US3649793A

US3649793A - Trigger mechanism for rotary switches and the like

Info

Publication number: US3649793A
Application number: US63442A
Authority: US
Inventors: Alexander Maclean
Original assignee: ELECTRO SWITCH CORP
Current assignee: ELECTRO SWITCH CORP
Priority date: 1970-08-13
Filing date: 1970-08-13
Publication date: 1972-03-14
Anticipated expiration: 1989-03-14

Abstract

A trigger mechanism for rotary electrical switches and the like has a first roller mounted for rotation about a fixed point and a second roller mounted on a movable support with the support being pivotally mounted for pivotal movement about a pivot point spaced from the center point of the second roller. Means urge the second roller into contact with the first roller at a point lying on coincident radii of the first and second rollers for establishing a latch position of the trigger mechanism. A trip means preferably in the form of a solenoid push rod is provided for moving the first roller pivotally about its fixed pivot point. The trigger mechanism permits an extremely large force as may be provided by a loaded spring, to be maintained in the latch position and immediately released by a small force provided by the trip means which trip means can be small in size, fast acting and relatively inexpensive. Thus, rotary electrical switches such as lockout relays can be latched in a first position and automatically tripped by a small force to be immediately responsive to move to a second position.

Description

United States Patent MacLean Mar. 14, 1972 [54] TRIGGER MECHANISM FOR ROTARY SWITCHES AND THE LIKE [72] Inventor: I Alexander MacLean, Hingham, Mass.

[73] Assignee: Electro Switch Corp., Weymouth, Mass.

[22] Filed: Aug. 13, 1970 21 Appl. No.: 63,442

2,696,536 12/1954 Coggeshall et 31.... .....335/25 3,009,034 11/1961 Barkan ..335/25 3,187,593 6/1965 McCloud 200/153 X Barry ...200/63 R,

Primary Examiner-R. F. Staubly Assistant ExaminerGeorge A. Montanye Attorney-Wolf, Greenfield & Sacks [5 7] ABSTRACT A trigger mechanism for rotary electrical switches and the like has a first roller mounted for rotation about a fixed point and a second roller mounted on a movable support with the support being pivotally mounted for pivotal movement about a pivot point spaced from the center point of the second roller. Means urge the second roller into contact with the first roller at a point lying on coincident radii of the first and second rollers for establishing a latch position of the trigger mechanism. A trip means preferably in the form of a solenoid push rod is provided for moving the first roller pivotally about its fixed pivot point. The trigger mechanism permits an extremely large force as may be provided by a loaded spring, to be maintained in the latch position and immediately released by a small force provided by the trip means which trip means can be small in size, fast acting and relatively inexpensive. Thus, rotary electrical switches such as lockout relays can be latched in a first position and automatically tripped by a small force to be immediately responsive to move to a second position.

12 Claims, 4 Drawing Figures PATENTEDMAR 14 I972 INVENTOR ALEXANDER \MCIC LEAN ATTORNEYS TRIGGER MECHANISM FOR ROTARY SWITCHES AND THE LIKE BACKGROUND OF THE INVENTION Lockout relays of various types are often used in the electrical power industry. Such relays are automatic trip, manual reset, control relays for the purpose of tripping and locking out circuit breakers automatically when a fault or predetermined condition such as an overload exists. The relays or switches are generally used in conjunction with differential relays to protect transformers, buses and rotating 'machinery in various electrical systems. Lockout relays of known types often have as many as or more normally open electrical contacts and 10 or more normally closed electrical contacts. The relays can be programmed to change sequences such as by shutting down an overhead pump and starting up a standby pump or bypassing a fault circuit by tripping and closing breakers. 1

Such relays are normally latched in a first position against the bias of stored energy such as coil spring energy normally urging the relays to a second or trip position. Fast operating times from the reset to the trip position are required and trigger mechanisms with high mechanical advantages are desired.

It has been a problem in the art to obtain fast operating switching with high reliability in compact efficient relays.

It is an object of this invention to provide a trigger mechanism enabling latching in a first position against the bias of a high force yet allowing tripping of the latch by a small force.

Another object of this invention is to provide a trigger mechanism in accordance with the preceding object which is particularly useful in electrical switches and relays.

Still another object of this invention is to provide a trigger mechanism in accordance with the preceding objects which is highly compact and not subject to unwanted tripping by vibration or mechanical shock.

Still another object of this invention is to provide a tripping mechanism in accordance with the preceding objects which can be actuated by small solenoids and has low cost.

SUMMARY OF THE INVENTION A trigger mechanism in accordance with this invention comprises a first roller means mounted for rotation about a fixed central point. A second roller means is mounted on a movable support with the movable support mounted for pivotal movement about a pivot point spaced from the center point of the second roller means. Means are provided for urging the second roller means into contact with the first roller means at a point lying on coincident radii of said roller means. Trip means are provided for moving the first roller means about the first-mentioned fixed central point.

The first and second roller means are preferably dynamically balanced and the means urging the second roller means into contact with the first roller means is preferably a source of stored energy such as a spring. In the preferred embodiment, the trigger mechanism is incorporated in a lockout relay and the trip means comprises a small solenoid and a part of the first roller means.

It is a feature of this invention that the mechanism can be highly compact yet highly efficient having mechanical advantages ratios of latching force to trip force of at least 30 to l. The tripping force distance of travel can be extremely small. Fast operation times of 8 milliseconds and below can be obtained with the use of small trip solenoids. The trigger mechanisms are highly resistant to accidental tripping of the latched condition by shockand vibration.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will be better understood from the following specification when read in conjunction with the accompanying drawings in which:

FIG. I is a side view of a preferred embodiment of a trigger mechanism of this invention in a lockout relay;

FIG. 2 is a rear end view thereof; and

FIG. 3 is a cross-sectional view thereof taken through line 3-3 of FIG. 1.

FIG. 4 is a diagrammatic cross-sectional view taken through line 4--4 ofFIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENTS With reference now to the drawings, a trigger mechanism in accordance with this invention is generally designated at 10 and is incorporated in a lockout relay having a conventional switch portion 11. The switch portion of the relay is a known rotary switch such as a Series 24 rotary selector switch produced by Electro Switch Corporation of Weymouth, Massachusetts.

The switch portion 11 is formed by a plurality of insulating rings 12 defining an axial passageway 13 and carrying a plurality of standard metallic contacts 14 for attachment of suitable electrical connections. In the preferred embodiment, contacts 14 are provided in 4 rows extending around the periphery of the rings 12 and equally spaced thereabout. A preferably square cross section switch shaft 15 extends through the passageway 13 and through trigger

mechanism mounting plates

16 and 17 to a handle 18. The rear end of the shaft 15 is cylindrically formed at one section and mounted in stop plate 19. A rear plate 100 mounts the shaft for rotation as will be described. A panel plate 20 is attached by screws 21 to mounting plate 17. Four assembly bolts 23 lock the components in position and are provided with conventional circular sleeve spacers 24 to separate the

mounting plates

16 and 17.

The shaft 15 as best shown in FIG. 4 carries rotary knife contacts 30 positioned apart and adapted to make contact with conventional extensions of contacts 14 which extend into the passageway 13. A coil spring 31 provides a source of stored energy for the rotary switch in a conventional manner. As seen from the diagrammatic showing in FIG. 4, the latched condition of the switch is shown called herein the reset position where the shaft is spring loaded by spring 31. Upon release of the latched condition, the shaft rotates 45 as indicated by dotted lines 32 to the trip position thereby making contact with a second set of contacts. Thus the first set of contacts can be used to interconnect circuitry in the reset position which is normally operating. Upon occurrence of a fault, the trigger mechanism is actuated to release the latch whereupon the stored energy of the spring immediately shifts the contacts 30 to make contact with a second circuit as known in the art.

Turning now the trigger mechanism 10 best shown in FIGS. 1 and 3, a first roller means 40 is mounted for rotation about a fixed central point 41 and positioned to coact with a second roller means 42 mounted for rotation about a central point 43 on a roller support arm 44 which in turn pivots about a point 45.

The roller support arm 44 has a square cutout 46 at one end thereof passing therethrough and in which is mounted the shaft 15. A downwardly depending circular boss or bearing 47 fits within a circular opening in the mounting plate 16 to permit rotation of the roller support arm pivotally about point 45 coinciding with the central axis of the shaft 15.

One end of the roller support arm 44 carries a cutout notch 44A defining upper and lower forked arm portions between which extend fixed stop pins 48 and 49. Roller 42 is mounted for free rotation about a pin 50 fixed on the forked arms of the roller ann portions and having an axis coincident with the central axis of roller 42. The roller 42 is as near perfect a cylinder as possible so that it is dynamically balanced about the axial point 43.

A mounting block 60 is fixed in position between

plates

16 and 17 by one of bolts 23 passing through a preformed hole 61 and a protruding boss 62 passing through a corresponding hole in plate 16. Mounting block 60 has a forked end as described with relation to the roller support arm.

Roller means 40 is mounted for rotation about a fixed pin 63 fixed to the forked arms of the block 60 and having its central axis coincident with a central axis of cylindrical curved surface 64 of the roller means 40. The roller means 40 is a section of a roller or flat cylinder which has been cut away to form

lever arm portions

65 and 66 on either side of the pivot point 41. These

lever arm portions

65 and 66 are dynamically balanced, i.e., the center of moments of each portion lies on a diameter line passing through central point 41 and is equally spaced from the point 41. Dynamic balancing of the

rollers

42 and 40 is desirable. Shock and vibration forces acting on either side of the central points of the rollers, when they are in the latched position, do not tend to release the latch but tend to balance each other out.

Preferably the top and bottom surfaces of the arm portions 66 at the cylindrical surface portion 64 are beveled slightly as shown at 64A to ensure against snagging of the arm portion 66 between the upper and lower forked arm portions. The roller 40 is pivotal about the pin 63 in both a clockwise or counterclockwise direction.

A pin 70 is fixed in position and extends between the arms of the mounting block 60. A wire or leaf spring 71 is mounted thereon to provide a very slight force constantly urging the roller 40 in a clockwise direction as viewed in FIG. 3. This spring may provide, for example, 1 ounce of force so as to urge the end 66 into position against the pin 48 in the latched position of the trigger mechanism shown in FIG. 3.

A conventional solenoid 72 is fixed in position on an extension 16A of the plate 16 with its push rod 73 designed to reciprocally move in the directions of

arrows

74 and 75 as known in the art. The push rod 73 is preferably positioned toward the outer extremity of portion 65 to maximize the lever action of the roller 40 and enable a small tripping force to be applied to a surface 76 of portion 65 causing counterclockwise movement of end 66 and releasing the latch. Because of the positioning of the push rod, and the high mechanical advantage obtained, a small solenoid can be used with a minimized actuation distance required between the rest position of the push rod shown in FIG; 3 and the actuated position thereof which trips the latch.

Preferably the diameter of the roller 40 is larger than the diameter of the roller 42 in order to maximize mechanical advantage. The

pins

50 and 63 can be of equal diameter. However, in the preferred embodiment pin 63 has a slightly larger diameter than pin 50 since it can be made of a softer material such as soft stainless steel and can have a larger diameter without greatly increasing friction between it and the larger roller 40. In the preferred embodiment, the roller has a fillets 80 and 84 to increase strength and reduce the possibility of internal stresses being set up from heat treating of the roller. All moving surfaces are preferably made of hard materials such as stainless steel'or heat treated metals to assure long life and avoidance of flats on any of the curved surfaces.

In a specific example of this invention, the diameter of surface 64 is l% inches, the diameter of pin 63 is three thirtyseconds inch, the diameter of roller 42 is one-fourth inch, the diameter of roller pin 50 is five sixty-fourths inch. Central point 43 is spaced 0.550 inch from the axis 45 of shaft 15. Solenoid push rod 73 has an end spaced 0.040 inch from surface 76 in the latched position and can be actuated to move in the direction of arrow 74 through a distance of 0.125 inch to trip the mechanism and provide a safety factor of overtravel. In the latched position shown in FIG. 3,

rollers

40 and 42 touch at a point lying on coincident radii R1 and R2 and the load force of the spring 15 is directed along R2. When this force is in an amount of 45 pounds, the tripping force exerted by the solenoid push rod can be 1 k pounds.

Turning now to the operation of the trigger mechanism, a theoretical Y-axis is indicated through the centerline of the shaft 15 with an X-axis at a right angle thereto. In the latched position, when the switch is loaded against the bias of the spring 31, a centerline 85 is shown passing through

axial points

45 and 43 with the small roller 42 having a radius R2 coincident with the radius R1. The radii R1 and R2 define a line at a 90 angle to line 85. The

rollers

40 and 42 are urged together at a line of points where their cylindrical surfaces contact each other. To release the latch, the roller 40 must move counterclockwise through a distance D. This movement is caused by solenoid push rod 73 acting against the surface 76 causing the roller 40 to pivot in the direction of arrow 81. As soon as the roller 40 has pivoted, the stored spring energy of spring 31 moves the roller 41 through an angle of 45 to a position where line 85 overlies the X-axis indicated and the shaft 15 is correspondingly rotated 45 to reset the contacts and switch on a second circuit if desired as indicated by the dotted lines 32 in FIG. 4. When in the latched position FIG. 3, vibrations will not cause tripping of the switch since inertial forces will be balanced about the pivot points of each of the rollers.

To reset the switch, the handle 18 is manually grasped moving the shaft 15 and attached forked plate 44 clockwise until such movement is stopped by a stop pin 52 extending from plate 16. At or shortly before this point, the spring 71 urges the roller 40 against the stop pin 48 whereupon release of manual force engages'the latch as shown. Manual force applied to the handle 18 in a counterclockwise direction, will not move the contacts once the latch position is reached unless the switch is destroyed. In addition, manual turning of the handle 18 in a clockwise position cannot take the switch out of its latched position but merely allows some slight movement toward pin 52. Thus, a safety feature is provided since only electrical actuation of the solenoid push rod 73 can trip the switch.

A stop for the counterclockwise rotation of the switch shaft 15 is provided by a conventional stop plate 19 having a stop edge 101. A cam or stop arm plate 102 has an edge 103 and is fixed to shaft 15 for rotation therewith. Then plate 102 has an inwardly extending circular boss (not shown) mating with a cylindrical cutout in backplate 100 and acting as a shaft bearing. The stop assembly is known in the art and other stop means can be used. When the latch is tripped surface 103 rotates with the shaft until it meets fixed edge 101 which acts as a limit stopping further rotation of the shaft.

Alternatively a stop pin similar to pin 52 can be located on the plate 16 to limit travel of the roller arm in the tripped position if desired.

Suitable leads can be connected to contacts 14 as known in the art. Solenoid leads 72A and 72B are preferably actuated through a set of contacts 14 to which is attached conventional circuitry to activate the solenoid rod to move in the direction of arrow 75 to automatically trip the latch when a predetermined condition is sensed. The solenoid is then deenergized since the solenoid contacts are opened in the trip position.

While a specific embodiment of this invention has been shown and described, many variations thereof are possible. For example, in some applications, the load applied along the line of the coincident radii need not be a resilient spring load but can be a weight. While it is preferred to use a solenoid tripping push rod, the mechanism can be tripped by manual pressure applied to surface 76 or other means in other embodiments. While it is preferred that a straight line drawn through

points

45 and 43 be at a right angle to a second straight line through points 43 and 41 (which is considered to be formed of coincident radii of the two roller means), these lines can vary in angular relationship so long the angle between them is less than l80 and greater than 0. It is preferred that the angular relationship be to minimize the required release or trip force that must be applied by the roller 40 since this force will increase as the angular relationship varies from 90.

While it is preferred that the

rollers

40 and 42 be mounted for rotation about fixed pins such as 50 and 63, in some cases ball bearing pivoting of these rollers about their central points can be used. Similarly, other pivoting arrangements can be used. While it is preferred that the rollers be symmetrical to provide for dynamic balancing, they need not be symmetrical in order to obtain the advantages of increasing mechanical advantage and enabling use of small tripping forces. Moreover,

resistance to accidental tripping due to vibration can be obtained by use of dynamic balancing without symmetry in the rollers employed. In some cases, the roller 42 can be fixed to the roller support arm 44 rather than rotate about point 43. However, higher frictional forces are thereby encountered which tend to wear the contacting cylindrical surfaces and decrease the mechanical advantage obtained.

What is claimed is:

1. A trigger mechanism comprising a first roller means defining a cylindrical surface mounted for rotation about a fixed center point of said cylindrical surface,

a second roller means mounted on a movable support and having a cylindrical surface and a center point of said lastmentioned surface,

said movable support being mounted for pivotal movement about a pivot point spaced from said center point of said second roller means,

"means for urging the cylindrical surface of said second roller means into contact with the cylindrical surface of said first roller means at a point lying on coincident radii of said roller means to latch said first and second roller means,

said first and second roller means being dynamically balanced so that when said first and second roller means are latched and subject to dynamic forces of shock, impulse and vibration, forces on either side of the center point of each roller means balance out to avoid rotation of the roller means,

and trip means for moving said first roller means about said fixed center point to trip said system.

2. A trigger mechanism in accordance with claim 1 wherein said means for urging said second roller means is a spring,

said first and second roller means are each symmetrical about their respective center points,

and said second roller means is mounted for rotation about said second roller means cylindrical surface center point.

3. A trigger mechanism in accordance with claim 2 and further including a stop means for limiting pivotal movement of said first roller means to define a latch position of said system.

4. A trigger mechanism in accordance with claim 3 and further comprising second spring means for urging said first roller means toward said stop means.

5. A trigger mechanism in accordance with claim 3 wherein said trip means comprises a solenoid push rod mounted for reciprocation toward and away from said first roller means to permit alternative tripping and latching of said system.

6. A trigger mechanism in accordance with claim 5 wherein said first roller means comprises two dynamically balanced portions of a cylinder.

7. A trigger mechanism in accordance with claim 5 wherein a straight line running through the center points of said first and second roller means and said point lying on coincident radii is perpendicular to a straight line running through said center point of said second roller means and said pivot point.

8. A trigger mechanism in accordance with claim 5 wherein said movable support of is fixed to an electrical switch shaft for movement therewith.

9. A trigger mechanism in accordance with claim 8 wherein said spring is a coil spring attached to the said shaft to load said shaft when said trigger system is latched and to pivot said movable support when said trigger system is tripped.

10. In a rotary electrical switch having a first set of stationary contacts and a second set of stationary contacts with a switch shaft carrying a third set of movable contacts for contacting said first set of contacts in one position and said second set of contacts in a second position when rotated about said shaft axis, the improvement comprising,

a first roller means having a cylindrical surface mounted for rotation about a fixed center point of said cylindrical surface,

a second roller means mounted for rotation on a movable support and havin a c lindrical surface and a center point of said su ace a out which said second roller means is free to rotate,

said movable support being mounted for pivotal movement about a pivot point spaced from a center point of said second roller means, said switch shaft being axially aligned with said pivot point and being linked to said support for movement therewith,

means for urging said cylindrical surface of said second roller means into contact with said cylindrical surface of said first roller means at a point lying on coincident radii of said roller means cylindrical surfaces to latch said first and second roller means,

and trip means for moving said first roller means about said fixed center point to trip said system so that one set of contacts is utilized in the latched position of said system and a second set of contacts is utilized in the tripped position of said system.

11. The improvement of claim 10 wherein a straight line running through the center points of said first and second roller means and said point lying on coincident radii is perpendicular to a straight line running through said center point of said second roller means and said pivot point.

12. The improvement of claim 10 wherein said means for urging said second roller means is a spring, and said first and second roller means are each symmetrical about their respective center points.

Claims

1. A trigger mechanism comprising a first roller means defining a cylindrical surface mounted for rotation about a fixed center point of said cylindrical surface, a second roller means mounted on a movable support and having a cylindrical surface and a center point of said last-mentioned surface, said movable support being mounted for pivotal movement about a pivot point spaced from said center point of said second roller means, means for urging the cylindrical surface of said second roller means into contact with the cylindrical surface of said first roller means at a point lying on coincident radii of said roller means to latch said first and second roller means, said first and second roller means being dynamically balanced so that when said first and second roller means are latched and subject to dynamic forces of shock, impulse and vibration, forces on either side of the center point of each roller means balance out to avoid rotation of the roller means, and trip means for moving said first Roller means about said fixed center point to trip said system.

2. A trigger mechanism in accordance with claim 1 wherein said means for urging said second roller means is a spring, said first and second roller means are each symmetrical about their respective center points, and said second roller means is mounted for rotation about said second roller means cylindrical surface center point.

10. In a rotary electrical switch having a first set of stationary contacts and a second set of stationary contacts with a switch shaft carrying a third set of movable contacts for contacting said first set of contacts in one position and said second set of contacts in a second position when rotated about said shaft axis, the improvement comprising, a first roller means having a cylindrical surface mounted for rotation about a fixed center point of said cylindrical surface, a second roller means mounted for rotation on a movable support and having a cylindrical surface and a center point of said surface about which said second roller means is free to rotate, said movable support being mounted for pivotal movement about a pivot point spaced from a center point of said second roller means, said switch shaft being axially aligned with said pivot point and being linked to said support for movement therewith, means for urging said cylindrical surface of said second roller means into contact with said cylindrical surface of said first roller means at a point lying on coincident radii of said roller means cylindrical surfaces to latch said first and second roller means, said first and second roller means being dynamically balanced so that when said first and second roller means are latched and subject to dynamic forces of shock, impulse and vibration, forces on either side of the center point of each roller means balance out to avoid rotation of the roller means, and trip means for moving said first roller means about said fixed center point to trip said system so that one set of contacts is utilized in the latched position of said system and a second set of contacts is utilized in the tripped position of said system.