Title:
Gantry
United States Patent 2420163


Abstract:
This invention relates to a gantry and is designed primarily for use in hoisting mechanisms of the boom type such as cranes, excavating machines and the like. Machines of this type comprise a supporting structure, or platform, and are usually self-propelled to enable them to be moved to different...



Inventors:
Borsini, Frederick H.
Application Number:
US58956145A
Publication Date:
05/06/1947
Filing Date:
04/21/1945
Assignee:
MARION POWER SHOVEL CO
Primary Class:
International Classes:
B66C23/36; E02F9/14
View Patent Images:
US Patent References:
2391440Crane boom suspension1945-12-25
2378915Suspension for crane booms1945-06-26
2374074Rotatable derrick1945-04-17
2348285Retractable mast1944-05-09
2198793Tilting boom1940-04-30
2189212Crane1940-02-06
1038809N/A1912-09-17
0538186N/A1895-04-23



Description:

This invention relates to a gantry and is designed primarily for use in hoisting mechanisms of the boom type such as cranes, excavating machines and the like. Machines of this type comprise a supporting structure, or platform, and are usually self-propelled to enable them to be moved to different working positions or to different locations. The boom is pivotally mounted on and extends forwardly from the platform. It is customary to provide means for adjustably supporting the boom so that it may be supported at different angles of inclination as required by the work and may be lowered to a substantially horizontal position to enable the machine to pass under low overhead structures as it is propelled from one location to another, or to be loaded onto a railway car for transportation. When the machine is equipped with a long boom the gantry must be of substantial height in order to properly support the boom in an operative position and it is often too high to pass under overhead structures. It has been proposed heretofore to provide such a machine with a collapsible gantry the upper portion of which can be lowered to reduce its height and which in its collapsend position will support the boom in a lowered position, but such a gantry must be in its extended rigid condition in order to support the boom in an operative position, and it cannot be adjusted to support the boom in different operative positions.

One object of the invention is to provide a machine of the boom type with improved means for adjustably supporting the boom.

A further object of the invention is to provide a boom supporting device which is movable to raise and lower the boom and which will provide adequate support for the boom in all positions of the latter.

A further object of the invention is to provide such a device by means of which the boom may be moved from an approximately vertical position to a substantially horizontal position and which will maintain the boom supporting line at a substantial angle to the boom in all positions of the latter.

A further object of the invention is to provide such a device which will be moved to a lowered position when the boom moves to an approximately horizontal position, A further object of the invention is to provide a gantry having a part which is connected with the boom by a supporting line of fixed length and which is movable about a fixed axis to raise and lower the boom.

A further object of the invention is to providq a boom supporting and adjusting device of such a character that one boom may be removed and another boom substituted therefor without the removal of or change in the supporting and adjusting means other than the provision of a boom supporting line corresponding to the length of the new boom.

Other objects of the invention may appear as the device is described in detail.

In the accompanying drawings Fig. 1 is a side elevation, partly in section, of a machine equipped with the improved gantry; ig. 2 is a perspective view of the platform and suerstructure of such a machine with the boom partly broken away; Fig. 3 is a section taken lengthwise of the shaft of the gantry; and Fig. 4 is a sectional detail view of a portion of the mast and of the bridle mounted thereon.

In these drawings I have illustrated one embodiment of my invention and have shown the same in connection with a portable crane but it is to be understood that the invention may take various forms and may be installed on various machines of the boom type regardless of the char5 acter of the work for which they are designed The crane here shown is of the rotatable type and comprises a supporting structure, or platform, 5 which is mounted on crawling traction devices 6 for movement with relation thereto about a vertical axis. The boom 7 is supported at its lower end, or foot, on the forward portion of the platform for movement about a horizontal axis and has at its outer end, or point, a sheave 8 for the load cable, not shown. The cable drums, power mechanism and the like are mounted on the platform and are usually enclosed in a cab 9.

Ordinarily the boom is supported in adjusted positions about its axis by a rigid upright gantry with which it is connected by a cable or cables extending about sheaves on the boom and the gantry and leading to a hoisting drum by which the cable may be taken in and played out to raise and lower the point of the boom.

In accordance with this invention the gantry comprises a member pivotally supported above the platform for fore and aft movement about a horizontal axis substantially parallel with the axis of the boom, and the upper end portion of this pivoted member is connected with the outer end portion of the boom by a boom supporting line of fixed length, so that the distance between the end portions of the gantry and the boom remains the same in all positions of the boom, and the movement of the boom is controlled by Z5 the movement of the pivoted member. The pivoted member may be of any suitable character and may be supported and actuated in any suitable manner. Preferably the gantry includes a lower part or base 10 on which the pivoted part is mounted. In the present arrangement the base comprises two members I I rigidly secured to the platform in laterally spaced relation and similar in construction to ordinary low A frames, the legs of which converge upwardly and merge into an upper part 12 which, in the present instance, extends through and a short distance above the top of the cab. Pivotally mounted on the base for fore and aft movement about a transverse axis is an upper member or mast 13 the upper end portion of which is connected with the boom. 1i In the illustrated construction the mast comprises two parallel members 14 of substantial length which are rigidly connected and braced one against the other by rods 15 and are pivotally supported on a shaft 16 which is mounted 21 on the upper portions 12 of the two base members. Preferably the members 14 of the mast are provided adjacent their lower ends with bearings 11 through which the shaft extends, the shaft being mounted in apertures in the parts of 2 the base members.

The mast 13 is connected with the boom 7 by a supporting line or lines which may be either rigid or flexible. With a mast of the kind here shown it is preferably to employ two supporting lines : 10, here shown as cables, which are pivotally connected at their rear ends with the respective mast members 14 by links 19 mounted on pivot pins 20 in the forked upper ends of the members 14. At their forward ends the supporting lines are pivotally connected with the boom adjacent the point thereof by links 21. Thus the boom is at all times supported by, and at a fixed distance from, the mast and is moved upwardly by the rearward movement of the mast about its axis and moves downwardly by gravity when the mast is permitted to move forwardly.

Any suitable means may be provided for actuating the mast to raise the boom and for controlling its movement by the weight of the boom, but I prefer to employ a cable or cables for that purpose. In the present arrangement a single cable is used, the cable being attached at one end to a relatively fixed part, extending about sheaves carried respectively by the mast and a part fixed with relation to the platform and spaced rearwardly from the pivotal axis of the mast. There may be any suitable number of sheaves and they may be arranged in any suitable manner. As here shown, a sheave supporting frame, or bridle, 22 is pivotally mounted Ao the upper end portion of the mast, the ends of the frame extending into the forked upper ends of the member 14 and being mounted on the pivot pins 20. Rotatably mounted on the frame and arranged substantially in a common plane are three sheaves 23, 24 and 25. A second sheave supporting frame or bridle 20 is pivotally supported on a fixed axis in the rear of the pivotal axis of the mast and, in the present instance, adjacent thetop of the cab. Two sheaves 27 and 28 are mounted on the bridle 26 substantially in a common plane. Preferably the bridle 26 is mounted in the rear end of a frame connected with the base of the gantry and extending rearwardly therefrom. In the form shown this frame comprises two rigid arms 29 mounted on the shaft 16 and braced one against the other by rods 2?a. Mounted in the rear ends of the arms 2E is a shaft 30 on which the bridle 26 is pivotallĂ˝ supported. The arms 29 are held against upward movement by suitable connections with the platform, such as standards 31 secured at their lower ends to the platform, extending through the top of the cab and having at their upper ends opening through which the shaft 30 extends. The ends of the shaft 30 project outwardly beyond the respective arms 29 and supported on one end of the shaft is a sheave block 32 in which is I mounted a vertical sheave 33. A cable 34 is dead ended on the other end of the shaft 30 and extends upwardly and about the sheave 23 on the mast, thence downwardly and about the sheave 27 and thence successively about the sheaves 24, 28, 25 and 33. From the sheave 33 the cable extends forwardly and downwardly to a cable drum on which it is wound. In the preferred arrangement the drum is mounted on the platform near the rear end thereof, as shown at 35, and the 0 cable extends from the sheave 33 forwardly about a sheave 36 and then downwardly to the drum.

The sheave 36 may be supported in any suitable manner, as by a standard 37 mounted on the platform and, as here shown, it extends partially through the top of the cab with its axis adjacent said top. In some installations it may be desirable to mount a cable drum near the front end of the platform, either in substitution for or in addition to the drum 35. Such a drum is shown i' in broken lines at 38 in Fig. 2 and the cable extends forwardly from the sheave 33, about a sheave 39 supported adjacent the forward end of the top of the cab, and thence downwardly to the drum 38. If both drums are provided the cable may be disconnected from one drum and connected with the other drum as desired. The cable drum or drums may be of the type commonly used on hoisting machinery and which is provided with a brake to hold the drum normally 40 against rotation by the load on the cable and to control the unwinding of the cable from the drum when the load is to be lowered, and which may be operated from any suitable source of power.

45 The arrangement of the mast and its actuating mechanism is such that the boom may be moved to substantially a vertical positipn and to avoid the possibility of its being moved to a position in which it would tend to fall rearward0 ly out of control it is desirable to provide a stop to prevent the movement thereof beyond a safe position, say eighty degrees from horizontal. A stop suitable for this purpose comprises an elongate tubular element 40 pivotally mounted at its 5 lower end on, or adjacent to the axis of, the shaft 16 on which the mast is mounted, and a rod 41 slidably mounted in the tubular element and pivotally connected with the boom at a suitable point between the ends of the latter, as by 60 a lug or bracket 42 rigidly secured to the boom.

The length of the tubular element is such that the upper 'end thereof will engage the lug 42 when the boom has been moved to the desired limit of its movement and thus prevent the fur65 ther rearward movement thereof. The length of the rod is such that it will not be withdrawn from the tubular element when the boom moves to its lowermost position.

The normal range of operation of the boom is 70 between the eighty degree position shown in full lines in Fig. 1 and the twenty-five degree broken line position 7a, but the boom may be lowered S to the substantially horizontal broken line position 7b and in all these positions the boom sup75 porting line 18 extends at an angle to the boom sufficient to provide adequate support for the boom and to lift the same. Further, when the boom is in an approximately horizontal position the mast is in a lowered forwardly extending position and the hoisting cable extends at such an angle to the mast as to support and lift the mast and the boom. Thus both the boom and the mast may be quickly and easily lowered to and supported in positions which will permit the machine to be propelled beneath an overhead structure. The mast is of such length that as it moves forwardly or rearwardly through the vertical plane of its pivotal axis the upper end thereof travels in an arc of substantial length with a relatively small vertical displacement of the upper end of the mast, with which the boom supporting line is connected. As a result of this small vertical movement of the end of the mast the angle between the supporting line and the boom remains substantially constant through a relatively wide range of movement of the boom.

When one boom is to be removed from the machine and another boom substituted therefor, either for the purpose of providing a boom of different length or of replacing a damaged boom, this may be accomplished by lowering the boom onto a fixed support, disconnecting the supporting line from the mast, removing the boom from the platform and then connecting the new boom with the platform and connecting its supporting line with the mast. If the new boom is of a length different from the old boom a supporting line of different length will be required but otherwise the supporting line may be disconnected from the old boom and then connected with the new boom. The telescoping stop device may be disconnected or the rod may be withdrawn from the tubular element when the boom is removed and replaced by a similar rod connected with the new boom. It is not necessary to remove or to in any way disturb the boom hoist cable 34 or any part of the mechanism other than those mentioned, thus enabling the change of booms to be effected in a relatively short time and with a minimum of labor. 4 While I have shown and described one embodiment of my invention I wish it to be understood that I do not desire to be limited to the details thereof as various modifications may occur to a person skilled in the art. Having now fully described my invention, what I claim as new and desire to secure by Letters Patent, Is: In a machine comprising a platform and a cab on said platform, a boom mounted on said platform for movement about an axis transverse to its length, a gantry comprising two base members mounted on said platform in the rear of the pivotal axis of said boom, spaced laterally one from the other and extending above the top of said cab, a shaft mounted on said base members above the top of said cab and spaced rearwardly a substantial distance from said axis of said boom, and a mast including side members mounted on said shaft for fore and aft movement about the axis thereof, a supporting connection of normally fixed length between the upper end of said mast and said boom, a sheave supporting member arranged between and pivotally mounted on the upper portions of the side members of said mast, a plurality of sheaves carried by said supporting member, a rigid frame comprising laterally spaced elongate arms mounted on said shaft and extending rearwardly therefrom, means for rigidly connecting the rear portions of said frame with said platform, a sheave supporting member arranged between and pivotally mounted on the rear portions of said elongate arms of said frame, a plurality of sheaves carried by the last-mentioned supporting member, a cable anchored at one end and extending about the sheaves on said supporting members, and a drum mounted on said platform and operatively connected with the other end of said cable. FREDERICK H. BORSINI.

REFERENCES CITED The following references are of record in the file of this patent: UNITED STATES PATENTS Number 538,186 1,038,809 2,189,212 2,198,793 2,348,285 2,374,074 2,378,915 2,391,440 Name Date Widdows --_-_____ Apr. 23, 1895 Williams ---------- Sept. 17, 1921 Ljungkull --______-------- Feb. 6, 1940 Schroeder -- __--- _ Apr. 30, 1940 Ekboom et al. ---___ May 9, 1944 Derby et al. -------- Apr. 17, 1945 Davidson --_----_ June 26, 1945 Anderson -----___ Dec. 25, 1945