US1444825A - Centrifugal electrical switch - Google Patents

Description

Feb. 13, 1923. 1,444,825 c. P. BANZHOF CENTRIFUGAL ELECTRICAL SWITCH Filed May '7, 1919 2 shE ets-sheet 1 35390 1923. 1,444,825 C. P. BANZHOF CENTRIFUGAL ELECTRICAL SWITCH Filed May 7, 1919 2\\sheets-sheet 2 Patented Feb. 13, 1923.

UNITED STATES PATENT OFFICE.

CHARLES P. BANZHOF, OF LANCASTER, PENNSYLVANIA, ASSIGNOR OF THREE- ]EOURTHS TO THE FIDELITY ELECTRIC COMPANY, OF LANCASTER, PENNSYL- VANIA, A CORPORATION OF PENNSYLVANIA.

CENTRIFUGAL ELECTRICAL SWITCH.

Application filed May 7, 1919.

T all whom it may concern Be it known that 1, CHARLES P. BANZHOF, a citizen of the United States, residing at Lancaster, in the county of Lancaster and State of Pennsylvania, have invented certain new and useful Improvementsv in Centrifugal Electrical Switches; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention has for its object improvements in automatic starting switches for alternating current electric motors. It is more especially designed for use in connection with single phase motors which are to be started by the known method of phase displacement or so-called split phase method. However, it is not limited in its use to this particular application, but may be used in other connections as will be hereinafter pointed out. i

More specifically the invention embodles a centrifugal switch operating to quickly and positively open or close an electrical circuit at a definite predetermined speed of the rotating element to which it is attached, and to restore the circuit connections by a return to the starting position only after a reduction in speed of the rotating element shall. have been attained which. is relatively lower than that necessary to initially operate the switch.

A further object of the invention is to provide a centrifugal switch in which the timing or adjustment for operating at predetermined speeds is made independent of the current carrying members. The latter become worn or burned away by continued use, effecting a change in their weight, which changewould act to alter'the original timing adjustment of the switch, were these elements not separate from and independent of the switch operating means.

Vith these and other objects in view, a switch has been designed, which is of simple and sturdy construction, containin a minimum number of elements, and which will function with accuracy and precision for long periods of time without need of renewal or replacement of parts.

The invention will be described in connec Serial No. 295,326.

tion with the accompanying drawings formmg a part of this specification, and in which;

Fig 1 is an end elevation showing the application of the centrifugal switch to the rotor element of a split phase motor where it is necessary to open the circuit of the starting winding after the motor has de veloped the desired speed of rotation;

Fig. 2 is a view showing diagrammatically the motor circuit arrangements and their'relation to the switch forming the subject matter of this invention;

Fig. 3 shows an alternative arrangement of the switch as applied to alternating current motors of the types other than the split phase type, where it may be desirable to automatically either short circuit or connect together certain parts or portions of windings after a predetermined starting speed has been attained; and

Fig. 4.- is a perspective view of the apparatus as illustrated in Fig. 1.

In all the views the same reference characters are used to indicate the same or corresponding parts.

Referring now to Figs. 1 and 4, it will be seen that the current carrying members of the switch mechanism comprise fixed contact rings 8 and a corresponding number of contact fingers 1. arranged in the same vertical planes with the rings and so mounted as to make electrical contact with them when the switch is in its closed position. The rings 8 are of suitable conducting material and may be supported from a fixed part of the motor frame or casing. The contact fingers 1. are carried by or are integral with a sleeve member 2 rotatably mounted upon a stud or short shaft section 3, which latter is secured. to and rotates with the rotor element 11 of the motor. The fingers 1 are preferabl of resilient material and are provided at t eir ends with conducting shoes 14: rigidly secured to the lingers but insulated therefrom by interposed insulating material. When used as a starting switch for asplit phase motor, the conducting portions of the shoes 14 are connected by a conductor 16 as shown in Fig. 2, and with. the switch in this position the starting and working coils or windings of the stator element will be. connected in multiple, which is the desired connection produci for starting a motor of this type. To open the circuit oi the starting winding after the i'notor has been brought to the desired speed, it is only necessary to lift the tingers 1 from contact with the conducting rings 8 when the motor will continue to o ierate as a single phase motor. This is accomplished automatically by co-operation of the following mechanism. A spring finger 4 is secured to the inner end of the sleeve 2 and in the posi tion o the switch as illustrated in Fig. 1 e);- tends downwardly therefrom making an angle oi} substantially 90 with the contact fingers 1'. The lower end. oi the member 4: has the criniped portion 6 presenting a rounded surtace to be engaged by the end 7 the hook-shaped member 1'7, which in the full line position shown exerts pressure on the arm 4% to hold the contact-fingers l in engagement with the rings 8.

The hook-shaped member 17 is pivotally connected at one end to the rotor 11 upon a suitable support 12 and is held in restraint against outward movement by the spring 10 also carried by the rotor 11 upon a stud or boss 9; The movement of the member 17 is limited by an omer stop 1:; and an inner stop "which. is proiti-irably the axle oi? the rotor element ot the motor, since between the latter and the member I? there would be no relative movement to cause friction and consequent wear. The shape of 7l161116l11l361' l? is of in'iportancc :tor the proper functioning of this switch. it depends for its outward niovement to the dotted line position of Fig. 1 upon a component of centrifugal. force developed by the rotation oi" the rotor element ll. The center of this rotation is of course the center of the supporting); axle. Two forces initially oppose the outward JTiOV6- ment of the inen'iber y (me oi these being the spring 1.0 and the other a component of centrifugal force acting upon the mass of the end 7 of the said member 17 which at starting lies on the opposite side of the axis of rotation to that of the major portion of the member of which it is an integral part. ."issiuninn' a given tension for the spring 10 it will be seen that the mass of the end 7 will be the actor wh ch deter e time cor-- i A- speed which the will. be operated to open the starting;

circuit.

QU. w-.1d li ioreover. with movement aber I? started away from the corn 'otation. a portion of the mass which opposed this motion is added to that the motion, which acts to accelerate the L-OVQlIiGllt to the outer limit of its travel. in the closed position oi. the switch. l'l'iofend 7 oil; the hook-shaped member 17 b s against the end of the arm lto hold the switch in that position, but when the member 1? swings outwardly under the infiuence of centrifugal force. the contacting aims l of the switch will be free to respond e ia-s to centrifugal force ai'zting also on them and they will quickly move to the dotted line position of Fig. 1, thus brealcinr; the circuit of the starting winding.

The elements of the switch will remain. in the open position until the speed. of rotation oi the rotor is reduced to a point considerably lower than that at which the switch was opened. This is due to the fact that the center of gravity of the member 17 has been moved to a point a greater distance from the center of rotation than it is when the switch was moved to the open position. When returning to the closed position the outer curved surface oi? the end 7 engages the end oi: the arm l; and exerts sufiicient pressure thereon to positively close the switch by bringing the contact fingers 1 into engage inent with the conducting; rings 8. A wide difference in speed of rotation between the opening action. and closing action of the switch is a much desired feature of operation.

With very slight changes in structure, this switch may be used to short circuit starting resistances of motors or to connect together the rotor windingz s oi? a single or polyphase alternating current motor; after the speed of the same has been brought up to the desired point. in Fig. 3 the rotor windings terminate in the tired contact points or blocks of conducting material. which may be supported from the rotor element and in vertical planes coinciding with those of the conductin shoes carried by the contact arms 1. 11 this arrangement at starting, the windings of the rotor would be open circuited and when a predetermined speed of rotation had been attained. would be closed on themselves by connections with the shoes of contact fingers l. The timing cl'iaracteri stir: of the switch in this instance would be identical with that already described.

@ther applications or uses of a switch having these characteristics will beapparent and are within the scope of this invention.

Having thus described my invention, what i claim as new and desire to secure by Let tors Patent of the United i tates. is I l; lin a centril i switch the movable ments of which are m unted upon and car-- i motio the ried by a body capable of rota combination u h contacting? .1s secured to sleeve rotatably mounted on rod or stud projecting from the supphrting body.

lined contacts with which said errors are adapted to an operating arm so cured to said sleeve at a point axially displaced. along the sleeve from the contact arms. a switch controlling arm pivotally connected at one end to the supporting body, and on one side thereof opposite to that on which the movable contact arms of the within fixed limits, the hook end of the con trolling arm lying on the opposite side of the axis of rotation of the supporting body to that of the major portion of the mass of the controlling arm, the said hook end being adapted to engage and hold the operating arm of the switch element in one posi tion and to free said arm by movement to another position.

2. In a centrifugal switch, comprising fixed. contacts and movable switch. elements cooperating therewith to effect certain changes in electric circuits, the combination of a supporting body capable of rotary motion, a weight arm pivoted thereto which arm is so designed and supported that lin equal portions of its mass lie on opposite sides of the axis of rotation of the supporting body and a coiled restraining spring se cured to the supporting body and to the weight arm. a sleeve member also pivoted to the supporting body, a resilient arm secured to said sleeve the outer end thereof lying in the path oi? movement of the weight arm during a part of the movement of the latter, and one or more contact fingers also secured to said sleeve and so supported to make sliding contact with the fixed contacts of the switch and to be thrown out of engagement therewith. by centrifugal force when released by the Weight arm, substantially as described.

3. In a centrifugal switch comprising one or more fixed Contact rings and movable switch elements arranged to co-operate therewitl'i, the combination of a. rotary support, a weight arm pivoted thereon and re silient means connecting the weight arm and its rotary support, the said weight arm being so shaped that unequal portions of its mass may lie on opposite sides oi? the center of rotation of the rotary support, a sleeve also pivotally mounted upon the rotary support, a resilient arm secured to said sleeve and arranged for sliding engagement with the weight arm during: a portion of the movement of said arm, and another resilient arm secured to the sleeve which is provided on its outer end with a contact shoe for making electrical connection with the stationary contact ring, and adapted to be thrown out of engagement with the said ring by centrifugal force when released by the weight arm.

In testimony whereof I affix my signature 5 in the presence of two witnesses.

CHARLES P. BANZHOF. Witnesses:

JOHN F. HoR'rrNe, CHAS. F. STAUFFER.

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