Inertia switch

An inertia switch including a cone-shaped inertia mass element movable from a stable condition wherein it supports a movable switch plunger in a position for maintaining a pair of switch blades in an open condition, into a collapsed condition in response to an impact bringing about an abrupt change in movement. In the collapsed condition the inertia mass will be out of its plunger supporting position allowing the same to activate the switch by permitting the switch blades to close.

SUMMARY OF THE INVENTION 
This invention relates to an inertia switch apparatus responsive to abrupt 
changes in movement occurring in any direction through the horizontal 
plane. Many prior so-called inertia switches are restricted to actuation 
in limited direction movement or limited changes in velocity and thus are 
not universally adaptable. 
The present invention utilizes as its inertia element a cone-shaped member. 
From this configuration, the inertia mass is located at a point between 
the cone's circular base and its apex, permitting the cone to pivotally 
respond uniformly to an impact force coming from any direction in the 
horizontal plane. 
The switch controlling plunger provides an external releasable latch 
arrangement whereby the device will remain in its actuated condition until 
manually reset. 
Resetting is achieved by applied compression forces upon external portions 
of the plunger carrier and a directional pull out of its latched position.

GENERAL DESCRIPTION 
FIG. 6 is a side elevational view showing the inertia switch 10 of this 
invention as including a housing 11, an electrical connector compartment 
12, and an external plunger carrier 13. 
FIG. 1 shows the components of the inertia switch 10 as including an 
inertia mass element 14 in the form of a cone. The cone 14 is contained 
within a circular compartment 15, and in its normal position as seen in 
FIG. 1, the cone's circular base 16 rests upon the bottom wall 17 of the 
housing 11. 
Within the upper portion of the housing 11 and in communication with the 
electrical connector compartment 12 is an electric switch 18 having its 
external connectors 19 disposed in the electrical connector compartment 
12, while its switch blades 20 extend in a transverse direction to the 
apex 21 of the cone 14. 
Provided by the top wall of the housing 11 is a hollow sleeve 25, which 
extends in a spaced paralled direction with respect to the electrical 
connector compartment 12. The upper free end portion of the sleeve 25 is 
externally threaded as at 26 for the purpose of receiving an adjustment 
nut 27. 
Adapted to be journalled through the sleeve 25 as well as the adjustment 
nut 27 is the elongated shank portion 28 of a plunger 29. The plunger 29 
includes a circular collar 30, and has to one side thereof an elongated, 
somewhat smaller circular section 32. The section 32 is adjacent to a 
reduced circular end 31, and separated therefrom by an inclined wall 33. 
The opposite end 34 of the plunger 29 is knurled as at 35 (see FIG. 5), 
and as such is press fitted into a circular receptacle 36 provided by the 
external plunger carrier 13. The plunger carrier 13 includes a pair of 
elongated relatively thin latch legs 38, which extend substantially 
coaxially with respect to the plunger 29. The free ends of the legs 38 
provide inwardly directed hook elements 40, which are adapted to be moved 
into the housing 11 through openings 41 formed in the top wall thereof. 
The opposite ends of the latch legs 38 provide independent grip arms 42. 
It is desirable that the external plunger carrier 13 be made from a 
semi-rigid plastic material so that by external compression forces against 
the grip arms 42, there will be a slight separational movement of the 
latch legs 38 for a purpose hereinafter made apparent. 
Within the sleeve 25 and extending between the collar 30 on the plunger 29 
and the inner wall of the adjusting nut 27 is a coiled expansion spring 
43. This expansion spring 43 tends to yieldably urge plunger 29 and its 
carrier 13 in a direction of the housing 11 and through the open wall 41 
formed in the top wall thereof. 
The inertia switch 10 is adapted to be fixedly mounted to any object for 
which it is desired to monitor abrupt changes in movement or impact, and 
as such would be placed in the condition as shown in FIG. 1. 
In FIG. 1 the inertia mass element or cone 14 is properly seated within the 
compartment 15 with its circular base 16 in contact with the bottom wall 
17 of the housing 11. The apex 21 of the cone 14 engages the free inner 
end 44 of the plunger 29. In this position the cone 14 resists 
longitudinal movement of the plunger 29 as it is normally urged by the 
expansion spring 43. In such position of the plunger 29 the reduced end 32 
permits the switch blades 20 to have their free ends 45 (see FIG. 3) in 
facial contact. In this condition the switch 18 is energized and may be 
part of a control circuit not shown. When the switch housing 11 is subject 
to an abrupt change in velocity resulting from an impact or the like the 
inertia mass 14 will become unstabled and assume a tilted position such as 
is shown in FIG. 2. As the apex 21 of the cone 14 moves from beneath the 
plunger 29 it, together with the plunger carrier 13, is permitted to move 
through its longitudinal axis inwardly of the housing 11. The enlarged 
section 32 of the plunger 29 will be forced to pass between the switch 
blades 20 causing the same to open, de-energizing the switch 18. The hook 
portions 40 of the latching legs 38 will move through the opening 41 
formed in the top wall of the housing 11 and engage the bottom wall of the 
sleeve 25. In this position there is a visual indication that the inertia 
switch has been activated. 
To reset the inertia switch one need only grip the gripping arms 42 and 
compress the same together, which will result in an outward flexing of the 
latching legs 38, so that the hook elements 40 become disengaged from the 
sleeve 25. The plunger carrier 13 together with the plunger 29 may be 
withdrawn outwardly of the housing 11. By this movement the inertia mass 
or cone 14 is permitted to assume its normal condition as shown in FIG. 1 
and the inertia switch will be reactivated. 
Reference is made to FIG. 7 which illustrates a modified form of the 
inertia switch. The modification relates to the inertia mass element 14 
prime which is shown to be positioned within the switch housing within a 
compartment having inwardly tapered side walls 11 prime. The inertia mass 
14 prime will become unstable and move from beneath the plunger tip 44 
upon impact and momentarily be displaced to one side thereof, permitting 
the switch to be activated. By reason of its length when the plunger 29 is 
retracted outwardly of the switch housing, the inertia mass 14 prime will 
seek to right itself into its set position as shown. The modified inertia 
mass 14 prime has the same action as the cone shaped inertia mass 14 shown 
in the preferred form of embodiment. 
While I have illustrated and described the preferred form of construction 
for carrying my invention into effect, this is capable of variation and 
modification without departing from the spirit of the invention. I, 
therefore, do not wish to be limited to the precise details of 
construction as set forth, but desire to avail myself of such variations 
and modifications as come within the scope of the appended claims.