US2888150A

US2888150A - Level luffing attachment for cranes

Info

Publication number: US2888150A
Application number: US469161A
Authority: US
Inventors: Robert P Fox
Original assignee: CLYDE IRON WORKS Inc
Current assignee: CLYDE IRON WORKS Inc
Priority date: 1954-11-16
Filing date: 1954-11-16
Publication date: 1959-05-26
Anticipated expiration: 1976-05-26

Description

May 26, 1959 R. P. FOX

LEVEL LUFFING ATTACHMENT FOR CRANES Filed Nov. 16, 1954 INVENTOR Q fioker'f I? fbx 1 BY m ATTORNEY LEVEL LUFFING ATTACHlVlENlF FOR 'CRANES Robert P. Fox, Duluth, Minn., assignor to 'Clyde Iron Works, Inc., Duluth, Minn, a corporation of Minnesota Application November 16, 1954, Serial No. 469,161

3 Claims. (Cl. 212-58) This invention relates to an improvement in level lufiing attachment for cranes, and deals particularly with an attachment which can be added to a standard crane of the Whirley type without impairing the normal capability of the main or heavy tackle.

For many years, the advantage of level luffing gear on cranes designed for certain uses has been recognized. Numerous types of gear has been produced to accomplish this result. In general, in a level lufling crane, the load traverses a horizontal path as the boom of the crane is luifed from maximum to minimum radius. High speed operation without loss of safety and control is possible, and the swinging and lufling of the boom may be easily coordinated by an operator having limited experience. Perhaps the greatest advantage of this type of gear, however, lies in the fact that little lutfing power is required, since the load is not lifted as the boom is raised.

While level luffing cranes have been in use for some years, such cranes are designed specially for this purpose, and cannot be used as all purpose cranes. It is the purpose of the present invention to provide an attachment to a crane of conventional type which is capable of transforming a conventional crane into a level lufiing crane, while still not interfering with the normal operation of the crane when it is being used for heavier loads.

A feature of the present invention lies in the provision of a simple and inexpensive attachment for a standard crane which may be used in conjunction with an extra line to provide a level luffing action on the conventional crane. As a result, a single crane may serve both purposes, and much of the heavy expense involved in having available cranes of both types may be eliminated.

A further feature of the present invention lies in the provision of a simple attachment for cranes which may provide a level lufiing gear for standard cranes, and which may accommodate either a single line with a hook attachment, or a two line clam shell bucket. The attachment is also readily changed in design to accommodate various boom lengths by raising or lowering the tackle suspension point.

These and other objects, and novel features of the present invention will be more clearly and fully set forth in the following specification and claims:

In the drawings forming a part of the specification;

The figure is a side elevational view of a crane, showing the level lufiing attachment in place thereupon.

In view of the large actual size of the crane, the draw ing is not shown in great detail. However, the attach ment is believed shown in suificient detail so that the invention will be clear to those skilled in the art. The particular crane illustrated is of the type known commercially as a Whirley, being mounted at the top of a moveable gantry only diagrammatically shown in partial form in the drawings. The gantry supports a circular track 10, and the base of the crane is circular, and is supported by suitable wheels or wheel trucks 11 so that the crane may rotate about a vertical axis.

States Patent The wheels or wheel trucks 11 support a crane base 12 which is rotatably supported upon the circular track 10 for swinging movement about a vertical axis. A pair of upwardly inclined rear mast portions 13, one of which is shown in the figure, extend upwardly from points 14 on the crane base to provide a mast. A second pair of mast forming members 15, one of which is illustrated in the figure, extend upwardly from point 16 near the forward end of the crane base. The upper ends of the

members

13 and 15 are connected together at the mast top 17. v,

The crane boom 19 is pivotally connected at 20 along a transverse axis at the forward end of the crane platform 12 to extend forwardly therefrom. The lufiing attachment for the crane includes a sheaveblock 21 which is pivotally connected to the mast at the mast top 17 The luffing gear also includes a second sheaveblock 22 which is connected by a fixed length of line 23 to a bridle strap 24 which is hingedly connected at 25 to the boom 19 near the point thereof. The luffing line extends from the luffing drum 26 over a direction changing the sheave 27 on the forward frame portions 15 of the mast, over the outer sheave 29 of the sheave block 22, around the larger sheave 30 of the sheave block 21, back around the sheave 31 of the sheave block 22, next around the sheave 32 of the sheave block 21, and is deadended to the sheave block 22 at 33. Accordingly, when a pull is exerted upon the luffing block 34, the sheave block 22 is drawn toward the sheave block 21, thus, swinging the boom up wardly to position the boom point at a smaller radius from the center of rotation of the crane frame.

The main or heavy tackle of the crane is also conventional. The load line 35 extends from the hoisting drum 36 between a pair of guide sheaves 37 and along the boom to the sheave 39 at the boom point or spaced slightly therefrom. The line 35 then extends down through the load block, and upwardly through the load block 41, the line passing over any desired number of sheaves in the two blocks and being deadended to one of the blocks as is indicated at 42. A hook 43 is shown con nected to the block 40 for supporting a load and the upper block 41 is connected below the boom point by asuitable hanger 44. This main tackle is standard upon cranes of this type and is, of course, capable of lifting extremely heavy loads.

The level luffing attachment for the crane will now be" described. The boom is extended either by a separate ex'- tension 45 or by spacing the sheave 39 at a point spaced from the extreme point of the boom. Frame members 46 extend upwardly from the forward part of the crane body and cooperable frame members 47 are hinged to the mast part 15 at 49 and are connected to the frame parts 46 at 50. A sheave S1 is mounted at this point and a direction changing sheave 52 is provided near the lower ends of the frame parts 46 to guide the load line 53 from the sheave 51 to the load drum 54.

The boom extension 45 supports a first sheave 55 and a second sheave 56. The level luihng line 53 extends from the drum 54 between the guide pulleys 52 and over the sheave 51. From here the line extends over the sheave and back around a second sheave 51 parallel to the first sheave. The line then extends over the sheave 56 and downwardly to the bucket 57 or other load supporting device.

Thus it will be seen that the single part load line is reeved into three parts between the sheave 51 and the sheave 55. The sheave 51 is located at the one point from which the distance to the boom point sheave 55 reduces by exactly one-third the amount that the boom point is elevated as the boom is raised. The location of the sheave 51 is determined by a graphic construction aeeawo employing the fact that the resultant of a vertical force of one combined with a topping force of three must pass through the boom point. As a result of this atrangement, as the boom 19 is elevated, the three part line between the

sheaves

51 and 55 hold the load 57 at a constant elevation from the position shown in full lines to the position shown in dotted lines which represent the point of minimum radius of the load.

Thus as will be indicated from the drawings, if the load comprises a clam shell bucket the load may be lifted to the level shown in full lines and moved horizontally to the position shown in dotted lines so as to drop the load into the hopper 60 which forms a part of the base or support 61 of the crane.

The advantage of this arrangement is believed obvious. Under normal circumstances one type of crane must be used for the lifting of heavy materials so that in such a case it is necessary to use the main tackle of the crane where high loads such as in the nature of ten to one hundred tons are to be lifted depending upon the crane model. However, when loads under ten tons are lifted and where level luifing is desirable for the quick handling of cargo, the level luffing attachment may be employed. Neither tackle affects the use or operation of the other and a single crane is capable either of unloading by level lufiing methods or by ordinary crane operation.

It will be seen that the level luffing attachment is readily adaptable to cranes of the Whirley type and the attachment is merely constructed to properly locate the point at which the sheave 51 is supported relative to the sheave 55. In speaking of the sheave 51 it will be understood that more than one sheave is mounted in side by side relation to accommodate the three part line. In instances where the load line 35 passes about a tackle block and is dead ended at the boom point to form a two part line, the three part reeving is doubled. In constructing the attachment the boom point extension 45 is planned for the end of the boom and the point 50 is located graphically so that the level luffing line 53 pays out the amount which the boom raises.

While the location of the point 50 varies for each crane having a different mast height and boom length, little difficulty is experience in determining the point of location as cranes of the type in question are usually furnished in a series of standard boom lengths and corresponding mast heights.

In accordance with the patent statutes, I have described the principles of construction and operation of my level lutfing attachment, and while I have endeavored to set forth the best embodiment thereof, I desire to have it understood that obvious changes may be made within the scope of the following claims without departing from the spirit of my invention.

I claim:

1. A level luffing attachment for conventional cranes of the type having a base, a mast extending upwardly from the base, a boom pivotally supported upon the base for movement in a vertical plane, means for raising and lowering said boom, a main sheave means carried by said boom, and a main load line extending over said main sheave means, the attachment including a pair of frame members one of which is connected to the crane base to extend upwardly therefrom, and the other of said frame members being connected to the crane mast and extending forwardly therefrom to intersect said first frame member, the frame members being connected together, an extension connected to the upper end of said boom, a first auxiliary sheave means supported at the free end of said extension to form a boom point, a second auxiliary sheave means connected to the intersection of said frame members, a three part auxiliary load line extending between said first and second sheave means, a hoisting drum to which one end of said auxiliary load line is secured, the other end of said auxiliary load line extending downwardly from said first named auxiliary sheave means, said second sheave means being located at the one point from which the distance to the boom point reduces by one-third the amount that the boom is elevated as the boom is raised.

2. A level lufiing attachment for conventional cranes having a crane base, a mast extending upwardly from the crane base, a boom pivotally supported by the base for movement in a vertical plane, means for raising and lowering said boom, a main sheave means carried by said boom, and a main load line extending over said main sheave means, the attachment including a first auxiliary sheave means at the boom point, a frame connected to the mast supporting a secondary auxiliary sheave means, a three part auxiliary load line extending over said first and second auxiliary sheave means, a hoist drum connected to one end of said auxiliary load line, the other end of the auxiliary load line extending downwardly from the boom point, the second auxiliary sheave means being located at the point where the distance between the sheave and the boom point reduces .by exactly one-third the amount the boom point is elevated when the boom is raised, said frame supporting said second sheave means being also detachably connected to the crane base.

3. A level lufiing attachment for cranes of the type having a base, a mast extending upwardly from the base, a boom pivotally supported upon the base for movement in a vertical plane, means for raising and lowering said boom, the attachment including a pair of frame members one of which is connected to the crane base to extend upwardly therefrom, and the other of the frame members being connected to the crane mast and extending forwardly therefrom to intersect the first frame member, the frame members being connected together, an extension on the upper end of said boom, a first sheave means supported at the free end of said extension to form a boom point, a second sheave means connected to the intersection of said frame members, a three part load line extending between said first and second sheave means, a hoisting drum connected to one end of said load line, the other end of the load line extending downwardly from said first named sheave means, said second sheave means being located at the one point from which the distance to the boom point reduces by one-third the amount that the boom is elevated as the boom is raised.

References Cited in the file of this patent UNITED STATES PATENTS 2,082,017 McClain June 1, 1937 2,386,475 Kay Oct. 9, 1945 2,570,417 Wulleman Oct. 9, 1951 2,703,180 Brown Mar. 1, 1955 FOREIGN PATENTS 196,056 Great Britain Apr. 11, 1923 760,662 France Dec. 14, 1933