JPH0125807Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a return type tensioner that applies appropriate tension to chains, belts, etc.

Prior Art As disclosed in Japanese Patent Publication No. 58-24666, a screw shaft movable in the axial direction and prevented from rotating is screwed into a cylinder to which a torque is applied to one end by a spring. Tensioners that convert torque into axial propulsion force of a screw shaft and apply it to the back surface of a chain or the like are conventionally known. In this conventional structure, the screw shaft can advance steplessly but cannot retreat, so there is a drawback that when the tension becomes excessive due to vibration of the chain, it adversely affects the transmission parts.

Problems to be solved by the invention This invention has the advantage of stepless advancement using a screw shaft in the conventional technology, and also allows for retraction by an amount corresponding to the excessive tension of the chain, etc., compared to the conventional technology. The purpose of this invention is to propose a tensioner that eliminates the above drawbacks.

Means for Solving the Problems This proposal includes a spring holder which is prevented from moving in the axial direction but is guided and supported to rotate freely, and to which torque is applied by a spring, and a cylinder whose one end is coaxially fixed to the spring holder. a coil spring; and a sleeve which is prevented from rotating and has a pawl that is slidably guided and supported coaxially with the cylindrical coil spring and is threadedly engaged with an intermediate portion of the cylindrical coil spring, and is given a protruding force to the outside of the main body by the torque. is provided, and the back surface of the chain or belt is pressed by the protruding force.

Function: When the chain or the like extends and its tension decreases, the sleeve protrudes steplessly in response to this, maintaining the tension at a predetermined value. However, if the chain etc. vibrates due to high speed, the tension will also fluctuate, and the axial length of the cylindrical coil spring from the threaded part of the pawl to the fixed end with the spring holder will be elastic. changes to absorb excess tension. Therefore, tension fluctuations in the chain, etc. are almost eliminated.

Example A large diameter hole 2 and a small diameter hole 3 are coaxially formed in the main body 1 installed on one side of the chain C, and a small diameter hole 5 coaxial with the large diameter part 2 is bored in the cover 4 fixed to the main body 1. Set up The spring holder 6 inserted into the large diameter hole 2 has a flange 8 that loosely fits into the large diameter hole 2 and comes into contact with the end surface 7 thereof.
, a cylindrical portion 9 that fits loosely into the small diameter hole 3, and a medium diameter portion 10 extending from the flange 8 to the inner surface of the cover 4;
The spring holder 6 is integrally formed with a small diameter portion 11 that loosely fits into the small diameter hole 5, and when the cover 4 is attached, the spring holder 6 is prevented from moving in the axial direction and is guided and supported to freely rotate. A torsion spring 12 surrounding a medium diameter part 10 is provided in the large diameter hole 2, one end of which is attached to the main body 1 and the other end to the flange 8, and the small diameter part 11 is rotated from the outside to wind the spring 12. Spring holder 6
After applying torque to the cover 4 and the narrow diameter part 11
A pin 13 is inserted into the hole of the spring holder 6 to temporarily prevent rotation of the spring holder 6.

One end of a cylindrical coil spring 14 coaxially protruding into the small diameter hole 3 is fixed in the cylindrical portion 9, and a sleeve 15 having a hollow portion into which the cylindrical coil spring 14 enters the small diameter hole 3 is freely guided and supported. A pin 17 attached to the main body 1 is fitted into an axial groove 16 provided on the outer surface to prevent rotation, and a ring 18 fixed to the inner end of the sleeve 15 has a claw that engages with the middle part of the cylindrical coil spring 14. 19 and 20 are formed to act as a nut when the cylindrical coil spring 14 is considered as a screw shaft.

The outer end of the sleeve 15 protruding from the main body 1 is brought into contact with a shoe S whose one end is pivotally connected to a fixed member with a pin P via an elastic material E, and the shoe S is attached to a chain P.
When the pin 13 is pulled out, the spring holder 6 is rotated by the torsion spring 12 to rotate the cylindrical coil spring 14 and apply an outward protrusion force to the sleeve 15 via the claws 19 and 20. This applies a predetermined tension to the chain P. As the chain P extends and the tension decreases, the sleeve 15 protrudes accordingly, keeping the tension approximately constant.

If the load on the chain P increases or the tension increases due to vibration of the chain P, the reaction force applied to the sleeve 15 causes the pawls 19 and 20 to compress the cylindrical coil spring 14 and allow the sleeve 15 to retreat. The increase in tension is relieved.

Effects of the invention This invention has the above-mentioned configuration. When the tension of the chain or belt decreases, the sleeve protrudes to compensate for the decrease in tension in a stepless manner, and when the tension increases, the sleeve elastically retreats to increase the tension. This has the effect of not only preventing wear and noise of the chain and other transmission parts, but also maintaining appropriate tension and improving power transmission efficiency.

[Brief explanation of the drawing]

The drawing is a longitudinal sectional view of one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Main body, 6...Spring holder, 12...Spring, 14...Cylindrical coil spring, 15...Sleeve, 19, 20...Claw.

Claims (1)

[Scope of utility model registration request] The main body includes a spring holder which is rotatably guided and supported while being prevented from moving in the axial direction and to which torque is applied by a spring, a cylindrical coil spring whose one end is coaxially fixed to the spring holder, and a cylindrical coil spring which is prevented from rotating. and a sleeve that is coaxially and freely guided and supported, has a claw that engages with the middle part of the cylindrical coil spring, and is given a protruding force to the outside of the main body by the torque, and the protruding force causes the chain or belt to A tensioner that presses against the back.