Fluid sprinkling – spraying – and diffusing – Mobile distributor
Reexamination Certificate
1998-10-30
2001-05-29
Douglas, Lisa Ann (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Mobile distributor
C239S728000, C239S741000, C074S425000, C074S60600R
Reexamination Certificate
active
06237863
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the field of gearboxes, and more particularly gearboxes in which a worm gear engages a bull gear.
BACKGROUND OF THE INVENTION
Worm wheel gearboxes are well known in the art. Such gearboxes are especially useful where low speed and high torque is desirable. Within these gearboxes, a worm gear engages a bull gear. Often, the worm gear is disposed on an input or drive shaft and the bull gear is linked to an output shaft. These worm wheel gearboxes are commonly used, for example, in agricultural automatic irrigation systems and potato pilers.
Large scale agricultural automatic irrigation systems typically comprise a system of sprinkler heads disposed on a truss or frame network. The trusses are linked together, enabling such irrigation systems to stretch to lengths of a thousand yards or more. The ground supports of the trusses are each disposed on a wheel or pair of wheels so that the entire irrigation system can be moved across a field. It is common for such irrigation systems to rotate about a center point, resulting in a substantially circular irrigating footprint. However, such irrigation systems may also be adapted to move in a straight line across rectangular fields.
Each wheel or pair of wheels supporting and transporting the irrigation system is driven by a dedicated motor. The motor drives a shaft which acts as the input shaft to a worm wheel gearbox. A worm gear disposed on the input shaft is engaged with a bull gear within such a gearbox. The bull gear is linked to an output shaft. The output shaft has an output flange which connects to the driven wheel. Rotation of the input shaft is thus transmitted via the gearbox to the output shaft, driving the wheels of the irrigation system. A typical automatic irrigation watering system has a number of such support wheels and each wheel or pair of wheels typically is driven by a dedicated motor and worm wheel gearbox as described. Worm wheel gearboxes are especially advantageous in this environment because once the drive motor stops, the worm and bull gear combination will allow very little backlash or coasting. Thus, the irrigation system will remain in its position even if it is on a hill.
The farm environment tends to be wet, muddy, silty and dusty. Thus, these gearboxes are sealed to prevent contamination of the gearbox contents.
As discussed above, worm wheel gearboxes are also commonly used in potato pilers. A potato piler comprises a conveyor disposed on a wheeled frame. To enable even piling of potatoes, the conveyor must be moved short, precise distances during operation. Potato pilers thus typically comprise a motor which rotatably drives a shaft and a worm wheel gearbox that transmits the shaft rotation to drive the wheels of the potato piler. This enables the potato piler to be moved short, precise distances when piling potatoes.
The need often arises to tow the units described above. For example, some farmers, in order to reduce costs, will use one irrigation system for a number of fields. Thus, it is necessary to tow the entire irrigation system from one field to another. Similarly, once a warehouse has been filled with potatoes, the potato piler must be transported to another warehouse. Thus, there is a need to tow the potato piler.
Worm wheel gearboxes are not adapted for easy towing. The gear ratios are best adapted for high-torque, low-speed situations. Accordingly, there is a need for a worm wheel gearbox that can be made to freewheel in order to ease towing.
The industry's standard solution to this towing problem is to attach a freewheeling hub and flange onto the output shaft of the worm wheel gearbox. This freewheeling flange is then connected to the driven unit's wheel. When the unit is being towed, this freewheeling flange allows the wheels to spin free.
To engage the wheel with the gearbox, a pin is pushed through aligned holes in both the output flange and the freewheeling flange so that the freewheeling flange and the wheel, which is attached thereto, are turned with the output flange. This approach has many limitations. First, the extra parts make this towable gearbox more expensive to manufacture than a non-towable gearbox. Also, it requires at least one loose part (pin) which can be lost. This approach also exerts the entire driving force of the motor and gearbox on the pin, resulting over time in pin failures. Maintenance costs are high, as is downtime and the risk of losing crops due to missed irrigation.
Another approach to solving the towing problem uses locking hubs similar to those used in four-wheel drive vehicles. However, this construction has proven too complex and expensive to be practical in this application.
SUMMARY OF THE INVENTION
Thus, there is a need in the art for an affordable, sealed, disengagable worm wheel gearbox which is adapted for high-torque, low-speed operation and can be operated in muddy, silty or wet environments without extensive maintenance.
The present invention satisfies this need in the art. A preferred embodiment of the present invention comprises a sealed worm wheel gearbox which enables full engagement and disengagement of the worm gear and bull gear.
The worm wheel gearbox comprises a gearbox housing having a pair of eccentric shaft supports rotatably mounted within the housing at opposing ends. These eccentric shaft supports each have a hole adapted to receive the driveshaft. The axis of rotation of the drive shaft when fit into the hole is offset from the axis of rotation of the eccentric shaft supports. Washers, O-rings and oil seals ensure that the gearbox is sealed, preventing gear oil from within the gearbox from leaking out of the gearbox and silt, mud and dust from the surrounding environment from entering the gearbox. Each eccentric shaft support further comprises a plurality of threaded bosses. These bosses receive fasteners which are used to attach a handle onto the eccentric shaft supports. Actuation of the handle causes the eccentric shaft supports to rotate.
Since the driveshaft is mounted along an axis which is offset from that of the eccentric shaft supports, rotation of the eccentric shaft supports results in linear movement of the driveshaft and the attached worm gear along a radius of curvature. The offset distance and angle of rotation of the eccentric shaft supports are configured so that the worm gear travels enough linear distance to completely disengage the teeth of the bull gear. Thus, by actuating the handle, the worm gear can be moved into and out of engagement with the bull gear. When the worm and bull gears are engaged, rotation of the driveshaft is transmitted to the output shaft via the gearbox. When the gears are disengaged, there is no rotation transmission.
End plates are attached onto opposing sides of the main body of the gearbox. Each end plate has a substantially circular hole which allows the eccentric shaft supports to extend therethrough. Each hole has a pair of ridges extending thereinto. When the eccentric shaft support is rotated, the threaded bosses contact a ridge and further rotation is prevented. A first ridge stops rotation in a first direction so that the worm gear does not become engaged too tightly with the bull gear. The other ridge stops rotation in a second direction in order to establish a stop point once the worm gear is disengaged from the bull gear.
A dust cap is provided to further discourage intrusion of matter such as dust, mud and silt into the seals of the eccentric shaft support or driveshaft. The dust cap is generally circular in shape and has an outer ridge that fits into a canal formed in the end cap. The dust cap is further adapted to surround and aid sealing of the driveshaft.
These and other objects, advantages and features of the present invention will be more fully understood and appreciated by reference to the written specification, the drawings and the claims.
REFERENCES:
patent: 2568937 (1951-09-01), Stueland
patent: 2646213 (1953-07-01), Martin
patent: 2747423 (1956-05-01), Sanders
patent: 2834223 (1958-05-01), Strnad
pate
Douglas Lisa Ann
Knobbe Martens & Olson Bear LLP.
Smith William F.
LandOfFree
Disengageable worm wheel gearbox does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Disengageable worm wheel gearbox, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Disengageable worm wheel gearbox will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2514140