Quick-connect sectional boom members for cranes and the like

Abstract: A quick-connect system is disclosed for sectional boom members (23,24) for cranes and the like. The sectional boom members (23,24) comprise chords (31,33) for carrying compressive loads, each chord terminating in an end configured to abut against an end of a chord of an adjacent sectional boom member. The quick-connect system comprises at least one easily alignable connector (36,37,38,39) secured to the ends of at least one of the chords, the connector comprising a compressive load bearing surface (58) intersected by the intersection of the vertical and horizontal neutral axes (40,41) of the chord to which the connector is attached.

Description: The present invention relates to quick-connect sectional boom members for cranes and the like. Large capacity lift cranes typically have elongate load supporting boom structures comprised of sectional boom members secured in end-to-end abutting relationship. Predominantly, each of the sectional boom members is made of a plurality of generally axially extending chords interconnected by diagonally disposed lacing or lattice elements. The terminal end portions of each chord are generally provided with connectors of one form or another to secure abutting boom segments together and to carry compressive loads between abutting chords. Typical connectors comprise male and female lugs secured by a pin carrying compressive loads in double shear. An example 67m (220ft) boom may be made of a 12m (40ft) boom butt pivotally mounted to the crane upper works, a 9m (30ft) boom top equipped with sheaves and rigging for lifting and supporting loads, with five sectional boom members in between: one 3m (10ft) in length, one 6m (20ft) in length and three 12m (40ft) in length. Such an example boom has six boom section connections. Typically each section has four chords, and hence four connectors, making a total of 24 connectors that must be aligned and pinned to assemble the boom. Large capacity cranes require very large boom cross sections. As a result, even when the boom segments are laying flat on the ground, the pin connectors between the top chords are typically eight feet or higher off the ground. The rigging personnel must either move a step ladder to each pin location or stand and walk along the top of the boom to reach the top connectors. A 12m (40t) long sectional boom member may weigh over 2268kg (5,000lbs). Thus, an assist crane is required to lift the boom member. One rigger usually then holds the suspended boom section in general alignment while a second rigger uses a large hammer [4.5kg-6.8kg (10 or 15lbs)] to manually drive the pin, which typically has a long taper, into position. In the prior art, the pins connecting the boom sections are generally used to carry the compressive loads between chords. As a result, the pins have a tight fit, further increasing the difficulty in assembling the boom. As such, it may take three men (a crane operator and two riggers) four or more hours to assemble the example 67m (220ft) boom Where the crane is moved frequently, the costs to assemble and disassemble the boom may exceed the cost to lift and position the load for which the crane is used. Efforts have been made to design sectional boom members with quick-connect systems. For example, U.S. Patent No. 3,511,388 discloses a pin connection system for boom structures having tubular chord members. Tapered male lug members are disclosed for insertion, presumably with some rapidity, into female sockets. The lugs are then held together by a pin. Compressive loads are carried by machined surfaces on the perimeter of the lugs, slightly larger in width than thickness of the walls of the tubular members. German Patent Publication No. DE 3842726 A1 apparently discloses a quick-connect system where the connectors on the top chords have hook-like male lugs and female lugs with spaced members capturing a horizontal pin between them. FIG. 10 apparently shows how the hook-shaped member can be fit in place while the boom sections are not parallel, with a rotary motion (about the axis of the pins) bringing the boom sections into parallel alignment and apparently mating up bearing surfaces on the end of each male lug with the inner face of each female lug. Apparently the horizontal neutral axis of the top chords (which appear to be tubular in cross-section) intersect the centerline of the pin, but does not intersect the compressive load bearing surface. It would be preferable if compressive load bearing surfaces on connectors were intersected by the line formed by the intersection of the horizontal and vertical neutral axes of the chords to which they were attached, and most preferably be symmetrical about these axes. This would allow compressive loads to be transmitted through the connectors without creating bending moments in the chords. Also, chords having a right angle cross-section are frequently used on boom sections, and quick-connect systems for such chords would be useful. Quick-connect sectional boom members and quick-connect systems for sectional boom members for cranes and the like have been developed which provide these desired features, as well as many others. The present invention provides a quick-connect sectional boom member for cranes and the like, the sectional boom member comprising: a) a first connector; and b) a bearing surface for carrying compressive loads between sectional boom members; characterised in that the first connector comprises a lug having a vertically protruding pin. The present invention also provides a quick-connect system for sectional boom members for cranes and the like wherein the sectional boom members comprise at least three chords with intermediate lacing elements, each chord terminating in an end configured to abut against an end of a chord of the adjacent sectional boom member, the quick-connect system comprising: a first lug secured to one end of a first chord of a first sectional boom member, the first lug comprising a bearing surface for carrying compressive loads between said first chord and an abutting chord of a second sectional boom member; and a second lug secured to the end of said abutting chord abutting said first end, said second lug comprising a bearing surface for carrying compressive loads between said first chord and said abutting chord; characterised in that the first lug further comprises a vertically extending pin and the second lug further comprises means for engaging with the pin of said first lug, said engaging means allowing initial contact between the lugs when the chords are not parallel and rotating engagement about the pin ending in abutment of the bearing surfaces when the chords are parallel; and in that the bearing surfaces are centered about the intersection of the vertical and horizontal neutral axes of the chords to which the lug on which they are formed is secured. The benefit of the invention is that compressive loads are carried through the connector on bearing surfaces which are intersected by the horizontal and vertical neutral axes of the chords. In this manner the chord's compressive loads do not induce bending moments. Using the quick-connect features of the invention, a sectional boom can be quickly assembled that has superior load bearing attributes. Further, the embodiments of the invention disclosed hereafter each allow rotational engagement of boom sections. That is, the top chords are easily connected by bringing a second sectional boom member into a non-parallel relationship to a first sectional boom member and hooking the top chord connectors of the second boom section into the connectors of the first boom section. As the unattached end of the second boom section is lowered to align the sectional boom members, the bottom chord connectors naturally swing into the proper alignment position. The bearing surfaces on the bottom chord connectors also provide stop-surfaces to prevent further rotation of the second boom section, leaving the connectors aligned so that they can be easily pinned. Less time and manpower are thus required to assemble the boom. These and other advantages of the invention, as well as the invention itself, will best be understood in view of the drawings, a brief description of which is as follows. Figure 1 is a side view of a typical crane with a lattice sectional boom construction to which the present invention may be applied. Figure 2 is a side elevational view of a first embodiment of a quick-connect system of the present invention showing two boom sections during rotational engagement of the sections. Figure 2A is a cross sectional view of one of the top chords of the boom section taken along line 2A-2A of Figure 2. Figure 3 is an enlarged, side elevation view of one embodiment of a top chord connector of the present invention. Figure 4 is a top plan view taken along line 17-17 of Figure 3. Figure 5 is a view of the embodiment of Figure 3 shown in a partially engaged position. Figure 6 is an enlarged, side elevational view of a first embodiment of a bottom chord connection which may be used with the present invention. Figure 7 is a top sectional view taken along line 20-20 of Figure 6. Figure 8 is a top sectional view, similar to Figure 7, of a second embodiment of a bottom chord connection which may be used with the present invention. For ease of reference, designation of "top", "bottom", "horizontal" and "vertical" are used herein and in the claims to refer to portions of a sectional boom in a position in which it would typically be assembled on or near the surface of the ground. These designations still apply although the boom may be raised to different angles, including a vertical position. The typical crane 10, as shown in Figure 1, is comprised of upper works 12 rotatably mounted on lower works 11 which, as shown, may include self propelled crawler tracks. The upper works 12 typically has a counterweight 13 attached thereto and supports a pivotally mounted boom 20. A sheave assembly 17 at the top of the boom 20 is used to hoist loads from the boom. Live rigging or a pendant 16 connects the top of the boom 20 to the gantry 15 and is used to adjust the boom angle. In conventional cranes, the boom 20 is made of several sectional members, including a boom butt 21, boom insert sections 22, 23 and 24, which may vary in number and be of different lengths, and a boom top 25. The sectional boom members 21-25 typically are comprised of multiple chords. In the embodiment shown in Figure 2, each boom section 23 and 24 has a rectangular cross section with a chord at each corner. Thus there are two top chords 31 and two bottom chords 33 (only one of each of which can be seen in the side view) interconnected by lacing on lattice elements 35. In the embodiments shown, the chord members are made of steel with a right angle cross section, as shown in Figure 2A. Each chord member has a vertical neutral axis 40 and a horizontal neutral axis 41. Compressive loads applied at the intersection of the vertical and horizontal neutral axes of a chord will not induce bending moments within the chord. In the preferred embodiments, the lattice elements 35 are welded to the chords such that the centerline of the lattice element 35 is as near as possible to the neutral axis intersecting the face of the chord to which the lattice element 35 is welded. Described hereafter is an embodiment of an easily alignable connector. The easily alignable connector is described as being provided on the top chords 31 of a boom section. Also, two embodiments of connectors for bottom chords 33 are disclosed. Each embodiment includes mating connectors, attached to abutting ends of the chord of the sectional boom members. The mating connectors generally have a male and female relationship. Thus there are two top chord female connectors 36 and two bottom chord female connectors 38 on each boom section, generally but not necessarily on the same end of the boom section, as well as two top chord male connectors 37 and two bottom chord male connectors 39 an opposite ends of the boom section from the respective top and bottom chord female connectors. Thus when two boom sections such as sections 23 and 24 are brought together for assembly, the two top chord female connectors 36 of section 23 mate with the top chord male connectors 37 of section 24, and the bottom chord female connectors 38 of section 23 mate with the bottom chord male connectors 39 of section 24. The foregoing reference numbers are used for the various embodiments disclosed in Figures 3-8. A preferred embodiment of the easily alignable connection of the present invention is shown in Figures 3-5. In this embodiment the quick connect system comprises a male connector 37 having a lug 104 carrying a vertical pin 103. In the preferred embodiment, the pin 103 extends into or through the body of lug 104 and is held in place by a keeper pin 106. Also the pin 103 is preferably tapered at its top end. On the end of chord 31 abutting the chord 31 carrying lug 104 is a female connector 36 comprising lug 101. Lug 101 is a generally horizontally extending element with an elongated hole 102 therethrough. The location and size of pin 103 and hole 102 are such that the lug 101 and 104 may be interconnected through rotational engagement about a horizontal axis perpendicular to the length of the boom, as shown in Figure 5. The horizontally extending portion of lug 104 is fashioned on its end face with a bearing surface 103a for carrying compressive loads between abutting chords 31. Likewise, lug 101 comprises a bearing surface 108b positioned to mate with bearing surface 108a when the sectional boom members are in operational engagement. The bearing surfaces 108a and 108b are each centered about the intersection of, are intersected by and are symmetrical about the vertical and horizontal neutral axes 40 and 41 of chords 31. Preferably the elongated hole 102 has a narrow dimension only slightly greater than the diameter of the pin 103. This allows transverse loads created on the boom 20 to be transmitted between the pin 103 and side wall of the hole 102 as a shear force across the pin 103 at the horizontal interface of the two lugs 103 and 104. Figure 6 and 7 shows a first embodiment of a bottom chord connection for the quick-connect system of the present invention. The female connector 38 comprises two spaced members 111 and 112 extending generally parallel to the chord 33. The male connector 39 comprises one extending lug 114. Each of the spaced members 111 and 112 and the lug 114 include a hole through which a pin 113 can be inserted after the boom sections are aligned. Once in place, the pin 113 may be held by cotter pins 116. As best seen in Figure 7, male lug 114 includes a load bearing surface 118. This bearing surface bears against a load bearing surface formed on tne inside area of connector 38 between the spaced members 111 and 112. As mentioned previously, these load bearing surfaces also provide a stop surface to limit rotation of the sectional boom members about the easily alignable connections between the top chords. Also, these load bearing surfaces are centered about the intersection of, are intersected by and are symmetrical about the vertical and horizontal neutral axes 40 and 41 of the chords 33. A second embodiment of a connector for the bottom chords is shown in Figure 8. This arrangement is similar to the first embodiment except that the bearing surfaces 128 are formed on the ends of the spaced members 121 and 122 making up the female connector 38 and the base of the male connector 39. The lug 124 of the male connector 39 thus does not extend to the inside surface of the female connector 38 between the spaced members 121 and 122. Again, the load bearing surfaces 128 also provide stop surfaces, leaving the holes through the spaced members 121 and 122 and male lug 124 aligned for insertion of pin 123. In this embodiment, the bearing surfaces 128 are not intersected by the vertical neutral axis 40, but are intersected by the horizontal neutral axis 41 (not shown) and are symmetrical about both neutral axes. Also, the centroid of the area of bearing surfaces 128 is intersected by the intersection of axes 40 and 41. Either of the two bottom chord connectors may be used with the top chord connector to provide different quick-connect systems of the present invention. Also, modified bottom connectors may be used where the loads are still carried by the connecting pins, but having stop surfaces similar to surfaces 118 and 128. In these modified embodiments (which may be easier to fabricate since it is easier to maintain tolerances between a pin and a hole than between the required tolerances in positioning load bearing surfaces 118 and 128), the stop surfaces would be set back about 0.38mm (.015") so that when the pins were driven in there would be a slight gap at the stop surfaces. With the use of either of the two bottom chord connector embodiments and the top chord connector, torsional loading on the boom is carried through both bottom chord connections and at least one of the top connectors, depending on which direction the torsional loading is applied. The various pins, lugs and chord members are preferably made of steel, sized in accordance with standard engineering design practice. The lugs may be constructed from welded plate material, or more preferably from castings. The easily alignable connectors shown allows for rotary engagement. During assembly, a suspended boom section is guided into general engagement by one rigger from ground level. The assist crane operator lowers the hoist line, allowing the unengaged end of the suspended boom section to drop, rotating the bottom connector into place. The rigger may then install the ground level bottom pins. Since the compressive loads are carried by the surfaces 118 or 128, the pins 113 or 123 do not require a tight fit. Further, alignment of the holes for the pin is mechanically assured. The described embodiment has several distinct benefits. First, the upper connector is tightly captured longitudinally between the vertical pin and the bearing surface. The final portion of the rotary engagement produces a tight fit with no alignment effort. Second, engagement of both the horizontal and vertical bearing surfaces is readily visible. Third, coupled forces on the chords resulting from moments created from crane swing (especially in tower cranes) will not be able to separate the connectors, since the vertical pin carries the load in single shear. In this embodiment, both top chord connectors act to carry torsional loads. The chord compressive load is carried through the connector bearing surfaces with no induced bending moments since the surfaces are centered about and intersected by the intersection of the vertical and horizontal neutral axes. Even though preferred embodiment uses chords having a right angle cross section, other chord cross sections can be made using the invention by welding endplates on the chords and positioning the connectors such that the proper relationship is achieved between the bearing surfaces and the neutral axes of the chords. It should be appreciated that the apparatus of the present invention is capable of being incorporated in the form of a variety of embodiments, only a few of which have been illustrated and described above. For example, the invention could be applied to triangular cross sectional boom members having only three chords, with either one or two of the chords having easily-alignable connectors. While male and female lug designs are shown, other lug arrangements are possible. For these reasons, the described embodiments are to be considered in all respects only as illustrative and not restrictive, and the scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims: A quick-connect sectional boom member (22-24) for cranes and the like, the sectional boom member comprising: a) a first connector (37); and b) a bearing surface (108a) for carrying compressive loads between sectional boom members; characterised in that the first connector (37) comprises a lug (104) having a vertically protruding pin (103). A quick-connect sectional boom member as claimed in claim 1, further comprising at least three chords (31,33) with intermediate lacing elements (35), each of the chords (31,33) having an end configured to abut a corresponding end of a chord of a second sectional boom member to which said first sectional boom member is adapted to connect; wherein the first connector (37) is attached to the end of at least one of the at least three chords (31,33). A quick-connect sectional boom member as claimed in claim 2, comprising a second connector which also comprises a lug (104) having a vertically protruding pin (103) extending therefrom and a bearing surface (108a), and the bearing surface (108a) on each of said first and second connectors is positioned so as to be intersected by the intersection of the horizontal and vertical neutral axes of the chord member to which it is attached. A quick-connect sectional boom member as claimed in claim 2, wherein the first connector (37) is configured such that an adjoining connector may be attached through rotational engagement of the second sectional boom member. A quick-connect sectional boom member as claimed in claim 2, having a second connector (36) on an opposite end of the chord to which said first connector (37) is attached, comprising a lug (101) with a hole (102) therethrough designed to fit over a vertically protruding pin (103) on a lug (104) of a connector (37) on a second sectional boom member shaped like said first connector (37). A quick-connect sectional boom member as claimed in claim 5, wherein the hole (102) is elongated in a direction parallel to the neutral axis of the chord to which it is attached to facilitate rotary engagement of the connectors (36,37) during connection of said first sectional boom members with said second sectional boom member. A quick-connect sectional boom member as claimed in claim 2, wherein the lug (104) on said first connector (37) comprises a bearing surface (108a) on an end furthest from the chord to which the lug (104) is attached, and said bearing surface (108a) is adapted to mate with a bearing surface (108b) on a lug (101) of a mating connector having a hole (102) therethrough for receiving said pin (103). A quick-connect sectional boom member as claimed in claim 2, wherein the load bearing surface (108a) on the first connector (37) is positioned so as to be intersected by a line extending along the intersection of the horizontal and vertical neutral axes of the chord to which it is attached. A quick-connect system for sectional boom members for cranes and the like wherein the sectional boom members comprise at least three chords (31,33) with intermediate lacing elements (35), each chord terminating in an end configured to abut against an end of a chord of the adjacent sectional boom member, the quick-connect system comprising: a first lug (104) secured to one end of a first chord of a first sectional boom member, the first lug (104) comprising a bearing surface (108a) for carrying compressive loads between said first chord and an abutting chord of a second sectional boom member; and a second lug (101) secured to the end of said abutting chord abutting said first end, said second lug comprising a bearing surface (108b) for carrying compressive loads between said first chord and said abutting chord; characterised in that the first lug further comprises a vertically extending pin (103) and the second lug (101) further comprises means for engaging with the pin (103) of said first lug (104), said engaging means allowing initial contact between the lugs (101,104) when the chords are not parallel and rotating engagement about the pin (103) ending in abutment of the bearing surfaces (108a,b) when the chords are parallel; and in that the bearing surfaces (108a,b) are centered about the intersection of the vertical and horizontal neutral axes of the chords to which the lug (101,104) on which they are formed is secured. A quick-connect system as claimed in claim 9 wherein said engaging means comprises a horizontally extending element on said second lug (101) with an elongate hole (102) therethrough, said elongated hole (102) being configured to allow: a) insertion of the pin (103) through the hole (102) while the first and second chords are non-parallel; and b) rotational engagement by bringing the first and second chords into an end-to-end relationship. A quick-connect system as claimed in claim 9 or claim 10 wherein each of the connections between chords of adjacent boom sections include means to oppose torsional forces applied to the boom. A quick-connect system as claimed in any of claims 9 to 11, wherein the boom sections each comprise two top chords and two bottom chords, and wherein the connectors between the top chords are configured to allow rotary engagement of adjacent boom sections and the connectors between the bottom chords comprise stop-surface to limit the degree of rotation of said rotary engagement.

Inventors: BEEBE WAYNE W, CASAVANT TERRY, LANNING JOHN, PECH DAVID J, PUKITA PAUL M, WANEK MICHAEL J, BEEBE, WAYNE W., CASAVANT, TERRY, LANNING, JOHN, PECH, DAVID J., PUKITA, PAUL M., WANEK, MICHAEL J.
Applicants: MANITOWOC CRANE GROUP INC, MANITOWOC CRANE GROUP, INC.
Application year: 1992
Main classification: B66C23
IPC codes: B66C23