Aug. 16, 1949. E. R. GOLDFELD 2,479,344 MOTOR BRAKING DEVICE Filed Oct. 26, 1944

INVENTOR. EDWIN RUSSELL 6oLDFELD BY A12 vulu Ayy70AMAY3. aLCLCu Aug up ov Z419,344 UNITED STATES PATENT office MOTOR BRAKNG DEVICE Edwin Russell Goldfield, University Heights, Ohio, assignor to Picker X-Ray Corporation Waite Manufacturing Division, Inc., Cleveland, Ohio, a corporation of..Ohio Application October 26, 1944, Serial No. 560,481 4 Claims. (C. 12-36) 1. 2 This invention relates to improved braking in Suitable bearings for rotation between pole means for electric motors. pieces and 2 which in the present embodiment An object of the present invention is to provide are shown of laminated construction. These poles a brake for the of an which are magnetized in the usual manner by means of is continuously urged toward braking position the fixed winding 3 which is energized by means and which is released by means of a magnetic not shown in the usual manner when current is which is attracted to an electromag - Supplied to the motor. The motor shown is pro netic pole piece of the motor whenever the same vided with shading coils 4 which rest in Suitable is magnetized. recesses or grooves 5 in the pole pieces. On the A particular application of my invention occurs upper end of the rotos shaft is fixed a, brake drum is connection with a shaded pole f6 which rotates with the rotor. The entire motor where the magnetic armature for releasing the is mounted on a base . brake is positioned adjacent the shading coil. The braking nearis is mounted or a bracket 8 A further modification of my invention occurs in fixed relation to the base and having an up in the provision of a shading ring on the magnetic 5 standing flange portio 3a, at the upper end of armature which is attracted to the electromag which two ears 82 are provided extending out netic pole piece for the purpose of releasing the Wardly at right angles to the flange portion. Lo lake. cated centially of the upper edge of the fiange Other objects and advantages of the present in portion is a tongue isc for Supporting a spring as vention and the details adopted in practicing my 20 later described. invention will be apparent from the accompany A level 9 is provided with notches 9d inter ing drawings and description, and the essential mediate is ends into which the ears 8ts extend features will be set forth in the accompanying to provide a fulcrum for the lever. The upper cians. end of the lever is provided with a korake shoe 9b In the drawings, 25 adjacent the otake drain it. The lower end of Fig. 3 is a perspective view of a Small moto the ever is provided with a magnetic airmature equipped with my in proved device, SSc secure to the leve" by the screws 29. The Fig. 2 is a fragmental sectional view taken ends of this airs natu3'e are bent inwardly as at 9d along the line 3-2 of Fig. ; to goints adjacent; the pole pieces and 2. A Fig. 3 is a view similar to Fig. 2 out showing the tongue S3e extends upwardly and outwardly from rake in released position; the bottom of the lever to a point opposite the Fig. 4 is a side elevational view of he device of Orague 38c. A small coil Spiring 2 is held in Sig. ; while te:sion between She tongues 8c azhd 3é. This Sig. 5 is a fragmental perspective yievy showing spring is positioned above the fulcrum of the Ore end of the ragnetic ariature of Sig. .. evei and therefore seives to continuously pull the The purpose of the present invention is too shce 9th against the drun 5. quickly stop he rotor of an electric motor when fi, iesuits from the above construction that, the energizing electric current is turred off. Un When current is Supplied to the winding 3 upor. eSS Such means is provided, the iraeria of the starting the motor, the pole pieces and 2 are rotor and the driven parts connected therewith is 40 ragnetized which in turn will attract the arma such that it will got coine to rest quickly enough ture 96 and release the brake shoe 9t) from the when the current is turned off and it is essential drum 6. This action takes place because of the in most applications that the speed of stopping high stray or leakage flux which exists around be accurately controlled. Braking devices are the pole pieces of the notor. This is particularly well known in which a rake shoe bears against 45 true in the locality of the shading coils 4 where Some part connected with the rotor at all times the flux is greater. T, therefore, prefer to posi when the motor is not energized. Then this tion the ends 9d of the magnetic armature ad brake is released usually by means of a solenoid jacent these shading coils as shown. which is energized simultaneously with the motor. For substantially reducing or eliminating chat My present improvement accomplishes the same 50 ter between the armature 9e and the pole pieces, purpose but without the use of a separate Solenoid. I may provide a shading ring 22 on the armature The drawings show my invention as applied to and at right angles to the plane of the shading a shaded pole induction motor of Small size and coils 4. As best seen in Figs. 1 and 5, the ends adapted to revolve at about 3,300 R. P. M. The 9d of the armature 9c are bifurcated, and the motor illustrated comprises a rotor 9 mounted SS shading ring 22 of copper or other suitable metal

2,479,844 3 4 is fixed to one of these bifurcated ends lef. The pieces, comprising a brake drum rotatable with shading rings 22 are positioned generally parallel said rotor and positioned laterally upon said pole to a plane passing through the rotor and pole pieces, a lever having a fulcrum intermediate its pieces. In this manner, an out-of-phase flux is ends, a brake shoe at one end of said lever posi provided which substantially reduces chatter of tioned adjacent said brake drum, a magnetic the armature during energization of the motor. armature at the other end of said lever, a shad In the above manner I have provided a very ing ring on Said armature and adjacent said efficient means for braking the rotor immediately shading Coll, said shading ring lying in a plane upon the deenergization of the motor including generally at right angles to the plane of said the coil 3 and have also provided very simple 0. shading coil, and Spring means urging said shoe means for releasing the brake immediately upon against said drum, said armature being adapted the energization of the coil f which is a stand when attracted by said pole piece and shading ard part of the motor shown and does not require coil to move said shoe away from said drum, any extra electrical devices. and Said shading ring being adapted to reduce What I claim is: s chatter. 1. Braking means for an electric motor hav 4. Braking means for an electric motor hav ing a rotor and electromagnetic pole pieces Sup ing a rotor and electromagnetic pole pieces com porting the field windings of said motor and said prising a brake drum rotatable with said rotor, motor having a shading coil on at least one of a brake shoe adjacent said drum, means urging said pole pieces, comprising a brake drum rotat 20 said brake against said drum, means for moving able with said rotor, a brake shoe adjacent Said said shoe away from said drum including a mag drum, means urging said brake against Said netic armature positioned adjacent at least one drum, and means for moving said shoe away of Said pole pieces, and a shading ring on said from said drum including a magnetic arrnature arnature opposite said one pole piece and ex positioned to receive the diverted 25 tending generally in a plane parallel to a plane by said shading coll. passing through said rotor and pole pieces, 2. Braking means for an electric anotor have whereby to Substantially reduce chatter of said ing a rotor and electromagnetic pole pieces Sup armature. porting the field windings of said motor and said DWN RUSSEL, GOLDFIELD. motor having a shading coll on at least one of 30 said pole pieces, comprising a brake drum rotat EFERENCES (CEEB) able with said rotor and positioned laterally upon The following references are of record in the said pole pieces, a lever having a fulcrum inter file of this patent: mediate its ends, a brake shoe at One end of said lever positioned adjacent said brake drum, a 35 UNITED STATES PATENTS magnetic armature at the other end of said lever Number Name late and positioned to receive the magnetic flux of 363,186 Thomson ------May 7, 1887 Said shading coil, and spring means urging said 728,974 Pott et al. ------May 26, 1903 shoe against Said drum, said armature being 1,005,857 Lindquist ------Cct. 17, 1911 adapted when attracted by said pole piece to A. 1437,421 Holliday ------Dec. 5, 1922 move said shoe away from Said drum. 518,020 Trever ------Dec. 2, 1924 3. Braking means for an electric motor hav 1,689,442 exa ------Oct. 30, 1928 ing a rotor and electromagnetic pole pieces and 1,768,950 Frank ------July 1, 1930 having a shading coil on at least one of said pole 1822,679 Stewart et al. ------Sept. 8, 1931