US1770113A - Electric motor - Google Patents

Description

July 8, 1930. w, STUMPF 1,770,113

ELECTRIC IOTOR Filed June 28, 1926 .2 Sheets-Sheet 1 July 8, 1930. w STUMPF 1,770,113

ELECTRIC .IOTOR Filed June 28. 1926 2 Sheets-Sheet 2 ZZZ Patented July 8, 1930 UNITED STATES PATENT o1=1=1c1-:

WALTR STUHPI', OI BALTIMORE COUNTY, MARYLAND, ASSIGNOR TO THE BLACK & DECKER MANUFACTURING COMPANY, OF TOWSON, MARYLAND, A CORPORATION 01 IARYLAN D ELECTRIC MOTOR Application filed June 28,

In themanufacture of portable electric tools the expense incident to machming the same with a sufficient degree of accuracy torovide for the positioning of the armature Bearings, which, on account of the high speeds attained, must be practically frlctionless andftherefore, located, and aligned with exactness, has been an important item. It has also been difficult to provide for taking up the wear in the bearings resulting in both end play and side play. To overcome the difficulty thus encountered one of the bearings is mounted to slide in the direction of the axis, the wear and plati bein taken up by a spring which presses e sli ing bearing toward the fixed bearing, prefera ly acting on the outer race. g

The present invention relates to the ositioning means and also to various detai s of the means for positioning the bearing and taking up the play as aforesaid.

An important ditnculty has been due to the tendency of the service men in re-assembling after removing the armature to leave out parts of the bearing supporting and pos1- tionin elements, which ordinarily drop out with t e shaft. A feature of the invention relates to securing the spring to the spring cup or washer or to both the cup and the housing so that in the first instance the spring cannot be easily removed from the cup and 'the combined parts are not apt to be overlooked, and in the second instance neither the s ring nor the cup can be easily removed from tile casing or housing.

In the accompanying drawings I have illustrated so much of a portable rotary electric tool of the drill type as is considered necessary to a full comprehension of my invention and the manner of applying the same. I

In the drawings:

Figure 1 is a vertical central section of a portable electric tool, the handle being shown in elevation and the s indle and lower portion of the gear casing ing broken away for convenience of illustration.

Figure 2 is an elevation of the spindle and lower portion of the gear casing below the broken line in Figure 1. 1-

Figure 3 is a section taken on the line of the 1926. Serial No. 118,971.

axis through the rear or upper motor bearing and adjacent portion of the motor housing.

Figure 4 is an end elevation or top plan of the same looking from the right in F igure 3.

Figure 5 is an axial section through the spring cup and spring.

Figure 6 is a view of the the right in Figure 5.

Referring to the. drawings by numerals, each of which is used to indicate the same or similar parts in the different figures, the illustration includes an electric drill or similar portable rotary electric tool 1, comprising a motor housing 2 enclosing motor 3 and having rigidly connected thereto at one end a handle 4 and at the other end gear casing 5 enclosing reducin gearing 6 by means of which the spindle is rotatlvely connected to and driven by and from the motor 3. The motor is provided with a rotating armature 9 mounted on a shaft 10 rotating in a fixed bearing 11 located by shoulder 12 at one end, and at the other end in a bearing 14 mounted in a suitable recess or chamber 15 formed in the end of the housing for this purpose, the said bearing having a sliding relation with said housing, or more particularly the bushing 16 therein which carries the outer race 17 of the hearing, which is shown as a ball bearing. The inner race 18 is secured to the shaft, being either pressed or sWeated on the shaft and the tendency to end play of the shaft and to similar motion in the axial direction of the bearing is taken up by means of a spring 19 which, as shown, is a spiral spring, bearing at one end on the end or rear wall 20 of the chamber 15 and in the other direction on the bottom of the spring cup 21 which preferably engages the outer race 17 of the open ended bearing shown. Neither the ty e of bearing nor the exact arrangement (i;- scribed is essential to the broadest conception of the invention.

It is obvious that the inner race bein grooved at '22 to receive the balls 24 andthe inner race itself being secured to the shaft, theouter race being grooved at 25 on the outer or upper side of same looking from the balls, the end play is conveniently taken likewise shouldered or a up by the spring pressure against the outer race.

Where an open bearing is used, as in the form illustrated, the outer race is made with a cylindrical surface 26 which extends toward the lower or inner end of the bearing for a very short distance which may be conveniently about one millimeter. This provides for a slight degree of motion of the outer race relatively to the rest of the bearing with out injury to the bearing. The motion of the outer race is limited to the length of the cylindrical surface 26 just described by the formation and placing of the cup 21. The cup being formed by ashort peripheral or cylindrical flange 27 at the edge of the washer or disk 28, the outer or open edge of this flange or rim 29 is spaced, in accordance to the preferred dimensions of the parts, from the rear wall 20 of the cavity or chamber which receives the bearing by an interval 31 slightly less than the short cylindrical surface 26. The motion of the cup 21 under these circumstances corresponds but is slightly less than the extreme upward or backward motion of the outer race, which is permissible without injuryto the parts. It is to be understood, however, that the exact type of bearing is not regarded as'an essential feature of the invention in its broader conception, as herein described and claimed.

A difliculty encountered in connection with the operation and maintenance of such tools is the tendency of the service man to mislay and leave out in reassembling various arts which he may regard as non-essential. Vith the spring take-up, the spring is not infrequently omitted on reassembling, with a consequent increased play of the armature and shaft, and a tendency to increased wear, noise, difficulty and even uncertainty of operation.

One of the objects of the present invention is to decrease the tendency to omit the spring in assembling the tool. To this end the cup 21 is provided with an offset or a plurality of staked edge portions 33, see Figure 6, which project from the outer edges 29 inwardly toward the center of the cup and take over the base or outer coil of the spring and tend to prevent the removal of the spring from the cup without the exertion of considerable'efdial play due to wear of this bearing and the upper or rear bearing are taken up by the spring take-up described. The manner of assembling and operation are obvious from the description and drawings.

In the form shown in Figure l, the bearing is closed by a washer 45 on the inside, i. e., between the armature and the bearing. This washer, in the form shown, bears at one side against the inner race, the other side of the washer engaging in the case of the sliding bearing a shoulder 46 on the shaft and in the case of the stationary bearing the fan hub 47.

In Figure 3, two washers, one a small washer 48 which encircles the shaft just inside the end of the inner race and bearing against the same serves to limit the motion of the balls relative to the outer race and a a second larger washer 49. which positions the inner washer 48, are substituted for the washers 45 in Figure 1.

I have thus described specifically and in detail a single embodiment of my invention in order that the nature and operation of the same may be clearly understood, however, the specific terms herein are used descriptively rather than in a limiting sense, the scope of the invention being defined in the claim.

What I claim as new and desire to secure by Letters Patent is:

A takeup for the ball bearings of an electric motor having a casing with a bearing housing, the takeup comprising a spiral spring, a cup enclosing and secured to the coil at the large end of the spring and a stud securing the coil at the small end of the spring to the bearing housing.

Signed by me at Baltimore, Maryland, this 22 day of June 1926.

WALTER STUMPF.

fort. The structure may be further im-' proved, and the tendency to removal of the spring which results in its being left out when the tool is assembled, overcome, by riveting the center or forward or upper coil 34.- of the spiral spring 19 to the center of the rear or top wall 35 of the cavity or chamber 15 in which the bearing is seated. The rivet is indicated by reference character 36, and for convenience in setting the rivet the cup 21 has a central aperture 37 in the bottom to admit a riveting tool. The lower or forward bearing 40 is seated in the bushing '41 in the

Images