LOCK MECHANISM WITH TWO LOCKING ELEMENTS

Abstract: Lock mechanism having a primary latch member (2) which is displaceable between a disengaged position and an engaged position, and two separate elements (32, 33) provided as a secondary latch member, which are mounted for simultaneous co-operation with the primary latch member to maintain said primary latch member in the engaged position, and are displaceable in opposite directions by manual operation to disengage the primary latch member.

Description: Lockmechanism with two lockingelements. The present invention relates to a lock mechanism. In several fields, lock mechanisms are used in order to protect human life or to secure or retain persons or objects in such a manner that they can be released rapidly and easily when required. Such lock mechanisms are used e.g. in automotive safety belts and other safety belts but the use of these lock mechanisms is of interest also in many other fields. Even if the inven¬ tion has been developed particularly in connection with automotive safety belts it is not limited to this narrow field; the invention can be applied more generally in different technical fields where the same problem is encountered as in connection with automotive safety be! ts . The lock mechanism of an automotive safety belt in the first place must provide a locking of the belt which is so safe that the lock can fulfil the vital function thereof in a reliable manner but at the same time it is required that the lock mechanism can be operated and disengaged without major effort, e.g. in order to release rapidly the user of the automotive safety belt after an accident. Usually, this means that the lock mechanism is operated at a push button or the like, the latching force provided in the lock mechanism by some springs being overcome. Since the push button or other operating member always has a specific inertia mass, shocks and vibrations as well as centrifugal accelera- tion and retardation forces in some cases may cause unintentional operation of the lock mechanism to the disengaged position, the consequences of which can be disastrous when such disengagement occurs at the time , of an accident. In the beginning of the fifties, the first crash tests with passenger cars were performed and then it was established that the average acceleration during the course of a crash will be about 30 g. Therefore, it was supposed to be sufficient that the lock mechanism of automotive safety belts could stand an acceleration of 50 to 60 g without the lock mechanism being sponta¬ neously and unintentionally disengaged. The introduction of automotive safety belts soon advantageously influenced the accident statistics, and it did not last long before there issued national and international regulations regarding the quality of automotive safety belts. However, after some time mysterious accidents occurred wherein the belt lock was disengaged by itself at the time of the accident . proper. Initially it was considered that this was due to incorrect use of the automotive safety belt, e._.g. by the lock tongue being wedged in the lock housing without being engaged with the lock mechanism proper. When this matter was more closely studied, it was found that incorrect use of the automotive safety belt can in fact cause that the lock mechanism will be dis¬ engaged unintentionally. At this time, the roller belts had not appeared so far and therefore it could happen that the belt strap was too slack at the use of the safety belt. When a slack belt strap is suddenly stretched as occurs at an accident, the strap starts to vibrate intensely like a violin string. Further investigations showed that also longitudinal oscilla¬ tions of large amplitude and high frequency can occur in the strap. Furthermore, it was found that also the crash pulse at a collision in the reality comprises a number of acceleration peaks which are considerably larger than it was believed at that time. Under unfortunate conditions, different accelerations there- fore can be superposi tioned one upon the other, which may cause disengagement of the lock mechanism. On the basis of this knowledge and experience it is the purpose of the present invention to provide an improved lock mechanism which as such excludes the possibility that external uncontrolled forces which may arise at the time of the accident proper, act on the lock mechanism in such a manner that said mechanism at a critical instant is unintentionally disengaged. The lock mechanism on which the invention is based, is of the prior art type having a primary latch member which is displaceable between a disengaged position and an engaged position, and a secondary latch member which is arranged to maintain in a locking position the primary latch member in the engaged position and can be manually operated to dis¬ engage the primary latch member. Locks of this type are available in many different embodiments and are amply represented in the patent literature. In this conneciton, only as an example, reference is made to the French patent publica¬ tion 2,379,995 which discloses one embodiment of such a lock mechanism. According to the invention, this lock mechanism for the purpose mentioned has obtained the character- istics according to claim 1. It should be mentioned that it is not novel per se to construct a latch member as two separate elements This is disclosed e.g. in the U.S. patent specification 4,047,267, but in that case the two latch elements engage the lock tongue proper, which comprises an arrow tongue. Thus, another type of lock is concerned wherein the two elements form the primary latch member and moreover are maintained in the engaged position by a spring which biases directly a member which can be operated manually. In this prior art lock mechanism, the circumstances and experience referred to above have not been taken into account, because said member will be exposed to existing forces which cannot be controlled, and therefore " may be actuated uninten- tionally so as to disengage the lock. In order to explain the invention in more detail reference is made to the accompanying drawings in whi ch FIGS. 1 and 2 are diagrammatic longitudinal cross-sectional viewsof a lock mechanism of the type referred to herein in a prior art embodiment thereof, FIGS. 3 and 4 disclose in a corresponding manner another prior art embodiment, FIG. 5 discloses diagrammatical ly the lock of the . invention, FIGS. 6 to 8 disclose diagrammatically different positions of the elements forming the secondary latch member in the lock of the invention, FIG. 9 discloses diagrammatically another embodi¬ ment of the lock mechanism of the invention, FIGS. 10 and 11 disclose a more constructive embodiment of the 1 ock mechanism of the invention in plan view and longitudinal cross-sectional view, respectively, FIG. 12 is a perspective view of the primary latch member, and FIG. 13 is a plan view of the primary latch member of FIG. 12 in a modified embodiment thereof. In FIGS. 1 and 2 there is shown a lock housing 1 having a primary latch member 2 for engagement with a lock tongue 8. In order to maintain the latch member 2 in an engaged position according to FIG. 1 there is provided a secondary latch member 3 which can comprise a pin or the like -and is biased by means of a compression spring 4 to the position in FIG. 1 wherein said secondary latch member is positioned over an engage¬ ment surface 2' of the latch member 2. In this posi¬ tion, the latch member 3 prevents the latch member 2 from disengaging the lock tongue. A push button 5 can be actuated against the bias of a spring 6 to dis¬ place the latch member 3 to the disengaged position, FIG. 2, such that the latch member 2 can be pivoted upwards to disengage the lock tongue. An ejector 7 which is biased by means of a compression spring 9, is provided to eject the lock tongue when disengaged. It is now understood that the push button 5 and/ or the latch member 3 and the spring 4 if the lock mechanism is exposed to a heavy acceleration in the direction of the arrow, will move in such a manner that there is a risk of the lock mechanism being dis¬ engaged, the lock tongue 8 thus being released from the lock housi ng 1. In the lock of FIGS. 3 and 4, the secondary latch member is constructed as a rocker 31. The lock mechanism is in the engaged position in FIG. 3, and when it is to be brought into the disengaged position, the latch member 31 is pivoted in clockwise direction, which means that the lower end of the rocker will move in the direction of the black arrow to the position of FIG. 4. The latch member 31 can be considered a double-armed lever one arm of which engages the primary latch member and the other arm of which is biased by means of the spring 4. If the lower part of the latch member 31 is heavier than the upper part, the lock will be opened at a specific acceleration in the direction of the white arrow. If the upper part of the latch member 31 is heavier than the lower part, the lock will be opened by an acceleration in the opposite direction. Now, it has to be taken into account that the push button 5 has its own inertia which will influence the dynamic of the latch member 31 in one case or the other. It would be possible to balance the latch member 31 and the push button 5 in such a manner that there will be no displacement of the latch member 31 due to linear acceleration. For practical reasons this is not possible, however, because the push button in that case should have different positions due to the lock tongue being inserted into the lock housing or not, and this cannot be accepted in the automotive industry. However, for safety reasons such an arrangement would not be acceptable, because the lock mechanism still would not be latched with regard to rotational move¬ ment, nor with regard to vibration. The lock of FIG. 5 to which reference is now made, is constructed according to the invention. and the elements included therein, which are identical with corresponding elements in the figures previously described, are provided with the same references. The secondary latch member in this case comprises two elements 32 and 33 which are displaceably guided in a slot in the lock housing and are displaceable towards and away from each other. Thus, they can take different positions which are illustrated in FIGS. 5 to 8. In FIG. 5, the lock mechanism is in the normal latching position or engaged position thereof. The mutually engaged .elements 32 and 33 both co-operate with the latch member 2 to maintain this member in the engaged position, the partition line between the el- ements being located substantially centrally on the engagement surface. 2' . In FIG. 6, the elements 32 and 33 are moved apart and the engagement surface 2' is exposed, which means that the lock mechanism is in the disengaged position. In FIG. 7, the lock mechanism is again in the latching position or engaged position. Then, the two elements 32 and 33 under the influence of external forces are both located at the left end of the slot and in that case the element 32 maintains the primary latch member 2 in the engaged position. In FIG. 8, the elements are at the right end of the slot, and in that case the element 33 maintains the primary latch member in the engaged position. FIG. 9 illustrates the application on pivoted elements 32' and 33' , and as will be easily seen, the function will be the same as in case of linearily dis¬ placeable elements. Thus, the important aspect of the lock mechanism according to the invention is that the lock mechanism can be brought to the disengaged position only if the elements forming the secondary latch member both are moved completely apart at the same time. -At rectilinear accelerations or retardations, the lock mechanism will stay in the engaged position, because if one element moves away from the primary latch member 2, the other element will still be in the 1 atching iposi tion . The lock mechanism of FIGS. 6 to 9 is substantially more advantageous than the lock mechanisms avai 1 abl e today; however, it is not completely perfect. If it is assumed that the primary latch member 2 is latched by means of the two elements 32 and 33, FIG. 5, and that the lock suddenly starts to rotate about an axis which extends perpendicularly to the elements and therebetween, or about an axis which extends between the elements, and is substantially parallel thereto, it may occur that the elements are moved apart by the centrifugal acceleration In order to solve this problem, the elements 32 and 33 according to the invention are shaped such that the centre of gravity of the element 32 is located in the area of the element 33, i.e. at that side of the partition line between the elements, which is opposite to the element 32, and the centre of gravity of the element 33 is located in an analogous manner in the area of the element 32. As a consequence thereof the lock mechanism will be more securely latched against the influence of uncontrolled forces, the greater the rotational acceleration and the transl ational accelera¬ tion. In this connection it should be observed particularly that it is not the strength of existing springs that determines if the lock mechanism will open or not. On the contrary, this is determined by geometrical and mechanical factors which can be easily controlled and reproduced. In the constructive embodiment of the lock of the invention according to FIGS. 10 and 11 wherein the same references have been used for elements which are found also in the figures previously described, the element 32 is constructed as part of a frame 320 while the element 33 is constructed as part of a T-piece 330. The elements 32 and 33 have the same position as in FIG. 5, but the centres of gravity of the frame arid the T-piece are reversed in relation to the partition line between the elements 32 and 33 in the manner previously indicated. The primary latch member 2 has a recess 20, FIG. 12, for the stem of the T-piece in order that said stem cannot lock the primary latch member. However, this member has two projecting shoulders 21 , the two elements 32 and 33 which form the secondary latch element, co-operating with said shoulders. Moreover, the latch element ' 2 has a lock detent 22 to engage the lock tongue, and two arms 23 for the pivotal mounting in the lock housing 1. In order to disengage the primary latch member 2 the element 32 must be displaced to the left as seen in FIGS. 10 and 11, i.e. in the opposite direction of the push button 5. This can be achieved by the push button 5 being provided with arms 51 one at each side of the lock, but only one arm is shown in FIG. 10, these arms providing the necessary movement of the element 32, i .e. the frame 320, over rockers 11. Between the elements 32 and 33 a compression spring 12 is provided which orientates the two elements in relation to each other, but which does not determine the level at which the lock mechanism opens by itself at an acceleration, if any, as in case of prior art lock mechanisms. In order to balance completely the lock mechanism it is only necessary to make the frame 320 heavier than the push button 5 and the spring 6 (not shown in FIG. 11) co-operating with the push button. In this connection it shouljd be noted that the rockers .11 comprise auton¬ omous bodies sensi ti v.e„ to rotation, but can actuate only one of the elements 32 and 33, and thus the security of the lock mechanism is not jeopardized as a consequence thereof. If only one of the elements 32 and 33 engages the primary latch member 2 and the acceleration should be reversed, the risk of the latch member 2 being unintentionally disengaged, is exceedingly small , because the overlapping distance is large in relation to the gap in the disengaged position of the other element and corresponds to the thickness of the shoulders 21. The overlapping, distance can be increased by angling the shoulders in the manner shown in FIG. 13 wherein the overlapping distance is indicated a-t 1-. The lock mechanism can be made still more safe by the elements 32 and 33 being divided into several units. Then, these units will form autonomous oscillating masses at vibrations. Each such division will increase the time required for random uncovering of the shoulders 21 with several tenth powers.

Claims: CLAIMS 1. Lock mechanism having a primary latch member (2) which is displaceable between a disengaged position and an engaged position, and a secondary latch member which is arranged to maintain in a locking position the primary latch member in the engaged position and can be manually operated to disengage the primary latch member, c h a r a c t e r i z e d in that the secondary latch member comprises two separate elements (32, 33) for co-operation with the primary latch member. 2. Lock mechanism as claimed in claim 1 , c h a r a c t e r i z e d in that the elements (32, 33) are mutually engaged in the locking position and can be moved apart by the manual operation to dis- engage the primary latch member (2) . 3. Lock mechanism as claimed in claim 2, c h a r a c t e r i z e d in that the elements * (32% 33) are arranged to cover in -the locking position an engagement surface (2 1 ) of the primary atch member. 4. Lock mechanism as claimed in claim 3, c h a r a c t e r i z e d in that the elements (32, 33) can be moved apart by the manual operation to a spacing which is only insignificantly larger than the width of the engagement surface (2') . 5. Lock mechanism as claimed in claim 3 or 4, c h a r a c t e r i z e d in that the partition line between the elements (32, 33) in the locking position is located substantially centrally on the engagement surface (2'). 6. Lock mechanism as claimed in any of claims 2 to 5, c h a r a c t e r i z e d in that the elements (32, 33) can be moved towards and away from each other in one plane. 7. Lock mechanism as claimed in any of claims 2 to 7, c h a r a c t e r i z e d in that the elements (32, 33) are spring-biased to engage each other in the locking position. 8. Lock mechanism as claimed in any of claims 1 • to 7, c h a r a c t e i z e d in that each element (32, 33) has the centre of gravity thereof at the side of the partition line between the elements, whi ch is opposite to said element. 9. Lock mechanism as claimed in claim 8, c h a r a c t e r i z e d in that one element (32) forms part of a frame (320) and the other element forms part of a T-piece (330) the cross beam of which is located inside the frame. 10. Lock mechanism as claimed in claim 9, c h a r a c t e r i z e d in that the primary latch member (2) forms shoulders (21) at each side of the stem of the T-piece (330) for co-operation with the two elements (32, 33) .

Inventors: WEMAN PER-OLOF, WEMAN, PER-OLOF
Applicants: AUTOLIV DEV, AUTOLIV DEVELOPMENT AB
Application year: 1986
Main classification: A44B11
IPC codes: A44B11