 are used to form the moment diagram of FIG. 3. If the distance between points A and H is considered to be 5 feet, and if the extension of the cable 15 were to intersect the line H-D 5 feet to the right of point II, a load of 4,000 pounds on the hook I4 would be compensated by a load of 4,000 points at point A normal to the line A-H because the opposite moments would be 20,000 foot pounds. If this tilting moment of 20,000 foot pounds was considered to be the desired maximum tilting moment, the boom loading can be determined for other dispositions of the boom. For example, as shown in FIG. 3, the safe load would be 2,000 pounds at a 10 foot reach and L000 pounds at a 20 foot reach. Thus, with a sensor at point A to limit the force to 4,000 pounds in a direction normal to line A-H, the proper boom loading can be insured regardless of the angle of the boom 11.
FIG. 4 shows a specific sensor and mounting means for the anchor point. A rigid beam 16 is supported on the superstructure of the crane carrier I as a cantilever beam by rigidly fixing the lower end 17 to a portion 18 of the superstructure by means of the bolt 19 or any other suitable means. The free end of the beam 16 is connected to a toggle member 20 which forms the lower end of the boom support 12 by means of the anchor pin A-l, the center of which is located at the anchor point A. A switch 21 is mounted on the superstructure in any convenient manner (not shown) and is positioned adjacent the anchor point end of the beam 16 such that movement of the anchor point end of the beam will cause the switch to open, as will hereinafter appear, when the load on the beam 16 exceeds a predetermined value. In the switch, element 22 is a grounded terminal, contact 23 is mounted on the outer end of a spring arm 24 so that in the closed position as shown, the contact 23 bears against the grounded terminal 22. The other end of the spring arm 24 is connected to a terminal post 25 which in turn connects with aconductor 26 leading to a motor or other control circuit (not shown). The switch 21 is also provided with an outer lever arm 27 which is pivotally mounted internally of the switch at 28 and which is provided with a pin 29 which holds the spring arm 24 in the position shown. A screw 30 is threaded through the beam 16 and contacts the outer lever arm 27. This screw 30 can be adjusted so that the contact 23 will open when a predetermined force due to boom loading is reached.
It should be understood that the longitudinal centerline of the beam 16 falls along the line between points A and H. Thus, assuming a desired maximum boom loading of 20,000 foot pounds and, regardless of the angle of inclination of the boom 11, if the resulting force in the direction R on FIG. 4 exceeds 4,000 lbs., the deflection of the beam 16 would be sufficient to open the contact 23 and interrupt the circuit between the conductor 26 and the ground.
The outer end of the toggle 20 is provided with an adjusting screw 31 for a purpose which will hereinafter appear. In cases where the hook 14 were disposed to the left of the right-hand outrigger support 13, the tilting moments would be negative in value. Therefore, the crane could lift loads restricted to the structural strength of the crane without danger of tilting. To provide for this greater load, the adjusting screw 31 is incorporated in the toggle 20 so that in the dotted line position of the toggle 20 shown in FIG. 4, the screw 31 will contact the switch lever arm 27 and push it to the left so that a greater deflection of the beam 16 will be required to open contacts 23. The screw 31 can be adjusted so that the contact 23 will open before the safe structural load was exceeded.
In the embodiment shown in FIG. 6, the rigid arm 33 is not cantilever supported as in the case of FIG. 4. The arm 33 is pivotally connected to a portion 34 of the superstructure of the crane carrier by means of the pin 35. The outer end of the arm 33 is connected to the toggle by means of the pin A-l whose center is the anchor point A. The pin A-l is also connected to the hydraulic piston-cylinder unit 35 as will hereinafter appear.
The hydraulic piston-cylinder unit 35 is comprised of a cylinder 36 which is hinged at 37, the latter being connected to a fixed point on the superstructure by means of a pin (not shown). Unit 35 also includes a piston 39 and an interconnecting piston rod 40 having an outer linkage 41 which engages the pin A-l. The two fixed points of the above linkage are 35 and 37. The arm 33 has a longitudinal centerline that is colinear with the line from A to II. Also, the unit 35 is so positioned that the central axis of the piston rod 40 is perpendicular to the line A-H.
Any force in the direction A-R will increase the pressure of the hydraulic fluid 42 which is contained within the cylinder 36. This increase in pressure will be transferred by the conduit 43 to any suitable measuring and control device (not shown) responsive to fluid pressure. These pressure-responsive devices would then preclude the function or functions which would overload the crane.
Whereas the present invention has been described in particular relation to the drawings attached hereto, it should be understood that other and further modifications, apart from those shown or suggested herein, may be made within the spirit and scope of this invention.
For example, opening of the contact 23 could serve to remove power completely from the hoist motor and/or the boom lift motor, or circuitry could be incorporated to merely disable the particular motor in the direction in which it was moving at the time the overload was reached. In any event, it should be understood that additional controls will be provided to operate any function in a manner to decrease the tilting moment after the contact 23 has been opened. Similar considerations hold true for the hydraulic embodiment.
What is claimed is:
1. In a hoisting apparatus having a superstructure, a boom pivotally supported on said superstructure at a hinge point spaced from the center of gravity of said hoisting apparatus, said boom being movable in a vertical plane about said hinge point, a variable length boom support means connected at one end to the free end of said boom and at its other end to an anchor point adjacent said superstructure for moving said boom into different angular positions in said vertical plane, a rigid cantilever beam having a longitudinal centerline substantially colinear with the line between said anchor point and said hinge point, said beam being rigidly connected at one end to said superstructure adjacent said hinge point the other end of said beam extending free from said superstructure and being connected to said other end of said boom support means for constituting said anchoring point, hoisting means connected to the free end of said boom for supporting a load therefrom, and means mounted adjacent said anchor point end of said cantilever beam and independently thereof, responsive to the deflection of said cantilever beam at the anchor point end thereof said means for sensing the deflection of the rigid beam at the anchor point is an electrical switch secured to the superstructure and positioned adjacent the anchor point end of the beam, said switch having operator means in contact with the anchor point end of the beam whereby the switch contacts are closed when the deflection of the beam is less than a fixed predetermined value and the switch contacts are opened when the deflection of said beam exceeds the predetermined value, the opening of said switch contact operating to render inoperative the hoisting means to prevent further increase of the pitching moment.
2. The improvement according to claim 1 including additional means also responsive to the operating angle of said boom support at the anchor point end thereof to prevent the hoisting apparatus from lifting loads which would exceed the structural strength of said apparatus.