US3265844A - Mercury switch - Google Patents

Description

Aug. 9', 1966 L. w. COOK 3,265,844

MERCURY SWITCH Filed April 25, 1963 2 Sheets-Sheet 1 INVENTOR.

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A TTORNEY Aug. 9, 1966 L. w. cooK 3,265,844

MERCURY SWITCH Filed April 25, 1963 3 Sheets-Sheet 2 FIG 7 INVENTOR. Zea/76rd if 600%, BY

MM 4 6 1M A TTORNE Y United States Patent 0 3,265,844 MERCURY SWITCH Leonard W. Cook, Warwick, RJL, assignor to General Electric Company, a corporation of New York Filed Apr. 25, 1963, Ser. No. 275,719 7 Claims. (Cl. 200-152) This invention relates to an electrical switch, .and more particularly, to a mercury button electrical switch.

Many examples of mercury switches may be found in the prior art. Those switches most closely related to the present invention employ a mercury button as the circuit control element, with the button having a metallic or ceramic envelope containing a quantity of mercury and two contact electrodes. When the switch is in an open position, the mercury is normally separated into two pools, one contacting each electrode. As the switch is moved to the closed position, the mercury forms a single pool which completes the circuit between the electrodes. Control over the separation or joining of the mercury pools is typically exercised by an operating means rotating the mercury button between the switch open and switch closed positions.

One example of such a switch is shown in Sambleson Patent 2,142,154, assigned to the assignce of the present invention. As there discussed, provision must be made to contact the electrodes of the mercury button and to support the button for rotation. In the Sambleson switch, these two objectives .are obtained by providing projections having part spherical surfaces on the resilient contact arms, which engage complementary part spherical depressions on either side of the mercury button, providing a ball and socket joint. While this switch assembly has performed satisfactorily, it has been found to have certain disadvantages. For example, it is possible to incorrectly assemble the mercury button so that the part spherical depressions are not properly aligned on the true axis for button rotation. As a result, the button may become canted in the switch assembly. This misalignment may lead to poor electrical contact of the button terminals with resultant overheating, and excessive play between the mercury button and the operating means, causing the operating means to become disengaged from the button and fail to move it properly.

As a further example, in assembling the Sambleson switch, the button must be trapped between the resilient contact arms before the arms are inserted into the switch housing. This assembly procedure requires care and may be difficult to perform. Further, slight changes in the part spherical form of either the contact arms or the mercury button can greatly change the location of contact between the two, affecting operation.

The mercury switch of the present invention overcomes these disadvantages by assuring that the axis of rotation of the mercury button is placed on a predetermined axis and retained along that axis with adequate electrical contact.

' This invention has .as one of its objects the placement of the axis of rotation of the mercury button along a predetermined axis in a switch housing and the retention of the button along that axis.

Another object is to permit ease of assembly for a mercury button switch, with retention of the button in the assembled switch.

Another object is to assure continued adequate elec- Patented August 9, 1966 "ice trical contact for the terminals of the mercury button, giving a long and reliable operating life.

In one form of the present invention these objects are attained by providing within a switch housing resilient contact members for receiving a mercury button, such as that disclosed in Cook Patent 3,032,633, assigned to the assignee of the present invention. This button is of generally cylindrical form and has terminals protruding along the axis of the cylinder. These terminals serve both as contact electrodes for the mercury held within the button and as trunnions for button rotation. Channel indentations are placed on the contact members, extending from an edge, to engage the terminals of the button and to provide electrical contact and bearing surfaces which determine the axis of rotation of the button. The indentations are formed in a scoop shape, flared adjacent the edge of the contact, so that the button may be easily placed in the housing and retained along the proper rotational axis by the cooperation of the indentations and the resilient force of the switch mounting bracket.

The present invention may be most clearly understood when described in conjunction with the accompanying drawings, in which:

.FIGURE 1 is a top view, partly broken away, of an assembled switch;

FIGURE 2 is an exploded perspective view of certain elements ofthe switch assembly;

FIGURE 3 is a side view, in partial section, of an assembled switch;

FIGURE 4 is the same as FIGURE 3, showing the operating means in an intermediate position;

FIGURE 5 is a cross-sectional view of the switch taken along the line 55 of FIGURE 4;

FIGURE 6 is a view of a portion of a contact member showing a modified form of indentation; and

FIGURE 7 is a view of a portion of a contact member showing another modified form of indentation.

As shown by FIGURES 1-5, the switch may be assembled in a housing 10 of an insulating material. The housing is of a generally rectangular shape, .and has an open side to permit insertion and assembly of the various switch elements. The open side of the housing is closed, in the assembled switch, by a mounting bracket 11. The elements of the assembled switch which are contained within the housing are an operating means, or trigger 12, a mercury button 13, and two spaced contact members 14.

The exploded view of these elements shown in FIG- URE 2 makes clear the relationship and certain features of the trigger 12 and themercury button 13. As illustrated, the button 13 is of the type disclosed in the previously mentioned Patent 3,032,633. The metallic shell 15 of the button has an indexing slot 16 and terminals 17, one of which is shown in FIGURE 2. The indexing slot 16 serves several purposes, one of which is to provide a means for the trigger 12 to engage the button. The side of the trigger to be placed adjacent the button is formed as an arcuate surface having a protrusion 18 which engages the indexing slot 16 and causes the button to move with the trigger. The assembled relation of the trigger and button, in which the protrusion engages the indexing slot, is most clearly illustrated in FIGURE 3. The trigger 12 is also provided with extensions 19 which are formed with two short planar surfaces 20, 21 tangent to a cylindrical surface about the axis of rotation of the mercury button, when the trigger and button are in the assembled relationship. These planar surfaces engage the lower surface of the mounting bracket 11 in the assembled switch. The resilience of the mounting bracket 11 is such that the trigger 12 is stable when one of the planar surfaces 20, 21 is engaged by the bracket and unstable in any other position. The unstable, transient, position is illustrated in FIGURE 4. Thus, the planar surfaces 20, 21 cooperate with the mounting bracket 11, in the assembled switch, to provide a snap action, twoposition switch movement.

The protruding terminals 17 are of cylindrical form, and together define the desired axis of rotation for the mercury button 13. The resilient force of the mounting bracket 11 acting against the trigger 12, .and the engagement of trigger 12 with the button 13 are such that the trigger rotates as a unit with the button about this axis defined by the trunnion terminals 17.

The contact members 14 are held within the housing by any suitable means such as slots 22 formed in opposite end walls of the housing and projections 23 formed on the bottom of the housing. The contact members are identical parts, each of which is provided with a conventional screw terminal 24 for attachment of the external wiring. In order to assure that the button is maintained on the correct axis for rotation in the housing, each of the contact members is provided with a channel indentation 25, extending from an edge. The contact member may be of an H shape, as shown in FIG- URE 3, and, referring to that particular drawing, the indentation extends downwardly from the upper edge of the contact member across bar 26. While it is convenient at this point to describe the features of the contact structure with reference to the particular coordinate system of FIGURE 3 in which the trigger is directed upwardly, it

must be recognized that the switch may be mounted in various other positions and the coordinate convention chosen will vary accordingly.

As may be noted from FIGURE 5, the indentations 25 of the contact members 14 are struck outwardly so that when the contact members are positioned in the housing, the convex side of the indentation faces the nearest housing wall. In order to facilitate insertion of the button 13 during assembly of the switch, the indentations 25 are also given a scoop shape opening upwardly so that, when the contacts are assembled in the switch housing, the upper end of the indentation, adjacent the edge, is flared outwardly to closely approach the housing wall. Careful placement of the contact members 14 in the housing 10 will permit alignment of the indentations 25 on the members along any desired axis. As this alignment is determinative of the location of the trunnion terminals 17, it is also determinative of the axis of rotation of both the mercury button 13 and the trigger 12 in the assembled switch. It is necessary that the contact members be correctly positioned within the housing by such means as the slots 22 and projections 23 formed with the housing.

The exact construction of the indentation is most clearly shown in FIGURE 2 which shows a channel indentation 25 extending downwardly from an edge of a contact member 14, with the indentation having a scoop shape opening upwardly. The lower end of the indentation 25 is struck along a straight line generally parallel to the edge of the contact cross-bar 26 and is sharply stamped so as to provide a ledge 27 perpendicular to the principal plane of the contact material, having a depth equal to the thickness of the stock material from which the contact member is formed. The side surfaces 28 of the indentation, although not so sharply struck as to cut the stock material, are stamped so that they are generally perpendicular to both the principal plane of the stock material and the ledge 27, and generally parallel to each other. The distance between these side surfaces must be at least as great as the maximum cross-sectional dimension of the trunnion terminals 17, to allow admission of the button, but preferably does not substantially exceed such dimension. Stamping these side surfaces of the in dentation in this manner assures additional resistance to dislodging the trunnion terminals 17 from the indentations 25 due to the possible development of any twisting forces on the button. The resilience of the contact members 14, which are bowed outwardly by inserting the button 13 into the slightly scoop-shaped indentations 25, provides a force acting along the axis of rotation.

In assembling the mercury button switch from these components, contact members 14 hearing indentations are first placed in the insulating housing 10. The mercury button 13 is then inserted and pushed downwardly with the terminals 17 entering the indentations fully. These trunnion terminals thus bear against ledge 27 of each of the contact indentations, which provide a bearing surface about which the rotating parts of the switch assembly move. The trigger 12 is then placed in engagement with the mercury button, with the protrusion 18 engaging indexing slot '16, and the mounting bracket 11 is secured to the housing to complete the assembly. When the mounting bracket 11 is secured to the housing 10, the bracket brings into play a resilient force acting downwardly upon the planar surfaces 20, 21 of the trigger. This resilient force presses the trunnion terminals 17 of the mercury button 13 against the ledges 27 of the contact members 14 assuring that the button rotates about the desired axis, maintaining the button in alignment with this desired axis, and generating a high contact pressure between the trunnion terminals 17 and the ledges 27 by which the electrical resistance of the assembly is kept low. The resilient force also prevents the trigger protrusion 18 from becoming disengaged from the button index slot '16 thus assuring that the mercury button will always move with the trigger as desired.

The resilient mounting bracket 11, then, performs a multiplicity of functions in the assembled switch. First, it provides the conventional mounting for placing the assembled switch in a use location. Secondly, it provides a resilient force which, acting against the trunnion terminals of the mercury button, retains the mercury button in the desired position within the switch assembly and assures good electrical contact. Thirdly, the mounting Ibracket provides a resilient force acting against the switch trigger to prevent the trigger from becoming disengaged from the button. Finally, as the resilient force acts against the planar surfaces 20, 21 of the trigger extensions, a snap action operation is provided for the switch.

It may be seen that the contact members with the indentations of the present invention cooperate with a mercury button having axial terminal protuberances in the switch assembly to assure adequate electrical contact for the button terminals and to assure that the button rotates about the desired axis of rotation. With the indentation formed as shown in FIGURES 2 through 5, ease of insertion of the button during the manufacturing process is attained by the scoop-shaped indentation 25 while the ledge surface 27 serves to determine the axis of rotation of the button and provides an electrical contact area. Retention of the terminals of the button against the ledges 27 is achieved by use of the resilient mounting bracket 11, acting against the trigger 12 and urging button 13 downwardly.

The modified indentation 29 of FIGURE 6 is initially formed in a contact member 30-similar tocontact member 14 of FIGURE 2. A slot 31 is then formed in the indentation, extending from the upper end of the indentation downwardly toward the ledge 32.

This modified indentation form provides the ease of assembly advantages and bearing and eelctrical contact surface characteristics of the first indentation type. Additionally, the slot 31 provided in this modified form of indentation permits a slight vertical flexure of the contact member cross bar under the single downwardly directed resilient force of the mounting bracket 11. This flexure makes it possible for the switch assembly to adjust to the small manufacturing tolerance variations which are encountered in mass produced items.

The modified contact member of FIGURE 7 embodies the form of the indentation illustrated in FIGURE 2, in that a scoop-shaped indentation 33 and a ledge 34 are used. In addition, a boss 35 is struck in the indentation counter to the direction in which the major indentation 33 is struck. Thus, if the contact member is to be placed in the switch housing 10 so that the major indentation has its convex side toward the nearest housing wall, the boss 35 is so placed as to have its convex surface directed inwardly, toward the center of the housing.

This modified contact indentation form has the manufacturing advantages, bearing and electrical contact surface characteristics of the indentation form shown in FIGURE 2. In addition, the provision of the boss 35 introduces a further safeguard against dislodging the terminals 17 of the mercury button from the desired position, thus providing additional assurance that the button will be retained along the desired axis of rotation. This is additionally advantageous during the assembly procedure for the switch or under the possible situation in which the resilient mounting bracket 11 is removed or accidentally loosened.

While the present invention has been described with some particularity, it is to be understood that this is done for illustrative purposes only and the proper scope of the invention is to be determined solely from the appended claims.

What I claim .as new and desire to secure by Letters Patent of the United States is:

1. In a mercury switch (a) ahousing,

(b) a mercury button having aligned axially protruding terminals,

(c) spaced contact members mounted within said housing for supporting said button for rotational movement about an axis defined by said terminals,

((1) each of said contact members having an indentation extending from an edge thereof,

(e) said terminals being received in said indentations,

and

(f) means for urging said terminals into engagement with said contact members.

2. In amercury switch (a) ahousing,

(b) a mercury button having aligned axially protruding terminals,

(c) spaced contact members mounted within said housing for supporting said button for rotational movement about an axis defined by said terminals,

((1) each of said contact members having a principal plane and having an indentation extending from an edge thereof,

(e) each of said indentations terminating, at the extremity from said edge, in a ledge perpendicular to the principal plane of said contact member,

(I) said terminals being received in said indentations,

and

(g) means for urging said terminals into engagement with said ledges.

3. In a mercury switch (a) a housing,

(b) a mercury button having aligned axially protruding terminals,

(c) spaced contact members mounted within said housing for supporting said button for rotational movement about an axis defined by said terminals,

(d) each of said cont-act members having a channel indentation extending from an edge thereof,

(e) said channel indentation having two parallel side surfaces spaced apart a distance at least as great as the maximum cross sectional dimension of said terminals, and terminating, at the extremity from said edge, in a ledge perpendicular to said sides,

(f) said terminals being received in said indentations,

and

(g) means for urging said terminals into engagement with said ledges.

4. In a mercury switch (a) ahousing,

(b) a mercury button having aligned axially protruding terminals,

(c) spaced contact members mounted within said housing for supporting said button for rotational movement about an axis defined by said terminals,

(d) each of said contact members having a principal plane and having a channel indentation extending from an edge thereof,

(e) each of said channel indentations having side surfaces generally perpendicular to the principal plane of said contact member,

(f) each of said channel indentations terminating, at

the extremity from said edge, in a ledge perpendicular to the principal plane of said contact member and said side surfaces,

(g) said terminals being received in said indentations,

and

(h) means for urging said terminals into engagement with said ledges.

5. In a mercury switch (a) a housing,

(b) a mercury button having aligned axially protruding terminals,

(c) spaced contact members mounted within said housing for supporting said button for rotational movement about an axis defined by said terminals,

(d) the ends of said terminals having plane surfaces perpendicular to said axis,

(e) each of said contact members having a principal plane and having an indentation extending from an edge thereof,

(f) a portion of each of said indentations, adjacent the extremity of said indentation from said edge, lying in a plane parallel to the principal plane of said contact member,

(g) said terminals being received in said indentations,

and

(h) means for urging said terminals into engagement with said contact members.

6. In a mercury switch ('a) .a housing,

(b) a mercury button having aligned axially protruding terminals,

(0) spaced contact members mounted within said housing for supporting said button for rotational movement about an axis defined by said terminals,

(d) each of said contact members having an indentation extending from an edge thereof,

(e) each of said indentations having a slot extending from said edge and terminating at a distance from the extremity of said indentation at least as great as the maximum cross sectional dimension of said terminals,

(f) said terminals being received in said indentations, and (g) means for urging said terminals into engagement with said contact members.

7. In a mercury switch (a) ahousing,

(b) a mercury button having aligned axially protruding terminals,

(c) spaced contact members mounted within said housing for supporting said button for rotational movement about an axis defined by said terminals,

(d) each of said contact members having an outwardly struck indentation extending from an edge thereof, References Cited by the Examiner (e) each of said indentations having an inwardly struck N boss spaced from the extremity of said indentation a U ITED STATES PATENTS distance at least as great as the maximum cross sec- 3,054,878 9/1962 Wlley 200 152 tional dimension of said terminals, 5 3,089,937 5/1963 Von HOOIn et al 200-152 (f) said terminals being received in said indentations, 3309979 10/1963 Sheldon et 200.452

and

(g) means for urging said terminals into engagement ROBERT SCHAEFER Primary Examiner with said contact members. H; HOHAUSER, Assistant Examiner.

Claims (1)

1. IN A MECURY SWITCH (A) A HOUSING, (B) A MERCURY BUTTON HAVING ALIGNED AXIALLY PROTRUDING TEREMINALS, (C) SPACED CONTACT MEMBERS MOUNTED WITHIN SAID HOUSING FOR SUPPORTING SAID BUTTON FOR ROTATIONAL MOVEMENT ABOUT AN AXIS DEFINED BY SAID TERMINALS, (D) EACH OF SAID CONTACT MEMBERS HAVING AN INDENTATION EXTENDING FROM AN EDGE THEREOF, (E) SAID TERMINALS BEING RECEIVED IN SAID INDENTATIONS, AND (F) MEANS FOR URGING SAID TERMINALS INTO ENGAGEMENT WITH SAID CONTACT MEMBERS.

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