US2202294A

US2202294A - Control apparatus

Info

Publication number: US2202294A
Application number: US94411A
Authority: US
Inventors: Paul B Leonard
Original assignee: Ranco Inc
Current assignee: Robertshaw US Holding Corp
Priority date: 1936-08-05
Filing date: 1936-08-05
Publication date: 1940-05-28
Anticipated expiration: 1957-05-28
Also published as: USRE21622E

Description

y 1940- P. B. LENARD 2,202,294

CONTROL APPARATUS Filed Aug. 5, 1936 3 Sheets-Sheet 1 INVENTOR LONAQD BY WflJ-TM ATTORNEY y 8, 1940. P, B. LEONARD 2,202,294

CONTROL APPARATUS Filed Aug. 5, 1936 3 Sheets-Sheet 2 INVENTOR 404 3,450A/AQ0 BY W 4 ATTORNEY May 28, 1940. P. B LEONARD 2,202,294

I CONTROL APPARATUS Filed Aug. 5, 1936 3 Sheets-Sheet 3 57.]1. 1 '9. Z 5. INVENTOR Pwz. ELEM/App W64}? ATTORNEY Patented May 28, '1940 CONTROL APPARATUS Paul B. Leonard, Columbus, 0hio, assignor to Ranco Incorporated, Columbus, Ohio, a corporation of Ohio Application August 5, 1936, Serial No. 94,411

24 Claims.

My present invention relates to switches and more particularly to an electric switch.

One of the objects of my invention is to provide a switch in which the break, or separation, between the contacts is relatively wide in relation to the movement of the actuating mechanism.

Another object is to provide a constant, high, contact pressure at the instant before separation of the contacts, to eliminate chattering and subsequent arcing of the contacts.

A further object is to provide a snap action device that operates through the resultant force components of opposing springs to produce positive snap action without the usual graduating tendency.

Other and further objects and advantages will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred form of embodiment of the present invention is clearly shown.

Fig. 1 is a side elevational view of the switch;

Fig. 2 is a front elevational view of the switch having the housing cut away and the adjustment spring removed;

Fig. 3 is an enlarged front view of the snap mechanism;

Fig. 4 is an enlarged side view of the snap mechanism with the contacts in the closed position;

Fig. 5 is a similar view of Fig. 4 with the contacts in the open position;

Fig. 6 is a diagrammatic view of the mechanism in the closed position with spring 2| removed;

Fig. '7 is a view similar to Fig. 6 with spring 22 removed and spring 2| in place;

Fig. 8 is a diagrammatic view of the mechanism with spring 2| removed and shown in the position at the instant before the separation of the contacts;

Fig. 9 is a similar view to Fig. 8 with spring 22 removed and spring 2| in place;

Fig. 10 is a diagrammatic view of the mechanism with spring 2| removed and with the contacts in an open position, and,

Fig. 11 is a similar vir to Fig. 10 with spring 22 removed and spring 2| in position.

The embodiment of the switch as shown in the (01. zoo-gas) upper end, which is clamped to the base plate I! by a removable collar I, held in place by screws 3|. This collar I does not clamp the housing I! so tightly that it can not be turned manually, but neither is there any appreciable end play. 5 This attachment allows rotation of the housing l8, together with the enclosed bellows ll, without changing the relative position of the bellows IT to the associated mechanism. An elbow IE or other convenient means is used to engageably at- 10 tach the bellows I'I to the pressure system, which may be an air or steam line, or other type of conduit, or the bellows may be connected to a bulb and tube as is familiarly used in refrigeration controls. A change of pressure within the bell5 lows l1 acts to vary its length, which variation is transmitted to the snap mechanism by a push rod I5.

Rod l5 acts against a lever 84, which is U- shaped at the lower end, at the bearing point 32. 20 The bearing 32 is formed by a depression in the lever M to receive the conical end of the rod I5. The lever M is the actuating lever for the switch mechanism and is pivoted at its lower end on the knife edge bearing of a rod 23, which in cross sec- 5 tion resembles a sector of a circle. The rod 23 is set in apertures 26 formed in the bracket 5. These apertures 26 are of similar shape to the cross section of the rod 23. The bracket 5 is sub stantially U-shaped at its lower end and is perso manently attached to the base plate IS. The bearings 36 in the actuating lever M are also in the shape of a sector of a circle, but with a greater degree are than is used in the bracket 5. This additional arc allows the necessary space for the 5 movement of the lever M with respect to the bearing rod 23. The lever I4 is held tightly against the push rod 5 by the tension of a spring I3, attached to the lever M at 3'! and adjustable through the screw |2 which turns in a plate 33. It will be noted that the plate 33 is provided with a projection 34 that is slidably engaged with a slot 35 in the frame 20. This engagement allows longitudinal adjustment of the plate 33 and attached spring l3 by the action of the screw |2, without the plate 33 turning, or otherwise becoming disengaged from the spring l3. The screw adjustment l2 varies the tension of the spring on the actuating lever l4 thereby changing the pressure exerted through the associated pin I5 on the bellows I1. This change in pressure varies the adjustment of the device. The projection 34 of plate 33 extends through frame 20, and is used as an indicator for the setting of the spring I3. 66

The lever |4 cooperates at its upper end with a lever, or movable contact element ii, that carries the movable contacts it loosely set in an insulating memberil, attached to the contact element The movable element it engages, on closing, with the fixed contact member 8, which may be connected to the electrical circuit by associated lugs l. The contact 8 is set in insulating .material 2 which is secured to the bracket 5 by the member 24. The lower end of movable element N forms a knife edge which is pivoted on the lever M at the bearing M. This construction may be more clearly seen in the enlarged views shown in Figs. 3, 4 and 5, where the relationship of parts is well illustrated.

The upper or free end of lever i4 is connected to the free end of a toggle, or flipper member 8 by the spring 2|. its upper, pivoted end in a knife edge or V-shaped bearing 28 which is formed in the fixed bracket 5. The lever II is also connected to the free end of the toggle 6 by the spring 22. The movement of the free end of the toggle his limited and adjustable in both directions by the screw stops 3 and 4. Stop 3 is mounted on the lever l4; this particular construction is not limiting, but merely the most obvious method of manufacture. Stop 4 is screwed through the member 24 which is associated with the support bracket 5 by rivets. The screw 3 (see Fig. 3) is engaged through the threaded hole 3 in lever M. This hole 3' is in the elongated spring slot which provides for a tight thread at all times without the use of a lock nut. Screw 4 is similarly engaged. These two stops 3 and 4 furnish the differential range adjustment for the instrument. It is evident that by limiting the free movement of the toggle S that the differential of the device may be varied within any reasonable limits.

The pivotal mounting of member H on lever I4 is important to the success of my invention. As the lever l4 shifts in position, as occasioned by movement of the bellows ill, the fulcrum 21 for lever moves towards the dead center position of the toggle member t and the movable element I I. This action tends to reduce the bellows movement necessary to secure operation of the snap mechanism.

The pivotal mounting of lever ii on lever M has another advantage from an electrical standpoint. As the lever i 4 moves, its fulcrum point 21 also moves, but since this fulcrum point 21 is not on the same center as the fulcrum point 36, of the lever H, the fulcrum 27 described an are as it moves. This path of movement rubs, or wipes the contacts Ml against the contacts 8 which keep the surfaces of the contacts from sticking just before the separation of the contacts.

At the start of the closing cycle, the switch is in the position shown in Fig. 5 with the projection 29 serving as a stop for the outward movement of lever As lever l4 moves to close the switch, due to a decrease in bellows pressure, the stop 29 on the lever 04 moves lever clockwise so that it approaches its dead center position. This movement simultaneously displaces the spring 2| that is attached to the lever l4 and to the flipper 6. When spring 2| and flipper 6 pass the dead center position, the spring 2| snaps the flipper 6 from stop 3 to stop 4; this movement also carries the spring 22 to the right of the dead center position for lever i, and lever II will snap from stop 29 to the contacts 8 and the switch will be closed. This snap ac- The toggle 6 is supported at a tion of lever ii and flipper 6 is substantially instantaneous. At practically the same instant lever M will follow through, due to the change in pull of spring 2| caused by the change in the position of flipper 6 from stop 3 to stop 4, to hit against the lever It and greatly increase the closing contact pressure.

On opening the device, the spring 2| overcomes the spring 22 to snap the toggle open before the lever |4 contacts the projection 25 on lever neither is the point 29 in contact with the lever II. This allows for additional movement of free travel on the separation of the contacts. The projection 25 is placed on lever II to engage lever M if for any unforseen reason the contacts do not separate. This is an added measure of safety. In this event, the direct contact of the levers H and I4 cooperate to force the separation of the contacts. It will be noted that in this position the pressure within the bellows is acting directly on the lever through lever l4 without any intervening members being actuated. Similarly, on the closing of the device, the actuating member |4 through its integral projection 28, bears or acts directly on the movable member H. Thus, during closing of the switch, the action is direct from the bellows through lever N to the movable member H without the intervening action of the toggle mechanism, which does not come into operation until the movable member passes its dead center position. At this point the flipper 6 is snapped through dead center to snap the movable member ii to the closed position. It will be noted that the contact separation is relatively small at the instant before the closure of the contacts, whereas the contact separation is relatively great on the opening. This relation between the contacts is very desirable as a wide brea prevents arcing, etc, when the switch opens.

The leverage ratio of the actuating lever I4 is relatively high and may be utilized due to the construction of the switch, which does not have a graduating tendency at the instant before separation of the contacts but maintains the high contact pressure until the contacts are separated by the snap mechanism. Therefore, the movement of the upper end of the actuating lever I4 is relatively large compared to the movement of the lever or bellows end of the lever. Thus for a short bellows movement a wide separation of the contacts may be obtained.

The snap action of the device is acquired by the action of the two snap springs 2| and 22 cooperating with the movable contact lever H, the actuating lever l4, and the flipper 5. The spring 22 connects the movable contact member II to the flipper member 6. The tension of the spring 22, through its horizontal component of force, tends to press the movable contacts ID to the fixed contacts 8, in the closed position of the switch. The spring 2| connects the flipper 6 to the actuating member M. The spring 2| is preferably heavier than the spring 22.

Figs 6 to 11, inclusive, illustrate diagrammatically the action of the springs and toggles as the switch is actuated for separation of the contacts. In Fig. 6 the contacts are shown in closed position, and for the sake of clarity, spring 2| is removed, since springs 2| and 22 superimpose on one another in the side view of the switch. Fig. '7, therefore, is an identical view to Fig. 6, but showing the spring 2| and omitting spring 22. Figs 8 and 9 are similar views at the instant before separation of the contacts.

As the actuating member It moves counter clockwise from the position shown in Figs. 6 and 7, due to the expansion of the bellows, it displaces the spring 2| from the position shown in Fig. 7 to the position shown in Fig. 9. Although at the time lever l4 moves the spring 2| beyond its dead center position, with respect to flipper 6, the flipper 6 is not' displaced at that instant due to the opposing force of spring 22. At the instant that the horizontal component of spring 2| exceeds the horizontal component of spring 22, the flipper will be snapped from the stop 4 to stop 3. Figs 8 and 9 show the position of the elements at the instant that the force of spring 2| is equal to the force ofspring 22. At the instant that the force of spring 2| overcomes the force of spring 22, the flipper 6 is snapped through its own dead center and the elements are moved from the position shown in Figs. 8 and 9 to the position shown in Figs. 10 and 11. Let us assume that the switch is in the position shown in Figs. 6 and '7 and, for example, spring 22 has a horizontal force component. of ten pounds, the spring 2| having a horizontal force component of five pounds in the opposite direction. The resultant force component tending to keep the flipper 6 in its original position against stop 4, will be flve pounds. As the spring 2| is displaced to the position shown in Fig. 9, its horizontal force component increases to a point where it is ten pounds in the opposite direction of the ten pound component of spring 22. This gives a resultant force of zero of the flippers against stop 4.

The instant that the component of force of spring 2| exceeds ten pounds, it will snap the flipper 6 through the dead center position of the latter. Due to this movement of flipper 5, the angularity between the flipper 6 and the spring 2| is constantly increasing to produce a correspondingly constant increase in the horizontal force component of the spring 2|. This constantly increasing component of force of spring 2| insures contact separation, which separation is constantly increasing in speed from the very start to the completion thereof.

The contact pressure of contact ID on contact 8 is unchanged until snap action occurs. Fig. 8 illustrates very clearly why the contacts have a maximum pressure even at the instant before separation, for it will be noted that the horizontal component force of spring 22 at its upper end as exerted on contacts I is unchanged during the movement of spring 2|.

The present switch presents a, device with positive spring action to assure constant, high, contact pressures and positive make and break of the points, thus providing perfect switch operation, entirely devoid of chattering or arcing. The movable contacts l0, due to their loose engagement with the insulating member 9 having a slight wiping action on closing. This is also advantageous for perfect operation.

My present invention has numerous distinct advantages over snap action devices of theusual design. It is a well known fact that switches and the like, having small differentials in their operating ranges usually have a very limited movement between the switch points.

My invention differs from the usual switch in that compensating adjustments, automatic in character, are provided, that not only allow a very small differential range, but also allow an exceptional break, or movement of the points.

This relatively large break is made possible by the lost motion and movable fulcrum features'of the invention. In order that this lost motion," which allows wider separation of contacts, does not increase the difierential, the compensating movable fulcrum is provided for the movable contact member. The movement of the fulcrum points disposes the lever in position to snap with no additional travel of the bellows. In other words the displacement of the fulcrum, for the movable member, takes up the lost motion.

Although the description of my invention is d rected to electrical switches, it is to be understood that the principles involved should not be limited to use in these specific devices. It is evident that the benefits derived from the described mechanism, namely, a relatively large movement of the snap member for a relatively small movement of the actuating medium, would be well adapted for use in a number of devices completely divorced from electrical switches. The inherent advantages involved would, for example, be well employed in valves of the snap action type, for use with fluids of various kinds, whether such valves or mechanisms are actuated by the described bellows or by such other well known mediums as bimetal, rod and tube expansion elements, etc.

In fact, the described mechanism will be extremely useful in any type of device where a strong, definite action or movement is required under low differential conditions.

While the form of embodiment of the present invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

I claim as my invention:

1. In a snap action device, a movable element, a flipper fulcrumed at one end, a spring connecting the movable element and the flipper, an actuating member, a spring connecting the actuating member to the flipper, stop means disposed to contact the free end of the flipper and means for moving the actuating member.

2. hi a snap acting device, relatively fixed and movable elements, a snap member, an elas tic means cooperating with said movable element and said snap member, an actuating member, a resilient means connecting said actuating member and snap member, said snap member, resilient means and actuating member having a dead center position, said actuating member being so disposed in relation to the snap member that when the dead center position of the snap member is passed that both the elastic means and the resilient means react cooperatively to move the movable element.

3. A snap acting device comprising, a movable element to be actuated, a flipper, a spring connecting the movable element and the flipper, an actuating member, a spring connecting the actuating member to said flipper and means for moving the actuating member.

4. A snap acting device comprising a movable element to be actuated; a flipper fulcrumed at one end; a spring having one end thereof connected with the free end of the flipper and having the other end thereof connlected with the element, said spring, flipper and elel0 ment having a dead center position; an actuating member; a spring connected with the actuating member and with the free end of said flipper, said last spring, actuating member and flipper having a dead center position and said i last spring being adapted to move the flipper beyond its dead center position with respect to the first spring, flipper and first element when the second spring is moved beyond its dead cen ter position relative to the flipper and actuating member; and means for moving the actuating member.

5. In a snap acting device, a movable element to be actuated, a flipper fulcrumed at one end; a spring having one end connected to the free end of the flipper and having the other end connected with the element, said spring, flipper and element having a dead center position, an actuating member carrying a fulcrum for said movable element; a second spring connected with the actuating member and flipper, said flipper, actuating member and spring having a dead center position, said actuating member being adapted to move the movable element and the second spring toward the dead center positions; and means for moving the actuating member.

6. In a snap acting device, a movable element to be actuated; a flipper fulcrumed at one end; a spring having one end connected to the free end of the flipper and having the other end connected with the element; said spring, flipper and element having a dead center position; an actuating member carrying a fulcrum for said movable element; a spring connected with the actuating member and with the free end of said flipper, said last spring, actuating member and flipper having a dead center position, said actuating member being adapted to move the movable element toward its dead center position, said last named spring being adapted to move the flipper beyond its dead center position with respect to the first spring, flipper and first element when the second spring is moved beyond its dead center position relative to the flipper and actuating member; and means for moving the actuating member.

'7. In a snap acting device, a movable element to be actuated; a flipper fulcrumed at one end; a spring having one end connected to the free end of the flipper and having the other end connected with the element; said spring, flipper and element having a dead center position; an actuating member carrying a fulcrum for said movable element; a spring connected with the actuating member and with the free end of said flipper, said last spring, actuating member and flipper having a dead center position, said actuating member being adapted to move the movable element toward its dead center position, said last named spring being adapted to move the flipper beyond its dead center position with respect to the first spring, flipper and first element When the second spring is moved beyond its dead center position relative to the flipper and actuating member; and means for moving the actuating member.

8. In a snap acting device, relatively stationary and movable elements to be controlled; an actuating member, said movable element adapted I to be limited in its movement in one direction by the stationary element and adapted to be limited in its movement in the other direction by the actuating member, said movable element and actuating member being spaced from one another for free travel of the movable element; a flipper; a spring connected with the flipper and the movable element, said second spring, flipper and element having a dead center position, said spring being adapted to snap actuate the movable aeoaaoe element when the spring, flipper, and movable element are moved beyond their dead center position; and a second spring connecting the flipper and the actuating member, said second spring, flipper and element having a dead center position, said second spring being adapted to snap actuate the flipper beyond the dead center position of said first spring, flipper and movable element when the actuating member moves beyond its dead center position with respect to the flipper and second spring.

9. In a snap action device, a plurality of levers, yielding means interconnecting one of said levers to each of two other levers, said yielding means having unequal and opposing force components, means to actuate one of said second levers to increase the force components of one of said means whereby snap action occurs when the increasing force component exceeds the stationary force component of the other means.

10. In a snap acting device, a plurality of pivoted elements having their free ends disposed oppositely from one another, a spring connecting said elements for urging the free ends in one direction when the spring is in one position, a second spring connected to one of said elements for moving the elements in the opposite direction, and means for increasing the force of the second mentioned spring on the one element for overcoming the force of the first mentioned spring on the element.

11. In a snap acting device, a movable element, resilient means for urging the element in a certain direction, said element and means being so disposed with respect to one another that the component of force of said means acting upon the element decreases when the element is moved in opposition to said means, a spring tending to move said element in a direction opposite the said certain direction, and mean for moving the spring to increase the force of said spring to a point at which it overcomes the force of the first mentioned means.

12. In a snap acting device, a first movable member and a second movable member; a fixed support for the first movable member; an overcenter spring interconnecting the said movable members; an operating member; a fulcrum for said second movable member carried by the operating member; a spring interconnecting the operating member and said first movable member for actuating the first movable member to move the first mentioned spring over dead center on movement of the operating member to cause snap action of the first and second movable members; and means for actuating the operating member.

13. In a snap acting device, a movable member; a snap member fulcrumed at a fixed point; elastic means cooperating with the movable member and the snap member, said movable member having a dead center position with respect to the elastic means and the snap member; an actuating member, said actuating member carrying said movable member; resilient means cooperating with the snap member and the acresilient member for moving said element from one of the extreme positions to an opposite extreme position including a second resilient member for urging the first resilient member toward the second mentioned extreme position with respect to the element; and means for reversing the directions of force of the second resilient member on the first member for moving said first member in opposite directions.

15. In a snap acting device, an element movable between two positions, said element having a pivot; a resilient member connected to the element for biasing said element in either of said positions, said member being movable to a position on either side of a line through the pivot and the point of connection of the member and element; means, including a second resilient member, for yieldingly moving the first resiiient member from one side of the said line to the other; and means for increasing the yielding effect of the second resilient member on the first member for moving said first member.

16. In a snap acting device, a movable element having a pivot; a spring connected to the element and being movable to a position on either side of a line through the pivot and the point of connection of the spring and element for actuating the element; means for moving the spring, including, a member connected to the spring and biased in one direction by the spring, and a second spring connected to the member for biasing the member in the opposite direction and means for moving the second spring relative to, the member for increasing the biasing effect of the second spring whereby the member is moved in said opposite direction with a snap movement and moving the first spring therewith.

17. In a snap acting device, a movable element; means for limiting movement of the element between two positions; a translatable resilient member connected to the element; means for limiting movement of the resilient member between two positions; means for translating the resilient member for causing said element to be moved from one of its positions to the other, including, a second resilient member for urging the first mentioned resilient member from one of its said positions to the other; and means for reversing the directions of force of the second resilient member on the first member for moving the first member in either direction.

18. In a snap acting device, a movable element having translatable pivot; stop means for limiting movement of the element in one direction; snap mechanism for moving the element from the stop means, including a spring and a movable member, said spring connecting the element and the member and being disposed so that the moment of force thereof is at an angle with respect to a line from the pivot to the stop means to yieldingly urge the element against the stop means; an actuating member for moving the pivot to increase the angle between the spring and the said line while the actuating member moves in one direction; and means for shifting the spring to a position in which the moment of force thereof is opposite the pre-shifted position thereof for moving the element away from the stop means, said shifting means comprising snap acting mechanism including said movable member actuated by the actuating member after said actuating member moves a predetermined distance in said one direction.

19. In a snap acting device, a movable element; stop means for limiting movement of the element between two opposite positions; a spring connected to the element, said spring being adapted to move the element from one of said positions to the other; a second spring connected to the element for yieldingly retaining the element in either of said positions; and means for actuating the first spring for overcoming the yielding effect of the second spring and move the element to the opposite position.

20. In a snap acting device, an element movable in two directions; a stop limiting the movement of the element in one of said directions and a stop limiting the movement of the element in the other of said directions; means for moving said element from one stop to the other with a snap movement; and means cooperating with said means for moving one of said stops relative to the other stop prior to snap movement of the element in the said one direction for increasing the snap movement of the element in the one direction and for moving said stop relative to the other stop prior to snap movement of the element in the said other direction by said snap means for decreasing the movement of the element in said other direction.

21. In a snap acting device, a pivoted element movable about its pivot in two directions; a stop limiting movement of the element in one direction and a stop limiting movement of the element in the other of said directions; snap acting means actuatable for moving said element from one stop to the other; and a member for actuating the snap acting means, said member being adapted to move one of said stops in said one direction to increase the movement of said element by the snap acting means in said one direction and to move the said one stop in the said other direction for decreasing the movement of the element by the snap acting means in said other direction.

22. In a snap acting device, a pivoted element movable in two directions; a stop limiting movement of the element about its pivot in one of said directions; a movable actuating member, said member having a part for engaging said element for limiting movement of the element in the other of said directions; and snap mechanism operated by movement of said actuating member for moving said element to said limiting part and stop with a snap action.

23. In a snap acting device, a pivoted element movable in two directions; stops limiting the extent of movement of the element in said directions; snap acting mechanism for actuating the movable element; and means for actuating the snap actuating mechanism in opposite directions and for actuating one of said stops for moving the pivoted element toward the other stop when said means is operating the snap acting mechanism in a direction to move the element to said other stop.

24. In a snap acting device, a pivoted element movable in two directions; stops limiting the extent of movement of the element in said directions; snap mechanism for actuating the movable element; a lever carrying one of said stops; and means intermediate the stop and fulcrum of said lever for actuating the snap mechanism.

PAUL B. LEONARD.