Latch mechanism

Abstract: This invention relates to a latch mechanism 10. The latch mechanism 10 comprises a latch bolt 12 rotatably mounted about a pivot 46 on a chassis 11. The latch bolt 12 is movable from an open condition (in which it is free to receive a striker 50 of a motor vehicle) to a closed condition in which the striker is retained by the latch bolt. The latch bolt 12 comprises an overmould 18 of elastomeric material, which defines first, second and third buffers 20, 22, 24. The third buffer 24 is adapted to co-operate with an abutment 42 on the chassis 11 absorb over-travel of the striker 50 when the door of a motor vehicle carrying the latch mechanism 10 is closed (fig 1).

Description: The present invention relates to a latch mechanism. The latch mechanism is primarily, but not exclusively, intended for use on a door of a motor vehicle. It is known for a motor vehicle latch mechanism to have on a latch bolt thereof, incorporated into an over-mould, a first low energy buffer and a second low energy buffer. Such low energy buffers lower the noise of operation of the latch mechanism. In particular, the first low energy buffer can absorb some of the impact between the latch bolt and an open latch abutment as the latch bolt moves under a spring bias into its open condition. When a latch bolt moves into a closed condition, in which the latch bolt retains a striker mounted on the door frame of the motor vehicle, a pawl moves past a first safety abutment of the latch bolt and is spring biased to engage the latch bolt at a closed abutment to maintain its closed condition. The second low energy buffer can absorb some of the impact between the pawl and that portion of the latch bolt between the first safety abutment and closed abutment as the pawl, under its spring bias, moves to engage the closed abutment. When a motor vehicle door is closed, the striker on the door frame engages the latch mechanism. The force of closing the door gives rise to over-travel of the door and hence the latch beyond the closed position. To absorb, and limit to an extent, over-travel, it is known to provide a separate buffer, mounted on a chassis of the latch mechanism in the line of movement of the closing latch bolt. Such a high energy buffer is designed to absorb much higher impact than the first and second low energy buffers of the latch bolt. Due to its large size and other requirements its has been considered necessary to mount the high energy buffer separately on the chassis at additional cost and assembly time. An aim of the invention is to provide a latch mechanism having a simplified over-travel buffer arrangement. Thus according to the present invention there is provided a latch mechanism according to the accompanying independent claims. In that way, there is no need for a separate over-travel buffer on the chassis and the cost and assembly time associated with it. Should the latch bolt also require low energy buffers the overmould can be moulded to incorporate all the different types of buffers. That is preferable to having a combination of buffers on the chassis and buffers on the latch bolt. The applicant is the first to realise that it is possible to provide a single overmoulding on a latch bolt that is capable of absorbing high energy associated with over-travel of the associated door and also low energy impacts associated with various relatively moving components of the latch mechanism. A latch mechanism 10 in accordance with the invention will now be described with reference to the accompanying drawings in which; Figure 1 shows a side view of a latch mechanism in accordance with the invention, and Figure 2 shows the latch mechanism of figure 1, drawn to the same scale, showing only certain components in a latch open position. Referring to figure 1, a latch mechanism 10 comprises a chassis 11 having a latch bolt 12 and a retaining means in the form of a pawl 13 mounted thereon. The chassis I 1 is in the form of a plate. A slot 14 known as a fish mouth is defined on the chassis 11. The latch bolt 12 comprises two arms 15 which define a recess 16. The latch bolt 12 has a overmould 18. The overmould 18 is formed of elastomeric material. The overmould 18 comprises a first buffer 20, a second buffer 22 and a third buffer 24. It is immediately noticeable from figure 1 that the third buffer 24 is much larger than the first and second buffers 20, 22. The first buffer 20 comprises a small cavity 26 bound by a small loop 28 of the overmould 18. The second buffer 22 is similarly formed. The third buffer 24 comprises a first large cavity 30 and a second large cavity 32, the cavities 30, 32 being bound by successive first and second large loops 34, 36 of the overmould 18. The first and second large cavities 30, 32 are of elongate form. The ends of each large cavity 30, 32 are of increased width and rounded so as to confer a bone shaped appearance to the large cavities 30, 32 in cross section. The first large cavity 30 is longer than the second large cavity 32. The pawl 13 comprises an impact surface 38 and an engaging surface 40 defining a pawl tooth 39. The latch bolt 12 has a closed abutment 41 adapted to engage the engaging surface 40 of the pawl 13. The latch bolt 12 comprises a first safety abutment 25 at its periphery between the recess 16 and the third buffer 24. The chassis 11 comprises an over-travel abutment 42 and an open latch abutment 44. The latch bolt 12 is rotatably mounted at a first pivot 46 (having a pivot axis 47) on the chassis 11. The pawl 13 is rotatably mounted at a second pivot 48 on the chassis 11. The latch bolt 12 is biased by biasing means (not shown) anticlockwise about the first pivot 46 as shown in figure 1. The pawl 13 is biased by further biasing means (not shown) clockwise about second pivot 48 (having a pivot axis 49) as shown in figure 1. It will be appreciated that the first buffer 20 is at the same radial distance from pivot 46 as open latch abutment 44 i.e. it is rotationally in line with the open latch abutment 44, the open latch abutment lying anticlockwise of the first buffer as shown in figure 1. It will also be appreciated that the third buffer 24 is rotationally in line with the over-travel abutment 42, the over-travel abutment lying clockwise of the third buffer as shown in figure 1. In use the latch mechanism 10 is mounted on the door (not shown) of a motor vehicle (not shown). A striker indicated at 50 is fixed on a door frame (not shown) of the motor vehicle and is aligned with the slot 14. In an open position of the latch bolt mechanism 10 as shown in figure 2, the latch bolt 12 is biased against the open latch abutment 44 so that the recess 16 aligns with the slot 14, ready to receive the striker 50. As the door (not shown) of the motor vehicle is closed the relative movement between the striker 50 and the latch mechanism 12 causes, the striker to move into the fishmouth slot 14 and the recess 16 of the latch bolt 12 and pushes the latch bolt about the first pivot 46. A leading edge 37 of the third buffer 24 hits the impact surface 38 of the pawl 13 and displaces the pawl anticlockwise as shown in figure 1 against its bias. It will be appreciated that with the impact being between the edge of the third buffer 24 and the metal of the impact surface 38, noise of impact is reduced with respect to the known metal-metal impact. The aforementioned impact rotates the pawl 13 anticlockwise sufficiently for the pawl to move relatively along the periphery of the latch bolt 12, as the latch bolt moves clockwise beneath the pawl, with the pawl jumping past the first safety abutment 25 and moving clockwise (as in Figure 1), under its bias, to strike the second buffer 22. The second buffer 22 absorbs some of the energy of the impact. The latch bolt 12 continues to rotate clockwise until the third buffer 24 hits the over-travel abutment 42. The over-travel abutment 42 deforms the third buffer 24. The first and second large loops 34, 36 are pressed together closing the cavities 30, 32 and absorbing the impact. The further biasing means (not shown) mentioned earlier, biases the pawl 13 clockwise as shown in figure 1 so that the engaging surface 40 of the pawl engages the closed abutment 41 of the latch bolt 12. In that way the latch bolt 12 is not free to rotate under its biasing means into its open condition. When the pawl 13 of figure 1 is lifted, the engaging surface 40 moves out of the recess 16 to allow the latch bolt 12 to rotate anticlockwise under its bias until the first buffer 20 contacts the open latch abutment 44 thereby returning the latch mechanism to its open position. The first buffer 20 absorbs some of the kinetic energy of the latch bolt when the latch bolt 12 rotates from the closed position (shown in figure 1) to the open position described above. The impact on the third buffer 24 is many times the impact on the first and second buffers 20, 22. The applicant is the first to realise that the different magnitudes of impact on the first , second and third buffers 20, 22, 24 can be accommodated by the use of a single overmould. It is clear that the third buffer may comprise any number of independently moveable buffer parts and may comprise any number of cavities. While the invention has been described with reference to a rotary latch bolt 12, it could easily be applied to a linear latch bolt. Figure 1 shows three lines, X, Y and Z, all of which are radially orientated relative to axis 47 of pivot 46 of the latch bolt 12. Line X passes through the fully closed abutment 41 and line Y passes through the first safety abutment 25. The angle subtended between these lines is A. Line Z passes through an edge of one of the cavities, in this case cavity 32. It will be appreciated that line Z is the most anticlockwise orientated line (when considering axis 47) which nevertheless passes through an edge of one of the cavities. Thus, angle B (the angle subtended at axis 47 between lines Y and Z) is the smallest angle subtended at axis 47 between a radial line passing through first safety abutment 25 and a radial line passing through an edge of one of the overtravel buffer cavities. In particular, angle A is greater than angle B. This provides for a compact latch since the overtravel cavities can be positioned circumferentially close to the first safety abutment. Consideration of figure 2 shows a line L drawn between axis 47 of pivot 46 of the latch bolt and the pawl tooth 39. It will be appreciated that the whole of cavity 32 sits to the left of line L and a portion 31 of cavity 30 also sits to the left of line L. Such an arrangement is particularly compact since it allows portions of the overtravel cavities to lie in a position previously occupied by the metal substrate of the latch bolt 12.

Claims: A latch mechanism suitable for a vehicle, the latch mechanism comprising, a chassis, and a latch bolt having an over-mould thereon, and being movably mounted on the chassis between an open position in which it can receive a striker of a vehicle, a closed position in which the striker is capable of being retained by the latch bolt, and an over-travel position in which the striker is in an over-travel position relative to the latch chassis, characterised in that the overmould defines a buffer, comprising at least a first cavity wherein ends of the first cavity are of increased width and the chassis also comprises an abutment for the buffer, wherein the buffer is adapted to co-operate with the abutment to absorb over-travel of the latch bolt in which the cavity is elongate and has an inside surface with an inside surface region proximate the abutment and an inside surface region remote from the abutment in which the inside surface region remote from the abutment bulges towards the inside surface region proximate the abutment. A latch mechanism suitable for a vehicle, the latch mechanism comprising, a chassis, and a latch bolt, having an over-mould thereon, and being movably mounted on the chassis between an open position in which it can receive a striker of a vehicle, a closed position in which the striker is capable of being retained by the latch bolt, and an over-travel position in which the striker is in an over-travel position relative to the latch chassis, characterised in that the overmould defines a buffer, comprising at least a first cavity wherein ends of the first cavity are of increased width and the chassis also comprises an abutment for the buffer, wherein the buffer is adapted to co-operate with the abutment to absorb over-travel of the latch bolt in which the buffer comprises a second cavity substantially similar in shape to the first cavity. A latch mechanism suitable for a vehicle, the latch mechanism comprising, a chassis, and a latch bolt having an over-mould thereon, and being movably mounted on the chassis, between an open position in which it can receive a striker of a vehicle, a closed position in which the striker is capable of being retained by the latch bolt, and an over-travel position in which the striker is in an over-travel position relative to the latch chassis, characterised in that the overmould defines a buffer, comprising at least a first cavity wherein ends of the first cavity are of increased width and the chassis also comprises an abutment for the buffer, wherein the buffer is adapted to co-operate with the abutment to absorb over-travel of the latch bolt in which the overmould comprises a further buffer adapted to absorb an impact between a pawl of the latch mechanism and the latch bolt in which the pawl is operable to retain the latch bolt in one of the closed and first safety position, the further buffer being positioned between a closed abutment of the latch bolt associated with the closed position and a first safety abutment of the latch bolt associated with the first safety position. A latch mechanism according to any preceding claim, wherein the first cavity does not reach the periphery of the over-mould. A latch mechanism according to any preceding claim, wherein the first cavity is elongate. A latch mechanism according to Claim 5, wherein the first cavity is adapted so that its longitudinal axis is perpendicular to the direction of engagement of the buffer with the abutment when the abutment is in contact with the buffer. A latch mechanism according to any preceding claim wherein the first cavity has a single inside surface which is continuously curved. A latch mechanism according to any preceding claim, wherein ends of the first cavity are partially circular such that the cavity is bone shaped. A latch mechanism according to any preceding claim, wherein the buffer comprises a second cavity substantially similar in shape to the first cavity. A latch mechanism according to Claim 9, wherein the first cavity (30) is proximal the abutment and is larger than the second cavity (32) which is remote from the abutment. A latah mechanism according to any preceding claim, wherein the overmould is formed by an elastomeric material. A latch mechanism according to any preceding claim, wherein the buffer is adapted to displace a retaining means as the latch bolt moves from its open position to its closed position. A latch mechanism according to any preceding claim, wherein the overmould comprises a further buffer adapted to absorb an impact between a further component of the latch mechanism and the latch bolt. A latch mechanism according to Claim 13, wherein the further component is an open latch abutment of the chassis contacted by the further buffer as the latch bolt position moves to the open position. A latch mechanism according to Claim 13, wherein the further component is a pawl, the pawl operating to retain the latch bolt in one of a closed and a first safety position, the further buffer being, positioned between a closed abutment of the latch bolt associated with the closed position and a first safety abutment of the latch bolt associated with the first safety position.

Inventors: KALARGEROS NICK, MEJEAN VERONIQUE, SPURR NIGEL, KALARGEROS, NICK, MEJEAN, VERONIQUE, SPURR, NIGEL
Applicants: ARVINMERITOR LIGHT VEHICLE SYS, ARVINMERITOR LIGHT VEHICLE SYSTEMS (UK) LTD
Application year: 2001
Main classification: E05B17
IPC codes: E05B65, E05B17