US2190847A - Switch plate - Google Patents

Description

Feb. 20, 1940. 1.. PERSONS SWITCH PLATE Filed May 16, 1936 4 m m 2% 4 E 5 r E r W A P &

Patented Feb. 20, 1940 UNITED STATES SWITCH PLATE Lawrence M. Persons, St. Louis, Mo., assignor, by memo assignments, to Automatic Control Corporation, St. Louis, Mo., a corporation of Delaware Application May 16,

11 Claims.

The present invention relates to a switch plate and, in particular, to one that allows a certain amount of movement of the fixed contact and which will effectively break any weld that may occur when the switch is open.

It is an object of the invention to provide a switch of this kind operable to transmit relatively high .currents with a minimum of mechanical power.

It is a further object of the invention to provide a switch of such low mechanical power requirements that will break any weld that may be formed when the switch is closed.

It is a further object of the invention to provide a switch plate of this type that will permit a controlled movement of the fixed contact and which, in such movement, will set up internal stresses that will tend to move the contact point in a direction different from that produced by the movement of the moving contact lever.

It is a further object of the invention to provide a device producing such stresses in a direction to peel apart any weld that may be pro duced.

It is a further object of the invention to provide a switch plate that will set up such stresses, principally about an axis at an angle, preferably 90, to the axis of the movement of the movable contact plate.

It is a further object of the invention to provide such a switch plate, permitting the described movement of the fixed contact, which will distribute the bending actions so as to avoid permanent deformation.

It is a further object of the invention to provide a switch plate that will permit ready movement of the switch plate with the movable contact to a predetermined point, after which the movement is resisted by the production of an increasing amount of potential energy in the plate until this energy exceeds the resisting force joining the contacts, and causes them to break apart.

It is a further object to provide a switch plate 45 of this kind having preformed bends therein of such nature that, upon a tendency of the material to relieve such bends, no deleterious effect will be produced in the switch.

In the drawing:

Fig. l is an elevation of the switch, open.

Fig. 2 is an elevation of the switch as the contacts first come together.

Fig. 3 is an elevation of the switch with the contacts in finally closed position.

Fig. 4 is a section on the line 4-4 of Fig. 1.

Fig. 5 is a section on the line 5--5 of Fig. 2.

Fig. 6 is a section on the line 6--6 of Fig. 3.

Fig. 7 is a horizontal section on the line 1-1 of Fig. 1.

1936, Serial No. 80,090

Fig. 8 is a perspective view of the switch plate per se.

The switch plate generally indicated at 10 may be mounted on a suitable base element II, as desired. This base Ii may be of insulating ma- I terial. The switch plate In is of U-shaped configuration and includes a contact leg l2, a fixed leg l3, and a connecting portion It. The plate is made of some elastic tempered material, such as bronze, so as to be resilient. The leg I3 is 10 secured to the base II by suitable means, such as the rivets IS. A contact element i6, preferably with a curved top surface, is secured to the free leg i2 01' the switch plate. An electric lead I1 is connected to the leg l3 of the plate. As II is shown, the connecting member II is turned up at an angle, preferably a right angle, to the plane of the two legs of the switch plate, and forms a bend B with the leg l2 and a bend B with the leg l3.

Cooperating with the contact I6 is a. contact l8 mounted upon a pivoted switch blade I8. This blade may, if desired, include an insulating portion 20. The. entire switch blade is pivoted as at 2| to some fixed part of the device 22, such as a continuation of the base H. A second electric lead 23 is connected to the blade I9, as is shown.

Beneath the base II is a magnet 24 secured to the base by the rivet l5. Adapted to be brought into the field of this magnet is an armature 25 having a depending portion 26, the armature forming a continuation of the switch blade IS. The action of the magnet on the armature provides a snap-action for the switch. Any other type of snap-action could be employed.

In the operation of the device, the movable contact I8 is brought to the fixed contact l6 by movement of the switch blade l9 about its pivot 2|. When the switch is open, as shown in Figs. 1 and 4, the leg l2 extends somewhat above the surface of the base II and is held in this position by the formed shape of the metal. This lostmotion space is produced by providing the bend B further up on the connecting member it than the bend B. As the switch blade I9 descends, the contact l8 reaches the contact l6, as is shown in Figs. 2 and 5. In this position, no movement has been imparted to the movable leg l2 of the switch plate i0. 50

Further descent of the blade l9 forces the contact l6 down until the leg l2 rests against the base II. The latter part of the switch blade motion occurs with a snap-action by the eflect of the magnet 24 on the armature 25 of the blade i9. This causes a slight deformation of the leg l2 from its original angular relation to the connecting portion it. This action may be considered as a pivoting about the axis defined by the bend B between the leg l2 and the connecting no portion I4. The result is that the or al angle between these elements is increased. 'It will be observed that this axis B is at right angles to the pivotal axis 2I of the switch blade I9.

When the switch seeks to open, it may be that contacts are welded or otherwise held together. In opening, the switch moves backwardly' from the position shown in Figs. 3 and 6 to that shown in Figs. 2 and 5, and finally breaks. In moving from the position of Fig. 3 to that of Fig. 2, the motion is comparatively free of any resistance by the blade itself. The contact I6 may follow the contact I8 with only the resistance of the magnet or snap-action mechanism. This permits the switch to get a "running sta before it begins to break the weld. The amount of this running start is determined by the clearance between the leg I2 and the base II. If the weld is not broken by the time the switch reaches the position of Fig. 2, a further withdrawal of the contact I8 lifts the contact I6, which will tend to pivot the leg I2 about its axis B. This pivotal action is resisted by the structure of the metal itself, since any movement of the leg I2 relative to the connecting portion I4 produces a deformation of the switch plate, owing to its inherent resiliency. The switch plate III will yield and permit lifting of the leg I2 until suillcient resistance is produced in the nature of potential energy stored up in the switch plate to be greater than the strength of the weld joining the contacts.

The movements in the switch plate as the contact l6 follows the contact I8 may be analyzed into two main groups. The first group consists in the pivotal movement of the leg I2 about the connecting portion I4, and a division of this with pivotal movement of the connecting portion I4 about the fixed leg I3. This group of movements is about the axes B and B, and it permits the vertical lifting of the contact I6. As the contact I6 lifts, it seeks to bend the leg l2 upwardly toward the connecting portion I4 about the axis line formed by the junction of said leg and said portion. This bending action is resisted by the inherent resiliency of the plate I0, and resolves itself, within the leg I2 and the portion I4 into opposite forces, the one in the leg acting downwardly to force the leg counterclockwise in Fig. 4, and the other in the portion I4 acting outwardly to force the portion clockwise. This latter is necessarily transmitted through the portion I4 to its connection with the fixed leg I3, and, in turn, tends to unbend the portion I4 about the said leg I3. The result is that the lifting of the contact IB resiliently further bends the leg I2 about the portion I4, and resiliently unbends the portion I4 about the leg I3. This action, being substantially equal and opposite, overcomes the efi'ect of the metals tendency to right itself from the two bends. In other words, by normal fatigue, metal tends to remove any bends. This tendency would be aggravated by the pivotal action of the arm I2 about the portion I4 in the position of Fig. 6 (or by the oppositemovement if the portion I4 were turned down instead of up, as it may be). With an equal and opposite bend in the other leg, this aggravating effect is nullified. Even without it, however, there is a normal tendency of deformed metal to straighten out. In the present device, even if the bends B and B straighten, since the plate is homogeneous, and the bends alike, they will operate together, and the only result will be a change in the relative position of the portion I4, with no change in the position of the contact I2.

This is an important feature of the invention, since, in previous switches, having no compensating bends, there have occurred prohibitively serious displacements of the contact after the passage of only a few weeks.

/ Since these two bending actions of group one are substantially the same, a detailed analysis of one will sumce for both. Although this. group relates to the lifting of the contact I6, it also has a lateral force component. During the lifting of the leg I2 about its axis of bend with the portion I4, the contact I6 moves in an arcuate path about said axis. As shown, the axis of this travel is at a right angle'to the axis of travel of the movable contact I8, although the invention is not limited to this exact angle. In travelling in such an arcuate path, the contact I6 remains at a constant distance from the bend. However, the travel of the contact I8, as seen in Figs. 4-6, is in a plane coincident with the are at only one point. As the contact I8 lifts, it becomes more distant from the bend, resulting in drawing away from the contact I6. In other words, the contact I6 is, in effect, drawn laterally from the contact I8, and, at the same time, is rocked rela tive thereto, resulting in a peeling action. This combination of actions is effective in tending to break away welds between the contact.

In recapitulation of the movements of group one, they may be said to include the following: (1) the running start effect, (2) the uplifting eifect distributed between the two horizontal bends between the respective legs and the conv necting portion, which uplifting effect stores an increasing amount of resistant potential energy in the plate that tends to break the contacts, and (3) the laterally acting forces resulting from the arcuate path of travel of the legs about their bends that draws the contact I6 sideways from and across the surface of the contact I8, and rocks it thereon.

The movements of group two take place about an axis through the connecting portion I4. As heretofore noted, and referring to Figs. 4-6, the contact I6 travels in an arcuate direction about its bend, whereas the contact I8 travels, as respects these views, vertically. If the bend between the leg I2 and the portion I4 were unmovable, the entire stress of the lateral pull by the moving contact I8 would have to be absorbed in tension in the leg. However, it is desirable that provision be made to avoid this. In the present structure, the resiliency of the connecting portion permits it to bend about an axis that may be consideredas being the axis of the U. This permits the contact I6 to move toward the pivotal axis 2I, or away from it. However, this movement is resisted by the inherent resilience of the connecting portion, and potential energy of resistance to bendingor righting energy-is stored in the portion I4 in an amount increasing as the bend increases. This righting energy produces lateral forces seeking to break the contact I6 from the contact I8, as will be evident. These lateral forces cooperate to peel the contact I6 from the contact I8.

It will be understood that these various forces work together, so that the final action is a resultant of all of them. The plate may be designed to leave any of them out, but it is preferable that they all are present. The particular angle between the portion I4 and the legs is immaterial, and a different angle merely changes the direction of the forces of group two. The direction of the axes of bend is most eficient at 90 to the axis 2 I, but the device will operate at other angles. The axis of the movements of group two is not necessarily coincident with the U-axis, since, in any event, it produces a component thus coincident, and only changes the distribution of the forces.

It is to be observed, further, that these various forces are produced by the plate itself. They could be produced by outside spring means and separate pivots, but only at the cost of simplicity, efiiciency, and cheapness. It is immaterial which way the portion It extends relative to the legs, whether upward or downward, since the effect is the same for both. The plate is flexible, and yields with comparative freedom to the movements of the contact I8. In so yielding, it sets up these internal stresses acting in the directions noted that peel the contacts apart instead of pulling them apart. Such peeling reduces the energy required for the separation, and yet there is provided a switch that can carry a high electrical load. Hence, it is of great value in such applications as thermostats, wherein the expanding element has low mechanical power that must control a high current circuit.

In the claims to follow, the expression "planar development is used in its technical sense to mean the imagined bending of one surface, without stretching any one element, to fit upon a plane.

What I claim is:

1. In a switch device, a base, a switch plate comprising a resilient element U-shaped in planar development, one leg of which is secured to the base, a contact on the other leg, and the connecting portion being turned up at an angle to said legs, said connecting portion extending outwardly from the secured leg, laterally, and inwardly to the other leg, so as to extend outwardly in the same direction from both legs.

2. In a switch device, a base, a switch plate comprising a piece of resilient material of U- shape in planar development, one leg of which is secured to the base, a contact on the other leg, said other leg being spaced from the base, and the connecting portion being bent at substantially a right angle to the legs, and extending outwardly from the secured leg, laterally, and inwardly to the other leg.

3. In a switch device, a base, a first contact pivotally mounted for movement to operate the switch, a second contact, a supporifi'or'the second contact, said support including a first part upon which the contact is mounted, a second part supporting the first part for movement of the first part generally in a first plane, said plane being parallel to the pivot axis of the first contact, and a third part supporting the second part for movement in a plane at an angle to the first plane.

4. In a switch device, a base, a resilient switch plate, a contact, means mounting the switch plate on the base, said plate having a portion resistingly movable generally in a plane intersecting the base, and a portion resistingly movable in a plane parallel to the base, the contact being mounted on one of said portions, which aortion is in turn supported by the other por- 5. In a switch, a resilient switch plate U-shaped in planar development, the bight portion of which is turned out of the plane of each leg. a base,

means connecting one leg of the plate rigidly to the base, the other leg being free. whereby said other leg may move relative to the fixed leg, and a contact on said free leg.

6. In a switch device, a resilient switch plate U-shaped in planar development, the bight portion of which extends outwardly from one leg, laterally, and inwardly to the other leg, a base, means connecting one leg of the plate rigidly to the base, the other leg being free, a contact on said other leg, the connecting portion between said legs being bent at an angle to the legs, a switch lever having a contact adapted to close with the contact on the plate, said lever being pivoted about an axis parallel to the legs of the plate.

7. In a switch device, a base, a contact, means supporting the contact for resiliently resisted displacement substantially in a first plane, means supporting the first supporting means for resiliently resisted displacement substantially in a second plane at an angle to the first plane, and means supporting said second supporting means for resiliently resisted displacement.

8. In a switch device, a base, a contact, means supporting the contact for resiliently resisted displacement in a plane perpendicular to the base, a second means supporting the first supporting means for resiliently resisted displacement in a plane substantially parallel to the base, and a third means supporting the second supporting means for resiliently resisted displacement in a plane perpendicular to the base.

9. In a switch device, a base, a contact, means supporting the contact for resiliently resisted displacement in a first plane perpendicular to the base, a second means supporting the first supporting means for resiliently resisted displacement in a second plane substantially parallel to the base, a third means supporting the second supporting means for resiliently resisted displacement in a third plane perpendicular to the base, and a second contact, means movably joining the second contact to the base for relative movement between them in a plane perpendicular to the base but at an angle to the three previously mentioned perpendicular planes.

10. In a device of the kind described, a first contact, a base, a homogeneous resilient metallic element U-shaped in planar development, the bight portion extending outwardly from one leg,

laterally, and inwardly to the other leg, one leg of which is secured to the base and the other leg of which resiliently supports the first contact above the base, the connecting portion between said legs being bent at an angle thereto, a magnet adjacent the base, a movable switch blade, a second contact on said blade adapted to close with said first contact, an armature on said blade adapted to come into the field of the magnet as the switch approaches closed position, and said magnet thereupon drawing the armature and both contacts until the first contact rests on the base.

11. In a switch device, a base, a switch plate comprising an element U-shaped in planar development, having resilient legs, and a connecting g5 wardly from one leg, laterally, and inwardly to the other leg.

; LAWRENCE M. PERSONS.

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