GB2218754A - A multi-component boot for a mechanical joint having improved sealing about the input shaft - Google Patents

Description

A MULTI-COMPONENT BOOT FOR A MECHANICAL JOINT HAVING IMPROVED SEALING

ABOUT THE INPUT SHAFT 1 2r) z_ 18 7 5 4 The invention relates to boots for power transmitting mechanical joints, especially for joints which are subject to articulation during operation. More particularly, this invention relates to a boot in which at least a portion of such a boot is of a semi-rigid character. Specifically this invention relates to a boot for a constant velocity joint of the type used in the front wheel drive mechanism of a front wheel drive automotive vehicle, in which the portion of the boot which surrounds the outer race of the mechanical joint is made up of concentric interleaved components, each of which is of semi-rigid character.

Constant velocity drive joints are widely used in the automotive industry as means to transmit power from the transaxle of a front 'wheel drive vehicle to the driven front wheels of the vehicle. One or more of such joints may be provided for each of the driven wheels. Such drive Joints must be sealed to maintain the necessary I.ubrication within the joint and to keep the joint free from dirt and other external contaminants.

The devices heretofore used to accomplish this sealing function, J -1, which are usually referred to as boots, are of a flexible construction, usually constructed of an elastomeric material and usually in a corrugated or pleated configuration. Such flexible construction, however derived, gives the boot the ability to accommodate articulation or angular movement of the normally axially aligned input and output shafts of a constant velocity joint.

Flexible boots for automotive constant velocity drive joints have been utilized quite extensively. However, these boots are quite expensive and due to their flexible nature they must be installed using manual operations. This precludes the use of cost saving mechanical assembly techniques that rely on precise dimensions of the parts being installed. Additionally, flexible boots Are made from an elastomeric material and are subject to tear and puncture due to road hazards and other forms of concentrated impacts. Further, the physical properties of elastomeric materials are known to degrade when exposed to low temperatures and high temperatures of the type which are encountered during the normal lifeof an automobile. Additionally, the interior volume of these corrugated or pleated boots must be filled with grease to properly lubricate the associated joint, and require rather large quantities of grease for that purpose. Furthermore, many of the elastomeric materials from which these boots are made are subject to degradation when exposed to grease, which limits the useful life of such flexible boots.

U.S. Patent application Serial No. 832,865 describes a multi-component boot for a mechanical joint made from semi-rigid materials. An inner member of this boot has a generally spherical configuration and sealingly engages, at its open end, the spherical surface of the mechanical joint's outer surface. The inner member also has an axially disposed input f.ill IF -4 k i 4 shaft clearance aperture. A hemispherically-shaped outer member is concentrically disposed over the inner member and with the inner member defines a spherically-shaped recess. An intermediate member sealingly engaging the input shaft of the mechanical joint has a spherically-shaped flange which is sealingly and movably received in the spherically-shaped recess formed by the inner and outer members. The problem encountered with this boot is the failure of the sea] between the input shaft and the intermediate member. This failure permitted the ingress of dirt and water to the mechanical joint and permitted the egress of the lubricant (grease) which results in premature failure of the mechanical joint. Various attempts to solve this problem using 11011 rings and similar type seals were unsuccessful or too costly. The instant invention is a protective boot having a novel shaft seal which makes a reliable seal between the input shaft of the mechanical joint and the intermediate member of the boot.

The invention is a boot for sealing a power transmitting mechani cal joint of the type having an input shaft, an output shaft, connection means for connecting the input shaft to the output so that the input shaft and output shaft can be articulated relative to each other. The connection means includes an outer race having a spherical external surface connected to one of the input and output shafts.

The boot includes a hemispherically shaped semi-rigid inner member having an open end sealingly engaging the external spherical surface of the outer race. The inner member also has a first clearance aperture at the eqd opposite the open end circumscribing the other of the input and output shafts. The boot further includes a hemispherically-shaped semi-rigid outer member concentric with the inner member and connected thereto. The outer 4 4..

member has a second clearance aperture concentric with the first clearance aperture of the inner member. At least one of the inner and outer members has a reduced thickness portion forming a spherically- shaped recess between_ the inner and the outer members. The spherically- shaped recess is open at the end thereof adjacent to the first and the second clearance apertures. A semi-rigid intermediate member having a spherically-shaped flange is sealingly and slidingly received in the spherically-shaped recess and a cylindrical boss sealingly circumscribes the other of the input and output shafts. The radius of the spherically- shaped flange at its open end is selected to permit a predetermined degree of articulation of the intermediate member in the spherically- shaped recess. The cylindrical boss of the intermediate member has an annular recess provided in its external surface. The boot also includes a shaft seal having an inwardly projecting annular dog received in the annular recess of the cylindrical boss to lock the shaft seal to the intermediate member. The shaft seal also has at least one inwardly extending rib sealingly engaging the external surface of the other of the input and output shafts.

it is accordingly possible to provide a boot for sealing a mechanical power transmission joint having improved sealing about the input shaft.

More particularly, it is possible to provide an improved boot for sealing a power transmission in a mechanical joint whose input and output members are subject to articulation relative to one another._ It is also'possible to provide a boot for sealing a constant velocity drive joint having a novel shaft seal sealing at least one component of the boot to the input shaft.

It is also possible to provide a boot having improved sealing for a constant velocity drive joint used to drive the front wheel of a front wheel drive automotive vehicle.

It is still further possible to provide a boot for sealing a constant velocity drive joint of a f ront wheel drive automotive vehicle in which the boot has multiple spherically-shaped components, each component being formed of a semi-rigid material. The components are disposed concentrically with each other, the inner of such concentric components sealingly engaging the spherical outer surface of a member of the joint in a way which permits articulation between the boot and the member of the joint having the spherical outer surface.

Preferred features and advantages of this invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings., in which:

Figure 1 is a side view, partially in section, of a constant velocity drive J6int having a preferred embodiment of a sealing boot according to the present invention; Figure 2 is an enlarged partial cross-section showing the details of the shaft seal; and Figure 3 is a fragmentary view, similar to Figure 1, illustrating an alternative embodiment of the shaft seal.

Figure 1 illustrates a constant velocity drive joint of the fixed or nonplunging type, indicated generally by reference numeral 11. The constant velocity drive joint 11 receives power at an input end 12 from an. input shaft 13 and transmits power to a driven member, not shown, by an output shaft 14 which extends from an output end 15 of the constant velocity drive joint 11. As is known in the prior art, power is transmitted from the t input shaft 13 to the output shaft 14 by means of a circumferential series of balls 16, typically six in number, which are contained in a cage 17. The balls 16 roll on a spherical surface 18 of an inner race 19, which is keyed or otherwise geared to the input shaft 13 and, simultaneously, the balls 16 roll on the inner surface 21 of arcuate grooves 20 provided in an outer race 22. The outer race 22 is an integral extension of the output-shaft 14. The output shaft 14 and the outer race 22 are formed integrally by forging, for example.

id i In operation the input shaft 13 and the output shaft 14 are subject to articulation from the normal axial orientation depicted in Figure 1. In the case of the drive joint for a front wheel drive automobile, this articulation can be of the order of forty-five degrees (450) in each direction as a result of normal road vibrations, road bumps, and high speed cornering of the vehicle. The constant velocity drive joint 11 itself is quite capable of acommodating this degree of articulation due to the fact that the balls 16 are in rolling engagement with the spherical surface 18 of the inner race 19 and the arcuate surface 21 of the outer race 22, respectively.

The constant velocity drive joint 11, as heretofore described, contains precision machined components which move relative to one another and, therefore, it must be lubricated and free from dirt and other contaminants that may be encountered in an automotive environment. To this end, the drive joint 11 is provided with a sealing boot, indicated generally at 23, to seal the interior of the drive joint 11. The sealing boot 23 must be capable of accommodating the degree of articulation that the constant velocity drive joint 11 itself is subject to without a loss of the sealing capabilitids during such articulation. For automotive applicati-ons the seal provided by the boot 23 must be reliable and it should be capable of maintaining an efficient seal for many years.

As previously described, the constant velocity drive joint 11 must be capable of accommodating a substantial degree of articulation between the 3 4 input shaft 13 and the output shaft 14. For an automotive front wheel drive joint, this articulation will be approximately twenty degrees (20) in each direction during normal driving and may occasionally be as great as fortyfive degrees (450) during the severe conditions encountered in sharp turns. The necessary articulation of the boot 23 can be obtained by constructing the outer race of the drive joint with a spherical outer surface 24 and by constructing the sealing boot 23 from multiple interleaved members. In the case of a forged outer race, the spherical outer surface 24 is preferably unmachined to reduce the cost thereof. The first member of the boot is an inner member 25 which is provided with radially inwardly extending ribs 26 that sealingly engage the spherical outer surface 24 of the outer race 22. The internal diameter of the inwardly extending ribs 26 is less than the diameter of the outer race's spherical outer surface 24 so that the inner member 25 is held to the inner race by an over center snap fit. It is also contemplated that the sealing boot of the present invention can be utilized with existing universal joints which utilize a cylindrical or other nonspherical outer race. In such a case, a plastic or other type of fitment should be attached to the outer race and this fitment should have a spherical outer surface for effecting a surface-to-surface sealing engagement with the inwardly extending ribs 26 of the inner-member. The sealing boot 23 also includes an outer member 27 which is disposed concentric.with the inner member 25 and in at least partial engagement therewith. The inner member has a circumferential bead 28 provided intermediate its open end, an aperture 30 through which the input shaft 13 passes, and a partially reduced thickness portion 31 extending from the bead 28 to the aperture 30. The outer member 27 also has an aperture 52, concentric with the aperture 30 of the inner member through which the input shaft 13 also passes.

The forward portion 32 of the outer member 27 has an increased thickness which is received in the recess formed in the inner member 25 bet- ween a radial flange 33 provided at its open end 29 and the circumferential bead 28 to lock the outer member 27 to the inner member 25. The inner member 25 and the outer member 27 are sufficiently flexible to permit these members to be snap-locked together by the application of a sufficient force in an axial direction.

The outer surface of the partial reduced thickness portion of the inner member 25 and the inner surface of the outer member 27 define a spherical recess 34 which extends from the input shaft aperture 30 to the circumferential bead 28. An intermediate member 35 of the boot 23 has a generally spherically-shaped, semi-rigid flange 36 which is sealingly received in the spherical recess 34. The intermediate member 35 also has a cylindrical boss 37 which surrounds and sealingly engages the input shaft 13. To assure-the seal between the inner member 25 and the intermediate member 35 an internal bead 38 may be provided about the open end of the spherically-shaped flange 36 to assure the seal between the inner member 25 and the intermediate member 35 as more clearly shown in Figure 3. Similarly, the inner member 25 may have an annular lip 39 about the aperture 30 which sealingly engages the internal surface of the intermediate member 35.

The seal between the input shaft 13 and the cylindrical boss 37 of the intermediate member 35 is effected by a shaft seal 40. Referring to Figure 2, the cylindrical boss 37 has an annular lock recess 41 which receives an inwardly projecting annular dog catch 42 provided on the portion of the shaft seal 40 facing the mechanical joint. The end face of the dog catch 42 has a beveled edge 43 which cooperates with a beveled edge 44 of the cylindrical boss 37 for latching the dog catch 42 in the annular lock recess 41 by applying a sufficient force in an axial direction. Effectively the annular dog catch 42 of the shaft seal 40 and the annular lock recess 41 formed in the cylindrical boss 37 comprise a snap-lock, locking the shaft k 1 j, seal 40 to the intermediate member 35. The end of the shaft seal 40 opposite the dog catch 42 has a pair of inwardly extending shaft seal ribs 45 which sealingly engage the external surface of the input shaft 13.

An alternate embodiment of the shaft seal 40 is shown in Figure 3. In this embodiment the cylindrical boss 37 of the intermediate member 35 includes an annular lock recess 41 as described relative to Figure 2. The alternate embodiment of the shaft seal identified by numeral 46 has an annular dog catch 47 and a pair of inwardly extending shaft seal ribs 48 which correspond to the dog catch 42 and the inwardly exiending shaft seal ibs 45 of the first embodiment shown in Figure 2. The shaft seal 46 further includes an integral hemispherically-shaped shield 49 concentric with the flange 36 of the intermediate member 35 and the external surface of the outer member 27. The shield 49 has an annular lip 50 which sealingly engages the external surface of the outer member 27. To further improve the sealing, an annular bead, such as a bead 51, may be provided about the input shaft aperture 52 of the outer member 27. This bead 51 sealingly engages the internal surface of the shield 49.

The articulation of the constant velocity drive joint 11 is partially accommodated by the articulation of the flange 36 of the intermediate member 35 within the spherical recess 34. The degree of articulation of the flange 36 in the spherical recess 34, preferably, is sufficient to accommodate bumps and turning vibrations encountered during normal operation of the vehicle. The depth of the spherical recess 34 and the diameter of the flange 36 are selected so that the flange 36 may be angularly displaced through a predetermined angle. For an automotive front wheel drive joint this predetermined angle is approximately twenty degrees (200) in each direction. The dimensions of the flange 36 and the depth of the spherical recess 34 are also selected so that the open end of the flange 36 will engage the bottom of the spherical recess 34 27 when the degree of articulation exceeds the predetermined angle. Further, articulation is then k is g- obtained by the rotational displacement of the inner member 25 and the outer member 27 about the spherical outer surface 24 of the outer race 22. This articulation may accommodate up to an additional thirty degrees (30) of articulation in each direction, which is at least five degrees (59 more than is normally required in an automotive front wheel drive joint. This additional articulation comes into play only in unusual circumstances,-such as sharp turns and/or severe road conditions.

The inner member 25, the outer member 27, the intermediate member 35, and the shaft seal 40 are preferably made from tough, puncture resistant, nonelastomeric, or semi-rigid polymeric materials. A polyurethane material has proven to be well suited for the manufacture of each of these members. Preferably the outer member 27 is formed of a material that is somewhat harder than the materials used to form the inner member 25 to provide maximum puncture resistance and better sealing properties in the inner member 25. When so manufactured, the boot 23 will be considerably more resistant to punturing or tearing than the f]P-Xible elastomeric boots of prior art drive joints, and will have dimensions which will fall within precise tolerances, thus, lending itself to mechanical handling techniques during assembly where assembly labor costs can be reduced in that manner. Additionally, the boot 23 will be more. resistant to the extremes of high and low temperatures that can be encountered during the normal life of an automotive front wheel drive joint, and it will be more resistant to degradation from contact with grease contained in the constant velocity drive joint 11. AS another feature of the boot 23, the sliding movement of the flange 36 in the spherical recess 34 will, inherently, be self lubricating due to the fact that a portion of the inside surface of the flange 36 of the intermediate member 35 is in contact with the grease in the constant velocity drive joint. This self lubrication is augmented by the centrifugal forces on the grease during the rotation of the constant velo- r.

k, k.

L i is city drive joint which tends to keep the grease in contact with the inside surfaces of the flange 36 during articulation. Another feature of the boot 23 is that the diameter of the aperture formed by the bead 28 at the open end of the inner member 25 is smaller than the diameter of the spherical outer surface 24 of the outer race 22 and that the inner member 25 by virtue of its non-elastomeric character is retained in place on the spherical outer surface 24 of the outer race by means of a snap fit without the need for a clamp or ring to assist in such retention. This further reduces the cost of the parts involved in the manufacture of the constant velocity drive joint and the cost of assembling such parts. Similarly, the intermediate member 35 is sealingly retained between the inner member 25 and the outer member 27 by the shaft seal 40 without the need for a clamp or a groove to assist in such retention, thus, permitting a further reduction in material and assembly costs.

Various embodiments of the seal boot of the present invention have been described in their application to a drive joint of a constant velocity type, because it is_ contemplated that the invention will have particular util.ity in that field. It is to be understood, however, that it is contemplated that this type of boot or seal can be used with other types of drive joints, such as tripod or ball contact types or even nonconstant velocity drive joints such as Hookes or Cardan joints.

While a preferred and an alternate embodiment of the present invention have been described, it will be apparent to those skilled in the art that changes may be made to the invention as described herein without departing from the scope of the invention as set forth in the appended claims. Accordingly, the description of this invention described herein is intended to be illustrative of the principles of the invention and not to limit the scope thereof.

12 C1dims:- 1. A boot for sealing a power transmitting mechanical joint of the type having an input shaft, an output shaft,_and connection means for connecting the input shaft to the output shaft so that the said shafts can be articulated relative to each other, the connection means including an outer race which has a sphericai external surface and is connected to one of the said shafts, the boot comprising: a hemispherically-shap.ed semirigid inner member having an open end for sealingly engaging the spherical external surface of the outer race of the connection means and a first clearance aperture at the end opposite the said open end for circumscribing the other of the said shafts; a hemispherically-shaped semi-rigid outer member concentric with the inner member and connected thereto, the outer member having a second clearance aperture concentric with the first clearance aperture. at least one of the said members having a reduced thickness portion forming a spherically- shaped recess between the said members. the said recess being open at the end thereof adjacent to the said clearance apertures; a semi-rigid intermediate member having a spherically-shaped flange sealingly and slidingly received in the said recess and a cylindrical boss for 1 13 sealingly circumscribing the said other shaft, the depth of the said recess and radius of the said flange at its open end being such as to permit a"predetermined degree o f articulation of the intermediate member in the said recess, the boss having an annular lock recess in its external surface; and a shaft seal having an inwardly projecting annular dog received in the annular lock recess to lock the shaft seal to the intermediate member. and at least one inwardly extending rib for sealingly engaging the external surface of the said other shaft.

2. A boot as claimed in claim 1. wherein the shaft seat has two inwardly extending ribs for sealingly engaging the external surface of the said other shaft.

3. A boot as claimed in claim 1 or 2. wherein the boss and the shaft seal have beveled surfaces on the ends thereof. which facilitate their relative axial displacement to engage the annular dog in the annular lock recess locking the shaft seal to the intermediate member.

4. A boot as claimed in any preceding claim, wherein the shaft seal includes a spherically-shaped shield which sealingly and slidably engages the external spherical surface of the outer member.

7.

14 5. A boot as claimed in claim 4, wherein the shield has an annular lip about its periphery sealingly engaging the external spherical surface of the outer member..

6. A boot as claimed in claim 4 or 5, wherein the outer member has an annular bead sealingly engaging the internal surface of the shield.

7. A boot as claimed in any preceding claim. wherein the inner member has an annular recess in its external surface adjacent to its open end and the outer member has an inwardly projecting annular portion captivated in the said annular recess to lockingly connect the outer member to the inner member.

8. A boot as claimed in claim 7, wherein the inner member and the outer member have sufficient resiliency to permit the inwardly projecting annular portion to the outer mEmber to be snap-locked into the said annular recess in response to the exertion of a sufficient axial force urging the inner and outer members towards each other.

9. A boot for sealing an articulating rotary joint of the type having an input shaft, an output shaft. an inner race connected to one of the said shafts, an oute race which has a spherical external surface and is I 7 1 is connected to the other of the said shafts, and means for rotatably and articulaely connecting the inner race to the outer race, the boot comprising: a spherically-shaped inner member having an open end for sealingly engaging the spherical external surface of the outer race, a first clearance aperture for circumscribing the said one shaft, and a peripheral recess in the external surface of.the inner member adjacent to the said open end; a spherically-shaped outer member concentrically disposed over the inner member, the outer member having an inwardly projecting annular portion received in the peripheral recess to lock the outer member to the inner member and having a second clearance aperture generally concentric with the first clearance aperture, at least one of the said members having a reduced thickness portion forming a sphericallyshaped recess having an open end adjacent to the said clearance apertures; an intermediate member having a spherically-shaped flange sealingly and movably disposed in the spherically-shaped recess and a cylindrical boss for sealingly circumscribing the said one shaft, the boss having an annular lock recess in its external surface; and a shaft seal having an inwardly projecting annular dog received in the annular lock recess to lock the shaft seal to the intermediate member, and a pair of 16 inwardly extending shaft seal ribs for sealingly engaging the external surface of the said one shaft.

10. A boot as claimed in claim 9, wherein the radius of the sphericallyshaped flange is such as to permit a predetermined articulation of the intermediate member in the spherically-shaped recess.

11. A boot as claimed in claim 9 or 10, wherein the shaft seal includes a spherically-shaped shield slidably and sealingly en gaging the external spherical surface of the outer member.

12. A boot as claimed in any of claims 9 to 11, wherein the boss and the shaft seal have beveled surfaces to facilitate thd insertion of the annular dog in the annular lock recess ina snap-lock type of action in response to an axial force urging the boss and the shaft seal towar.ds each other.

13. A shaft seal of a boot for a mechanical joint having an input shaft, an output shaft, and connection means for connecting the input shaft to the'output shaft, wherein the boot has at least one member having a cylindrical boss for circumscribing one of the said shafts. the shaft seal comprising:

1 c 1 17 an annular lock recess provided in the external surface of the cylindrical boss; and a seal member for circumscribing the said one shaft adjacent the boss, the seal member having at least one inwardly projecting rib for s-ealingly engaging the said shaft and an inwardly projecting annular dog catch received in the annular lock recess to lock the seal member to the cylindrical boss.

14. A shaft seal as claimed in claim 13, wherein the seal member has two inwardly projecting ribs for sealingly engaging the said one shaft.

15. A shaft seal as claimed in claim 13 or 14. wherein the seal member has a spherically-shaped shield sealingly and slidably engaging a spherically-shaped_ external surface of at least one outer member of the boot.

16. A shaft seat as claimed in claim 15, wherein the shield has an inwardly projecting annular lip about its periphery, which sealingly engages the said spherically-shaped external surface.

17. A power transmitting mechanical joint having an input shaft and an output shaft connected for relative articulation by connection means including an outer race 18 which has a spherical external surface and is connected to one of the said shaft. and being provided with a boot according to any of claims 1 to 8.

18. An articulating rotary joint having an input shaft. an output shaft, an inner race connected to one shaft, an outer race which is connected to the other shaft and has a spherical external surface,-and means forrotatably and articulately connecting the recess, and being provided with a boot according to any of claims 9 to 12.

19. A boot substantially as described with reference to, and as shown in. Figures 1 and 2 or Figure 3 of the accompanying drawings.

Published 1989 at The Patent Office, State House. 66 71 High Holborn. London WCI R 4T? F=her copies maybe obtained from The Patent OfEice.

Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed bY Multiplex techniques ltd, St Mary Cray. Kent. Con. 1187 mues isranch,,St MaXY Cray. Orpington, Kent BRS 3RD. Printed bY Multiplex techniques ltd, st Mary Cray. Kent. Con. 1187 k 7