Mobile floor crane

A mobile floor crane has a tubular, rigid stanchion that supports a boom pivotally connected to the top end of the stanchion. The base end of the stanchion is disposed between the adjacently disposed mid portions of the tubular, rigid legs of the crane. A support member extends transversely through the mid portions of the legs and the base end of the stanchion and supports the stanchion. In an alternative embodiment, the legs have telescoping members, and a rolling member is provided on the base end of the stanchion to provide mobility for the crane when the telescoping members are detached for storage.

BACKGROUND OF THE INVENTION
 The present invention relates to floor cranes and more particularly to
 mobile floor cranes used in the automotive aftermarket.
 Conventional mobile floor cranes such as shown in U.S. Pat. Nos. 3,931,956
 and 4,669,703 typically have a pair of legs and a cross piece forming a
 bridge connecting the two legs and supporting the central upright
 stanchion of the crane. The legs and the cross piece typically are formed
 of tubular steel for increased strength. However, the strength of the
 cross piece and the strength of its connection to the two legs limit the
 amount of weight that can be lifted by the crane. The lateral distance
 between the stanchion and the legs provides a bending moment that can
 apply a twisting force to the legs and cause the crane to fail. Attempts
 to stabilize the legs against twisting have included the provision of a
 caster under each leg in the vicinity of the crosspiece as shown in U.S.
 Pat. No. 5,076,448. However, this then shifts the load from being carried
 by the rear wheels to being carried by the wheels beneath the legs by the
 crosspiece, and this shift has the undesirable effect of reducing the
 overall footprint of the load-carrying components of the crane. In the
 end, one type of instability is traded for another type of instability.
 Moreover, construction of these so-called bridge-type cranes wherein the
 cross piece forms a bridge between the two legs, involves multiple
 manufacturing operations like metal cutting, hole-drilling, positioning,
 welding, and bolting. These manufacturing operations, and particularly the
 welding operations, add significantly to the overall cost of the crane.
 For example, the cross piece must be sized and cut, and in some
 embodiments the cross piece must be welded to the base and/or the legs. A
 crane design that could eliminate the cross piece might be produced less
 expensively than a comparable bridge-type crane due to the elimination of
 fabrication materials, fabrication time, and fabrication operations
 involving the cross piece.
 Precise positioning of the parts relative to one another before they are
 welded also plays a significant role in the cost of manufacture of these
 conventional cranes. If the upright stanchion is located off-center
 relative to the two legs, then the load carried by the stanchion will not
 be evenly distributed between both legs of the crane. The off-center
 stanchion may wiggle or tend to tilt in use. Thus, siting of the stanchion
 atop the cross piece must be done with care, or the stanchion will be off
 center and the crane will need to be rejected. Rejects lead to waste that
 increases the cost of production. Moreover, the cumulative tolerances for
 the parts involved in positioning the stanchion can result in errors that
 cause a misalignment that might not be detectable by the eye of the user
 who assembles the crane.
 OBJECTS AND SUMMARY OF THE INVENTION
 It is a principal object of the present invention to provide an improved
 mobile floor crane that has an equivalent or greater lifting capacity as
 conventional cranes yet is configured so as to be less costly to
 manufacture.
 It is another principal object of the present invention to provide a method
 of making a mobile floor crane that reduces the cost of making the crane
 without sacrificing the lifting capacity of the resulting crane.
 It is a further principal object of the present invention to provide a
 mobile floor crane that easily disassembles for shipment and storage yet
 is less expensive to manufacture than a conventional crane without any
 reduction in the lifting capacity of comparable conventional cranes.
 Additional objects and advantages of the invention will be set forth in
 part in the description which follows, and in part will be obvious from
 the description, or may be learned by practice of the invention. The
 objects and advantages of the invention may be realized and attained by
 means of the instrumentalities and combinations particularly pointed out
 in the appended claims.
 A portable lifting device such as a mobile floor crane includes a stanchion
 carried by a mobile base. The base can be rendered mobile by wheels,
 rollers, or casters attached to the base. The wheels, rollers, or casters
 are disposed symmetrically with respect to a stanchion carried by the
 base. The base is formed by a pair of legs that are configured identically
 and disposed so as to be mirror images of each other. The stanchion is a
 rigid, vertically elongated, upright member that is centrally disposed
 relative to the legs. The stanchion is desirably formed of tubular steel
 having a generally rectangular transverse cross section along the entire
 length thereof.
 Each leg is desirably formed of tubular steel having a generally
 rectangular transverse cross section along the entire length thereof. Each
 leg has a rear portion, a mid portion, and a forward portion. In forming
 the base, the legs are disposed alongside one another such that the mid
 portions are side-by-side and opposed to one another such that each leg is
 the mirror image of the other. Along the mid portions of the legs, the
 legs are separated from each other by a distance that is not substantially
 more than the width of the stanchion. Each leg has a means for rendering
 the crane mobile. This typically can include a wheel assembly to support
 the free end of the forward portion of each leg and a caster to support
 the free end of the rear portion of each leg.
 In accordance with a presently preferred embodiment of the invention, the
 base end of the stanchion is disposed between the mid portions of the legs
 and mounted on a support bolt passing transversely through the mid
 portions of both legs and the base end of the stanchion. In the preferred
 case, the separation between the mid portions of the legs only allows
 sufficient clearance for the stanchion to be pivotable about the support
 bolt during assembly. Once assembled, the support bolt desirably places
 the stanchion and the mid portions of the legs under compression, thus
 substantially reducing any bending moments that might twist the legs under
 load.
 In still further accordance with a presently preferred embodiment of the
 invention, the mid portions of both the left and right legs are
 permanently attached to a unitary tubular member that functions as the
 rear portions of both legs and defines the spacing between the mid
 portions of the legs. In an alternative embodiment, a spacer is disposed
 between the mid portions of the legs in the vicinity of the rear portions
 of the legs. The spacer is formed by a rigid block that has substantially
 the same width as the width of the stanchion. The unitary tubular member
 and the spacer desirably can be formed of the same stock of tubular steel
 as the stanchion. In another alternative embodiment, a back brace is
 disposed between and connecting the rear portions of the legs.
 In accordance with a presently preferred embodiment of the invention, an
 obtuse angle is formed between the mid portion and the forward portion of
 each leg. Desirably, this angle is formed by bending the unitary tubular
 member that is used to form each leg.
 In accordance with a presently preferred embodiment of the invention, a
 second angle is formed between the rear portion and the mid portion of
 each leg. In an alternative embodiment, this angle is also formed by
 bending the unitary tubular member that is used to form each leg.
 By eliminating the cross piece and supporting the stanchion on the support
 bolt, the bending moment associated with the cross piece is also
 eliminated. Thus, the crane of the present invention is stronger than
 conventional cranes of the same dimensions and thus has greater lifting
 capacity. Moreover, the lifting device of the present invention is less
 costly to manufacture than conventional cranes. Because of the
 construction of the lifting device of the present invention, it is less
 likely that the stanchion will be installed off center.
 The accompanying drawings, which are incorporated in and constitute a part
 of this specification, illustrate one embodiment of the invention and,
 together with the description, serve to explain the principles of the
 invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Reference now will be made in detail to the presently preferred embodiments
 of the invention, one or more examples of which are illustrated in the
 accompanying drawings. Each example is provided by way of explanation of
 the invention, not limitation of the invention. In fact, it will be
 apparent to those skilled in the art that various modifications and
 variations can be made in the present invention without departing from the
 scope or spirit of the invention. For instance, features illustrated or
 described as part of one embodiment, can be used on another embodiment to
 yield a still further embodiment. Thus, it is intended that the present
 invention cover such modifications and variations as come within the scope
 of the appended claims and their equivalents. The same numerals are
 assigned to the same components throughout the drawings and description.
 One presently preferred embodiment of the mobile lifting device of the
 present invention is shown in FIG. 4A as a crane that is designated
 generally by the numeral 100. Another presently preferred embodiment of
 the mobile lifting device of the present invention is shown in FIG. 8 as a
 crane that is designated generally by the numeral 101. An alternative
 embodiment of the mobile lifting device of the present invention is shown
 in FIG. 1A as a crane that is designated generally by the numeral 10.
 Another alternative embodiment of the mobile lifting device of the present
 invention is shown in FIG. 2A as a crane that is also generally designated
 by the numeral 10.
 As shown in FIGS. 4A and 1A, crane 100, 10, respectively, includes a right
 leg 11 and a left leg 12 that is disposed opposite right leg 11. As shown
 in FIGS. 4B and 1B, each leg is formed of a rigid material such as steel.
 While each leg can be formed of a length of L-bar (having an L-shaped
 transverse cross section) or C-channel steel (having a C-shaped transverse
 cross section), each leg desirably has a tubular configuration that is
 hollow inside, as this configuration provides the desired strength.
 Moreover, the transverse cross-sectional shape of the tubular rigid
 material can be circular or polygonal, such as square, rectangular,
 hexagonal, etc.
 In a rectangular transverse cross-sectional shape shown in FIGS. 4B and 1B
 for example, the tubular configuration of each leg includes a pair of
 opposed side panels 13, 14 and a top panel 15 and a bottom panel 16, all
 of the panels being formed as a unitary tubular structure. The material
 forming each leg desirably is rolled, low carbon steel, and the gauge of
 steel and the width and depth of the rectangular cross-section depends
 upon the desired lifting capacity of the crane. For example, if the crane
 is to have a lifting capacity of two (2) tons, three inch by three inch
 rectangular cross-section eight (8) gauge steel is desired for forming
 each leg. The configuration of the crane for a given lifting capacity
 depends on the length of the legs, the cross-section of the tubing used to
 form the legs, the location of the load, and the length of the boom
 (described below).
 As shown in FIGS. 4B and 1B, each leg has a distinctive overall general
 configuration. Thus, each leg includes a rear portion 17, a forward
 portion 19 and a mid portion 18 that is disposed between rear portion 17
 and forward portion 19. Each of said rear portion 17, mid portion 18 and
 forward portion 19 defines a separate elongated straight section of the
 leg.
 In the presently preferred embodiments shown in FIGS. 4A, 4B, 8 and 9, the
 crane includes an undercarriage that includes the provision of a unitary
 member 61 that forms the rear portions 17 of both legs and provides for
 the permanent joining of both legs 11, 12 in a single integral structure.
 Thus, each leg has a unitary tubular member composed of the forward
 portion 19 and the mid portion 18. Moreover, the mid portions 18 of both
 the left and right legs are permanently attached to the unitary tubular
 member 61 that functions as the rear portions 17 of both legs. As shown in
 FIGS. 8, 9, 4A and 4E for example, the permanent attachment of the mid
 portions 18 of both legs to the unitary back portion member 61 can be
 effected as by welding a seam 62. The material forming unitary tubular
 member 61 desirably is rolled, low carbon steel, and the gauge of steel
 and the width and depth of the rectangular cross-section depends upon the
 desired lifting capacity of the crane. For example, if the crane is to
 have a lifting capacity of two (2) tons, three inch by three inch
 rectangular cross-section eleven (11) gauge steel is desired for forming
 unitary tubular member 61.
 In an alternative embodiment shown in FIGS. 1A and 1B, a spacer member 54
 desirably is formed as an abbreviated length of the same rigid tubular
 member that is used to form legs 11, 12 and can be disposed between left
 leg 12 and right leg 11. Spacer member 54 can be partially fastened
 between left leg 12 and right leg 11 by a fastening bolt 52.
 Another attachment bolt 55 can be provided through the opposite end of the
 spacer member 54 and through the mid portion 18 of each leg at a location
 spaced along the length of the mid portion 18 and between the location
 where the fastening bolt 52 is connected and where the stanchion 25
 (described below) is connected to the leg. The fastening bolts 52, 55 can
 be fastened by threaded nuts and places the bolts 52, 55 under tension and
 the legs 11, 12 and spacer member 54 under compression. Thus, the
 undercarriage of the embodiment of FIGS. 1A and 2A includes both legs 11,
 12 and the spacer member 54 connected together.
 In an alternative embodiment shown in FIGS. 15A and 15B for example, a back
 brace 110 that can be configured from a right angle plate can be fitted
 over the rear face and top face of the rear portions 17 of the legs 11,
 12. Back brace 110 can be configured as a length of L-bar (having an
 L-shaped transverse cross section) as shown in FIG. 15B for example.
 Alternatively, the right angle plate forming back brace 110 can be
 configured as a C-channel steel bar that overlaps three sides of the rear
 portions 17 of the legs 11, 12 and leaves a cut out for accommodating
 where mid portions 18 of the legs meet the rear portions 17. As shown in
 FIG. 15B for example, a plurality of fasteners such as bolts 111, washers
 112 and threaded nuts 113 are provided to firmly attach back brace 110 to
 the rear portions 17 of legs 11, 12. In this alternative embodiment, it is
 possible to dispense with spacer member 54. Additionally, a similar back
 brace 110 can be used with an embodiment such as shown in FIG. 5C for
 example.
 As shown in FIGS. 4B, 9, 1B and 2B for example, the mid portion 18 and
 forward portion 19 are formed as a unitary tubular member. As shown in
 FIGS. 1A, 1B, 2A and 2B, the rear portion 17, mid portion 18 and forward
 portion 19 are formed as a unitary tubular member. As shown in FIGS. 4B,
 9, 1B and 2B for example, a first bend 20 forms the vertex of an obtuse
 angle Alpha (.alpha.) disposed between mid portion 18 and forward portion
 19 of each leg. The first bend 20 desirably can define an angle Alpha
 (.alpha.) that is in the range of 135.degree. to 170.degree., but other
 angles are possible depending upon the desired application for the crane.
 As shown in FIGS. 4B, 9, 1B and 2B for example, a second bend 21 forms the
 vertex of a right angle Beta (.beta.) where the mid portion 18 joins the
 rear portion 17 of each leg. As shown in FIGS. 1B and 2B for example,
 spacer member 54 is located between the ends of the mid portions 18 of the
 legs that is closest to where second bend 21 forms the vertex of a right
 angle Beta (.beta.) where each mid portion 18 joins the rear portion 17 of
 each leg.
 The angle formed by first bend 20 will contribute to determining the
 footprint of the crane as it rests on or is moved across the floor. In
 some cases a wider footprint is desirable depending upon the intended
 purpose of the crane. In most cases, a narrower footprint is more
 desirable so long as the included angle defined between the forward
 portions 19 of the legs is large enough to dispose the legs outside of the
 footprint of the load that the crane is intended to lift. A typical angle
 for first bend 20 would be 167.50 so that the so-called included angle
 between the two legs 11, 12 as they were laid side-by-side would be
 25.degree.. The legs are desirably provided with an included angle such
 that the legs are disposed sufficiently outside of the center of gravity
 of the intended load to be lifted by the boom so as to provide a
 comfortable margin of safety for anticipated sideways movement of the
 load.
 As shown in FIG. 4B for example, the bending that forms first bend 20
 typically causes formation of an elongated indentation 22 in side panel 13
 of the leg. This indentation 22 is formed so that it extends into part of
 mid portion 18 and part of forward portion 19 of each outwardly facing
 side panel 13 of each leg 11 or 12.
 Similarly, as shown in FIG. 1B, a second bend 21 defines the vertex of a
 right angle Beta (.beta.) that forms the vertex connecting the mid portion
 18 and rear portion 17 of each leg. Though not shown in the Figs., an
 indentation similar to indentation 22 shown in FIG. 4B forms where second
 bend 21 defines the vertex of the right angle between rear portions 17 and
 mid portions 18 of each leg 11, 12.
 As shown in FIGS. 4A, 8, 1A and 1B, a rolling member such as a caster 23
 desirably is provided beneath each free end of the rear portion 17 of each
 leg in order to assist in rendering the crane mobile. As shown in FIGS. 1A
 and 1B for example, another rolling member such as a caster 24 can be
 disposed at the free end of the forward portion 19 of each leg 11, 12 to
 support the leg and assist in providing mobility for the crane.
 In the presently preferred embodiments shown in FIGS. 4A and 8 for example,
 neither the left leg nor the right leg is formed as a unitary structure as
 in the embodiment shown in FIGS. 1A and 1B. Moreover, each leg 11, 12
 includes a leg extension member 56 that is removably connected to the free
 end of forward portion 19 by a telescoping connection. One end of leg
 extension member 56 and the forward-most end of forward portion 19 of each
 leg 11, 12 can be configured so that one is insertable into and nests
 within the other. In the embodiment shown in FIG. 4A for example, leg
 extension member 56 is configured so as to be insertable into the
 forward-most end of forward portion 19 of each leg 11, 12, and this is the
 presently preferred configuration. The material forming each leg extension
 member 56 desirably is rolled, low carbon steel, and the gauge of steel
 and the width and depth of the rectangular cross-section depends upon the
 desired lifting capacity of the crane. For example, if the crane is to
 have a lifting capacity of two (2) tons, two and one half inch by two and
 one half inch rectangular cross-section eleven (11) gauge steel is desired
 for forming each leg extension member 56. As shown in FIG. 4A for example,
 leg extension member 56 is connected to forward portion 19 by a threaded
 attachment bolt 57 that is inserted transversely through forward portion
 19 and leg extension member 56. Threaded bolt 57 can be inserted from
 either side panel 13 or 14 of the leg 11, 12. Moreover, the caster 24 at
 the free end of the forward portion 19 of each leg is provided on the free
 end of the leg extension member 56 as shown in FIG. 4A. In an alternative
 embodiment, leg extension member 56 and the forward-most end of forward
 portion 19 of each leg 11, 12 can be configured so that the forward-most
 end of forward portion 19 of each leg 11, 12 is insertable into and nests
 within one end of leg extension member 56.
 One advantage of the embodiments of FIGS. 4A and 8 over the embodiment of
 FIGS. 1A and 1B is the possibility of reducing the length of the shipping
 carton. Each leg 11, 12 can be disassembled into two smaller components in
 the embodiments of FIGS. 4A and 8. Moreover, the provision of a series of
 holes along the length of each forward portion 19 of each leg renders the
 length of each leg adjustable in the embodiments of FIGS. 4A and 8.
 As shown in FIGS. 6A, 6B, 6C and 6D for example, casters 23, 24 can be
 replaced in some embodiments by other means of rendering the crane mobile
 such as wheels 68 mounted on axles 69. For example, as shown in FIG. 9, a
 plate 72 can be welded to a mount 73 for an axle 69 and wheel 68
 arrangement, and plate 72 can be welded against the bottom surface of the
 end of leg extension members 56 or the ends of legs 18, 19. Notice that
 plate 72 and mount 73 are welded so that the plane in which wheel 68
 rotates is disposed at an angle with respect to the length of extension
 member 56 so that this rotational plane of wheel 68 is parallel to the
 plane defined by the boom and stanchion of the crane in order to
 facilitate steering during movement of the crane.
 As shown in FIGS. 6B, 6C and 6D, additional fixed wheel and axle
 configurations can be provided on the end of leg extension members 56 or
 the ends of the legs 18, 19 themselves, depending on the embodiment. As
 shown in FIG. 6B, a wheel 68 mounted on an axle 69 disposed between the
 two side arms of a section of a C-channel member 30 can be attached as by
 a threaded bolt 70 and nut 71 onto the end of extension members 56 or on
 the ends of legs 18, 19. Alternatively, the C-channel wheel and axle
 arrangement can be welded with the base of the C-channel welded against
 the bottom surface of the end of leg extension members 56 or the ends of
 legs 18, 19. As shown in FIG. 6C, a section of a C-channel member 30 can
 be welded on the end of extension members 56 or on the ends of legs 18, 19
 in an orientation that is configured to form a hooded wheel 68 mounted on
 an axle 69 disposed between the two side arms of C-channel member 30. As
 shown in FIG. 6D, the base of a section 30 of a C-channel is permanently
 attached to each of the free ends of the front portions 19 of the legs 11,
 12 (or leg extensions 56). Wheels 68 are mounted on axles 69 mounted
 between the arms of the section 30 of the C-channel. In such an
 embodiment, casters 23 (not shown in the FIG. 6D view) are provided
 beneath the free ends of rear portions 17 so that steering of the crane is
 facilitated. As in the FIG. 9 embodiment, the rotational plane of wheel 68
 is disposed parallel to the plane defined by the boom and stanchion of the
 crane.
 As shown in FIGS. 1A, 4A, 8 and 10 for example, a stanchion 25 is provided
 and desirably is also formed of tubular rigid material that desirably is
 the same as provided for the legs and spacer member 54. The material
 forming the stanchion 25 desirably is rolled, low carbon steel, and the
 gauge of steel and the width and depth of the rectangular cross-section
 depends upon the desired lifting capacity of the crane. For example, if
 the crane is to have a lifting capacity of two (2) tons, three inch by
 four inch rectangular cross-section eleven (11) gauge steel is desired for
 forming stanchion 25. However, the stanchion can be formed of the same
 alternative materials noted above for forming the legs.
 As shown in FIG. 10, the stanchion also can include a pair of opposed side
 panels 26, 27 (only one being visible in FIG. 1A), a front panel 28 and a
 back panel 29 (FIG. 10). All of the panels forming the tubular member that
 composes the stanchion 25 are desirably part of a unitary tubular member
 having a rectangular and preferably a square transverse cross-sectional
 shape. However, the tubular member that composes the stanchion 25 also can
 have different transverse cross-sectional shapes that can be polygonal or
 circular as shown in FIGS. 14A, 14B, and 14C for example.
 As shown in FIGS. 4A, 1A, 1B, 2A and 8 for example, stanchion 25 is
 disposed symmetrically between and above right leg 11 and left leg 12.
 Further, stanchion 25 has a base end 31 shown in FIGS. 11, 1A and 1B for
 example. And as shown in FIGS. 1A and 10 for example, stanchion 25 has a
 top end 32, which is located generally opposite base end 31.
 In accordance with the present invention and as shown in FIG. 4B for
 example, a support member 33 is disposed to extend transversely through
 both of the side panels 13, 14 of each of the right leg 11 and the left
 leg 12 and through both of the side panels 26, 27 of the base end 31 of
 stanchion 25. The diameter of support member 33 can be varied depending
 upon the desired lifting capacity of the crane and the grade of steel. For
 example, for a lifting capacity of 2 tons, support member 33 can be 3/4
 inches in diameter and formed of carbon alloy steel of at least ASTM grade
 5, and desirably ASTM grade 8 carbon alloy steel. However, the larger the
 diameter of support member 33, the lower the grade of steel that can be
 used to form member 33.
 Support member 33 can take many forms, including a form Do that permits the
 legs and stanchion to be placed under tension or not, as desired. However,
 it is preferable for the support member 33 to facilitate the tightening of
 the legs and stanchion to be placed under tension. This can be
 accomplished if the support member 33 takes the form of a bolt with a head
 on one end and threaded on the other end so as to receive a threaded nut
 as shown in FIGS. 8 and 11 for example. In an alternative tensioning
 configuration, support member 33 can be formed as a bolt that can be
 fastened in place on its opposite ends by threaded nuts and in a manner
 similar to that shown in FIG. 4B for example wherein the surfaces of
 inwardly-facing side panels 14 of the legs 11, 12 are contacting the
 opposed surfaces of the respective side panels 27, 26 of the base end 31
 of the stanchion 25. When support member 33 fastens base end 31 of
 stanchion 25 to the mid portions 18 of the legs 11, 12, member 33 is under
 tension, and the base end 31 of stanchion and the mid portions 18 of the
 legs 11, 12 are under compression. The manner of attachment of stanchion
 25 to right leg 11 and left leg 12 in the embodiment of FIG. 4B is the
 same as shown in FIGS. 1A, 1B, 2A, 2B, 3A, 3B, 4A, 4C, 4D, 9, 12A and 13
 for those related embodiments.
 Alternative support members 33 can be provided that do not place the legs
 and stanchion under tension, but prevent them from separating more than a
 predetermined distance from one another. As shown in FIG. 14A, such
 alternative support members 33 can include a shaft with a head 103 on one
 end and a clevis pin or cotter pin 104 on the opposite end. As shown in
 FIG. 14B, a rod or straight bar can be provided with a side retainer 105
 on at least one end and/or on each opposite end. As shown in FIG. 14C, a
 bolt having on at least one end a slot 106 configured to receive a wedge
 107 is another form that the support member 33 can take.
 In an alternative embodiment shown in FIG. 4E, the manner of attachment of
 stanchion 25 to right leg 11 and left leg 12 differs from the embodiment
 of FIG. 4A for example insofar as the provision of at least one of a pair
 of shims 97. Each shim 97 has a main body that is configured to be
 interposed between one of the side panels 26 or 27 of stanchion 25 and the
 inwardly-facing side panel 14 of the corresponding mid portion 18 of each
 leg 11, 12. When the mid portions 18 are permanently attached to unitary
 tubular member 61 with a standardized spacing between the mid portions 18,
 each shim 97 facilitates the use of stanchions 25 of different widths in
 combination with an undercarriage composed of the mid portions 18 and the
 unitary tubular member 61 that forms the rear portions 17 of both legs 11,
 12 and provides for the permanent joining of both legs in a single unitary
 structure. For reasons of symmetry, it is preferable to install two
 identical shims 97, with one being disposed on each opposite side of
 stanchion 25. However, it is possible, though not recommended, to use a
 single shim on only one side of stanchion 25.
 As shown in FIG. 4E, each shim 97 can be configured with an L-shaped
 cross-section such that a lip portion 98 is disposed at a right angle to
 the main body of shim 97. Lip portion 98 is configured and disposed to
 rest on the top panel 15 of each leg 11, 12 and facilitates installation
 of shim 97.
 In this configuration shown in FIGS. 1A, 1B, 2A, 2B, 3A, 3B, 4A, 4B, 4C,
 4D, 4E, 8, 9, 11, 12A, 12B, 12C, 12D, 14A, 14B, 14C and 15A for example,
 stanchion 25 is supported at two locations along the length of support
 member 33. Moreover, the bearing surface contacting each location along
 the length of support member 33 is determined by the thickness of each
 side panel 26, 27 of stanchion 25. Support member 33 is in turn supported
 by two bearing surfaces provided by the side panels 13, 14 of each of the
 right leg 11 and the left leg 12. The location of the holes drilled
 transversely through the side panels 13, 14 of each of the left leg 12 and
 the right leg 11 can be adjusted so that they are more or less close to
 the top panel 15 forming the mid portion 18 of each leg. The more distance
 between the holes through the side panels 13, 14 and the bottom panel 16
 of the mid portion 18 of each leg, the more metal that is disposed beneath
 the bearing surface provided by each side panel 13, 14 of each leg and the
 more weight bearing capacity is believed to be provided by each leg.
 Moreover, the width of stanchion 25 automatically determines the
 separation between the mid portions 18 of the left leg 12 and the right
 leg 11 in the assembly shown in FIGS. 1A, 1B, 2A, 2B, 3A, 3B, 4A, 4B, 4C,
 4D, 8, 9, 11, 12A, and 12B for examples.
 In the configuration shown in FIGS. 1A, 1B, 2A, 2B, 3A, 3B, 4A, 4B, 4C, 4D,
 8, 9, 11, 12A, and 12B for example, stanchion 25 is pivotable about the
 lengthwise axis of support member 33 during assembly of the crane.
 As shown in FIGS. 4A and 1A for example, a boom 34 is pivotally connected
 to stanchion 25 at the top end 32 of stanchion 25 as by a mounting bolt 35
 mounted transversely through the opposed side arms of a U-shaped mounting
 member 76 that has its base portion attached to the top end 32 of
 stanchion 25. Bolt 35 is also mounted transversely through a back end 36
 of boom 34. The material forming the boom 34 desirably is rolled, low
 carbon steel, and the gauge of steel and the width and depth of the
 rectangular cross-section depends upon the desired lifting capacity of the
 crane. For example, if the crane is to have a lifting capacity of two (2)
 tons, three inch by four inch rectangular cross-section eight (8) gauge
 steel is desired for forming boom 34.
 Moreover, as shown in FIGS. 4A and 1A for example, and as is conventional
 in the art, boom 34 can have a telescoping member 37, which is provided at
 the end thereof with a chain 38 and an attachment device such as a hook
 39. The material forming the boom's telescoping member 37 desirably is
 rolled, low carbon steel, and the gauge of steel and the width and depth
 of the rectangular cross-section depends upon the desired lifting capacity
 of the crane. For example, if the crane is to have a lifting capacity of
 two (2) tons, two and one half inch by three and one half inch rectangular
 cross-section eight (8) gauge steel is desired for forming the boom's
 telescoping member 37. As shown in FIGS. 4A and 1A for example, a setting
 bolt 42 is removably disposed transversely of the free end 43 of boom
 extension 37 and through a link of chain 38, as is conventional in the
 art. As shown in FIG. 10 for example, telescoping member 37 is locked into
 a particular position by a locking pin 40 that is removably insertable
 transversely through the opposed side panels 41 of boom 34 and the nested
 portion of telescoping boom extension 37 contained within boom 34.
 As is conventional, the boom 34 is powered to perform the lifting function
 as it pivots with respect to stanchion 25. Such lifting force can be
 provided by a hydraulically operated cylinder such as a lifting ram 44
 shown in FIGS. 4A and 1A for example. Lifting ram 44 has a first end, and
 a second end disposed opposite the first end. Lifting ram 44 includes a
 conventional hydraulic cylinder member and a piston rod member. The piston
 rod member defines a rod connected at one end to a piston that is disposed
 within the cylinder member and thus is not visible in the view shown in
 FIGS. 4A and 1A. The rod has a free end disposed opposite the end
 connected to the piston. One end of the cylinder is at one end of the ram
 44, and the free end of the piston rod is at the other end of the ram 44.
 One of the cylinder member and the free end of the rod is pivotally
 connected to stanchion 25 between the base end 31 and the top end 32 of
 stanchion 25. As shown in FIGS. 8 and 1A for example, one end of the
 cylinder member is pivotally connected to stanchion 25 via a pair of
 mounting plates 45 and a mounting bolt 46 disposed transversely through
 mounting plates 45 and the mounting flanges 47 of the base of the cylinder
 member.
 The other of the free end of the rod and the cylinder member is pivotally
 connected to the boom 34. As shown in FIGS. 1A and 10 for example, the
 free end of the rod is pivotally connected to the boom 34 by a mounting
 flange 48 and a mounting bolt 49 that is transversely disposed through
 mounting flange 48 and the free end of the piston rod. As the piston rod
 moves in and out of the cylinder member, the boom 34 pivots about the back
 end 36 of the boom 34 and moves up and down with respect to the floor on
 which the crane is resting.
 A pair of support straps 50 is provided to help stabilize the stanchion 25
 and keep it centered between the right and left legs. As shown in FIGS.
 4A, 4B, 1A and 1B for example, a left support strap 50 defines a rigid
 member. Each rigid strap member 50 can be formed by flat bar steel
 measuring one quarter inch thick and one and one half inches wide and
 having a pair of opposed ends. The left strap 50 has one end connected to
 the stanchion 25 and the opposite end of the left strap 50 is connected to
 the left leg 12. As shown in FIGS. 4B and 1B for example, a fastening bolt
 52 is fitted transversely through the mid portion 18 of each leg and
 through one end of each of the left strap and the right strap (not visible
 in FIGS. 4B and 1B) and fastened thereto. As shown in FIGS. 4A and 1A for
 example, the other end of each strap 50 is connected to the stanchion 25
 by a fastening bolt 53 threaded transversely through stanchion 25 and
 through each of the left and right straps 50. Though not shown in FIGS.
 4A, 4B, 1A and 1B for example, a similar right strap 50 is provided on the
 opposite side of stanchion 25 and attached to right leg 11 so that the
 stanchion is held symmetrically between the straps 50 and the legs 11, 12.
 Each of the fastening bolts 52, 53 for the straps 50, whether through the
 legs or through the stanchion, can be fastened by threaded nuts and places
 the bolts 52, 53 under tension and the tubular members, whether stanchion
 25, the legs 11, 12 and/or spacer member 54, under compression.
 As shown in FIG. 5C for example, the support straps can take other
 configurations and dispositions on the legs. One end of each support strap
 51 can be attached to the outwardly-facing side panel 13 of the rear
 portion 17 rather than to the outwardly-facing side panel 13 of the mid
 portion 18 of each leg. Moreover, each support strap 51 can be configured
 with a 90.degree. twist 59 in order to accommodate this difference in the
 location of the attachment on each leg. These alternative embodiments of
 the support straps 51 with their twists 59 and attachment to
 outwardly-facing side panels 13 of the legs' rear portions 17 or
 forward-facing side panel of unitary back portion member 61, also can be
 applied to the other crane embodiments such as those shown in FIGS. 1A,
 2A, 3A, 4A, 8 for example.
 Because of the unique construction of the mobile lifting device of the
 present invention, it lends itself to easy disassembly for shipping and
 easy re-assembly by the end user once the disassembled device is received
 by the end user. Each of the left leg 12 and the right leg 11 can be
 disassembled from the stanchion 25, the support straps 50, and the spacer
 member 54 by removing the four (4) bolts 33, 52, 53, 55 that attach
 transversely through the side panels 13, 14 of the mid portion 18 of each
 leg and the side panels 26, 27 of the stanchion 25. Similarly, the casters
 24, 23 can be removed from each of the free ends of the forward portions
 19 and the rear portions 17 of the legs 11, 12. Each leg can be laid
 lengthwise in a box in a manner that forms the opposite mirror image of
 the other leg so that the rear portion 17 of one leg is adjacent the free
 end of the forward portion 19 of the other leg and the footprint of the
 two legs so aligned is rectangular. The top end 32 of the stanchion 25 can
 be disassembled by removing the mounting bolt 35 through the back end 36
 of the boom 34, and the boom 34 and the stanchion 25 also can be
 disassembled from the respective ends of the lifting ram 44. The boom 34,
 ram 44 and stanchion 25 can be laid lengthwise in the same box with the
 legs 11, 12 and the support straps 50 or 51. The casters 23, 24 and the
 spacer member 54 also can be fitted into the box along with the various
 bolts, nuts and pins. Thus, all of the components can be fitted into a
 rectangular box that has a relatively shallow depth that approximates the
 thickness of the tubular members forming the legs and the stanchion for
 example.
 The embodiment of FIGS. 8 and 9 is one of the presently preferred
 embodiments and resembles another presently preferred embodiment shown in
 FIG. 4A, but differs primarily in two respects. First, relative to the
 length of hydraulic a cylinder 44, the length of stanchion 25 is shorter
 in the embodiment of FIGS. 8 and 9 than in the FIG. 4A embodiment. To
 permit the boom 34 to be completely collapsed toward stanchion 25 in the
 storage position of the embodiment of FIGS. 8 and 9, a U-shaped mounting
 member 76 (FIG. 10) defines a pair of opposed arms 77 extending
 perpendicularly with respect to a base portion 78, which is attached to
 the underside panel 79 at one end of boom 34. Holes are drilled through
 the side panels 26, 27 of stanchion 25, and a bolt 35 is threaded through
 these holes and through corresponding holes drilled through the arms 77 of
 U-shaped mounting member 76.
 Another accommodation to the relatively shorter length of stanchion 25 in
 the embodiment of FIGS. 8 and 9 involves mounting flange 48, which is
 disposed in the mid-portion of boom 34. As shown in FIG. 10 for example,
 mounting flange 48 is provided with aligned holes through the opposite
 side arms 74, 75 of mounting flange 48. In the embodiment of FIG. 4A, the
 central axis of these aligned holes through mounting flange 48 is
 generally disposed in the middle of the side arms 74, 75 of mounting
 flange 48. However, in order to accommodate the collapse of boom 34 when
 the crane assumes the storage position shown in FIG. 9, the central axis
 of these aligned holes must be disposed toward the end of the side arms
 74, 75 of mounting flange 48 that is farthest away from the end on which
 U-shaped mounting member is 76 is attached.
 The second major difference between the presently preferred embodiments in
 FIG. 8 and FIG. 4A is the former's incorporation of a rolling member on
 the end of stanchion 25 opposite the end where U-shaped mounting member 76
 is pivotally attached. As shown in FIG. 11, this rolling member can be
 provided in the form of a wheel 80 that is part of a rolling assembly and
 carried rotationally on an axle 81 mounted between the side arms of a
 wheel mount 82 that is fixed, as by being welded or bolted or attached by
 some other fastening means, to the base end 31 of stanchion 25.
 As shown in FIG. 11, the wheel assembly can include a mounting plate 83
 that is welded to the base end 31 of stanchion 25, and wheel mount 82 is
 bolted to mounting plate 83. The rolling member is mounted to this plate
 83 in a manner so that the rolling member does not touch the floor surface
 so long as casters 24 (or other forms of mobility such as hooded wheels
 mounted on axles) are present on the leg extensions 56 on the ends of the
 legs. Thus, when the crane is in normal use, the rolling member on the
 base end 31 of the stanchion 25 does not bear any load. However, when
 telescoping leg extension members 56 are removed from legs 18, 19, the
 rolling member such as wheel 80 will touch the floor 90 as shown in FIG.
 13 for example, and facilitate the movement of the crane for purposes of
 storage.
 In accordance with one aspect of certain embodiments of the present
 invention, an adjustable attachment mechanism can be provided for
 attaching the rolling member to the base end 31 of the stanchion 25. The
 adjustable attachment mechanism can be configured to render the rolling
 member height adjustable. As shown in FIG. 12A for example, one form of
 vertically adjustable attachment mechanism can include a pair of opposed
 attachment flanges 115, 116 forming a slot therebetween. As shown in FIG.
 12B for example, the pair of opposed attachment flanges 115, 116 receive a
 portion 117 of the base end of the stanchion 25 in the slot formed between
 flanges 115, 116. As shown in FIG. 12A for example, a threaded hole 118 in
 one of the flanges 115 receives a threaded bolt 86 that can be tightened
 or loosened as desired to attach and adjust the wheel assembly and the
 vertical disposition (height off the floor) of the rolling member 80.
 As shown in FIG. 12C for example, another form of vertically adjustable
 attachment mechanism for the rolling member 80 can include a bolt 86 and a
 slide plate 84 that defines an elongated slot 85. The rolling member 80
 can be mounted on slide plate 84, and bolt 86 can be passed through slot
 85 to mount the slide plate 84 to the stanchion's front panel 28 at base
 end 31 of stanchion 25. Because of slot 85, the slide plate 84 can be
 adjusted to raise and lower the rolling member accordingly. The threaded
 shaft of bolt 86 can be screwed into a threaded hole 87 defined through
 the front panel 28 of stanchion 25. Alternatively, as shown for example in
 FIG. 12D, since stanchion 25 is a hollow tubular member, the hole 87 need
 not be threaded, and bolt 86 can receive a threaded nut 96 on the threaded
 end of bolt 86.
 Additional differences in the embodiment of FIG. 8 and FIG. 4A include a
 pair of storage eyelets 88 mounted on each side panel 26, 27 of stanchion
 25. Each storage eyelet 88 is configured so as to be able to receive a
 telescoping leg extension member 56, when member 56 is not attached to one
 of the portions 18, 19 of legs 11, 12. The storage eyelets 88 provide a
 convenient place to hold extension members 56 when the crane is being
 stored during periods of nonuse.
 Additionally, as shown in FIG. 10 for example, a channel 89 can be mounted
 transversely near the upper end of back panel 29 of stanchion 25 and can
 be configured to slidably receive therein the handle 91 that is used to
 pump the hydraulic cylinder 44. Thus, this handle 91 serves a dual
 function of providing leverage to pump the hydraulic cylinder when it is
 attached to the pumping sleeve 99 as shown in FIG. 8 for example. When
 handle 91 is removed from the sleeve 99 and is slidably received in the
 opening defined by channel 89, handle 91 provides leverage to the user who
 desires to steer the crane into a storage location or to move the crane
 when it is carrying a load from one location to another location.
 The crane of the present invention comprehends a number of alternative
 embodiments, some of which already have been introduced above. Each
 alternative embodiment shares like configurations and has some of the same
 structural components in common with other embodiments. Examples of some
 of these additional alternative embodiments and different combinations of
 structural components are now being described.
 In the alternative embodiment shown in FIGS. 2A and 2B, neither the left
 leg nor the right leg is formed as a unitary structure as in the
 embodiment shown in FIGS. 1A and 1B. In the embodiment of FIGS. 2A and 2B,
 each leg 11, 12 includes a telescoping leg extension member 56 that is
 attached to the free end of forward portion 19 as explained above in
 connection with the embodiments of FIGS. 4A and 8 for example.
 One advantage of the embodiment of FIGS. 2A and 2B over the embodiment of
 FIGS. 1A and 1B is the possibility of reducing the length of the shipping
 carton. Each leg 11, 12 can be disassembled into two smaller components in
 the embodiment of FIGS. 2A and 2B. Moreover, the length of each leg is
 adjustable in the embodiment of FIGS. 2A and 2B.
 Next, the embodiment partially shown in FIG. 3A is the same as the
 embodiment of FIG. 1A with the following exceptions. The FIG. 3A
 embodiment forms each leg from two separate tubular members that are
 joined together permanently as by a welded seam 60 at the vertex of the
 obtuse angle .alpha.. Thus, the forward portions 19 of the legs of the
 embodiment of FIG. 3A are welded to the mid portions 18 of the legs.
 The embodiment of FIG. 3B is the same as the embodiment shown in FIGS. 2A
 and 2B, except for the construction of each leg. In the FIG. 3B
 embodiment, each forward portion 19 of each leg is provided as a separate
 component from the unitary structure composing the mid portion 18 and rear
 portion 17 of each leg. The rear portions 17 and mid portions 18 are
 formed of a unitary tubular member having a second bend 21 forming the
 vertex of a right angle designated .beta. in FIG. 3B. Each forward portion
 19 of each leg is rendered integral with the mid portion 18 and rear
 portion 17 of each leg by means of a permanent connection such as a welded
 seam 60 between one end of each forward portion 19 and the otherwise free
 end of each mid portion 18 of each leg. The FIG. 3B embodiment thus
 requires additional manufacturing steps and materials relative to the
 embodiment of FIGS. 2A and 2B and is more costly to produce than the
 embodiments of FIGS. 2A and 2B. This is because the use of a bending tool
 to form the first bend 20 in the embodiments of FIGS. 2A and 2B is a much
 less costly operation to perform than a welding operation or another
 operation that permanently attaches the forward portion 19 of the leg to
 the mid portion 18 of the leg. However, the embodiments of FIGS. 3A and 3B
 do establish the possibility of substituting a means of permanent
 attachment such as welding to fabricate each leg and particularly at the
 juncture where the obtuse angle designated Alpha (.alpha.) in FIG. 3B is
 formed between the forward portion 19 and the mid portion 18 of each leg.
 An advantage of the embodiment of FIGS. 4A, 4B, 8 and 9 over the
 embodiments of FIGS. 1A, 1B, 2A and 2B is related to the unitary back
 portion member 61 that results in a permanently joined leg component. This
 permanent assembly reduces the unwanted effects of bending moments and
 ensures structural integrity and increased lifting capacity. It also
 eliminates the task of assembling the spacer member 54 on the part of the
 customer.
 One cost advantage of the embodiments of FIGS. 2A and 2B over the
 embodiments of FIGS. 4A, 4B, 8 and 9 is the replacement of a mechanical
 fastening step to attach the spacer 54 between the mid portions 18 of the
 legs for a welding step to attach the mid portions 18 of the legs to the
 unitary back portion member 61. Another cost advantage of the embodiments
 of FIGS. 2A and 2B over the embodiments of FIGS. 4A, 4B, 8 and 9 is the
 small packing carton that is possible because the spacer member 54
 disassembles from the legs and permits them to be placed against one
 another in the carton. The permanently assembled undercarriage provided by
 the combination of the unitary back portion member 61 and the legs,
 prevents such disassembly.
 The embodiment of FIG. 4C is like the embodiment of FIGS. 4A and 4B, except
 for the provision of the forward portion 19 of each leg being permanently
 attached to the mid portion 18 of each leg as by a means of permanent
 attachment such as a welded seam 60. Thus, the welded seam 60 shown in
 FIG. 4C substitutes for the bend 20 that orients the forward portion 19 at
 an obtuse angle designated Alpha (.alpha.) relative to the mid portion 18
 of each leg.
 The embodiment shown in FIG. 4D resembles the embodiment of FIG. 4A for
 example and differs from the embodiment of FIGS. 1A and 1B insofar as the
 provision of a unitary tubular member 61 that forms the rear portions 17
 of both legs and provides for the permanent joining of both legs in an
 integral undercarriage structure. However, the embodiment shown in FIG. 4D
 differs from the embodiment of FIG. 4A because the forward portion 19 of
 the embodiment shown in FIG. 4D is elongated rather than including a
 telescoping leg extension member 56 that is detachably connected to the
 forward portion 19 of each leg.
 The alternative embodiment shown in FIGS. 5A and 5B differs from the
 embodiment of FIGS. 2A and 2B in several respects insofar as the provision
 of a unitary member 61 that forms the rear portions 17 of both legs and
 provides for the permanent joining of both legs in a single integral
 structure. Thus, each leg has a unitary member composed of the forward
 portion 19 and the mid portion 18. Moreover, the mid portions 18 of both
 the left and right legs are permanently attached to a unitary member 61
 that functions as the rear portions 17 of both legs. The permanent
 attachment of the mid portions 18 of both legs to the unitary back portion
 member 61 can be effected as by welding a seam 62 for example.
 The embodiment of FIGS. 5A and 5B is the same as the embodiment of FIG. 4C,
 except for the method of attachment of the stanchion 25 to the mid
 portions 18 of both legs of the crane. As shown in FIG. 5B for example,
 the base end 31 of stanchion 25 is permanently attached to a top mounting
 plate 64, which sits atop the top panels 15 of the adjacently disposed mid
 portions 18 of the left leg 12 and the right leg 11. As shown in FIG. 5B
 for example, a welded seam 63 attaches base end 31 of stanchion 25 to top
 mounting plate 64. The two legs are attached to the unitary back member
 61, but are typically spaced apart a distance that is less than the width
 of the front panel 28 and back panel 29 of the stanchion 25, as shown in
 FIG. 5B for example.
 Desirably, as shown in FIG. 5B, the side panels 26, 27 of the stanchion 25
 should be disposed above the respective inwardly-facing side panels 14 of
 the mid portions 18 of the adjacent legs 11, 12. This is believed to be
 the best orientation for carrying the load that is supported by the is
 stanchion 25. As shown partially in phantom (dashed line) in FIG. 5B,
 desirably, a bottom mounting plate 65 is disposed against the bottom
 panels 16 of the mid portions 18 of the two legs so that the two legs are
 sandwiched between the top mounting plate 64 and the bottom mounting plate
 65 and fastened thereto as by bolts 66 such as those shown in FIG. 5B for
 example.
 The disadvantage of the embodiment shown in FIGS. 5A and 5B over the
 embodiment shown in FIG. 4C as well as the other embodiments of FIGS. 4A
 and 4B, 1A and 1B, 2A and 2B and 3A and 3B is in the difficulty in siting
 of the stanchion 25 symmetrically with respect to the legs as it is
 positioned atop the top panels 15 of the mid portions 18 of the legs. If
 the pre-drilled holes for the bolts 66 are not positioned correctly,
 whether the holes through the top and bottom panels 15, 16 of the mid
 portions 18 of the legs or the holes through the mounting plates 64, 65,
 the possibility exists for the stanchion to be positioned off-center. This
 poses challenges in the manufacturing process, and may lead to more costly
 manufacture due to rejects that result from improper siting of the holes,
 whether through the mounting plates 64, 65 or through the top and/or
 bottom panels 15, 16 of the mid portions 18 of each leg.
 The embodiment of FIG. 5C bears some resemblance to the embodiment of FIGS.
 2A and 2B as well as some resemblance to the embodiment of FIGS. 5A and
 5B. The embodiment of FIG. 5C differs from the embodiment of FIGS. 2A and
 2B in two main respects. First, the stanchion 25 is mounted on the top
 panels 15 of the mid portions 18 of the legs in a fashion similar to that
 shown in FIG. 5B for example, rather than disposed between the mid
 portions 18 of the legs and carried by a support member 33. In the
 embodiment of FIG. 5C, the top mounting plate 64 can be welded to the base
 end 31 of the stanchion 25.
 Second, the embodiment of FIG. 5C positions the inwardly-facing panels 14
 of the mid portions 18 of the legs in contact along the length of the mid
 portions 18 and thus does not include a spacer member 54 as is the case in
 the embodiment of FIGS. 2A and 2B for example. However, in the embodiment
 of FIG. 5C, each leg is formed of a unitary, rigid tubular member and is
 provided with a first bend 20 and a second bend 21 in a fashion similar to
 the embodiment of FIGS. 2A and 2B. Moreover, a connecting bolt 102 is
 disposed transversely through the mid portions 18 of the legs and so as to
 detachably connect the legs to each other. As an alternative to the
 connecting bolt 102, the legs can be permanently welded to each other
 along the length of the mid portions 18 of the legs. In addition, though
 not shown, a similar embodiment to the one shown in FIG. 5C can be
 provided in the same relationship as an embodiment such as shown in FIGS.
 1A and 1B such that leg extension members 56 like those in FIGS. 2A and 2B
 would not be required.
 The embodiment of FIG. 7 resembles the embodiment of FIG. 5C but differs
 from the embodiment of FIG. 5C primarily in the way that the stanchion 25
 is connected to the legs. In the FIG. 7 embodiment, a spacer 92 is
 disposed between each of a pair of side plates 93 and the stanchion 25,
 which is disposed on and straddling the top panels 15 of the mid portions
 18 of the legs. At least two bolts, and desirably a plurality of bolts 94,
 are disposed transversely through both side plates 93, both spacers 92 and
 the base end 31 of stanchion 25 to fasten these components together.
 Similarly, at least one and desirably two bolts 95 is/are disposed
 transversely through both side plates 93 and the mid portions 18 of the
 legs to fasten these components together.
 One cost advantage of the embodiments of FIGS. 5C and 7 over the
 embodiments of FIGS. 5A and 5B is the elimination of the additional
 permanent attachment steps needed to attach the mid portions 18 to the
 unitary back portion 61 of the legs. The mechanical fastening mechanism
 used in the FIG. 7 embodiment has the advantage of eliminating the need
 for careful centering of the stanchion 25 with respect to the legs, as
 this centering occurs automatically as a result of the symmetry of the
 mechanical fastening arrangement.
 The embodiment of FIG. 5D differs from the embodiment of FIGS. 5A and 5B in
 the configuration of the legs and the method of attachment of the two
 support straps 51 to the legs. As shown in FIG. 5D, the mid portions 18 of
 the legs are disposed at an obtuse angle (.alpha.) with respect to the
 forward portions 19 of the legs and also with respect to the rear portions
 19 of the legs. Moreover, the rear portions 17 of the legs are provided by
 a unitary tubular member 61. Additionally, as shown in FIG. 5D, the legs
 intersect one another and the top panels 15 of the tubular rigid material
 forming each leg are disposed in the same plane. Mounting bolts 66 attach
 the top mounting plate 64 to the top panels 15 of the proximal ends of the
 forward portions 19 of the legs rather than to the top panels 15 of the
 mid portions 18 of the legs.
 As shown in FIG. 5D, one end of each support strap 51 is attached to the
 outwardly-facing side panel 13 of the rear portion 17 of each leg rather
 than to the outwardly-facing side panel 13 of the mid portion 18 of each
 leg. Moreover, each support strap 51 has a 90.degree. twist 59 in order to
 accommodate this difference in the location of the attachment and to add
 additional strength.
 One cost disadvantage of the FIG. 5D embodiment relative to the embodiment
 of FIGS. 5A and 5B is the need to make several angular cuts and several
 angular welds during fabrication and assembly of the leg portions into an
 integral structure that is permanently attached to one another. This poses
 the possibility of mistakes that lead to rejects and waste, which
 increases the cost of production.
 In the FIG. 5D embodiment, the centerline designated by the numeral 67 is
 perpendicular to rear portions 17 of the legs. The angle Alpha (.alpha.)
 is in the range of 135 degrees to 160 degrees, so that the included angle
 between the forward portions 19 of the legs is in the range of 20 degrees
 to 45 degrees. For an included angle of 40 degrees for example, the angle
 Theta (.theta.) in FIG. 5D would be one half that, which is 20 degrees.
 The angle Beta (.beta.) in FIG. 5D is in the range of 100 degrees to 112.5
 degrees. The particular angle chosen depends upon the desired application
 of the crane and the requirements of the customer. Moreover, the
 embodiment of FIG. 5D can be provided in an alternative embodiment that
 forms each leg out of a unitary member rather than requiring a leg
 extension member 56.
 While preferred embodiments of the invention have been described using
 specific terms, such description is for illustrative purposes only, and it
 is to be understood that changes and variations may be made without
 departing from the spirit or scope of the following claims.