US752248A

US752248A - Crane

Info

Publication number: US752248A
Authority: US
Publication date: 1904-02-16
Anticipated expiration: 1921-02-16

Description

PATBNTED FBB 16, 1904.

E. NIGKERSON.

CRANE, APPLICATION FILED MAY 8, 1903 5 SHEETS-*SHEET 1- N0 MODEL.

W/TNESSES "PTBNTED PBR-16,1904.

.E NIUKERSON.

CRANE.

APPLIoATIoN FILED my a, 1903,. r

.5 SHEETS-SHEET 2.'

No MODEL.

W/ TNE SSE S A TTOHN'E Y I Y PATENTBD ma'. 1'6, 19o-4.

E.V NIGKBRSON.

' CRANEl l APPLmATIoN'rILBD MAY s. 1903.

a SHEETS-snm' a.

N0 MODEL.

m: wams Firms co. mom-umh. WASHINGTON. o. c.

PATENTD FEB. 16, 1904.

E. NIGKERSON.

CRANE.

APPLIUATION FILED MAY a, 1903.

5 SHEETS-SHEET 4.

N0 MODEL.

qv vE/vron W/TNESSES A from/Ey No. 752,248. PATENTBD ma. 16, 1904. v @.NIGKERSON.

` CRANE.

APPL'IOATION FILED MAY 1903.

No MODEL.

5 SHEETS-SHEETS.

Y I A Tron/VH .l

UNITED STATES Patented February 16, 1904.

PATENT OFFICE.

CRANE.

SPECIFICATION formngpart of Letters Patent N o. 752,248, dated February 16, 1904. Application filed May 8, 1903. Serial No. 156,217. (No model.)

lLocrZZ whom, tm/ay core/cern.-

Beit known that I, ERNEST NioKERsoN, a`

citizen of the United States, and a resident of Newton, in the county of Middlesex and State of Massachusetts, have invented a new and useful Improvement in Cranes, of which the following is a full, clear, and exact` description, reference being had to the accompanying drawings, forming a part of this specification, in explaining its nature.

The invention relates to an improvement in cranes and to that kind of crane where an automatically moved counterbalancing weight is provided to offset the weight of the load or object lifted.

The invention consists in an improved means whereby the movement of the counterbalancing-weight may be automatically obtained by utilizing the power of the thrust caused by the-load acting through the boom by which it is supported and developed at its seat or point of jointure to the fixed part of the crane.

The invention further consists in means whereby the crane provided with such coun-l terbalance may be protected against the strain arising from its extreme weight in case the object to be lifted should suddenly become detached from the crane by the breaking of a chain or fline or other intermediary support, especially when the strain ofthe load is first put upon the crane, and which strain'of the counterbalance unless provided against would be equally as disastrous upon the crane as the weight of the load would have been without the counter-acting iniiuence of the counterbalance, and even more so, owing to the sudden shock.

Figure 1 shows my improved crane structure in elevation. Fig. 2 shows in plan a detail thereof, to which reference will hereinafter be made. Eig. 3 shows in horizontal section a detail of my construction, to which reference will hereinafter be made. Eig. 4. shows the improved crane inI plan looking down upon the same. Eig. 5 shows in elevation the structure and correlation of the braces, to which reference will hereinafter be made.' Fig. 6 is a longitudinal vertical section upon the line 6 6 of Fig. 7. Fig. 7 shows in plan a modified portion of the structure, to which reference will hereinafter be made. Eig. 8 is a view of one of the concave steps shown at o in Fig.`l. Eig. 9 is a cross-sectional detail AView taken at the top of the adjustable braces.

. turn-table A' is shown fixed to a `movable truck A2. Rising from the main body of the crane is the mast a. a represents the jib or boom extension. For sustaining the boom, raising or lowering it, or for changing its inclination there is shown the chain or line a2, having suitable sheave or pulley attachments, and which chain or line is controlled in any suitable manner. as represents the hoisting rope or chain. This rope or chain has the usual sheave a pulley attachments, by which 'its lifting stress can bestbe utilized. The hoisting rope or chain connects with a drum or windlass turned by hand or power. These elements just referred to i are common to all cranes and require no further reference or explanation.

Extending from the main body of the crane is the overhang A3, which carries the counterbalancing-weight A4. The overhang comprises girders suitably braced and at the back end of which stays a4 are secured, which connect with the top of the mast a. Along the bottom of the overhang the iianges a5 are extended, upon which is laid the track a, extending on an upward incline from the main body of the crane. Running on this track and supported by suitable wheels or trucks is the counterbalance A4, which must be of suiiicient weight to counterbalance the load to be lifted when run out to some relative position upon the track a6. The normal position of the counterbalancing-weight A4, by reason of the inclination of the track upon which it runs, v would be, close in against the main body of the crane or in a position approximately over the base of its support, where it would cause the least strain when there was no load upon the crane. For moving the counterbalance along the track to a position where it will as nearly as possible balance that of the load to IOO be lifted there is utilized the force of the thrust caused by the load acting through the boom by which it is supported. In other words, the relation of the boom to the load is such that the weight of the load causes a thrust of variable intensity, dependent upon the weight of the load and the inclinationof the boom, to be developed in the boom at its seat or point of jointure with the fixed body of the crane, and which thrust is utilized and usedy as a source of power by making the end of the boom movable, then through suitable means of transmission applying it to the counterbalance to move it to its correct position or where it will as nearly as possible offset the weight of the load. Various expedients may be resorted to for transmitting the power so obtained to the counterbalance either by application through hydraulic or pneumatic pressures or by application through mechanical means, as gears, levers, and the like, or the application of the thrust to the setting of valves or other methods of control acting upon forces generated for the purpose of moving the counterbalance to its correct position, all of which means would be within thel essence of my invention looked at in its broader significance. As illustrative further of such transmittory means and as tending to the reduction of the invention to a working basis there is provided a means whereby hydraulic pressure is the instrument for transmitting the power of the thrust. The means may be eected as follows:

There is formed in the fixed body of the crane a chamber B, the back end and floor or base of which are made solid with a stability suiiicient to withstand any strain subjected by the lower inner end of the boom, which rests within this chamber, as its seat or base of support. For the purpose of utility, as will hereinafter appear, the lower end of the boom contained within the chamber B is made cleft with feet Z2 b', which take the form of flanged castings, to which the cleft ends of the boom are pivotally or otherwise secured. These castings or feet are supported against a lateral displacement or working by side guides b2 52. They carry rollers b3 3 upon their bottom sides, the axes of which rollers are at right angles with the central line of the boom. The rollers rest to move with a limited degree of movement upon the floor or base of the chamber B or any other table of support'formed thereon wherefore the sliding horizontal movement or thrust to the end of the boom is obtained. y

Within the chamber B, and preferably formed between the cleft ends of the boom, are the cylinder-chambers 64 b4 if, the headed ends of which butt against the inner wall of the said chamber. There are three of the cylinder-chambers shown; but this number is arbitrarily taken. Each cylinder-chamber has its piston b5, which pistons are simultaneously driven by the movable thrust end of the boom.

This result is obtained through the medium of what may be termed the equalizer-bar 5G. The rods of the several pistons are secured to this bar,I so that with the movement of the bar their simultaneous movement is obtained and the equalizer-bar is actuated by the thrust end of the boom, to which it is secured at either end by eyebolts or links 127, connecting with the cleft ends of the boom, and preferably by the same fastenings by which the same is secured to their respective feet b b'. Of coursewith this order of arrangement it is necessary that the equalizer-bar be actuated by the boom to move with a true even movement, in order that there may beno torsional strain or cramping of the piston within their respective bearings. For obtaining such movement the simple mechanical expedient is resorted to of fixing the beam bs or other stiffener-bar in the front of the body of the crane in the same plane as the equalizer-bar and in a position to define its true parallel line of motion. Interposed between the stiifener-bar and the equalizer-bar is the guide-bar Z2, connected to both bars by links or toggles Z210, and which guide-bar through the restraining action of the toggles equalizes the strain and causes the equalizer-bar to always move parallel with the stiffener-bar in the front of the crane or in a true line of movement, and so to simultaneously and uniformly actuate the pistons within their cylinder-chambers. The cylinder-chambers are filled with any incompressible iuid. Connecting with the vchambers are the passages b, whereby the liquid pressure within the chambers may become equalized. Within the wall of the middle chamber is a vent 7112, connecting with which IOO is the pipe 513, leading to a secondary cylinderchamber C. The chamber C is formed in the front of the main body of the crane. It is made cylindrical in shape and is left open at its rear end leading toward the counterbalancing-weight and from which end when projected extends what may be termed a telescopic hydraulic ram c, which is contained within this chamber. The hydraulic ram c consists of a number of telescoping tubes, the

Aforward end of which when the ram is in outward extensionis left closed. The forward end of each tube is flanged, and the placement of the flanges or the length of the tubes is so graduated that when the tubes are retracted into the chamber C the back edges of the tubes will all lie in the same plane. The telescopic ram of course is used for pressing the counterbalancing-weight A4 back along its inclined trackway and for holding it in a position where it will serve to counterbalance the weight to be lifted, as before explained. The ram accordingly is placed so as to contact with the rear end of the counterbalancingweight and to extend in the same line of direction that the weight is-moving, so that the contact of the ram against the rear end of the counterbalancing-weight is maintained at all TIO ' bottom of the overhang and which are so made that each Vstep will guide and serve as a stop for a corresponding sectional tube of the ram, which, together with the fact that the cylinders or tubes comprising the ram are so proportioned that it will be extended to press forward the counterbalance to apoint where it will as nearly as possible balance the load to be lifted, can better be understood by explaining the mode of operation governing the parts previously referred to. first instance the weight of the object raised causes the lower end of the boom to move or rather be thrust backward. The rolling feet, the horizontal basal support, and guides all facilitate this movement and confine it to a straight line parallel with the center line of` the crane. The toggles and connecting-bars also guide the movement and tend to equalize The equalizer-bar transfers the movement to the pistons, whereby they are pressed forward uniformly lin their respective cylinder-chambers.v Thus the horizontal component of the boom thrust is conveyed to the liquid behind the pistons in their respective cylinders. This liquid, which may be water, oil, or any suitable fluid, will then be forced from all the chambers by reason of their connecting-passages through the pipe connection to the secondary cylinder-chamber, where it will act upon the piston formed-by the rear end of all the sections to the telescopic ram, which is contained within this secondary cylinder-chamber, as before explained, and will push them backward, carrying with them the counterweight until the largest section or part reaches the end of its corresponding concave step or guide and stops. If then the pressure on the rear ends of the remaining sections is sufficient to overcome the resistance of the weight `of the counterbalance acting along the incline on which it runs, the remaining sections will move forward until the next size cylinder is stopped by the end of its concave step or guide, and so on. the total pressure on the remaining free sections equalizes the force necessary to move the weight of the counterbalance on its incline, the movement finally stops. The cylinders must be so proportioned that` this stoppage will occur when the weightof the counterbalance as nearly as possible balances the weight of the load to be lifted. When the load is lifted, it will be noted that the movement of the boom-foot allows the boom to lower slightly. Thus the load will not be raised from the ground until the counterbalance is extended to a position where it will balance the weight of the load. In lowering the weight a reverse operation-to that just detailed for the primary action of the cylinders will take place.

In the .r

When

The weight of thecounter-` balance acting along itsinclined track will shut back the telescoping sections of the ram into the secondary cylinder-chamber in which they are contained. Simultaneously with'the closing back of the telescoping sections the iiuid which each section contains will be forced back into the secondary chamber and thence into the primary cylinder-chambers, vwhere it .will drive back the pistons, which through the intermediary of the equalizer-bar connecting-links will carry back the end of the boom where it will be in a position to be actuated by the weight of the next load.

It will be understood, of course, as before referred to, that the normal position of the counterbalance is at the bottom of its inclined trackway, so that it will consequently press back the telescoping sections of the ram until they are all contained within the secondary cylinder-chamber and in a position to be acted upon by the influence of the next fiuid charge.

As tending to the further perfection of the crane, which has a counterbalancing-weight, there is shown in Figs. l and 5 a means tending to guard the crane against the strain of the weight of the counterbalance in case the chain or other means adapted to attach the object to be lifted, or even the hoisting-line itself, should break when the load is first to be upon it. Of course when the counterbalance is moved out on the overhang, away from the base thereof, should the line break and the vweight of the counterbalance be so suddenly deprived of the balancing effect of the load that it is unable to move in toward the base rapidly enough to avoid an overturning action then its strain upon the crane would be equally as disastrous as the weight of the load would be without the counteracting iniiuence of the counterbalance, and even more so,`owing to the sudden shock. Accordingly there arefixed at the end of the overhang, and preferably at either corner thereof, what may be termed adjustable braces connecting with the ground or any other fixed base of support. n"The adjustable braces are made alike. Each comprises a case 0l, fixed to the overhang and braced to hang in a vertical position.` `Eachcase CZ is tapped on its inside bore with a female thread. Fitting into the threaded bore of the case is the hollow screw d', which is also threaded on its inside to receive the screw d2, which threads on vthe interior of said screw for receiving the screw Z2 run in a direction so reverse to the threads on the outside of said screw, which fit into the case d, that the two screws d Z2 are moved up or down by turning them in reverse directions, this for purposes as will hereinafter appear. The screws d are braced against else than a which extend back and at their upper ends are secured to the under side of the overhang and at their lower ends to the attaching members lOO` IIO

IZO

di, which are suitably bored and threaded to fit each its screw, and by the sets of braces d5, which connect with the adjacent screws d' across the back end of the overhang. The bracesd? connect with each one ofthe screws d' at two points in order to secure an added stability of structure and also so that the braces may move simultaneously with the screws and turn freely. The members d @Z7 therefore adp vance and retract with the screws, carrying with them the whole system of braces el, wherefore the screws are braced whatever their position may be. The screws d, which fit into the screws d', as before explained, are

held against turning by a connecting-rod dm, rigidly secured to their lower ends. The screws Z2 are hollow, and they are threaded on their insides to receive the screw d, the ends of which are fitted to rest against the ground or other xed base of support. The system of screws comprising the separate braces, with the exception of the screws al, are turned by smooth square shafts d10, rigidly attached to the tops of the screws d and inside their respective casings d, and each of which shafts pass through a bushing du in the bevel-gear d, by whichthe shaft is turned with a sliding it. The bushing aforesaid is formed to project from the respective gears 0312, and the outside of the part projecting from the gear is turned around and bears on the sides of a circular hole Z13 in the top of its corresponding case d, which thus forms a journal for it. Each bevel-gear K12 intermeshes with a complemental gear el, which gears al are turned by shafts d, rotated by the engine of the crane or any suitable way. The simultaneous action of the adjustable set of screws comprising each of the separate braces will be as follows: Assuming the hoisting-line of the crane is about to be attached to the object to be lifted, the screws will then be substantially in the position shown in Fig. l. The screws CZ' will be turned up to within their respective cases, and the shafts by which they are turned will be extended up through the square hole in the bushing, through which they slide, as before explained. The screwsl d2 will be wholly orv partially contained within the screws d. The

screws ci will accordingly be removed from thel ground or other base of support. The operator then, through the intermediary of the shafts el, the bevel-gears al d, and the shafts d10, will turn the screws el to advance forward. At the same time the screws d2, whose exterior threads are laid in the opposite direction to those of the screw d" and which are prevented `from turning by the bar all, will advance with reference to the screw CZ', thus having the combined advance of the threads of both screws d cl2 and lowering the lower ends of the braces rapidly. When fully extended, the space, if any exists, between` the lower end of each brace and the ground or blocking will be taken up by the hand. With such means of support for the back end of the overhang the danger of the crane becoming strained by the overbalancing-weight in case the load becomes accidentally detached by the breaking of a line or otherwise is entirely eliminated. When the load is lifted and it is seen the fastenings will bear the weight of the load, if it is then wished to move the crane, with its load, or swing it on its center, the reverse motion 1s imparted to the screws and they will be run up. This feature of my invention has been treated from the standpoint that two braces are used to furnish the back support for the overhang. Two braces are better, because they furnish a more stable support; but of course one might be used without departing in any way from the spirit of my invention.

Reference has already been made to the fact that in so far as the essence of my invention is concerned various means may be employed to be acted upon by the movable end of the screws el, which are to be turned by boom, whereby its power and motion may be transmitted to move the counterbalancingweight to its correct position or where it will as nearly as possible offset the weight of the load. In modification, therefore, of the hydraulic means of transmission before referred to I have shown in Figs. 6 and 7 a system of gearing,

adapted to be acted upon by the movable boom end and act as the means of transmission. The mechanical combination of its elements and mode of operation is as follows: .e represents one or more racks secured to the equalizer-bar b and extending backward therefrom in line with the motion of the boom-foot, and which racks through the medium of the equalizer-bar are adapted to have the same relative degree of motion as the foot of the boom, the equalizerbar being secured thereto, as before explained. The racks have any suitable roller-support e and are made to engage with pinions e2, the motion of which, through suitable gears e3 64, is conveyed to the driving-drum e5 upon the same shaft with the gear ef, around which a rope or chain e is wound. One end of the line 6 is attached to the forward end of the vcounterbalancing-weight, while the other end is passed down around the pulley e7, fixed be- `low the drum, thenceis extended back and around the pulley es, and is then extended and secured to the rear end of the counterbalancing-weight. It is obvious that by properly graduating the relative size of lthe gears the counterbalancing-weight will be moved out upon its trackway a distance corresponding III lmay be.

with the distance the boom-foot is moved, or rather a distance relatively vcommensurate with the weight of the load, so having the effect of counterbalancing it. Upon the release of the load the counterbalancing-weight would gravitate back along its inclined track and by reason of the method of line connection would draw the parts back into place or to their normal posture in readiness to be influenced by the next load, whatever its size or weight It is to be noted that the track upon which the counterbalancing-weight is borne is gradually more sharply inclined as it eX- tends from the base. This is for the purpose of compensating,through the increase of presy sure that would be necessary to move the` counterbalancing-weight, for the increase of pressure developed by the weight of the load as the boom-foot is thrust back, the boom then extending gradually at a lesser degree of angle and exerting gradually a more direct pressure than when in its normal position before being moved. It is obvious that the mechanical expedient could be resorted to of securing the rack or racks to the boom end and directly actuating the pinions and other means of transmission; but I would prefer to actuate the members through the medium of the equalizer-bar, that can be guided in its movement, as before explained. This latter means just referred to for receiving the power and motion of the boom-foot is but illustrative of various changes that may be made in vmy invention without departing from its essential character, and while I have described mechanism which I consider at this time to be best adapted for the purposes of the invention I do not wish to be understood as limiting myself to the specific constructions that I have shown and described.

Having thus fully described my invention, I claim and desire to secure by Letters Patent of the United States- ,Y

l. A crane having a boom for supporting the load carried thereby, the foot of which boom is adapted to have movement when draft is imparted to the boom by the weight of the load, a counterbalancing-weight and means whereby the weight of the load through the instrumentality of said boom-foot, thus movable, may move the counterbalancing-weight.

2. A crane havinga boom for supporting the i load carried thereby, which boom is adapted to have a thrust movement when draft is imparted thereto by the weight of the load, a counterbalancing-weight, and means whereby the said load acting through the instrumentality of the boom thus movable may move the counterbalancing-weight to a proper counterbalancing position.

3. A crane having a boom for supporting a load carried thereby, the foot of which boom is adapted to have movement when draft is imparted to the boom by the Weight of the load, a counterbalancing means and means adapted 5. A crane having a boom for supporting the load carried by the crane, the lower .end of which boom is supported to be movable, a support for said movable end of the boom, a movable counterbalancing-weight, means adapted to be acted upon by said movable end of the boom' to move the counterbalancing-weight and hold the same atadistance commensurate with the weight of the load.

6. A crane having a boom the lower end of which boom is supported to have a limited degree of movement, a horizontal support therefor, a movable counterbalancing-weight, and means adapted to be acted upon by the said movable end of the boom for increasing its relative degree of movement and for imparting the force of the same to move the counterbalancing-weight.

7 A crane having a boom the lower end of which boom is supported to have a thrust movement when actuated by the weight of the load, a movable counterbalancing-weight supported to hold a normal position, and means adapted to be acted upon by said boom end to move said counterbalancing-weight, and reversely to be moved thereby to return said boom end and hold the same at a normal position.

8. Acrane having a boom, the lower end of which boom is supported to have movement when `actuated by the weight of the load, a`

movable counterbalancing-weight, an inclined way therefor, and means adapted to be acted upon by said boom end to move said counterbalancing-weight along said inclined way, and hold the same at a distance variable with the weight of the load, and reversely to be acted upon by said counterbalancing-Weight moving along said inclined way to return andhold the boom end in a normal retracted position.

9. A crane having a boom, the lower end of which boom is supported to have a horizontal thrust movement, guides, and a horizontal support therefor to confine said movement to a direction in line with the boom, substantially as and for the purposes set forth.

7 l0. Acrane having a boom, the lower end of which boom is supported to have a thrust movement, means for obtaining such movelment and a support comprising a foot or feet secured to the said lower end of the boom, guides for said foot or feet, rollers carried on the bottom side of the same and a table or support therefor formed within the body of the crane, substantially as and for the purposes setforth.

IOO

IIO

ISO

11. A crane having a boom, the lower end of which boom is supported to have movement when actuated by the weight of the load, a mQvable counterbalancing-weight, an inclined way therefor along which said weight is movable, and hydraulic means adapted to be acted upon by said movable end of the boom to move said counterbalancing-weight along said inclined way, a distance commensurate with the weight of the load.

12. Acrane having a boom, the lower end of which boom is supported to have a limited degree ofmovement, a movable counterbalancing-weight, one or more cylinders the pistons of which are connected to be actuated by the said movable end of the boom, a fluid within said cylinders adapted to be acted upon by said pistons, and means adapted to be acted upon by said fluid to move the counterbalancingweight a distance relatively commensurate with the degree of the movement of the boom end, substantially as and for the purposes set forth. y

13. A crane having a boom, the lower end of which boom is supported to have a thrust movement, a movable counterbalancingweight, and an inclined way or support'therefor, one or more cylinders the pistons of which are connected to be actuated by the said moving end of the boom, a iuid within said cylinders adapted to be acted upon by said pistons and a hydraulic ram comprising a series of telescoping tubes or sections adapted to be acted upon by said fluid, substantially as and for the purposes set forth.

14. A crane having a boom, the lower end of which boom is supported to be movable, a movable counterbalancing-weight and an inclined way or support therefor, one or more cylinders formed within the body of the crane the piston or pistons of which are connected to be actuated by said movable end of the boom, a fiuid contained in said cylinder or cylinders to be compressed by the piston or pistons thereof, and a hydraulic ram comprising a series of telescoping tubes or sections adapted to be acted upon by said iiuidtomove said counterbalancing-weight upward along its inclined Way or support, and reversely to be acted upon by said counterbalancing-weight moving downward along its inclined way whereby the tubes of the said ram are telescoped back, substantially as and for the purposes set forth.

15. A crane having a boom, theV lower end of which boom is supported to be movable, a movable counterbalancing-weight, an inclined way or support therefor, one or more cylinders formed within the body of the crane the piston or pistons of which are connected to be actuated by said movable end of the boom, a fluid contained in said cylinder or cylinders to be compressed by the piston or pistons thereof, a secondary chamber making connection with the primary cylinder or cylinders aforesaid, a hydraulic ram contained therein, the same comprising a series of telescoping tubes or sections adapted to be acted upon by said iiuid to move said counterbalancing-weight upward along its inclined way or support, a series of concave steps for said tubes or sections of the ram and for limiting the extent of movement thereof, substantially as and for the purposes set forth.

16. A crane having a boom, the lower end of which boom is made cleft and supported to be movable, a movable counterbalancingweight and an inclined wayA or support therefor, a plurality of cylinders formed within the body of the crane between the cleft ends of the boom, the piston or pistons of which are connected to be actuated by said movable end of the boom, means for equalizing the motion of said pistons, a uid contained in said cylinders to be compressed by the piston or pistons thereof, passages admitting of the fiow of the said fluid between the said chambers, and a hydraulic ram comprising a series of telescoping tubes or sections adapted to be acted upon by said fluid to move said counterbalancing-weight variable distances along said inclined way dependent upon the weight of the load.

17. A crane having a boom, the lower end of which boom is supported to have a thrust movement when actuated by the weight of the load, a movable counterbalancing-weight, and means adapted to be acted upon by said boom end whereby the said counterbalancingweight may be moved before the load has been lifted from the ground.

18. A crane having a counterbalancingweight for offsetting the weight of the load, an overhanging support therefor extending from the body of the crane, and an adjustable brace or braces secured and extending from said overhanging support to connect with some stable base, substantially as and for the purposes set forth.

19. A rotatable crane having a counterbalancing-weight for offsetting the weight of the load, an overhanging support therefor eX- tending from the body of the crane, and a brace or braces therefor, comprisinga series of adjustable screws, substantially as described.

20. A rotatable crane having counterbalancing-Weight for osetting'the weight of the doad, an overhanging support therefor eX- tending from the'body of the crane, and a brace for the end of said overhanging support, the same comprising the case d, screws d', d2, means for turning the screws d', and means for holding the screws d2, against rotation, substantially as and for the purposes set forth.

21. A rotatable crane having a counterbalancing-weight for offsetting the weight of the load, an overhanging support therefor, extending from the body of the crane, and a brace for the end of said support, the same IOO IIO

comprising a series of screws combined to be vertically extended or retracted, means for obtaining such extension or retraction of the screws, and means for bracing the same during such movement.

22. A crane having a counterbalancingweight for offsetting the Weight of the load, an overhanging support therefor extending from the main body of the crane, a brace for the end of said overhanging support, the same comprising acase d, secured to the end of said support, the screws d', cl2, braces secured to be movable with the screw d, means for securing the screw d2, against rotation, and means for turning the screw d.

23. A crane having a counterbalancingweight for offsetting the weight of the load, an overhanging support therefor extending from the body of the crane, and a brace or 2O braces extending from said overhanging support, each comprising a case secured to the hand-turned screw d, substantially as and for.

the purposes set forth.

ERNEST NICKERSON. In presence of- H. H. LOTTER, V. S. PERsoNs.