Apparatus for aligning trolleys

Apparatus, suitable for use on a crane having two trolleys, for indicating that a load suspended by two trolleys is skewed beyond a pre-selected angle of skew, said trolleys traveling parallel to each other along a pair of spaced transversely extending supports with one of said supports defining a reference surface aligned generally normal to the plane defined by the paths of travel of said trolleys, comprising:

• (a) first trolley follower means, carried by that trolley on said one support and cooperating with said reference surface, for establishing an axis generally parallel to the paths of travel of said trolleys, said axis and a reference point on the other trolley defining a plane, said trolleys when positioned with said axis and said reference point defining a plane substantially perpendicular to said reference surface establishing the "zero skew positions" of said trolleys;
• (b) inextensible means, connected at one end to said reference point on said other trolley, for flexibly joining together said trolleys;
• (c) extensible means, carried by that trolley on said one support, for applying constant tension to the other end of said inextensible means, the position of said other end of said inextensible means relative to a fixed point on said first trolley follower means when said trolleys are in a zero skew position defining the "reference position" of said other end of said inextensible means,
• whereby any relative displacement of said trolleys from a zero skew position to a skewed position forces said other end of said inextensible means away from said reference position and towards said one end of said inextensible means, said trolleys being aligned relative to one another by repositioning said trolleys until said other end of said inextensible means is in said reference position;
• (d) a switch;
• and
• (e) trip means, carried by said inextensible means, for actuating said switch in response to said other end of said inextensible means moving from said reference position to a first position and for de-actuating said switch in response to said other end of said inextensible means moving from said first position to said reference position, said trolleys when positioned to skew said load by an amount equal to said pre-selected angle of skew defining the "first position" of said other end of said inextensible means relative to said reference position, the position of said switch being an indication of the skewed condition of the load suspended by said trolleys.

Apparatus for warning that two trolleys of a crane under the control of an operator are misaligned relative to each other, said trolleys traveling parallel to one another and carrying a common load, one of said trolleys defining a reference axis perpendicular to the plane established by the parallel paths of travel of said trolleys, comprising:

• (a) flexible inextensible means, pivotally connected at one end to a reference point on the other trolley, for flexibly joining said trolleys;
• (b) tensioning means, carried by said one trolley, for applying constant tension to the other end of said inextensible means, said reference axis on said one trolley and the reference point established on the other trolley establishing a plane, said trolleys when positioned so that said plane is substantially perpendicular to the paths of travel of said trolleys defining the "zero skew positions" of said trolleys, said trolleys in said zero skew positions defining the "reference position" of said other end of said inextensible means whereby any relative displacement of said trolleys from a zero skew position to a skewed position forces said other end of said inextensible means away from said reference position, said trolleys being aligned whenever said other end of said inextensible means is in said reference position;
• (c) an alarm;
• and
• (d) actuating means, joined to said other end of said inextensible means, for actuating said alarm in response to said other end of said inextensible means moving from said reference position to a first position, said trolleys when misaligned relative to one another to the extent of imposing a pre-selected skewed condition on said load defining the "first position" of said other end of said inextensible means,
• whereby the operator controlling the position of said trolleys is alerted to the fact that said trolleys have been misaligned from a zero skewed position to the extent of imposing a skewed condition on said load by an amount at least as great as that skew resulting when said other end of said inextensible means moves from said reference position to said first position.

Apparatus for energizing an alarm to warn that two transversely spaced trolleys on a crane are misaligned, said trolleys being constrained to travel parallel to one another while suspending a common load, comprising:

• (a) uniformly extensible linking means for transversely linking together said trolleys, said linking means including an inextensible link and uniformly extensible tensioning means, connected to said inextensible link, for applying constant tension on said inextensible link, said inextensible link defining a reference point whose position is measured relative to a fixed point on one of said trolleys, said trolleys defining a first misaligned condition when a pre-selected degree of skew is imposed on said load and said reference point is in a second position relative to said fixed point, said trolleys defining an aligned condition when the skew on said trolleys is less than said pre-selected degree of skew and said reference point is in a first position relative to said fixed point;
• (b) a switch, disposed along said linking means and fixed relative to said one trolley, for energizing said alarm, said switch having an open and a closed position, tripping said switch from one of said open and closed positions to the other position has the effect of energizing said alarm;
• and
• (c) trip means, carried by said linking means, for tripping said switch from one of its positions to the other in response to said reference point moving from said first position to said second position,
• whereby said trolleys are aligned relative to each other when said trip means is in said first position and said alarm is de-energized, said switch being tripped and said alarm being energized to warn the crane operator that said load is skewed by an amount at least as much as said pre-selected degree of skew when said trolleys are misaligned relative to each other to the extent of imposing a skewed condition on said load in excess of said pre-selected degree of skew, said switch being repositioned and said alarm being de-energized when said reference point is returned to its first position.