Patent Description:
The background information herein below relates to the present invention but is not necessarily prior art.

Chain tensioner devices facilitate eliminating chain slack arising in chain drives. Chain slack is a result of prolonged usage of chain drives. The links of the chain drives elongate in length with due course of usage time of the chain drives. The slack in the chain drives gives rise to unwanted vibrations and thus results in noisy operation of the chain drives. Conventional devices for eliminating chain slack and vibrations typically have a pre-tensioned spring that facilitates eliminating slack and prevent vibrations and noisy operation. However, the stiffness of the spring needs to be adjusted every time to eliminate such slack. This requires periodic servicing procedure. Moreover, the chain drives need to be lubricated frequently which again requires periodic maintenance scheduling. Additionally, adjusting chain drive slack requires human skill, as spring characteristics for a particular application is distinct.

<CIT> describes an hydraulic chain-tensioning device for tracklaying vehicles, in which the chain tension controlling wheel is carried by a reciprocable slide operable by a hydraulically operable cylinder-piston system in association with a fluid accumulator through the intervention of a pushrod interposed between said cylinder piston system and said slide while yieldable spring means surrounding said pushrod are interposed between said cylinder-piston means and said slide.

<CIT> descrbes an automatic voltage regulator for chain control of distribution shafts of internal combustion engines.

<CIT> describes a belt type power transmitting system.

<CIT> describes a chain transmission chain tensioning and lubricating device.

A need was therefore felt for an apparatus for eliminating slack and vibrations in a chain drive that would overcome the aforementioned issues.

Some of the objects of the present invention, which at least one embodiment herein satisfies, are as follows:
An object of the present invention is to provide an apparatus for eliminating slack and vibrations in a chain drive that eliminates periodic maintenance and servicing.

Another object of the present invention is to provide an apparatus for eliminating slack and vibrations in a chain drive that eliminates the requirement of skilled labour.

Still another object of the present invention is to provide an apparatus for eliminating slack and vibrations in a chain drive that delivers optimum chain drive performance.

Other objects and advantages of the present invention will be more apparent from the following description, which is not intended to limit the scope of the present invention.

The objects are solved by the apparatus as defined in the independent claim. Further embodiments are defined in the respective dependent claims. According to the invention, an apparatus for eliminating slack and vibrations of a chain of a chain drive is provided, the apparatus being configured to transfer the chain slack and vibrations through a sprocket wheel connected to the chain, the apparatus comprising:.

According to an example, the first piston is configured to be displaced inside the cylinder of the piston-cylinder arrangement and the second piston is configured to be displaced inside a cavity defined inside the first piston with the axis of the cavity being coaxial with the axis of the cylinder. A lubricating oil passage defined to pass through the first piston, the second piston and the cylinder of the piston cylinder arrangement. The apparatus facilitates reduction in vibrations, slack elimination and automatic lubrication of the chain drive.

In examples, a first end of the lubricating oil passage is configured to be in fluid communication with the chain drive and a second end of the lubricating oil passage is configured to be in fluid communication with a lubricating oil reservoir.

In examples, the grease port is provided on one end of the cylinder, the grease port is configured to be in fluid communication with the first piston.

The apparatus can be provided with a metering valve attached on one end of the lubricating oil passage.

The first piston can be configured to be displaced by pressure of grease flowing through the grease port.

The second piston can be configured to be displaced by the pressure of silicone oil contained in the cavity.

The apparatus for eliminating slack and vibrations in a chain drive of the present invention will now be described with the help of the accompanying drawing, in which:.

Embodiments, of the present invention, will now be described with reference to the accompanying drawing.

Embodiments are provided so as to thoroughly and fully convey the scope of the present invention to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present invention.

It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present invention.

In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.

The terminology used, in the present invention, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present invention.

As used in the present disclosure, the forms "a", "an" and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises", "comprising", "including" and "having" are open-ended transitional phrases and therefore specify the presence of stated features, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present invention is not to be construed as necessarily requiring their performance as described or illustrated.

When an element is referred to as being "mounted on", "engaged to", "connected to" or "coupled to" another element, it may be directly on, engaged, connected or coupled to the other element. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed elements.

Terms such as "inner", "outer", "beneath", "below", "lower", "above", "upper" and the like, may be used in the present invention to describe relationships between different elements as depicted from the figures.

<FIG> shows a chain drive <NUM>', in accordance with prior art, with an apparatus <NUM>' having a sprocket wheel <NUM>' for eliminating slack and tension in the chain <NUM>' configured to run between a drive sprocket <NUM>' and driven sprocket <NUM>'. The apparatus <NUM>' comprises a spring which needs to be adjusted periodically to change stiffness of the spring, thereby eliminating the slack in the chain <NUM>'.

Referring to <FIG>, an apparatus (<NUM>) for eliminating slack and vibrations in a chain drive <NUM> is shown in accordance with an embodiment of the present invention.

The apparatus <NUM> has a first end 100a and a second end 100b. The apparatus <NUM> comprises a piston cylinder arrangement with a first piston <NUM> configured to slide inside a cylinder <NUM> along the cylinder longitudinal axis A. The first piston <NUM> is configured to be acted upon by the pressure of a first fluid. In a preferred embodiment, the first fluid is grease. The second piston <NUM> is configured to slide inside a cavity <NUM> defined inside the first piston <NUM>. The second piston <NUM> is configured to be acted upon by the pressure of a second fluid. In a preferred embodiment, the second fluid is silicone oil. The cavity <NUM> is oriented along an axis that coincides with the longitudinal axis A of the cylinder <NUM>. The cavity <NUM> contains silicone oil and is configured to be in fluid communication with the second piston <NUM>. Thus, the first piston <NUM> and the second piston <NUM> are both configured to be displaced along the longitudinal axis A of the cylinder <NUM>. A lubricating oil passage <NUM> is provided into the apparatus <NUM>. The lubricating oil passage <NUM> is defined to pass through the first piston <NUM>, the second piston <NUM>, and the cylinder <NUM>. The lubricating oil passage <NUM> forms an L-shape. The first end 50a of the lubricating oil passage <NUM> terminates at an area where the first piston <NUM> and a sprocket wheel <NUM> are configured to interact. The second end 50b of the lubricating oil passage <NUM> terminates on the outside surface of the cylinder <NUM>. Since the first piston <NUM> and the cylinder <NUM> have relative motion configured with respect to each other, the section of the lubricating oil passage <NUM> on the cylinder <NUM> misaligns with the section of the lubricating oil passage <NUM> at an instant during operation of the apparatus <NUM>. This ensures an intermittent supply of lubricating oil to the sprocket wheel <NUM>. The second end 50b is configured to be coupled with a lubricating oil reservoir <NUM> where the lubricating oil to be supplied to the chain drive. A metering valve <NUM> is coupled on the second end 50b of the lubricating oil passage <NUM> which facilitates measuring the amount of the lubricating oil consumed from the lubricating oil reservoir <NUM>. A grease port <NUM> is provided on one end of the cylinder <NUM> which facilitates pressurized grease supply contained inside a grease dispenser <NUM>. A pressure sensor <NUM> is provided on the cylinder <NUM> to sense the pressure of grease inside the cylinder <NUM>. The first piston <NUM> is configured to be in fluid communication with the grease coming through the grease port <NUM>. To prevent leaking of the silicone oil contained inside the cavity <NUM>, seals are provided between the second piston <NUM> and the first piston <NUM>.

In another embodiment, the apparatus <NUM> is configured on a plurality of chain drives (<NUM>) simulataneously. This is achieved by installing the apparatus <NUM> in a centralized manner, thereby facilitating slack elimination and vibration damping as well as lubrication to a plurality of chain <NUM>.

The working of the apparatus will now be explained with the help of <FIG>. A chain drive <NUM> is shown in <FIG>. A drive sprocket <NUM> and a driven sprocket <NUM> is placed at a desired distance apart from each other. The drive sprocket <NUM> and the driven sprocket <NUM> are connected by a chain <NUM> for transmission of power. The apparatus <NUM> is assembled on the slack side of chain <NUM>. The slack in the chain <NUM> is removed by pressurizing the cylinder <NUM> with the grease from the grease port <NUM>. Thus the initial tension in the chain <NUM> is maintained at a desired level. The second piston <NUM> is forced towards the second end 100b of the apparatus <NUM>. Typically, a displacement of <NUM> is applied to the second piston <NUM> towards the second end 100b. This compresses the silicone oil inside the cavity <NUM> towards the second end 100b. Silicone oil is selected as the fluid inside the cavity <NUM> due to its excellent compressibility characteristics.

When the chain drive <NUM> starts working, thrust forces act on the sprocket wheel <NUM> connected to the second piston <NUM>, thereby pushing the second piston <NUM> from the first end 100a to the second end 100b. This results in the compression of the silicone oil inside the cylinder <NUM> between the first piston <NUM> and the second piston <NUM>. When the chain <NUM> attains constant speed after sustaining the initial accelerations and decelerations due to starting of the chain drive <NUM>, the thrust incident on the second piston <NUM> reduces. Then, the silicone oil exerts force on the second piston <NUM> from the second end 100b to the first end 100a, thereby pushing the chain <NUM> into a mean position over the drive sprocket <NUM> as well as the driven sprocket <NUM>. Thus vibrations are minimized with the help of the reciprocating second piston <NUM> inside the first piston <NUM>. <FIG> shows the instant at which the lubricating oil passage <NUM> is blocked, while <FIG> shows the instant at which the lubricating oil passage <NUM> transfers the lubricating oil from the lubricating oil reservoir <NUM> to the sprocket wheel <NUM>. As shown in <FIG>, the section of the lubricating oil passage <NUM> on the cylinder <NUM> aligns with the section of the lubricating oil passage <NUM> on the second piston <NUM>. As the second piston <NUM> reciprocates inside the first piston <NUM>, intermittent supply of lubricating oil takes place, which eliminates the need of frequent manual intervention for the same purpose. As the sprocket wheel <NUM> is configured to be meshed with the chain <NUM> of the chain drive <NUM>, lubricating oil is transferred from the apparatus <NUM> to the chain <NUM> of the chain drive <NUM>.

With prolonged usage of the chain drive <NUM>, the slack in the chain <NUM> of the chain drive <NUM> increases and there arises a need for the first piston <NUM> to be displaced towards the first end 100a from the second end 100b. This is needed to eliminate slack and to ensure the desired tension in the chain <NUM> of the chain drive <NUM>. This is accomplished by pumping the grease through the grease port <NUM> towards the second end 100b of the apparatus <NUM>. The pressure sensor <NUM> constantly senses pressure of the grease present inside the cylinder <NUM> exerted on the first piston <NUM>. Slacking of the chain <NUM> causes reduction in pressure of the grease contained inside the cylinder <NUM>. The pressure sensor <NUM> signals a pump <NUM> mounted in the grease reservoir to increase pressure of the grease at a desired level inside the cylinder <NUM>. The desired pressure level of the grease inside the cylinder <NUM> is calibrated for the tension in the chain <NUM> of the chain drive <NUM>. Thus, slack in the chain <NUM> of the chain drive <NUM> is eliminated and optimum tension is achieved, thereby reducing unnecessary vibrations which are detrimental to the longevity of the chain drive <NUM>.

Claim 1:
An apparatus (<NUM>) for eliminating slack and vibrations of the chain (<NUM>) of a chain drive (<NUM>), the apparatus (<NUM>) being configured to transfer the chain slack and vibrations through a sprocket wheel (<NUM>) connected to the chain (<NUM>), the apparatus (<NUM>) comprising:
• a piston-cylinder arrangement;
• a first piston (<NUM>), a cylinder (<NUM>) in which said first piston (<NUM>) is configured to reciprocate, said cylinder (<NUM>) configured to be filled with a first fluid, a grease port (<NUM>) defined in said cylinder (<NUM>) for introducing and dispensing said first fluid into said cylinder (<NUM>) or therefrom, and a pump (<NUM>) in fluid communication with said grease port (<NUM>); characterized by a pressure sensor (<NUM>) fitted inside said cylinder (<NUM>) to sense pressure of said first fluid in said cylinder (<NUM>), said pressure sensor (<NUM>) configured to be in communication with said pump (<NUM>), said grease port (<NUM>) configured to enable operation of said pump (<NUM>) when said pressure sensor (<NUM>) senses a reduced pressure in said cylinder (<NUM>) in response to a slackening of the chain (<NUM>), and thereby reduction in pressure exerted by said first piston (<NUM>) on said first fluid inside said cylinder (<NUM>); the apparatus (<NUM>) further comprising:
• a second piston (<NUM>) configured to reciprocate in a cavity (<NUM>) defined inside said first piston (<NUM>), said second piston (<NUM>) connected to said sprocket wheel (<NUM>) at one end (100a), a second compressible fluid filled in said cavity (<NUM>), said second piston (<NUM>) arrangement configured such that the vibrations received by said second piston (<NUM>) are damped by said second compressible fluid.