Patent Description:
Gearing is often used between a driver and a driven component to, for example, change the speed or torque of the driver to a speed or torque needed for the driven component. For example, gearing can be used between a motor and a fan to drive the fan at a different speed than the motor output.

Such gearing is incorporated into a gearbox and is often contained in a gear casing or housing. The internal components of a gearbox such as gears as bearings require lubrication to reduce friction, wear, and heat. The lubricating medium, typically gear oil, is often circulated within the housing by either forced or passive methods, such as an oil pump or splash lubrication, respectively.

In most gear systems or gearboxes, there are penetrations or openings in the housings through which input and/or output shafts traverse. In order to prevent oil from leaking through the rotating shaft penetrations, various sealing mechanisms, such as radial lip seals, mechanical seals or non-contacting bearing isolators are used at the penetration. However, radial lip seals and mechanical seals require direct contact with the rotating shaft, resulting in a wear item that often leaks and requires frequent replacement. While non-contacting bearing isolators do not wear, they often leak when used in splash lubrication applications. This is especially true when the gear casing is oriented such that a shaft utilizing a non-contact bearing isolator is oriented in a horizonal plane.

One way to address oil leakage issues with non-contacting bearing isolator is to contain or "catch" any oil that leaks from the shaft penetration. This can result in, among other things, environmental contamination, waste of lubricant, and catastrophic failure from loss of oil. Another way in which to address oil leakage is to use external systems, for example, tubing, to collect the oil and redirect it to an auxiliary or main oil reservoir. <CIT> discloses a gear box comprising a box body, an input shaft, an input bevel gear, an output bevel gear and an output shaft, wherein part of the box is provided with a forced lubrication oil inlet and an oil return opening.

Accordingly, there is a need for a system to prevent oil from leaking through rotating shaft penetrations in gear casings that utilize non-contacting bearing isolators. Desirably, such a system is a passive system. More desirably still, such a system reduces contamination and waste, diverting the lubricating oil back into the gearbox.

According to the present invention, there is provided a gearbox as defined in claim <NUM>. The gear box includes a main housing carrying an input shaft and an output shaft. A carrier generally serves as secondary housing that supports a shaft assembly and is mounted to the main housing via, for example, a bolted connection. The carrier is mounted to the main housing and has a bore through which the input or output shaft extends. An isolator plate is mounted to the carrier and has a bore aligned with the carrier bore through which the input or output shaft extends. An isolator is mounted to the isolator plate and has a bore aligned with the isolator plate bore, through which the input or output shaft extends. The gearbox can include intermediate stages of gearing that do not require external penetrations.

The carrier includes an oil collection well spaced from the shaft bore and an oil return channel in fluid communication with the oil collection well and extending through the carrier to the main housing.

The isolator plate includes an interior surface and an oil passage formed therein extends from the interior surface to the oil collection well, and is in fluid communication with the main housing via the oil collection well and the oil return channel. Fluid at the interior surface of the isolation dam is drawn into the main housing via the primary oil passage, the oil collection well and the oil return channel.

In an embodiment, the oil passage is a radially extending passage formed in the isolator plate. The isolator plate can include a projection such that the oil passage extends along the projection. In such an embodiment, the projection can align with the oil collection well of the carrier.

In an embodiment, the carrier includes a projection containing the oil collection well, which is aligned with the isolator plate projection, providing continuity with both isolator plate oil passages. In another embodiment, the oil return channel in the carrier is spaced from a bottom of the oil collection well. In further embodiments, the oil return channel can be oriented parallel to or askew the bore. Further advantageous embodiments of the invention are laid down in the dependent claims.

Further understanding of the present invention can be obtained by reference to the following detailed description in conjunction with the associated drawings, which are described briefly below.

Various embodiments of a gearbox according to the invention are disclosed and are not limited by the figures of the accompanying drawings, in which like references may indicate similar elements and in which:.

While the present invention is susceptible of embodiments in various forms, there is shown in the drawings and will hereinafter be described a presently preferred embodiment with the understanding that the present disclosure is to be considered an exemplification and is not intended to limit the disclosure to the specific embodiment illustrated.

A novel apparatus or system is disclosed to prevent or reduce oil leakage from a gearbox <NUM> by diverting the oil within the gearbox <NUM> from areas of the main housing <NUM> or secondary housing <NUM> that include penetrations, back into the main housing reservoir. <FIG> illustrate one example of a gear casing <NUM> having a system <NUM> to prevent or reduce oil leakage. For purposes of the present disclosure, the term gearbox <NUM> refers to the entire assembly including the main casing or housing <NUM>, secondary housing or carrier <NUM> input and output shafts <NUM>, <NUM>, respectively, all internal components, such as gears <NUM> and bearings <NUM> within the casing <NUM>. The terms gear casing, gear housing, casing and housing are used interchangeably, and refer to the enclosure in which the gears <NUM> and other power transfer components are contained.

Gears <NUM> and bearings <NUM> are contained in the housing <NUM> or secondary housing <NUM>, portions of which are illustrated in <FIG> and <FIG>. An input shaft <NUM> is coupled to a motor (not shown) and a driven component such as a fan (not shown) is mounted or coupled to the output shaft <NUM>.

The casing <NUM> has a secondary housing or horizontal carrier <NUM>, isolator plate <NUM> and isolator <NUM> mounted to the casing <NUM>. The carrier <NUM>, isolator plate <NUM> and isolator <NUM> provide the penetration 14a through which the input shaft <NUM> exits the casing <NUM>. The horizontal carrier <NUM> is mounted to the casing <NUM>, the isolator plate <NUM> is mounted to the carrier <NUM> and the isolator <NUM> is mounted in an opening 32b in the isolator plate <NUM>, as illustrated in <FIG> and <FIG>. The isolator <NUM> serves as a seal apparatus for the input shaft <NUM>. The penetrations or bores 32a, 32b, 32c, respectively in the carrier <NUM>, isolator plate <NUM> and isolator <NUM> are all concentric for passage of the shaft <NUM>.

It will be appreciated that the gearbox <NUM> contains a media, such as oil, that serves as a lubricant for the gears <NUM> and bearings <NUM>. The oil reduces friction and wear on the loaded rotating components such as the gears <NUM> and bearings <NUM>, while also providing a cooling medium for the components. The lubricant, for example, oil, can however leak from the main housing <NUM> or secondary housing <NUM> at the casing penetrations 14a, 14b. For example, oil can leak from the interface of the input shaft <NUM> and the isolator <NUM> or at the isolator/rotor interface. Oil leakage can result in damage to the gearbox <NUM>, or unwanted contamination of the surrounding area.

To contain the oil in the main housing <NUM> and secondary housing <NUM> and to reduce leakage, an embodiment of the present gear casing oil diverter system <NUM> uses a modified carrier <NUM> and isolator plate <NUM>, as best seen in <FIG>. Referring first to <FIG>, the carrier <NUM> includes a body <NUM> that is generally circular in shape and has a forward or outboard end <NUM> and a rear or inboard end <NUM>. The rear or inboard end <NUM> is mated with the main housing casing <NUM> and the isolator plate <NUM> is mounted to the forward or outboard end <NUM>. An integral oil collection well <NUM> is formed within the lower radial projection <NUM>. An oil return channel <NUM> extends from the oil collection well <NUM> longitudinally through the carrier <NUM> to provide fluid communication with the main housing <NUM> of the gearbox <NUM>.

Referring to <FIG>, <FIG> and <FIG>, the isolator plate <NUM> is generally circular in shape (to mate with the carrier forward end <NUM>) and includes a radial projection <NUM> such that the isolator plate <NUM> mounts to and mates with the carrier forward end <NUM>. The isolator plate projection <NUM> overlies the carrier projection <NUM> and oil collection well <NUM>. The isolator plate <NUM> has a thickness t<NUM> that defines a concentric bore 32b. A section near the rearward end of the bore 32b has a reduced diameter, creating a lip <NUM> that serves as an isolation dam to limit the volume of oil allowed into the cavity <NUM> located immediately behind the isolator <NUM>.

An integral oil passage <NUM> is formed in the isolator plate <NUM>. In an embodiment, the oil passage <NUM> is formed as a channel that extends radially downward from the isolator plate bore 32b into the isolator plate projection <NUM>. The oil passage <NUM> turns rearwardly, toward the rearward end <NUM> of the isolator plate <NUM>, to an opening <NUM>. The opening <NUM> aligns with the oil collection well <NUM> located in the carrier projection <NUM>. In this manner, the isolator plate bore 32b is in fluid communication with the main reservoir of the main housing <NUM> via the oil passage <NUM> as it traverses through the isolator plate <NUM>, into the carrier oil collection well <NUM> and through the carrier oil return channel <NUM>. As best seen in <FIG>, the oil return channel <NUM> is at a height h<NUM> above that at which the oil passage <NUM> empties into the oil collection well <NUM>.

In an embodiment, the isolator plate <NUM> is secured to the carrier forward or outboard end <NUM> by a series of fasteners <NUM>. The isolator stator is mounted in the isolator plate <NUM> by an interference fit.

Referring again to <FIG>, oil is circulated in the gearbox <NUM> through one or more oil passages, such as passage <NUM>. With respect to the carrier <NUM>, oil flows into and around the bearings <NUM> and the shafts <NUM>, <NUM>. As such, oil will tend to leak at the penetration 14a of the shaft <NUM>, and more specifically at the interface <NUM> of the isolator stator and rotor.

As oil flows toward the isolator <NUM>, it is restricted from flowing beyond the isolator plate rearward end <NUM> by the isolation dam <NUM> of the plate <NUM>. However, given the fluid nature of oil and the splashing action within the gearbox <NUM>, oil may escape and flow over the isolation dam <NUM> and into the cavity <NUM> between the isolator <NUM> and isolator plate <NUM>.

In the present system, oil that the finds its way into the cavity <NUM> will not leak from the isolator stator/rotor interface <NUM>. Rather, the oil drains into the oil passage <NUM> and collects in the oil collection well <NUM>. As the oil fills the oil collection well <NUM>, it will reach the height or elevation of the oil return channel <NUM> in the carrier <NUM> and will drain toward the main housing <NUM>, as indicated by the arrow at <NUM>. In addition, the natural pumping action of the bearings <NUM> draws oil away from the oil return channel <NUM> and oil collection well <NUM> to greatly reduce or eliminate leakage at the shaft penetration and isolator stator/rotor interface <NUM>.

It will be appreciated that the presently disclosed system to prevent or reduce oil leakage from a gearbox <NUM> by diverting the oil within the casing <NUM> from areas of the casing that include penetrations, for example penetration <NUM>, is presented as an example only.

Claim 1:
A gearbox (<NUM>) comprising:
a main housing (<NUM>) carrying an input shaft (<NUM>) and an output shaft (<NUM>);
a carrier (<NUM>) mounted to the main housing (<NUM>), the carrier (<NUM>) having a bore (32a), wherein one of the input shaft (<NUM>) and the output shaft (<NUM>) extends through the bore (32a) in the carrier (<NUM>);
an isolator plate (<NUM>) mounted to the carrier (<NUM>) and having a bore (32b) aligned with the carrier bore (32a), wherein the one of the input shaft (<NUM>) and the output shaft (<NUM>) extends through the isolator plate bore (32b);
an isolator (<NUM>) mounted to the isolator plate (<NUM>) and having a bore (32c) aligned with the isolator plate bore (32b), wherein the one of the input shaft (<NUM>) and the output shaft (<NUM>) extends through the isolator bore (32c), wherein the isolator plate (<NUM>) includes an interior surface and an oil passage (<NUM>) formed therein;
characterized in that
the carrier (<NUM>) includes an oil collection well (<NUM>), spaced from the carrier bore (32a), and an oil return channel (<NUM>) in fluid communication with the oil collection well (<NUM>) and extending through the carrier (<NUM>) to the main housing (<NUM>); and in
that the passage (<NUM>) extends from the interior surface to the oil collection well (<NUM>), such that the interior surface is in fluid communication with the main housing (<NUM>) via the oil passage (<NUM>), the oil collection well (<NUM>) and the oil return channel (<NUM>); and in
that the oil passage (<NUM>), the oil collection well (<NUM>) and the oil return channel (<NUM>) are configured to draw fluid at the interior surface into the main housing.