Abstract:
A crane including a telescoping boom has a base boom member and an inner member slidably mounted in the base boom member with a first end projecting from the base boom member. The inner member includes first and second connector elements. A boom extension has a first end including first and second attachment elements. The boom extension also includes first and second spaced bracket assemblies and is shiftable between use and storage positions. A first support associated with the base boom member includes a holder for pivotably retaining the first bracket assembly and a second support has a rail projecting from the base section. A slider is slidably supported by the rail, and an actuator connected between the slider and the boom shifts the slider between a retracted position and an extended position relative to the base boom member. A method of deploying a boom extension is also disclosed.

Description:
FIELD OF THE INVENTION 
     The present invention is directed toward an automatically deployable boom extension and to a method of deploying same, and, more specifically, toward a boom having an actuator connected thereto for moving a portion of a boom extension away from the boom during a boom extension deployment and toward a method of controlling the actuator during the course of a boom extension deployment. 
     BACKGROUND OF THE INVENTION 
     To extend the reach of crane booms having telescopic boom sections, a side stowable jib or boom extension may be provided for connection to the nose assembly of the fly section or next adjacent boom section, as disclosed in U.S. Pat. Nos. 3,785,505, dated Jan. 15, 1974, and 4,483,447, dated Nov. 20, 1984. The entire contents of these patents are hereby incorporated by reference. 
     When moving the boom extension from a storage position on the side of the telescopic boom to a use position wherein the boom extension extends outwardly in alignment with the longitudinal axis of the boom, the boom extension is pivotally connected to one side of the nose assembly of the boom section and then swung around and connected to the other side of the nose assembly. The connections are made by a plurality of pins extending through aligned holes provided in the cooperating end portions of the boom extension and nose assembly of the fly section. 
     On relatively small cranes, holes on the boom extension can be aligned with holes on the boom by manually pulling one end of the boom extension away from the boom and pivoting the boom extension on an intermediate support until the openings on the extension come into alignment with the openings on the boom nose. Cranes such as the one disclosed in U.S. Pat. No. 3,785,505, for example, include a roller on the boom extension that is rolled up a short ramp to carry the boom extension onto a boom extension support on the boom. While this arrangement performs satisfactorily, if an operator inadvertently removes the safety retaining pin from the intermediate support, pulling the rear portion of the boom extension away from the boom could result in the entire boom extension detaching from the boom and severely injuring the operator. Additional safety devices therefore must generally be provided to minimize this problem. 
     Another approach to boom extension deployment has been developed for relatively small cranes. In such cranes, the rear portion of the boom extension slides toward and away from the boom on a slider mounted on a rail. The boom extension is retained on the slider by pins projecting in the direction of the front end of the boom. Therefore, even when the slider is in the extended position, the boom extension will not detach from the slider until it is moved in the direction toward the outward end of the boom, and the extension will not detach from the boom even if an operator accidentally removes the safety pin from the intermediate support before moving the rear portion of the boom. Even with relatively small cranes, however, it is difficult for an operator to move the heavy boom extension as required to ensure that the front end of the boom extension is aligned with openings on the boom. This arrangement has therefore not been widely adopted on small cranes and is impracticable for larger cranes having heavier boom extensions. 
     It would therefore be desirable to provide a boom extension that is easily shiftable from a storage position to a position wherein the boom extension can be connected to a boom regardless of the size of the boom extension and to provide a boom extension that will not readily detach from a boom. 
     SUMMARY OF THE INVENTION 
     These problems and others are addressed by the present invention, a first aspect of which comprises a crane that includes a telescoping boom having an outer boom member having a first end and an inner member slidably mounted in the outer boom member with a first end projecting from the outer boom member first end. The first end of the inner member includes a first connector element having an opening and a second connector element having an opening. The crane also includes a boom extension having a first end and a second end, the first end including first and second attachment elements each having an opening. The boom extension first side includes first and second spaced bracket assemblies. The boom extension is shiftable between a use position where the opening of the first attachment element is aligned with the opening of the first connector element and the opening of the second attachment element is aligned with the opening of the second connector element and a storage position where the boom extension overlies and is connected to first and second supports on the outer boom member and the second attachment element is spaced from the second connector element. The first support may be a holder for pivotably retaining the first bracket assembly and the second support may be a rail projecting from the outer boom member first side and a slider slidably supported by the rail. An actuator is connected between the slider and the boom for shifting the slider between a retracted position and an extended position relative to the outer boom member. 
     Another aspect of the invention comprises a method of deploying a boom extension on a telescoping crane boom that includes steps of providing a boom having an outer member having first and second supports and a telescoping inner member comprising a first end having first and second connector elements each having an opening where the second support may be a slider slidably mounted on a rail to be shiftable between a retracted and an extended position by an actuator. An aspect of the invention includes providing a boom extension having a first end including first and second attachment elements each having an opening, the boom extension having first and second bracket assemblies. The first bracket assembly is connected to the boom first support and the second bracket assembly is connected to the boom second support so that the first attachment element is spaced from the first connector element. The actuator is controlled to move the slider toward the extended position until the opening of a first attachment element is aligned with the opening of a first connector element. The first attachment element is connected to the first connector element. The boom extension is disconnected from the first and second supports by extending the inner member from the outer member, and the boom extension is pivoted about the boom extension first connector element until the opening of the second attachment element is aligned with the opening of the second connector element. Then the second attachment element is connected to the second connector element. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These aspects and features of the invention and other will be better understood after a reading of the following detailed description together with the attached drawings wherein: 
         FIG. 1  is a top plan view of a telescoping boom have having front and rear supports for holding a boom extension and a boom extension mounted on the front and rear supports in a stored position; 
         FIG. 2  is a top plan view of the telescoping boom and boom extension of  FIG. 1  with a rear end of the boom extension shifted away from the boom; 
         FIG. 3  is a top plan view of the boom extension and boom of  FIG. 2  with the telescopic boom partially extended and the boom extension shifted longitudinally from the position illustrated in  FIG. 2 ; 
         FIG. 4  is a side elevational view of the boom extension and boom of  FIG. 1 ; 
         FIG. 5  is an elevational view of the front boom extension support taken in the direction of arrows V-V of  FIG. 1 ; 
         FIG. 6  is an elevational view of the front boom extension support taken in the direction of arrows VI-VI in  FIG. 5 ; 
         FIG. 7  is a plan view of a first portion of the front boom extension support taken in the direction of arrows VII-VII in  FIG. 6 ; 
         FIG. 8  is a plan view of a second portion of the front boom extension support taken in the direction of arrows VIII-VIII in  FIG. 6 ; 
         FIG. 9  is a perspective view of the second portion of the front boom extension support; 
         FIG. 10  is an elevational view, partly in section, of the rear boom  20  extension support when the extension is positioned as in  FIG. 1 , taken in the direction of arrows X-X in  FIG. 1 ; 
         FIG. 11  is an elevational view, partly in section, of the rear boom extension support when the extension is positioned as in  FIG. 2 , taken in the direction of arrows XI-XI in  FIG. 2 ; 
         FIG. 12  is an elevational view taken in the direction of line XII-XII in  FIG. 11 ; 
         FIG. 13  is a first perspective view of the rear boom extension support when the extension is positioned as in  FIG. 1 ; 
         FIG. 14  is a perspective view of the rear boom extension support  30  when the extension is positioned as in  FIG. 2 ; 
         FIG. 15  is a perspective view of the rear boom extension support when the extension is positioned as in  FIG. 3 ; 
         FIG. 16  is a second perspective view of the rear boom extension support of  FIG. 1 ; and 
         FIG. 17  is a top plan view illustrating the boom extension swinging into a deployed position. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, which are for purposes of illustrating preferred embodiments of the invention only and not for the purpose of limiting same,  FIGS. 1-4  and  17  illustrate a boom  10  having a top  12 , a bottom  14  a first side  16 , a second side  18 , a rear end  20  and a front end  22 . Boom  10  further comprises a base section  24  and a plurality of telescoping sections  26  projecting from front end  22 . The telescoping end of the boom may be referred to hereinafter as the front of the boom and the opposite end of the boom may be referred to as the rear or base of the boom. These terms will also be used to describe the boom extension mounted on the side of the boom; that is the “front” of the boom extension is the portion closest to the telescoping portion of the boom when the extension is mounted on the boom even though the front and rear portions of the boom extension will change position as the boom extension swings into its use position (see, e.g.  FIG. 17 ). Relative directional terms such as “above” and “below” may also be used to refer to the boom in its normal operating position with the top  12  of boom  10  facing upwardly and bottom  14  facing the ground. 
     The front-most telescoping section  28  has a terminal end  30  having a first pair of upper and lower connector elements  32  on the first side  16  of boom  10  and a second pair of upper and lower connector elements  34  on second side  18  of boom  10 . First side  16  of boom  10  further includes a front boom extension support  36  and a rear boom extension support  38  for supporting a boom extension along the boom  10  in a storage position when the boom extension is not needed. 
     Boom extension  40  is also illustrated in  FIGS. 1-4  and includes a top  42 , a bottom  44 , a first side  46 , a second side  48 , a front end  50  and a rear end  52 . Front end  50  may be considered the base of the extension, to be mounted on the telescopic boom, as described below. Front end or base  50  includes diverging leg portions  54  each terminating in an attachment element. Leg portions  54  on first side  46  of extension  40  end in a first pair of attachment elements  56 , and leg portions  54  on second side  48  of extension  40  end in a second pair of attachment elements  58 . Each of the first and second pairs of attachment elements  56 ,  58  includes a hole or opening  60 . A front connector assembly  62  is mounted on first side  46  of boom extension  40  and is adapted to engage the front boom extension support  36  on boom  10 , and a rear connector assembly  64  is provided on first side  46  of boom extension  40  and is adapted to engage the rear boom extension support  38  on boom  10 . Rear end  52  comprises the top of the extension when it is mounted on the telescopic boom. 
     Front boom extension support  36  and front extension connector assembly  62  are illustrated in greater detail in  FIGS. 5-9 . Front boom extension  36  comprises a main plate  70  having a plurality of slots  72  connected to first side  16  of boom  10  by support  71  welded to first side  16  of boom  10 . Bolts  74  or similar fasteners extend through slots  72  in main plate  70  to connect main plate  70  to support  71 . This arrangement allows the position of main plate  70  to be adjusted relative to support  71  and boom  10  as necessary to ensure proper operation of the boom extension as described hereinafter. 
     A pair of upper spacing plates  76  extend perpendicularly from an upper portion of main plate  70 , a lower spacing plate  78  extends perpendicularly from a lower portion of main plate  70 , a pair of upper adjustable plates  80  is connected to upper spacing plates  76 , and a lower adjustable plate  82  is connected to lower spacing plate  78  in each case using bolts or similar fasteners  84 . Fasteners  84  extend through aligned openings in the spacing plates  76 ,  78  and adjustable plates  82 ,  84  and allow positions of the adjustable plates  80 ,  82  relative to first side  16  of boom  10  to be adjusted as necessary to ensure proper operation of the boom extension as described hereinafter. An alignment pin  86  is mounted on upper adjustable plates  80 , extends in the direction of front end  22  of boom  10 , and a has a generally circular cross section. An alignment tab  88  having an opening  89  projects from lower adjustable plate  82  also in the direction of front end  22  of boom  10 . 
     Front boom extension connector assembly  62  comprises an upper bracket  90  projecting normally from first side  46  of boom extension  40  which upper bracket  90  includes an alignment opening  92  configured to slidably receive alignment pin  86  on upper adjustable plate  80 . Alignment opening  92  is sufficiently larger in diameter than the diameter of alignment pin  86  to allow the boom extension  40  to pivot on pin  90  relative to boom  10  by at least several degrees for reasons described herein. 
     Front boom extension connector assembly  62  also includes a lower bracket  94  projecting normally from first side  46  of boom extension  40  and includes an alignment slot  96  somewhat larger than alignment tab  88  of lower adjustable plate  82  configured to receive alignment tab  88 . A locking pin  98  passes through opening  89  in alignment tab  88  to limit longitudinal movement of boom extension  40  relative to boom  10  while allowing the boom extension  40  to pivot by at least several degrees. 
     Rear boom extension support  38  and rear boom extension connector assembly  64  are illustrated in greater detail in  FIGS. 10-15 . With reference to  FIG. 10 , rear boom extension support  38  comprises upper and lower supports  100  welded to first side  16  of boom  10  and a support arm  102  having slots  104  connected to upper and lower supports  100  by bolts  106 . The bolt and slot arrangement allows the position of support arm  102  and to be adjusted as necessary. A rail  108  extends from support arm  102  and includes an upper surface  110  generally parallel to a lower surface  112 , the upper and lower surfaces being provided with wear pads  114  formed of a dense, low-friction plastic. 
     An electromechanical actuator  116  having a housing  118 , a motor  120  and a screw  122  is mounted to support arm  102 , and motor  120  is configured to drive screw  122 . A slider  124  having parallel upper and lower surfaces  126  each including a wear pad  128  slidingly engages rail  108  with the wear pads  128  of the slider in contact with the wear pads  114  of the rail  108 . Screw  122  of electromechanical actuator  116  connects to slider  124  to move the slider  124  from a first, retracted, position, illustrated in  FIG. 10  to a second, extended position, illustrated in  FIG. 11 , relative to rail  108  and boom  10 . Other types of actuators, including hydraulic actuators, could be used without departing from the scope of this invention. 
     An alignment wall  130  projects from slider  124  in the direction of front end  50  of boom extension  40 , and first and second support walls  132  project from slider  124  parallel to alignment wall  130 . First and second rollers  134  are rotatably mounted between first and second support walls  132 , and the roller closest to front end  50  of boom extension  40  is mounted at a lower elevation than the other roller  134 . First and second alignment pins  136  project from slider  124  in the direction of the front  50  of the boom extension  40 . 
     Boom extension rear connector assembly  64  comprises a frame  138  depending from bottom  33  of boom extension  40  which frame includes a ramp wall  140 , an alignment finger  142  illustrated in  FIG. 16 , and first and second alignment openings  144  configured to receive alignment pins  136  on slider  124 . 
     The deployment of boom extension  40  is discussed below. Boom extension  40  is mounted in a storage and transport position against first side  16  of boom  10 , as illustrated in  FIGS. 1 and 4 . Boom  10  can be used in a traditional manner with boom extension  40  safely stored on the side thereof. As illustrated in  FIG. 5 , in this configuration, alignment pin  86  of front boom extension support  36  projects through alignment opening  92  on the upper bracket  90  of front boom connector assembly  62 , and alignment tab  88  of boom extension support  36  projects through alignment slot  96  on lower bracket  94  of boom connector assembly  62  while locking pin  98  passes through opening  89  in alignment tab  88 . This arrangement substantially prevents boom extension  40  from separating from boom  10 . 
     Likewise, with reference to  FIG. 13 , alignment pins  136  on slider  124  project through alignment openings  144  on boom extension rear connector assembly  64  to secure the boom extension  40  to the slider  124 , and linear actuator  116  is powered down to retain slider  124  in a retracted position on rail  108  relative to boom  10 . In this configuration, as will be appreciated from  FIG. 1 , the first pair of attachment elements  56  on first side  46  of boom extension  40  are spaced from the first pair of connector elements  32  on the first side  16  of boom  10 . 
     To deploy boom extension  40  to a use position mounted on and aligned with boom  10  as illustrated in  FIG. 17 , linear actuator  116  is actuated by controller  146 , illustrated in  FIG. 17 . The controller is preferably mounted near the front end  22  of boom  10  and may be connected to linear actuator motor  120  by a wire  148  or using an RF transmitter if the linear actuator  116  is suitably equipped with an RF receiver. Linear actuator motor  118  drives screw  122  to move slider  124  and therefore boom extension  40  away from boom  10  toward the position illustrated in  FIG. 2 . 
     Slider  124  is driven away from boom  10  until the holes  60  in the first pair of attachment elements  56  on boom extension  40  are aligned with the holes  35  on the first pair of connector elements  32  of boom  10  as illustrated in  FIG. 2 . Controller  146  is preferably positioned close enough to connector elements  32  to enable an operator to observe the movement of the first pair of attachment elements  56  relative to the first connector elements  32  and turn off the linear actuator when all holes are aligned. Alternately, a stop  150  may limit the outward movement of slider  124  relative to rail  108  and be positioned such that the openings  35  in the first pair of connector elements  32  are aligned with the openings  60  in the first pair of attachment elements  56  when the motion of the slider  124  is arrested by the stop. Even when the stop is not used to align the holes  35  in the connection elements  32  with the holes  60  in the attachment elements  56 , a stop  150  is still preferably provided to prevent slider  124  from disengaging from rail  108 . When the holes in the connector elements  32  are aligned with the openings  60  in the attachment elements  56 , an operator inserts pins (not illustrated) through the first pair of aligned openings to secure a first portion of the boom extension  40  to boom  10 . 
     In this configuration, boom extension  40  is connected to boom  10  at three points: at first pair of connector elements  32 , at front connector assembly  62  and at rear connector assembly  64 . At this time, an operator removes locking pin  98  from alignment tab  88  and actuates a boom controller (not shown) to extend front-most telescoping section  28  of the boom from the boom base section  24  a small distance such as a foot or two to move the boom extension  40  into the position illustrated in  FIG. 3 . In this configuration, boom extension  40  is slid longitudinally off alignment pin  86  and alignment tab  88  of front boom extension support  32  and off alignment pins  136  of rear boom extension support  34 . Once free of the boom extension supports, and with the help of an operator who pushes the boom extension  40  or raises or lowers the front end  22  of boom  10  in a well known manner, boom extension  40  is caused to swing through an arc as illustrated in  FIG. 17  until the holes  60  in the second pair of attachment elements  56  align with the holes  35  in the second pair of connection elements  34 , at which time additional pins (not shown) are inserted through the aligned openings to secure the boom extension  40  to the boom  10 . After this assembly, the boom  10  together with boom extension  40  are operated in a conventional manner. 
     To stow boom extension  40 , the above steps are substantially reversed. Pins (not illustrated) are removed from second connector elements  34  freeing the second side  48  of boom extension  40  from the boom, and the operator pushes the boom extension (or manipulates the position of the boom) to swing boom extension  40  through an arc until it is more or less aligned with the boom  10  in the configuration illustrated in  FIG. 3 . While maneuvering boom extension  40  into this position, front-most telescoping portion  28  of boom  10  is not fully retracted. When the boom extension  40  is adjacent the side of boom  10 , in the configuration of  FIG. 3 , front-most telescoping portion  28  is retracted into boom housing  24  causing ramp wall  140  on rear connector assembly  64  ( FIG. 15 ) to engage rollers  134  and guide alignment openings  144  toward alignment pins  136  of rear boom extension support  34 . At the same time, alignment finger  142  overlaps alignment wall  130  ( FIG. 16 ) to further guide and secure the boom extension  40  to the boom  10 . Also the alignment pin  86  and alignment tab  88  of front boom extension support  36  engage the alignment opening  92  in bracket  90  and the alignment slot  96  in lower bracket  94 . At this time an operator installs locking pin  98  into alignment tab  88 . Linear actuator  116  is then operated to slide slider  124  on rail  108  toward boom  10  to pull boom extension  40  back into the storage position of  FIG. 1 . 
     With the above described system, even a large boom extension can readily be deployed by a sole operator while reducing the possibility of accidentally disconnecting a boom extension from the boom and injuring an operator or other property. The sole operator can also observe the position of the boom extension relative to the boom to align the openings without repeatedly walking back to the rear end of the boom and making further adjustments. Thus, when normal wear on the boom causes changes in the relative positions of elements of the boom and boom extension, the operator can correct for such wear by visual observation and use of the remote controller. The linear actuator further serves as a safety interlock and will substantially prevent the rear portion of the boom extension from being pulled away from the boom unless the actuator is used. 
     The present invention has been described herein in terms of an illustrated preferred embodiment. Various modifications and additions to this embodiment will become apparent to those skilled in the relevant arts upon a reading of the foregoing disclosure. It is intended that all such modifications and additions comprise a part of the present invention to the extent they come within the scope of the several claims appended hereto.