US3028977A - Safety stop mechanism - Google Patents

Description

April 10, 1962 M. R. BOWERMAN SAFETY STOP MECHANISM 2 Sheets-Sheet 1 Filed April 21, 1958 INVENTOR Myron R. Bowermcn April 10, 1962 Filed April 21, 1958 Fig.3.

M. R. BOWERMAN 3,02

SAFETY STOP MECHANISM 2 Sheets-Sheet 2 INVENTOR Myron R. Bowermon M 4% "W W tion.

United States Patent Ofiice 3,028,977 Patented Apr. 10, 1962 3,028,977 SAFETY STOP MECHANISM Myron R. Bowerman, Washington Township, Stark County, Ohio, assignor to The Alliance Machine Co., Alliance, Ohio, a corporation of Ohio Filed Apr. 21, 1958, Ser. No. 729,816 Claims. (Cl. 212-21) This invention relates to safety stop mechanisms and particularly to safety stop mechanisms for overhead cranes and the like.

There are times, during the operation of a crane, when the crane block will accidentally be brought up against the crane frame with such force that one or more cable reevings will be broken. When this occurs, the crane block will fall to the floor, often causing physical damage to plant and equipment and injury to men on the working floor. Various types of controls have been tried in an effort to provide some means for stopping the drive motors. These have not been entirely satisfactory for various reasons but primarily because the considerable amounts of rotary momentum in the motors, drives and cable drums are sufficient to carry the block with sufficient force to break the cables at unpredictable times. Various spring means have been proposed for mounting on the crane block, but these have generally been objectionable because of their bulkiness and added weight on the crane block.

I have invented a safety stop mechanism which overcomes the deficiencies of the heretofore proposed safety means. My invention will absorb the very considerable amounts of stored kinetic energy which are present when a crane block is raised without stopping against the crane frame.

In a preferred embodiment, I provide a crane mechanism comprising a frame, a lifting block depending from said frame on hoisting cables, means on the frame for raising and lowering the lifting block on said cables, and resilient means on the frame in the path of travel of the lifting block adapted to be contacted by the lifting block before reaching the frame and to exert increasing force against the moving block. Preferably, the resilient means are spaced bell cranks pivoted on the frame with one end in the path of the lifting block and compressible means acted on by the opposite end of the bell crank to be compressed with increasing resistance as the bell cranks are rotated.

In the foregoing general description, I have set out certain objects, advantages and purposes of the inven- Other objects, advantages and purposes of this invention will be apparent from the following description and the accompanying drawings in which:

FIGURE 1 is a side elevation of a preferred embodiment of my invention;

FIGURE 2 is an end elevation of the preferred embodiment of my invention shown in FIGURE 1;

FIGURE 3 is a view on the line III-III of FIGURE 2 partly in section;

FIGURE 4 is a section on the line lV-IV of FIGURE 3; and

FIGURE 5 is a section on the line V--V of FIGURE 3.

Referring to the drawings, I have illustrated a crane trolley having a frame provided with wheels 11 of conventional design. A hook block 12 carrying a lifting hook 13 is suspended on hoisting cables 14 from a hoist drum 15 Bell cranks 16 and 17 are journaled on pins 18 on a lifting beam 19 extending transversely of the frame 10. The bell cranks 16 and 17 are made up of spaced members, one on each side of the web 1921 of beam 19. One end 16a and 17a, respectively, of each member of each pair of bell crank members 16 and 17 extends below the lifting beam 19 in the path of the hook block 12 and are connected by a pin 20. A roller contact 21 is journaled on each of pins 20 to contact a cap 22 on the hook block 12. The other ends 16b and 17b of the paired members 16 and 17 lie beside the web 19a on opposite sides thereof. Parallel rows of Bellville spring washers 23 are mounted on spaced shafts 24 extending parallel to each side of the web 19a of the lift beam 19-. End plates 25 and 26 are slidably fitted on the ends of shafts 24 and bear against the Bellville springs. A hollow shaft 27 is fixed at one end to end member 25. The other end of shaft 27 is attached to a yoke 28 which passes around end member 26 and is fixed on a pin 29 through the end 17b of bell crank 17. A shaft30 is fixed at one end to end member 26 and extends through the hollow interior of shaft 27. The opposite end of shaft 30 is pivoted on a pin 31 in the end 1612 of bell crank 16.

The safety mechanism of this invention operates as follows: When the hook block 12 is raised by the hoist drum 15, the cap strikes the rollers 21 on the ends of the two bell cranks 16 and 17. If the conventional limit switch (not shown) fails to function, the bell cranks continue to raise. This causes bell crank 16 to draw rod 30 towards the left viewing FIGURE 2 and bell crank 17 to draw shaft 27 to the right viewing FIGURE 2, thereby drawing the end members 25 and 26 toward each other. This causes the Bellville springs 23 to be compressed and to gradually exert an increased resistance to the raising of the hook block, thereby absorbing the kinetic energy of the block so as to gradually bring the block to a stop. This gradual reduction in the speed of the block will bring it to a stop without breaking the lifting cables, whereas, if the block were brought against the lifting beam without this reduction in speed and energy, the lifting cables would in all likelihood snap.

While I have illustrated and described a present pre ferred embodiment of my invention, it will be understood that this invention will be otherwise embodied within the scope of the following claims.

I claim:

1. A hoisting mechanism comprising a frame, hoisting cables depending from said frame, a lifting block depending from said frame on said hoisting cables, means on the frame for raising and lowering the lifting block on said cables, a pair of bell crank means pivoted on the frame on opposite sides of the path of lift block travel having one end depending below the frame in the path of travel of the lifting block when raised and lowered, resilient means on the frame extending transversely of the direction of lift block travel of such size as to be capable of absorbing the kinetic energy of the moving lifting block and the raising and lowering means, connections from the other end of said bell crank means engaging the resilient means whereby increasing force is exerted on the bell crank and in turn on the lifting block as the block is raised in contact with said one end of the bell crank and striker means on the lifting block adapted to engage both bell crank means when the block is raised.

2. A hoisting mechanism comprising a frame, hoisting ropes depending from said frame, a lifting block depending from said frame on said hoisting ropes, means on the frame for raising and lowering the lifting block on said ropes, spaced pairs of bell crank means pivoted on the frame two on each side of the path of travel of the lifting block, each having one end directed toward the other and depending below the frame in the path of travel of the lifting block when raised and lowered, resilient means on the frame extending transversely of the direction of lift block travel of such size as to be capable of absorbing the kinetic energy of the moving lifting block and the raising and lowering means, between the other ends of said bell cranks, connections between the said other ends and the resilient means whereby increasing resistance to movement is exerted on the bell cranks as the lifting block is raised in contact with said one end of the bell cranks and striker means on the lifting block adapted to engage both bell crank means when the block is raised,

3. A hoisting mechanism comprsing a frame, hoisting ropes depending from said frame, a lifting block depending from said frame on said hoisting ropes, means on the frame for raising and lowering the lifting block on said ropes, a pair of spaced bell crank means pivoted intermediate their ends on the frame on opposite sides of the path of lift block travel, each having one end depending below the frame in the path of travel of the lifting block when raised and lowered, said one ends being directed toward each other, horizontally extending spring means on the frame of such size as to be capable of absorbing the kinetic energy of the moving lift block and the raising and lowering means, between the other ends of said bell cranks, connections between the said other ends and the spring means acting to compress the spring means when said one ends are moved toward the frame by the raising of the lifting block whereby increasing resistance to movement is exerted on the bell cranks as the lifting block is raised in contact with said one end of the bell cranks and striker means on the lifting block adapted to engage both bell crank means when the block is raised.

4. A hoisting mechanism comprising a frame, hoisting ropes depending from said frame, a lifting block depending from said frame on said hoisting ropes, means on the frame for raising and lowering the lifting block on said ropes, a lifting beam on the frame beneath the raising and lowering means, spaced paired bell crank means pivoted intermediate their ends on the lifting beam two on each side of the path of lift block travel, each having one end depending below the beam in the path of travel of the lifting block when raised and lowered, said end of each pair connected by a shaft carrying a roller, a pair of spaced parallel rods extending generally between the other ends of said bell cranks on each side of the lifting beam parallel to the length of the beam, comprcssible spring means on said rods of such size as to be capable of absorbing the kinetic energy of the moving lifting block and the raising and lowering means, means slidable on the rods connected to said other ends of said bell cranks acting to compress the spring means when said one ends are moved toward the lifting beam by the raising of the lifting block whereby increasing resistance to movement is exerted on the bell cranks as the lifting block is raised in contact with said one end of the bell cranks and striker means on the lifting block adapted to engage both bell crank means when the block is lifted.

5. A hoisting mechanism as claimed in claim 4 wherein the spring means are Bellville spring washers slidable on the parallel rods.

References Cited in the file of this patent UNITED STATES PATENTS 1,848,932 Brinley Mar. 8, 1932 1,867,450 Genzmer July 12, 1932 1,951,088 Feeley et al Mar. 13, 1934 1,975,094 Fitch Oct. 2, 1934 2,128,660 Moorhouse Aug. 30, 1938 2,260,634 Mullner Oct. 28, 1941 2,336,485 Knox Dec. 14, 1943 2,708,110 Clay May 10, 1955 2,778,506 Harry Jan. 22, 1957 2,844,431 Harnlett July 22, 1958 2,845,263 Gund July 29, 1958

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