Patent Description:
Portal gears are a way of configuring the drive system in a model vehicle such that the axle tube is above the center of the wheel hub and where there is a reduction gearbox in the hub. Portal gears improve performance of model vehicles by: <NUM>. increasing the ground clearance below the vehicle axles; and <NUM>. providing additional gear reductions for the overall axle assembly of the vehicle. The addition of gear reduction via the portal gear reduces the torque applied through the center drive shafts. By reducing this torque, the axle is less prone to twisting and preloading the suspension. Twisting of the axle due to low numerical axle ratio can have significant effect on driving performance.

Unfortunately, the implementation of portal gears is usually associated with concerns for additional costs. The conventional portal gear tends to have four gears - input, output, and two idlers. Accordingly, there is a need for a portal gear with a simplified design that provides the same performance increase while keeping cost low.

<CIT> discloses a portal gear box housing comprising an upper gear housed within the portal gear box; a lower portal gear housed within the portal gear box and in contact with the upper gear; at least one lower inner bearing mount and at least one lower outer bearing mount; a lower inner bearing mounted at the lower inner bearing mount; and a lower outer bearing mounted at the lower outer bearing mount.

According to the present invention there are provided a portal gear and a method as set forth in the appended independent claims.

The present invention provides a portal gear for model vehicles with a simplified two-gear design. The portal gear includes a drive shaft coupled to an input gear and a portal axle coupled to an output gear. In addition, the portal gear includes a housing configured to contain the input gear and the output gear.

Certain embodiments will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying drawings illustrate only the various implementations described herein and are not meant to limit the scope of various technologies described herein. The drawings are as follows:.

In the following discussion, numerous specific details are set forth to provide a thorough understanding of the present invention. However, those skilled in the art will appreciate that embodiments of the present invention may be practiced without such specific details. Additionally, for the most part, specific details, and the like have been omitted inasmuch as such details are not considered necessary to obtain a complete understanding of the present invention.

<FIG> and <FIG> generally illustrate a solid axle and a portal gear <NUM> for configuring the drive system of a model vehicle. The portal gear <NUM> transfers torque between a drive shaft <NUM> and a portal axle <NUM>. The portal gear <NUM> may improve the performance of the model vehicle by positioning the axle housing and differential centers above the wheel center, thereby increasing the ground clearance below the axles. In some embodiments, the portal axle <NUM> may transfer torque via the portal hex <NUM> to a model vehicle wheel (not shown).

The portal gear <NUM> comprises a gear reduction within an inner portal housing <NUM> and an outer portal housing <NUM> to increase the gear reduction of the overall axle assembly. The increased load reduction may allow for smaller gears and shafts in the drivetrain upstream of the portal gear reduction. In an embodiment, the ring and pinion for the differential and the center drive shafts may therefore be smaller due to the reduction in torque.

In an embodiment, the reduction of the portal gear <NUM> is simplified to a two-gear design by removing two idler gears typically found in portal gears for full size vehicles. The two-gear design of the portal gear <NUM> may decrease the overall cost of the portal gear <NUM> due to the removal of the additional idler gears and bearings and the resulting overall simplification. The removal of the idler gears may also decrease the size of the overall assembly of the portal gear <NUM> and save space within the model vehicle.

The smaller space required by the reduction of the portal gear <NUM> may create the opportunity to increase and maximize the numerical gear ratio of the reduction as allowed by the space saved from the removal of the idler gear. The increase in the numerical gear ratio directly impacts and lessens the "torque twist" of the suspension system.

Space is also saved in the portal gear <NUM> by consolidating the drive shaft <NUM> and a portal input gear <NUM> (See <FIG> for Example) into a single assembly. Typically, the drive shaft <NUM> and the portal input gear <NUM> require separate additional parts and space to assemble. In the embodiment of the portal gear <NUM> shown, the drive shaft <NUM> is integrated with the portal input gear <NUM> via a universal joint (u-joint) <NUM>. The u-joint <NUM> allows the drive shaft <NUM> to traverse in any direction and transmit rotary motion into the portal input gear <NUM>. The resulting smaller sized portal gear <NUM> may allow the overall portal gear <NUM> to be configured to falling substantially within the space of a typical model vehicle wheel.

In some embodiments, the portal gear <NUM> may be located on a front axle of the model vehicle, requiring upper and lower pivot points <NUM>, <NUM> and steering arm connection <NUM>. These features may be located on portal inner housing <NUM> or the outer portal housing <NUM>, depending upon application.

<FIG> shows a frontal view of the portal gear <NUM> with the portal axle <NUM> extending out of the outer portal housing <NUM>. The portal axle <NUM> may transfer power to a connected wheel of the model vehicle (not shown). In addition, <FIG> shows a frontal view of a portal hex <NUM>, used for transferring the torque of the portal axle <NUM> to a typical model vehicle wheel as stated previously.

Turning to <FIG> and <FIG>, the portal gear <NUM> is assembled by enclosing the portal input gear <NUM> and the portal output gear <NUM> between the inner portal housing <NUM> and the outer portal housing <NUM>. In <FIG>, the drive shaft <NUM> may be integrated with the portal input gear <NUM> by joining the ends of the drive shaft <NUM> and the portal input gear <NUM> with the universal joint <NUM>.

The portal output gear <NUM> is coupled to the portal axle <NUM> for example by inserting the portal axle <NUM> through a center opening <NUM> in the portal output gear <NUM>. The rotational and axial position of the portal axle <NUM> may be fixed in position relative to the portal output gear <NUM> by locking mechanism, in this case, through the use of a pin <NUM> inserted through a diametrically extending hole <NUM> through the portal axle <NUM>.

Opposing ends of the pin <NUM> may extend from the hole <NUM> into corresponding notches in the portal output gear <NUM> to prevent relative movement of the portal axle <NUM> axially away from the portal output gear <NUM> after the portal axle is inserted into the portal output gear <NUM>. The pin <NUM> may also ensure that rotation of the portal output gear <NUM> in turn rotates the portal axle <NUM>.

The position, size, and shape of the corresponding notches in the portal output gear <NUM> may be formed such that the opposing ends extending from the portal axle <NUM> may be fitted within the corresponding notches in the portal output gear <NUM> when the portal axle <NUM> is inserted through the center opening <NUM> of the portal output gear <NUM>.

The inner portal housing <NUM> may comprise a vehicle side <NUM>, a contacting side <NUM>, and a recessed gear cavity <NUM>. The recessed gear cavity <NUM> may open towards the contacting side <NUM> of the inner portal housing <NUM>. The recessed gear cavity <NUM> may be formed in the shape of a pair of adjacent abutting circular recesses to partially enclose the portal input gear <NUM> and the portal output gear <NUM> when the teeth of the two gears are mated.

The recessed gear cavity <NUM> may be sized to fit both the portal input gear <NUM> and the portal output gear <NUM> within the cavity <NUM>. The outer portal housing <NUM> may similarly comprise a contacting side <NUM>, a wheel side <NUM>, and a recessed gear cavity <NUM> substantially matching the shape and size of the recessed gear cavity <NUM> in the inner portal housing <NUM>.

The recessed gear cavity <NUM> of the outer portal housing <NUM> may partially enclose some portions of the portal input gear <NUM> and the portal output gear <NUM> not enclosed by the recessed gear cavity <NUM> of the inner portal housing <NUM>. The contacting sides <NUM>, <NUM> of the inner portal housing <NUM> and the outer portal housing <NUM> may be fitted together such that the recessed gear cavities <NUM>, <NUM> of completely enclose the portal input gear <NUM> and the portal output gear <NUM>.

As shown in <FIG>, the inner portal housing <NUM> may further comprise a through opening <NUM> in the recessed gear cavity <NUM> such that the portal input gear <NUM> may be inserted into the recessed gear cavity <NUM> from the vehicle side <NUM> of the inner portal housing <NUM>. The outer portal housing <NUM> may similarly comprise a through opening <NUM> in its recessed gear cavity <NUM> such that the portal axle <NUM> affixed to the portal output gear <NUM> may extend through the outer portal housing <NUM> from the contacting side <NUM> of the outer housing <NUM> to the wheel side <NUM>.

The portal gear <NUM> may be assembled by threading the portal input gear <NUM> through the opening <NUM> in the inner portal housing <NUM> and positioning the portal input gear <NUM> within the recessed gear cavity <NUM> of the inner portal housing <NUM>. The portal input gear <NUM> may comprise a flange <NUM> extending out of the outer perimeter surface of the portal input gear <NUM>.

The flange <NUM> may extend from a portion of the portal input gear <NUM> between the end of the portal input gear <NUM> connected to the drive shaft <NUM> and the teeth of the portal input gear <NUM>. The through opening <NUM> in the recessed gear cavity of the inner portal housing <NUM> may be sized such that only the teeth portion of the portal input gear <NUM> may fit through the opening <NUM>. The portal input gear <NUM> may be inserted through the inner portal housing <NUM> until the flange <NUM> contacts the vehicle side <NUM> of the inner portal housing <NUM>.

The portal output gear <NUM> is directly positioned adjacent the portal input gear <NUM> within the recessed gear cavity <NUM> such that the teeth of the portal input gear <NUM> and the portal output gear <NUM> are mated together. The portal output gear <NUM> may be positioned within the inner portal housing <NUM> with the portal axle <NUM> extending away from the contacting side <NUM> of the inner portal housing <NUM>. The recessed gear cavity <NUM> of the inner portal housing <NUM> may be sized such that is clearance for the portal input gear <NUM> and portal output gear <NUM> to rotate.

When both the portal input gear <NUM> and the portal output gear <NUM> are positioned within the recessed gear cavity <NUM> of the inner portal housing <NUM>, the contacting side <NUM> of the outer portal housing <NUM> may be subsequently secured against the contacting side <NUM> of the inner portal housing <NUM> to enclose the gears <NUM>, <NUM>.

The portal axle <NUM> extending from the portal output gear <NUM> may be threaded through the opening <NUM> in the recessed gear cavity <NUM> of the outer portal housing <NUM> when the outer portal housing <NUM> and the inner portal housing <NUM> are contacted together. The outer portal housing <NUM> may then be removably affixed to the inner portal housing <NUM> by six mechanical fasteners inserted from the vehicle side <NUM> inner portal housing <NUM> and two mechanical fasteners inserted from the wheel side <NUM> of the outer portal housing <NUM>. The mechanical fasteners securing the inner portal housing <NUM> and outer portal housing <NUM> together may include but is not limited to screws, nails, bolts, pins, clips, lugs and the like.

As shown in <FIG> and <FIG>, after the outer portal housing <NUM> and the inner portal housing <NUM> are engaged, a portal hex <NUM> may be positioned over a portion of the portal axle <NUM> extending out of the wheel side <NUM> of the outer portal housing <NUM>. The portal hex <NUM> may be positioned along the axle <NUM> until the portal hex <NUM> contacts a bearing 142A also positioned along the portal axle <NUM> between the portal output gear <NUM> and the outer portal housing <NUM>.

When secured against bearing 142A, the portal hex <NUM> prevent the portal axle <NUM> from moving axially moving towards the center of the model vehicle (i.e., to the left in <FIG>) or hitting the contacting side of the inner portal housing <NUM>. The portal hex <NUM> may be secured along the portal axle <NUM> by a pin <NUM> inserted through a first diametrically extending hole <NUM> through the portal hex <NUM> and a second diametrically extending hole <NUM> through the portal axle <NUM>. The pin <NUM> secures the contact between the portal hex <NUM> and the bearing 142A.

When the portal hex <NUM> is assembled at the end of the portal axle <NUM>, the portal hex <NUM> may also support the wheel and transmit torque to a model vehicle wheel (not shown). The portal hex <NUM> may be any other form of mechanical fasteners including but not limited to nuts, washer, locks, caps, and the like.

As also shown in <FIG>, inner bearing 142B is located in the recessed gear cavity <NUM> and supports another end of portal axle <NUM>. Correspondingly, bearing <NUM> located in the recessed gear cavity <NUM> and bearing <NUM> located against the inner portal housing support the portal input gear <NUM>.

<FIG> and <FIG> show the reduction between the portal input gear <NUM> and the portal output gear <NUM> within the inner portal housing <NUM> and the outer portal housing <NUM>. The additional reduction at the portal gear <NUM> increases the total numerical ratio of the axle assembly and reduces the torque applied through the drives shafts.

In the embodiment show, the portal gear ratio is <NUM>:<NUM> (<NUM>/<NUM>) and the ring and pinon of the axle is <NUM>:<NUM> (<NUM>/<NUM>). This makes the gear ratio of the axle assembly <NUM>:<NUM>. In other embodiments, the portal gear ratio is in the range between <NUM>:<NUM> to <NUM>:<NUM>. While in still other cases, the portal gear ratio is in the range between <NUM>:<NUM> to <NUM>:<NUM>. As shown in <FIG>, the teeth of the portal input gear <NUM> and the portal output gear <NUM> are mated to transfer torque between the drive shaft <NUM> and the portal axle <NUM>. Alternatively, gears of various sizes and ratio may be used for the portal depending on the overall size of the portal gear <NUM> and the availability of space within the inner portal and outer housing.

Claim 1:
A portal gear (<NUM>) for a drive system of a model vehicle comprising:
a drive shaft (<NUM>) coupled to an input gear (<NUM>) within a housing (<NUM>, <NUM>), the housing (<NUM>, <NUM>) containing the input gear (<NUM>) and an output gear (<NUM>), and the drive shaft (<NUM>) transferring a rotational torque from the input gear (<NUM>) to the output gear (<NUM>) via a gear reduction;
a portal axle (<NUM>) directly coupled to the output gear (<NUM>);
a bearing (142A) and an inner bearing ( 142B) rotatively supporting the output gear (<NUM>); and
a first and second input gear supports (<NUM>, <NUM>) rotatively supporting the input gear (<NUM>) in the housing (<NUM>, <NUM>),
characterised in that:
the drive shaft (<NUM>) is coupled to the input gear (<NUM>) via a universal joint (<NUM>), and a center of the universal joint (<NUM>) is within the first input gear support (<NUM>).