Lift truckload carriage safety device

Claim 2

In a lift truck hoist mechanism having a load carriage connected to be raised and lowered relative to a vertically extending mast structure by means of a pair of flexible cable means from which said carriage is suspended, the combination of an arm pivotally mounted on said carriage and connected to be rotated from a reference position upon occurrence of substantially different amounts of tension in the two cable means, each of said cable means being connected to said arm on a respective side of the pivot point of said arm whereby failure of one of said cable means causes rotation of said arm in first angular direction from said reference position with a torque commensurate with the weight of the load carriage and a load carried thereby or failure of the other of said cable means causes rotation of said arm in an opposite direction from said reference position with a torque commensurate with said weight, a first stop means, rigid lever means pivotally mounted on said carriage and spaced adjacent said arm so that said arm strikes said lever means whenever said arm is angularly displaced predetermined distances in either direction from said reference position and thereafter pivots said rigid lever means with a torque commensurate with said weight upon further displacement of said arm, said first stop means being connected to said lever means whereby said first stop means is urged toward a first position with a force commensurate with aid weight, and a plurality of cooperating stop means spaced along said vertically extending structure, each of said cooperating stop means being engageable with said first stop means when said first stop means is located vertically adjacent one of said cooperating stop means and is being urged toward said first position, whereby upon failure of one of said cable means said first stop means engages the first of said cooperating stop means to which it becomes adjacent and locks said carriage in a fixed position relative to said vertically extending mast structure.

Claim 3

The combination according to claim 1 in which said mechanism includes spring means arranged to act between said load carriage and said first means to urge said first means away from said reference position, the empty weight of said load carriage causing sufficient tension in said cable means in the absence of failure of said cable means to overcome the force of said spring means, but whereby said spring means is operative to rotate said means away from said reference position upon failure of and loss of tension in both of said cable means.

Claim 4

The combination according to claim 1 in which said vertically extending mast structure comprises a fixed mast structure and a telescoping vertically movable mast structure adapted to be raised and lowered relative to said fixed mast structure, and in which said plurality of cooperating stop means are spaced along said vertically movable mast structure.

Claim 5

The combination according to claim 1 in which said vertically extending mast structure comprises a fixed mast structure and a telescoping vertically movable mast structure adapted to be raised and lowered relative to said fixed mast structure, and in which said plurality of cooperating stop means are spaced along said fixed mast structure.

Claim 6

The combination according to claim 1 having spring-detent means for maintaining said first stop means in a reference position in the presence of vibration in the absence of failure of one or both of said cable means.

Claim 7

The combiNation according to claim 1 having means for preventing rotation of said first stop means as said first stop means engages any of said cooperating stop means.

Claim 8

In a hoist mechanism having a load carriage connected to be raised and lowered relative to a vertically extending structure by means of a pair of flexible cable means which said carriage is suspended, in which failure of one or both of said flexible cable means creates an unsafe condition, the combination of a first arm pivotally mounted on said carriage, each of said cable means being connected to said first arm on an opposite side of the pivot point of said first arm and each being connected to said first arm at the same lever arm distance from said pivot point, whereby substantially equal tension on said cable means positions said first arm substantially at a reference angular position about said pivot point and failure of one or the other of said cable means causes said first arm to be pivoted in one direction or the other from said reference angular position with a torque commensurate with the weight of said load carriage and the load carried thereby; movable stop means including lever means pivotally mounted on said carriage and a first stop means connected to said lever means, said lever means being spaced from portions of said first arm on opposite sides of said pivot point to be engaged by one or the other of said portions of said first arm upon predetermined rotation of said first arm in one direction or the other from said reference angular position, so that predetermined rotation of said first arm in either direction from said reference angular position pivots said lever means and translates said first stop means in a predetermined direction to a stop position with a force commensurate with said weight; and a plurality of cooperating stop means fixedly spaced along said structure to be engageable by said first stop means when said first stop means is in said stop position, whereby upon failure of one of said cable means said first stop means engages the first of said cooperating stop means which it passes and locks said load carriage in a fixed position relative to said vertically extending structure.

Claim 9

In a hoist mechanism having a load carriage connected to be raised and lowered relative to a vertically extending structure by means of a pair of flexible cable means which said carriage is suspended, in which failure of one or both of said flexible cable means creates an unsafe condition, the combination of a first arm pivotally mounted on said carriage, each of said cable means being connected to said first arm on an opposite side of the pivot point of said first arm and each being connected to said first arm at the same lever arm distance from said pivot point, whereby substantially equal tension on said cable means positions said first arm substantially at a reference angular position about said pivot point and failure of one or the other of said cable means causes said first arm to be pivoted in one direction or the other from said reference angular position with a torque commensurate with the weight of said load carriage and the load carried thereby; movable stop means including lever means pivotally mounted on said carriage and a first stop means connected to said lever means, said lever means being spaced from portions of said first arm on opposite sides of said pivot point to be engaged by one or the other of said portions of said first arm upon predetermined rotation of said first arm in one direction or the other from said reference angular position, so that predetermined rotation of said first arm in either direction from said reference angular position pivots said lever means and translates said first stop means in a predetermined direction to a stop position with a force commensurate with said weight; and a plurality of cooperating stop means fixedly spaced along said structure to be engageable by said first stop means when said first stop means is in said stop position, whereby upon failure of one of said cable means said first stop means engages the first of said cooperating stop means which it passes and locks said load carriage in a fixed position relative to said vertically extending structure.

Claim 10

A lift truck hoist mechanism, comprising, in combination: a mast structure including a pair of vertically extending mast members laterally spaced apart from each other, each of said members having a pair of laterally extending flanges; a load carriage connected to be raise and lowered relative to said mast members, said load carriage extending between said mast members and carrying a plurality of rollers nested between said pairs of flanges of said mast members; load-engaging means affixed to said carriage and extending longitudinally from said load carriage beyond said mast members; an arm pivotally mounted on said carriage to pivot about a substantially longitudinal axis; a pair of flexible cable means adapted to raise and lower said carriage, each of said cable means being connected to said arm on an opposite side of the pivot point of said arm, whereby failure of one or the other of said cable means causes rotation of said arm in one or the other of two angular directions from a reference position for said first arm; lever means pivotally mounted on said carriage to pivot about a substantially lateral axis, said lever means being spaced from said arm so that rotation of said arm in said one angular direction from said reference position of said arm causes said lever means to pivot in a given angular direction from a reference position of said lever means and rotation of said arm in said other angular direction from said reference position of said arm causes said lever means in pivot in said given angular direction from said reference position of said lever means; a first stop means connected to said lever means to be translated longitudinally in a direction perpendicular to a line between the two supporting mast member as said lever means is pivoted in said given angular direction; and a pluralIty of cooperating vertically spaced stop means spaced along said mast structure to be engaged by said first stop means when said first stop means is translated longitudinally.

Claim 11

A lift truck hoist mechanism, comprising, in combination: a mast structure including a pair of vertically extending mast members laterally spaced apart from each other, each of said members having a pair of laterally extending flanges; a load carriage connected to be raise and lowered relative to said mast members, said load carriage extending between said mast members and carrying a plurality of rollers nested between said pairs of flanges of said mast members; load-engaging means affixed to said carriage and extending longitudinally from said load carriage beyond said mast members; an arm pivotally mounted on said carriage to pivot about a substantially longitudinal axis; a pair of flexible cable means adapted to raise and lower said carriage, each of said cable means being connected to said arm on an opposite side of the pivot point of said arm, whereby failure of one or the other of said cable means causes rotation of said arm in one or the other of two angular directions from a reference position for said first arm; lever means pivotally mounted on said carriage to pivot about a substantially lateral axis, said lever means being spaced from said arm so that rotation of said arm in said one angular direction from said reference position of said arm causes said lever means to pivot in a given angular direction from a reference position of said lever means and rotation of said arm in said other angular direction from said reference position of said arm causes said lever means in pivot in said given angular direction from said reference position of said lever means; a first stop means connected to said lever means to be translated longitudinally in a direction perpendicular to a line between the two supporting mast member as said lever means is pivoted in said given angular direction; and a pluralIty of cooperating vertically spaced stop means spaced along said mast structure to be engaged by said first stop means when said first stop means is translated longitudinally.

Claim 12

A hoist mechanism according to claim 8 wherein all of said cooperating stop means are located longitudinally on one side of said mast structure.

Claim 13

A hoist mechanism according to claim 8 having a recess for slidingly supporting said first stop means and preventing rotation of said first stop means, said first stop means being connnected to said lever means by a pin-and-slot connection, whereby rotation of said lever means causes translation of said first stop means without rotation of said first stop means.