Bearing unit

A bearing unit of this invention includes, instead of a conventionally used bracket, a housing formed with an external thread and a bush press fitted in an inner bore of the housing.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a bearing unit for use in industrial 
machines, such as automobiles, marine vessels, various types of electrical 
machines, business machines, agricultural machines, machine tools, 
foodstuff machines, textile machinery, and packaging machines. More 
particularly, the present invention concerns a bearing unit provided with 
screws which make the unit detachable to an industrial machine. 
2. Description of the Prior Art 
Hitherto, an expensive bracket having a complicated structure has been used 
for mounting a bearing in an industrial machine. Such a bracket is formed 
integral with a housing having an inner bore of high precision for 
receiving a plain bearing bush. 
It is difficult to accurately machine the inner bore of the aforementioned 
housing with a bracket within a short time, and machining is extremely 
difficult particularly in cases where a plurality of plain bearing bushes 
are aligned in and press fitted in the inner bore of the housing. 
SUMMARY OF THE INVENTION 
According to the present invention, there is provided a bearing unit 
including a housing with an external thread and a bush adapted to be press 
fitted in the inner bore of the housing. This housing is screwed or 
inserted into a hole with or without an internally threaded bore of an 
industrial machine to which the bearing unit is to be applied, and is then 
secured by means of a nut or nuts.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1, there is shown a bearing unit 1a of a double-nut 
tightened type in accordance with a first embodiment of the present 
invention. This bearing unit includes a housing 5a provided with external 
threads, two bushes 7 adapted to be press fitted into an inner bore 6a of 
the housing, and two nuts 8 screwed onto the external threads of the 
housing. The housing 5a is formed of chromium molybdenum steel (SCM435) or 
the like, and the bushes 7 are in the form of, for instance, a DU Dry 
Bearing, a DX Dry Bearing, or a DIVEST bushing with a backing metal. In 
this embodiment, two bushes 7 are used, but one or three bushes may be 
used. The two nuts 8 interpose therebetween a portion 3 of an industrial 
machine upon assembling of a bearing unit, and washers and/or spring 
washers may be placed between the nuts 8 and the portion 3. In case an 
internal thread 2 is formed in the portion 3 of the industrial machine, 
the housing 5a may be screwed directly into that portion, and the nuts 8 
may be omitted. In addition, if a rust preventive is required, the overall 
bearing unit may be plated. The DU Dry Bearing is a registered trademark 
of Gracia Metal Ltd., a British company, and is a high performance PTFE 
bearing made by sintering porous bronze on a backing metal (steel or 
bronze) and impregnating and coating the same with a mixture of PTFE and 
Pb. The DIVEST bush is a registered trademark of Daido Metal Co., Ltd. 
This bush is manufactured by impregnating and coating pores and surfaces 
of a porous metallic layer provided on the surface of a backing metal with 
a composition which includes as its major component a synthetic resin such 
as polyacetal, resin and as additives a lipophilic fibrous material and a 
lubricant oil agent as well as metallic soap and/or a solid lubricant, as 
required, and by sintering the same. The DX Bearing is also a registered 
trademark of Gracia Metal Ltd., a British company, and is a polyacetal 
prelubricated bearing produced by adding an abrasion-resistant agent to 
polyacetal resin, instead of PTFE and Pb of the aforementioned DU Dry 
Bearing. 
Referring to FIG. 2, there is shown a bearing unit 1b of a single-flanged 
single-nut tightened type. This bearing unit differs from the bearing unit 
1a of the first embodiment in the shape of a housing 5b thereof and in the 
use of only one nut 8. In other words, the housing 5b includes a 
cylindrical outer peripheral surface 9b formed concentrically with an 
inner bore 6b with high precision, a flange 10b formed at one end portion 
thereof, and an external thread 4b formed at the other end portion 
thereof. A space 11b formed between the two bushes 7 disposed about both 
ends of the inner bore 6b may be used as a grease reservoir or an oil 
reservoir. In this case, two rotary shafts may be inserted from both ends 
of the bearing unit, respectively. 
Referring to FIG. 3, there is shown a bearing unit 1c of a single-flanged 
and stepped and single-nut tightened type in accordance with a third 
embodiment of the present invention. This bearing unit differs from that 
of the second embodiment in that the outside diameter of a housing 5c 
thereof and that of a flange 10c are greater than those of the latter. 
Referring to FIG. 4, there is shown a bearing unit 1d of the single-flanged 
and stepped and single-nut tightened type in accordance with a fourth 
embodiment of the present invention. This bearing unit differs from those 
of the second and third embodiments in that the inner bore of a housing 5c 
thereof is enlarged and a D bush 7' is press fitted in this inner bore. 
Referring to FIG. 5, there is shown a bearing unit 1e of the single-flanged 
and stepped and single-nut tightened type in accordance with a fifth 
embodiment of the present invention. This bearing unit includes a nut 8, a 
housing 5e and a bush 7. The housing 5e includes a bolt 12e provided with 
an external thread, a cylindrical portion adapted to be mounted in the 
portion 3 of the industrial machine and a flange 10e. An inner bore 13e in 
the form of a blind bore is formed in the flange 10e, and the end portion 
of this inner bore may be used as a grease or oil reservoir. 
Alternatively, a thrust washer or a thrust bearing may be fitted into the 
inner end portion of the blind bore to bear a thrust load in the axial 
direction. The bush 7 is press fitted in the inner bore 13e. The nut 8 may 
be omitted by forming an internal thread in the bore of the portion 3 of 
the industrial machine. In addition, a flanged bush 7e may be used instead 
of the bush 7, as shown by a chain line in FIG. 5. Furthermore, 
alternatively, in addition to the bush 7e shown in the Figure, a thrust 
washer may be secured to the end surface of the flange 10e by screws or an 
adhesive so as to bear a radial load and a thrust load. 
Referring to FIG. 6, there is shown a bearing unit 1f of a type provided 
with a semi-spherical cup seat in accordance with a sixth embodiment of 
the present invention. This bearing unit includes a plastic housing 5f and 
a semi-spherical cup-type bearing member 7f formed of a slide bearing 
material. The housing 5f has a generally cylindrical shape, and is formed 
at its outer peripheral surface with an external thread. The one end of 
the housing 5f is formed with a substantially semi-spherical recess and a 
flange 10f which recess receives the cup-type bearing member 7f. In 
assembly, the external thread of the housing is screwed into the portion 3 
of the industrial machine, and the flange 10f is adapted to abut against 
the portion 3. 
Referring to FIG. 7, there is shown a bearing unit 1g of a drawn-flange 
type. This bearing unit includes a housing 5g formed of a deep drawn steel 
plate and a single-flanged bush 7 such as a wrapped bush bearing. The 
housing has an external thread 4g formed on the outer peripheral surface 
thereof and a flange 10g formed at one end portion thereof. The housing 
may be made of a synthetic resin instead of the deep drawn steel plate, 
and when the threaded portion 4g is sufficiently screwed in that portion 
upon mounting to the portion 3 of the industrial machine, the housing 
abuts against the end surface of that portion. As shown in FIGS. 5 and 7, 
when a single-flanged bush or double-flanged bush (not shown) is used, a 
rotary shaft is formed with a step and the step is made to abut against 
the flange of the bush. 
Referring to FIG. 8, there is shown a bearing unit 1h of a drawn flange and 
bottomed type in accordance with an eighth embodiment of the present 
invention. This bearing unit is similar to the bearing unit of the seventh 
embodiment except that the outside diameter of a flange 10h thereof is 
small and the end portion of the housing 5h is made blind as at 17h. The 
bearing unit shown in FIG. 8 is useful in terms of the safety of the end 
portion of a rotary shaft, enclosing of grease and prevention of entrance 
of dust. The housing 5h may be formed of a synthetic resin instead of a 
deep drawn steel plate. The bearing unit 1h shown in FIG. 8 may be made to 
bear a thrust load by placing a thrust washer or a thrust bearing in the 
blind end portion as in the case of the bearing unit 1e shown in FIG. 5. 
Alternatively, a thrust load in the axial direction may be born by placing 
a thrust washer or a thrust bearing at the innermost portion of the blind 
bore. 
Referring to FIG. 9, there is shown a bearing unit 1i in accordance with a 
ninth embodiment of the present invention. This bearing unit includes a 
housing 5i formed with a flange 10i and an external thread 2i, a 
single-flanged bush 7i and a lipophilic fibrous member 14i. The 
single-flanged bush 7i is formed at its inner peripheral surface with an 
oil groove 15i, an oil thrower groove 16i and an oil window 17i. The 
flange 10i of the housing is provided about the inner peripheral portion 
thereof with an oil seal 18i. 
Referring to FIG. 10, there is shown a bearing unit 1j of a double-nut 
tightened type in accordance with a tenth embodiment of the present 
invention. This bearing unit is similar to the bearing unit 1a shown in 
FIG. 1 except that a housing 5j thereof is formed at the central portion 
thereof with a cylindrical surface. In assembly, the cylindrical portion 
in the center of the housing 5j fits in the cylindrical inner bore of the 
portion 3 of the industrial machine. A thrust washer or a thrust bearing 
(not shown) may be arranged in the space formed between both the bushes 7 
press fitted in the inner bore 6j of the housing 5j to bear a thrust load. 
The same is the case with the bearing units shown in FIGS. 1 to 4. 
Thrust load applied by two rotating shafts can be born by inserting from 
the opposite end of the housing 5j shown in FIG. 10 bearing bushes 
described in Japanese Patent Application No. 145855/1984 (Japanese Patent 
Laid-Open Publication No. 24815/1986) and having a bore and an inward 
directed flange. Furthermore, cup-shaped bearing bushes without a bore may 
be press fitted from both sides of the housing. When either of these 
bearing bushes described above is replaced by the bearing bushes shown in 
FIGS. 1 to 5 and FIG. 8, it becomes possible to bear both a radial load 
and a thrust load simultaneously. 
According to the present invention, a housing having a bush press fit 
therein has an external thread along the overall or partial length of the 
outer peripheral portion thereof, whereby it becomes possible for the 
housing to be mounted in a threaded bore or inner bore of a portion of an 
associated industrial machine. In addition, two bearing bushes can be 
incorporated into a housing, so that alignment thereof can be facilitated, 
and partial abrasion of the bearing resulting from one-sided contact of a 
rotary shaft can be prevented. 
In addition, the bearing unit of the present invention is fit for various 
uses because adjustment of movement in the axial direction can be made by 
the provision of a thread in the housing. Moreover, bearing units provided 
with a thread in accordance with the present invention can be manufactured 
at low cost in comparison with a conventional arrangement having a bracket 
integral formed with a housing.