Electrical switch assembly

A small electrical switch assembly for low voltage applications which has an insulating housing and cover, an insulating spring-biased plunger of relatively long travel, two terminals and a grounding terminal, and internal self-wiping contacts; and which is adapted for quick installation and fastening to a grounded structure via an electrically conductive fastening means that automatically grounds the switch assembly if grounding is required; and which is adapted for fully automatic assembly.

BACKGROUND AND SUMMARY OF THE INVENTION 
This invention relates to the field of electrical switches, and more 
particularly to small electrical plunger switch assemblies used in low 
voltage applications where the switch is easily and quickly installed into 
some larger structure. A need has arisen for an improved easily 
manufactured electrical switch assembly having a relatively long plunger 
travel usable without modification in several applications on the same 
automobile. Such an electrical switch assembly should be adapted for quick 
fastening to a grounded structure in the automobile via a fastening means 
that electrically grounds the switch assembly to the grounded structure if 
grounding is required. The switch assembly should be corrosion resistant 
and relatively immune to the deleterious effects of occasional dripping 
water. A gasket should not be required between the switch and the 
structure into which it is installed. The contacts within the switch 
should have a wiping action for self-cleaning. The mating wiring harness 
connected to the switch should not move during operation of the switch. 
The switch should be compact and light weight. 
Accordingly, one object of the instant invention is an improved electrical 
switch assembly. 
Another object is a small electrical switch assembly having a plunger with 
relatively long travel in relation to the physical size of the switch. 
Still another object is an electrical switch assembly usable in relatively 
low voltage circuits. 
Yet another object is an electrical switch assembly that is relatively 
corrosion resistant, that requires no gasket for installation, and that 
has self-wiping contacts for self-cleaning. 
Another object is an electrical switch assembly adapted for receiving and 
being automatically electrically grounded by an electrically conductive 
fastening means as the switch is installed into a grounded structure. 
Other objects, features and advantages of the present invention will become 
apparent from the subsequent description and the appended claims taken in 
conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The preferred embodiment of present invention shown in the drawings and 
described below forms a normally closed spring-biased plunger switch, 
which is diagrammatically shown in FIG. 5. The preferred embodiment has 
three electrical termination points: terminals 1 and 2, so labelled in 
FIG. 5, which are the primary current-conducting terminals, and a 
grounding terminal, symbolically labelled as such in FIG. 5, which grounds 
out terminals 1 and 2 when the plunger is released, that is, not actuated. 
The preferred embodiment is comprised of eight components: an insulating 
housing 20, an insulating cover 22, an insulating plunger 24, a helical 
compression spring 26, an electrically conductive sleeve 28, and three 
electrically conductive members 30, 32 and 34. Two of the three conductive 
members 30 and 32, called primary conductive members or primary members, 
are identical in shape and construction. They correspond to terminals 1 
and 2 on FIG. 5. The third conductive member 34, called the grounding 
conductive member or grounding member, differs in shape and construction 
from the other two, and corresponds to the grounding terminal in FIG. 5. 
These eight components are positioned with respect to one another as 
follows. As shown in FIGS. 1, 2 and 3, the cover 22 is disposed on one end 
36 of the housing 20 and overlies access to a chamber 38 within the 
housing 20, as shown in FIG. 6. 
The plunger 24, which can best be seen in FIG. 6, is movably disposed 
within the chamber 38 between two extreme longitudinal positions and 
extends outwardly through a passage 40 in the cover 22. The plunger is 
longitudinally captivated by the housing 20 on one end, which limits the 
plunger's inward travel, and the cover 22 on the other end which limits 
the plunger's outward travel. A shoulder 42 on the plunger 24 cooperates 
with the cover 22 to limit outward movement of the plunger. 
The spring 26 as shown in FIG. 6, is disposed in the chamber 38 of the 
housing. It extends between the housing and plunger, and biases the 
plunger 24 outwardly. 
As shown in FIGS. 6 and 7, the conductive sleeve 28 is disposed in the 
chamber 38 of the housing, and is positioned on and travels with the 
plunger 24. 
The three conductive members 30, 32 and 34 are substantially disposed in 
the housing 20. The housing 20 has three elongated slots 44, 46 and 48 
opening from the same end of the housing as the chamber 38, as shown in 
FIG. 8. These slots longitudinally extend into the housing and also open 
into the chamber. The conductive members 30, 32 and 34 are partially 
disposed in slots 44, 46 and 48 respectively, one per slot. As shown in 
FIGS. 2, 3 and 6, the two primary conductive members 30 and 32 extend 
through the housing 20 opposite the cover 22. As shown in FIG. 6, the 
grounding conductive member 34 is partially disposed in slot 48 on a side 
of the housing substantially opposite slots 44 and 46. 
Although the conductive members 30, 32 and 34 are not all shaped alike, 
they share common characteristics, as shown in FIG. 6. Each conductive 
member has a first portion, 50, 52, and 54 respectively, defining a 
springable tine extending into the chamber 38. Each has a second portion, 
58, 60 and 62 respectively, inserted into a slot in the housing 20 which 
is fixedly retained therein by the cover 22 which abuts one end of the 
slots. Each has a third portion 64, 66 and 68 respectively, that extends 
outwardly from the housing 20 to facilitate electrical connection. The 
third portions 64 and 66 of the primary conductive members 30 and 32 
extend outwardly from the end of the housing opposite the cover as shown 
in FIGS. 2, 3 and 6, and constitute terminals 1 and 2 in FIG. 5. The third 
portion 68 of the grounding conductive member 34 extends outwardly from 
the housing by virtue of a tab 70 adjacent to and protruding from a hole 
76 in the cover 22, as shown in FIG. 6, and constitutes the grounding 
terminal in FIG. 5. 
When the plunger 24 is in its extreme outward position, the sleeve 28 is in 
electrical contact with the first portion of each conductive member, 
which, of course, electrically connects all the conductive members 
together. FIG. 6 shows this electrical contact occurring. 
When the plunger 24 is in its extreme inward position, the sleeve 28 is 
electrically isolated from the conductive members, thereby interrupting 
electrical continuity between the conductive members of the preferred 
embodiment. As shown in FIG. 7, electrical contact between the sleeve 28 
and conductive members 30, 32 and 34 in the preferred embodiment is 
interrupted after the plunger and sleeve have travelled through a 
relatively small part of the plunger's total possible inward travel. 
Armed with the above general description, the more detailed features of the 
preferred embodiment described below may now be appreciated. 
As shown in FIGS. 3 and 6, the housing 20 has a bracket 72 extending 
laterally from the end 36 of the housing that provides access to the 
chamber 38. This bracket 72 is positioned adjacent to slot 48 in the 
housing. The bracket 72 is provided with a rectangular hole 74. 
The cover 22 overlying the housing 20, as shown in FIGS. 3, 4 and 5, has a 
hole 76 which communicates with the hole in the bracket. 
The cover and the housing are interlocked together by features of each 
which assure proper alignment during and after assembly of the cover to 
the housing. First, the housing 20 is provided with wedge-shaped nibs 78 
and 80 protruding externally from opposite side walls 82 and 84 
respectively of the housing, as shown in FIGS. 1 and 2. When the cover is 
disposed on the housing these nibs are lockingly engaged by clips 86 and 
88 extending from the cover 22 adjacent to and parallel to the side walls 
82 and 84 of the housing. Second, as shown in FIGS. 3 and 8, the four 
corners of the end of the housing project laterally from the side walls to 
form guides 90, 92, 94 and 96 which channel the clips 86 and 88 between 
the guides, thereby insuring proper alignment of the cover 22 during and 
after its installation on the housing 20. Third, as is evident when FIGS. 
1, 2, 3, and 6 are collectively studied, the cover 22 has a shallow hollow 
98 that is complementary to the bracket 72 of the housing 20 shown in FIG. 
6. Thus, when the cover is installed on the housing, the cover surrounds 
the sides of the bracket 72, limiting lateral movement of the cover with 
respect to the housing. Fourth, as shown in FIGS. 4 and 6, the bracket 72 
of the housing 20 has a post 100 which projects through a complementary 
orifice 102 in the grounding conductive member 34 and into a complementary 
orifice 104 in the cover 22. This feature limits lateral movement of the 
cover and the grounding member with respect to the housing. 
As shown in FIG. 6, the housing and plunger have features that give lateral 
stability to the spring, especially as it is longitudinally flexed. First, 
a portion of the plunger 24 in contact with a first end portion 108 of the 
spring 26 defines a finger 106 that fits within and guides the first end 
portion 108 of the spring as the spring is flexed. Second, the chamber 38 
of the housing 20 has an innermost region 110 which partially envelopes 
and guides a second end portion 112 of the spring 26 during flexion of the 
spring. 
During substantial inward travel of the plunger 24, the finger 106 of the 
plunger and the compressing spring 26 enter the innermost region 110 of 
the chamber 38, thus permitting greater inward travel. An internal surface 
near the innermost region 110 of the housing provides a positive stop 114 
that harmlessly limits extreme inward travel of the plunger. Since the 
chamber 38 in the housing and passage 40 in the cover together are long 
enough to accept the entire length of the plunger 24, this positive stop 
114 is not encountered until the plunger has been pushed inward past the 
outer lip 116 of the passage 40 in the cover. Thus, under normal operating 
conditions of the preferred embodiment, the positive stop does not limit 
plunger travel since the plunger would not be pushed inward that far. 
As shown in FIG. 6, the spring 26 helps retain the sleeve 28 on the plunger 
24 since the first end portion 108 of the spring is always pressed against 
the cup-shaped sleeve. The sleeve 28 provides a seat 118 for the spring, 
thereby protecting against the wear of the plunger by the spring which 
could occur absent such a spring seat. 
The segment 120 of the plunger defining the shoulder performs another 
function besides limiting outward travel of the plunger 24. As shown in 
FIG. 7, this segment 120 of the plunger 24 provides a cylindrical surface 
122 which rapidly cams the tines 50, 52 and 54 of the conductive members 
30, 32, and 34 away from the sleeve 28 as the plunger 24 moves inward, 
thereby furnishing a relatively quick break of electrical contact between 
the tines and sleeve. The tines intentionally extend relatively close to 
the surface 122 so that the electrical continuity between the sleeve and 
tines will be broken near the beginning of the plunger's long inward 
travel from its outermost position. 
In the preferred embodiment, the housing, cover, and plunger are each made 
of one piece injection molded hard tough plastic, such as nylon, while the 
sleeve and the three conductive members are each made of a tin-plated 
brass stamping which is punched, folded, and bent as required. 
The primary conductive members are each formed from a one-piece flat stock 
stamping 126 having two longitudinal forks 128 and 130 and a supporting 
base 132. As shown in FIGS. 9, 10 and 11, one fork 128 is longitudinally 
creased along its entire length, giving the fork a ridge 134 which 
protrudes from the plane of the supporting base 132. This fork 128 
corresponds to the second portions 58 and 60 of the primary conductive 
members 30 and 32, as shown in FIG. 6. Returning to FIGS. 9, 10, and 11, 
the other fork 130 has a transverse bend 136 where the fork 130 meets the 
supporting base 132, and also has a transverse bend 138 near the opposite 
end of the fork. This fork 130 corresponds to the first portions 50 and 52 
of the primary conductive members 30 and 32, which define springable 
tines. The location of the two bends can also be seen in FIG. 6. The 
folded supporting base corresponds to the third portions 64 and 66 of the 
primary conductive members 30 and 32 which extend outwardly from the 
housing opposite the cover as shown in FIGS. 1, 2, and 6. The third 
portions 64 and 66 are the terminal ends of the primary conductive members 
30 and 32 diagrammatically illustrated in FIG. 5 as terminal 1 and 
terminal 2. 
The ridges in the second portions 58 and 60 of the conductive members 30 
and 32 add to the overall rigidity of the primary conductive members. 
Additionally the ridges contact lateral surfaces 140 and 142 near the 
inward end of elongated slots 44 and 46 which the second portions of the 
conductive members are disposed in, thereby limiting inward insertion of 
the primary members into their slots. 
The grounding conductive member 34, shown in FIG. 6, is also formed from a 
one-piece flat stock stamping which initially has an elongated rectangular 
shape. The stamping has a front area 146, which is punched with the 
aforementioned orifice 102 and a rectangular hole 148. The hole 148 
communicates with the holes 74 and 76 in the bracket 72 and the cover 22. 
A peninsular piece of material from the hole 148 forms the aforementioned 
tab 70, which is bent outwardly from the hole 148. The front area 146 of 
the grounding member defines a bracket which is complementary to and 
disposed over the bracket of the housing as shown in FIG. 6. A transverse 
bend 150 separates the front area 146 of the grounding member 34 from a 
rear area 152 of the grounding member 34. The rear area 152 is punched to 
form an elongated peninsula 154 longitudinally and centrally located in 
the rear area. This peninsula of material has a transverse bend 156 where 
the peninsula remains connected to the rear area 152, and has a transverse 
bend 158 near the opposite end of the peninsula. This peninsula 154 forms 
the first portion 54 of the grounding conductive member 34 and defines a 
springable tine. The remaining part of the rear area of the grounding 
member forms the second portion 62 of the grounding member 34, which is 
captivated in the slot 48. Insertion of the grounding member 34 into the 
slot 48 is limited by contact with either the blind end 160 of the slot 48 
or the bracket 72 of the housing 20 or both. As shown in FIG. 6, the tab 
70 of the grounding member 34 is bent outwardly through the hole 76 in the 
cover and then laterally towards the plunger 24, thereby projecting over a 
part of the cover. The tab 70 forms a protuberance adapted for making 
positive and automatic electrical contact with an electrically conductive 
fastening means, for attaching the electrical switch assembly to a 
grounded structure, to be received by the adjacent communicating holes. 
FIGS. 6 and 8 show the housing 20 set in a rectangular hole 168 in sheet 
metal 166. The sheet metal 166 is also provided with a hole 170 designed 
to receive an electrical fastening means for fastening the switch to the 
sheet metal. The preferred embodiment is designed to be installed in a 
grounded structure, like the sheet metal in FIG. 8, having a first that is 
complementary to the generally rectangular external cross-section of the 
housing defined by the guides of the housing, and having a second hole 
complementary to the hole in the bracket and designed to receive an 
electrically conductive fastening means. 
One possible electrically conductive fastening means is the hex-head sheet 
metal screw 172, shown in FIG. 6, which is in positive electrical contact 
with the tab 70 and the sheet metal 166 opposite the tab. Another example 
of an electrically conductive fastening means is a pop-rivet. A third is a 
threaded bolt. The sheet metal is one possible example of a grounded 
electrical structure to which the preferred embodiment could be attached. 
Those skilled in the art are familiar with other possible electrically 
conductive fastening means and other possible grounded structures, so 
additional examples of the same need not be enumerated here. 
Once the preferred embodiment is installed in and fastened to a grounded 
structure, the housing, cover and third portions of the conductive members 
will be stationary with respect to said grounded structure. Hence, any 
wiring harness connected thereto would not move when the switch is 
operated via the plunger. 
The components of the preferred embodiment cooperate to help prevent the 
plunger from binding as it is actuated by forces having a substantial 
lateral component in addition to a longitudinal force component. First, 
there is little friction between the cover 22 and the plunger 24 as the 
plunger travels in the passage 40 of the cover, since both the bore 
defined by the passage and the sides of the plunger in contact therewith 
are smooth hard plastic. Second, as shown in FIG. 6, the generally close 
tolerance between passage 40 and plunger 24 combined with length of the 
passage help keep the plunger from cocking and binding in the passage. 
Third, the spring 26 imparts lateral stability to the plunger 24, helping 
to guide the plunger and keeping it from cocking, since the spring itself 
is laterally stabilized by the innermost region 110 of the housing 20. 
Numerous features of the components of the preferred embodiment and the 
manner in which the components cooperate, render the preferred embodiment 
particularly well adapted for fully automatic assembly. Many of these 
features are readily apparent to those skilled in the art. Some of the 
more important of these features which render the preferred embodiment 
particularly well adapted for fully automatic assembly are described 
below. 
The previously described features of the cover and the housing which 
interlock the cover and housing together and assure proper alignment of 
the same during and after assembly, help adapt the preferred embodiment 
for fully automatic assembly. 
The regions 174 and 176 of the elongated slots passing through the housing 
20 opposite the cover 22 are snugly complementary to the third portions 64 
and 66 of the primary conductive members 30 and 32 disposed therein. This 
snug fit insures that the primary conductive members remain stationary 
after being fully inserted into the elongated slots during automatic 
assembly. 
The ends 178 and 180 of the primary members 30 and 32 opposite the cover 22 
are slightly rounded or tapered which aids in insertion of the same into 
regions 174 and 176 of the slots 30 and 32 during automatic assembly. 
The end 182 of the finger 106 on the plunger 24 is slightly rounded which 
aids in placing the spring 26 over the finger 106 during automatic 
assembly. 
The region 184 of the chamber 38 adjacent to the innermost region 110 is 
shaped to funnel the second end portion 112 of the spring 26 into the 
innermost region 110 of the chamber 38 during automatic assembly. 
The springable tines of the conductive members 30, 32 and 34 are bent from 
the longitudinal axis of their respective conductive members at a 
relatively shallow angle. Thus, when the plunger 24 is inserted into 
chamber 38 of the housing 20 after the conductive members 30, 32 and 34 
are already in place, the conductive sleeve 28 on the plunger is able to 
cam the tines aside, thereby facilitating automatic assembly. 
The preferred embodiment has relatively few components, and these 
components are of relatively simple shape and construction, thus helping 
to adapt the same for automatic assembly. 
In light of the foregoing features, it is deemed clear to one skilled in 
the art that the electrical switch assembly described herein is adapted 
for fully automatic assembly. 
The materials used in the components of the preferred embodiment have 
already been enumerated. Those skilled in the art no doubt recognize, 
though, that the components of the instant invention can be of any 
conventional or suitable materials made by using any conventional or 
suitable manufacturing techniques. Such materials and manufacturing 
techniques are well known in the field of small electrical switch design 
and manufacture and thus need not be recited here. 
While it is apparent that the preferred embodiment of the invention 
disclosed is well calculated to fulfill the objects above stated, it will 
be appreciated the invention is susceptible to modification, variation and 
change without departing from the proper scope or fair meaning of the 
subjoined claims.