US3369098A - Switch housing including resilient compensating snap-on means - Google Patents

Description

Feb. 13, 1968 J. w. HUFFMAN 3,369,098

SWITCH HOUSING INCLUDING RESILIENT COMPENSATING SNAP-ON MEANS Original Filed May 8, 1963 INVENTOR: JUHN WHUFPMHN.

I E 4 JW @TTORNEY United States Patent 3,369,098 SWITCH HOUSING INCLUDING RESILIENT COMPENSATING SNAP-0N MEANS John W. Huffman, Mansfield, Ohio, assignor, by mesne assignments, to Emerson Electric Co., St. Louis, Mo., a corporation of Missouri Original application May 8, 1963, Ser. No. 278,959, now Patent No. 3,240,906, dated Mar. 15, 1966. Divided and this application Oct. 14, 1965, Ser. No. 496,055

6 Claims. (Cl. 200--168) ABSTRACT OF THE DISCLOSURE This invention pertains to switch mechanism and particularly to a switch housing of nonmetallic material and a metal cover therefor, the housing having recesses accommodating tab portions of convex shape on the metal cover and the end regions of the tab portions having lateral projections extending into the recesses and snapped over ridges to secure the cover to the housing.

This application is a division of my copending application, Ser. No. 278,959, now Patent No. 3,240,906.

This invention relates to switch mechanism and more especially to a dual switch mechanism in which one circuit establishing means is manually adjustable and wherein another circuit establishing means is thermostatically controlled in conjunction with the manual control.

In certain types or kinds of instrumentalities or appliances, it is desirable if not imperative to effect the electrical energization of one current consuming instrumentality or component prior to the energization of a second electrically energizable instrumentality particularly where the latter may be dependent for its successful operation upon the prior operation of the first instrumentality. A typical example of the utility of sequentially energizable dual switch means is a conventional hair dryer unit which embodies a motor driven blower or fan which is brought into operation prior to the energization of a heating element of the hair dryer unit and wherein the heating element is de-energized prior to the de-energization of the blower or fan motor.

In conventional heater switch and blower control arrangements in use at the present time in hair dryer constructions, a blower motor circuit is first energized and thereafter resistance heaters are successively or sequentially brought into operation by step switch means but without thermostatic control, reliance for different degrees of heat being provided by a plurality of individual resistance heaters brought into sequential operation through manual adjustment. In conventional hair dryer constructions, there is no provision for attaining a gradual increase or gradual decrease in heat desired as individual resistance heaters of fixed values are employed to secure different temperatures but without gradation between fixed temperatures.

The present invention embraces a method and apparatus for initiating sequential operation of dual circuit control means whereby sequential operation of dual instrumentalities is assured.

An object of the invention is the provision of switch mechanism wherein two switch means are arranged to be sequentially adjusted by manual means and wherein one of the switch means is subservient to or controlled by a thermoresponsive media whenever the said switch means is brought into operation by the manually controlled means.

Another object of the invention is the provision of dual switch mechanism having particular utility in controlling ble sequential operation in uses wherever one instrumen- 3,369,098 Patented Feb. 13, 1968 tality is energized before a second instrumentality is energized and the second instrumentality de-energized before the de-energization of the first instrumentality.

Another object of the invention resides in a switch mechanism having dual switch mean-s wherein both switch means are arranged to be manually adjusted and one of said switch means thereafter thermostatically controlled and the dual switch means connected in series whereby the switch means functions as a positive off for a circuit.

Another object of the invention is the provision of a switch mechanism embodying a thermoresponsive contact carrying arm in combination with an auxiliary heater intercalated in the circuit for influencing the thermoresponsive means and arranged to be shielded in a manner to reflect radiant heat away from the region of the thermoresponsive element whereby the thermoresponsive element is primarily influenced by conducted heat from the auxiliary heater to promote longer cycling times or periods between current on and off positions.

Another object of the invention is the provision of a thermoresponsive switch means constructed and arranged to provide for ambient temperature compensation whereby the contact carried by a thermoresponsive or bimetal element and the contact carried by a manually adjust able switch arm will be in the same relative position where both are subjected to variations in room or ambient temperature conditions.

Another object of the invention is the provision of a thermostatically controlled switch mechanism having a thermoresponsive or bimetal component constructed and arranged to foster or promote a more rapid opening and closing of the switch contacts influenced by the thermoresponsive component to substantially reduce or eliminate fluttering action of the contacts during circuit making and breaking operations whereby to reduce the arcing between the contacts and correspondingly reduce the heat generated by arcing between the contacts and thereby assure more positive cycling of desired on and off periods of current flow through the switch mechanism.

Further objects and advantages are within the scope of this invention such as relate to the arrangement, operation and function of the related elements of the structure, to various details of construction and to combinations of parts, elements per se, and to economies of manufacture .and numerous other features as will be apparent from a consideration of the specification and drawing of a form of the invention, which may be preferred, in which:

FIGURE 1 is an isometric View of a switch housing enclosing the switch mechanism of the invention and illustrating schematically two current consuming instru- Inentalities intercalated in circuit with the switch mechanism;

FIGURE 2 is a top plan view of the manually adjustable control and indicating means for the switch mechanism;

FIGURE 3 is a plan view of the switch mechanism, the cover being shown in section;

FIGURE 4 is a sectional view taken substantially on the line 44 of FIGURE 3;

FIGURE 5 is a sectional view taken the line 55 of FIGURE 3;

FIGURE 6 is an isometric view of the switch housing;

FIGURE 7 is an expanded view of components of the switch mechanism in isometric illustration; and

FIGURE 8 is a detail sectional view taken substantially on the line 88 of FIGURE 3.

The switch mechanism of the invention is particularly adapted for controlling hair drying apparatus in which a motor operated fan or air blower and an electrically energizable heater are employed, but the switch mechanism may be advantageously employed for sesubstantially on quential operation of other current consuming instrumentalities. The switch means of the invention may also be utilized to secure a positive 01f condition of a thermostatically controlled circuit to provide for positive current interruption irrespective of the relative position of the thermoresponsive component or its ambient temperature environment.

Referring to the drawings in detail and initially to the form of the invention illustrated in FIGURES 1 through 8, the switch mechanism is mounted in a suitable housing or casing fashioned of rigid insulating material, as for example, lava or other suitable high temperature resistant insulating material. In the embodiment illustrated the switch housing 10 is preferably of substantially square configuration having a bottom portion or door 12 and upwardly extending walls 14, one pair of opposing walls being formed with recesses or slots 16 shown in FIGURES 6 and 8.

A cover or closure 20 of rectangular shape is provided for the housing 10' and is preferably fashioned of metal and is provided with tabs or ear portions 22 which are adapted to be received in the recesses or slots 16, the lower end regions 24 of the tabs extending inwardly over ridges 23 to secure the cover 20 to the housing 10 in the manner particularly shown in FIGURE 8. The tabs or ears 22 are fashioned with convex portions 25 providing stressed regions to resiliently hold the end regions 24 in proper engagement with the ridges 23, as shown in FIGURE 8. The convex portions 25 serve to compensate for expansion of the cover under temperature variations set up by a heating means in the housing construction.

The base or floor 12 of the switch housing 10 is provided with notches or notched regions to accommodate three terminals 28, 30 and 32 to which circuit leads are connected for the current supply and instrumentalities controlled by the switch means. As shown in FIGURE 1, the supply line L1 is connected with the terminal 28. Terminal 30 is connected with a heating element 34 of the hair dryer unit (not shown) and terminal 32 is connected with a motor 36 operating a fan or blower for circulating air through the dryer. The other terminals of the heater 34 and the motor 36 are connected by leads 38 and 39 with the current supply line L2.

The arrangement of the invention is provided with a manually operable means for adjusting the relative position of switch means of the switch mechanism to be hereinafter described. The planar upper wall 40 of the switch cover 20 is provided with a central opening which receives the tenon portion of a bushing 42, a portion of the tenon extending within the cover 20 being swaged as shown at 44 to secure the bushing 42 to the cover. The bushing 42 is threaded internally to receive a hollow threaded shaft or stem 46 to the upper end of which is secured a manipulating knob 48 which may be molded insulating material, the knob being secured to the stem 46 by a securing screw 50.

The hollow interior of the stem..46 is threaded to accommodate an adjusting screw 52, the lower extremity of which is fashioned with a recess accommodating an end of a strut 54 of lava or other suitable rigid insulating material having high temperature resistant properties. The cover 20 is formed with a struck up or upwardly extending projection 56 which is formed by shearing a portion of the material of the upper wall 20 of the cover. Projecting laterally from the stem 46 is a stop pin 58 which is adapted to engage the projection or abutment 56 to limit rotational movement of the stem 46.

The rotational movement of the stem through its threaded engagement with the bushing 42 adjusts the position of a switch member to be hereinafter described.

The upper surface of the cover 20 is provided with a dial 60, particularly shown in FIGURE 2, and the stem 46 provided with an index or indicator 62 for cooperation with the dial 60. Where the switch mechanism of the invention is utilized for controlling a hair dryer, it is essential that the fan or blower motor 36 be energized before the heating element 34 is energized.

FIGURE 2 illustrates the knob 48 in an off position, and clockwise movement of the knob 48 and the stem 46 as viewed in FIGURE 2 first actuates one switch means to energize the motor 36 driving the fan and further clockwise movement of knob 48 energizes the heating element 34. On the indicator 60 low and high positions are indicated for heating the hair dryer but the temperature of the hair dryer is thermostatically controlled in a manner hereinafter described and the setting of the knob 48 and stem 46 determines the temperature of the hair dryer through the length of duration of the periods in which current flows through the hair dryer heating element 34.

The switch mechanism of the invention is inclusive of dual switch means, one switch means 64 being arranged to control the circuit of the blower or fan motor 36 and the second switch means 66 arranged to control the energization and de-energization of the heating element 34 through manually adjustable and thermostatically controlled means. The switch means 64 includes a switch arm or member 70' of L-shape, as shown in FIGURE 7, having a shank or body portion 72 and the projecting leg ortions 73.

The switch member 7 0 together with other components of the switch mechanism are supported on a pin or rivet 75 having a head portion 76, as shown in FIGURE 5. The terminal 28 is secured in position by a rivet 75 which, after assembly of the switch components is swaged to form a head 77. As shown in FIGURE 7, the switch arm 70 is provided with an opening 78 through which extends the rivet 75. The switch member 70 is provided with a second opening 80 through which extends the insulating strut 54. The projecting portion or leg 73 of switch member 70 is provided with a contact 82, shown in FIGURE 4.

As shown in FIGURE 4, the housing or casing 10 is fashioned with a boss portion or ledge 84 having an opening accommodating a tubular rivet or pin 85, the interior of the rivet or pin being threaded to accommodate a threaded tenon 85' secured to or forming an extension of a contact 86 of silver or other suitable material adapted for cooperation with the contact 82 carried by the relatively movable or flexible switch arm 70. The end of the threaded tenon 85 is formed with a kerf to accommodate a tool inserted through the hollow interior of the rivet 85 in order to adjust the relative position of the contact 86. The rivet 85 extends through an opening in terminal member 32 and serves to retain the terminal in fixed position, the end of the hollow rivet 85, after assembly, being swaged to form a head 87 adjacent and engaging the terminal 32. The cooperating contacts 82 and 86 control the circuit through the blower motor 36 illustrated schematically in FIGURE 1.

The second switch means 66 includes a switch arm 90 of L-shaped configuration including a body or shank portion 92 and a laterally extending leg portion or projection 93, shown in FIGURE 7, provided with a contact 95. The body or shank portion 92 of switch member 90 has an opening 94 to receive the rivet 75, as shown in FIGURE 5. In assembly, the body portion of switch member 70 is contiguous with the shank or body portion 92 of the second switch member 90, the leg portion 73 of switch member 70 extending in a right-hand direction as viewed in FIGURE 3, and the leg portion 93 of switch member 90 extending in a left-hand direction as viewed in FIGURES 3 and 4.

The switch mechanism is inclusive of a thermoresponsive component or element 98 which is fashioned of two metals having dissimilar coefiicients of expansion whereby the element is deflected under variations in ambient temperature conditions. The thermorespousive element 98 is provided with an opening 100, shown in FIGURE 7. Assembled on the pin or rivet 75, shown in FIGURE 5, is an insulating bushing or member 102 provided with a tenon portion 104. The thermoresponsive element 98 is mounted on the insulating bushing 102, the opening 100 accommodating the tenon portion 104. The bushing 102 may be made of high temperature resistant ceramic material or lava.

Secured to an end region of the bimetallic element 98 is a member or element 106 which is secured to the bimetallic element by means of a rivet 108, or other suitable securing means.

The member or element 106 at its terminal region is provided with a contact 110 adapted for cooperation with the contact 95 carried by the switch member 90. The cooperating contacts 95 and 110 control the circuit through the heating element 34, shown schematically in FIGURE 1.

The member or element 106 may be fashioned of bimetallic material or strip but inverted with relation to the bimetallic element 98 whereby ambient temperature variations will cause the member 106 to flex in a direction opposite to that of the bimetallic element 98 for a purpose hereinafter explained. The element 106 is preferably of lesser length than the bimetallic element 98 so that ambient temperature variations affect the bimetallic element 98 to move the contact 110 through the element 106 of inverted bimetallic material partially offsets or counteracts a portion of the movement of the bimetallic element The extension or element may be fashioned of nonthermoresponsive material such as stainless steel or the like which, as hereinafter explained, provides a similar action in association with the bimetallic element 98. With particular reference to FIGURE 5, the bimetallic element 98 is disposed so that upon an increase in ambient temperature conditions, the bimetallic element 98 is flexed downwardly to move the contact 110 carried thereby in a direction away from the contact 95.

A supplemental heating element 116 is embodied in the switch mechanism for establishing heat to influence the bimetallic element 98 when the contacts 95 and 110 are in circuit-closing position establishing a circuit through the heating element 34, shown in FIGURE 1. With particular reference to FIGURE 4, a rivet 114 secures the terminal member 30 to the housing 10. One end of the supplemental resistance heater or heating element 116 surrounds the rivet 114 within the housing 10 adjacent the head 118 of the rivet.

The opposite end region 120 of the supplemental heating element 116 is disposed beneath and in contact with a metal plate 122, shown in FIGURES 5 and 7, the plate The purpose of the supplemental heater 116 is to establish heat adjacent the bimetal element 98 during the periods that the current flows through the main heating element 34 shown in FIGURE 1. While it is essential to thermoresponsive control of the circuit through the contacts 95 and 110 to provide the supplemental heater 116 for increasing the temperature of the environment ambient the bimetal element 98, it is preferable that the major amount of heat generated by the heater 116 be conducted by the metal of the heater and the plate 122 to the bimetal element 98.

The heater 116 generates radiant heat and excessive radiant heat causes too rapid cycling or operation of the bimetal element 98. Hence in most uses for the switch mechanism it is desirable to reduce or retard the eflect of radiant heat on the bimetallic element 98. In order to retard or reflect the radiant heat, a thin layer of mica 130 is disposed above the heater 116 so as to cover the heater. Disposed above the layer 130 of mica is a layer of metal foil 132 coextensive with the mica layer 130 and, above the layer of foil 132, is a second layer of mica 134.

The foil 132 is therefore contained between the mica layers 130 and 134 so that the foil is insulated by the layers of mica. The metal foil serves the purpose of reflecting or retarding flow of radiant heat from the heater 1'16 toward the bimetallic element whereby the current on periods may be of greater duration than is possible where the radiant heat from the heater 116 is unimpeded.

It is to be understood that the current supplied to the primary heater 34 of a hair dryer unit or other instrumentality connected in circuit with the contacts 95 and 110 receives its current flow though the supplemental heater 116. Where the heater 34 does not consume a large amount of current so that heat generated by current flow through the supplemental heater 116 is not excessive, the reflective insulation provided by the layer of foil 132 may be dispensed with.

The operation of the switch mechanism shown in FIG- URES 1 through 7 as utilized for controlling a hair dryer unit wherein the heating element 34 is the heating element in the hair dryer unit and the motor 36 operates an air circulatingmeans or blower, is as follows: The switch members 70 and are normally prestressed upwardly in a direction separating the contacts 82 and from their cooperating contacts 86 and 110. Thus when the control member 48 is in the oif position the circuits through both switch arms 70 and 90 are open.

In the use of a conventional hair dryer, it is essential that the air circulating means provided by a blower be energized and in operation prior to the energization of the circuit through the hair dryer heating element 34. In initiating the use of the dryer the operator rotates the knob 48 in a clockwise direction as viewed in FIGURES 1 and 2 from an off position to the position indicating the degree of heat desired to be maintained in the hair dryer unit.

The initial rotary movement of knob 48 from an off position, through the strut 54, flexes the switch member 90 downwardly as viewed in FIGURES 4 and 5 and the stressed condition of the switch member or arm 70 causes the arm 70 to move downwardly following the downward flexure of the switch member or arm 90. This initial movement engages the contacts 82 and 86 to energize the motor 36 operating the air circulator or blower.

A position on the dial 60 designated fan indicates the setting of the knob 48 to initiate the operation of the blower without the energization of the circuit through the heating element 34.

Further rotational movement of the knob 48 in a clockwise direction flexes the switch arm 90 further downwardly and engages the contact 95 carried thereby with the contact carried by the bimetallic or thermoresponsive means 98 and 106 to thereby energize or complete a circuit through the hair dryer heating element 34. The relative rotational position of the control knob 48 between the designations low and high is determinative of the position of the switch arm 90 at which the heated environment provided by the heater 116 affects the bimetallic element to eflect disengagement of the contact 110 from the contact 95 through flexure of the bimetal element 98.

Through this means the temperature of the hair dryer unit may be maintained at a desired temperature by regulation of the knob 48 between the low and high positions provided on the dial 60. The amount of heat for the hair dryer unit generated by energization of the heating element 34 is determined by the duration of the on periods of the heating element controlled through the heat responsive movements of the bimetal element 98. During onperiods the same amount of current flows through the heating element 34 but the hair dryer temperature is varied by the duration of the current on positions controlled by the flexure of the bimetal element 98.

The action of a bimetallic strip may be comparatively slow in its action particularly Where the temperature change in the region of the thermostat is comparatively slow. This condition results in a so-called creeping action of the thermostat or bimetal means preventing an abrupt or defined making or breaking of the circuit through the contacts 95 and 110. Thus when the stress in the thermoresponsive element under ambient heat conditions approaches the critical position of engaging and disengaging the contact 110 with the contact 95, a min ute movement of the movable contact causes substantial arcing of current between the contacts establishing substantial heat.

The heat from the arc is substantial and affects the thermoresponsive element in a direction to separate the contacts 110 and 95. This additional heat from the are transmitted to the bimetallic element is soon dissipated and the contact 110 again approaches a position to engage the contact 95 and a repetition of the arcing or fluttering ensues.

The foregoing described action of a thermoresponsive element tends to occur where the entire support for the movable contact is a continuous strip of bimetal. The provision of the short length of material 106 attached to the bimetal element 98 functions to reduce the fluttering action of the contacts during a making or breaking of the circuit through engagement or disengagement of the contacts 95 and 110.

The extension element 106 secured to the bimetal element 98 may be fashioned of a bimetal strip but inverted so that the heat generated by arcing between contacts 95 and 110 is effective to flex the short bimetallic strip 106 in a direction to either positively make or break the circuit depending upon the direction of movement of the bimetal element 98.

It is found that the extension or element 106 may be fashioned of stainless steel in lieu of a bimetallic element and obtain substantially the same action. Stainless steel is a relatively poor conductor of heat and it is believed that the element 106 fashioned of stainless steel, retards the transfer of heat caused by arcing at the contacts from reaching and adversely affecting the bimetal element 98 and thereby secure a more positive and faster engagement or disengagement of the contacts 95 and 110 with a minimum of arcing.

This arrangement greatly improves the sensitivity of the control of the hair dryer heating element 34 as the bimetal element 98 with the extension 106 provides a more positive making or breaking of the contacts and hence a more reliable control of the energization and deenergization of the heating element 34.

Another feature of the switch of the invention is that when the operator desires to de-energize the hair dryer unit, rotation of the control knob 48 in a counterclockwise direction first disengages the contact 95 from the contact 110 to deenergize the heater 34 and upon further movement of the knob to off position, effects a subsequent disengagement of the contact 82 from the contact 86 to de-energize the blower motor 36.

Through this arrangement a safety factor is provided in that the air circulating means operated by the motor 36 is brought into operation before the primary heating element 34 is energized and continues to function until after the switch rnemher 9t! disengages the contact 95 from contact 110 so that whenever the heating element 34 is energized, the air circulating means operated by the motor 36 is in operation.

It is apparent that, within the scope of the invention, modifications and different arrangements may be made other than as herein disclosed, and the present disclosure is illustrative merely, the invention comprehending all variations thereof.

I claim:

1. In combination, a housing of rigid heat-resistant insulating material, switch mechanism contained in said housing, connecting terminals carried by said housing, a metal cover for said housing, exterior surface regions of said housing being formed with recesses, a ridge in each recess integral with the housing, said cover having tab portions disposed in said recesses, the end regions of said tab portions having preformed lateral projections extending into the recesses and snapped over said ridges to secure the cover to the housing, said tab portions being of convex configuration to resiliently hold the lateral projections at the end regions of the tab portions in engagement with the ridges.

2. The combination according to claim 1 wherein the housing is of lava.

3. The combination according to claim 1 wherein the housing is of rectangular configuration with one pair of opposing walls thereof provided with the recesses to receive the tab portions of the metal cover.

4. The combination according to claim 1 wherein the housing and the metal cover are of substantially square configuration.

5. In combination, a switch housing of rigid heat-resistant insulating material, said housing being of rectangular shape having a bottom portion and opposing pairs of side walls defining a hollow interior, one pair of opposing side walls having recesses therein, each of said recesses having a ridge adjacent the bottom portion, a metal cover of rectangular shape for the housing, said cover having ear portions received in the recesess, the

. end regions of the ear portions having preformed lateral projections extending inwardly and snapped over the ridges, each of said ear portions having a convex region to resiliently hold the lateral projections in engagement with the ridges and thereby compensate for expansion of the cover under temperature variations.

6. The combination according to claim 5 wherein the housing and metal cover are of square configuration.

References Cited UNITED STATES PATENTS 2,254,729 9/1941 Bryant et a1. 20(l168 2,921,147 l/1960 Hutt 200l68 3,119,916 l/l964 Holden 200168 2,665,353 1/1954 Popp 200-168 2,723,327 11/1955 Gilbert 200168 ROBERT K. SCHAEFER, Primary Examiner.

H. O. JONES, Assistant Examiner.

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