US2991340A

US2991340A - Switch mounting for rotating equipment

Info

Publication number: US2991340A
Application number: US798482A
Authority: US
Inventors: Abraham S Bickham
Original assignee: AO Smith Corp
Current assignee: AO Smith Corp
Priority date: 1959-03-10
Filing date: 1959-03-10
Publication date: 1961-07-04
Anticipated expiration: 1978-07-04

Description

y 1961 A. s. BICKHAM 0 SWITCH MOUNTING FOR ROTATING EQUIPMENT Filed March 10, 1959 INVENTOR.

ABRAHAM 5510mm United States Patent 2,991,340 7 SWITCH MOUNTING FOR ROTATING EQUIPMENT Abraham S. Biekham, Dayton, Ohio, assignor to A. 0. Smith Corporation, Milwaukee, Wis., a corporation of New York Filed Mar. 10, 1959, Ser. No. 798,482 7 Claims. (Cl. 200-80) This invention relates to a switch mounting for rotating equipment and particularly relates to a mounting bracket for a centrifugal switch in a single phase motor or the like.

Single phase induction motors are normally wound with a running winding and a starting winding which is connected in circuit only during initial starting of the motor. The circuit of the starting winding includes a centrifugally actuated switch having contacts biased to an open position. A centrifugal snap-action actuator is secured to the motor shaft immediately adjacent to the centrifugaily actuated switch and biased to hold the centrifugal switch contacts closed. As the speed of the motor increases, the centrifugal force applied to the actuator increases accordingly and when running speed is approached or attained, the actuator operates to open the switch contacts and disconnect the starting winding from the circuit.

The centrifugally actuated switch must be accurately positioned with respect to the actuator to establish disconnection of the starting winding at a predetermined speed. Further, the centrifugal switch must be so mounted as to allow continued predetermined switch operation in the presence of severe motor vibration and the like.

In accordance with the present invention, a mounting bracket assembly having a resilient arm rigidly joined to a base support is rigidly secured to the frame supporting the rotating shaft. A centrifugally actuated switch is secured to the resilient bracket arm. A positioning rod located closely adjacent to the bracket end is releasably connected to a portion of the frame and the bracket arm. The positioning rod engages the switch carrying arm closely adjacent to the bracket end and bends the aim to accurately position the switch which is mounted thereon. The mounting of the adjustment rod closely adjacent to the bending point of the bracket requires high bending forces in the positioning of the switch carrying arm. The high bending forces allow accurate positioning of the centrifugally operated switch and substantially eliminate any loosening movement of the adjustment rod due to motor or machine vibration that is transmitted to the mounting bracket assembly.

The mounting bracket assembly is most simply and readily fabricated in the form of a U-shaped member of suitable steel. Suitable openings are provided in the arms of the member closely adjacent the bracket end. An adjustment rod extends through the openings and is releasably threaded into a suitably tapped opening in the shaft supporting frame or the like.

The mounting apparatus of the present invention provides a rugged, reliable support for a centrifugally actuated switch and the like which allows ready and accurate location of the switch with respect to the centrifugal actuator. The simplicity of the mounting assembly makes the switch mounting readily adapted to mass production and relatively economical to fabricate.

The drawing furnished herewith illustrates the best mode presently contemplated for carrying out the invention.

In the drawing:

FIGURE 1 is an elevational view of a motor with parts broken away to show the starting switch construction;

FIGURE 2 is a fragmentary end view of the motor taken on line 22 of FIGURE 1; and

FIGURE 3 is a side view of the electric switch.

FIGURE 4 is a perspective view of the mounting bracket employed in FIGURES l and 2.

Referring to the drawings and particularly to FIGURE 1, a single phase motor is shown incorporating a tubular frame 1 which is closed at one end by an end bell 2, and cover 3, as shown to the left in FIGURE 1, and an end hell 4, as shown to the right in FIGURE 1. A plurality of circumferentially arranged thru bolts 5 extend through the aligned

end bells

2 and 4 and the tubular frame 1 to securely clamp the units together. A stator 6 is sup ported within the tubular frame 1 between the

end bells

2 and 4 and carries the conventional start and running winding shown diagrammatically at 7. A rotor 8 is coaxially mounted within the stator 6 and rotatably supported by a rotor shaft 9 which is journalled within the

opposite end bells

2 and 4.

The rotor 8 is a conventional squirrel-cage variety rotor which, upon suitable energization of the stator winding 7 rotates and establishes a mechanical power output at the extension of shaft 9, shown to the right in FIG- URE 1.

The end hell 2 is generally cup-shaped and opens axially outwardly of the frame 1. The base portion 10' of the end bell 2 extends radially inwardly and terminates in a central bearing assembly 11. The shaft 9 is journaled within the bearing assembly and terminates immediately within the cup-shaped bell member 2.

A switch actuator 12 is mounted on the extended end of shaft 9 within the end bell 2 and controls the opening and closing of contacts of a switch 13 which is rigidly mounted adjacent the actuator 12.

The switch actuator 12 includes a generally channelshaped support bracket 14 which is rigidly secured by a screw 15 to the end of shaft 9. The screw 15 extends through an opening in bracket 14- and threads into a suitably tapped opening in the end of the shaft 9.

A generally T-shaped operating weight assembly 16 is disposed between the arms of bracket 14 and is pivotally supported by a pair of pivot arms 17 on the cross arm portion of the member and aligned openings in the arms of bracket 14. The weight assembly 16 is pivotally supported on bracket 14 off center with respect to the shaft 8 whereby centrifugal force resulting from the rotation of the shaft 8 causes the T-shaped weight assembly 16 to pivot on the arms 17. Projections 18 extend laterally from opposite sides of the member 16 and receive a hook end of a pair of coil springs 19 disposed on opposite sides of bracket 14. The coil springs 19 extend across the axis of the shaft 9 and are pivotally secured at their opposite ends by suitable hooks in holes 20 in formed extensions of the lower end of the arms of the channel shaped bracket 14. The coil springs 19 bias the cross arm portion of the T-shaped weight assembly 16 into stop engagement with the adjacent upper end of the bracket 14. The extending stem portion of the weight assembly 16 is disposed axially outwardly of the bracket 14 and terminates in a semi-spherical nib 21, its center lying in line with the axis of the shaft 9. The nib 21 is biased axially outwardly into operative engagement with the centrifugally operated switch 13 to normally hold the switch closed until the shaft is rotating at a preselected speed. The extension hole 20 is positioned intermediate the. pivot connection pin 17 and the normal stop position of projection 18. As the weight assembly 16 starts to pivot, the spring tension increases at a given rate and the moment arm between the center line of the spring and Patented July 4, 1961 the pivot point decreases. The resulting moment to return the weight assembly 16 to its normal position increases at a lesser rate than the moment produced by centrifugal force on the weight assembly 16 as a result of the latter moving out to an increased radius. Thus, when the weight assembly 16 begins to move outwardly, it goes all the way with a snap action.

Referring particularly to FIGURE 2, the centrifugally actuated switch 13 includes a pair of

unformed leaf springs

22 and 23 which are riveted as by rivets 24 or otherwise rigidly secure at one end to space surfaces on a mounting plate 25. The

leaf springs

22 and 23 are generally arranged to form an inverted V-shaped configuration having an overlap at the apex of the V-shaped configuration. Suitably shaped electrical contacts 26 are secured to the opposed surfaces of the overlapped portion of the

leaf springs

22 and 23.

The mounting plate 25 is adjustably secured to an enlarged wall portion 27 of the base of end bell 2 by a U-shaped mounting bracket 28. The plate 25 is made of a fibrous material or other suitably insulating material to electrically insulate the

leaf springs

22 and 23 when the contacts 26 are open.

Referring particularly to FIGURES l and 3, the

unformed leaf springs

22 and 23 are. tensioned by the shaped surfaces of the mounting plate 25 against which they rest to hold the contacts 26 in spaced relation, as shown in phantom in FIGURE 3.

The leaf spring 22 extends generally radial-1y over the upper end of plate 25 and in front of the nib 21 of the T-shaped weight assembly 16. A button 29 is secured to the free end of leaf spring 22 and is selectively engaged by the nib 21 to open and close the contacts 26. The outward bending of the

leaf springs

22 and 23 is limited by a rigid backing member 30 superimposed upon spring 23.

Suitable leads 31 are secured to the lower end of

springs

22 and 23 and are extended through a close fitting grommet, not shown, located in a hole, not shown, in the base 10 of end bell 2 and into the motor frame for correction in the circuit. The leads are suitably connected in circuit with the starting winding portion of stator winding 7 to selectively connect and disconnect the starting winding and auxiliary components to the power supply line, not shown.

In accordance with the illustrated embodiment of the present invention the centrifugal switch 113 is rigidly, adjustably supported with respect to the actuator 12 by relative closing and opening of the U-shaped bracket 28.

Referring particularly to FIGURES l and 4, one arm 32 of the U-shaped bracket 28 is secured to wall 27 of the end bell 2. A screw 33 extends through 34 an opening in the outer portion of arm 32 and threads into a correspondingly tapped opening in the wall 27. The second arm 35 of bracket 28 is integrally joined to the arm. 32 by the bracket back 36 which is so proportioned as to generally align the second arm 35 axially outwardly of the switch actuator 12 by a small distance where the switch is mounted thereon. A small screw 37 extends through an opening in the. mounting plate and threads into a correspondingly tapped aperture 38 in the outer end of arm 35 to secure the mounting plate 25 to the exterior surface of the arm 35. A switch positioning screw 39 extends through aligned openings 41), 41, and 42 in the mounting plate 25 and the

bracket arms

35 and 32 immediately adjacent the base 36 of bracket 28. The positioning screw 39 threads into a suitably tapped opening 43 in the supporting wall portion 27 of the end hell 2. A lock washer 44 is disposed between the head of positioning screw 39 and mounting plate 25 to help maintain the screw 39 in the position to which it is set.

The adjustment screw 39 is adapted to bend the forward arm 35 of the U-shaped bracket 23 axially of the motor to accurately position the centrifugally actuated switch 13 with respect to the actuator 12. The illustrated bracket 28 is formed of any suitable metal such that the junction of the arm 35 to the base 36 constitutes a resilient joint or connection permitting the. described bending of arm 35. The adjustment screw 39 is disposed immediately adjacent the back 36 of the U-shaped bracket 28 and relatively large bending forces are required in positioning of the arm 35 and the attached centrifugally actuated switch 13. Consequently, the switch 13 may be very accurately located with respect to the actuator 12. The high bending forces or stresses established in bracket 23 in positioning of the switch 13 substantially eliminate loosening of the adjustment screw and attendant dislocation of the switch 13 because of vibrations which may be present in applications on which the motor is used.

In assembly, the mounting bracket 28 is secured to wall 27 by the screw .33 and the actuator 12 is secured to the end of shaft 9 by the screw 15. The switch 13 is secured to the forward arm 35 of bracket 28 by screw 37 with the plate aperture aligned with the

apertures

41 and 42 of the mounting bracket 28. The switch adjustment screw 39 is inserted through the aligned openings 4042 and threaded into tapped opening 43 to position the

leaf springs

22 and 23 for automatic opening and closing of the contacts 26 in response to predetermined speeds of the motor. To position the switch 13, the shaft is slowly rotated and the weight assembly manually held in the actuated position, as shown in phantom in FIG- URE l. The switch adjustment screw 39 is then turned to position switch 13 with the switch button 29 just clearing the weight assembly nib 21. The leads 31 are connected to the outer end of the

respective leaf springs

22 and 23 to serially connect the contacts 26 in circuit with the starting circuit portion of stator winding 7. The contacts 26 are held closed to supply current to the starting winding portion during the initial energization of the winding 7.

When the motor is energized, the rotor 8 and shaft 9 accelerate to running speed. The centrifugal force on the T-shaped weight assembly 16 biases it to the open position for the switch 13, as shown in phantom in FIG- URE 1. The weight assembly 16 moves toward the open position until it engages the bracket 14 which serves as a stop member. The tension in

springs

22 and 23 holds contacts 26 closed during this initial movement of the weight assembly 16. The continued snap-action movement of the weight assembly 16 moves the nib 21 axially inwardly of the mounting plate 25 and allows the

leaf springs

22 and 23 to move to the biased open posi tion, as shown in phantom in FIGURE 1. The contacts 26 open and disconnect the starting winding portion of stator winding 7 from the circuit.

The speed of rotation of the motor at which the T- shaped weight assembly :16 of actuator 13 snaps to the open contact position of switch 12 is synchronized with the operating speed of the motor at which the starting winding is no longer necessary.

The present invention thus provides a simple, reliable and rugged mounting for adjustably positioning and holding centrifugally actuated switch in a dynamo-electric machine and the like where severe vibrations may be encountered in operation.

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

I claim:

1. In an apparatus having a rotating shaft carrying a centrifugal actuator and having a centrifugally actuated switch adapted to be opcratively mounted adjacent the centrifugal actuator, a spring bracket assembly secured to a relatively stationary portion of the apparatus and having a rigid leg resiliently secured to a support member, means to secure the centrifugal switch to the rigid leg of the bracket assembly, and adjustable means operatively engaging the leg carrying said switch closely adjacent the bending point of the leg and adapted to position the rigid leg relative to the support member to selectively position the switch with respect to the actuator.

2. In a dynamoelectric machine and the like having a rotating shaft carrying a centrifugal actuator and having a centrifugally actuated switch adapted to be operatively mounted adjacent the actuator, a support bracket adapted to be secured to a supporting wall portion for the shaft and having a base extending from the wall portion generally parallel to the motor shaft and having an integral leg extending laterally of the base, said base and integral leg being formed from a resilient metal, means to rigidly secure the centrifugal switch to the integral leg, and adjustable rod means extending between the integral leg and the wall portion closely adjacent the base to angularly position the integral leg with respect to the base and thereby position the attached switch with respect to the centrifugal actuator.

3. In a dynamoelectric machine and the like having a rotating shaft carrying a centrifugal actuator including a movable operating member and having a centrifugally actuated switch adapted to be operatively mounted in the path of the operating member, a generally channelshaped resilient bracket having one spring arm secured to a stationary portion of the motor and a second spring arm flexibly mounted in axially aligned relation with said actuator, said latter spring arm being flexible in the direction of movement of the operating member of the actuator, means to rigidly secure the switch to the second spring arm of the bracket, and adjustable means operatively engaging the second spring arm immediately adjacent the base of the channel-shaped bracket to position the second spring arm and thereby selectively position the switch with respect to the operating member of said actuator.

4. In a dynamoelectric machine and the like having a rotating shaft carrying a centrifugally moved snap-action member and having a centrifugally actuated switch adapted to be operatively mounted adjacent the snapaction member, a generally channel-shaped integralbracket of a resilient metal and having the first leg secured against a wall portion of the motor and the second leg in generally radially spaced and axially aligned relation to the snap-action member, means to secure the switch to the outer portion of the second leg of the bracket, and rod means extending through the first leg into engagement with the second leg closely adjacent the base of the U-shaped bracket and adjustably secured within the wall portion to selectively position the second leg and the switch relative to said snap-action member.

5. In a dynamoelectric machine having an enclosing casing and a shaft extending through one end of the casing, an actuator secured to the end of the shaft and having an operating portion axially movable between a first and a second position incident to operation of the dynamoelectric machine, a switch having a movable contact member adapted to open and close the switch, a chamelshaped mounting bracket of resilient steel having a pair of arms joined by a web portion, means to rigidly attach the switch to the outer end portion of one of said arms, means to rigidly attach the outer end portion of the other bracket arm to the exterior of said casing adjacent said shaft to dispose said movable contact member of said switch in the path of said operating portion of the actuator, and an adjustment rod extending through aligned openings in the arms of the bracket and coupled to the arm carrying the switch and releasably adjustably secured to the casing to permit selective bending of the switch carrying bracket arm for precision movement of said switch relative to said actuator.

6. In a dynamoelectric machine having a tubular housing and having a two-piece assembly closing one end of the housing and forming a separate chamber and having a shaft terminating in the chamber journaled within said assembly, an actuator disposed within the chamber and secured to the end of the shaft and having an operating portion axially movable between a first and a second position incident to operation of the dynamoelectric machine, a switch having a movable contact member adapted to open and close the switch, a channel-shaped mounting bracket of spring steel having a first and second arm joined by a web portion, means to rigidly attach the switch to the outer end portion of the first arm, means to rigidly attach the outer end portion of the second arm to a radial wall portion on the innermost member of the two-piece assembly, said web portion extending parallel to the motor shaft and terminating in generally axial alignment with said shaft to dispose said movable contact member in the path of the operating portion of the actuator, and an adjustment screw extending through aligned openings in the arms of the bracket adjacent the web portion of the bracket and threaded into a correspondingly tapped opening in the wall portion to selectively open and close the mounting bracket and thereby precisely locate said switch relative to said actuator.

7. In a single phase motor having a tubular frame carrying an annular stator winding and having a rotor and attached shaft coaxially disposed within the tubular frame, an end bearing member secured to one end of the frame and having a central bearing to support said shaft, a centrifugal actuator secured to the end of the shaft adjacent the end bearing member and having an operating member adapted to move axially outwardly, a centrifugal switch having a mounting plate, a channel shaped bracket having spaced arms integrally joined by a web portion, a continuous solid radially extending wall portion on the exterior side of said end member corresponding generally to a first of said spaced arms, means rigidly securing the upper portion of the first spaced arm to the wall portion, means rigidly securing the central portion of the mounting place to the upper portion of the second spaced arm, said mounting plate and bracket arms having aligned openings adjacent the bracket web portion, said wall having a tapped aperture aligned with said openings, and an adjustment screw extending through said aligned openings and threaded into said tapped aperture, said adjustment screw having a bearing surface engaging the mounting plate to adjustably secure said centrifugal switch in position relative to said operating member.

Taylor Jan. 30, 1940 Haines Jan. 20, 1959