Force responsive switch.

The present invention relates to a force responsive switch and, more particularly, to a magnetically controlled switch which is rapidly caused to change state in response to the application of a force greater than a given magnitude and, thereafter, returned to its original state a predetermined time after the force terminates.

In certain instances, it is necessary to energize or de-energize an electrical circuit in response to the application of a force above a given magnitude. For example, a movable object, such as a vehicle, may contain an electrical circuit designed to control the inflation of an air bag or the like which must be energized in response to the rapid deceleration of the vehicle. Such an electrical circuit must remain energized. for a relatively brief period and, thereafter, be de-energized.

In general, it is difficult to design a force sensing system which will operate in this manner which will function reliably under all conditions and, at the same time, be of simple enough construction to be light in weight, small in size and inexpensive. These criteria are met by the present invention which employs two independently operating magnetic switch control systems of relatively simple construction. Ore of the systems reacts rapidly to the application of the force to change the state of the switch. The other system reacts relatively slowly to return the switch to its original state after the application of the force has ceased.

More particularly, the present invention employs a magnetically controlled switch, for operable electrical connection to the circuit to be energized or de-energized upon application of the force. Two independently acting magnetic control systems are situated adjacent the magnetically controlled switch. One of the magnetic control systems reacts relatively rapidly to the application of force and serves to change the state of the magnetically controlled switch almost instantaneously upon the application of a force above the given magnitude. The second magnetic control system reacts relatively slowly to the application of the force and serves to return the switch to its original -state a predetermined time interval after the force has ceased.

As will become clear from the following description, the time interval between changes in the stite of the magnetically controlled switch can be determined, within limits, by the appropriate selection of materials and the structure design of certain of the parts of the invention. Thus, the magnetic control system which reacts relatively slowly to the application of force may include a pair of members which move through a fluid. By selecting a fluid of a particular viscostity and by the appropriate structural design of the members, the amount of time for this magnetic control system to react can be adjusted to suit a particular application.

It is, therefore, a prime object of the present invention to provide a force responsive switch which changes state rapidly after the application of a force above a given magnitude.

It is another object of the present invention to provide a force responsive switch which returns to its original state relatively slowly in reaction to the application of a force above a given magnitude.

It is another object of the present invention to provide a force responsive switch which includes two independently reacting magnetic switch control systems.

In accordance with the present invention, a force responsive switch is provided comprising magnetically operated means switchable between first and second states and first and second magnetic means for controlling the state of the switchable means. The first magnetic control means reacts relatively rapidly to the application of a force above a given magnitude and is adapted to change the state of the switchable means from a first state to a second state. The second magnetic control means reacts relatively slowly to the application of force above a given magnitude and is adapted to change the state of the switchable means from the second state to the first state.

In a preferred embodiment, the switch includes a housing with a first recess. The first magnetic control means comprises a magnet fixedly mounted to the housing, proximate one end of the recess. Situated within the first recess is a magnet movable within the recess between a first position, proximate the fixed magnet and a second position remote from the fixed magnet.

Preferably, the switchable means comprises a conventional reed switch. The reed switch is mounted in the housing proximate the first recess.

The housing also has a second recess. The second magnetic control means comprises a second fixed magnet fixedly mounted proximate one end of the second recess. Situated within the second recess is a second magnet movable therein between a first position proximate the second fixed magnet and a second position remote from the second fixed magnet.

Self-adjusting means are associated with the second movable magnet and are adapted to regulate the speed of movement of the second movable magnet by permitting movement in a first direction with minimum resistance and movement in a second direction with maximum resistance.

The second recess is preferably filled with a fluid. The speed regulation means includes mechanical means situated in the fluid for increasing the resistance of the fluid to the movement of the mechanical means, as the second movable magnet moves in one direction, from its second to its first position, as compared to the resistance of the fluid to the movement of the mechanical means, as the second movable magnet moves in the other direction, from its first position to its second position.

The mechanical means includes a member movably mounted to the second movable magnet. The member is movable betveen a first position, wherein the fluid exerts relatively little resistance to the movement thereof, to a second position, wherein the fluid exerts a relatively large resistance to the movement thereof. Preferably, the mechanical means includes a connecting element mounted to the second movable magnet and first and second movable members. The first and second movable members are pivotally mounted to one end of the connecting element.

Upon the application of sufficient force to overcome the magnetic attraction between the fixed magnets and the movable magnets, respectively, the movable magnets each move to a position within the respective recesses which is remote from the fixed magnets. The first movable magnet, which is situated in a non-sealed reces.s, reaches the far end of the recess fairly rapidly, actuating a reed switch located proximate thereto within the housing. The second movable magnet, which is situated within the fluid filled recess, moves to its remote position somewhat more slowly, in part due to the effect of the pivotally connected speed regulating members, although the members are in a position of least resistance for movement in this direction.

After the force ceases, uhe first movable magnet returns relatively rapidly to its original position because of the attraction of the first fixed magnet. However, this does not effect the state of the switch because the second movable magnet functions to maintain the switch in the changed state. The second movable magnet will reverse direction and move back towards its original position because of the attraction of the second fixed magnet. Upon this reversal of direction, the speed regulating members will pivot to positions of maximum resistance, thereby reducing the return speed of the second movable magnet. Upon return to its original position, the second movable magnet will change the state of the reed switch back to its original state. In this manner, the state of the reed switch is changed from its original state relatively rapidly after the application of the force, but is returned to its original state only a predetermined time interval after the force has ceased.

A preferred force responsive switch of this invention will now be described with reference to the accompanying drawings, wherein like numerals refer to like parts, and in which: <ul id="ul0001" list-style="none"><li>Fig. 1 is a perspective view of the force. responsive switch;</li><li>Fig. 2 is a lengthwise sectional view of the switch illustrated in Fig. 1 in the rest condition; and</li><li>Figs. 3 -5 illustrate successive conditions of the switch illustrated in Fig. 1 during the operation thereof.</li></ul>

The embodiment of force responsive switch illustrated in the drawings comprises a housing, generally designated A. Housing A has a forward facing end 10 and a rear facing end 12. It is designed to be mounted in a movable object with the forward facing end 10 toward the front of the object and the rear facing end 12 toward the back thereof. Housing A includes an opening or channel 14 within which a magnetically controlled switch, such as a conventional encapsulated reed switch 16, is mounted. Reed switch 16 has leads 18 and 20 to permit same to be electrically connected to the circuit to be either energized or de-energized upon the application of sufficient force to housing A.

. Also contained within housing A, proximate reed switch 16, are first and second magnetic control systems, generally designated B and C, respectively. System B is a relatively rapidly reacting magnetic control system and will serve to change the state of reed switch 16 from its original state almost instantaneously upon the application of force above a given magnitude to housing A in a direction parallel to the longitudinal axis of housing A. System C is a relatively slowly reacting magnetic control system and will serve to change the state of reed switch 16 back to its original state a predetermined time after the applied force has ceased.

Housing A is intended to be placed in a movable object, such as a vehicle or the like, with its longitudinal axis parallel to the direction of movement of the object. When positioned in this manner, the magnetic control systems will react to the deceleration of the vehicle when that deceleration results in the application of a force above a given magnitude to housing A.

Magnetic control system B includes a fixed permanent magnet 22 with a non-magnetic isolating part 24 affixed thereto. Magnet 22 and part 24 are affixed to the rearward facing end of a non-sealed cylindrical recess or channel 26, elongated along the longitudinal axis of the housing. Recess 26 is closed at the forward facing end by a non-magnetic ston part 28. Within channel 26, between isolating part 24 and stop part 28, and freely received therein, is a movable unit including a permanent magnet 30 and a non-magnetic mass 32.

The slow reacting magnetic control system C includes a permanent magnet 34 affixed to the interior surface of the rearwardly facing wall of housing A. Magnet 34 is situated with a relatively large sealed cylindrical recess or channel 36 which contains a fluid, preferably a liquid 38. Recess 36 is generally parallel to, but spaced from, recess 26 and is elongated in a direction parallel to recess 26, that is, along the longitudinal axis of the housing. Extending inwardly from the opposite walls of recess 36, near the mid-section thereof, are a plurality of guide members 40 which function to align a second movable unit, including a permanent magnet 42 and a non-magnetic mass 44, with magnet 34 and to guide the movement of the second movable unit along recess 36.

A speed regulating means is connected to the forward facing surface of magnet 42. The speed regulating means includes a connecting element 46 and a pair of semi-circular shaped members 48a and 48b which are pivotally connected to the forward end of element 46 by any conventional means, such as a pin 50 extending between spaced ends of element 46, which passes through openings in connecting members 52a, 52b affixed to each member 48a, 48b, respectively. Members 48a and 48b change position relative to element 46, due to the resistance of fluid 38, to alter the speed of movement of magnet 42, depending upon which direction the magnet is moving.

Figs. 1 and 2 illustrate the switch in its rest condition, that is prior to the application of a significant deceleration force to the housing. Figs. 3-5 illustrate the switch at various times after the application of a signficant deceleration force.

Magnet pairs 22, 30 and 34, 42 are selected such that the magnetic attraction forces between the magnets in each pair is smaller than the force which is produced when the object in which housing A is mounted decelerates in a lengthwise direction to a given degree. For example, the attractive force of the magnets can be selected such that it will be overcome by a force of 25 g., which corresponds to a deceleration of approximately 250 meters per second per second.

When the object in which housing A is mounted decelerates sufficiency rapidly, the two magnetic control systems B and C will respond. The rapidly reacting magnetic control system B responds immediately, for a short time period, whereas the relatively slowly reacting magnetic control system C responds for a relatively long time.

As soon as the lengthwise deceleration force exceeds the magnetic attractive forces between the magnetic pairs, the movable unit including magnet 30 moves away from fixed magnet 22 and towards end part 28 along recess .26. Mass 32, which is fixed to magnet 30, moves along with magnet 30. The change in position of the magnet 30 causes reed switch 16 to change from its initial state to a second state, that is, -either from an actuated state to a deactuated state, or from a deactuated state to an actuated state. The forward movement of the unit including magnet 30 will cease once the forward surface of mass 32 abuts the rear surface of stop part 28 (as illustrated in Fig. 3).

In the meantime, the movable unit including magnet 42 and mass 44 has begun to move away from fixed magnet 34 and towards the forward facing end 10 of housing A, along recess 36. As this occurs, members 48a and 48b pivot to the position of least resistance to move through fluid 38, as illustrated in Fig. 3, such that each assumes an inclined position with respect to connecting element 46.

Members 48a and 48b will remain in this inclined position as the unit including magnet 42 travels forward along recess 36 and until the members abut the interior surface of the wall at the forward facing end 10 of the housing. At this point, members 48a and 48b pivot back to their original colinear positions, as illustrated in Fig. 4.

The movable units will remain in the positions illustrated in Fig. 4 until the applied force ceases, that is, its magnitude is reduced to a level below the attractive forces of the respective magnet pairs. At this point, the unit includi-ng magnet 30 rapidly returns to its original position proximate magnet 22. However, the unit including magnet 42 returns to its original position relatively slowly because of the resistance to movement in the return direction created by members 48a and 48b.

In their colinear positions, members 48a and 48b create the maximum resistance to the return movement of the unit including magnet 42 through fluid 38. Members 48a and 48b maintain their positions of maximum resistance as the unit including magnet 42 moves back towards fixed magnet 34, as illustrated in Fig. 5. In this position, members 48a and 48b cause the unit including magnet 42 to move towards magnet 34 relatively slowly, because of the relatively large resistance of fluid 38.

Although the unit including magnet 30 returns to its original position relatively rapidly after the application of sufficient deceleration force has terminated, reed switch 16 prevented from changing back to its original state by the influence of magnet 42. However, once magnet 42 returns to its original position, it will cause reed switch 16 to return to its initial state. Reed switch 16 has a hysteresis which prevents the switch from changing back to its original state even if magnet 32 has returned, or is returning, to its original position prior to significant movement of magnet 42. This prevents the reed switch 16 from returning to its initial state prior to the delay period, before the slow reacting magnetic control system C has sufficient opportunity to act to retain the switch in its changed state.

System B will react almost instantaneously to the application of a sufficient force and, consequently, will change the state of reed switch 16 from its initial state approximately 3 milliseconds or less after application of the force to housing A. Slow reacting system C, or; the other hand, will not function to return reed switch 16 to its initial condition until a predetermined time interval, for example 50 milliseconds, after the operative deceleration force has terminated. The reed switch 16 will thus be held in its changed state for approximately 50 milliseconds after the original actuating force has disappeared.

The selection of a fluid 38 of particular viscosity and the size and shape of members 48a and 48b will determine the delay time after which reed switch 16 will-return to its initial state. Thus, the delay time can be preset, within limits, through the appropriate selection of fluid and the structural design of members 48a and 48b.

It should now be appreciated that the present invention is a force responsive magnetic switch which is designed to be mounted on a moving object and to energize or de-energize an electrical circuit connected thereto upon the application of a sufficient deceleration force to the object. The invention includes a magnetically actuated switch, electrically connected to the circuit to be controlled and a pair of magnetic switch control systems. One of the control systems reacts relatively rapidly to the application of sufficient deceleration force and will change the state of the switch almost instantaneously. The second magnetic control system reacts much more slowly and will not return the switch to its initial state until the passage of a predetermined time interval after the force has terminated.

The speed of movement of the magnet in the second control system is regulated by a pair of pivotally mounted members, the position of which is determined by the direction of movement of the members through the fluid. The pivotally mounted members function to maximize the fluid resistance as the magnet connected thereto returns to the fixed magnet aligned therewith. As a consequence, the influence of the second magnetic control system on the reed switch, which results in the reed switch returning to its initial condition, is delayed for a predetermined time interval.

While only a single preferred embodiment of the present invention has been disclosed herein for purposes of illustration, it is obvious that many variations and modifications could be made thereto. It is intended to cover all of these variations and modifications which fall within the scope of the present invention, as defined by the following claims: