US 3742163 A
An electric switch which is responsive to acceleration and/or deceleration having at least one movable contact arranged in a housing and biased into electrically conductive connection with a corresponding contact surface arranged in the housing. A spring serves for biasing the movable contact piece with a constantly effective force of a predetermined magnitude which is determined by the axial extent of the spring and a screw element serves for controlling the axial extent of the spring to vary the magnitude of force provided thereby. In response to an accelerative force in a predetermined direction, the contact piece overcomes the biasing force and moves away from its contact surface thereby interrupting the conductive circuit path through the switch.
Claims available in
Description (OCR text may contain errors)
United States Patent [191 Gawlick et a1.
1 June 26, 1973 1 ACCELERATION RESPONSIVE SWITCH WITH LINEARLY MOVABLE CONTACTORS  Assignee: Dynamit Wobel Aktiengesellscaft,
Troisdorf, Germany 221 Filed: Nov. 3, 1971 21 Appl. No.: 195,436
 Foreign Application Priority Data 3,161,736 12/1964 Randall et a1 ZOO/61.45 R 3,453,405 7/1969 Gasik ZOO/61.45 R 2,984,719 5/1961 Higgs et al. ZOO/61.45 R X 3,154,776 10/1964 Otten ZOO/61.45 X 3,157,757 11/1964 Lorenz ZOO/61.45 R
Primary Examiner-J. R. Scott Attorney-Craig, Antonelli & Hill  ABSTRACT An electric switch which is responsive to acceleration and/or deceleration having at least one movable contact arranged in a housing and biased into electrically conductive connection with a corresponding contact surface arranged in the housing. A spring serves for biasing the movable contact piece with a constantly effective force of a predetermined magnitude which is determined by the axial extent of the spring and a screw element serves for controlling the axial extent of the spring to vary the magnitude of force provided thereby. In response to an accelerative force in a predetermined direction, the contact piece overcomes the biasing force and moves away from its contact surface thereby interrupting the conductive circuit path through the switch.
20 Claims, 10 Drawing Figures PATENTEU JUN 2 6 I975 SHEEI 2 OF 2 ACCELERATION RESPONSIVE SWITCH WITH LINEARLY MOVABLE CONTACTORS The present invention relates to an electric switch having at least one contact piece arranged for movement within a housing and having a corresponding contact surface fixedly secured in the housing.
Switches are known which close an electric contact in response to a specific accelerative or decelerative force. Thus, in a conventional switch which responds to positive or negative acceleration, i.e., to acceleration or deceleration, a contact piece is held in the center of a housing in a freely suspended position by means of two springs. In response to an accelerative or decelerative force, which is above an adjustable value, the contact piece moves against the bias of the springs, toward one of the two contact surfaces, whereby a switching pulse is emitted upon contact.
In another type of switch, a contact piece is freely suspended on a spring within a conductive housing and in response to an accelerative or decelerative force above a predetermined value, the contact piece moves toward the housing which is electrically insulated at most parts with respect to the contact piece such that upon contact with the housing, an electrically conductive path is closed.
Conventional mechanical switches functioning in accordance with the contact closing principle have a disadvantage in that a predetermined distance must be maintained between the two contacts, for reasons inherent in the manufacturing technique and safety requirements. Thus, when the spacing between the contacts is too small and high-frequency oscillations occur at relatively low accelerative and/or decelerative values, an undesired and unintended connection may occur. In addition, extremely small tolerances must be maintained during manufacture.
If a large contact is formed for reasons of safety and manufacturing technique, the vibrating contact must traverse a correspondingly large path against the bias of the spring in response to an accelerative and/or decelerative force above the predetermined value. Thus, due to the large path of travel, the vibrating contact will touch the contact surface with a time delay which is dependent on the increase in acceleration and/or deceleration. Due to this chronological shift in the switching process at varying increases in acceleration and/or deceleration, it is difficult to adjust these contact switches since, in practical use, it is not possible to predict that an accelerative or decelerative value will continue for a predetermined time period. In the extreme case, i.e., for a very brief increase in acceleration and/or'deceleration above the adjusted switching value, it is possible that the movablecontact may not cause the switch to function in that the contact piece may not have traversed the entire path at the end of the period of increase in acceleration and/or deceleration.
A further characteristic disadvantage of these conventional switches resides in that the freely vibrating contact in response to an accelerative and/or decelerative force above the set value does not at once establish a firm contact when it first touches the contact surface, but rather, due to the elastic behavior of the contact materials, rebounds several times from the fixed contact surface. Due to these rebound effects, the instant of switching is once more shifted by an indefinable period of time until the movable contact firmly touches the surface. In this connection, there is the additional disadvantage that in case of low-frequency accelerative and/or decelerative values ranging below the set value, the inherent resonance of these systems can be reached and thereby causing the switch to function at an improper time.
Additional disadvantages exhibited by the conventional switch reside in that the springs, due to the contact masses being attached thereto, are under a constant stress, even in case of small accelerative and/or decelerative values. In addition to the constant stresses on the springs, other spring stresses result from other impact forces such that the spring characteristic may change or the spring may break due to material fatigue thereby causing switching malfunctions.
The present invention overcomes the aforementioned disadvantages by providing an electric switch with at least one contact piece movably arranged in a housing and with a corresponding contact surface fixedly disposed within the housing with the contact piece being maintained in electrically conductive contact with the contact surface by means of a continuously effective force until a predetermined accelerative or decelerative value is reached. The contact piece is disposed in the housing in such a manner that when the predetermined value has been exceeded in a predetermined direction, the electrically conductive connection between the contact piece and the contact surface is broken and thus the current flow is interrupted.
A switch in accordance with the present invention responsive to an accelerative and/or decelerative force effective in a predetermined direction may be utilized, for example, very advantageously in conjunction with sensors for inflatable safety air bags for vehicles, especially automotive vehicles, wherein the lifting of the contact or one of the contacts from the corresponding contact surface causes the switch to open. However, if accelerative and/or decelerative forces are effective upon the switch in a direction deviating from the predetermined direction, then the electric contact between the contact piece and the contact surface remains closed, unless a component of the effective accelerative and/or decelerative forces oriented into the predetermined direction exceeds the value fixed for the predetermined direction. Thus, the switch may be utilized in arrangements wherein electrically actuated devices must be mechanically switched without rebound within extremely short periods of time. If a closing function is required from the electrically actuatable device, the opening function of the switch can be transformed without rebound by means of conventional electronic circuit arrangements.
In one embodiment of the present invention, the contact piece or the contact pieces are arranged in an axially displaceable manner on a pin mounted within the housing. In this manner, movement of the contact piece or the contact pieces in an exactly defined manner is assuredand an undesired contacting, for example on the periphery, with the surrounding housing is avoided. It would, of course, also be possible to avoid an undesired contacting such as on the periphery without the provision of a pin arranged within the housing, however, this would require that either the surrounding housing is formed of an insulating material, or the inside of the housing and/or the outside of the contact piece or pieces are provided with an insulating material at predetermined locations.
In accordance with a feature of the invention, a spring, preferably a helical spring is utilized to produce the continuously effective force holding the contact piece or contact pieces in conductive connection with the respective corresponding contact surface.
In another embodiment of the present invention, means such as a screw type element is provided for rendering the magnitude of this force variable, for example, by making the distance between the contact surfaces adjustable. Thus, it is possible in a simple manner to adapt the switch to differing conditions or to adjust the switch for varying accelerative and/or decelerative force values.
This invention also provides another arrangement for changing the switching characteristic by filling the housing with a gas or a liquid, e.g. silicone oil, glycerin, or the like. Depending on the viscosity of the medium introduced into the housing, a predetermined attenuation of the motions of the movable parts disposed inthe housing will be attained and the attenuating medium can simultaneously be utilized for the corrosion protection of the contacts.
In accordance with a further embodiment of the invention, a switch is provided with two or more contact pieces having different masses in order to obtain a different acceleration or deceleration response for the individual contact pieces.
It is therefore an object of the present invention to provide an acceleration and/or deceleration responsive switch which overcomes the disadvantages of the prior art.
It is another object of the present invention to pro vide an acceleration and/or deceleration responsive switch which opens the circuit through the switch when a predetermined value is exceeded.
It is a furtherobject of thepresent invention to provide an acceleration and/or deceleration responsive switch wherein the response values may be varied.
It is still another object of the present invention to provide an acceleration and/or deceleration responsive switch wherein the response characteristics of the switch elements may be varied.
These and other objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show several embodiments of the present invention and wherein:
FIG. 1 is a sectional view of the switch of this invention with two contact pieces of identical mass which are axial movable and arranged on a pin attached-within the housing,
FIG. 2 is a sectional view showing the interrupting position of the switch of FIG. 1,
FIG. 3 is a sectional view of a switch with two contact pieces of differing masses,
FIG. 4 is a sectional view showing the interrupting position of the switch of FIG. 3,
FIG. 5 is a sectional view of a nonadjustable switch with two contact pieces of identical mass,
FIG. 6 is a sectional view of a nonadjustable switch with two contact pieces of different masses,
FIG. 7 is a sectional view of an adjustable switch with only one mass,
FIG. 8 is a sectional view showing the interrupting position of the switch of FIG. 7 in operation,
FIG. 9 is a sectional view of an adjustable switch with two contact pieces of identical mass, and
FIG. 10 is a sectional view showing the interrupting position of the switch of FIG. 9 in operation.
Referring now to the drawings wherein like reference numerals are used throughout the various figures to designate vlike parts, and more particularly to FIG. 1, there is shown an electrically conductive housing 1 having an insulating bush securing one end of a guide pin 8. The housing may be made of metal and the guide pin 8 is centrally arranged therein. The other end of the guide pin 8 is arranged so that it is displaceable in the longitudinal direction within an insulating tube 6 fixedly secured to a setscrew 5 so that the guide pin 8 is insulated with respect to the housing. Two electrically conductive contact pieces 2 having identical masses are arranged for axial displacement on the guide pin 8. A helical compression spring 7 is disposed between the two contact pieces and rests on an annular shoulder 14 provided on each contact piece. Each contact piece is provided with an annular contact surface 15 and the spring 7 serves for biasing the contact surface of one of the two contact pieces 2 into electrically conductive connection with a fixed contact surface 16 arranged in the housing, and for biasing the annular contact surface of the other contact piece in electrically conductive connection with a contact surface 17 or a setscrew 5. The setscrew 5 is threadly adjustable in the axial direction with respect to the housing by means of a thread 10 within the bushing 4 which is secured to the housing and electrically insulated therefrom by an insulating ring 3.
Asshown, the housing is provided with the bore 12 which is offset in a stepwise fashion and which is threaded in its external section. The bore 12 is closed by means of the sealing screw 11 provided with a conical tip for forming a metallic seal with the relatively sharp annular edge 13. The bore 12 is utilized for inserting an attenuating medium into the interior of the housing. The medium may be a gas or a liquid such as silicone oil or glycerin and depending upon the viscosity of the medium introduced into the housing a predetermined attenuation or damping of the motion of the movable contact pieces is obtained. Thus, the switching characteristics which is governed by the movement of the contact pieces may be easily varied. In addition, the attenuating medium may serve the dual purpose of providing corrosion protection of the contact portions of the switch.
The desired deceleration or acceleration sensitivity is adjusted by turning the setscrew 5 and after the predetermined value is set, the setscrew is soldered to the bushing 4 to form a solder joint 20. By this solder joint the setscrew is secured against rotation and simultaneously the internal space of the housing is hermetically sealed with respect to the outside atmosphere. A lead 18 is connected to the solder joint 20 and a lead 19 is connected to electrically conductive housing 1 to form a conductive path between the leads via the contact pieces and the housing.
In the rest position of the switch, i.e., without effective accelerative or decelerative forces, a current flows via the lead 18 and the solder joint 20 into the setscrew 5 to the contact surface 17. One of the two contact pieces 2 is in electrically conductive connection with the contact surface 17, via its annular contact surface 15 due to the spring force effective on this contact piece. From the annular contact surface 15, the current flows through the contact piece 2 to the shoulder 14 and from there into the compression spring 7. The compression spring 7 is connected to the other contact piece 2 in the same manner and forms a conductive path such that the current flows via the opposed contact piece 2 to the annular contact surface thereof which, due to the spring force, is in electrically conductive connection with the fixed contact surface 16 of the housing. From the contact surface 16, the current flows through the housing 1 to the lead 19. It is, of course, also possible for the current flow to take place in the reverse direction.
In response to an accelerative or decelerative force above the predetermined value from one of the two axial directions, the annular contact surface 15 of one of the two contact pieces 2 is lifted from the contact surface 16 or from the contact surface 17 depending on the force direction against the bias of the spring as shown in FIG. 2. Thus, the current flow is interrupted and, by this switching operation, an electrically operated device is caused to function.
As can readily be seen from the drawing, the switch is completely insensitive to positive or negative transverse accelerations, since the contact pieces 2 are prevented from contacting the surrounding housing by the guide pin 8. However, it is of course possible to eliminate the guide pin 8 by ensuring that the peripheries of contact pieces 2 cannot come into conductive contact with the surrounding housing. This may be accomplished by providing the contact pieces with an external insulation and/or by internally insulating the housing. Likewise, it is also feasible to manufacture the housing from a nonconductive material. In this case, it is of course necessary to provide an appropriate arrangement for the current flow.
FIG. 3 illustrates another embodiment of a switch according to the present invention which corresponds in its mode of operation and in its switching characteristic to the switch of FIGS. 1 and 2. In this embodiment, the contact pieces 2 and 2a are formed with different masses such that an acceleration and/or deceleration response characteristic of the contact pieces is obtained in the direction of the extension of guide pin 8 which is inversely proportional to the ratio of the masses of the contact pieces. The greater acceleration and/or deceleration response characteristic is provided, of course, by the contact piece 2 exhibiting the larger mass. That is, the larger mass will respond to smaller acceleration or deceleration values. FIG. 4 illustrates the interrupting position of the larger contact piece. Here again, an insensitivity to transverse acceleration is provided by the guide pin. As in the prior embodiment, the switch becomes responsive only when an accelerative or decelerative force becomes effective which emanates directly from one of the two axial directions and is above the predetermined value, or when the axial component of an accelerative or decelerative force effective from another direction surpasses this set value.
In FIG. 5, there is shown another switch embodiment which corresponds in function and switching characteristic to the switches of FIGS. 14. However, in this embodiment, there is no provision for adjustable setting the desired accelerative or decelerative value by means of an adjustable setscrew. Thus, in contrast to FIGS. 1-4, the switch of FIG. 5 is provided with a contact surface 21 for one of the two contact pieces 2 formed directly at the bushing 4 such that a predetermined value is set upon manufacturing. Here again, the contact pieces 2 are constructed with the same mass, so that the switch exhibits the same acceleration and deceleration sensitivity in both longitudinal directions. The switch of FIG. 6 corresponds to that of FIG. 5 except for the differently proportioned masses for the contact pieces 2 and 2a.
A somewhat modified embodiment of the switch of this invention is shown in FIGS. 7 and 8, that is, a switch having only one single movable contact piece 2. In order to ensure that the contact piece is pressed against the contact surface 16 by the helical compression spring 7, the setscrew 5 is formed with the shoulder 14 against which the spring rests. It is readily apparent that this switch responds only in a single direction, so that it must be installed, depending on whether it is to respond to acceleration or deceleration, in an appropriate manner within the associated device. In this embodiment, the desired sensitivity to acceleration or deceleration forces can be adjusted as desired by turning the setscrew. After this value has been set, the setscrew may be soldered to the bushing to seal the interior of the housing hermetically with respect to the outside atmosphere.
FIGS. 9 and 10 show a further embodiment of the switch according to the present invention, without a guide pin 8. In this embodiment, the housing 1 is provided with a threaded bore 29 at one end, the setscrew 23 being threadedly inserted therein. The setscrew is provided with a section 23a which is offset in a stepwise manner and has a beveled front end 24. This section 23a is surrounded by an electrically insulating tube 22 in order to prevent another electrically conductive contact being established between the contact piece and the counter contact surface as a result of any occurring shocks from different directions which could cause a swinging motion of the bell-shaped contact pieces 2. A pin 25 constructed similar to the setscrew 23 is secured to the housing and electrically insulated therefrom by a bushing 26 which may include, for example, an insulating glass sleeve 30. As shown, the bushing 26 is attached within the housing 1 by means of flange 28. The electrical connection is effected at the two contacts 23 and 25 which form the terminals for the switch. The switch is adjusted to the desired acceleration and/or deceleration sensitivity by biasing the spring 7 against the contact pieces 2 by turning the setscrew 23 to obtain the desired value. Thus, when the value is exceeded, the contact piece is lifted from the corresponding contact surface and interrupts the electrically conductive connection between the setscrew 23 and the pin 25 representing the counter contact. The adjusted value can again be fixed by soldering the setscrew to the housing. Since both contact pieces 2 are biased by the helical spring 7, the adjusted response value holds true for both axial directions. That is if the masses of the two contact pieces 2are equal, the switch responds at the same value in both directions.
In the rest position of this switch, the current flows from the setscrew 23 via the contact piece'2, the spring 7, the other contact piece 2 and to the pin 25. Accordingly, when an accelerative or decelerative force is effective on the switch which is larger than the set sensitivity value, the current flow is interrupted at the annular edge of the contact pieces 2, depending on the direction of the active force, toward the counter contact 23 or 25, respectively, and the desired switching process of the device to be actuated is initiated. it is readily apparent that this switch embodiment may also be provided with contact pieces having different masses to obtain inversely proportional response characteristics for deceleration and acceleration. Likewise, it is also possible in this embodiment of the switch to provide only a single contact piece. However, in such an arrangement, care must again be taken that the switch is installed in the proper direction for response.
While we have shown and described several embodiments of the switch of the present invention, it is understood that the switch is not limited thereto and may be modified and utilized in a great variety of ways. For example, several of the contact-pieces or contact piece spring systems may be installed into a housing or other device in different directions and connected for example, by a series connection. Thus, an arrangement is attained which will be responsive to a specific accelerative or decelerative force from one of three dimensional directions with one of the contact pieces being lifted from the corresponding contact surface such that the contact within the entire system is interrupted in the desired manner. We therefore do not wish to be limited to the details shown and described herein, but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.
1. An electric switch responsive to acceleration and- /or deceleration comprising a housing, two contact pieces movably disposed in said housing, a corresponding contact surface for each of said contact pieces mounted within said housing, each of said contact pieces and said corresponding contact surface being electrically conductive, means for biasing each of said contact pieces into electrically conductive connection with said corresponding contact surface said biasing means providing a constantly effective force ofa predetermined magnitude, each of said contact pieces being responsive to an acceleration force of a predetermined value in a different predetermined direction for overcoming the force of said biasing means and for moving out of electrically conductive connection with said corresponding contact surface, whereby a conductive circuit path trhough said switch is interrupted.
2. An electric switch as defined in claim ll including means arranged in said housing for mounting said contact pieces to control the directions of movement thereof within said housing.
3. An electrical switch as defined in claim 2 wherein said mounting means is a pin having said contact pieces mounted thereon for axial displacement therealong.
4. An electric switch as defined in claim 1 wherein said biasing means is a spring.
5. An electric switch as defined in claim 11 wherein said biasing means is a helical spring.
6. An electric switch as defined in claim ll including means for varying the magnitude of the constantly effective force provided by said biasing means.
7. An electric switch as defined in claim 6 wherein said biasing means is a helical spring and said means for varying the magnitude of force of said spring is an adjustable screw means biasing said spring to vary the compression thereof.
8. An electric switch as defined in claim 1 and further including an attenuating medium filling the interior of said housing.
9. An electric switch as defined in claim 8 wherein said attenuating medium is a gas.
10. An electric switch as defined in claim 8 wherein said attenuating medium is a liquid.
illl. An electric switch as defined in claim 1 wherein, each of said contact pieces has a different mass for responding to different values of acceleration in a predetermined direction.
12. An electric switch as defined in claim 1 including means for hermetrically sealing said housing to provide an airtight interior.
13. An electric switch as defined in claim ii wherein said biasing means is a helical spring with the constantly effective force of a predetermined magnitude being determined by the axial extent of said spring when said contact pieces are in electrically conductive connection with said corresponding contact surface, and adjusting means for controlling the axial extent of said spring within said housing to vary the magnitude of the constantly effective force.
14. An electric switch as defined in claim 13 wherein said adjusting means is an adjustable screw element having a portion thereof in contact with one end of said spring.
115. An electric switch as defined in claim 13, wherein each of said contact pieces has the corresponding contact surface arranged at opposite ends of said housing, said spring being arranged in said housing in contact with each of said contact pieces for biasing said contact pieces in opposite directions into electrically conductive contact with said corresponding contact surfaces with a constantly effective force having a magnitude determined by the axial extent of said spring when said contact pieces are in electrically conductive connection with said corresponding contact surface.
16. An electric switch as defined in claim 15 wherein said adjusting means is an adjustable screw element having a portion thereof forming one of said contact surfaces whereby the positioning of the contact surface within said housing determines the biasing of said spring means.
17. An electric switch as defined in claim llti wherein said two contact pieces are of the same mass.
118. An electric switch as defined in claim 16 wherein said two contact pieces are of different masses.
19. An electric switch as defined in claim 16 including an attenuating medium filling the interior of said housing.
20. An electric switch as defined in claim ii, wherein said contact pieces are responsive to acceleration forces in opposite directions.