Belt tensioner with increased bushing surface

Details Belt tensioner with increased bushing surface Belt tensioner with increased bushing surface

1999-08-13

2001-04-17

Bucci, David A. (Department: 3682)

Endless belt power transmission systems or components

Means for adjusting belt tension or for shifting belt,...

Guide roll mounted for movement of its axis along arcuate...

C474S101000, C474S117000, C474S133000

Reexamination Certificate

active

06217470

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a device for automatically applying tension to a drive belt used in conjunction with rotating accessories mounted on a vehicular engine. More particularly, the invention relates to the belt tensioner designed to have an increased bushing surface between stationary and displaceable parts of the device.
BACKGROUND OF THE INVENTION
It is known to utilize a tensioning device to effectively operate a variety of rotating accessories operatively connected with and driven by an engine. In order to maintain reliable and efficient operation of the accessories, the tension of the belt should be maintained at a level sufficient to prevent slipping of the belt over various pulleys upon which the belt is trained.
Consequences of the slippage of the belt can be undesirable. Particularly, slippage can be disastrous in case of the chains used to drive an engine's valve gear. The slipping of accessory drive belts used for the purpose of providing power to such engine accessories as a power steering pump, air conditioning compressor and many others, while not producing catastrophic results, still leads to its inefficient operation and is accompanied by undesirable squealing and chirping noises. Accordingly, the need for belt tensioning under such circumstances has been recognized for many years.
Typical in many respects of the known prior art, a belt tensioner shown in
FIG. 1
includes a stationary bracket
8
′ and a pivotal arm
5
′ functioning as a pulley support. The illustrated device is negatively affected by a few drawbacks. First of all, because the tensioning device is secured to the engine, the attaching structure lacks rigidity and as a result may have vibration characteristics which are far from being ideal. This, in turn, leads to unsatisfactory rigidity of the structure which negatively affect the tensioning of the belt.
The device shown in
FIG. 1
is particularly unsatisfactory because it has a very limited supporting surface between the arm and the bracket. As known in the art, facing surfaces of the stationary and displaceable elements of the tensioner are abutted by respective bearing surfaces. Thus, as can be seen from
FIG. 1
, a central axial bearing
12
′ contacting the arm
5
′ and the bracket
8
′ is practically a single wear surface which provides stiffness to the whole structure. As demonstrated by practical application of such tensioners, this structure is inadequate and results in a short life of the tensioner. It needs frequent maintenance and, therefore, is neither cost efficient nor practically durable.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a belt tensioner which has superior functional characteristics in terms of vibration.
It is another object of the invention to provide a belt tensioner which has a reliable and large contact surface capable of withstanding vibration.
Still another object of the present invention is to provide a belt tensioner having a plurality of bearings inserted between respective adjacent surfaces of the displaceable and stationary components of the belt tensioner.
The embodiment of the invention described herein is just an example of the inventive concept, and it is to be understood that the various features of the invention can be utilized in various combinations thereof to provide a belt tensioner for other systems as desired.
A belt tensioner according to the invention includes a stationary bracket rigidly mounted at the front of the engine. The bracket is cup-shaped and receives a lever arm which is mounted pivotally on the bracket and is spring-loaded to be tensioned in a belt-tensioning directions toward an endless belt. The bracket and lever arm are provided with a plurality of formations extending toward one another and spaced apart. Such juxtaposition defines a plurality of channels that are filled with at least one U-shaped bearing. The arm supports a pulley carrier that extends so that a fastening element attaching the bracket to the engine does not extend into a volume of the pulley carrier.
According to another embodiment, the channels formed between the stationary bracket and pivotal arm are filled with a pair of coaxial bushings.
Further, the invention provides a continuous surface of the lever arm terminating within a housing of the bracket and forming therewith a compartment, which receives a spring element. Respective surfaces of the components are separated by a spring bearing providing an additional support surface and serving as a guide for the spring element.


REFERENCES:
patent: 3924483 (1975-12-01), Walker et al.
patent: 4473362 (1984-09-01), Thomey et al.
patent: 4596538 (1986-06-01), Henderson
patent: 4696663 (1987-09-01), Thomey et al.
patent: 4725260 (1988-02-01), Komorowski et al.
patent: 4886484 (1989-12-01), Hanes
patent: 4938734 (1990-07-01), Green et al.
patent: 5131889 (1992-07-01), Meckstroth et al.
patent: 5545095 (1996-08-01), Henderson

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