US 3838238 A
A centrifugal switch including a normally open embodiment and a normally closed embodiment; in either embodiment weighted portions of a spring or inertia members may be used for selecting a speed range in which the switch becomes operative. Either embodiment includes an elongated spring wherein the effective length of the spring is subject to adjustment for more precisely selecting the rotational speed at which the switch becomes operative.
Description (OCR text may contain errors)
United States Patent 1191 lomlinson 1 1 Sept. 24; 1974 CENTRIFUGAL SWITCH 3,020,465 2/ 1962 Rowe ,1 200 140 B Inventor: Bayne B. Tomlinson, Decatur UL 3,194,913 7/1965 Lmdgren 200/80 B  Assignee: Borg-Warner Corporation, Chicago, Primary Examiner-Herman Hohauser I11. Attorney, Agent, or Firm--Donald W. Banner 22 F] d: S t. 17, 1973 l 1 57 ABSTRACT  Appl. N0.: 398,261
A centrifugal switch including a normally open embodiment and a normally closed embodiment; in ei-  U.S. Cl. 200/80 B ther embodiment weighted portions of a spring or in-  Int. Cl. H01h 35/10 ertia members may be used for selecting a speed range  Field of Search 200/80 R, 80 B, 61.45, in which the switch becomes operative. Either em- ZOO/61,46 bodiment includes an elongated spring wherein the effective length of the spring is subject to adjustment for  References Cited more precisely selecting the rotational speed at which UNITED STATES PATENTS the switch becomes operative.
2,999,139 9/1961 Lee 200/80 B 12 Claims, 6 Drawing Figures w 6O 32 1 49 5! a ,1 53
58 57 52 T. 56 1a 69 37 62 32 44 I V 2 1 1 A y 11/1 'i'l 1 '1 a L2 22 /fi a CENTRIFUGAL SWITCH BACKGROUND OF THE INVENTION The present invention resides in the field of centrifugal switches and is concerned with improvements in rotatable switches permitting selection of the speed at which the switch becomes operable.
SUMMARY OF THE INVENTION A principle object of the present invention is to provide an improved centrifugal switch characterized by relatively simple, sturdy construction, a further object is to provide a centrifugal switch susceptible of simple modification for operation in different speed ranges, and a still further object is to provide a centrifugal switch including adjusting means for correlating operation thereof with a desired speed of rotation.
BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a plan view of a centrifugal switch according to the present invention;
FIG. 2 is a section view taken along the line 2--2 of FIG. 1;
FIG. 3 is a section view taken along the line 3-3 of FIG. 1;
FIG. 4 is a fragmentary section view similar to a portion of FIG. 2, illustrating a modified form of construction of switch actuating members;
FIG. 5 is a fragmentary section view similar to FIG. 4 illustrating a further modified form of construction of switch actuating members; and
FIG. 6 is a fragmentary sectional view illustrating an alternative normally closed embodiment of the switch according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now in more detail to the drawings, the reference character 10 indicates a centrifugal switch according to the present invention illustrated in a form particularly suitable for use with a flexible cable instrument drive such as a flexible drive for a speedometer of a motor vehicle.
The switch is susceptible of use in many applications where it is desired to control an electrical circuit in accordance with the speed of a rotating member and, therefore, it is to be understood that the switch may occur in various particular forms compatible with the intended application.
In the embodiment of FIGS. 1 3, the switch includes a rotatable shaft 12 journalled in a housing or body member 11 which includes a pair of electrical terminal posts or binding posts 13, 14. Brushes 26, 27 are electrically connected to respective binding posts 13, 14 by means of springs 28, 29. If desired, the brushes can be connected to the binding posts by other means such as flexible conductor straps, for example. Each end of shaft 12 is provided with a square socket portion 16, 17, counterbore 18, 19 and thrust washers 21, 22 proportioned to receive a drive fitting of a flexible shaft. Each end of body member 11 includes a threaded shoulder portion 23, 24 proportioned for engagement with a ferrule of a flexible shaft instrument drive. In the illustrated form, opposite ends of the switch are of like construction permitting connection of a flexible shaft to either or both ends thereof.
Shaft 12 includes a first journal portion 31 received within a corresponding bearing portion 32 of body 11; Adjacent journal portion 31 is an integral annular shoulder portion 33 including an axially slotted portion 34, a radially extending bore 36 and a counterbore 37.
Spaced from shoulder portion 33 is a pair of axially spaced projections 38, 39.
A retainer member 41 in the form of an axially slidable collar is mounted on shaft 12, having a keyway 42 thereof engaging projection 38. Collar 41 is permitted to move axially along shaft 12 but prevented from rotating with respect thereto as a result of the engagement between projection 38 and keyway 42.
A ring member 43 including an axial bore 44 and a radial aperture 46 is mounted on shaft 12. A second journal portion 47 of shaft 12 extends through axial bore 44 of ring member 43 while the projection 39 on shaft 12 snaps into radial aperture 46 to fix the circumferential and axial position of ring member 43 against displacement with respect to the shaft. Second journal portion 47 ofshaft 12 is rotatably received within bearing portion 48 of housing 11.
A pair of electrically conductive slip rings 49 and 51 are mounted on shaft 12 for engagement with respective brushes 26, 27. Slip ring 49 is mounted on annular shoulder 33, while slip ring 51 is mounted on ring member 43.
An elongated spring 52 is mounted to extend axially along shaft 12. Spring 52 if preferably formed of an electrically conductive material including a bight portion 53 clamped to engage slip ring 51 and a surface of shaft 12 by means of ring member 43. Bight portion 53 defines a short leg 54 engaging slip ring 51 and a long leg 56 lying along the surface of shaft 12. Long leg portion 56 of spring 52 extends through a slot 57 in retainer collar 41 into slotted portion 34 of annular shoulder 33 and terminates in a weight portion 58 lying radially inwardly of slip ring 49. Weight portion 58 is of an electrically conductive material, and may, if desired, be integrally formed with spring 52.
It is to be noted that slot 57 of retainer collar 41 includes an edge or heel-like portion 59 which serves to confine a portion of the long leg 56 of spring 52. The portion of long leg 56 between heel 59 and weight portion 58 is the effective length of the spring capable of flexing inasmuch as the remainder between heel 59 and ring 43 is confined to lie along side shaft 12. Axial movement of retainer collar 41 along the shaft and the spring results in changing the effective length of long leg 56. Inasumch asthe effective length of the spring is one factor in determining its stiffness or resistance to flexure, axial adjustment of retainer collar 41 provides means for selecting the centrifugal force required to move contact surface 61 of spring 52 outwardly into engagement with contact surface 60 of slip ring 49. In practice, the collar 41 is adjusted to permit engagement of contact surfaces 61 and 60 at a selected speed of rotation of shaft 12 corresponding to the centrifugal force required for outward movement of contact surface 61.
In order to facilitate adjustment of the axial position of retainer collar 41 which in turn regulates the effective length of the spring and the rotational speed at which the switch becomes operative, the retainer collar 41 is preferably formed as a hollow cylinder having circumferential ridges 62 extending about the outer surface thereof. A substantially cylindrical adjusting member 63 is received within a well 66 in body member 11 and includes a series of spline like teeth 64 engaged tangentially with ridges 62 of retainer collar 41. Adjusting member 63 is provided with a slotted head 67 and a friction collar 68 engaging well 66. Rotation of adjusting member 63, as by means of a screw driver, urges retainer collar 41 axially along shaft 12 and spring 52 since teeth 64 are engaged with ridges 52. Adjusting member 63 thus affords means for adjusting the action of spring 52 while shaft 12 is rotating where it is desired to correlate engagement of contact surfaces 61 and 60 with a selected speed of rotation. Friction collar 68 is effective to frictionally grip adjusting member 63 and the wall of well 66 to retain adjusting member 63 and retainer collar 41 in a selected position. For applications where changes in adjustment are not required, it is contemplated that an adjusting member such as 63 would be permanently secured in position such as by staking or welding in place.
In addition to the above described means for regulating the resistance of the spring 52, it is contemplated to provide means for aiding engagement of contact surfaces 61, 60 in response to the speed of rotation of shaft 12. Such means includes the mass of the weight portion 58 of spring 52 and may also include the mass of an auxiliary inertia member 69. As shown in FIG. 2 inertia member 69 is the form of a ball which preferably is of a dense material such as metal, located in counterbore 37. The counterbore provides a radial guideway arranged such that ball 69 urges contact surface 61 outwardly under the influence of centrifugal force. Alternative inertia members having differing masses may be employed for providing differing speed ranges for operation of the switch.
A modified arrangement of an inertia member is illustrated in FIG. 4 wherein ball 69 is received in guideway 37 and is biased in the radially outward direction by a spring 71 located in a further counterbore 72. Inasmuch as spring 52 tends to retain inertia member 69 in guideway 37 while spring 71 tends to eject it therefrom, the difference is preload force of the two springs establishes the force which must be overcome by centrifugal action of the inertia member in order to initiate closure of the contacts. When the spring 71 is strong the contacts will operate at low shaft speed and when spring 71 is weak, the contacts will operate at high shaft speed. The spring 71 thus represents further means for selecting the speed at which the contacts become operattve.
A further advantage of spring 71 resides in urging inertia member 69 against spring 52 so that its placement with respect to the axis of rotation of shaft 12 is known. The use of a spring 71 makes possible the employment of an inertia member 69 of small size with assurance that its center of gravity lies radially outwardly of the axis of rotation of shaft 12 toward the contact 58. The use of inertia members of different sizes afford means for selecting a desired mass of the inertia member which in turn affects the speed at which the contacts become operative.
A further modified arrangement of an inertia member is illustrated in FIG. wherein the inertia member 73 is in the form of a cylindrical slug received in guideway 37. A cylindrical form of slug is beneficial inasmuch as alternate slugs of varying length and diameter provide different inertia masses which can be employed for varying the speed response of the switch. In the embodiment of FIG. 5 the guideway or counterbore 37 is illustrated as extending across the axis of rotation 74 of shaft 12 terminating in a shoulder 76. This construction permits the selection of a slug 73 having dimensions such that its center of gravity 77 lies close to the axis of rotation 74 of shaft 12. When the center of gravity of the inertia member is located closer to the axis of rotation of the shaft, the response speed at which the contacts become operative is increased, and conversely where the center of gravity of the slug is located further from the axis of rotation of the shaft, the response speed is decreased. It is contemplated that the embodiment of FIG. 5 may be further modified in order to employ a biasing spring similar to the spring 71 illustrated in FIG. 4.
In each of the illustrated forms of the invention, it should be noted that the center of gravity of the contact 58 and of the inertia members such as 69 or 73 moves outwardly to a greater radius as soon as movement of the contact is initiated thus increasing the centrifugal force exerted on the contact without a corresponding increase in shaft speed. This increase in the effective orbital radius of the inertia member results in a snap action or avalanche effect which tends to propel the contact outwardly as soon as the selected speed of operation is reached. The snap action tends to hold the contact in an outer position even though the shaft speed remains constant thus avoiding chattering of the contact surfaces.
FIG. 6 illustrates an alternative embodiment of the invention in which the contact surfaces are caused to separate in response to the shaft reaching a given speed of rotation. In the alternative embodiment a nonconductive bridge portion 81 spans slot 134 in shaft 112. A conductor member 82 extends through a radial aperture 136 in shaft 112 contacting slip ring 149. A head portion of conductor 82 is received in a recess 137 and provides a contact surface normally engaging a contact surface 161 on spring 152. Upon shaft 112 reaching a predetermined speed of rotation, the weight portion 158 causes the spring 152 to deflect outwardly breaking contact between contact surfaces 161 and 160. The effective length of spring 152 is controlled by a retainer member 141 as in the case of the embodiment of FIG. 1, and an inertia member may be employed if desired to assist movement of spring 152 as in the case of the FIG. 1 embodiment.
In a preferred embodiment, the switch 10 includes numerous parts formed of a moldable electrically nonconductive material, for example, the body 11, shaft 12, retainer collar 41 and adjusting member 63 can be made of Nylon or filed Nylon. Other portions of the switch such as the spring 52, and associated slip rings, brushes, and binding posts are made of an electrically conductive material. In the embodiment illustrated in FIGS. 1 through 3 the body member 11 is in the form of an enclosing housing protecting the contact surfaces from the intrusion of foreign matter, the electrical circuit toward and from the shaft being completed by the brushes and binding posts. However, it should be recognized that the principle components of the switch are mounted on the shaft and that a subassembly of shaft and switching components may be used in some applications independently of a housing.
The embodiment of FIGS. 1 through 3 illustrates a normally open switch in which one portion of an electrical circuit is to be connected to binding post 13 which is electrically connected to spring 28, brush 26 and slip ring 49, while another portion of the circuit is to be connected to binding post 14 which is electrically connected to spring 29, brush 27, slip ring 51, and elongated spring 52. Inasmuch as contact surfaces 61, and 60 are normally separated by an air gap, the switch is normally open until shaft 12 reaches a rotational speed sufficient to move weight portion 58 outwardly into contact with slip ring 49.
The embodiment of FIG. 6 illustrates a normally closed switch in which contact surfaces Mill and 1160 are normally touching thereby closing an electrical circuit between spring 152 and slip ring 149 until shaft 112 reaches a rotational speed sufficient to cause movement of weight portion 158 outwardly away from conductor 82.
While normally open and normally closed centrifugal switches are useful in many circuit applications, the above described switches are particularly useful for controlling electrical circuits associated with combustion engines where the circuit is to be controlled in accordance with engine speed or vehicle speed.
What is claimed is:
l. A centrifugal switch including a rotatable shaft and a pair of juxtaposed electrically conductive contact surfaces mounted for relative movement toward and from engagement with each other in response to rotation of said shaft,
spring means mounted for rotation with said shaft having an elongated portion extending substantially parallel to the axis of rotation of said shaft including a resiliently flexible portion yieldable outwardly with respect to the axis of said shaft in response to centrifugal force, the effective length of said flexible portion defining a measure of stiffness opposing outward movement thereof, said flexible portion carrying one of said contact surfaces, and
means for selecting an effective length of said flexible portion including a retainer member engaging said elongated portion of said spring means limiting the effective length of said flexible portion thereof.
2. A centrifugal switch according to claim ll, wherein said retainer member comprises a collar mounted for axial movement along said shaft, said collar being engaged with said elongated portion of said spring means for limiting the effective length of said flexible portion thereof.
3. A centrifugal switch according to claim 2, including a body member associated with said rotatable shaft, wherein said collar is of substantially hollow cylindrical form slidably embracing said rotatable shaft and said elongated portion of said spring means, said body member including an adjusting member engageable with said collar for moving said collar axially along said shaft and spring means.
4. A centrifugal switch according to claim 3, wherein said collar includes a ridge portion extending circumferentially about an outer surface thereof, said adjusting member having a tooth portion tangentially engageable with said ridge portion of said collar for moving said collar axially along said shaft and spring means.
5. A centrifugal switch according to claim ll, wherein said flexible portion of said spring means carries a weight portion disposed eccentrically with respect to the axis of rotation of said shaft.
6. A centrifugal switch according to claim 5, wherein said weight portion is integral with said one contact surface.
7. A centrifugal switch according to claim 1 including an inertia member disposed radially inwardly of and engageable with said flexible portion of said spring means, said rotatable shaft including a radially disposed guideway receiving said inertia member for guiding radially outward movement thereof.
8. A centrifugal switch according to claim 7, wherein said guideway is formed for receiving alternative inertia members.
9. A centrifugal switch according to claim ll, wherein said rotatable shaft carries both of said pair of contact surfaces, said one contact surface being disposed radially inwardly of the other of said contact surfaces.
10. A centrifugal switch according to claim ll, including a body member journalled on said rotatable shaft, said body member having an electrically conductive brush mountedthereon, said rotatable shaft having an electrically conductive slip ring mounted thereon engaging said brush, said slip ring including a surface defining the other of said pair of contact surfaces.
l l. A centrifugal switch according to claim 11, including a body member journalled on said rotatable shaft,
said body member having first and second electrically conductive brushes mounted thereon, said rotatable shaft having first and second electrically conductive slip rings mounted thereon engaging respectively said first and second brushes, said spring means providing an electrical conductor having one end thereof connected to one of said slip rings and another end thereof connected to said one contact surface, the other of said slip rings having a surface defining the other of said contact surfaces.
12. A centrifugal switch according to claim ll, including a body member formed of an electrically nonconductive material having first and second electrically conductive brushes mounted therein spaced from each other, said body member including terminal posts connected to respective brushes, said rotatable shaft being journalled in said body member and formed of an electrically nonconductive material, said shaft carrying first and second electrically conductive slip rings engaging respective brushes, said spring means being formed of an electrically conductive material connected to one of said slip rings and having said flexible portion thereof extending into proximity with the other of said slip rings, a surface portion of the other of said slip rings defining the other of said contact surfaces disposed for engagement with said one contact surface in response to deflection of said flexible portion of said spring