Having described my invention, I claim
1. A telescopic boom for a tower crane or the like, comprising at least two telescopic boom sections and a carriage having wheels that roll on said sections, said sections having track surfaces disposed in a common horizontal plane, said track surfaces of one boom section being disposed in close lateral proximity to the track surfaces of another of said boom sections but laterally offset therefrom, and means for shifting said carriage wheels laterally upon passage from one said boom section to another said boom section so that said wheels pass substantially uninterruptedly along a said track surface from boom section to boom section.
2. A boom as claimed in claim 1, said boom sections comprising inner and outer sections, said track surfaces of said inner boom section being more closely spaced than said track surfaces of said outer boom section, said carriage having wheels at each side thereof that ride on said track surfaces, and means for moving said carriage wheels toward each other upon passage of said carriage from said outer to said inner boom section.
3. A boom as claimed in claim 1, said boom sections being of triangular cross-sectional configuration and having an elongated horizontal member at each apex of the triangle, the base of the triangle being horizontal and the lower apices of the triangle being defined by members bearing said track surfaces.
4. A boom as claimed in claim 3, said members being angle irons having horizontal flanges defining said track surfaces.
5. A boom as claimed in claim 3, the apex of the triangle being defined by a ridge member, said boom sections comprising outer and inner sections, said outer section having a said ridge member in the form of a channel member having downwardly extending flanges and said inner boom section having a ridge member in the form of a closed section disposed between said flanges.
6. A boom as claimed in claim 1, said means for shifting said wheels laterally comprising parallelogram linkage, the base of the parallelogram being horizontal.
7. A boom as claimed in claim 6, and means responsive to the passage of the carriage from one said boom section to another said boom section for shifting said parallelogram linkage between a position in which said wheels ride on one said boom section to a position in which said wheels ride on the other said boom section.
8. A boom as claimed in claim 7, said shifting means comprising abutment means carried by one of said boom sections and means carried by said carriage and contacting said abutment means when said carriage is about to pass from one said boom section to the other said boom section to shift said parallelogram linkage.
9. A boom as claimed in claim 8, said means carried by said carriage comprising a movable cam.
10. A boom as claimed in claim 9, said cam having a recess therein and said abutment means comprising a finger that fits in said recess, and means mounting said cam for horizontal swinging movement on said carriage about a vertical axis upon engagement of said finger in said recess.
The present invention relates to booms of great length, more particularly of the type used in tower cranes. Such long booms present problems during transportation and emplacement, because of their great length. It has been proposed to make such booms telescopic, but this solution is complicated by the boom, to move from one telescoping section to the other. The arrangements for transferring the carriage wheels from one telescopic section to the other, which have been proposed in the past, have added considerably to the weight of the boom.
It is accordingly an object of the present invention to provide a telescopic boom, particularly of the type found in tower cranes, in which the carriage can move easily from one telescopic section to the other, without resort to means which add substantially to the weight of the boom or carriage.
Another object of the present invention is the provision of such booms, which will be relatively simple and inexpensive to manufacture, easy to assemble, emplace, operate, maintain and repair, and rugged and durable in use.
Briefly, the objects of the present invention are achieved by providing a telescopic boom according to the present invention, with a wheeled carriage riding thereon, comprising at least two telescoping boom sections, in which the horizontal boom surfaces on which the wheels of the carriage ride are disposed at substantially the same level for all the telescoping sections and are laterally displaced from each other. Means are also provided for moving the carriage wheels toward and away from each other when passing from one telescoping section to the other. Means are also provided for automatically effecting the shift of the wheels, from wide gauge to narrow gauge and vice versa, at about the time of passage of the carriage between boom sections.
Other objects, features and advantages of the present invention will become apparent from a consideration of the following description, taken in connection with the accompanying drawing, in which:
FIG. 1 is a somewhat simplified cross-sectional view of a telescoping boom according to the present invention;
FIG. 2 is an enlarged fragment of the lower left portion of FIG. 1, showing a carriage riding on the boom and a means for shifting the carriage wheels from wide gauge to narrow gauge and vice versa; and
FIG. 3 is a fragmentary plan view of a portion of FIG. 2, showing the cam mechanism for shifting the carriage wheels.
Referring now to the drawing in greater detail, and first to the arrangement of FIG. 1, there is shown a telescoping boom for tower cranes and the like, comprising an outer boom section indicated generally at 1 and an inner boom section telescoped therewithin, indicated generally at 2. Boom sections 1 and 2 are horizontally supported for telescoping movement relative to each other by conventional antifriction means (not shown) and are conventionally supported relative to the tower crane itself by conventional means (not shown).
It will be noted that those boom sections 1 and 2 are generally triangular and have the base of the triangle lowermost and the base and sides of the triangle of one boom closely adjacent those of the other boom. At the lower corners of the triangle formed by the outer boom section 1, are two channel members 3 which are C-shaped in cross section with their webs vertical and disposed toward each other and their flanges horizontally disposed and extending outwardly away from each other. Thus, the upper flanges 4 of the channels 3 present horizontally elongated track surfaces which are exposed laterally outwardly throughout their length and are exposed laterally inwardly at least adjacent their ends.
The apex of the triangle of the outer boom section 1 is provided by a ridge member 5 in the form of a downwardly opening channel member. The members 3 and 5 at the corners of the triangular boom are interconnected by struts 6 spaced along the length of the boom but also spaced from the outer ends of the outer boom section 1 so that those outer end sections extend beyond any strut 6 for a purpose that will be explained later.
The inner boom section 2 has its lower corners defined by channel members 7 in the form of angle irons, which are L-shaped in the illustrated embodiment, and extend lengthwise of the boom. The horizontal flanges 8 of the members 7 extend outwardly away from each other and are disposed at the same horizontal level as the flanges 4 of the members 3 of the outer boom section 1 and are laterally outwardly unimpeded all along their length. The lateral gap between the upper surfaces of the flanges 4 and 8 is maintained as narrow as possible, within convenient construction limits. The apex of the triangular cross section of the inner boom section 2 is defined by a box beam 9 of rectangular cross-sectional configuration, specifically square in the embodiment illustrated, which is disposed between the downwardly extending flanges of the channel members 5 of outer boom section 1. The members 7 and 9 are interconnected by struts 10 spaced along their length.
It will of course be understood that the members 3, 5, 7 and 9 are of great length and have substantially the same cross-sectional configuration along at least most of their length; while the struts 6 and 10 are spaced apart along the length of the boom sections.
Turning now to FIG. 2, there is shown on a somewhat larger scale a fragment of FIG. 1 and also the carriage 12 that rides along the boom. Carriage 12 is supported on the boom for rolling movement therealong by means of wheels 11 mounted for rotation in supports 13 that are connected to the carriage 12 proper by parallelogram linkage 14 and so that wheels 11 can shift between their full line position and their phantom line position shown at 11a, while the axes of the wheels 11 remain at all times horizontal.
Apart from the means for thus shifting the wheels 11 horizontally, carriage 12 can be conventional in construction and so need not be further illustrated or described.
It will of course be understood that the boom of the present invention is bisymmetric about the vertical medial plane X shown in FIGS. 1 and 2. Therefore, the mounting and moving means for the wheels 11, of which only one is shown in FIG. 2, are of course duplicated in mirror image on the other side of carriage 12.
It will also be understood from FIG. 2, that, in the full line position of wheels 11, they ride on the flanges 4 of outer boom section 1; while in the inner or phantom line position 11a, the wheels ride on the flanges 8 of the inner boom section 2. Thus, the pivotal axes of the lower ends of the links of parallelogram linkage 14 are disposed in a common horizontal plane, so that the wheels 11 will be at the same elevation both in their inner and in their outer positions and the axes of the wheels will be horizontal at all times.
To move the wheels 11 between their inner and outer positions, a lever 15 is pivotally attached at one end to one of the links 14 and at the other end is attached for pivotal movement about a vertical axis to a cam 16 of lyre shape, which is pivotally mounted on carriage 12, for horizontal swinging movement about a vertical axis 17. Outer boom section 1 carries a downwardly depending pin 18 adjacent its outer end, which pin is receivable in a recess 19 in cam 16 when carriage 12 approaches the outer end of outer boom section 1. A coil-tension spring 20 is secured at one end to carriage 12 and at the other end to cam 16 and passes over center, relative to axis 17 between the full and phantom line positions of cam 16 which are shown in FIG. 3. Thus spring 20 tends to maintain cam 16 in either one of those positions, the finger 18 swinging the cam 16 between the two positions depending on the direction of movement of carriage 12.
In operation, let it be assumed that carriage 12 is rolling on the outer boom section 1, with its wheels 11 in the full line position shown in FIG. 2, toward the outer end of section 1. When the outer end is reached or closely approached, pin 18 on the outer end of boom section 1 engages in recess 19 of cam 16, which is then in the full line position shown in FIG. 3. Continued movement of the carriage 12 toward or past the outer end of boom section 1, causes the pin 18 to swing cam 16 from the full to the phantom line position shown in FIG. 3, which pulls lever 15 clockwise as seen in FIG. 2 and thus shifts the wheels 11 on opposite sides of carriage 12, toward each other, from the full to the phantom line position 11a shown in FIG. 2. The wheels 11 thus automatically are caused to effect the transition from flanges 4 to flanges 8.
To ease this transition, the outer ends of flanges 4 can be cut away gradually as they approach the vertical web of channel 3, that is, the flanges 4 can be faired, so that there is no sharp transition between the flanges 4 and 8 and there is no loss of support of any wheel 11 during this transition.
It will thus be understood why there is no strut 6 adjacent the outer end of outer boom section 1: such a strut would interfere with the transition of the wheels 11 and so the outer ends of the flanges 4 extend a substantial distance beyond the endmost strut 6.
On movement of the carriage 12 in the reverse direction, the very reverse occurs: the same or a similar pin 18 carried by the outer boom section engages in the recess 19 of cam 16, which is now in the phantom line position shown in FIG. 3, thereby swinging cam 16 back to the full line position shown in FIG. 3. Alternatively, of course, the engagement of the faired edges of the flanges 4 on the vertical flanges of wheels 11 can be relied upon to shift the wheels 11 from their narrow gauge to their wide gauge position.
From a consideration of the foregoing disclosure, therefore, it will be evident that all of the initially recited objects of the present invention have been achieved.
Although the present invention has been described and illustrated in connection with preferred embodiments, it is of course to be understood that modifications and variations may be resorted to without departing from the spirit of the invention, as those skilled in this art will readily understand. Thus, for example, the members 3 and 7 can have various shapes other than those shown. Member 3, for example, might have no lower flange, or could be T-shaped in cross section. Section 7, of course, could be T-shaped in cross section, or could be C-shaped and have an upper flange. These and many other variations and modifications are considered to be within the purview and scope of the present invention as defined by the appended claims.