US2036386A - Crane - Google Patents

Description

Mmmm 79 WQ N. n. E. ANDERSW CRANE Filed Deo. 18, 1933 2 Sheets-Sheet l ATTQRNEY Patented Apr. 7, 1936 UNITED STATES PATENT OFFICE CRANE.

Application December 18, 1933, Serial No. 702,997

5 Claims.

This invention relates to cranes in which the raising of the boom causes the load to move horizontally toward the crane without ascending vertically. Cranes of this type are kno-wn, but are 5 unnecessarily heavy and cumbersome and require a greater working area for their operation than the crane of this invention.

One object of this invention is to provide a novel means for securing a horizontal movement of the l0 load as the boom is raised.

Another object is to provide a novel mounting for the boom of such a crane which reduces the working space required by the crane and increases its speed of operation.

Other objects will become apparent from the description of the invention and from the appended claims.

The invention will be best understood by referringv to the drawings in which Fig. 1 is a side view of a craneshowing the working elements to which this invention relates, the boom being in the lowest position;

Fig. 2 is a diagrammatic partial side view showing the crane of Fig. 1 when the boom is in a median position;

Fig. 3 is a diagrammatic partial side View showing the crane of Fig. 1 with the boom in an upper position;

Fig. 4 is a detail diagrammatic view in perspective of the sheaves which counterload the hoisting boom and of the hoisting cable multiply reeved over the sheaves;

Fig. 5 is a diagrammatic partial side view oi another form of a crane of this invention wherein 5 the counterloading sheaves are actuated by geared segments.

Referring now to Fig. l, the crane is shown mounted upon a supporting structure Il! by means of a turn-table II. On the turntable is a crane operators cabin I2 and a frame I3 for supporting a boom I4on the pivot I5. The operators cabin contains a hoisting engine and hoisting controls, neither of which is shown in the drawings. The boom I4carries ahoisting sheave I6 at its upper end and has an extension I'I at itslower end for carrying a set of three coaxial, counterloading sheaves I8. The center of the sheaves I8` is located on the axis of the boom I4 which passes through the boom pivot I5 and the center of the hoisting sheave I6.

The length of the boom I4 from its pivot I5 to the center of the hoisting sheave I6 is ten times the distance from its pivot I5 to the center of the counterloading sheaves I8. This ratio is taken as an illustrative example only and other ratios may be adopted if compensatory changes are made in the means for counterloading the boom. Attached to a plate I9. at the rear end of the boom I4l is a weight 2| which counterbalances the weight of the boom about the boom pivot I5.

Attached to the frame I3 by the pivot 22, located perpendicularly below the boom pivot I5, is a bell crank lever 23. A sheave 24 is also mounted on this pivot 22. One arm 25 of the bell crank lever 23 extends rearwardly and carries another set of three coaxial, counterloading sheaves 26. The length of this arm 25 is equal to the rearward extension I'I of the boom I4 from its pivot I5 to the center of the upper counterloadingsheaves I3. The other arm 2l of the bell crank lever 23 extends forward and carries the pivot 28 to which is attached the link 29, the other end of which is attached to the boom I4 bymea-ns of the pivot 3l.

The relationship between the various links, pivots and levers is best understood by referring to Fig. 2, which shows the boom I4 in a position halfway' between its upper and its lower limit. In order to clarify the description, a horizontal line A-A has been drawn mid-way between the boom pivot I5 and the bell crank pivot 22 and a straight line B has been drawn connecting the boom pivot I5 with the upper pivot 3| of the link 20. The arrangement of the parts is such that the angle which the bell crank lever arm 25 makes with the line A-A is equal to the angle which the axis 45 of the boom I4 makes with the line A--A. The line A-A furthermore bisects the angle made by the arm 25 of the bell crank 23 and the axis 45 of the boom I4. The arm 21 of the bell crank 23:1is of equal'length with the line B and is parallel to it and when the boom is in the position halfway between itsV upper and lower position. With this arrangement of parts the bell crank arm 25 will remain substantially symmetrical with the axis 45 ofthe boom I4 in respect to the line of symmetry A-A for all positions of the boom I4. This symmetrical relationship for other positions of the boom I4 is shown by Figs. 1 and 3.

Referring again to Fig. 1, a hoisting cable 32 carrying the hook 33 is passed over the hoisting sheave I6 at the end of the boom I4 and multiply reeved over the two sets of counterloading sheaves I8 and 26, so thatve strands of the hoisting cable 32- extend between the two sets of sheaves IliandY 26. Fig. 4 shows a developed view of the reeving between the counterloading sheaves I8 and 26. The hoisting cable 32 is carried over the sheave 24 to the hoisting drum 34, which is operated by suitable machinery, not shown in the drawings.

It will be observed that a load carried on the hoisting hook 33 will, because of the multiple reeving of the hoisting cable 32 at the rearward extension I'i of the boom I4, exert a downward. or counterloading pull on the upper counterloading sheaves I3 which is iive times as large as the downward pull of the load on the upper end of the boom i4. The multiple reeving of the hoisting cable 32 will similarly exert an upward pull on the lower counterloading sheaves 23 equal to the downward pull on the upper sheaves I8, and this upward pull is transmitted to the rearward extension l? of the boom I4 as a downward pull by the bell crank lever 23 and the link 29. The total downward pull on the rearward extension I 'I of the boom I4 is therefore ten times the downward pull of the load on the upper end of the boom i4 and since the length of the boom ifi from the boom pivot I5 to the center of the hoisting sheave I3 is ten times the length of the rearward extension I'I of the boom from the boom pivot i5 to the center of the upper counterloading sheaves I8, the boom I4 is fully counterloaded about its pivot I5. Since the weight of the boom i4 is also counterbalanced by the weight 2 I, the boom E4 may be raised or lowered regardless of the extent to which it is loaded by a force suicient merely to overcome the friction and the inertia of the various moving parts, Furthermore, as the boom I4 is raised, the upper and lower counterloading sheaves I8 and 26 coming together will pay out an amount oi cable suiiicient to keep the load almost exactly on a horizontal line. Figure l shows the line of travel C-C of the hoisting hook 33 as the boom I4 is raised. The number of counterloading strands between the sheaves i3 and 26 of the hoisting cable 3?. required for any length of boom is found by dividing the boom length from its pivot I5 to the center of the hoisting sheave IG by twice the distance between the boom pivot I5 and the center of the counter-loading sheaves I8.

The various sheaves of the crane are so arranged that as the boom I4 is raised or lowered the additional wrapping of the hoisting cable 32 about one sheave is compensated by the unwrapping of the cable 32 from another sheave, thus assisting in the more exact preservation of a horizontal movement of the load. For example, if the boom I4 is raised through an angle of thirty degrees, the wrapping of the cable 32 about the hoisting sheave IG will be increased by an arc of thirty degrees on the circumference of this sheave I6, but this wrapping is offset by the unwrapping of an equal amount from the first sheave of the upper set of counterloading sheaves I3 of the boom i4. rIhe additional wrapping of the cable 32 on the sheave 24 will likewise be offset by an equal amount of unwrapping from the last sheave of the lower set of counterloading sheaves 26 on the bell crank lever 23. The horizontal movement of the load is, furthermore, not affected by a change in the size of the sheaves provided the size of all sheaves are maintained uniform.

The boom Ibi may be raised or lowered by any convenient means. One means is shown in Fig. l and comprises a lever 35 secured to the boom I 4. Pivotally attached to this lever 35 is a link 3G which at its other end is secured to the pin 3'I of the crank arm 33. This crank arm 38 may be rotated by means of its shaft 39 which extends into the control cabin I2 and is driven by suitable machinery, not shown. Rotation of the shaft 39 in the proper direction will produce the desired raising or lowering of the boom. Since but little energy is required to raise the boom I4, this operation may be performed quickly so that after the load is raised it can be moved rapidly toward or away from the crane.

The boom I4 is mounted on the frame a substantial distance to the rear of the center of rotation of the crane on the turntable II. This has many advantages when applied to this type of a crane over the customary mounting of the boom I4, which is at or in front of the center of rotation.

First, the load may be brought over the operators cabin I2 when the crane is to be turned. When in this position the load does not project beyond the cabin I2 and the crane may be turned in a very restricted area. This is especially advantageous when several cranes operate close together, as in the unloading and reloading of ships. Usually two or three cranes of this invention can operate over each hatch of the vessel with the result that the lay-over time of the vessel is reduced to the minimum.

Second, the load when so placed is near the center of rotation of the crane and has a low radius of gyration so that less power is required to turn the loaded crane.

Third, the load when near the center of rotation of the crane has a lessened tendency to swing outwardly by centrifugal force as the crane is turned and the turn can therefore be made faster than with the usual mounting.

Fourth, if the crane requires turning through 180 degrees the load may be carried in a straight line from the point of pick-up to the point of deposit, traveling directly over the turning center of the crane. This possibility, together with the possibility of moving the load rapidly on a horizontal line makes possible an articulation of the various elements which is conducive to the rapid handling of the material.

Fifth, the rearward mounting of the counterweighted boom I 4 causes the entire weight of the boom I4 and the counterweight ZI to be applied to the rear of the crane. This weight, applied as it is to the rear of the frame I3, will under some conditions be suflicient to balance the moment of the load being lifted to such an extent that reactions in the turntable I I can be kept within desired limits without the application of any of the usual counterweighting to the rear end of the frame. At any rate, the amount of such counterweighting in such cases as may require the same will be very substantially reduced, and as a result, the crane of this invention will be lighter in weight than the ordinary crane of the same lifting capacity. All of these advantages combine to produce a crane of less weight, greater adaptability, lower initial cost, lower operating cost, and greater operating speed than the usual type of crane.

To secure symmetrical movement between the upper and the lower counterloading sheaves I8 and 25, other commonly known connecting elements may be employed. In Fig. 5 is shown a common means which serves this purpose. The boom carries a gear segment 4I which meshes with a lower similar segment 42 pivotally secured to the frame by the pivot 43. The arm 44 of the lower segment carries the lower set of counterloading sheaves 26 upon which the hoisting cable 32 is reeved in the same manner as in the first embodiment of the invention. The pivot 43 and the arm 44 correspond also in all essentials with the pivot 22 of the bell crank lever 23 and the lever arm 25, respectively.

By omitting the hoisting machinery and deadending the cable 32 at or near one of the pivots of the counterloading sheaves I8 or 26 a structure is obtained which may be utilized to suspend objects, such as illuminating units, in any position on a horizontal plane within operating radius of the boom.

While this invention has been shown and described as embodied in particular forms, it is intended that the protection of letters patent be not unnecessarily limited thereby inasmuch as various changes and modifications may be made without departing from the principle of the invention.

I claim:

1. A crane comprising a turntable, a frame mounted on said turntable, a hoisting drum on said frame, a counterweighted boom pivotally attached to said frame to the rear of the axis of rotation of said frame on said turntable, means for raising and lowering said boom, a hoisting sheave on said boom, a second sheave on said boom for counterloading said boom, a bell-crank lever pivotally attached to said frame, a third counterloading sheave on the rearward extending arm of said bell-crank lever, a link pivotally attached to the forward extending arm of said bell crank lever and to said boom, and a hoisting cable passed over said hoisting sheave and over said second and third counterloading sheaves and dead-ended on said hoisting drum.

2. A crane comprising a turntable, a frame mounted on said turntable, a hoisting drum on said frame, a counterweghted boom pivotally attached to said frame to the rear of the axis of rotation of said frame on said turntable, means for raising and lowering said boom, a hoisting sheave on said boom, a second sheave on a rearward extension and on the center line of said boom for counterlcading said boom, a bell-crank lever pivotally attached to said frame vertically below the pivotal attachment of said boom on said frame, a third counterloading sheave on the rearward extending arm of said bell-crank lever, a link pivotally attached to the forward extending arm of said bell crank lever and to the rearward extension of said boom, and a hoisting cable passed over said hoisting sheave and over said second and third counterloading sheaves and dead-ended on said hoisting drum.

3. In a horizontal luing crane, the combination comprising a cab carrying hoisting machinery, a boom support mounted upon said cab, a boom pivotally mounted upon said boom support and extending outwardly over the cab and rearwardly beyond said pivot, a sheave nest on the rearward extension of said boom, a sheave on the outer extremity of said boom, a walking beam pivot placed directly below said boom pivot, a walking beam mounted thereon said walking beam extending rearwardly beyond said pivot, said rearward extension being equal in length to the rearward extension of said boom, a nest of sheaves mounted upon said rearward extension of said walking beam, a sheave mounted upon the pivot of said walking beam, means connecting said pivoted boom and said walking beam and confining the same to equal and opposite angular movement, a hoisting drum in said cab, and a hoisting line passing from said drum rearwardly over said sheave mounted on said walking beam pivot, thence to and fro alternately about the sheave nest attached respectively to said walking beam and said rearward extension of said pivoted boom, and thence about a sheave on the outer extremity of said boom, the angular deflections of said hoisting line about said sheaves being in a clockwise direction only.

4. In a crane of the class described, a base, a frame mounted thereon, rotatable means interposed between said base and said frame so that said frame may rotate horizontally about a center, a boom support carried by said frame on one side of said center of rotation, a boom having a rearwardly extending overhang and a forwardly extending main portion pivotally mounted on said boom support for luiiing movement so that said main portion extends forwardly across said center of horizontal rotation, a counterweight attached to said rearwardly extending overhang, means for causing luiiing movement of said boom, and means associated with said boom for lifting a load.

5. In a crane of the class described, a base, a circular track on said base, a turntable centered with respect to said track for turning movement about the center thereof, a frame mounted to turn on said turntable, a boom support rigidly mounted on said frame and extending above the same and laterally displaced with respect to the center of said turntable, a boom pivot mounted on said boom support, a boom pivotally attached to said pivot and arranged to swing in a vertical plane and to extend forward over said turntable center, an extension rigidly attached to said boom and extending beyond said pivot in a direction opposite to the direction in which the boom extends, a counterweight attached to said extension, means for causing lufng movement of said boom, and means associated with said boom for lifting a load.

NILS PETER ERIK ANDERSEN.

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