Chain-type balance sling

Abstract

To prevent dangers such as breaking of the chain and dropping of a suspended load by suppressing the jumping up of a chain guide and preventing the chain from coming off a sprocket even when the chain moves forcefully during lifting in a chain type balance sling.SOLUTION: A chain-type balance sling 1 having a sprocket 15 provided on a central axis X of a main body 10 so as to be rotatable relative to the main body, and a pair of chain guides 17, 18 provided symmetrically with respect to the central axis of the main body at points close to the sprocket so as to be rotatable relative to the main body is provided with spring means that is rotationally biased in a direction that always presses the chain that is stretched between the sprocket and the chain guide while engaging with the sprocket, for example, tension springs 22, 23 that are stretched between a pair of chain guides and simultaneously rotationally bias them in opposite directions.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a chain-type balancing hoist that can automatically balance and lift loads that are difficult to balance, such as deformed steel structures, in a stable position. [Background technology]

[0002] The following Patent Document 1 describes a chain-type balancing hoist that includes a main body, a sprocket rotatably mounted on the main body, a pair of chain guides rotatably mounted on the main body above the sprocket, and a chain whose both ends are connected to a load and whose chain elements engage with the sprocket at approximately the middle so that it is stretched between the sprocket and the chain guide.

[0003] In this type of chain-type balancing hoist, when the chain is opened at a predetermined hoisting angle or more (for example, 60 degrees or more) and connected to a load, the hoisting device is started and the load is hoisted.The sprocket automatically rotates and the chain moves so that the center of gravity of the load is on the central axis of the balancing hoist, thereby achieving balance, even if the load is unbalanced.This has the advantage that operations such as lifting and inverting a load with an unbalanced center of gravity can be performed smoothly and in a stable position (see paragraphs 0033 to 0036, Figures 5 and 6 of Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4297486 Summary of the Invention [Problem to be solved by the invention]

[0005] When using such a chain-type balancing hoist to lift a load, it is rare for the chain to be balanced from the start when both ends of the chain are attached to the load; in most cases, the load is connected to the chain-type balancing hoist in an unbalanced state. The following explanation assumes the case where a single-center-of-gravity load W with a step is hoisted using a chain-type balancing hoist, with reference to Figures 5 and 6. Note that Figures 5 and 6 show substantially the same conditions as those in Figures 5 and 6 of Patent Document 1, respectively.

[0006] When this load W is placed on the floor (Figure 5), and both ends of the chain 20 are set at points P1 and P2 and lifted, as soon as the load W leaves the floor, the sprocket 15 rotates clockwise in the figure, and the chain 20 moves from the left side to the right side, transitioning to a balanced state as shown in Figure 6.

[0007] In particular, if the mass of the load W is large or if the misalignment (height difference and / or distance from the central axis X) between the two points P1 and P2 connecting the chain 20 is large, the sprocket 15 rotates at high speed during the transition from the initial setup state shown in Figure 5 to the balanced state shown in Figure 6. The chain 20 engaged with the sprocket 15 moves forcefully within the chain-type balancing hoist, causing the chain guide 17 to bounce up, potentially causing the chain 20 to become disengaged from the sprocket 15 (see Figure 7). If the chain 20 continues to be disengaged from the sprocket 15 within the chain-type balancing hoist, twisting of the chain 20 can occur, potentially leading to breakage even at loads below its intended working load. Furthermore, if this condition occurs, the chain will not move smoothly, preventing the transition to the balanced state shown in Figure 6. This can lead to uneven load distribution on both sides of the chain 20, potentially resulting in breakage of the chain. Chain breakage can lead to serious accidents, such as a dropped load.

[0008] Therefore, the problem that the present invention aims to solve is to provide a new structure that solves the above problems with chain-type balancing hoists, and that prevents the chain from coming off the sprocket by suppressing the jumping of the chain guide even when the chain moves forcefully when transitioning from an unbalanced state to a balanced state, thereby making it possible to avoid dangers such as chain breakage and the load falling. [Means for solving the problem]

[0009] In order to solve this problem, the present invention of claim 1 is a chain-type balance hoist characterized by having a main body, a sprocket mounted on the central axis of the main body so as to be rotatable relative to the main body, a pair of chain guides mounted symmetrically about the central axis of the main body at points close to the sprocket so as to be rotatable relative to the main body, a chain made up of many connected chain elements, both ends of which are connected to the load and the chain elements are engaged with the sprocket at approximately the middle part of the chain while passing between the sprocket and the chain guide, and spring means for rotationally biasing each chain guide in a direction pressing it against the sprocket via the chain.

[0010] The present invention according to claim 2 is characterized in that, in the chain-type balancing device according to claim 1, the spring means is a tension spring stretched between a pair of chain guides, and urges the pair of chain guides to rotate simultaneously in opposite directions. [Effects of the Invention]

[0011] According to the present invention of claim 1, the spring means always rotates the chain guide in the direction of pressing the chain element against the sprocket. Therefore, even if the chain moves forcefully within the chain-type balancing hoist when the mass of the load is large or when there is a large positional misalignment between the two points where the chain is connected, the chain can be prevented from bouncing up and coming off the sprocket, thereby preventing the chain from breaking or the load from falling.

[0012] According to the present invention as defined in claim 2, a pair of chain guides can be simultaneously urged to rotate in opposite directions by a single tension spring, so that the pressure acts on the chain symmetrically about the central axis of the main body, thereby more reliably achieving the above-mentioned effect. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is an overall front view of a chain-type balancing sling according to an embodiment of the present invention. FIG. [Figure 2] FIG. 1 is a front view of the main part of this chain-type balancing sling (the front main body plate is not shown). [Figure 3] FIG. 2 is a side view of the main part of this chain-type balancing sling. [Figure 4] 1A is a perspective view showing a sprocket used in this chain-type balancing hoist, and FIG. 1B is a perspective view showing the state in which chain elements are engaged with the sprocket. [Figure 5] This is a front view showing the state in which this chain-type balancing sling is set on an off-center sling with a difference in height at the suspension point. [Figure 6] FIG. 6 is a front view of the load lifted from the state of FIG. 5 to a balanced state. [Figure 7] FIG. 1 is a front view showing an inconvenient state in which the chain guide jumps upward when a hoist with an off-center center of gravity is hoisted using a chain-type balancing hoist of the prior art. BEST MODE FOR CARRYING OUT THE INVENTION

[0014] A chain-type balancing sling 1 (hereinafter simply referred to as "sling") according to one embodiment of the present invention will be described with reference to FIGS.

[0015] The sling device 1 has a main body 10. The main body 10 is made up of a pair of front and rear main body plates 10a, 10b that are connected and fixed together by fastening bolts 11a, 11b, 11c at a distance that is approximately the same as or slightly larger than the width dimension of a chain element (described later).

[0016] A hanging bolt 12 is provided on the top of the main body 10, and a master ring 14 is connected via a coupling 13. By passing a hook of a lifting device such as a crane (both not shown) through this master ring 14, it is possible to lift the main body using the lifting device.

[0017] A sprocket 15 is rotatably supported by a center bolt 16 at the center of the main body 10. The sprocket 15 used in this embodiment has a configuration in which two front and back plates 15a and 15b, each of which has a substantially regular pentagonal shape in plan view, are stacked with a predetermined distance between them, and protrusions 15c formed on each vertex of the front and back plates 15a and 15b have grooves 15d formed in accordance with the distance (FIG. 4(a)). Chain 20 is made up of alternating chain elements 21a oriented approximately perpendicular to the surfaces of sprocket front and back plates 15a, 15b (hereinafter referred to as "orthogonal chains") and chain elements oriented approximately parallel to the surfaces of sprocket front and back plates 15a, 15b (hereinafter referred to as "parallel chains"). Within sling 1, orthogonal chain 21a engages sprocket 15 with its pair of long side surfaces approximately abutting the side edge surfaces of sprocket front and back plates 15a, 15b, and parallel chain 21b engages sprocket 15 with one long side inserted into groove 15d of protrusion 15c (Figure 4(b)). The shape and dimensions of each part of sprocket 15 are designed to achieve this engagement state.

[0018] Above the sprocket 15, a pair of chain guides 17, 18 are rotatably supported by the fastening bolts 11a, 11b, leaving a chain passage between them and the sprocket 15. The pair of chain guides 17, 18 are arranged symmetrically at a predetermined distance from each other about the main body central axis X, which passes through the hanging bolt 12, the center bolt 16 which is the rotation axis of the sprocket 15, and the lower fastening bolt 11c.

[0019] The chain guide 17 is made up of a pair of chain guide front and rear plates 17a, 17b arranged side by side in the thickness direction of the main body 10 at a distance that is approximately the same as or slightly larger than the thickness of the chain element 21. Similarly, the chain guide 18 is made up of a pair of chain guide front and rear plates 18a, 18b arranged side by side in the thickness direction of the main body 10 at a distance that is approximately the same as or slightly larger than the thickness of the chain element 21.

[0020] As can be understood from the above description and Figures 2 to 4, within the hoisting device 1, the orthogonal chain 21a moves in the forward direction through the gap (chain passage) between the sprocket 15 and the chain guides 17, 18, and the horizontal chain 21b is configured so that one long side thereof fits into the groove 15d between the sprocket front and back plates 15a, 15b at the protrusion 15c, and the other long side thereof fits between the chain guide front and back plates 17a, 17b; 18a, 18b, and the entire chain 20 moves in a direction corresponding to the rotation direction as the sprocket 15 rotates.

[0021] Each chain guide 17, 18 is rotationally biased by a spring means in a direction that presses the chain 20 (chain elements 20a, 20b) against the sprocket 15. In this embodiment, the spring means are tension springs 22, 23 that are stretched between the chain guide 17 and the chain guide 18 (more specifically, between the front plate 17a of the chain guide 17 and the front plate 18a of the chain guide 18, and between the front plate 17b of the chain guide 17 and the front plate 18ba of the chain guide 18). The spring forces of the tension springs 22, 23 simultaneously bias the pair of chain guides 17, 18 to rotate in opposite directions, always pressing the chain 20 against the sprocket 15 and preventing it from bouncing up.

[0022] The use and operation of the chain-type balancing hoist 1 configured as above when hoisting a load W with an unbalanced center of gravity and a difference in height between the hoisting points P1 and P2 will be described with reference to FIGS. 5 and 6.

[0023] To set the sling 1 on a load W placed on the floor at a predetermined location, coupling 13 and master ring 14 are connected to hoisting bolt 12 attached to the top of the main body 10, a hook (not shown) of a lifting device (not shown) such as a crane is passed through master ring 14, and the lifting device is driven to move the sling 1 to the site of the load W. Then, couplings 24, 24 connected to both ends of chain 20 are set on locking devices 25, 25 attached to the top surface of the load W (FIG. 5). The slinging points P1, P2 at which chain 20 is set may be different as long as they are within a predetermined tolerance range, and the positional relationship between the center of gravity G of the load W and the sling 1 does not need to be considered. Because the load W shown in FIG. 5 has a stepped shape on its top surface, there is a difference in height between slinging points P1, P2 at which chain 20 is set, and the center of gravity G is offset from the central axis X of the sling main body 10. Therefore, the chain 20L set at the lower suspension point P1 is longer than the chain 20R set at the higher suspension point P2.

[0024] After the sling 1 is set on the load W in this way, the lifting device, such as a crane, is hoisted up to raise the load W. As the load W is raised, the misalignment between the sling points P1 and P2 is gradually eliminated, and the chain 20L set on the lower sling point P1 moves toward the opposite side as the sprocket 15 rotates. When the load W is completely lifted, the center of gravity G of the load W is on the central axis X of the sling body 10, and at this position the rotation of the sprocket 15 and the movement of the chain 20 stop (Figure 6).

[0025] If the mass of the load W is large or if there is a large difference in elevation between the two points P1 and P2 where the chain 20 is connected, the sprocket 15 may rotate at high speed within the hoisting device 1 when transitioning from the state shown in Figure 5 to the state shown in Figure 6, causing the chain 20 to move forcefully. However, even in such cases, the tension springs 22 and 23 always press the chain 20 against the sprocket 15 to prevent it from bouncing up, thereby preventing the chain 20 from coming off the sprocket 15 and preventing accidents such as breaking the chain 20 or causing the load to fall.

[0026] Although one embodiment of the present invention has been described above with reference to the accompanying drawings, the present invention is not limited to this embodiment and can be implemented with a wide variety of modifications and changes within the scope of the invention as defined by the claims. [Explanation of symbols]

[0027] 1 Chain type balance sling 10 Main Unit 10a, 10b Pair of main body plates 11a, 11b, 11c Fastening bolts 12 Hanging bolt 13 Coupling 14 Mastering 15 sprockets 16 Center bolt 17,18 Pair of left and right chain guides 17a, 17b; 18a, 18b Pair of front and rear chain guides 20 Chain 21 Chain elements 22, 23 Pull spring (spring means) 24 Coupling 25 Locking device X Center axis of the body W Unbalanced load P1,P2 Hanging point position

Claims

1. A chain-type balancing hoist comprising: a main body; a sprocket mounted on the central axis of the main body so as to be rotatable relative to the main body; a pair of chain guides mounted symmetrically about the central axis of the main body at points close to the sprocket so as to be rotatable relative to the main body; a chain comprising a number of connected chain elements, the chain having both ends connected to a load and having the chain elements engaging with the sprocket at approximately its midpoint while passing between the sprocket and the chain guide; and spring means for rotationally biasing each chain guide in a direction pressing it against the sprocket via the chain.

2. 2. A chain-type balancing sling according to claim 1, wherein said spring means is a tension spring stretched between a pair of chain guides, and urges the pair of chain guides to rotate simultaneously in opposite directions.

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