US 3423890 A
Description (OCR text may contain errors)
Jan. 28, 1969 B. J. LEIGH BOOM STRUCTURE Filed April 17, 1967 INVENTOR. Bertram J. Leigh BY 1 5 1/ Fig.2
Attorneys United States Patent Ofiice 8 Claims ABSTRACT OF THE DISCLOSURE Boom construction having an outer boom in which an inner boom is telescopingly mounted and in which the outer boom is generally rectangular in cross-section and is formed of a plurality of overlapping metal sections which are provided with outwardly extending reinforcing flanges.
Background of the invention This invention relates to a boom construction for aerial lifts and more particularly to a boom construction for mobile aerial lifts in which a workmans platform is carried by the outer end of the boom structure.
In the boom structures heretofore provided, a great deal of stress is placed on the outer boom by the inner boom as it telescopes in and out of the outer boom and particularly when the inner boom is cantilevered within the outer boom. The stresses are so great that repeated telescoping of the boom structure may cause failure of certain parts of the boom or may cause failure of welds where they are utilized in the boom construction.
Summary of the invention The boom structure is for use with the lift supporting structure and consists of an outer boom which is pivotally mounted on the lift supporting structure for movement about a horizontal axis. An inner boom is provided. Means is also provided which is carried by the inner boom and engages the outer boom which permits relative movement between the inner boom and the outer boom. The outer boom is substantially rectangular in crosssection and is formed of a plurality of sections at least portions of which overlap and in which certain of the sections are provided with outwardly extending reinforcing flanges.
Brief description of the drawings FIGURE 1 is a side elevational view of a mobile lifting equipment utilizing a boom structure incorporating the present invention.
FIGURE 2 is a cross-sectional view taken along the line 2-2 of FIGURE 1.
Description of the preferred embodiment As shown in the drawings, a boom structure 11 is mounted upon a self-propelled van-like vehicle 12 having front and rear wheels 13 and 14 upon which a framework or platform (not shown) is mounted. A cab 16 is mounted on the front of the vehicle and a van-type body 17 is mounted over the rear wheels of the vehicle. The cab 16 is provided with a door 18 to permit entrance to the driving station within the cab.
The boom structure 11 includes an outer or main boom 21 and an inner or telescoping boom 22. A workmans platform or basket 23 is carried by the outer end of the inner boom 22 and is adapted to be moved alongside the driving station of the vehicle 12 as shown particularly in FIGURE 1.
The vehicle 12 and the manner in which the boom structure 11 is mounted upon the vehicle and is operated with respect to the vehicle 12 is described in copending 3,423,890 Patented Jan. 28, 1969 application Ser. No. 521,193, filed Jan. 17, 1966. As described therein, the outer boom 21 is mounted for swinging movement about a horizontal axis formed by a shaft 26 and means is provided which includes a motor 27 for raising and lowering the outer end of the boom structure 11 about the axis formed by the shaft 26. As also described therein, means is provided for rotating the entire boom structure 11 about a vertical axis through 360 and also for extending and retracting the inner boom 22 with respect to the outer boom 21.
As described in said copending application Ser. No. 572,306, filed Aug. 15, 1966 now abandoned, means is carried by the inner boom and engages the outer boom permitting relative movement between the inner boom and the outer boom. Thus, the inner boom is provided with a housing 31 at the rear end thereof which is generally rectangular in shape and serves to support in cantilever fashion the cylindrical inner boom section 32. A pair of vertically extending rollers 33 are rotatably mounted upon the housing 31 and engage the top inner surfaces of the outer boom 21. Bottom vertically extending rollers 34 are mounted on the housing 31 and engage the bottom inner surfaces of the outer boom. Additional side rollers 36 are mounted on the housing 31 and engage the lower inner side surfaces of the outer boom 21.
The outer boom 21 is substantially rectangular in crosssection as can be seen from FIGURE 2 and is formed of a plurality of metal sections, at least portions of which are overlapping. As can be seen in FIGURE 2, the outer boom is formed of upper and lower sections 41 and 42. The upper and lower sections 41 and 42 can be formed of any suitable material such as 11 gauge steel having a minimum yield of 50,000 p.s.i. Both the upper section 41 and lower section 42 are provided with main planar portions 41a and 42a, respectively, which lie in spaced parallel planes and with inwardly turned end portions 41b and 4212, respectively, which extend substantially at right angles to the main portions 41a.
Two additional side sections 43 and 44 are provided which also are formed of any suitable material such as 12 gauge steel having a minimum yield of 50,000 p.s.i. The sections 43 and 44 are both provided with main planar portions 43a and 44a, respectively, which are spaced and parallel to each other and extend at right angles to the main portions 41:: and 42a of the sections 41 and 42. The sections 43 and 44 are formed with inwardly extending end portions 43b and 44b, respectively, which extend at right angles to the main portions 43a and 44a, respectively. In addition, the sections 43 and 44 are provided with portions 43c and 44c which extend at right angles to the portions 43b and 44b and are parallel to the portions 43a and 44a. As can be seen from FIGURE 2, the sections are formed so that the portions 43b and 44b overlie the portions 41b and 42b and serve to enclose the same so that, in effect, the corners formed by the four sections 41, 42, 43 and 44 are reinforced. The sections are joined together in a suitable manner as, for example, by providing welds 46 extending longitudinally of the outer boom and joining the base of the portions 43c and 440 to the main portions 41a and 42a of the sections 41 and 42.
The sections 41, 42 and 43, 44 are formed so that the portions 43c and 440, in effect, form reinforcing flanges or gutters for the outer boom and are positioned in such a manner that they are in general alignment with the inner side edges of the upper rollers 33 and the bottom rollers 34. The portions 421) are of sufficient length so that they are engaged by the side rollers 36. Also, it should be noted that a relatively large radius is utilized for forming the inwardly turned end portions 41b and 42b so that they form gentle curves. Portions 41b and 42b are seated within right angle portions of the side sections 43 and 44 and provide a beam which is triangular in cross-section with an increased moment of inertia that reinforces the corners for the outer boom 21. The triangularly shaped beams are particularly effective in increasing the torsional rigidity of the outer boom.
If desired, as shown in FIGURES 1 and 2, the outer boom 21 can be provided with lightening holes 46 which are spaced longitudinally of the boom.
In use of the boom, it has been found that the construction shown in FIGURE 2 is such that the outer boom will not fail over many tens of thousands of telescoping movements of the inner boom 21 with respect to the outer boom even though the entire forces which are utilized for supporting the inner boom are carried by the housing 31 and the rollers mounted thereon. The reinforcing flanges provided by the portions 43c and 440 greatly stiflen the outer boom 21 and prevent its flexing during telescoping movement of the inner boom. In addition, it has been found that even after severe continued usage, the metal utilized in the boom structure does not fail and, in addition, the welds which are utilized in joining the sections do not fail.
It is apparent from the foregoing that there has been provided a new and improved boom structure which can be economically fabricated and which will readily withstand the forces encountered during normal operation of the boom structure.
1. In a boom structure, an outer boom, an inner boom, and means carried by the inner boom and engaging the outer boom for permitting relative movement between the outer boom and the inner boom, said outer boom being substantially rectangular in cross-section and being formed of a plurality of metal sections having at least portions thereof overlapping and having outwardly extending reinforcing flanges formed thereon and extending longitudinally of the outer boom throughout substantially the entire length of the boom.
2. A boom structure as in claim 1 wherein the outwardly extending reinforcing flanges are formed on upper and lower surfaces of the outer boom and are spaced from opposite sides of the outer boom.
3. A boom structure as in claim 2 wherein the outer boom includes two side sections and wherein the flanges are formed integral with the two side sections.
4. A boom construction as in claim 3 wherein the boom also includes upper and lower sections and wherein the upper and lower sections are provided with inwardly turned end portions which overlap portions of the side sections to provide triangularly shaped beams.
5. A boom structure as in claim 1 wherein said outer boom is formed of a pair of spaced parallel side sections and upper and lower sections, and means joining the upper and lower and side sections together to form an outer boom which is substantially rectangular in crosssection, said flanges being formed integral with the side sections.
6. A boom structure as in claim 1 wherein the means carried by the inner boom and engaging the outer boom consists of a housing, and a plurality of rollers carried by the housing and engaging said outer boom, said upper and lower sections and said side sections having at least portions thereof overlapping in the areas engaged by the rollers.
7. A boom structure as in claim 6 wherein said reinforcing flanges are generally in alignment with at least certain of the rollers carried by the housing.
8. A boom structure as in claim 6 wherein the overlapping portions form corners in which one portion in each corner is bent in a relatively sharp right angle and the other portion in each corner is formed into a gentle curve to provide a triangularly shaped beam.
References Cited UNlTED STATES PATENTS 7/1959 Eitel 2l255 X 7/1964 Pilch 214138 HUGO O. SCHULZ, Primary Examiner.