US2777912A

US2777912A - Adjustable centrifugal switch assembly

Info

Publication number: US2777912A
Application number: US431529A
Authority: US
Inventors: Jr William A Haines
Original assignee: AO Smith Corp
Current assignee: AO Smith Corp
Priority date: 1954-05-21
Filing date: 1954-05-21
Publication date: 1957-01-15
Anticipated expiration: 1974-01-15

Description

Jan. 15, 1957 w, s, JR 2,777,912

ADJUSTABLE CENTRIFUGAL SWITCH ASSEMBLY Filed May 21, 1954 INVENTOR. WllZLCLlTl A.Hau1es,lr.

WMVM ATTORNEY;

.inited States Patent @fifice 2,777,912 Patented Jan. 15, 1957 ADJUSTABLE CENTPJFUGAL SWITCH ASSEMBLY William A. Haines, Jr., Troy, Ohio, assignor to O. Smith Corporation, Milwaukee, Wis., a corporation of New York Application May 21, 1954, Serial No. 431,529

7 Claims. (Cl. 20080) This invention relates to a centrifugally actuated switch and particularly to a switch which is adjustably mounted in relation to a centrifugal actuator.

In the mounting of a centrifugal switch in relation to its actuator, various factors such as contact clearance and pressure and switch clearance are critical.

In accordance with the present invention a switch is constructed in a self-contained manner to automatically set the required clearances and pressure. Further, the switch is provided with a pivotal attachment which permits easy initial setting and positive clamping so that the original setting cannot be disturbed.

More particularly, the switch is a self-contained unit having the necessary contact clearance and pressure. The switch is adjustably attached to the actuator, such that when the actuator, in a non-responsive position, engages the switch in a closed position, the assembly is correctly adjusted.

Therefore, one object of the invention is to provide an adjustable centrifugal switch assembly with an improved attachment construction.

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

In the drawing:

Figure 1 is a view partly in section of the switch and actuator in a non-responsive position;

Figure 2 is an elevational view of the actuator, viewed from the right in Figure 1;

Fig. 3 is an elevational view of the switch, viewed from the left in Figure 1;

Fig. 4 is a reduced elevational view of the switch, with the cover removed, as viewed from the right in Figure 1; and

Fig. 5 is a similar view of the switch cover, viewed from the left in Figure 1.

Referring particularly to Figure l, a centrifugal actuator 1 is secured to the end of a rotatable shaft 2 which is journaled in a bearing 3. A switch 4 is secured to a stationary bearing support 5 of bearing 3 and in spaced relation to the actuator 1.

The actuator 1 is of a conventional variety having a pivotal weighted switch actuating member or operator 6 disposed transversely of the shaft 2 and responsive to a predetermined speed of rotation of the shaft 2 to actuate the switch 4. The operator 6 is provided with a pair of transversely extending ears 7 trunnioned in the upper portion of the side arms 8 of a support bracket 9. The side arms 8 are in spaced parallel relation with the operator 6 disposed therebetween. To bias the operator 6 to a non-responsive position, a pair of longitudinal springs 10, one secured to each exterior side of arms 8, are provided with hooks on both ends thereof with the hooks of each spring engaging respectively a lug 11 on the op erator and a lug 12 on the side arms 8. The springs bias the weighted end of the operator 6 downwardly into engagement with a web portion 13 of the bracket 9 extending above the shaft 2. In this position the lower end of the operator 6 is biased upwardly and outwardly, holding the contacts 14 of switch 4 in a closed position.

Each arm 8 has a vertical extension 15 disposed in the path of the operator 6 and limiting the pivotal movement of the operator. The movement or" the operator 6 is therefore between the top of the web portion 13 and the extensions 15 which movement is sufficient to completely disengage the switch 4, as subsequently described.

The actuator 1 is secured to the end of the shaft as by a bolt 16 passing through an opening in the web 13 of bracket 9 and threaded into the center of the shaft 2.

Referring now to switch 4 the contacts 14 of the switch are totally enclosed by a generally rectangular housing consisting of an inner wall 17 and an outer wall or cover 18 constructed of a suitable electrically insulating material.

The inner wall 17 is provided with sides 19 which extend to the outer wall or cover 18 and define a switch chamber. The

walls

17 and 18 are provided with matching flanges 20 through which rivets 21 extend and hermetically join the walls.

A metal strip spring 22 is disposed within the housing and is secured at one end to the interior surface of the wall 18 as by rivets 23 and carries at its other free end a floating contact 24 of contacts 14. An L-shaped connector 25 is secured to the exterior surface of wall 18 by the lower rivets 23 to provide for the connection of contact 24 in an electrical circuit, not shown. The spring 22 is secured to an enlarged lower portion 26 of the outer wall 18 to permit floating movement of the contact 24.

The spring 22 is prestressed such that the contact 24 is biased toward the wall 17. The free end of spring 22 is provided with transversely extending cars 27 which engage small protrusions 28 extending from the sides 19 of wall 17 to limit the movement of the spring 22. The prestressing of the spring 22 provides the desired contact pressure for contacts 14, when in a closed position, with optimum contact clearance when in an open position.

A metal strip spring 29, similar to the spring 22, is secured at its lower end to the interior surface of wall 17 as by rivets 30 and carries at its free end the movable contact 31 of contacts 14 in alignment with contact 24. The spring 29 is prestressed, similar to spring 22, to bias the upper end of the spring 29 against the inner wall 17 i with the contact 31 disengaged from contact 24 a predetermined distance to provide the desired contact clearance therebetween in open condition.

The outermost portion of the free end of spring 29 has a generally U-shaped portion 32 with the shaft of the switch operating button 33 passing therethrough and with the tips of the U-shaped portion crimpe-d toward the inner wall 17 as at 34. A generally L-shaped connector 35 is secured to the exterior surface of wall 17 by the lower rivet 30 to provide for the connection of contact 31 in an electrical circuit, not shown.

The button 33 has an enlarged portion 36 journalled in an opening in a tubular extension 37 of the inner wall 17. The opening through which the enlarged portion 36 of button 33 passes is hermetically sealed by a rubber boot 38 which is generally tire-shaped with the ends fitting tightly in a ring groove in the exterior end of the button 33 and a ring groove in the tubular housing extension 37. The boot 38 in addition to hermetically sealing the opening prevents the button 33 from turning in the extension 37 and therefore reduces wear on the button.

A flange 39 at the innermost end of button portion 36 provides a stop to limit the outward travel of the button spring 29 to move the contact 31. The U-shaped portion 32 of the spring 29 provides a balanced pressure at two diametrically opposite points of the button 33 and prevents the tendency of the button to bind in the guide opening as it is moved. When the button 33 moves inwardly, the flange 39 engages the spring 29 at 34 and moves the contact '31 toward contact 24.

The inner end of the shaft of button 33 is slidably mounted in a cylindrical recess 40 in the outer wall 18 and the inward travel of the button 33 is limited by the engagement of the button and the bottom of recess 40.

The button 33 is constructed in cooperation with the prestressed springs 22 and 2-9 such that the desired contact pressure is obtained when the button 33 moves to its innermost position and such that the desiredcontact clearance is obtained when the button 33 moves to its outermost position. Further, the distance the button 33 travels between its outer and innermost positions is less than the travel of the operator 6 and therefore the button 33 and operator 6 are disengaged in the responsive position, as previously noted The switch 4 is secured to the support with the button 33 disposed in thepath of the operator 6 and with the button in its innermost Position when. the .operator 6 is in a non-responsive position, as shown inl-" igure 1.

The switch 4 is attached in place by a channel-shaped bracket 41 which is bolted to the stationary support 5 as at 42. The sides 43 of the bracket extend upwardly to support the switch 4 with the button 33in the path of operator 6. The switch ,4 ,is secured to the bracket 41 by an upper bolt 44 and a lower b lt 45 each of which passes through aligned openings in the bracket sides and a transverse opening ,in the inner wall 17 of he switch, the inner wall 17 being suitably thickened transversely to provide the Ieqniredbolt openings.

The upper opening in the wall of the switch isfenlarged toform an elongated slot 46 allowing limited pivotal movement about thelower bolt 45. i

In assembly, the actuator 1 is first secured, to shaft 2. The switch 4 is pivotally secured to thebracket 41 and pivoted against the switch operator 6 until the button 3,3 lightly engages the bottomvofthe recess 4.0. While the button 33 is held against the bottom of recess 40,

bolts

44 and 45 are tightened to hold the switch in place. Thereafter the resilience in the complete system disengages the button 33 from the bottom ..of the recess ,40Qso that no force over and above that exerted by springsIZZ and 29 is applied through button 33 to the operator .6. This disengagement is in the order of a few thousandths of an inch which is indicated in an exaggerated manner in Figure 1 as at 47 and is 'suflicient to prevent undue pressure on operator 6 which might force it to operate at an unintended lower speed. The actuator 1 and switch 4 are then in the position illnstratedi-n Figure 1. The position of the actuator 1 and switch 4 in aresponsive position is shown in Figure l bythedashed-lineposition of the operator 6 and button '33.

Theoperation of the actuator and switch is .as follows:

,At a predetermined speed of rotation wat the shaft 2, the centrifugal force acting on the operator 6 overcomes the force of the longitudinal springs with a resultant pivoting of the operator 6. The operator 6 disengages the button 33 and the contacts 14 are instantly opened as a result of the prestressing of s prings 22 and '29 toward the wall 17. V i

As previously noted, the switch 4 is constructed such that the limited movement of the button 33 provides thedesired contact clearance and contact pressure for the contacts 14 when the button is in its outermost and innermost positions, respectively. The mounting method described provides an ,accurate and simple .rnanner of switehlooation for areguired contactseparation whenthe switch-is open and contact pressure when the switch is closed.

Various embodiments of the invention may be employed within the scope of the following claims.

I claim:

1. The combination of a switch member and centrifugal actuator with said actuator being mounted on a rotatable shaft and having a switch actuating member responsive to a predetermined speed of rotation of the shaft, said switch member comprising a housing, a pair of resilient switch contacts secured within said housing, switch means extending between one of said contacts and the switch actuating member and adapted to engage and disengage the contacts upon actuation by the switch actuating member, stop means in the housing in the path of the switch means to limit the movement of the switch means by the switch actuating member when the switch means is initially assembled with said switch actuating member, a frame disposed adjacent the rotatable shaft, adjustable securement means securing the switch housing to said frame so that when the switch member is initially assembled with the centrifugal actuator prior to a clamp ing of the securement means and the shaft is in nonro'tating position the switch actuating member is disposed in engagement with the switch and the switch means is manually held in engagement with the stop and the contacts are in engagement with each other whereby the switch member is accurately located re1ative to the centrifugal actuator, and a relief space being formed between said switch means and the stop means upon release of the switch means after a clamping of the securement means to thereby eliminate undue pressure on' the actuator that might result in its operation atan unintended lower speed.

i 2. The combination of a switch and centrifugal actuator, said actuator being mounted on a rotatable shaft extending from a motor with which the combination is employed and having a switch actuating member responsive to'a predeterminedspeed of rotation of the shaft, said switch member comprising a housing, a pair of resilient switch contacts secured within said housing, switch means extending between one of said contacts and the switch actuating member and adapted to engage and disengage the contacts upon actuation by the switch actuating member, stop means in the housing in the path of the switch means to' limit the movement of the switch means by the switch actuating member when the switch means is initially assembled with said switch actuating member, a frame in which ,the shaft is journaled and disposed adjacent the housing, a bolt means securing the housing of the ,switch member to the frame adjacent the end of the housing removed from the switchmeans, a transverse slot in the housing between the bolt means and the switchnneans, a second bolt means extending through the slot with said slot permitting manual pivoting of the housing onthe first named bolt means upon initial assemblynof the switch member and centrifugal actuator to at that time dispose the switch actuating member in engage ment with the switch and to hold the switch means in engagement with the stop and the contacts in engagement with each other whereby the switch member is accurately located relative to the centrifugal actuator, and a relief space being formed between said switch means and the stop upon the manual release of the switch means as a result of the resilience of the switch mounting to thereby eliminate undue pressure on the actuator that might result' in its operation at an unintended lower speed.

3. In combination, a centrifugal actuator mountedon a rotatable shaft and having switch actuating mechanism with an axial movement, a pair of contacts resiliently mounted on a support disposed adjacent said switch actuating mechanism with one of said contacts being adapted to bemoved by said mechanism and both of said contacts being biased oward said a me han pm an .1. s i support limitingthe movement of the contacts toward said actuator and providing a predetermined contact clearance between the contacts in open position, a second stop means on said support limiting the movement of the contact moved by the switch actuating mechanism to provide a predetermined contact pressure between the contacts in closed position, and adjustable means securing said support for the contacts in place relative to said actuator to provide for full movement of the contact actuated by the actuating mechanism between said stop means and to effect a positioning of the support and actuator without close tolerance demands on the securing means and with out trial and error tensioning of said resilient contacts.

4. In combination, a centrifugal actuator secured to a rotatable shaft and having a switch operator responsive to a predetermined speed of rotation, and a switch unit comprising a housing pivotally mounted in spaced relation to said actuator, a pair of leaf springs disposed within the housing and secured at one end to said housing in spaced relation to each other, a contact on the free end of each of said leaf springs in general alignment with each other, said leaf springs being prestressed to effect a bias of the contacts in the same direction and one of said leaf springs being moved in response to movement of said operator and thereby alternately opening and closing the contacts on said springs, stop means in the housing in the stressed-wise path of said leaf springs to provide a predetermined clearance between the contacts in an open position, a second stop means in the housing to limit the movement of said leaf springs in closing the contacts and thereby provide a predetermined contact pressure between said contacts in a closed position, and means to secure said housing in a predetermined fixed relation to said actuator with said contacts in closed position whereby the mounting of the actuator and contacts is facilitated.

5. In combination, a centrifugal actuator mounted on a rotatable shaft and having a switch operator responsive to a predetermined speed of rotation of said shaft, a switch contact housing pivotally mounted adjacent said operator on a frame supporting said shaft, a leaf spring secured at one end to said housing and having the other end disposed in the path of said operator, said leaf spring being prestressed toward said operator, stop means extending from said housing into the path of said leaf spring between the spring and the actuator, a contact secured to the free end of said leaf spring, a second leaf spring secured at one end to said housing in spaced and aligned relation to said first leaf spring, said second named leaf spring being prestressed toward said first named leaf spring, a contact secured to the free end of said second leaf spring and disposed in alignment with said first named contact, stop means located in said housing in the stressedwise path of said second spring to provide a predetermined clearance between said contacts, stop means located in said housing and limiting the contact engaging movement of said first leaf spring to provide a predetermined pressure between the contacts when said contacts are closed, and said housing being secured to the frame when said contacts are in closed position and the first named leaf spring is engaged by said operator to assemble the actuator and switch contacts for accurate operation.

6. In combination, a centrifugal actuator support mounted on the end of a rotatable shaft, a switch operator pivoted on said support transversely to the axis of the shaft to effect axial and shaft-wise movement of a portion of the operator in response to a predetermined speed of rotation of the shaft, a spring biasing said operator to a non-responsive position, a switch contact housing disposed adjacent said shaft on a frame supporting said shaft, a leaf spring secured at one end to said housing and having the other end unsecured, said leaf spring being prestressed to bias its unsecured end toward said operator, a portion of the housing disposed to engage said leaf spring and limit the operator-wise movement of the spring, a contact attached to the unsecured end of said leaf spring, a second leaf spring attached at one end to said housing diametrically opposite and in alignment with said first leaf spring, a contact attached to the unsecured end of said second leaf spring and aligned with said first contact, said last named leaf spring being stressed to bias said second contact toward said first contact, a portion of said housing disposed in the stress-wise path of said second spring to effect a predetermined clearance between said contacts, a contact lever journaled in the walls of said housing and adapted to move said leaf spring to effect engagement between said contacts, a lever stop portion of said housing disposed in the contact engaging path of said lever to provide a predetermined contact pressure, and pivotally attaching means adapted to secure said housing to the frame when the contact lever is engaging said operator and said lever stop portion, said construction eliminating close tolerances in assembling the actuator support and the switch housing and eliminating trial and error stressing of said leaf springs to obtain the predetermined contact clearance and pressure.

7. In combination, a frame, a channel-shaped support having a web secured to an end of a rotatable shaft supported by said frame with said support having axially extending sides with aligned openings in the upper portion thereof, a switch operator having ears extending into said openings to support the operator for pivotal movement, spring means biasing said operator to a non-responsive position with a projection on said operator extending axially outwardly of the shaft, said operator responding to a predetermined speed of rotation of the shaft to move said projection of the operator generally axially toward said shaft, a hollow switch housing disposed adjacent said shaft and having vertically spaced openings in one wall to receive attachment bolts for securing the housing to said frame, one of said openings being in the form of a transverse slot to effect limited pivotal movement of the housing about the other of said openings and the wall of the housing having said openings being disposed transversely to said shaft, a contact rod journaled in one end of said housing and aligned with the projection of said operator, a leaf spring attached at one end to the inside of said housing and having the other free end adapted to be engaged by said contact rod, a contact affixed to the free end of said leaf spring, said leaf spring being prestressed a predetermined degree toward said operator to bias said rod toward the operator, a second leaf spring attached at one end to the inside of said housing and spaced from and longitudinally aligned with said first named leaf spring, a contact afiixed to the unsecured end of said second leaf spring in alignment with said first named contact, said second leaf spring being prestressed a predetermined degree toward said first leaf spring, protrusions on the inside of said housing engaging said second leaf spring and holding the second spring a predetermined distance from the first spring to provide a predetermined contact clearance, said contact rod extending outwardly of the housing and being engaged by said operator when the operator is in a non-responsive position and the opposite end of the contact rod being journaled in a recess in a wall of the housing with the base of the recess limiting the movement of said rod to effect the engagement of said contacts with a predetermined contact pressure, and said switch housing being secured to said frame when the contacts are in an engaged position and the contact rod is engaged with the operator disposed in a non-responsive position, said construction facilitating the mounting of the combination on the shaft and bracket.

References Cited in the file of this patent UNITED STATES PATENTS