Machine element or mechanism – Elements – Gear casings
Reexamination Certificate
2001-12-21
2003-06-10
Luong, Vinh T. (Department: 3682)
Machine element or mechanism
Elements
Gear casings
C060S487000, C060S489000, C060S491000, C180S006280
Reexamination Certificate
active
06575055
ABSTRACT:
BACKGROUND OF THE INVENTION
The disclosure of U.S. patent application Ser. No. 08/899,903 is incorporated herein by reference.
This invention relates generally to transmission and transaxle casings and, more particularly, relates to a fastener less, hydrostatic transmission or transaxle casing.
Transmission and transaxle casings of conventional construction are well known in the art. An example of one such transaxle casing is disclosed in U.S. Pat. No. 5,330,394 to Hauser et al. entitled “Rider Transaxle Having Improved Casing Design.” As illustrated by the '394 patent, known transmission and transaxle casings are typically formed by fastening two or more casing components together. More specifically, the casing components are formed with complimentary fastener accepting apertures through which a fastener, such as a bolt or the like, is passed to secure the components in mating engagement.
A further transaxle casing may be seen in U.S. Pat. No. 5,613,409 to Hauser entitled “Axle Driving Apparatus Having Improved Casing Design.” In particular, the '409 patent discloses an integrated hydrostatic transaxle (“IHT”) having a casing component to which is fastened a cap plate and an axle cap. As with the '394 patent, the casing components are all formed from a metal, such as aluminum, and provided with fastener accepting apertures through which fasteners are passed to secure the casing components in mating engagement.
While the transmission and transaxle casings found in the prior art work well for their intended purpose, such casings are known to have several disadvantages. In particular, forming the casing components with fastener accepting apertures is seen to be a costly process which requires relatively tight manufacturing tolerances, for example, to ensure the proper alignment of the apertures. Furthermore, the process of using fasteners to couple the various casing components is seen to slow and complicate the assembly process resulting in an undesirable increase in the overall cost of manufacture. Additionally, deflection of the casing components of hydrostatic transmissions and transaxles along the junction surfaces will occur in those areas not directly secured with fasteners (those areas between the fasteners) which may result in the leakage of hydraulic fluid therefrom. Such fluid leakage resulting from the noted intermittent attachment between the casing components may impair the operability of the device and is cosmetically and ecologically unappealing.
From the foregoing, it is seen that a need exists for an improved transmission and transaxle casing.
SUMMARY OF THE INVENTION
The present invention resides in a fastener less casing adapted for use in carrying a transmission or transaxle assembly, in particular, a hydrostatic transmission or a hydrostatic transaxle. The casing includes a main casing section having an opening and a cap disposed over the opening wherein the cap and the main casing section are adapted for snap fit engagement. In a first embodiment, the main casing section has a first lip formed around the perimeter of the opening and the cap has a second lip wherein the first and second lips are adapted for snap fit engagement. In a second embodiment, the main casing section has a lip formed around the perimeter of the opening and the cap comprises a plurality of clips wherein the lip and the plurality of clips are adapted for snap fit engagement.
Accordingly, it is an object of the present invention to provide an improved transaxle or transmission casing which overcomes the deficiencies above-noted. More specifically, it is an object of the present invention to provide an improved casing which may be manufactured and assembled at a relative cost savings. It is a further object of the present invention to provide a relatively less costly means for increasing the number of points of attachment between the casing components for the purpose of minimizing the leakage problem resulting from component deflection. It is still a further object of the present invention to provide an embodiment which utilizes “continuous” attachment between the casing components for the purpose of eliminating the leakage problem resulting from component deflection. It is yet a further object of the present invention to provide an improved casing which is relatively lighter than currently known casings. It is a more specific object of the present invention to provide an improved casing which does not require the use of fasteners, i.e., a “fastener less casing”.
A better understanding of the objects, advantages, features, properties and relationships of the invention will be obtained from the following detailed description and accompanying drawings which set forth illustrative embodiments and which are indicative of the various ways in which the principles of the invention may be employed.
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Altheimer & Gray
Hydro-Gear Limited Partnership
Luong Vinh T.
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