Fabrication of fluid coupling

Details Fabrication of fluid coupling Fabrication of fluid coupling

1999-06-08

2001-01-16

Hughes, S. Thomas (Department: 3726)

Metal working

Method of mechanical manufacture

Impeller making

C192S058410, C192S113210, C192S058681

Reexamination Certificate

active

06173492

ABSTRACT:

TECHNICAL FIELD
The subject invention relates to a fluid coupling of the type for transmitting rotary motion between an internal combustion engine and the cooling fan which moves cooling air through the radiator for cooling the cooling fluid of the engine.
BACKGROUND OF THE INVENTION
Due to the high shear forces in such fluid couplings, significant amounts of heat is generated. In order to dissipate this heat, the housings of the fluid couplings are die cast with integral fins which act as heat sinks. The numerous and geometrically complex cooling fins cannot be manufactured economically with any process but die casting. However, die casting is an expensive process and often produces defective housings which leak. An example of such an assembly is shown in U.S. Pat. No. 5,277,289 to Dax. In addition to the heat dissipation, it is frequently desirous to maintain a narrow gap between the disc and side walls of the fluid coupling assembly as illustrated in U.S. Pat. No. 3,319,754 to Kokochak et al. Conventional clutches are die-cast and then machined to achieve the necessary tolerances. Considerable machining is needed because die-casting is an inaccurate process that typically generates parts that substantially deviate from the final desired result. An additional disadvantage of die-casting is the potential leaks in the clutch because of the porosity of the die-casting material. This porosity typically dictates the need to use an additional step in the manufacturing process called impregnation, whereby the die-cast and machined parts are immersed in a high temperature resin batch under pressure in order to seal the leaks in the material. Impregnation is expensive and slow. Despite its disadvantages and cost, the die-casting process is used in conventional clutches because of the need to provide cooling fins on the outside of the body of the clutch. Viscous clutches generate substantial heat internally because of the shear stress in the oil. This heat has to be transferred to the air surrounding the clutch, and this is possibly only by providing a sufficiently large heat exchange area, which is achieved with the cooling fins. Cooling fins cannot be machined because the amount of machining would make the clutch prohibitively expensive. The only possible solution so far has been to use die-cast those fins. That resolves the problem of the cooling fins, but it creates all the other problems mentioned above.
SUMMARY OF THE INVENTION AND ADVANTAGES
A fluid coupling assembly comprises a housing having spaced side walls extending transversely to an axis and defining a fluid chamber. A shaft extends through and is rotatably supported by one of the side walls and a disc is supported by the shaft in the chamber in spaced relationship to the side walls. Cooling fins are included for cooling the fluid chamber. The assembly is characterized by a cooling sub-assembly comprising a support member supporting the cooling fins independently of the housing with the cooling sub-assembly secured to the housing.
The invention also includes a method of assembling such an assembly including the steps of fabricating a cooling sub-assembly by connecting cooling fins and a support member, and securing the cooling sub-assembly to the housing.
The new method, which is the object of this invention, consists basically of making the clutch without fins (which eliminates the need to use die-casting) and then, in a second operation, mounting a set of cooling fins made separately onto the clutch. This separately made set of cooling fins can be made using different processes (such as aluminum extrusion, stamping, etc.)
Accordingly, the fluid couplings of the subject invention may be fabricated from a relatively inexpensive stamping, which alone do not have sufficient mass to inherently dissipate heat, but which are combined with separately fabricated cooling sub-assemblies. The fabrication process may be controlled to prevent leaks and a wide variety of components may be combined in various combinations to provide a wide variety of fluid coupling assemblies.


REFERENCES:
patent: 3007560 (1961-11-01), Weir
patent: 4899860 (1990-02-01), Diederich
patent: 5111923 (1992-05-01), Kennedy
patent: 5404977 (1995-04-01), Martin et al.
patent: 5484045 (1996-01-01), Kikuchi et al.
patent: 5601170 (1997-02-01), Martin et al.

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