Latch mechanism

Abstract: A vehicle door latch mechanism 10 having a latch bolt 14 adapted to releasably secure a striker, in use, the latch bolt 14 being pivotably mounted to a chassis of the latch mechanism 10 and movable between an open position and a closed position, wherein the latch mechanism further includes a detent mechanism adapted to releasably maintain the latch bolt 14 in the open position. By providing such a detent mechanism the need for a dedicated latch bolt return spring is eliminated

Description: The present invention relates to latch mechanisms for motor vehicle doors. A typical vehicle door latch mechanism essentially comprises a rotatable claw mounted on the vehicle door which co-operates with a striker pin mounted on the vehicle body. The action of closing the door causes the claw to rotate to a closed position whereupon it engages and retains the striker pin. The claw is maintained in a closed position by a sprung pawl which abuts an appropriately shaped portion of the claw. The latch typically includes a claw return spring which holds the claw in an open position ready to receive the striker pin before the door is closed. US 4073519 (Kurozu et al) discloses a latch mechanism that employs a stop in conjunction with a return spring to retain a claw-type latch bolt in an open position. GB 2267119A (Vecamplast Sr1) discloses a latch in which a return spring connects a claw-type latch bolt and an associated pawl, the spring and pawl tooth acting to retain the claw in its open position. It is desirable to eliminate this return spring so as to reduce the number of components in the latch mechanism and consequently make the latch mechanism cheaper and easier to manufacture. Further, the latch mechanism assembly can be made smaller, or alternatively the space vacated by elimination of the spring used to house one or more other components of the latch assembly. According to the present invention there is provided a vehicle door latch mechanism comprising a latch bolt adapted to releasably secure a striker, the latch bolt being mounted to a chassis of the latch mechanism and movable between an open position and a closed position, the latch mechanism further including a detent mechanism adapted to releasably maintain said latch bolt in said open position, the detent mechanism is provided by a recess on one of the latch bolt and chassis and a corresponding projection of the other of said latch bolt and said chassis and characterised in that a portion of the chassis has a reduced wall thickness as compared to a surrounding part of the chassis, enabling resilient deformation of the projection or recess. The provision of a detent mechanism eliminates the need for a dedicated latch bolt return spring to be included in the latch mechanism. Preferably the recess is provided in the latch bolt and the projection on the chassis. In such an embodiment the projection extends laterally from a side of the chassis and the recess is provided in a facing side of the latch bolt. The projection may be provided on a portion of a retention plate of the chassis. In such an embodiment, said portion of the retention plate has a reduced wall thickness when compared to the main body of the retention plate so as enable resilient deformation thereof, in use. Preferably the projection is provided with a rounded edge adapted to engageable in the recess of the latch bolt. One embodiment of the present invention will now be described with reference to the accompanying drawings in which: Figure 1 shows a diagrammatic side view of a latch mechanism wherein the pawl is provided above the claw; Figure 2 shows the cross-sectional view indicated by arrows A-A in Figure 1. Referring to the figure 1 there is shown a latch mechanism generally designated 10. The mechanism 10 includes a pawl 12, a latch bolt in the form of a claw 14, and a retention plate 16. The pawl 12 is pivotally mounted above the claw 14 via a pawl pin 18 which is in turn connected to the retention plate 16. The pawl 12 includes a pawl engagement portion 20. The retention plate 16, in conjunction with further components of the latch mechanism 10 (not shown) which do not move relative to the retention plate 16 during use, form a chassis of the latch mechanism 10. The claw 14 is pivotally mounted on a claw pin 22 which is secured to the retention plate 16. The claw 14 includes a claw jaw 24 and a claw first safety engagement portion 26 and a claw closed engagement portion 27. In figure 1 the claw 14 is shown in an open position. The retention plate 16 includes a mouth 28 adapted to receive a striker pin (not shown). In use, the claw jaw 14 releasably secures the striker pin in the mouth 28 of the retention plate 16. The claw 14 can be secured in its first safety position, by abutment of the pawl engagement portion 20 with the claw first safety engagement portion 26 wherein an associated door is secured from opening though is not in a fully closed position, and the claw can be secured in its closed position, by abutment of the pawl engagement portion 20 with the claw closed engagement portion 27. The claw 14 is held in the open position by the provision of a detent mechanism. In the embodiment of figure 1 the detent mechanism is provided by a sprung latch 30 of the retention plate 16 which co-operates with a corresponding latch recess 32 of the claw 14 when the claw 14 is in the open position. As can be seen from the cross-sectional view in figure 2, a portion 34 of the retention plate 16 corresponding to a lower edge of the mouth 28 is formed so as to bulge laterally towards the claw 14. The thickness of the retention plate 16 in the region of the latch 30 is reduced so as to permit resilient movement thereof. The side of the claw 14 facing the retention plate 16 is provided with ramped recesses 32, 36 sharing a common apex 38. The shallower latch recess 32 is adapted to receive the latch 30 and hold the claw 14 in the open position. The steeper recess 36 is provided so as to smooth the transition of the latch 30 to and from the latch recess 32 as the claw 14 pivots about the claw pin 22, in use.

Claims: A vehicle door latch mechanism (10) comprising a latch bolt (14) adapted to releasably secure a striker, the latch bolt (14) being mounted to a chassis (16) of the latch mechanism and movable between an open position and a closed position, the latch mechanism (10) further including a detent mechanism adapted to releasably maintain the latch bolt (14) in the open position, wherein the detent mechanism is provided by a recess (32) on one of the latch bolt (14) and chassis (16) and a corresponding projection (30) of the other of the latch bolt (14) and the chassis (10) and characterised in that a portion of the chassis (16) has a reduced wall thickness as compared to a surrounding part of the chassis (16), enabling resilient deformation of the projection (30) or recess (32). A latch mechanism as claimed in claim 1 wherein the recess (32) is provided in the latch bolt (14) and the projection (30) on the chassis (16). A latch mechanism as claimed in claim 2 wherein the projection (30) extends laterally from a side of the chassis (16) and the recess (32) is provided in a facing side of the latch bolt (14). A latch mechanism as claimed in any of claims 1 to 3 wherein the projection is provided on a portion (30) of a retention plate (16) of the chassis. A latch mechanism as claimed in claim 4 wherein said portion (30) of the retention plate (16) has a reduced wall thickness when compared to the main body of the retention plate (16) so as enable resilient deformation thereof, in use. A latch mechanism as claimed in any preceding claim wherein the projection (30) is provided with a rounded edge engageable in the recess (32).

Inventors: FAUVEAU AXEL, FISHER SYDNEY EDWARD, FAUVEAU, AXEL, FISHER, SYDNEY EDWARD
Applicants: ARVINMERITOR LIGHT VEHICLE SYS, ARVINMERITOR LIGHT VEHICLE SYSTEMS (UK) LTD
Application year: 2001
Main classification: E05B65
IPC codes: E05B63, E05B65, E05B15