US2015957A - Safety device for the prevention of overloading cranes and the like - Google Patents

Description

Oct. 1, 1935.- L. B. N EAL Er AL 2,015,957

SAFETY DEVICE FOR THE PREVENTION OF OVERLOADING CRANES AND THE LIKE v 2 Sheets-Sheet 1' Filed Dec. 23, 1930 INVENTORS .l u'l'e 2117.240 and fltaw M Sta mar ATTORN EY Oct. 1, 1935. L. B. NEAL El AL SAFETY DEVICE FOR THE PREVENTION OF OVERLOADING CRANES AND THE LIKE Filed D60. 23, 1930 2 Sheets-Sheet 2 VIII/ll fill/Ill KW q ELK M b j WITNESS d/ ATTOR N EY Patented Oct. 1, 1935 UNITED STATES PATENT OFFICE SAFETY DEVICE FOR THE PREVENTION OF OVERLOADING CRANES AND THE, LIKE Lillie B. Neal and Blanche M. Stoner, Bremerton, Wash., assignors to J. 0. Neal, Port Orchard,

Wash.

Application December 23, 1930, Serial No. 504,384

6 Claims.

and claimed.

It is an object of our invention tov provide a safety device for cranes and the like wherein an operator of the crane may be appraised of the load upon the crane, thus avoiding accidents due to an overloading of the crane, which in many instances causes overturning thereof.

'It is a further object of the invention to provide a safety device in which a visual indicator is employed, operable in conjunction with an audible signal.

A still further object of the invention is the provision of a safety device wherein a warning of load limit will be given at any danger point of the radial swing of the boom. I

Additional objects, advantages and features of invention will be apparent from the following description and accompanying drawings forming a.- part of this application, wherein,

Figure l is a side elevation of a locomotive crane equipped with one safety device,

Figure 2 is a top plan view of the boom,

Figure 3 is a plan view of the indicator,

Figure 4 is a vertical section of the indicator and illustrating the electrical circuit for the audible signal,

Figure 5 is an enlarged vertical section on the line 5--5 of Fig. 3, illustrating the operating mechanism for the indicator, and

Figure 6 is a detail of one of the drums.

. It will beunderstood that we do not limit ourselves to the adaptation of our device to locomotive cranes, but, for illustration, we have shown the invention as applied to a locomotive crane ill, which may be of any usual construction embodying a boom II. The boom II is suitably mounted for vertical swinging movement as at l2, and movable radially with the cabin l3, as is customary.

The crane l0 embodies a power drum I4 having a load line l5 threaded through a sheave l6 mounted at the outermost point of the boom H and through block H from whence the cable is passed around a sheave l8. From this sheave, the cable I5 is extended rearwardly and trained about a pulley i 9 carried upon a lever mounted adjacent the base of,the boom II, as clearly shown in Fig. 2. After passing through the pulley t9, the cable is extended forwardly for passage around a pulley 21, mounted upon the forward end of the boom H, but to the rear of the sheaves 16 and I8. The cable I5 is finally secured to the block ll as at 22. It is evident that the particular arrangement of the cable 15 from the power drum l4 to its dead end, as above described and shown,

have no relation to this invention and that that 5' portion between the pulley l9 and the shackle 22 may be considered the deadend of the cable. The stress on the ,cable I5 is, of course, the same at all points therein and depends on the weight lifted and the number of cable-sections supporting the block H. In the drawings this stress is therefore one-third of the weight being lifted, but if the dead end were loosed from the block I1 and attached. directly to the lever 20, the stress therein would be one-half that of the weight, while if it passed twice around the pulleys in the block I! and the end of the boom and thence to the lever 20, the stress therein would be one-quarter that of the weight.

From a consideration of Fig. 2, it will be noted 20 that the lever 20 is pivotally mounted upon one side of the boom II, as indicated at 23, and adjacent the opposite end is suitably apertured for mounting of a compression spring 24. The spring is confined within a suitable housing which is secured by a. tum-buckle or other suitable adjusting device 25 to the base of the crane Ill. The tension of the spring may thus be varied by adjustment through the turn-buckle.

The lever 20 may be apertured as at 26 in order to vary the attachment of the pulley l9, as found necessary, thereby varying the proportion of the stress, in the weight-raising cable I5, which is counterbalanced by the spring 24 and therefore varying the extent of movement of the lever 20 for a given load on the crane boom.

A cable 21 is attached to the lever 20 adjacent its free end and passes therefrom under the pulley 28, adjacent the pivot pin E2 of the boom, and thence around suitable pulleys 28 to our indicator 29, which will be fully described hereinafter. A cable 30 extends from our indicator, suitably guided by pulleys 3| and is attached to the boom H as at 32. We preferably include adjusting means 33 in the cables 21 and 30 to take up any slack which may occur through stretching, or otherwise.

From the foregoing, it will be apparent that as the weight is applied to the power line IS, a pull will be exerted upon the cable 21; and that any raising movement of the boom II will cause a corresponding slackening movement to the cable 30 and vice versa.

Our indicator 29 is mounted within the cabin 13 in a position immediately before an operator of the crane, and in our present construction embodies a housing ll having a shaft 35 Journalled in the upper part thereof. A cam or drum I6 is keyed upon the shaft 38 and is preferably ecoentrlcally mounted with respect to the shaft. so that any variation in the travel of the boom H may be readily accommodated. The drum It is suitably grooved to receive the cable 21, the end of which is secured therein.

A drum I1 is also keyed upon the shaft II, and has a cable It coiled therearound to the lower end of which there is secured a counterweight 19. adapted to keep the cable I! taut.

As clearly shown in Fig. 5, a hollow shaft 40 is revolubly mounted on the shaft 35 and has keyed thereon drums II and 4!. The shaft 40 projects through the housing II at one side but stops short of the projecting end 35a of the shaft 3!. Indicator hands 48 and II are secured upon the projecting ends of respective shafts l and 40 for rotary movement about the dials Cl and it, respectively, caused by rotation of respective drums 80 and I2.

Becured to the drum ll, we provide a cable I], to the lower end of which there is attached a counterweight 4' adapted to keep the cable It taut.

The counterweights II and 4B are movable longitudinally of the housing II, and are suitably guided in their paths by a guide-way 09.

The cable ll is coiled about the drum 4! and the end thereof secured to the drum in a suitable manner.

It will be apparent that a pull upon either of the cables 21 or II will cause rotation of its associated drum, and consequent movement of the indicator hands ll or 44, as the case may be. It is also apparent. since an increase in the weight lifted causes a tension in the cable 21 and a counterclockwise rotation of the shaft 3! and its indicator hand 43, and a raising of the counterweight and an increase in the leverage of the weight or the distance that the boom end extends from the cabin II causes a slackening of the cable SI and consequently a clockwise rotation of the shaft II and its indicator hand 44, and a lowering of the counterweight ll, that the hands 48 and ll turn in opposite directions on an increase of either the weight or its leverage, and that the counterweights 38 and 48 also travel in opposite directions on such increase. When the crane is inactive and the boom is raised, the counterweight II is at the top of its travel and the counterweight II is at its lowest point of travel. when the combined effect of an increase in the weight and/or leverage is such as to endanger the safety of the crane, the said counterweights will have moved to the relative positions shown in Fig. 4, though it must be understood that this condition may occur at any point in the travel of the weights, for instance, an extremely heavy weight will cause the counterweights 39 and ll to meet at the upper end of their travel, thus indicating that the boom must be held substantially vertically when handling such a load, while a comparatively light load will cause them to meet at the lower end of travel when the boom is extended as low as possible. The crane can be safely handled so long as the counterweight l! is higher than the weight 38, but any increment of added weight or leverage will immediately bring them into line.

To provide an audible signal, we mount a pair of contracts III and Ii upon the counterweights II and I. These contacts are suitably insulated and of a length to aflord a brushing contact one with the other, during movement of the counterweights. An electric bell I2, and battery 88 is in electrical connection with the contacts 50 and II so that the bell will be sounded upon completion 5 of the circuit through movement of the counterweight.

The operation of our device is substantially as follows:

We will say that we are about to elevate an object twenty feet away from the center of gravity of the crane, and the load limit at this radius is 10 tons. The movement of the boom I l to position to bring the block H to a point centrally of the object to be elevated will cause a move- 16 ment of the cable It, and in doing so rotation of the drum 4! is effected, with consequent movement of the indicator hand 44 on the dial 4. to indicate. the movement of the boom. During movement of the drum 4!, a like movement is imparted to the drum II, which in turn moves the counterweight ll to a predetermined point. Now, if the object to be lifted does not exceed the permissible 10 tons the crane may be operated, as usual through the power drum ll. Also the pull exerted through the power line II will pull the lever 20 compressing the spring 24, and pulling the cable 11. The pull upon the cable 21 causes rotation of the drum It and rotation of the hand 43 to indicate the weight being lifted. However, should the weight exceed the assumed .10 tons, the hand ll will turn until it assumes a position directly over the hand I. The movement of the hand 43 has also brought the counterweight 39 directly opposite the counterweightl8, and therefore the contacts are in contacting relation one with the other, consequently sounding the bell I2, to indicate an excessive load and return of the boom to the vertical.

Upon release of a load, the hands I! and N 40 will assume their normal zero reading. brought back to such position through the counterweights l9 and It. It should also be noted that the hands 43 and 4| are synchronized with the contacts 50- carried by the counterweights.

From the foregoing it will be apparent that we have provided a safety device which is simple in construction and efficient in operation, and one which may be readily installed upon cranes already in use.

What is claimed is:

l. A safety device for cranes comprising a swinging boom; a weight-raising cable therefor; an indicator having a pair of concentric dials; a pair of indicator hands mounted in the axis of said dials and adapted to indicate, respectively, the

radius of said boom and the weight being raised by said cable; a shaft for each of said hands; cable means connected between said boom and one of said shafts; means mounted on said boom and connected to said weight-raising cable and movable thereby in response to the load applied thereto; cable means connected between said other shaft and said load-responsive means; and counterweights operably connected with said last two cables whereby said cables are maintained taut.

2. A safety device for cranes comprising a vertically swinging boom; a weight-raising cable therefor: an indicator having a pair of concentric dials; a pair of indicator hands mounted in the axis of said dials and adapted to indicate, respectively, the radius of said boom and the weight being raised by said cable; a shaft for each of said hands, cable means connected betact witheach other and in circuit with an elect'ric signal whereby said signal will be energized upon mutual contacting of said contacts during movementof said counterweights.

' 3. A safety device for cranes or the like, comprising a vertically swinging boom; a lever pivoted at one end to said boom andextending transversely thereof; a weight-raising line, wholly independent in its operation of the operation of said vertically swinging boom. and having itszdead end connected with said lever and having the weightraising force applied to its other end; a counterbalancing spring between said lever and said boom; an indicator; a pair of rotatable hands; and cable means between the respective hands and said lever and boom, whereby said hands are rotated in opposite directions to indicate respectively an increase in the radius of said boom and the weight applied to said weight-raising line.

4. A safety device for cranes having a means for raisinga weight at variable radii'from the center of gravity of the crane, and independent means forchanging the said radius an indicator; a pair of concentric shafts mounted therein and each carrying an indicator hand; a pair of operating drums mounted on said concentric shafts; cables wound on both said'drums and operatively connected respectively .to the weight-raising means and to the radius-changing means, whereby an increase in bothsaid means will cause the .corresponding drums to rotate in opposite directions; a second pair of drums mounted on said concentric shafts; cables woundon said second pair of drums in directions opposite to the directions of I the cables wound on the first pair of drums on the same shafts. respectively; and counterweights onsakisecondpairofcabless- 5. A safety device for cranes having a means for raising a weight at variable the center of gravity of the crane, andindependent means for changing the said radius; an indicator;

a pair of concentric shafts mounted therein and g each carrying an indicator hand; a pair of operating drums mounted on said concentric shafts; cables wound on both said drums and operatively connected respectively to the weight-raising means and to the radius-changing means, where- '10.

by. an increase in both said means will cause the corresponding drums to rotate in opposite directions; a pair of counterweights; and connecting means between said counterweights and said concentric shafts whereby said counterweights tend to oppose the motion of the respective shafts under the action of said weight-raising means and said radius-changing means.

6. A safety device for cranes having a means. for raising a weight at variable radii from thecenter of gravity of the crane, and independent means for changing the said radius; an indicator;

a pair of concentric shaftsmounted therein and each carrying an indicator hand; a pair of operating drums mounted on said concentric shafts; cables wound on both said drums and operatively connected respectively to the weight-raising means and to the radius-changing means, whereby an increase in both said means will cause the corresponding drums to rotate in opposite directions; a pair of counter-weights; connecting means between said counterweights and said concentric shafts whereby said counterweights tend to oppose the motion of the respective shafts under the action of said weight-raising means and I said radius-changing means; an electric signal circuit; and a pair of electric contacts mounted in the signal circuit and operatively attached to the respective counterweights and adapted to move therewith into contact with each other to close so the signal circuit when the combined action of the weight lifted and the radius of action thereof exceeds a predetermined amount.

IJLLIEB. NEAL.

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