US2188686A - Luffing crane - Google Patents

Description

Jan. 30, 1940.

B. H. KERSTING ETIAL LUFFING CRANE Filed Feb. 25,1939

4 Sheets-Sheet 1 INVENTORS mam/1% yM Z'ZM Ja n. 30,1940- 5. H. KERSTING ET AL LUFFING CRANE 4 Sheets-sheaf 2 Filed Feb. 25, 1939 Jan. 30,

B. H. KERSTING ET AL.

LUFFING CRANE Filed Feb. 25,- 1939 4 Sheets-Sheet I5 J-.r IHZ 32 INVENTORS Patented Jan. 1940 UNITED STATES PATENT OFFICE Coraopolis, Pas assignors to Dravo Corporation, a corporation of Pennsylvania Application February 25, 1939., Serial No. 258,534

9 Claims.

This invention consists in means for swinging pivotally mounted structures; and, while it is of general applicability, we have developed it in application to the swinging of the jib of a crane,

and in such application we shall particularly describe it. The swinging in vertical plane of the jib of a crane is technically called luiiing. This lufling of the jib of 'a crane is commonly 'accomplishedby means of pulley and cable. The

l0 means of this invention involvethe use of screw and nut. The objects in vieware simplicity of structure and facility, speed, and accuracy of operation.

In the accompanying drawings Fig. I is a view I! in side elevation of a gauntry crane of turret type mounted to travel upon' rails, in which the lufling means of our invention are employed; Fig. II is a view to larger scale and also in side elevation, showing fragmentarily the crane, and

showing in greater detail the lufling mechanism;

Fig. III is a fragmentary view, showing the luffing mechanism in plan; Figs. IV and V are views in ems-section, showing the luiiing mechanism to still larger scale on the planes respectively indicated at IV-IV and V-V, Fig. II; Figs. VI and VII are views in axial section and in end elevation of a certain nut and bearing assembly, and Fig. VIII is. a view partly in side elevation and partly in axial section of such assemao Fig; IX is a fragmentary view, showing in axial section, on larger scale than Figs. VI to and bearing assembly; and Fig. X is a diagrammatic view in side elevation 011a draw-bridge which includes a pivotally mounted element,

and to which application is-made'of the swinging means of the invention.

The gauntry crane of Figs. I-VIII ,afiords example of the practice of the invention; the

invention is in no sense limited to this or any other particular form or type of. crane; and, as is manifest on consideration of Fig. X, it is of general applicability in the swinging of pivotally mounted structures. k

The crane stands upon a base I (in this instance a platform mounted to rotate turret-like upon a derrick 2). It includes a jib 3 pivoted to the base at 4 and adapted to swing in vertical plane upon such pivotal mounting. Such swinging in vertical plane is, as has been said, termed lumng. From a drum 5 rotatably mounted in base I a hoist line Ii extends throughout the length of the jib and supports in a suitably formed. bight a block 1. Upon' this block the ll load is hung. It does not concern us further (Cl. 21H) to describe details and refinements of load carry- .ing.'

The jib 3 of the crane will be seen to be a trussv structure, of general triangular outline, pivoted by'one comer of the triangle'upon the 5 base I, and itself including a basal chord memher 8. This chord member 8 of .the arm" is pivotally connected at one end to the base I A third member, ascrew 9, is through'intermediate parts presentlrtobe' described, pivoted at one in of its ends tothe distal end of the pivotally mounted member 8 (at point I0) and at its other end (through intermediate parts) to base I at a point II, remote from pivot 4. The base I, the chord member 8, and the screw-9 thusform a It triangle (called in the industry an A frame). Of this triangle of members, the effective length of one (the screw 9) is variable: and by, variation in the effective length of this member the frame is swung and luiiing is effected. 2o

The screw 9 is oppositely threaded at its two ends and can'ies upon its oppositely threaded ends twp oppositely threaded nuts, I2 and. I3. The nuts'are pivotally mounted; in pairs of links I4, I and I5, I5 that move .in a runway 25 in a frame I6, and in their mounting are secured against rotation. These links are pivoted, one pair to arm 3 at III, the other pair to base I at II. It is manifest, then, that as screw 9 is rotated in one direction or the other and the '39 I pairs of links drawn together or spread apart, VIII, the internally threaded portions of the nut the effective length of the screw as a member of the A frame is diminishedor increased, and the arm 3 is swung upward or downward. The

positions illustrated in full lines .and inbroken .35 lines in Fig. I indicate the shifting ofposition of the parts. The range of swing is not limited to the positions shown,.but is of much wider extent.

The screw' 9 may be equipped with a gear- 40 wheel I1, and the frame I6 with a motor I8, by

' which through suitable transmission mechanism rotation in desired direction, at proper speed,

and to desired extent may be imparted powerfully to screw 9. The frame I6 is'assembled with the links I 4,

. I, I5, I5, and affords a floating runway and torsion-resisting member for the links and a sup port for the motor I8. structurally the frame includes two-parallel beams I60. spaced apart r," and rigidly integrated with cross-struts ISI. The screw .9 extends between the beams I60, and at opposite ends is journaled in bearing blocks. thatare secured. against. axial displacement,

by means of keepers I62 rigid with the frame. 5

The inner faces of the beams I60 carry longitudinal rails 26, upon which the links I I, I I and I5, I5, when assembled'with .the nuts, are adapted to travel. The structure holds the links (and the cups 23 presently to be described) against rotation. The links include lateral projections I II, II that are notched to engage the rails 26,

as shown in Fig. IV; and between the paired links the nuts I2 and I3 are severally mounted. 4

Provision is made for the distribution of stress between nut and screw. The practical limitations upon the degree of perfection attainable in the preparation of materials and-in the fabrication of parts give value to this provision. The nut has gimbal mounting in the pairs of 7 links; and, accordingly, under stress transmitted between screw and link, the nut adjusts itself .upon the screw, and stress that might otherwise be concentrated at one point is distributed around the circumference of the interengaged threads. The gimbal mounting is found in a cylindrical cup 23 with a bottom orifice through which in the assembly the screw 9 extends, and within which the nut is arranged. Externally the cup is provided with trunions 24 by which it is pivotally mounted in the associated pair of links (I4, I4 or I5, I5)., Internally the. cup is provided with transversely extending cylindrical bosses, conveniently formed as pins 25 welded in orifices in thecup walls. The axes of trunions 24 and of pins 25 are angularly displaced at a 90 angle,

immediately provided with the bearingsurfaces to engage the pins 25. The two partsare united against relative rotation by the spline 22.

Upon the part 2| a supplementary nut 30 is mounted bybolts 3I-,- and by" such mounting is minutely adjustable in its position. The supplementary nut 30- is provided upon its outer face (the face that in the assembly is remote from the nut 20, 2 I) with an outstanding diametrically extending ridge 32 of a width less than the overall diameter of the screw 9. The threads within the nut 20 are so proportioned as to fill the complementary threads in the screw 9; the threads in the supplementary nut 30 are so proportioned as toafford a small play between the opposed surfaces of the threads. When the parts are initiallyassembled, the faces of the threads in nut 30, which-otherwise would hear the stress of service,

. stand away from the thread on the screw 9. In

consequence, it is the nut 20 that primarily bears the stress of service. As in continued use the interergaging surfaces wear away, the space narrows at which the thread surfaces of the supplementary nut 30 stand apart from those of the screw. The narrowing of this space is visible as through a window at the sides of the ridge 32; and thus a tell-tale is provided, by which deter:

'mination may be made, when the nut 20 is so far worn as to require replacement.

Manifestly, it is only the reach of the screw 9 between the nuts I2 and I3 that is subject to the tension stresses of the load, and, of course, if the screw breaks, it will break at some point in the interval between the nuts. In the event of such screw failure, the two ends of the screw severally extending between the nuts I2 and I3 and the thrust blocks 90 at the opposite ends of the frame I6, become compression members, and transfer through the keepers I62 to the body of the frame I6 the load-sustaining tension, normally borne by the portion of the screw between the nuts. Thus, the frame I6, normally serving as a runway and motor support, is adapted in emergency to be come the effective load-sustaining member, preventing undue harm to the apparatus, and serious danger to workmen.

The nuts 20 will normally be formed of bronze;

but the supplementary nuts 30, serving their described purposes, not of tell-tale merely, but, if

for any reason the threads in the bronze nuts 20 fail, of compression members also, will advantageously be formed of steel of high shear strength.

The screw is supported in the frame" by the nuts, and at the ends there is suflicient normal clearance from blocks 90 to allow for wear between screw and nuts.

The structure allows the screw to float in the nut assemblies I2 and I3, and, as has been said,

the stress is distributed over the engaging surfaces around the circumference of the screw.

Already we have said that the screw 9 floats in the frame IS, in that it is mounted in blocks that have universal pivotal mounting in the frame. Furthermore, it will be observed that the frame I6- floats, in thesense that, in addition to its pivotal movement upon points III and I I, it has movement of longitudinal translation relatively to base I and arm 3. Such movement is indicated in the broken-line position, Fig. I.

The operation of lufiing is effected by rotation of screw 9 with the effect that the pairs of links I4, I4 and I5, I5 are-drawn together or spread apart; the effective length of one arm of the A-frame is diminished or increased; and arm 3 is raised or-lowered. In case the screw 9 breaks under load, the frame I6, through the keepers I62, becomesthe tension member, sustaining the load.

shown, consisting of two halves '40 severally mounted pivotally upon opposed bridge-heads 50, and adapted to be swung severally from full-line to dotted-line positions. In this case also each bridge half is in structure a truss that includes a chord member 80. Between the distal end of chord 80"(the end remote from the point of pivoting) and a pivot mounted on the bridgehead 50 at an interval from the pivotal point I0 of the chord member 80, such a structure as that already shown and described may be introduced. And, by means of such a structure, the draw-bridge halves may be raisedand lowered.

Whereas the bridge illustrated consists in two pivotally mounted bridge sections that are 'adapt ed to be swung severally between horizontal and elevated positions, the art is familiar with draw In'Fig. X a draw-bridge is diagrammatically bridges that have a single member that is adapted to be swung in vertical plane. Manifestly, the structure of the invention may be also employed in bridges-of this sort.

In like manner, as will be understood, the invention may be applied to the swinging o f-the gates of locks in canals; and, generally, in the swinging of pivotally mounted structures.

We claim as our invention:

1. Means for swinging a structure" pivotally tation to effect the drawing together of the nuts and of the carriages that bear them.

2. The structure of claim 1, the gimbal mountings including each a cup being pivotally mounted in one of said carriages on an axis transverse to the axis of the screw and each cup being additionallyadapted to be pivotally engaged by the nut on an axis of turning also transverse to the screw axis and angularly displaced (with respect to the screw axis as a centre) from the axis of pivotal mounting first named.

3. In a crane structure including an arm in the form of a truss with basal chord member, pivotally mounted at one end of such basal chord member to an extended base, lufiing means,.including a frame with longitudinally extending runway, two oppositely threadednuts mounted in said runway, one of said nuts being pivotally connected to the basal chord member of 'said arm at a point remote from the point of pivoting to the said extended base, and the other of said nuts being pivoted to the said extended base'at a point remote from the said point of the pivoting of the arm upon it, and a rotatable bolt formed with oppositely threaded portions simultaneously engaging the two said nuts.

4. In a crane including an arm pivotally mounted upon a base, lufling means, including a frame with longitudinally extending runway-two links adapted to travel in said runway, two nuts mounted with universal pivotal connection, one to each link, a screw extending longitudinally of said frame and engaging the nuts in said links, one

of said links being pivotally connected to said arm at a point remote from the point of pivotal mounting upon the base ,and the other of said carriages being pivotally connected'to said base -at a point remote from the-point of pivotal mounting of the arm upon it.

5. In a crane including 'an arm pivotally mounted upon a base, lufling means, including a frame-with a, longitudinally extending runway, two links adapted to travel in said runway, two nuts mounted with universal pivotal connection, one to each link, a screw extending longitudinally of said frame and engaging the nuts in said links,

one of said links being pivotally connected to said arm at 'a point remote from the point of pivotal mounting upon the base, and the other I of said links being pivotally connected to said base at a point remote fromthe point of pivotal mounting of the arm upon it, and means for rotating said shaft to vary the space interval between said links.

6. In a crane including an arm pivotally mounted upon a base, lufiing means, including a screw carrying two nuts connected, one to said arm at a point remote from the point of pivotal mounting upon the baseyand the other to the base at a point remote from the point of pivotal mounting of the arm upon it, and a floating frame borne by and providing runway for said nuts.

7. In a crane including an arm mounted upon a base, lufling means, including a frame with a longitudinally extending runway, two nuts adapted to travel in said runway, a screw extending longitudinally of said frame and engaging the said nuts, one of said nuts being pivotally connected to the said arm at a point remote from the point of pivotal mounting upon the base, and the other of said nuts being pivotally connected to said base at a point remote to the pivotal mounting of the arm uponit, the said frame being provided with abutments beyond the two ends of said screw in such assembly,, whereby, in case of screw failure, the frame becomes, a tension member sustaining the load.

8. In a crane including an arm pivotally mounted upon a base, means including a screw and a traveling nut for swinging said arm in vertical plane, anda frame including a runwayfor said traveling nut, said frame. carrying an abutment adapted, in case of screw failure, to be engaged by said screw and to transmit the load stress to said frame.

W 9. Means for swinging a, structure pivotally mounted upon a support, such means including a frame, two nuts rotatably borne by said frame and pivotally connected, one to the swinging structure and the other to the support, a screw simultaneously engaged by the two said nuts and adapted on'rotation in one direction or the other to effect the drawing together or the recession of the nuts from one another, a prime mover borne by said frame, and rotation-imparting connection between said prime mover-and said screw BERNARD H, KERSTING. HANS ENARD.

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