Fannin, Wayne V. (Dayton, OH)
Halsted, Edwin H. (Dayton, OH)
This invention relates to centrifugally actuated switches and more specifically to an improved centrifugal switch assembly for electric motors controlling a starting circuit therein.
Centrifugally actuated switches are commonly employed in single phase AC induction motors which are used in industrial and household devices including appliances such as, clothes washers and dyers, dishwashers, garbage disposals, etc. These motors typically include a main winding and a starting winding which are energized when the motor is turned on. A centrifugal switch mechanism disconnects a starting winding when the motor has reached a predetermined speed and it is no longer desirable to maintain the starting winding energized.
Among the significant features of centrifugal switch mechanisms are the mounting arrangements and utilization of space within the motor housing without changing the size or shape of the electric motor. It is particularly desirable that the centrifugal switch assembly include a minimum of components so that the switch is reliable, easily assembled, and is readily serviceable so that the switch mechanism can be easily manufactured and assembled in the motor housing.
In accordance with the present invention, a centrifugally actuated motor switch assembly includes a support member containing a centrally disposed aperture for concentrically positioning it upon the motor shaft and it includes diametrically opposed axially extending flanges. The axially extending flanges contain guide slots receiving guide members on a basket shaped switch actuator which is slidably mounted relative to the support member and is also concentrically positioned on the motor shaft. A conical coil spring likewise is concentrically positioned on the motor shaft between the support member and the switch actuator normally biasing the switch actuator outwardly of the support member.
A pair of conductive leaf spring switch arms are rigidly secured in an insulating block attached to the motor housing. The switch arms have aligned contacts secured thereon and are normally biased open by their inherent spring characteristics. The basket shaped switch actuator includes a circumferential radially extending flange at its outer periphery terminating in an annular switch actuating rim. The coil spring between the support member and the switch actuator normally biases the rim into engagement with the leaf spring arms retaining the contacts in engagement normally closing the starting circuit. A pair of weight members include a pair of spaced arcuate fingers engaging supporting shoulders on the basket shaped switch actuator. They also engage spaced axially extending mounting lugs on the support member flanges pivotally supporting the weights in the assembly. The weight members are responsive to centrifugal force and pivot upon the support member flanges depressing the basket shaped switch actuator against the force of the coil spring moving the annular ring out of engagement with the leaf spring arms and opening the starting circuit when the motor reaches a predetermined speed.
Accordingly, a primary object of this invention is the provision of an improved centrifugal switch assembly for an electric motor that is compactly mounted internally of the motor in a manner requiring a minimum of housing space.
Another object of this invention is the provision of a centrifugal switch actuator assembly for an electric motor wherein the actuator assembly is mounted concentrically about the motor shaft inwardly of the usual lubricating assembly provided in the area where the shaft is rotatably mounted in the motor housing, the actuator assembly including a basket shaped actuator guided and slidably mounted within a support member for positive actuation in response to centrifugal forces whereby it opens a starting circuit when the motor attains a predetermined speed.
A further object of this invention is the provision of a centrifugally responsive switch actuator assembly within a motor housing positioned concentrically upon the motor shaft axially between the rotor and a lubricating oil well assembly in the motor housing so as to take advantage of available space without increasing the axial length of the motor housing, the actuator assembly including a support member having diametrically opposed axially extending flanges containing guide slots receiving guide lugs on a basket shaped switch actuating member normally spring biased to close contacts on leaf spring switch members, and a pair of weights being pivotally mounted in the support member flanges in engagement with the switch actuating member, the weights moving radially outwardly in response to motor speed thereby moving the switch actuator inwardly within the support member, opening the switch contacts and consequently the starting circuit when the motor attains a predetermined speed.
The novel features which we believe to be characteristic of our invention are set forth with particularity in the appended claims. Our invention itself, however, both as to its organization and method of operation, may be best understood by reference to the following description taken in connection with the accompanying drawings in which:
FIG. 1 is a side elevational sectional view of an electric motor employing a centrifugal switch actuating assembly in accordance with the present invention.
FIG. 2 is an exploded perspective view illustrating the components of our centrifugal switch actuating assembly in aligned positions removed from the electric motor.
FIG. 3 is a fragmentary sectional view taken on line 3--3 of the switch actuator shown in FIG. 2 with the remaining components in assembled relationship illustrating the switch actuating mechanism in a centrifugal force operated position.
FIG. 4 illustrates an electrical schematic diagram including the switch contacts actuated by our centrifugal force responsive mechanism.
Referring now to FIG. 1, an electric motor 10 of a single phase AC induction motor type includes a motor housing 12, a stator 14, and a rotor 16 affixed to a shaft 18 for rotation therewith. The stator 14 is supported within housing 12 and includes a stator winding 20 comprising a main winding 22 and a starting winding 24 shown schematically in FIG. 4. The motor housing 12 is substantially cylindrical in form and includes end frames 26 and 28 enclosing opposite ends thereof. The end frames 26 and 28 include annular bearing supports 30 and 32 which contain bearing assemblies 34 and 36, respectively. The shaft 18 includes a forward portion 38 rotatably supported in bearing 34 which provides an output driving connection for the motor 10 while a rearward portion 40 of the motor shaft 18 is supported by bearing 36. In a preferred embodiment, the shaft 18 is vertically disposed although, of course, the shaft can be disposed horizontally without departing from the principal features of the present invention.
The rotor 16 includes a plurality of squirrel cage bars, not shown, which extend through the rotor and electrically connect with a pair of end rings 42 and 44 disposed on opposite ends of the rotor 16. The end rings 42 and 44 can be made of a cast aluminum or other suitable conductive material and electrically interconnect with the squirrel cage bars, as previously indicated, in a well known manner. The end rings 42 and 44 have fan blades 46 cast integrally therewith for circulating air through the interior of housing 12 as the shaft 18 rotates. The fan blades 46 extend axially from the end rings 42 and 44 and are circumferentially spaced so that open spaces between the blades are formed radially of the shaft 18.
The annular bearing supports 30 and 32 define cavities 48 and 50 each containing a quantity of porous material 52 impregnated with a lubricant so as to effectively lubricate the shaft 18 in the areas of bearings 34 and 36 during operation of the motor. The cavities 48 and 50 are substantially enclosed at the interior end thereof by thrust washers 54 secured to the annular bearing supports 30 and 32 and extending into engagement with the outward side of annular flanges 56 attached to the shaft 18.
A centrifugal switch actuating assembly 58, constructed in accordance with my invention, is positioned between the rotor 16 and the annular flange 56 near the driving end 38 of shaft 18. The switch actuating assembly 58 includes a support member 60 containing a central aperture 62 defined by an annular flange 64 which provides for the concentric positioning of the support 60 upon shaft 18 adjacent rotor 16 in engagement with end ring 42. The annular flange 64 has an inner surface engaging a splined surface 19 on shaft 18 providing a driving connection therebetween. The support member 60 includes diametrically oppositely positioned axially extending flanges 66 which terminate in radially extending flanges 68 being deformed to include vertically extending lugs 70 as is best illustrated in FIG. 2. The support member 60 contains an annular depression 72 receiving one end of a conically shaped coil spring 74. The axially extending flanges 66 each contain a centrally positioned slot 76 for a purpose to be later described.
A switch actuator 78 substantially in the form of a basket includes a bottom portion 80 and an upper annular switch actuating rim 82 connected with the bottom member via a plurality of struts 84. The switch actuator 78 also includes diametrically opposed vertical walls 86 which connect with bottom surface 80 via an integral extended portion 88 and connect with the switch actuating rim 82 by means of an integral radially extending flange 90. The vertical walls 86 are cut away to provide rounded shoulders 92 on either side of the vertical wall as is specifically illustrated in FIG. 2.
A pair of centrifugal force responsive weights 94 include spaced arcuate fingers 96 at either end of the top edge defining a notch therebetween. The axially extending flanges 66 of the support member 60 are of a width sufficient to permit positioning of the arcuate fingers 96 of weights 94 on either side thereof adjacent the vertically extending lugs 70. Likewise, the vertical wall 86 of the basket switch actuator 78 is of a width sufficient to permit positioning of the arcuate fingers 96 upon rounded shoulders 92 so that in an assembled relationship the weights 94 are operative to pivot relative to the support member 60 and move the switch actuator 78 against the force of spring 74 as will be later described with respect to operation of our improved centrifugal switch actuating mechanism.
The motor housing 12 has an insulating block 100 secured thereto by means of a rivet 102, shown in FIG. 1. The insulating block 100 is notched at 104 and 106 and leaf spring switch actuating members 108 and 110 are respectively secured therein as best shown in FIG. 2. The leaf spring members 108 and 110 have contacts 112 and 114 secured thereon in axial alignment for engagement in a switch closed position. The switch actuating arms 108 and 110 are connected in series electric circuitry with one power line 23 and the starter winding 24, as schematically illustrated in FIG. 4.
The basket switch actuator 78 includes integral axially extending guide lugs 116 extending outwardly of the vertical walls 86 which are slidably received within notches 76 in the axial extending flanges 66 of support member 60. This arrangement provides for sliding movement of the basket member 78 relative to the support member 60 as influenced by the coil biasing spring 74 while preventing relative rotation between support 60 and actuator 78. As previously mentioned, the annular flange 64 of the support member 60 includes an inner surface engaging the splined surface 19 formed upon the shaft 18 drivingly connecting the support 60 with shaft 18. In this manner the shaft 18 is effective to rotate the support member 60 while the guide members 116 residing in slots 76 provide a driving connection between the support member and the basket member 78 so that it is positively rotated with rotor 16 during operation of the motor. This arrangement is necessary to retain the switch actuator assembly in a fixed angular position out of interference with the cooling fan blades 46 on the end ring 42.
In operation, with the motor in a static condition or in a low speed initial operating condition, the coil spring 74 is effective to maintain the basket switch actuator 78 in an extended position moving contact 114 into engagement with contact 112 maintaining the circuit through starting winding 24 closed. The extended movement of the basket switch actuator 78 is limited by engagement of rounded shoulders 92 of the basket switch actuator 78 with arcuate portions 96 of weights 94 which in turn has the top edge of notch 98 in engagement with the radially extending flanges 68 of support member 60, as illustrated in FIG. 1. When the motor attains a predetermined speed, the weights 94 pivot radially outwardly with the arcuate portions 96 remaining in engagement with the vertically extending lugs 70 while simultaneously continually engaging rounded shoulders 92 on vertical wall 86 of basket switch actuator 78. This outward pivotal movement depresses the switch actuator 78 against the force of spring 74 and permits leaf spring switch member 110 to move its contact 114 out of engagement with contact 112 on leaf spring member 108. In this manner the circuit through the starting winding 24 is opened and the motor continues to operate by means of a closed circuit through main winding 22.
From the above description it is apparent that our invention provides a compact centrifugal force responsive switch actuating mechanism which fits within a conventional motor structure without increasing the axial length thereof. A conventional motor structure can be slightly modified to accommodate this arrangement, the only necessity being that a splined surface 19 be provided upon the motor shaft 18. The incorporation of guide members 116 on the basket shaped switch actuator 78 insures rotation of the basket member with rotor 16 while preventing undesirable tilting or binding of the components so that it can readily move axially relative to the shaft 18 under the influence of coil spring 74 or in response to centrifugal forces sensed by the weights 94. Also, engagement of guide members in support member slots 76 fixes the radial position of the switch actuator 78 relative to the rotating motor components permitting unobstructed motor operation.
While we have shown and described a particular embodiment of the present invention it will, of course, be understood that various modifications and alternative constructions thereof may be made without departing from the true spirit and scope of our invention and that we intend by the appended claims to cover all such modifications and alternative constructions as fall within the true spirit and scope of our invention.