US3207868A - Snap action electric switch mechanism - Google Patents

Description

Sept. 21, 1965 c. w. KUHN ETAL 3,207,868

SNAP ACTION ELECTRIC SWITCH MECHANISM Original Filed Feb. 28, 1962 5 Sheets-Sheet 1 30g 30b g 1 iIllllll Sept. 21, 1965 c. w. KUHN ETAL 3,207,868

SNAP ACTION ELECTRIC SWITCH MECHANISM Original Filed Feb. 28, 1962 5 Sheets-Sheet 2 62 44 30g 52 30b 58a, 8

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Sept. 21, 1965 c. w. KUHN ETAL 3,207,868

SNAP ACTION ELECTRIC SWITCH MECHANISM Original Filed Feb. 28, 1962 5 Sheets-Sheet 3 .9 44 548 y 5tk$fl 6 \llllu lull Sept. 21, 1965 c. w. KUHN ETAL 3,207,868

SNAP ACTION ELECTRIC SWITCH MECHANISM Original Filed Feb. 28, 1962 5 Sheets-Sheet 4 36 JR 74f 74a 308 g 1 HH 5 2 2 23 ER 42; sacilfig i%55g 33 48am J gmwko-ma [llll F b 42a 42b 42a Q Sept. 21, 1965 c. w. KUHN ETAL SNAP ACTI ON ELECTRIC SWITCH MECHANISM 5 Sheets-Sheet 5 Original Filed Feb. 28, 1962 United States Patent SNAP ACTION ELECTRIC SWITCH MECHANISM Clarence W. Kuhn, Wanwatosa, and Charles R. Smith, Mequon, Wis., assignors to Cutler-Hammer, line, Milwaukee, Wis., a corporation of Delaware Original application Feb. 28, 1962, Ser. No. 176,354, now Iatent No. 3,135,849, dated June 2, I964. Divided and this application Nov. 14, 1963, Ser. No. 323,701

9 Claims. (Cl. 20067) This application is a division of our application Serial No. 176,354, filed February 28, 1962, now US. Patent No. 3,135,849.

This invention relates to improved snap action electric switch mechanism.

While not limited thereto, the mechanism of the present invention is well suited for use in thermostatic control devices of the kind disclosed in said Patent No. 3,135,849.

The object of the present invention is to provide an improved snap acting switch mechanism which has two stable operating conditions and provides fast make and break contact operation when positively driven from one to another of its stable operating conditions.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate preferred embodiments which will now be described in detail, it being understood that the embodiments illustrated are susceptible of various modifications without departing from the scope of the appended claims.

In the drawings:

FIGURE 1 is a side elevation view of a thermostatic control switch constructed in accordance with the invention;

FIG. 2 is a right end view of the control switch shown in FIG. 1;

FIG. 3 is a view in cross section taken along the line 33 of FIG. 2;

FIG. 4 is a view like FIG. 3 but showing the control switch in another operating condition;

FIG. 5 is a top plan view with a cover removed to show interior mechanism;

FIG. 6 is a view in cross section taken along the line 66 of FIG. 3;

FIG. 7 is a fragmentary view partially in cross section taken along the line 77 of FIG. 3;

FIG. 8 is a view in cross section taken along the line 88 of FIG. 4;

FIG. 9 is a top plan view of a lever assembly used in the control switch;

FIG. 10 is a view showing the parts of the lever assembly of FIG. 9 in exploded relation;

FIG. 11 is a view like FIG. 5 but to smaller scale and with certain mechanism removed;

FIG. 12 is a fragmentary view taken along the line 12-12 of FIG. 3;

FIG. 13 is a top plan view of a part in the switch mechanism;

FIG. 14 shows one operating condition of certain parts used in the switch mechanism of the control switch; and

FIG. 15 is like FIG. 14 but shows the same parts in another operating condition.

Referring particularly to FIGS. 1 to 13, they disclose a preferred and basic form of refrigerator control embodying the invention which comprises a thermal responsive power element 30, an operating mechanism enclosing case 32, and a range adjusting knob 34. This form is a so-called straight range version wherein cut-in and cut-out points are simultaneously adjustable while maintaining the dilferential between such points substantially constant.

Power element 30 is provided with a cup-shaped portion "ice 30a, a pair of side frame portions 3% which integrally join with portion 30a on opposite sides at the upper end of the latter. At corresponding ends portions 30b are provided with integral tabs 300 (see FIG. 5) which extend through slots in a mounting bracket 36 and are upset over the opposite side of bracket 36 to secure the latter in place.

As best shown in FIGS. 3 and 4, power element 30 is provided with a diaphragm 3% which is suitably secured in a sealed relation to the inner wall of the cup portion 30a to form an enclosed diaphragm chamber 38 therewith. A capillary tube 40 penetrates and is sealed to a boss portion 306 which extends downward at one side of the underside of portion 30a. Tube 40, as is well known, is of some definite length and its bore and diaphragm chamber 38 of element 30 are provided with a suitable fill of gas such as Freon (F-22 or F-12) or methyl chloride. Diaphragm 36d is preferably formed in accordance with the teaching of the Smith Patent No. 2,751,935 so that it will move outwardly and inwardly in a linear relation to changes in pressure of the gas in the chamber 38 and tube 40.

A base 42 formed of a suitable molded electric insulating material seats at its lower end against the upper edge of cup-portion 39a on opposite sides between the side from portion 39a and at one end against bracket 36. Tabs 30f struck out of the portions 30b are bent into recesses 42a (see FIGS. 1 and 5) formed in the outer surfaces of the aforementioned sides of base 42 and serve to secure the latter and power element 30 in assembled relation.

A cover 44 formed of a suitable insulating material seats against the upper surface of base 42 and is secured in place by inwardly extending tabs Stig formed along the upper edges of the portions 30b.

A stationary contact 46 is mounted on an arm 43a of stationary contact terminal member 48 (see FIGS. 5 and 11) that seats within base 42 where it is secured by a screw 50. A movable contact 52 is secured in overlying working relation to contact 46 to the free end of a central hollow rectangular portion 54a of a metallic reed member 54 which is of a form best shown in FIG. 13. At its other end member 54 is provided with spaced apart openings to accommodate screws 56 which also penetrate the arm 58a of a terminal member 58 that overlies and contacts the last mentioned end of member 54 to secure the latter and terminal member 58 in place in base 42.

As shown in FIG. 13, member 54 is provided with legs 54b which are spaced apart and extend parallel with the longitudinal sides of the portions 54a. At their outer ends the portions 54b have integral portions 540 that extend inwardly toward a tab 54d integrally formed on the free end of portion 54a. Portions 54c have booked lips 54e that extend generally parallel with the portions 54b.

Reed member 54 is formed to accurate dimensions by suitably blanking the same from thin flat stock of a spring temper material, such as beryllium copper alloy. Mounting recesses for member 54 and terminal member 58 are so formed that when the same are initially secured in base 42 by screws 56 contact 52 will be forced into engagement with contact 46 with some pre-bending of the portion 54a thereby establishing a minimum normal engagement pressure between contacts 52 and 46.

A C-shaped flipper spring 60 has a slot 60a formed therein (see FIGS. 3, 4, 5, 12, 14 and 15) and the tab 54d of member 54 extends therethrough. The portions 540 and 54e of each of the legs 54]) also extend or hook over the web 60b of spring 60 with the portions 54e extending into the slot 66a. The web 6% narrows and terminates at an end 600 that engages in a V-shaped notch 62a formed in one end of a molded drive lever 62. Flipper spring 60 is formed by blanking from thin flat stock of stainless steel which has been suitably heat treated and tempered. The C-shape configuration of spring 60 is imparted in assembling it to the reed member 54 and drive lever 62, but preformed C-shape springs can also be used.

Drive lever 62 at its opposite end is provided with a V-shaped notch 62b that engages on the inner edge 54f of the end portion 54g bounding one end of the central opening 5411 in member 54 to provide a pivot fulcrum point for lever 62. As viewed in FIG. 3, notch 62a is below the plane of member 54 and the forces developed in spring 60 hold the tab 54d in engagement with a lateral stop finger 58d integrally formed with terminal member 58. In such position of member 54 contact 52 is held out of engagement from contact 46 thereby interrupting circuit.

If drive lever 62 is pivoted counterclockwise about its pivot fulcrum at notch 62b the end 60c of spring 60 will move upwardly and be compressed, and the upward component of force exerted by spring 60 on the member 54 decreases as the angle between its ends and the plane of member 54 decreases. A null point is reached where the upward force exerted by spring 60 is equal to the downward force exerted by member 54 due to its aforementioned bending. Any further counterclockwise movement of lever 62 permits tab 54d, and hence portion 54a, to move downwardly to engage contact 52 with contact 46. Before the end 60c moves across the plane of the legs 54b, the force exerted by spring 60 reverses to exert a vertical downward component, and a toggle action takes place causing spring 60 to move rapidly with lost motion the width of its slot 60a, minus the thickness of member 54, to engage along the upper margin of its slot as depicted in FIG. and drive tab 54d downwardly and close contact 52 upon contact 46. In the closed position of the contacts, shown in FIGS. 4 and 15, the force developed in spring 60 applied through the upper side of slot 60:: against tab 54d is added to the aforementioned prebending stress in member 54 to hold contact 52 against contact 46. Overtravel of lever 62 in the clockwise direction is limited by engagement of one of the projections 620 with a tab 580 which overlies such projection.

Assuming that contact 52 is closed against contact 46 as shown in FIG. 4, if drive lever 62 is pivoted clockwise about its notch 62b the end 60c of spring 60 will move downwardly along an arc and be compressed. This increases the force developed in spring 6%), but because of its changing angle relative to the plane of reed member 54the downward vertical component of force exerted on tab 54d is decreased which reduces the contact engagement pressure. When notch 62a is in line with legs 54!) the vertical component of force exerted by spring 60 on member 54 becomes zero. As lever 62 continues to pivot clockwise, the vertical component of force exerted by spring 60 reverses and a position is reached where the upward force exerted by spring 62 on member 54 is balanced by the downward forces exerted by legs 54b and a balance of forces exists. Only the aforementioned prebending stress of member 54 provides contact engagement pressure. Any additional clockwise movement of lever 62 increases the vertical component exerted by spring 60 and legs 54:: will move the distance of slot 66a (less the thickness of member 54) and spring 60 will toggle member 54 rapidly upwardly to move contact 52 from engagement with contact 46. Member 54 is limited in upward travel by engagement of the upper surface of its tab 54d with stop finger 58d which is an integral part of member 58. Similarly, the integral projections 62c on drive lever 62 engage the lower surfaces of recesses 42b, formed in base 42 to limit overtravel movement of the lever in the clockwise direction.

Between drive lever 62 and diaphragm d a lever motion multiplying and range differential adjusting system is interposed. Referring particularly to FIGS. 3, 4, 8, 9 and 10, the motion multiplying system includes a thrust plate 66, a range lever 68, a cut-in lever 70, a cut-out lever 72, a stabilizing leaf member 74 and a biasing spring 76.

Thrust plate 66 bears centrally against the diaphragm 30d, and diametrically opposite legs 66a bear at their arcuate upper ends against the outer arms 686 of range lever 68. Lever 68 bears at its one end 6811 against the edge of a range adjusting cam 78. At the tip of its opposite angularly upward end 6811, lever 68 bears against the lower sides of the levers 70 and 72. Lever 70 pivots against the lower end of an adjusting screw 80, and lever 72 bears at its corresponding end against the lower end of an adjusting screw 82.

Bias spring 76 seats at its upper end in a recess 42d formed in base 42, and terminates at its other end in a coaxial straight end that bears in a recess in the upper surface of cut-out lever 72. The spring 76 develops a counterclockwise torque on lever 72 about its pivot on the end of screw 82.

As best seen in FIGS. 8, 9 and 10, plate 66 and levers 68, 70 and 72 are held together in assembled relation by leaf member 74 which is preferably formed of thin flexible spring stock. Levers 70 and 72 are spot welded to the ends of the outer legs 74a and 741;, respectively, and the plate 66 is spot welded on its upper surface to the end of the central leg 740 of member 74 with the legs 66:: of plate 66 straddling the outer margin of leg 74c. Range lever 68 is spot welded at its end 68b to the intermediate connecting bight 74d of member 74. This assembly is secured and located in base 42 by means of spaced downwardly projecting lugs 42c formed in the base molding which penetrate openings 74c formed in leaf member 74. Oppositely disposed tabs 74 formed in the margin of the latter openings grip the sides of lugs 42a and dig in to prevent withdrawal therefrom. Stabilizing member 74 provides lateral stabilizing for plate 66 and levers 68, 70 and 72 and flexes to permit such plate and levers to move and pivot as required of the lever. The amount of flexing required of member 74 in normal operation is minimized by making the attachments thereto as close as possible to the pivot points of the levers.

As best seen in FIGS. 3, 4 and 9, lever 70 has an angularly upturned portion 70:: which engages on the un der surface of a semi-cylindrical boss 62d formed on drive lever 62. Lever 72 has a generally C-shaped free end 72a which overlies the boss 62d in a recess 62c formed in lever 62 and engages with boss 62d to pivot lever 62 clockwise under decreasing power element pressure changes as will hereinafter be explained.

Range adjusting cam 78 is provided with a central opening and is mounted on a cylindrical boss 42g formed on base 42. A spring washer 86 frictionally gripping the periphery of an inner concentric boss 42; bears against cam 78 to hold it against axial displacement. A member 88 journaled for rotational movement in mounting bracket 36 has a lug 880 which interfits with cam 78 in an opening 78a formed in the latter. On the outer side of bracket 36 member 88 penetrates and is non-rotatably upset over a U-shaped member 90 to which range adjusting knob 34 is fitted. The portion 881) has a triangular shaped high point 880 which when knob 34 is turned to its counterclockwise extreme limit (when looking in from the left in FIG. 1) engages the end 62 of a hook portion 62g of drive lever 62 to pivot the latter to a clockwise extreme position wherein it manually toggles member 54 to and holds it in a position disengaging contacts 52 and 46. The last mentioned extreme limit is determined when member 90 engages a raised projection 36a struck up from the bracket 36.

In one preferred embodiment of cam 78 its peripheral form will be like that depicted in FIG. 7. As viewed in FIG. 7, if cam is rotated clockwise the radial distance be tween its point of engagement with the end 68b of range lever 68 and its axis of rotation decreases thereby causing the end 6812 to move upwardly as member 68 pivots on the ends of legs 66a of thrust plate. Consequently lever 68 pivots clockwise as viewed in FIGS. 3 and 4,

thereby lowering its end 68d which in turn causes cut-in and cut-out levers 7i and '72 to pivot counterclockwise about the ends of the differential adjusting screws 80 and 83. As will hereinafter be apparent the higher the position of the end 68b of range lever 68 as established by cam 78, the higher will be the pressures in power element 39 at which contact 52 will be engaged and subsequently disengaged from contact 46.

Let it be assumed that the contacts 52 and 46 are initially open as depicted in FIG. 3, and that cam 78 is given an intermediate adjustment depicted. Now if element 40 is subjected to an increasing temperature, the pressure in chamber 38 will increase and diaphragm 30d will move upwardly. Thrust plate 66 moves upwardly with diaphragm 3%. which in turn pivots range lever 68 counterclockwise at its point of engagement with the edge of cam 78. Such movement of lever 68 causes both the cut-in and cut-out levers 7th and 72 to be pivoted clockwise about their pivot points on the ends of diflerential adjusting screws 8%) and 82. As cut-in lever 70 continues to pivot clockwise it ultimately engages the lower side of boss 62d of drive lever 62. Further clockwise pivoting of lever 70 results in counterclockwise pivoting of lever 62 to provide the closing of contact 52 to contact 4-6 as hereinbefore described. Thus the aforedescribed levers 63, 70, 72 and 62 attain the positions depicted in FIG. 4.

Now assume, as a result of closure of contacts 52 and 46 and operation of refrigerating apparatus controlled by such contacts, that the temperature to which temperature responsive element 4% is subjected decreases. This causes a reduction in vapor or gas pressure in chamber 38 and diaphragm 30d moves downwardly. Bias spring 76 acting on cut-out lever 72 causes the latter and range lever 68 to pivot counterclockwise and clockwise respectively in following the downward movement of diaphragm 30d. Ultimately the C-shaped end 72a of cut-out lever 72 engages the boss 62d on its upper side and pivots drive lever 62 clockwise. When lever 62 is pivoted clockwise sufliciently contacts 52 and 46 are toggled opened as hereinbefore described. As will be understood the force exerted by spring 76 must be sufiicient to efiect operation of the snap action switch mechanism but should not have a spring rate greater than necessary to minimize the loading on diaphragm 30d. Spring rates in the range of 2 to 3 lbs. per inch have proved to be satisfactory for spring 76.

It will be apparent that the levers 68 and 70 or 72 provide considerable motion amplification for any upward or downward movement of diaphragm 30d. For a given setting of range adjusting cam 73, diaphragm 30d, thrust plate 66 and levers 68, 70 and 72 take new positions for each unit change in pressure developed in element 40.

The spacing between the ends 70a and 72a which underlie and overlie the boss 62d of drive lever 62 determines the diflerential betweetn cut-in and cut-out toggle operation to close and open the contacts 52 and 46. This differential is adjustable in accordance with the adjustment of the screws 8% and 82. Cut-in and cut-out differential adjustments are initially established by subjecting element 4t) to a low cut-out temperature, say 20 F. for a given intermediate adjustment of cam 78. When element 40 is stabilized at 20 adjusting screw 82 is adjusted to pivot lever 72 counterclockwise and engage boss 62d of drive lever 62 and is continued until toggle action of the contact operating mechanism occurs and opens contacts 52 and 46. If it is desired that contacts 52 and 46 reclose at a 10 higher temperature, then element 40 will next be subjected and stabilized at such a temperature, e.g., 30 F. and adjusting screw 80 is turned to pivot lever 70 clockwise on end 68d of lever 68 to engage boss 62d and pivot drive lever 62 until the point is reached where the contact operating mechanism is toggled to close contacts 52 and 46. Thereafter for any given positioning of cam 78 the cut-in and cut-out temperatures will al ways have the same fixed differential.

We claim:

1. In a snap action switch mechanism, a thin flexible member having a fixed end portion and three, parallel spaced apart portions which are integral with and depend from said end portion, the center one of said three portions having a central opening formed therein, an operating lever pivoted on an inner edge of said center portion adjacent said end portion, and a snap member formed of thin spring metal having a transverse slot adjacent one end through which said center portion extends and be ing longitudinally bowed with its other end seating against said lever, said slot being substantially wider along the longitudinal dimension of said snap member than the thickness of said flexible member, said other two portions of said flexible member anchoring the first mentioned end of said spring against longitudinal and transverse movement on said center portion, and said lever being pivotally movable in opposite directions to move said other end of said snap member across the plane of said center portion of said flexible member to provide lost motion, snap toggling of said center portion by said snap member from one stable position to another and vice versa.

2. The combination according to claim 1 wherein said lever is provided with V-shaped bearing notches where it engages with said flexible member and said snap member.

3. The combination according to claim 1 wherein said other two portions of said flexible member adjacent their ends are turned in toward each other and through said slot in said snap member toward said end portion of said flexible member.

4. In a snap action switch, a molded insulating base, an electrical terminal member having a stationary contact tip mounted on said base, a thin flexible electrical conducting member having an end portion secured to said base and having three, spaced apart parallel portions integral with and depending from said end portion, the center of said three portions having a contact tip mounted thereon in line with that of said terminal member and having a central opening formed therein, a drive lever of insulating material pivoted on an inside edge of said center portion adjacent said end portion, and a snap member formed of thin spring metal and having a transverseslot formed adjacent one end through which said center portion extends and being longitudinally bowed with its other end seating on said lever, said slot being substantially wider along the longitudinal dimension of said snap member than the thickness of said flexible member, said other two portions of said flexible member anchoring the first mentioned end of said spring against longitudinal and transverse movement on said center portion and said drive lever when driven in opposite directions pivoting said other end of said snap members across the plane of said flexible member to provide lost motion snap toggling of said center portion by said snap member from one stable position to another.

5. The combination according to claim 4 wherein said flexible member is prestressed to engage its contact tip with the other contact tip and wherein such contact tip engagement is maintained until said snap member is toggled in one direction to take up the lost motion afforded by the width of said slot and positively move said flexible member in contact disengaging direction.

6. The combination according to claim 4 wherein a second electrical terminal member is secured to said base in overlying engaging relation to said end portion of said flexible member and is provided with a portion overlying said center portion of said flexible member to provide a limit stop for said center portion when the latter moves to disengage its contact tip from the other contact tip.

'7. The combination according to claim 6 wherein said base and said second electrical conducting member having abutments which are engaged by a portion of said lever to limit the pivotal movement of the latter in each of its reverse directions.

8. The combination according to claim 4 wherein said other two portions of said flexible member are relatively narrow and adjacent their ends are turned toward each other and through the slot in said snap member toward said end portion of said flexible member to longitudinally and transversely anchor the first mentioned end of said snap member on said center portion.

9. The combination according to claim 4 wherein said drive lever is provided with V-shaped bearing notches O (I? wherein it engages with said flexible and snap members.

References Cited by the Examiner UNITED STATES PATENTS 2,197,229 4/40 \Vaddell 20067 X 2,460,087 1/49 Hollis 20067 2,813,946 11/57 Cox 20067 X 2,905,782 9/59 Chapin et a1. 200-67 2,927,171 3/60 Rhodes 20067 BERNARD A. GILHEANY, Primary Examiner.

Claims (1)

1. IN A SNAP ACTION SWITCH MECHANISM, A THIN FLEXIBLE MEMBER HAVING A FIXED END PORTION AND THREE, PARALLE SPACED APART PORTIONS WHICH ARE INTEGRAL WITH AND DEPEND FROM SAID END PORTION, THE CENTER ONE OF SAID THREE PORTIONS HAVING A CENTRAL OPENING FORMED THEREIN, AN OPERATING LEVER PIVOTED ON AN INNER EDGE OF SAID CENTER PORTION ADJACENT SAID END PORTION, AND A SNAP MEMBER FORMED OF THIN SPRING METAL HAVING A TRANSVERSE SLOT ADJACENT ONE END THROUGH WHICH SAID CENTER PORTION EXTENDS AND BEING LONGITUDINALLY BOWED WITH ITS OTHER END SEATING AGAINST SAID LEVER, SAID SLOT BEING SUBSTANTIALLY WIDER ALONG THE LONGITUDINAL DIMENSION OF SAID SNAP MEMBER THAN THE THICKNESS OF SAID FLEXIBLE MEMBER, SAID OTHER TWO PORTIONS OF SAID FLEXIBLE MEMBER ANCHORING THE FIRST MENTIONED END OF SAID SPRING AGAINST LONGITUDINAL AND TRANSVERSE MOVEMENT ON SAID CENTER PORTION, AND SAID LEVER BEING PIVOTALLY MOVABLE IN OPPOSITE DIRECTIONS TO MOVE SAID OTHER END OF SAID SNAP MEMBER ACROSS THE PLANE OF SAID CENTER PORTION OF SAID FLEXIBLE MEMBER TO PROVIDE LOST MOTION, SNAP TOGGLING OF SAID CENTER PORTION BY SAID SNAP MEMBER FROM ONE STABLE POSITION TO ANOTHER AND VICE VERSA.

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