GB2066925A

GB2066925A - Universal joint lubrication

Info

Publication number: GB2066925A
Application number: GB8037081A
Authority: GB
Original assignee: Rockwell International Corp
Current assignee: Boeing North American Inc
Priority date: 1979-12-26
Filing date: 1980-11-19
Publication date: 1981-07-15
Also published as: JPS5697628A

Abstract

Improved lubrication of bearing cups in universal joints is provided. A universal joint has a cross, which includes a central portion and trunions extending outwardly therefrom. Each of the trunions has a substantially cylindrical cavity which is open at its outer end. The cross has passages extending from the central portion which communicates with each of the cavities. The passages and the cavities contain a grease like lubricant to provide for lubrication of the bearing cups. A lubricant agitator is located in each of the cavities. The agitator is composed of an element 24 which is denser than the lubricant and is capable of moving around the inside of the cavity. The agitator keeps the lubricant homogeneous while the cross rotates. <IMAGE>

Description

SPECIFICATION Universal joint lubrication BACKGROUND OF THE INVENTION Field ofthe invention The present invention relates to an improved lubrication system for a universal joint and, in particurar, to a lubrication agitator which keeps the lubricant homogeneous.

Description of the prior art Due to the normal bleeding and the centrifugal effect of a rotating universal joint on the lubricating grease, often times a residue consisting of the lubrication thickener is left in the U-joint cross ends blocking the lubrication passages. There has been a long felt need for improvements in the lubrication of universal joints. Such improvements are shown in U.S. Patents 3,901,049 issued in 1974 to Herscovici; 3,832,865 issued in 1974 to Lewis and 3,470,711 issued in 1969 to Kayser. While all of these patents seek to improve lubrication of the needle bearings on a cardan type universal joint, none of them addresses the need for a homogeneous lubricant U.S. Patent 2,018,286 issued in 1935 to Smith discloses a lubricant agitator for use in oscillating bearings.This lubricator is provided with a plurality of balls which meter the lubricant to an oscillating bearing. The plurality of balls is required to produce this effect and, while these balls do mix the lubricant, such a system would not be applicable to a universal joint. U.S. Patent 428,657 issued in 1980 to Verniaud also discloses a lubricator which meters lubricant into bearing journals. None of the two lubricant metering devices disclosed above would function in a high speed rotating universal joint. As described below, the inherent rotational characteristics of a cardan universal joint allow the use of a densely compounded agitator to provide a homogeneous lubricant.

Summary ofthe invention It is, therefore, an object of this invention to provide an improved universal joint.

It is a further object of this invention to provide a universal joint with improved lubrication for its needle bearings.

It is still a further object of this invention to provide a densely compounded agitator in the trunions of the universal joint cross to insure a homogeneous lubricant.

It is yet another object of this invention to provide a densely componded agitator which is able to take advantage of the non uniform accelerations inherent in a cardan type universal joint.

It is yet an additional object of this invention to provide an economical lubricant agitator in the form of a steel ball which may be easily installed in the cavity of a standard cardan type universal joint.

These and other objects of the invention are provided in a preferred embodiment thereof which includes the universal joint of the type having a cross having a central portion and trunions extending outwardly therefrom. Each ofthetrunions has a cavity open at the outer end thereof. The cross has passages extending from the central portion and communicating with each of the cavities. The passages and the cavities contain a lubricant such as grease. Each cavity also contains an agitator which is composed of an element denser than the lubricant and which is movable in the cavity to keep the lubricant homogeneous as the U-joint cross rotates.

These and other objects of the present invention will become apparent to those skilled in the art by reading the foliowing specification, reference being made to the accompanying drawings and the appended claims.

Brief description of the drawing The description herein makes reference to the sole drawing wherein Figure lisa partial sectional front view of a cross and bearing cups of a universal joint of the present invention.

Description of the preferred embodiment Referring to Figure 1,'there is shown a universal joint with a cross generally denoted as 10. The cross 10 has a central portion 12 and trunions 14. The trunions 14 extend outwardly from the central portion 12 of the cross 10. Each of the trunions 14 has a cavity 16 which is open at the outer end thereof. The cross 10 has passages 18 which extend from the central portion 12 and communicate with each of the cavities 16. The passages 18 and the cavities 16 contain a lubricant (not shown) which is used to lubricate needle bearings 20. The lubricant flows through passages 22 to lubricate the needle bearings 20. A seal 32 is used to retain the lubricant in the bearing area.

A supply passage 28 communicates with the four lubrication passages 18 and terminates in an external lubricant fitting 30 by means of which grease or other suitable lubricant can be supplied to the passages 18 periodically. Normally, the lubricant used in universal joints is a thick grease which becomes less viscos as the joint heats up during use.

The typical grease lubricant has a specific cavity of .8 and is readily available from any major supplier of oils and lubricants. During the operation of a cardan type universal joint, the lubricant is subject to centrifugal forces and bleeding through the various lubricant passages in the joint. These effects cause a residue consisting of the lubricant thickenerto separate from the lubricant upon cessation of operation. This residue is left in the U-joint cross ends in the area of passages 22 thereby blocking the flow of lubricant.

In order to prevent this blocking mechanism from occurring, densely compounded spherical agitators 24 are placed in the cavities 16 priorto assembling the bearing bushings 26 to the cross 10.

The densely compounded agitator 24 is movable in the cavity to keep the lubricant homogeneous upon rotation of the cross. As discussed below, the non uniform rotation of the cross insures that the agitator will move back and forth inside the cavity 16 rather than just staying at one point in the cavity.

In the preferred embodiment, the agitator is a steel ball with a diameter smaller than the diameter of the cavity 16 and larger than the diameter of the passages 18. While in the preferred embodiment the densely compounded material is steel, any material could be used as long as the density is greater than that of the lubricant employed for lubricating the bearing.

The homogeneous grease travels through the passages 22 from the cavities 16 to lubricate the needle bearings 20. The agitation caused by the agitator 24 helps force the lubricant through passages 22 to the needle bearings further enhancing the lubrication thereof.

Agitation of the lubricant in cavities 16 is caused by back and forth radial movement of the agitator 24 which results in the non uniform angular velocity of the cross in a cardan joint. The effect of this non uniform angular velocity causes the agitator to undergo rotation accelerations which cause the motion of the agitator during normal operation of a U-joint. It has long been known that a cardan type universal joint suffers a loss in efficiency with increasing angle between the input and output shafts. Thus, the ratio of the anguiar velocities of the driven and driving shafts increases as the angle between the shafts increases. This well known phenomenon causes a cyclic pulsation of the angular velocity of the driven shaft giving rise to accelerations which cause the agitator 24 to move in a radial direction back and forth across the cavity 16.

The cross and bearing of a universal joint shown in Figure 1 are connected to the driving and driven members (not shown) in the usual manner.

It can be seen that a universal joint incorporating the invention disclosed herein will have enhanced lubrication in that the lubricant will remain homogeneous and that the radial motion of the agitator 24 will help move the lubricant through passages 22 to the needle bearings 20.

Various modifications of the above described embodiment of the invention will be apparent to those skilled in the art and it is to be understood that such modifications can be made without departing from the scope of the invention if they are within the spirit and tensure of the accompanying claims.

Claims

1. A universal joint of the type having a cross including a central portion and trunions extending outwardly therefrom, each of said trunions having a cavity open at the outer end thereof, said having passages extending from said central portion and communicating with each of said cavities, said passages and said cavities containing a lubricant, the improvement comprising: an agitator located in each of said cavities, said agitator comprising an element denser than said lubricant and movable in said cavity to keep said lubricant homogeneous upon rotation of said cross.

2. A universal joint as set forth in claim 1, wherein said agitator is spherical in shape and is composed of material with a specific gravity greater than one.

3. A universal joint as set forth in claim 2, wherein said agitator is a steel ball.

4. A universal joint of the type having a cross including a central portion and four trunions, the trunions oriented in a plane with each trunion located on an axis normal to an adjacent axis, said cross having passages extending from said central portion to positions near the inner end of said trunions, a lubricant cavity in each of said trunions communicating with one of said passages, said passages and said cavities containing a lubricant, said universal joint comprising: an agitator located in each of said cavities, said agitator comprising an element denser than said lubricant and movable in said cavity to keep said lubricant homogeneous upon rotation of said cross.

5. A universal joint as set forth in claim 3, wherein said agitator is spherical in shape and is composed of material with a specific gravity greater than one.

6. A universal joint as set forth in claim 5, wherein said agitator is a steel ball.

7. A universal joint substantially as hereinbefore described with reference to and as shown in the accompanying drawing.