Motor bearing and bracket therefor

A plastic bracket and bearing assembly for a shaft of a fractional horsepower electric motor which includes a molded heat insulating plastic article having two or more feet attachable to the motor and spaced outwardly from a central hub having a recess for receiving a washer-shaped lubricating wick of fibrous material, spaced passageways in the bracket to provide oil to the wick, and a spherical self-aligning bearing block with a bore for supporting the motor shaft.

BACKGROUND OF THE INVENTION 
Fractional horsepower electric motors are generally small machines which 
during their operation generate a surprising amount of heat in the motor 
windings. This heat causes the lubricating oil to become thin and 
evaporate too quickly, and to cause damage to the bearings and the shaft 
of the motor and then to the motor itself. It is therefore extremely 
important to dissipate the heat away from the bearings to the maximum 
extent possible. One improvement has been to employ a fan on the motor 
shaft which will blow air over the bearing to assist in cooling it. 
Another improvement has been to employ metal bearing members in plastic 
housings. Still another improvement has been the use of porous bronze 
bearing members lubricated by oil passing through a fibrous wick which is 
in contact with the bearing. Typical of such improvements are those shown 
in U.S. Pat. Nos. 3,034,838; 3,037,822 and 3,934,953. None of these 
patents, however, shows an optimum combination of features for a small 
fractional horsepower electric motor. 
It is an object of this invention to provide an improved bearing and 
bearing bracket for a small electric motor. It is another object of this 
invention to provide an improved bearing and bearing bracket for a 
fractional horsepower electric motor that generates considerable heat 
during operation. Still other objects will become apparent from the more 
detailed description which follows. 
BRIEF SUMMARY OF THE INVENTION 
This invention relates to a bearing and a bracket for the bearing. The 
bearing is for a shaft of a fractional horsepower motor and includes a 
bearing block, a lubrication wick and a plastic housing for the block and 
the wick; the bearing block being a solid cylindrical member with 
hemispherical ends and being symmetrical about a diametrical through bore; 
the wick being a washer-shaped member of fibrous material; and the housing 
including a central hub with a cylindrical recess adapted to accommodate 
the wick at its outer end and the bearing block at its inner end 
contiguous to the wick, a passageway connecting the inner portion with the 
atmosphere surrounding the housing, and at least two feet spaced apart 
from the hub each with a through bore to accommodate screw member to 
fasten the housing to the motor. 
The bearing bracket comprises a housing with a cylindrical recess for 
receiving a generally cylindrical bearing block, in a press fit and 
adjoining the recess is an undercut portion for receiving a washer-shaped 
lubrication wick of fibrous material contiguous to the bearing block, the 
housing also having feet for attachment of the housing to the motor, and 
the plastic being a poor conductor of heat to inhibit evaporation of 
lubrication from the wick. 
In specific and preferred embodiments of the invention the housing is made 
of a plastic that is a poor conductor of heat and has at least two feet 
that contact the electric motor and support the remainder of the housing 
spacedly away from the motor.

DETAILED DESCRIPTION OF THE INVENTION 
This invention relating to a bearing and to a bearing bracket can best be 
described with reference to the attached drawings. 
FIG. 1 shows schematically a small fractional horsepower electric motor 30 
with the motor shaft 32 extending outwardly from opposite sides of the 
motor 30. A bearing bracket 31 containing internally a bearing block is 
positioned over the shaft 32 on each side of the motor 30 to support the 
shaft 32 in a free turning manner. Each bracket 31 has two feet 11 which 
are fastened to the motor 30 by screws 33. The main support member of the 
bearing bracket 31 is span 16 which is spaced away from motor 30 by the 
design of feet 11 so as to leave an air space 25 between the motor 30 and 
the bracket 31. The flow of air in space 25 helps to insulate the bearing 
from the heat generated by the motor windings. Normally a fan blade is 
attached to shaft 32 on one side of motor 30 with its blades designed to 
cause air currents to flow over motor 30 so as to cool motor 30. Rotor 34 
of motor 30 turns with shaft 32 and is supported by a bearing block 
mounted internally in hub 10 of bracket 31. 
The bearing bracket 31 in FIG. 1 is shown in detail in FIGS. 2-4. Bracket 
31 includes a central hub 10 having an internal recess 15 and at least two 
feet 11 spaced outwardly on opposite sides of hub 10. If there are two 
feet 11, they will be on diametrically opposite sides of hub 10. If there 
are three or more feet 11, they will be equally spaced radially around hub 
10 but not necessarily on a diameter. 
Each foot 11 is designed to rest against the motor to which it is fastened 
by a screw or rivet or bolt or the like via bore 21 and counterbore 24 to 
receive the head of the fastener element. Preferably, but not necessarily, 
a small locating flange 26 extends beyond the seating surface 35 of foot 
11 to fit into the corresponding bore or threaded hole in motor 30. Except 
for the seating surface 35 of each foot 11, the remaining portion of 
bracket 31 is spaced away from and does not touch motor 30 other than at 
the shaft bearing. Feet 11 are joined by a main support span 16 to central 
hub 10 so as to leave an air space 25 between the bracket 31 and motor 30. 
Preferably, there also is a stiffening or reinforcing rib 14 extending 
between each foot 11 and hub 10 on the underneath side 37 of bracket 31. 
Hub 10 is also reinforced by a plurality of short angle ribs 13 on the 
upper surface 36 of main support span 16 extending laterally toward each 
foot 11, respectively. Ribs 13 and 14 are not critical to the design of 
the bracket of this invention and may be modified or eliminated in designs 
where other means are employed to strengthen the structure of the bearing 
bracket 31. 
Hub 10 is designed to contain the bearing for shaft 32. While the bearing 
may be a ball bearing assembly or a roller bearing assembly or a journal 
or block bearing, the latter is preferred because of simplicity and 
inexpensiveness. Shown in FIG. 4 in an exploded arrangement is a bearing 
block 28 with a central bore 29 to receive shaft 32. Bearing block 28 is 
pressed into recess 15 in bracket 31 so as to be stationary with respect 
to bracket 31. It is entirely acceptable for bearing block 28 to be 
fastened into bracket 31 by other means such as cementing, by set screws, 
etc., but a frictional holding is preferred because of ease of assembly. 
Recess 15 is generally cylindrical so as to match and receive cylindrical 
surface 38 of bearing block 39. Preferably, the two end portions 39 of 
bearing block 28 are hemispherical so as to provide a small amount of 
alignment adjustability to bearing block 28. This is typical for 
self-aligning block bearings or journal bearings to compensate for minor 
discrepancies between the alignment of shaft 32 and the alignment of bore 
29 in bracket 31. 
Recess 15 is shown to be cylindrical from inner end 18 to outer end 19. At 
outer end 19 there is a passageway 22 through which shaft 32 extends 
outwardly of bracket 31. At outer end 19 of recess 15 there is a seat for 
lubrication wick 27 which is a washer-shaped piece of fibrous material, 
which may be natural, synthetic, metallic, or the like capable of forming 
a reservoir for lubricating oil to lubricate shaft 32 rotating in bearing 
block 28. Preferably, bearing block 28 is a porous bronze material capable 
of transmitting oil through the solid block in the pores of the bronze. If 
bearing block 28 is nonporous, the lubricating oil must flow around the 
outside of block 28 and into the interface between shaft 32 and central 
bore 29. The outer end 19 of bracket 31 is pierced by one or more 
passageways 20 through which oil may be fed into wick 27 when needed. 
Preferably wick 27 is washer-shaped and held in place by recess 15 and by 
downwardly depending flange 23 at shaft passageway 22. Other shapes of 
wick 27 and means for retaining those shapes in place are operable in this 
invention. Furthermore, the shape of recess 15 may be modified, e.g., to 
include a hemispherical seat for the outer end of bearing block 28, even 
though this might require other modifications to provide proper 
lubrication channels for shaft 32. 
The bearing assembly of bracket 31, bearing block 28, and wick 27 wherein 
bracket 31 is made of a molded plastic that is a poor conductor of heat is 
a great improvement over similar bearing structures where bracket 31 is a 
metal. Metal conducts heat very well and accordingly conducts the heat 
from the motor windings (temperatures of about 185.degree.-300.degree. F.) 
very efficiently to bearing block 28 which causes lubrication problems. 
The oil becomes heated which breaks down its viscosity and its lubricating 
characteristics, and it causes the oil to evaporate to dryness much more 
rapidly than when its temperature is reduced. The bearing bracket of this 
invention is made of a heat insulator which protects the bearing and the 
lubricating oil from the high temperatures developed by the motor, leaving 
the bracket cool to the touch (approx. 100.degree.-150.degree. F.). 
Preferred plastic materials are thermoplastics such as polyacetales, 
polycarbonates, polyamides, polyolefins and the like. A particularly 
desirable plastic is ULTEM made and sold by General Electric Co. The 
plastic must be a poor conductor of heat, but also must be structurally 
strong so as to hold the rotor shaft 32 in a steady position. Reinforced 
plastic materials are also operable. 
A second feature of this bearing bracket is that it may be designed to be 
as small as the natural strength of the plastic will permit. Small sizes 
are advantageous in that there is less of the bracket to receive heat from 
the motor, and therefore less heat to handle, since the remainder will be 
dissipated to the surrounding atmosphere by radiation and convection. 
Corresponding applications in metal or in plastic show that the volume of 
the plastic bracket may be only about 50-75% of the volume of a 
corresponding bracket in white metal. Similarly the weight of the plastic 
bracket may be from 25% to 75% of the weight of a corresponding white 
metal bracket. 
It is, of course, important to the design of the bearing bracket of this 
invention that the physical contact between the bearing bracket and the 
motor be kept to a minimum. This is accomplished by designing the bearing 
with a plurality of feet having minimum area of actual contact with the 
motor while keeping the remainder of the bearing bracket spaced away from 
the motor. These criteria provide for a minimum conduction of heat from 
the motor to the bearing and the lubricant. In the present design this is 
accomplished by minimizing the area of contact between surface 35 of feet 
11 and motor 30, and by maximizing the air space 25 between main span 16 
of bracket 31 and motor 30. 
While the invention has been described with respect to certain specific 
embodiments, it will be appreciated that many modifications and changes 
may be made by those skilled in the art without departing from the spirit 
of the invention. It is intended, therefore, by the appended claims to 
cover all such modifications and changes as fall within the true spirit 
and scope of the invention.