Rotary shafts – gudgeons – housings – and flexible couplings for ro – Housing – Flexible housing
Reexamination Certificate
1998-09-22
2001-06-12
Browne, Lynne H. (Department: 3629)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Housing
Flexible housing
C024S0200CW
Reexamination Certificate
active
06244967
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a constant velocity joint having a fixing construction wherein a bellows-like resin boot is fixed at boot attaching portions by boot bands.
Constant velocity joints have a boot mounted thereon in order to prevent leakage of grease sealed in the joint and entry of foreign matter into the joint. Such boot is clamped and fixed at a boot attaching portion of an outer joint member and at a boot attaching portion of a shaft portion of the constant velocity joint by boot bands, respectively. As for such constant velocity joint boots, rubber boots made of rubber, such as chloroprene rubber (CR), and resin boots made of resin material are in common use. In recent years, however, there has been a tendency for resin boots to be used more frequently from the viewpoint of rotational expansion resistance and durability.
FIG. 14
shows a constant velocity joint
11
having a conventional bellows-like resin boot
12
mounted thereon. The resin boot
12
has cylindrical boot fixing portions
12
a
and
12
b
on the larger and smaller diameter sides with a bellows portion
12
c
disposed therebetween. The boot fixing portion
12
a
on the larger diameter side is clamped and fixed at a boot attaching portion of an outer joint member
11
a
by a boot band
13
and the boot fixing portion
12
b
on the smaller diameter side is clamped and fixed at a boot attaching portion of a shaft portion lie by a boot band
14
.
A resin boot, as compared with a rubber boot, has a high hardness, lacking in elasticity; therefore, in order to secure a sufficient fixing strength and sealability it is common practice to use, as boot bands, crimp type bands (omega bands)
13
and
14
having clamp portions of omega (&OHgr;) shape which provide a greater clamping force. The reason why the omega bands have been used for the conventional resin boots is that such a boot band as so-called lever type boot band (a band of the type adapted to clamp by folding back a lever member), which is conventionally used for rubber boots, has failed to provide a sufficient clamping force if they used with the conventional resin boots.
The omega bands
13
and
14
, as compared with the lever type boot band and the like, is capable of providing a large clamping force. On the other hand, it has disadvantages in design; for example, since it has a form in which a clamp portion projects radially outward, its maximum radius of rotation is so large as to require a large space to avoid interference with the peripheral parts. Further, since the clamp portion is projecting, its chance of encountering foreign substances (such as flying stones) increases. Further, the band itself is complicated in shape, and requires a greater wall thickness and a greater width than those of boot bands used for rubber boots; thus, it is disadvantageous also from the viewpoint of cost. On the other hand, some of the boot bands have no projecting clamp portion, however, if they are applied to resin boots, it has been difficult to secure a sufficient fixing strength and sealability.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a fixing construction which has no projecting clamp portion and is capable of securing a sufficient fixing strength and sealability for resin boots.
To achieve the object, the invention uses the so-called lever type boot band having no projecting clamp band portion as a boot band for clamping at least one of boot fixing portions of a resin boot and thereby fixing it to boot attaching portion of a constant velocity joint. That is, to use such a boot band that comprises, a band member of band-like metal material, the band member being bended in annular shape and having a joined portion in which opposite ends of the band member are joined together in a state of inner surfaces thereof met each other, and a lever member of metal material having higher rigidity than that of the band member, the lever member being attached to one outer surface of the joined portion of the band member. The lever member is folded back by making use of leverage to clamp the boot fixing portion, and then the lever member is placed on and fixed to an outer surface of the band member. This boot band is simple in construction and has no projecting clamp portion, so that it is advantageous from the viewpoint of design and cost. Further, since the chances of encountering foreign substances are low, a stabilized fixed state can be maintained.
Further, in order to secure a sufficient fixing strength and sealability, the invention uses the following technical means.
(1) The resin boot was made of a thermoplastic polyester type elastomer whose hardness was such that 38≦H
D
<50, preferably 41≦H≦47, for example H
D
=47. Thereby, as compared with the conventional resin boot (conventionally, H
D
is 50 or above), the material hardness is reduced and the pliability is improved, and simultaneously, the stresses (tension and compression) during bending produced in the troughs are reduced and the bending fatigue resistance of the troughs are improved. Herein, “H
D
” indicates the D scale of the Shore hardness (based on ASTM).
(2) The average wall thickness T of each ridge of the bellows portion of the resin boot was such that 0.5 mm≦T≦1.5 mm, the average wall thickness t of each trough was such that 0.5 mm≦t≦1.5 mm, the wall thickness ratio r (=t/T) of the trough to the ridge in each pair which consists of adjoining ridge and trough was such that 1.0≦r<1.5, the maximum value Tmax of the average wall thickness T of the ridges was related to its minimum value Tmin such that Tmax≦1.5 Tmin, and the maximum value tmax of the average wall thickness t of the troughs was related to its minimum value tmin such that tmax≦1.5 tmin. By setting the wall thickness ratio r (=t/T) in the above range, as compared with the conventional resin boot (conventionally, the t/T=1.5−2.1), the elasticity of the troughs with respect to the ridges is increased (since the wall thickness is relatively decreased), the stresses (tensile and compressive) in the troughs are decreased, and the bending fatigue resistance of the troughs is improved. Further, by setting the maximum value of the average wall thickness for both the ridges and the troughs at not more than 1.5 times the minimum value, the compression produced when the joint is attached is distributed with good balance over each trough, so that there is no inflection point formed in the (compressive load)-(amount of axial compression) diagram.
(3) In accordance with the constructions in the above paragraphs (1) and (2), it is possible, while securing a durability which is equal to or greater than the durability of the conventional resin boot, to attain compact-sizing (reduction of the outer diameter, reduction of the axial length). The reduction of the material hardness of the resin boot (improvement in pliability) and compact-sizing through reduced wall-thickness will work advantageously in securing fixing strength and sealability for constant velocity joints.
(4) The wall thickness S
3
of the boot fixing portion of the resin boot was such that 1 mm≦S
3
≦1.8 mm and the calculated clamp interference &dgr; defined below was such that 0<&dgr;≦1.6 mm:
&dgr;={&phgr;
A
+(2
×S
3
)}−&phgr;
D
where
&phgr;D: calculated clamping inner diameter of boot band:
&phgr;A: maximum outer diameter of boot attaching portion
S
3
: wall thickness of boot fixing portion
(wall thickness prior to application of clamping force).
During the clamping of the boot band, a slight amount of elongation is produced in the band member by the clamping force. The diameter &phgr;D is the clamping inner diameter calculated by neglecting the elongation of the band member, etc., produced during the clamping. The diameter &phgr;A is the outer diameter of the top surface of the projection (see
FIGS. 2 through 4
) when such projection is provided on the boot attaching portion. Also, &phgr;A is the oute
Takabe Shinichi
Terada Kenji
Arent Fox Kintner Plotkin & Kahn
Binda Greg
Browne Lynne H.
NTN Corporation
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