Two-way push-pull chain and reciprocating actuator

A link member includes a first pin hole, a second pin hole, a first engaging portion, and a second engaging portion. The second pin hole is an elongated hole extending in a longitudinal direction of a two-way push-pull chain. The pin is movably inserted into the second pin hole and fixed to the first pin hole. With the pin being movably inserted into the second pin hole, adjacent link members are expandable and contractible relative to each other by a length. The length is greater than a length of a portion where the first engaging portion contacts the second engaging portion in a state where the adjacent link members are contracted relative to each other.

BACKGROUND OF THE INVENTION

This application claims the benefit of Japanese Patent Application No. 2012-231027 filed Oct. 18, 2012, the entire content of which is incorporated herein by reference.

The present invention relates to a two-way push-pull chain formed by connecting a plurality of link members by means of pins, and a reciprocating actuator having the two-way push-pull chain.

There is known a two-way push-pull type block chain formed by connecting a plurality of link members by means of pins as disclosed in Japanese Patent Laid-Open No. 6-286834, Japanese Patent Laid-Open No. 2011-251795, and Japanese Utility Model Laid-Open No. 3-105191. For example, as illustrated inFIGS. 7A and 7B, a block chain700is formed by connecting a plurality of link members710arranged along a longitudinal direction Y by means of pins720. When the drive force of an unillustrated sprocket is transmitted to the block chain700, the block chain700slides on a guide portion G. Accordingly, the block chain700moves back and forth in the longitudinal direction Y.

The conventional block chain700is structured to mesh with the outer peripheral surface of the sprocket while being bent around the pin720. Thus, when the block chain700is pressed from both ends thereof on the guide portion G, a part of the block chain700may be spaced apart from the guide portion G, as illustrated inFIG. 7B, and buckled, which prevents the block chain700from being moved by pushing the end portion thereof to a desired position.

In other words, the conventional block chain700does not satisfy both the need to mesh the block chain700with the outer peripheral surface of the sprocket by freely bending the block chain700and the need to move the block chain700by pushing the end portion of the block chain700to a desired position without buckling the block chain700. The chain disclosed in Japanese Utility Model Laid-Open No. 3-105191 is structured to be bendable in only one direction by causing a projecting piece of the link member to abut against adjacent link members. Thus, the chain cannot mesh with the outer peripheral surface of the sprocket by bending the chain freely, and the chain may be buckled in a direction opposite to the bending direction of the chain.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a two-way push-pull chain satisfying both the need to mesh a chain with an outer peripheral surface of a sprocket by permitting free bending of the chain and the need to push an end portion of the chain to a desired position without buckling the chain and to provide a reciprocating actuator having the two-way push-pull chain.

In order to solve the above problems, a first aspect of the present invention provides a two-way push-pull chain formed by connecting a plurality of link members arranged along a longitudinal direction of the two-way push-pull chain by means of pins and having a first end and a second end. The second end is opposite to the first end. The link member includes: a first pin hole provided on the first end of the link member; a second pin hole provided on the second end of the link member; a first engaging portion provided on the first end of the link member; and a second engaging portion provided on the second end of the link member and engageable with the first engaging portion of an adjacent link member. Either of the first pin hole and the second pin hole is an elongated hole extending in the longitudinal direction and the other pin hole is a fixing hole. The pin is movably inserted into the elongated hole and fixed to the fixing hole. With the pin being movably inserted into the elongated hole, adjacent link members are expandable and contractible relative to each other by a predetermined length. The predetermined length is greater in the longitudinal direction that the length of a portion in which the first engaging portion contacts the second engaging portion in a state where the adjacent link members are contracted relative to each other.

In order to solve the above problems, a second aspect of the present invention provides a reciprocating actuator having the two-way push-pull chain. The reciprocating actuator includes: a two-way push-pull chain; a sprocket meshing with the two-way push-pull chain to transmit power to the two-way push-pull chain; an actuated portion attached to the first end of the two-way push-pull chain and moved by a push/pull action of the two-way push-pull chain; and a guide portion guiding the first end of the two-way push-pull chain and the actuated portion in a forward and backward direction.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

The following is a description of a reciprocating actuator10according to a first embodiment of the present invention and a two-way push-pull chain100of the reciprocating actuator10with reference toFIGS. 1 to 4B. In the following description, a chain longitudinal direction and a chain lateral direction will be described as a longitudinal direction Y and a lateral direction X respectively.

As illustrated inFIG. 1, the reciprocating actuator10includes: the two-way push-pull chain100, a sprocket S, an actuated portion M, and a guide portion G. The sprocket S meshes with the two-way push-pull chain100to transmit power to the two-way push-pull chain100. The actuated portion M is attached to a first end of the two-way push-pull chain100and moved by a push/pull action of the two-way push-pull chain100.

The guide portion G guides the first end of the two-way push-pull chain100and the actuated portion M in a forward and backward direction thereof. This makes it possible to push and pull the actuated portion M by the first end of the two-way push-pull chain100. The actuated portion M is configured to be attachable to a sensor or a camera. For example, the actuated portion M can enter and leave the inside of a hole of an object to be inspected and the inside of a tubular body.

The second end of the two-way push-pull chain100is fixed to a fixing portion H. The two-way push-pull chain100is expandable and contractible in the longitudinal direction Y by an external force and/or its own weight. In the two-way push-pull chain100, the weight of the two-way push-pull chain100acts on a portion between the fixing portion H and the sprocket S. Thus, as illustrated by100A inFIG. 1, the portion between the fixing portion H and the sprocket S in the two-way push-pull chain100is always in tension and extended downward.

When the sprocket S is rotated counterclockwise inFIG. 1, the first end of the two-way push-pull chain100moves to the left and pushes the actuated portion M to the left inFIG. 1while being guided by the guide portion G. At this time, the weight of a portion including the actuated portion M and the first end of the two-way push-pull chain100acts on a portion in the two-way push-pull chain100between the actuated portion M and the sprocket S. Thus, as illustrated by100B inFIG. 1, the portion of the two-way push-pull chain100between the actuated portion M and the sprocket S is contracted and under compression because it is pushed by both a portion near the actuated portion M and a portion near the sprocket S.

When the sprocket S is rotated clockwise inFIG. 1, the first end of the two-way push-pull chain100moves to the right and pulls the actuated portion M to the right inFIG. 1while being guided by the guide portion G. At this time, the weight of a portion including the actuated portion M and the first end of the two-way push-pull chain100acts on a portion in the two-way push-pull chain100between the actuated portion M and the sprocket S. Thus, as illustrated by100A inFIG. 4A, the portion of the two-way push-pull chain100between the actuated portion M and the sprocket S is expanded and under tension because it is pulled from both a portion near the actuated portion M and a portion near the sprocket S.

Then, the configuration of the two-way push-pull chain100will be described in further detail.

As illustrated inFIGS. 2 to 4B, the two-way push-pull chain100is configured by connecting a plurality of link members110arranged along the longitudinal direction Y each by means of a pin120. The link member110includes a first pin hole111, a second pin hole112, a first engaging portion113, and a second engaging portion114. The first pin hole111is provided on the first end of the link member110.

The second pin hole112is provided on the second end of the link member110, opposite to the first pin hole111. The first engaging portion113is provided on the first end of the link member110. The second engaging portion114is provided on the second end of the link member110, opposite to the first engaging portion113. The second engaging portion114is engageable with the first engaging portion113of the adjacent link member110.

The second pin hole112is an elongated hole extending in the longitudinal direction Y. The pin120is movably inserted into the second pin hole112and is fixed to the first pin hole111. With the pin120being movably fitted into the second pin hole112, the adjacent link members110are expandable and contractible relative to each other by a length L1. As illustrated by100B inFIG. 4B, L2 denotes the length in the longitudinal direction Y of a portion where the first engaging portion113contacts the second engaging portion114in a state where the adjacent link members110are contracted relative to each other. The length L1 is greater than the length L2. Thus, as illustrated inFIG. 4A, the first engaging portion113can be disengaged from the second engaging portion114in a state where the adjacent link members110are expanded away from each other. When the link members110are expanded relative to one another, the two-way push-pull chain100can be bent in any direction.

As illustrated by100B inFIG. 4B, the first engaging portion113contacts the second engaging portion114in a state where the adjacent link members110are contracted relative to each other. Accordingly, the two-way push-pull chain100is not bent in any direction. In this case, the two-way push-pull chain100is switched between a state where the adjacent link members110are expanded relative to each other and a state where the adjacent link members110are contracted relative to each other by an external force and/or its own weight. At this time, the adjacent link members110are switched between a state where the first engaging portion113is engaged with the second engaging portion114and a state where the first engaging portion113is disengaged from the second engaging portion114.

In the latter case, the two-way push-pull chain100can be meshed with the outer peripheral surface of the sprocket S. In the former case, the portion including the first end of the two-way push-pull chain100can be moved to a desired position by being pushed forward without being buckled in the manner ofFIG. 7B. Specifically, as illustrated inFIG. 3B, the link member110is formed such that the first end of the link member110contacts both end portions of the second end of the adjacent link member110, that is, the link member110is formed like a so-called offset link. In other words, the link member110is formed such that the first pin hole111is located outward of the second pin hole112.

Further, according to the first embodiment, the first engaging portion113is a projected portion projecting in the longitudinal direction, and the second engaging portion114is a recessed portion shaped to receive and engage with the first engaging portion113. Accordingly, the first engaging portion113meshes with the second engaging portion114in a state where the adjacent link members110are contracted relative to each other. Accordingly, the two-way push-pull chain100is prevented from bending in any direction.

As illustrated inFIGS. 4A and 4B, the first engaging portion113includes a first surface113aand a second surface113b. Likewise, the second engaging portion114includes a first surface114aand a second surface114b. The first surfaces113aand114aand the second surfaces113band114bextend in substantially the same direction as a radius of the pin120. Thus, even if a bending force acts on the two-way push-pull chain100, a component force hardly acts on each of the first surfaces113aand114aand the second surfaces113band114b. Therefore, the force for regulating the bending of the two-way push-pull chain100is maximized.

In addition, the first surface113aof the first engaging portion113is parallel and opposite to the first surface114aof the second engaging portion114. Likewise, the second surface113bof the first engaging portion113is parallel and opposite to the second surface114bof the second engaging portion114. Thus, when the adjacent link members110expand and contract relative to each other, the force for regulating the bending thereof can be maximized and the adjacent link members110can smoothly expand and contract relative to each other.

The first embodiment has the following effects.

(1) The link member110has the first pin hole111, the second pin hole112, the first engaging portion113, and the second engaging portion114. The second pin hole112is an elongated hole extending in the chain longitudinal direction Y. The pin120is movably inserted into the second pin hole112and fixed to the first pin hole111. With the pin120being movably inserted into the second pin hole112, the adjacent link members110are expandable and contractible relative to each other by the length L1. The length L1 is greater than the length L2 (measured in the longitudinal direction of the chain100) of a portion where the first engaging portion113contacts the second engaging portion114in a state where the adjacent link members110are contracted relative to each other. This configuration allows the two-way push-pull chain100to be meshed with the outer peripheral surface of the sprocket S and to be pushed forward without buckling a portion that includes the first end of the two-way push-pull chain100. In other words, this configuration can satisfy both the need to mesh the two-way push-pull chain100with the outer peripheral surface of the sprocket S by permitting free bending of the two-way push-pull chain100and the need to move the chain100by pushing the first end of the two-way push-pull chain100to a desired position without the occurrence of buckling.

(2) The first engaging portion113is a projected portion projecting in the longitudinal direction Y and the second engaging portion114is a recessed portion engaging with the first engaging portion113. This configuration can reliably allow the two-way push-pull chain100to be pushed without buckling the portion that includes the first end of the two-way push-pull chain100.

(3) The first engaging portion113includes the first surface113aand the second surface113b. Likewise, the second engaging portion114includes the first surface114aand the second surface114b. The first surfaces113aand114aand the second surfaces113band114bextend both in the longitudinal direction Y and in the lateral direction X. This configuration reliably permits the two-way push-pull chain100to be pushed forward without buckling the portion that includes the first end of the two-way push-pull chain100.

(4) The reciprocating actuator10includes the two-way push-pull chain100, the sprocket S, the actuated portion M, and the guide portion G. This configuration allows the two-way push-pull chain100to be meshed with the outer peripheral surface of the sprocket S and to be pushed forward without buckling the portion that includes the first end of the two-way push-pull chain100.

Second Embodiment

There follows a description of a two-way push-pull chain200according to a second embodiment of the present invention with reference toFIGS. 5A and 5B.

The two-way push-pull chain200reverses the relationship between the recessed portion and the projected portion of the first engaging portion113and the second engaging portion114of the two-way push-pull chain100according to the first embodiment. In the following description of the two-way push-pull chain200, the description of matters common to the two-way push-pull chain100according to the first embodiment will be omitted, and the reference numerals of the second embodiment (the200series) have the same lower two digits as corresponding reference numbers of the first embodiment.

As illustrated inFIGS. 5A and 5B, a first engaging portion213is a recessed portion and a second engaging portion214is a projected portion engaging with the first engaging portion213. Thereby, the first engaging portion213meshes with the second engaging portion214in a state where adjacent link members210are contracted relative to each other. Accordingly, the two-way push-pull chain200cannot be bent in any direction.

In addition, the first engaging portion213includes a first surface213aand a second surface213b. Likewise, the second engaging portion214includes a first surface214aand a second surface214b. The first surfaces213aand214aand the second surfaces213band214bextend both in the longitudinal direction Y and in the lateral direction X. According to this configuration, even if a bending force acts on the two-way push-pull chain200, a component force does not occur on each of the first surfaces213aand214aand the second surfaces213band214b. Therefore, the force for regulating the bending of the two-way push-pull chain200is maximized. In other words, the two-way push-pull chain200, in which the relationship between the recessed portion and the projected portion of the first engaging portion213and the second engaging portion214is reversed, provides the same effects as the two-way push-pull chain100of the first embodiment.

Third Embodiment

There follows a description of a two-way push-pull chain300according to a third embodiment of the present invention with reference toFIGS. 6A and 6B.

The two-way push-pull chain300changes the shape of the first engaging portion113and the second engaging portion114of the two-way push-pull chain100of the first embodiment. In the following description of the two-way push-pull chain300, descriptions common to the two-way push-pull chain100of the first embodiment will be omitted, and the reference numbers of the third embodiment (the300series) have the same lower two digits as the corresponding reference numbers of the first embodiment.

As illustrated inFIGS. 6A and 6B, a first engaging portion313is a recessed portion and a second engaging portion314is a projected portion engaging with the first engaging portion313. Thereby, the first engaging portion313meshes with the second engaging portion314in a state where adjacent link members310are contracted relative to each other. Accordingly, the two-way push-pull chain300cannot be bent in any direction. In addition, the first engaging portion313includes a first surface313aand a second surface313b. The first surface313afaces the longitudinal direction Y; and the second surface313bextends both in the longitudinal direction Y and in the lateral direction X. Likewise, the second engaging portion314includes a first surface314aand a second surface314b. The first surface314afaces the longitudinal direction Y; and the second surface314bextends both in the longitudinal direction Y and in the lateral direction X.

As illustrated by300B inFIG. 6B, the first surface313aof the first engaging portion313is in surface contact with the first surface314aof the second engaging portion314in a state where the two-way push-pull chain300is contracted. At the same time, the second surface313bof the first engaging portion313is in surface contact with the second surface314bof the second engaging portion314. Here, the second surface313bof the first engaging portion313and the second surface314bof the second engaging portion314extend in a radial direction of the pin320. Accordingly, this configuration can regulate the lifting of the two-way push-pull chain300from the guide portion G and bending thereof. Also, as illustrated inFIGS. 6A and 6B, the first surface313aof the first engaging portion313and the first surface314aof the second engaging portion314are highly inclined with respect to a radius of the pin320. In this case, the first surfaces313aand314aare not perpendicular to a radius of the pin, which can regulate the bending of the two-way push-pull chain300.

Note that the first to third embodiments may be changed as follows.

In the first embodiment, the pin120is fixed to the first pin hole111, which is located outside the second pin hole112. However, the pin120may be fixed to the second pin hole112by preparing the first pin hole111as an elongated hole instead of by preparing the second pin hole112as an elongated hole.

In the first embodiment, the chain is prevented from being bent in any direction by engaging the first engaging portion113with the second engaging portion114. However, the first engaging portion113and the second engaging portion114may be of any shape as long as the bending of the chain can be regulated by engaging the first engaging portion113with the second engaging portion114.

In each of the above embodiments, the two-way push-pull chain may be made of any material. Also, the two-way push-pull chain may be constituted by any chain such as a roller chain, a bushing chain, or the like as long as the chain has link members.

In each of the above embodiments, a drive motor may be used as a sprocket driving source. Also, the two-way push-pull chain may be driven by a force obtained by manually rotating a rotary handle.