Bearing Lock for a Dynamoelectric Machine

In previous constructions of a bearing lock assembly with dynamoelectric machines, the bearing lock is often assembled before the machine was completely assembled. The prior art has suggested a locking device applied after the motor is assembled. For example, U.S. Pat. No. 3,930,695 discloses a locking means operable from the outside of the motor enclosure. With the construction of the present invention, an electric motor, for example, may be completely assembled and thereafter the bearing lock accurately assembled in place in a bearing and bracket provided for that purpose to reliably and firmly lock the bearings in place. The means of locating the lock relative to the bearing and the means in which the bearing lock preload is applied and supported distinguishes the invention from the prior art.

The invention is directed to a bearing locking assembly for a dynamoelectric machine such as an electric motor. The construction has a bearing bracket at an end of a motor which is secured to the frame of the motor and has a bearing seat which receives a shaft bearing. In an optimum structure, the shaft bearing has an outer race projecting slightly inwardly of the bracket. The bracket has housings or abutments which are located on opposite sides of the motor shaft, and each housing ordinarily has the same bearing fastening construction. Each housing has a generally central opening closed by inboard and outboard walls each of which has a non-circular slotted opening normally in alignment with each other and extending across the bearing. The inward wall has offset stops on each side of the slotted opening therein. A bearing fastening means is inserted through the opening in the outboard wall of the bracket and in a first embodiment consists of a fastener having threads on the inside and a generally large head which when rotated in place in the inboard slotted opening locates it between and abutting the stops to limit the rotation and overlaps the bearing and radially outer wall of the abutment. The fastener is drawn outwardly to abut the bearing and lock the bearing in its seat. The outward movement of the fastener is selected to deflect the head, such that the side opposite the bearing engages the spaced outer wall of the abutment. The fastening member thus extends through the slotted opening in the inboard wall and to the outboard wall and a screw is threaded into the fastener in the first embodiment. Under the head of the screw is a washer and when the screw is threaded home in the fastener the head of the screw holds the washer in engagement with the outboard wall and locks the fastener to the bearing and also aligns the screw to the T-head so that the locking forces are axial on the outer race of the bearing, and the deflected head engaging the outer wall limits the stress in the head and functions as an effective "lock" washer on the assembly.

Under a second embodiment of the invention, the fastener is threaded on the outer end and receives a washer and nut which when threaded thereon and against the outboard wall of the housing again secures the generally large T-shaped head on the fastening member against the bearing outer wall of the abutment and the fastener then similarly locks the bearing to its seat .

FIG. 1 is a cross section of the first embodiment of the invention assembled around the end of an electric motor and with a partially tightened bearing lock assembly and taken on line 1--1 of FIG. 3;

FIG. 2 is a detailed enlarged view of one of the housings of FIG. 1 illustrating the fastening member secured in place of the lock assembly;

FIG. 3 is an end view of the fastening construction illustrating the two fastening members in place on opposite sides of the motor shaft;

FIG. 4 is a detailed sectional view of the illustrated embodiment of the invention with the bearing lock assembly in the fully secured position;

FIG. 5 is a view taken on line 5--5 of FIG. 1; and

FIG. 6 is a detail view of a portion of a second embodiment of the invention.

Referring to the drawings, there is shown one end of an electric motor 1 which has a frame 2 and a shaft 3 on which is mounted the rotor 4 which rotates within the stator 5.

A bearing locking bracket 6 is secured at one end of the electric motor 1 over the shaft 3 and held against frame 2 by a bolt 7 which extends through the motor and through a bearing locking bracket, not shown, at the opposite end of the motor and secured in place as by a locking bolt head, not shown.

Bearing locking bracket 6 extends inwardly from frame 2 and as illustrated, has a first abutment or housing 8 on one side of shaft 3 and a second abutment or housing 9 on the opposite side of shaft 3. A number of housings other than housings 8 and 9 may be provided in the locking bracket. Bearing seat 10 is provided in bracket 6 around shaft 3 and receives the bearing which has an outer race 11 and an inner race 12 within which are located the ball bearings. The shaft 3 may be notched at 13 in line with seat 10 to locate the bearing around shaft 3 and shaft 3 rotates within the inner race 12 of the bearing. The bearing and particularly the outer race 11 projects slightly outwardly of the bearing seat 10, as at 13a, and most clearly shown in FIG. 4.

It may be required that the bearing be locked in place in its seat and this may be accomplished under the invention after the motor 1 is completely assembled or as a preassembly to the bracket. The locking construction will be described in connection with the first housing 8, as particularly shown in detail in FIGS. 2 and 4 of the drawing. The locking construction of the second housing 9 normally would be the same as that of the first housing.

In the first embodiment of the locking mechanism, the housing 8 has openings 14 provided in alignment in the inboard wall 16 and outboard wall 17 of the housing 8. A central opening 15 extends between openings 14 and is bordered by the side walls 16a to form a continuous passage for receiving a fastening member. The slotted openings are of a size to permit passage therethrough of the generally large head 18 of an internally threaded fastening member 19. Head 18 is generally rectangular in shape and gives the fastener 19 a T-shaped appearance and the openings 14-15 are angularly offset from the T head locking position. In the illustrated embodiment, the openings are shown in a horizontal plane, but may be rotated about the shaft to any other location. In assembly of the fastener 19 it is first passed through the horizontally slotted opening 14 in the outboard wall 17 and thence through the central opening 15 and the corresponding slotted opening 14 in the inboard wall 16. Fastener 19 is then rotated by a screw 20, which threads into the fastener 19, a one quarter turn to angularly locate the head relative to the bearing outer race in a generally perpendicular position and abutting tabs or stops 21 which prevent any further rotation of the head once it is in locking position. The tabs 21 are located one each to opposite sides of the inboard slotted opening 14 and are located to lock the head 18 of the fastener 19 in position with one end over the outer race 11 of the bearing, as at 21a, and the opposite end over the outer wall 16 of the bracket opening as at 21b. Housing walls 16-17 locate head 18 radially with respect to the bearing to assure that the T-shaped head 18 will overlap the outer race 11 of the bearing.

Under the first embodiment of the invention the screw 20 is threaded into fastener 19 through the slotted opening 15 in the outboard wall 17 of the housing 8. A washer 24 which may be generally of the shape of T head 18 is assembled over screw 20 before screw 20 is threaded into fastener 19. THe washer 24 is seated in a recess in outboard wall 17 and maintains alignment of screw 20 relative to the head 18 to assure that the assembly is parallel with the axis of the bearing. The head of screw 20 engages washer 24 and locks it securely against the outboard wall 17. This secures T-shaped head 18 of fastener 19 against the outer race 11 of the bearing to lock the bearing into seat 10. As noted previously, the bearing projects outwardly of its seat and particularly defines a gap or space 13a between the innermost engaged face of bearing race 11 and the inboard wall 16, as shown in FIGS. 1 and 4. This assures that the bearing lock tightens against the bearing as the result of turning screw 20 and outward movement of fastener 19. T-shaped head 18 in locking position is located between the tabs 21 to assure that the head will rotate over wall 16 and then be locked in place between tabs 21 by the internal tightening of screw 20. Continued tightening of screw 20 will cause T head 18 to deflect to the position of FIG. 4 and thus be supported by the bearing race 11 at 21a one side and a clamp portion 21b of the inboard wall 16 on the other side, as shown most clearly in FIG. 4. This clamping action reduces stress on T head 18 from what it would be if the secondary support were not there and the construction tends to act like a lock washer, should the fastener be subject to vibrations or the like. The location of the head 18 between the tabs 21 prevents rotation of head 18. The bearing locking assembly holds the bearing in place by means of an axial preload on outer race 11 against bearing seat 10. The preload is the axial force generated by and proportional to the torque applied to screw 20.

In the second embodiment of the invention illustrated in FIG. 6, the locking fastener 19 has an enlarged T-shaped head 25 at the inner end and an outwardly extending shank which has threads 25a at the outer end. The housing 8 in which the fastener 19 is lodged may be as in the first embodiment and with openings 14-15 and bordered at opposite ends by inboard wall 16 and outboard wall 17. The respective walls 16 and 17 have the aligned slotted openings 14 and tabs 21 are located on both sides of the opening 14 in inboard wall 16 to prevent rotation of the fastener when it is located in place, the same as in the first embodiment. A washer 26 is assembled over threads 25 and a nut 27 is then threaded onto the threads 25a of the fastener 19, thereby locking fastener member 25 against the inboard wall 16 and washer 26 located in a recess in the outboard wall 17 of housing 8. Nut 27 is threaded onto the fastener 19 to initially rotate it a quarter of a turn to locate the head 25 thereof in overlapping relation with respect to the outer race 11 of the bearing and also secure the head 25 between the two stops 21 to prevent further rotation of fastener 19. The bearing race 11 again projects beyond the inboard wall 16. Further, tightening of the nut on the thread shank 25a moves the head 25 into a deflected bearing holding position as in the first embodiment.

The invention has few parts and the locking assembly is easily assembled in place and one of the main features is that the bearing locking assembly can be constructed after the motor has been completely assembled and it appears desirable that the bearing be locked in place around the motor shaft 3. The means of the locating the lock relative to the bearing and the means in which the bearing preload is applied and supported distinguish the bearing locking assembly over the prior art.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.