US3032322A

US3032322A - Portable spar with counter-balance mechanism for bias-mounted head block

Info

Publication number: US3032322A
Application number: US69882A
Authority: US
Inventors: Frank L Lawrence
Original assignee: AERIALMATIC CO Ltd
Current assignee: AERIALMATIC Co Ltd
Priority date: 1960-11-17
Filing date: 1960-11-17
Publication date: 1962-05-01
Anticipated expiration: 1979-05-01

Description

May 1, 1962 F. L. LAWRENCE 3,032,322

PORTABLE SPAR WITH COUNTER-BALANCE MECHANISM FOR BIAS-MOUNTED HEAD BLOCK Filed Nov. 17, 1960 2 Sheets-Sheet 1 r w I l! l 2 ,L m /s ,l I .1 2,

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ATTORNEYS May 1, 1962 F. L. LAWRENCE PORTABLE SPAR WITH COUNTER-BALANCE MECHANISM FOR BIAS-MOUNTED HEAD BLOCK 2 Sheets-Sheet 2 Filed Nov. 17, 1960 FIG.2

MPUQ ATTORNEYS ire States ada Filed Nov. 17, 1960, Ser. No. 69,882 10 Claims. (Cl. 254-190) This invention relates to portable spars of the type in which the main or haulback sheaves, or both, are located at the head end of the spar, receiving support from a head block having its hub journaled for swivel movement about a generally vertical axis.

The spar of the present invention is one in which the swivelled hub of said block is hollow and the main and haulback cables lead downwardly from the respective sheaves through the hollow center of the hub and thence through an opening in the wall of the spar to the spooling drums of a yarder. The erected spar occupies substantially a vertical position. The spooling drums are spaced horizontally from the baseof the spar and this perforce dictates for the cables a path angular to the vertical if the cables are to run rub-free between the spooling drums and the'sheaves. To insure this rub-free path the head blocks swivel axis is biased from the vertical to bring the hollow center into line with the wall opening. Since the overhang of the fairleader head block and its sheave establishes for such head block a weight center which is offset from the swivel center, the main sheave carried by the head block normally tends to gravitate into an established position. This is perforce undesirable when the direction in which the main cable runs out from the spar is angular to the direction in which the sheave points by force of gravity. A conflict arises between the pull force exerted on the head block by the main cable, to align the head block with the vertical plane in which the cable is working, and the countering force of gravity. This causes the cable to drag against a flange of the sheave, developing frictional losses and increasing wear on the cable, the sheave, and the journals.

The present invention has for its general object to provide a portable spar of the nature described embodying a mechanism counterbalancing force of gravity imposed upon a head block swivelled to turn about a biased axis.

This and other more particular objects and advantages will appear and be understood in the course of the following description and claims, the invention consisting in the novel construction and in the adaptation and combination of parts hereinafter described and claimed.

In the accompanying drawings:

FIGURE 1 is a fragmetary vertical sectional view illustrating the head end of a portable spar engineered to embody the preferred teachings of the present invention.

- FIG. 2 is a fragmentary elevational view thereof including an illustration of the main and haulback sheaves which surmount the spar, the scale being reduced from that of FXG. l; and

FIG. 3 is a fragmentary vertical sectional view employing the same scale as that of FIG. 1 and detailing the thrust-and-journal mounting for the upper end of the head blocks swivelled hub.

Referring to said drawings, the numeral 5 designates the hollow upper section of a portable spar. Stabilizing guy lines (not shown) run from stumps or other suitable ground anchors to connectors 6 hung from an anchoring ring 7 which surrounds the spar section and bears upon a thrust ring 8 welded or otherwise fixedly secured to the spar section. Below said thrust ring an elongated opening it is provided in said spar section for the accommodation of main and haulback cables running from powerdriven spooling drums to respective sheaves 11 and 12. A self-aligning block 13 which carries the main sheave 11 is mounted at the head end of the spar for swivel movement about a generally vertical axis, and a self-aligning block 14 for the haulback sheave 12 is in turn mounted at the head end of the block 13 for swivel movement about a coinciding axis. The swivelled hubs of said blocks are made hollow to accommodate the cables, and the axis about which the hubs swivel is set at a moderate angle from the center line of the spar in order that the cables will pass, rub-free, through the wall opening ill. This angularity is shown as 8. The swivel mounting for the main block 13 is provided by welding an adapter pipe 15 in the head end of the spar section and fitting this pipe with a journal bushing 16 at the bottom and a thrustand-journal bushing 17 at the top.

' Such main block projects by its lower end moderately below the adapter pipe. An open annular crown cam 18 is bolted or otherwise rigidly secured to said projecting lower end with its camming surface facing downwardly. Said camming surface is regular, being developed with. substantially a'uniform rise in both directions between; high and low points which are at 180 from one another.

' A roller 21, journaled between the fork-arms 22 of a.

yoke for rotation about an axis radial to the cam, rides on the cam and is yieldingly pressed against the latter by a spring 23. The spring used is an open spiral spring opposing compression, and exerts its thrustload through a ball-joint connection 24 to a vertical slide 25 presenting at its upper end the yoke which supports the roller. A guide 26, for vertical reciprocation of the slide along an axis paralleling the swivel aXis of the block 13, is made an integral part of the spar section.

' Considering low and high as the cam. surface which is remote or proximate, relatively speaking, to the level occupied by a stationary bottoming disk 27 from which the spring 23 takes its purchase, the roller is so located that it rides upon the high point 28 of the cam when the main sheave 11 hangs in a position dictated by gravity. This is the position in which the sheave is shown in the drawing. As the vertical plane of the sheave shifts to one sideor the other in consequence of running the main line on a course angular to said gravity-dictated plane, the roller responsively works toward the cams low point 29, ultimately occupying the latter when the main line runs out from the spar at 180 to the initial position.

The turning moment exerted upon the cam by the springloaded roller is perforce zero at either of these points in that the roller is occupying a level surface, so to speak.

- The maximum turning moment which the roller exerts obtains when the cam has moved the slope of the cam then being at its maximum. The directional influence of this turning moment is perforce toward the low point 29 and the design of the cam is such that this moment equals the oppositely directed turning moment due to the ofi-center mounting of the main sheave block.

The load exerted by the spring upon the cam is approximately equal to the total weight of the main and the haulback sheave assemblies plus an allowance for the weight of the cable carried by each sheave. The cam is designed so that, as the main sheave block shifts to any position, the spring-loaded roller 21 exerts upon the cam a turning moment equal to the turning moment which reflects the degree to which the weight center of the sheave assembly is laterally removed from a plane radial to the swivel axis of the sheave block into which said weight center normally tends to move by the influence of gravity. This turning moment, to reiterate, varies from zero when the main sheave block occupies either the position in which it is shown or lies diametrically opposite therefrom, and increases to maximum when moved to a position at right angles thereto.

It is believed that the invention and the manner of its working will have been clearly understood from the foregoing detailed description of my now-preferred illustrated embodiment. Changes within the spirit of the invention will suggest themselves. It is my intention that no limitations be implied and that the hereto annexed claims be given the broadest interpretation to which the employed language fairly admits.

What I claim is:

1. In combination with a portable spar having a hollow top section provided with an opening in the wall, a block having a hollow hub journal-mounted in the head end of said top section above the wall opening for swivel movement about an axis so biased from the vertical center of the erected spar that a cable will pass rub-free from the hollow center of the hub through said wall opening to the spooling drum of a yarder occupying a ground position adjacent the base of the spar, a self-aligning sheave over which said cable is fed to said hollow center of the hub carried by the block and influencing the latter when the spar is approximately vertical to gravitate in one direction by oft-center distribution of weight, and means operatively connected with the block exerting thereon a force counter-balancing said force of gravity.

2. Structure according to claim 1 in which said block is given a journal mounting at its lower end and a thrustand-journal mounting at its upper end.

3. In combination with a portable spar having. a hollow top section provided with an opening in the wall, a block having a hollow hub journal-mounted in the head end of. said top section above the wall opening for swivel movement about an axis so biased from the vertical center of the erected spar that a cable will pass rub-free from the hollow center of the hub through said wall opening to the spooling drum of a yarder occupying a ground position adjacent the base of the spar, a self-aligning sheave over which said cable is fed to said hollow center of the hub carried by the block and influencing the latter when the spar is approximately vertical to gravitate in one.

direction by ofif-center distribution of weight, a crown cam fixed to said block concentric to the swivel axis, the development of said cam being regular with a single high and low point placed diametrically opposite to one another, and a spring-loaded roller bearing against said cam and so placed as to occupy the high point of the cam when the sheave is pointed in said direction in which it is gravitationally influenced.

4. Structure according to claim 3, said roller being guided for reciprocal motion along an axis paralleling the swivel axis of the block, the spring load being imposed through a ball-and-socket joint.

5. In a spar, in combination. with a head block carried for swivel movement by the spar with its, swivel axis so placed as to be biased from the vertical upon erecting the spar to have the same occupy a predetermined position and having mounted upon said block a self-aligning sheave characterized in that its weight distribution in said erected condition of the spar is off-center in relation to the swivel axis and hence imposes upon the sheave a gravitational force tending to swing the sheave in one direction, co-acting means carried by the spar and the block exerting from the spar upon the block a force component working counter to said force of gravity.

6. In a spar, in combination with a head block carried for swivel movement by the spar with its swivel axis so placed as to be biased from the vertical upon erecting the spar to have the same occupy a predetermined position and having mounted upon said block a self-aligning sheave characterized in that its weight distribution in said erected condition of the spar is oil-center in relation to the swivel axis and hence imposes upon the sheave a gravitational force tending to swing the sheave in one direction, co-acting spring-loaded means carried by the spar and the block exerting from the spar upon the block a force component approximately counter-balancing said force of gravity.

7. In a spar, in combination with a head block carried for swivel movement by the spar with its swivel axis so placed as to be biased from the vertical upon erecting the spar to have the same occupy a predetermined position and having mounted upon said block a self-aligning sheave characterized in that its weight distribution in said erected condition of the spar is oft-center in relation to the swivel axis and hence imposes upon the sheave a gravitational force tending to swing the sheave in one direction, co-acting means one carried by the block and the other by the spar exerting upon the block a turning moment working counter to said force of gravity, one of said means comprising a crown cam fixed to said member by which it is carried in a position concentric to said swivel axis of the block.

8. A spar according to claim 7, said means which coacts with the cam comprising a roller riding on said cam guided for reciprocal movement in. a direction paralleling the swivel axis of the block, and a spring under compression-loading pressing said roller against the cam.

9. Structure according to claim 7, said cam being a regular cam developed so that the counter force exerted is a turning moment approximately equaling the turning moment due to said oft-center distribution of weight.

10. In a spar, in combination with a head block carried for swivel movement by the spar with its swivel axis so placed as to be biased from the vertical upon erecting the spar to have the same occupy a predetermined position and having mounted upon said block a self-aligning sheave characterized in that its Weight distribution in said erected condition of the spar is off-center in relation to the swivel axis and hence imposes upon the sheave a gravitational force tending to swing the sheave in one direction, a crown cam fixed to said block concentric to the swivel axis, the development of said cam being regular with a single high and a single low point placed diametrically opposite one another, and a spring-loaded roller carried by the spar bearing against said cam and so placed as to occupy the high point of the cam when the sheave is pointed in said direction in which it is gravitationally influenced.

References Cited in the file of this patent UNITED. STATES PATENTS 964,035 Lombard July 12, 1910