Device for Mounting and Dismounting Chain Blocks

1. Field of the Invention

The present invention relates to an improved device for mounting and dismounting a chain block to and from a suspension ring, said device being designed so that the hook of a chain block can be mounted and dismounted to and from a suspension ring held at a high place as by a load suspending tripod or a suspension ring connected to a support member at a high place inside or outside a building, easily, safely and positively by an operation from the ground.

2. Description of the Prior Art

For mounting and dismounting a chain block to and from the head of a load handling tripod, it has heretofore been common practice to tie one end of a single rope to the linking hook (hereinafter referred to simply as hook) of the chain block while passing the other end of the rope around a horizontal pin which connects a suspension ring to the lower surface of the head of the tripod, and to pull the other end of the rope downwardly to pull up the chain block so as to engage the hook of said chain block with said suspension ring.

With this method, however, since a single rope is used for pulling up, the twist in the rope affects the lifting operation such that the opening in the hook of the chain block does not always face to the suspension ring. Therefore, it is necessary that the chain block lifted to the high place be manually changed in direction to adjust the direction of the opening in the hook. This operation is difficult and entails danger particularly where the suspension ring is located at a high place which is far above the height of a man; thus, a joint operation of two or more persons is required. For dismounting, the rope is quickly and strongly pulled to cause quick ascent of the hook, with the lower edge of the opening in the hook outwardly kicking the suspension ring, the rope being then slackened by making use of an instant which precedes the restoration of the suspension ring to its original position, thereby disengaging the hook of the chain block from the suspension ring. In cases where the chain block is heavy or said instantaneous disengagement is not smoothly effected, however, the total weight of the chain block and hook is suddenly imposed on the tension rope portions, thus entailing danger on the operator while requiring high physical force and skill on the part of the operator. Further, since a violent tension is often applied to the rope in cases where a heavy chain block is pulled up or down by the rope tied at one end thereof to the hook of said chain block, the knot in the rope sometimes loosens, possibly leading to a free fall of the chain block.

An object of the present invention is to provide a chain block mounting and dismounting construction which eliminates the drawbacks described above and which makes it possible for a single operator to perform the mounting and dismounting operation easily, simply and safely without having to exert a violent force.

FIG. 1 is a perspective view showing the head portion of a tripod with an embodiment of the present invention mounted thereon;

FIG. 2 is a front view of the device;

FIG. 3 is a side view taken as indicated by the line III--III of FIG. 2;

FIG. 4 is a front view showing a hook mounted on a suspension ring; and

FIG. 5 is a front view showing another embodiment of the invention.

Embodiments of the invention will now be described. In FIGS. 1 through 4, a suspension member 4 is suspended from a top plate 3 which is placed on leg head members 2 connected to the upper end of a tripod 1 by fixtures 11 and which interconnects said leg head members 2 by bolts 12 and nuts 13. A horizontal pin 5 is inserted through the lower portion of said suspension member 4. Suspended from the opposite end extensions of the horizontal pin 5 is a U-shaped suspension ring 6 having support portions 6a pivotally mounted on the opposite end portions of the horizontal pin 5.

The upper ends of the opposed support portions 6a of the suspension ring 6 are bent at right angles in opposed relation to each other, forming rope slip-off preventive elements 6b. In use, a rope 7 is installed on said suspension member 4 such that it extends on both sides of said suspension member and through a space defined by said rope slip-off preventive elements 6b and support portions 6a while passing around said horizontal pin 5. One region of the rope 7 forms a continuous lifting portion 7a with a turn portion caught by the hook 9 of a chain block 8. The other region of the rope 7 is annularly knotted together or forms tension rope portions 7b without being knotted together. Nuts 10 are threadedly applied to both ends of the horizontal pin 5 to prevent it from slipping off.

At respective intermediate positions on the opposed arm portions 6c of the suspension ring 6, a strip-like guide 6e for suspension ring angle change engageable by the respective outer sides of said tension rope portions 7b is connected between said arm portions 6c in a bridge fashion projecting on the side which faces to the opening in said hook 9.

The device is used in the following manner.

When it is desired to bring the hook 9 into engagement with the suspension ring 6, the tension rope portions 7b are pulled each with substantially the same force in the direction of arrow P. This operation lifts the chain block 8 along with the hook 9 engaged by the lifting rope portion 7a. During this lifting operation, since the lifting rope portion 7a is pulled while being supported at two places on the horizontal pin 5, which is longer than the diameter of the suspension member 4, the hook 9 is held in such an attitude that its opening correctly faces to the suspension ring 6. In this state, continuing to pull up the hook 9 causes the hook top 9a of the hook 9 to push the suspension ring 6 obliquely around the axis of the horizontal pin 5 until the suspension ring is tilted to extend in the direction of the hook tip 9b along the outer edge of said hook top. Further pulling the tension rope portions 9b to lift the hook 9 disengages the suspension ring 6 from the hook tip 9 b and allows the suspension ring to turn around the axis of the horizontal pin under its own weight back toward the opening in the hook 9. Finally, the tension rope portions are slightly slackened to allow the hook 9 to engage the suspension ring 6, establishing the perfect linkage state shown in FIG. 4. During this series of operations, the range of pulling direction of the tension rope portions 7b is preferably such that the rope does not at all contact the suspension ring direction change strip-like guide 6e of the suspension ring 6 or even if it contacts, it does so lightly.

When it is desired to remove the hook from the suspension ring 6, as shown in FIG. 3, the pulling direction of the tension rope portions 7b is adjusted such that when the hook 9 is not linked to the suspension ring 6, the strip-like guide 6e is urged by the tension rope portions 7b to move upwardly until the drooping portion 6d of the suspension ring lies off the path of movement of the hook 9. That is, an increased angle of the suspension ring 6 with the vertical is adopted and the suspension ring 6 is further lifted by pulling the tension rope portions 7b, whereupon the engagement between the suspension ring 6 and the hook 9 is automatically canceled. Thus, if the tension rope portions 7b are then gradually slackened, disengagement can be effected easily and safely, enabling the hook 9 to descend.

The suspension member 4 may not necessarily but preferably be rotatable relative to the top plate 3 from the standpoint of easier operation.

FIG. 5 shows another embodiment of the invention, wherein grooved pulleys 13 are mounted for free rotation on the horizontal pin 5 and the rope 7 is fitted in the grooves of the pulleys. According to this embodiment, friction on the rope 7 is decreased to provide for smooth mounting and dismounting operation.

As has been described so far, according to the present invention, a suspension ring is pivotally supported on a horizontal pin inserted through a suspension member supported by a support member mounted on the head portion of a tripod or disposed at a high place on a building, and a rope is installed to extend on both sides of said suspension member and around said horizontal pin, with the continuous lifting rope portion engaged by the linking hook of a chain block. Therefore, when the chain block is being lifted by pulling the tension rope portions, the hook tip of the hook is maintained correctly opposed to the suspension ring, making it unnecessary to manually adjust its direction. Therefore, the mounting and dismounting of the chain block to and from the suspension ring can be effected by a single operator and, moreover, ground operation is easy and safe.

Further, at respective intermediate places on the opposed arm portions of the suspension ring, a guide for suspension ring angle change is connected between said arm portions in a bridge fashion projecting on the side which faces to the opening in the hook. Therefore, the mounting and dismounting of the chain block can be safely, positively and easily effected by pulling the tension rope portions in the direction which forces the drooping portion of the suspension ring away from the path of upward and downward movement of the hook and then slackening said rope portions.