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 a quick-connect system for 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 220 foot boom may be made of a 40 foot boom butt pivotally mounted to the crane upper works, a 30 foot boom top equipped with sheaves and rigging for lifting and supporting loads, with five sectional boom-members in between: one 10 feet in length, one 20 feet in length and three 40 feet 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 40 foot long sectional boom member may weigh over 5,000 lbs. 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 (10 or 15 lbs.) 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 220 foot 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. CH-585613 describes a connection system for the rods making up a chimney sweeping device. Two rods are connected by means of a peg engaging in a corresponding hole and the two parts are prevented from disengaging by a moveable sleeve which surrounds the connected end portions of the two rods. The present invention 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, a first chord of a first sectional boom member having a first connector secured on one end thereof and a chord of a second sectional boom member abutting said first chord having a connector secured on one end thereof, characterised in that the first connector comprises a vertical pin and the second connector comprises a horizontally extending element having an elongate hole therethrough configured to allow said first and second connectors to be interconnected through rotational engagement about a horizontal axis perpendicular to the length of the boom. In a preferred aspect of the invention, the first and second connectors each comprise a load bearing surface for transmitting compressive loads between abutting chords, the bearing surfaces each being 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. Using the quick-connect features of the invention, a sectional boom can be quickly assembled that has superior load bearing attributes. The invention also allows 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 preferably 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. Another benefit of the preferred embodiment 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. 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 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 elevational view of an 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 of 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 of 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 back hitch 14 and mast or gantry 15, as well as 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 or 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 one embodiment of easily alignable connectors. The easily alignable connectors are 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 on 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. One 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 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 108a 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 intersectioned 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. Figures 6 and 7 show 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 the 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 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 connectors 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 0.4mm 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 connectors, 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 embodiments use 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. The invention may be embodied in other forms without departing from its spirit or essential characteristics. 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.

Claims: A quick-connect system for sectional boom members (22,23,24) for cranes and the like wherein the sectional boom members (22,23,24) 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, a first chord (31) of a first sectional boom member having a first connector (37) secured on one end thereof and a first chord (31) of a second sectional boom member abutting said first chord of the first sectional boon member having a second connector (36) secured on one end thereof, characterised in that the first connector (37) comprises a vertical pin (103) and the second connector (36) comprises a horizontally extending element (101) having an elongated hole (102) therethrough configured to allow said first and second connectors (37,36) to be interconnected through rotational engagement about a horizontal axis perpendicular to the length of the boom. A quick-connect system as claimed in claim 1 wherein the first and second connectors (37,36) each comprise a load bearing surface (108a,108b) for transmitting compressive loads between abutting chords, the bearing surfaces (108a,108b) each being positioned so as to be intersected by the intersection of the horizontal and vertical neutral axes (40,41) of the chord member to which it is attached. A quick-connect system as claimed in claim 2 wherein the bearing surfaces (108a,108b) are symmetrical about both the horizontal and vertical neutral axes (40,41) of the chords to which the connectors (36,37) are attached. A quick-connect system as claimed in claim 2 or claim 3 wherein the load bearing surface (108a,108b) on each connector (36,37) is flat. A quick-connect system as claimed in any preceding claim wherein the elongated hole (102) has a narrow dimension slightly greater than the diameter of the pin (103) such that transverse loads created on the boom are transmitted between the pin and the side wall of the hole. A quick-connect system as claimed in any preceding claim wherein the boom sections each comprise two top chords (31) and two bottom chords (33), and wherein the connectors (36,37) between the top chords are configured to allow rotary engagement of adjacent boom members and the connectors (38,39) between the bottom chords comprise stop-surfaces (118) to limit the degree of rotation of said rotary engagement, the stop-surfaces (118) also comprising compressive load bearing surfaces for the connectors (38,39). A quick-connect system as claimed in any preceding claim wherein first and second sectional boom members are connected by a shear pin connection (113) between chords other than the chords (31) to which said first and second connectors (36,37) are secured, and wherein the shear plane of said vertical pin (103) is perpendicular to the shear plane of said shear pin connector (113).

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 CO, THE MANITOWOC COMPANY, INC.
Application year: 1992
Main classification: B66C23
IPC codes: F16C11, B66C23