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Title:
INERTIA SWITCH DEVICE
Document Type and Number:
WIPO Patent Application WO/1981/000325
Kind Code:
A1
Abstract:
The inertia switch device (1) comprises an inertia mass (6) which is movable from a rest position when the device is subjected to an applied acceleration or deceleration in a horizontal plane, a first electrical contact (5) movable between a first stable position in which it engages a second electrical contact (3) and a second stable position in which it no longer engages the second electrical contact, and support means (4) having a bifurcated portion (24) for carrying a bifurcated portion of the first electrical contact (5). An operating means (27) is struck by the inertia mass (6), when the applied acceleration or deceleration exceeds a threshold value and moves the first electrical contact (5) from the first to the second stable position. The operating means (27) has a first limb (31) which is struck by the inertia mass and a second limb (28) with a bifurcated portion which is pivotally mounted on the support means. A resilient biassing means (34) lies within the bifurcated portions and connects the first electrical contact (5) and the second limb (28) so as to bias the first electrical contact (5) towards the first or second stable position. A resetting means has an operating member (35) movable to operate the resilient biassing means (34) and thereby return the first electrical contact (5) to its original stable position.

Inventors:
Crick, Jackman D. P.
Application Number:
PCT/GB1980/000117
Publication Date:
February 05, 1981
Filing Date:
July 10, 1980
Export Citation:
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Assignee:
FIRST INERTIA SWITCH LTD CRICK D JACKMAN P.
International Classes:
H01H35/14; (IPC1-7): H01H35/14
Domestic Patent References:
WO1979000500A11979-08-09
Foreign References:
US2206067A1940-07-02
CH538187A1973-06-15
Download PDF:
Claims:
Claims
1. An inertia switch device (1) comprising: an inertia mass (6) which is movable from a rest posi¬ tion when the device is subjected to an . applied accele¬ ration or deceleration in a horizontal plane; a first electrical contact (5) movable between a first stable position in which it engages a second electrical contact (3) and a second stable position in which it no longer engages the second electrical contact; support means (4) having a bifurcated portion (24) for carrying a bifurcated portion of the first electrical contact (5) ; operating means (27) engageable by the inertia mass (6), on movement of the inertia mass as a result of the applied acceleration or deceleration exceeding a thres¬ hold value, to move the first electrical ' contact (5) from the first to the second stable position, or vice versa; the operating means (27) comprising a first limb (3D which is struck by the inertia mass (6) when the thres¬ hold value is exceeded and a second limb (28) having a bifurcated portion .which is pivotally mounted on the support means; resilient biassing means (34) which lie within the bifurcated portions and connect the first electrical contact (.5) and the second limb (28) so as to bias the first electrical contact (5) towards the first or second stable position depending on the position, of the second limb (28); characterized by: resetting means comprising an operating member (35) movable to operate the resilient biassing means (34) and thereby return the first electrical contact (5) to its original stable position. OMPI m IPO .
2. An inertia switch device as claimed in Claim 1, characterized in that the operating member (35) is arranged to actuate a linkage (59) which bears against the resilient biassing means (34) to return the first electrical contact (5) to its original stable position.
3. An inertia switch device as claimed in Claim 1 or Claim 2, characterized in that the operating member (35) is arranged to actuate a cranked lever (68) which bears against the resilient biassing means to return the first electrical contact (5) to its original stable position.
4. An inertia switch device as claimed in Claim 3, characterized in that the cranked lever (68) has two limbs (58, 69) which extend substantially at right angles to each other and are located at opposite ends of a pivotally mounted shaft (70).
5. An inertia switch device as claimed in any preceding claim, characterized in that the resilient biassing means (34) compriss a helical tension spring hooked at opposite ends into respective holes in the first ele trical contact (5) and the second limb (28) of the operating means (27) •.
6. An inertia switch device as claimed in any preceding claim, characterized by a housing (2) which ' ccommodates the inertia mass (6), the electrical contacts (3,5), the operating means (27) and the resilient biassing means (34), and in that the operating member (35) .extends' out of the housing by an amount which provides a visual indication as to whether the operating means (27) have been struck by the inertia mass. O • WI .
7. An inertia switch device as claimed in Claim 6, characterized in that the electrical contacts ( 3»5) are respectively connected to two electrical terminals (13, 14) accesible from the exterior of the housing.
8. An inertia switch as claimed in Claim 6 or Claim 7, characterized in that the operating member (35) is slidably mounted in the housing (2) and extends through an upper wall (61) of the housing.
9. An inertia switch device as claimed in any preceding claim, characterized in that the operating means (27) is engageable by a second inertia mass (7) which tends to maintain an initial rest position when the device is subjected to an applied angular rotation about an axis substantially parallel to said horizontal plane and which is also arranged to operate the electrical con¬ tacts (3»5) when the applied angular rotation exceeds a predetermined value.
10. An inertia switch device as claimed in Claim 9, characterized in that the second inertia mass (7) is slidably mounted to produce operation of the electrical contacts (3»5) when the device is subjected to said applied angular rotation.
11. An inertia switch device as claimed in Claim 9 or Claim 10, characterized in that the second inertia mass (7) comprises a block (37) slidably mounted within a compartment (38) and arranged to resist operation of the electrical contacts (3, 5) by a force applied in a direction normal to the horizontal plane by a peg on the block engaging in a slot provided in the compartment. OMPI .
12. An inertia switch device as claimed in Clam 9 or Claim 10, characterized in that the second inertia mass (7) comprises a block (37) slidably mounted in a com¬ partment (38) and arranged to resist operation of the electrical contacts (3>5) by a force applied in a direction normal to the horizontal plane by a .peg on the block engaging in a slot provided in the compart¬ ment.
13. An inertia switch device as claimed in Claim 11 or Claim 12, characterized in that the slot has an inverted Ushape, and the peg is arranged to engage the slot at a position at the apex of the inverted Ushape and to move along one of the arms of the slot depending on the direction of angular rotation of the device.
14. An inertia switch device as claimed in claim 9, characterized in that the second inertia mass (7) is pivotally mounted to produced operation of the elec¬ trical contacts (3, 5) when the device is subjected to said applied angular rotation.
15. An inertia switch device as claimed in Claim 9 or Claim 14, characterized in that the second inertia mass (7) comprises a block pivotally mounted so as to resist operation of the electrical contacts (3, 5) by a force applied in a direction normal to the horizontal plane.
16. An inertia switch device as claimed in Clam 15, characterized in that the pivotally mounted block is hemi cylindrical.
17. An inertia switch device as claimed in Claim 15 or Claim 16, characterized in that the operation of the electrical contacts (3, 5) is produced by a cam follower arranged to cooperate wih a cam rotationally fast with the pivotally mounted block.
18. An inertia switch device as claimed in any one of Claims 9 to 17, characterized in that the electrical contacts are arranged . to be operated when the applied angular rotation exceeds 90 degrees. OMPI.
Description:
nertia Switch Device

Technical Field of the Invention

This invention relates to an inertia switch device for opening or closing electrical contacts in response to movement of the device .

Background Art

Devices of this kind are known in which an inertia mass held in an operative position by a spring or a magnet is freed by an acceleration or a deceleration of a pre¬ determined intensity to effect the opening or closing of the electrical contacts. Such devices are usually mounted in a vehicle in a position such that they respond to acceleration or deceleration in a horizontal direc¬ tion, so that if the vehicle is subject to an impact from the front, the side, or the rear, the electrical contacts are operated. It is a disadvantage of such devices that they may not be capable of being easily reset to their original, unoperated, condition.

An object of this invention is to provide an inertia switch device which mitigates this disadvantage.

Disclosure of the Invention.

According to one aspect of the present invention an inertia switch device comprises an an inertia mass which is movable from a rest position when the device is subjected to an applied acceleration or deceleration in a horizontal plane, a first electrical contact movable between a first stable position in which it engages a second electrical contact and a second stable position in which it no longer engages the second electrical

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contact, support means having a bifurcated portion for carrying a bifurcated portion of the first electrical contact, operating means engageable by the inertia mass on movement of the inertia mass as a result of the applied acceleration or deceleration exceeding a thres¬ hold value, to move the first electrical contact from the first to the second stable position, or vice versa, the operating means comprising a first limb which is struck by the inertia mass when the threshold value is exceeded and a second limb having a bifurcated portion which is pivotally mounted on the support means, resi¬ lient biassing means which lie within the bifurcated portions and connect the first electrical contact and the second limb so as to bias the first electrical contact towards the first or second stable position depending on the position of the second limb, and resetting means ' comprising an operating member- movable to operate the resilient biassing means and thereby return the first electrical contact to its original stable position.

Conveniently the operating member may be arranged to actuate a linkage which bears against the resilient biassing means to return the first electrical contact to its original stable position.

Preferably the operating member is arranged to actuate a cranked lever which bears against the resilient biassing means to return the first electrical contact to its original stable position.

The resilient biassing means may comprise a helical tension spring hooked at opposite ends into respective holes in the first electrical contact and the second limb of the operating means.

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The inertia mass, the electrical contacts, the operating means and the resilient biassing means may be accommo¬ dated in a housing and the operating member may extend out of the housing by an amount which provides a visual indication as to whether or not the operating means have been struck by the inertia mass.

It is also a disadvantage of some inertia switch devices that they do not necessarily respond and operate the electrical contacts if the device is subjected to a rotary .motion such as that occurring when the vehicle rolls about its longitudinal axis.

Furthermore, where such devices are designed to operate the electrical contacts in response to rotary motion of the vehicle, this may be accompanied by a tendency to operate the electrical contacts in response to a rela¬ tively low. force applied in a vertical direction. This is disadvantageous in that the device may respond to forces applied in a vertical direction such as are caused by bumps in a road along which the vehicle is travelling.

According to another aspect of the present invention an inertia switch device comprises an inertia mass which is movable from a rest position when the device is sub¬ jected to an applied acceleration or deceleration in a horizontal plane, electrical contacts operable by the inertia mass on movement of the inertia mass as a result of the applied acceleration or deceleration in said horizontal plane exceeding a predtermined value, and a second inertia mass which tends to maintain an initial rest position when -the device is subjected to an applied

angular rotation about an axis substantially parallel to said horizontal plane and which is also arranged to operate the electrical contacts when the applied angular rotation exceeds a predetermined value.

The inertia switch device of the invention has the advantage that the operation of the electrical contacts occurs when the angular rotation exceeds the predeter¬ mined value such as occurs when the vehicle rolls about its longitudinal axis.

The second inertia mass may be slidably mounted to produce operation of the electrical contacts when the device is subjected to said applied angular rotation. Conveniently, the second inertia mass may comprise a block slidably mounted within a compartment and arranged to resist operation of the electrical contacts by a force applied in a direction, normal to the horizontal plane by peg in the compartment engaging a slot provided in the block or by a peg on the block engaging a slot provided in the compartment.

The slot may have an inverted U-shape and the peg may be arranged to engage the slot at a position at the apex of the inverted U-shape and to move along one of the arms of the slot depending on the direction of the angular rotation of the device .

The inertia switch device of the invention therefore has the additional advantage that it will resist operation of the electrical contacts by forces applied in a direction normal to the horizontal plane such as are caused by bumps in a road along which the vehicle is travelling.

Alternatively, the second inertia mass may be pivotally mounted to produce operation of the electrical contacts when the device is subjected to said applied angular rotation.

Suitably, the second inertia mass may comprise a block pivotally mounted so as to resist operation by a force applied in a direction normal to the horizontal plane.

The pivotally mounted block, may be hemi-cylindrical and the operation . of the electrical contacts may be produced by a cam follower arranged to co-operate with a cam rotationally fast with the pivotally mounted block.

Embodiments of the invention in both its aspects are hereinafter described, by way of example, with reference to the accompanying drawings.

Brief Description of the Drawings

Figure 1 is a longitudinal cross-sectional vie ' of an inertia switch device in accordance with the invention;

Figure 2 is a cross-section on the line II - II in Figure 1, looking in the direction of the arrows;

Figure 3 is an under plan view of. a cranked lever shown in end elevation in Figure 1.

Figure 4 is a side elevation of the cranked lever shown in Figure 3.

Figure 5 is a longitudinal cross-sectional view of another inertia switch device in accordance with the invention having a second inertia mass;

Figure 6 is a perspective view of the second inertia mass shown in Figure 5;

Figure 7 is a fragmentary perspective view of a re¬ taining peg shown in Figure 5 ; and

Figure 8 is a perspective view of an alternative form of the second inertia mass- shown in Figure 5.

Best Modes for Carrying out the Invention

Referring in the first .instance to Figures 1 to 4, the inertia switch device 1 has a housing 2 of electrically insulating material in which are mounted two fixed electrical terminals 3 and -4 and a movable electrical contact member 5. The housing 2 also accommodates an inertia mass 6 responsive to acceleration or decele¬ ration of the device 1 acting in a substantially hori¬ zontal direction when the. device, is mounted in the attitude illustrated in Figure 1.

The inertia mass 6 comprises a spherical steel ball which normally rests on the bottom 8 of a frusto-conical seat 9 and is restrained in this position by a permanent magnet 10. The force exerted by the magnet 10 on the ball 5 is such that it is overcome by the attainment of the predetermined threshold value of acceleration or deceleration in a horizontal plane acting .on the device 1 and thus on the ball 6. When this, threshold value is attained the ball 6 moves away ' from the bottom 8 of the frusto-conical seat 9 and rides up the sloping side 11.

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The electrical terminals 3 and 4 have respective lower portions 13 and 14 which lie parallel to one another and extend through a wall 15 into a recess 16 from which they are accessible from the outside of the housing 2 for the connection of electrical conductors thereto. The upper part of the electrical terminal 3 f wh.ich extends through a wall 18, is cranked and has a verti¬ cally extending portion 19 which co-operates with a rounded portion 20 of the movable contact member 5. The upper part of the electrical terminal 4 also extends through the wall 18 and has a horizontally extending portion which terminates in a bifurcated end portion, each of the two limbs 24 of which has an indentation 25 in its upper surface.

The upper part of the movable contact member 5 is bifurcated the two limbs 26 forming the bifurcation bearing against respective indentations * in the underside of the two limbs 24. A contact actuating member 27, which is generally L-shaped, has a bifurcated arm 28, the limbs 29 of which are seated for pivotal movement in the indentations 25 in the upper surface of the limbs 24 of the terminal 4. The other arm 31 of the actuating member 27 extends over the ball 6 and rests on the upper surface of the seat 9 in which the inertia mass 6 is accommodated. A helical tension spring 34, hooked at opposite ends into a hole in the contact * actuating member 27 and a hole in the movable contact member 5, lies between the limbs of the bifurcations of these members 27, 4 and 5 and normally -acts to urge the movable contact member 5 against the fixed terminal 3 and to urge the arm 31 of the actuating member 27 towards the ball 6.

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A reset button 35 is slidably mounted in the housing 2 so that its lower end 36 engages a limb 58 of a linkage 59. The reset button 35 has a rectangular head 60 which projects from the upper wall 61 of the housing 2 and a stem 62 which extends into the interior of the housing 2 through a slot 63 formed between two upstanding shoul¬ ders 64 on the upper surface 61 of the housing 2. Abutments 65 and 66 formed on the wall of the housing act as guides for the stem 62 during sliding movement of the res.et button 35.

The linkage 59 takes the form of a cranked lever 68 having two limbs 58 and 69 (see Figures 3 and 4) which extend substantially at right angles to each other and are located adjacent opposite ends of a shaft 70 which is pivotally mounted in the housing 2. The end of the limb 69 is arranged to engage the spring 34 and the end of limb 58 is provided with a notch 71 which is engaged by the lower end of the stem 62.

In use of the inertia switch device shown in Figure 1 to 4, the device 1 is mounted n a vehicle with the base 51 of the housing 2 in a substantially horizontal plane with the rounded portion 20 of the moving contact member 5 engaging the portion 19 of of the electrical terminal 4. The arm 1 of the actuating member 27 extends over the ball 6 - and rests on the upper surface of the seat 9 as seen in Figure 1-. The electrical terminals 3 and 4 are connected to electrical circuits (not shown) for electrically operated door locks of the vehicle or for an electrically operated supply valve in a fuel pump or a fuel supply pipe of the vehicle.

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If there is an accident, such that an acceleration or deceleration in a horizontal plane in excess of a predetermined value is applied to the device 1 , the inertia mass 6 will ride up the sloping side 11 of the frusto-conical seat 9 and strike the arm 31 of the actuating member 27. The arm 31 is moved upwards until it comes to rest against a series of ribs 12 on the under¬ side of the upper wall 61 of the housing 2. This causes the spring 3 to move "over centre" so that the rounded portion 20 of the movable contact member 5 is moved away from the vertically extending portion 19 of the elec¬ trical terminal 3- Thus the electrical circuit for the electrically operated door locks or the electrically operated supply valve is broken, so that the door locks are released and the supply of fuel is cut off.

The spring 34 bears against the end of the limb 58 of the cranked lever 68 causing it to rotate in an anti- clock-wise direction as seen in Figure 1 so that the end of the limb 58 bears against the lower end 36 . of the stem 62 and pushes the reset button 35 in an upward direction. The inertia swi-tch device 1 remains in this conditon until it is reset. The displacing of the reset button 35 in an upward direction provides a visual indication that the inertia mass 6 has struck the arm 31 of the actuating member 27-

The inertia switch device 1 is reset by depressing the reset button 35 which actuates the linkage 59 and returns the mechanism to its original position. Depress¬ ing rectangular head 60 towards the wall 61 of the housing 2 causes the lower end of the stem 62 to engage the notch 61 in the end of the limb 58 of the cranked

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lever 68 causing it to rotate in clockwise direction. The end of the limb 69 bears against the spring 34 an causes it to move "over centre" so that the rounded portion 20 of the movable contact member 5 engages th vertically extending portion 19 of the electrica terminal 3. The lower position of head 60 of the rese button indicates that the switch device 1 has been reset.

Turning now to Figures 5 to 7 , the inertia switch device 1 is generally similar .to that shown in Figures 1 to but differs therefrom in that it includes a furthe inertia mass 7 responsive to angular rotation. The inertia mass 7 comprises a metal block 37 arranged t slide within the substantially rectangular compartment 33 within the housing 2 in response to angular rotation of device " 1 about an axis 39. The extent and direction of the sliding movement of the metal block 37 is con¬ trolled by a. peg 40. which lies within an inverted U- shaped slot 41 provided on side 42 of the metal bloc 37. The metal block 37 tapers towards its upper end - 4 and its broader, lower end 44 normally rests on the bottom 45 of the compartment 33.

The peg 40, which is anchored in a wall 32 of the housing 2, normally projects into the slot 41 at a position at the apex of the inverted ϋ and tends to keep the block 37 at or near to the bottom 45 of the com¬ partment 33 when the device 1 is subjected to a force applied in a vertical direction such as is caused by a bump in a road along which a vehicle is travelling. When the metal block 37 is in this normal position the upper end 43 lies just below an. end portion 49 of the arm 31 of the actuating member 27 which extends through a slot 50 in the wall 32.

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In use of the inertia switch device shown in Figures 5 to 7, the device 1 is mounted on the vehicle with the base 51 of the housing 2 in a substantially horizontal plane and the axis 39 substantially parallel to the longi¬ tudinal axis of the vehicle. The electrical terminals 3 and 4 are connected to electrical circuits (not shown) for electrically operated door locks of the vehicle or for an electrically operated supply valve in fuel supply pipe of the vehicle.

If there is an accident, such that an acceleration or deceleration in a horizontal plane in excess of a predetermined value is applied to the device 1 , the inertia mass 6 will ride up the sloping side 11 of the frusto-conical seat 9 and strike the arm 31 of the actuating member 27. The arm 31 is moved upwards until it comes to rest against a series " of ribs 72 on the underside of the upper wall 61 of housing 2. This causes the spring 34 to move "over centre" so that the rounded portion 20 of the movable contact member 5 is moved away from the vertically extending portion 19 of the electrical terminal 3. Thus the electrical circuit for the electrically operated door locks or the elec¬ trically operated supply valve is broken, so that the door locks are released and the supply of fuel is cut off.

The spring 3 bears against the end of the limb 59 of the cranked lever 68 causing it to rotate in an anti- clock-wise direction as seen in Figure 5 so that the end of the limb 58 bears against the lower end 36 of the stem 62 and pushes the reset button 35 in an upward direc¬ tion. The inertia switch device 1 remains in this

condition until it is reset. The displacing of the rese button 35 in an upward direction provides a visua indication that the inertia mass 6 has struck the arm 3 of the actuating member 27.

If the accident is such that the acceleration or decele ration is not in excess of the predetermined value, bu the vehicle rolls about its longitudinal axis through a angle in excess of 90 degrees, the device 1 will rotat around the inertia mass 7 which tends to remain in it original rest position in space. The compartment 3 therefore slides around relative to the inertia mass 7, the slot 41 moving around relative to the peg 40 so tha the peg 40 eventually occupies a position along one o the arms 47 or 48 depending on the extent and th direction of the angular rotation of the vehicle. Th upper end 43 of the inertia mass 7 will therefore strik end portion 49 of- the arm 31 of the actuating membe 27. The movable contact member 5 is therefore move away from the . vertically extending portion 19 of th electrical terminal 3 to break the electrical circui for the electrically operated door locks or the elec trically operated fuel supply valve.

The device 1 can be reset when the vehicle has bee returned to its original, upright position by depressin the reset button 35 which actuates the linkage 59 and returns the mechanism to its -original position. Depress ing rectangular head 60 towards the wall 61 of th housing 2 causes the lower end of the stem 62 to engag the notch 61 in the end of the limb 58 of the cranked lever 68 causing it to rotate in clockwise direction. The end of the limb 69 bears against the spring 34 and

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causes it to move "over centre" so that the rounded portion 20 of the movable contact member 5 engages the vertically extending portion 19 of the electrical ter¬ minal 3. The lower position of the head 60 of the reset button indicates that the switch device 1 has been reset. While the embodiment of the invention shown in Figures 5 to 7 has the slot 40 in the block 37 and the peg 41 anchored in a wall 32 of the housing 2 * it will be appreciated that in other embodiments of the invention the peg 40 may be secured to the block 37 and the . slot 41 provided in the wall 32 of the housing.

Turning finally to Figure 8, the alternative form of the inertia mass 7 comprises a substantially hemi- cylindrical block 52 which is pivotally mounted for rotation about an axis 53. The block 52 forming the inertia mass 7 is accommodated in a compartment of the inertia device 1 similar to the compartment 38 shown in Figure 5. A shaft 54, which is rotationally fast with the block 52 and which provides the pivotal mounting, carries a cam 55 at one end which is arranged to co¬ operate with a cam follower 56 slidably mounted in the compartment. An abutment 57 on the upper end of the cam follower 56 is arranged to engage the end portion 49 of the arm 31 of the actuating member 27. When the device 1 is subjected to a force applied in a vertical di¬ rection such aa is caused by a bump in a road along which the vehicle is travelling, the pivotal mounting resists vertical movement so that the block 52 tends to remain in its original position in space.

In the event of an accident such that vehicle rolls about its longitudinal axis through an angle in excess of 90 degrees, the device 1 will rotate around the hemi- cylindrical block 52 forming the inertia mass 7 which tends to remain in its original rest position in space. The cam follower 56 therefore rotates around the cam 55 so that the abutment 57 is urged into engagement with the end portion 49 of the arm 31 of the actuating member 27. The movable contact member 5 is therefore moved- away - from the vertically extending portion 19 of the electrical terminal 3 to break the electrical circuit for the electrically operated door locks or the elec¬ trically operated fuel supply valve. As before the device can be reset by the reset button 35.

While in the embodiments of the invention ' described above the rounded portion 20 of the moving contact member 5 and the portion 19 of the electrical terminal 4 form . "normally closed" contacts, other embodiments of the invention may utilize ' "normally open" contacts or "changeover" contacts.

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