GB2423333A

GB2423333A - Latch assembly with crank shaft mounting for bolt retention pawl

Info

Publication number: GB2423333A
Application number: GB0503386A
Authority: GB
Inventors: Nigel Victor Spurr
Original assignee: ArvinMeritor Light Vehicle Systems France SA
Current assignee: Inteva Products France SAS
Priority date: 2005-02-18
Filing date: 2005-02-18
Publication date: 2006-08-23
Anticipated expiration: 2025-02-18
Also published as: GB2423333B; GB0503386D0; CN101180442A; CN101180442B

Abstract

A latch assembly having a chassis 12 a latch bolt 14, moveably mounted on the chassis and having a closed position for retaining a striker and an open position for releasing the striker, a pawl 16 having an engaged position for holding the latch bolt in the closed position and a disengaged position allowing the latch bolt to move to the open position, a crank shaft 50 being rotatably mounted on the chassis about a crank shaft axis Y and having a crank pin 54 in which the pawl 16 is rotatably mounted on the crank pin 54 so as to be rotatable about a pawl axis, the chassis including a chassis control surface 29A engageable by a pawl control surface 42 of the pawl in which during movement of the pawl from the engaged position to the disengaged position the crank shaft rotates in an opening direction such that pawl axis is constrained to move along an arc centred on the crank shaft axis and the angular position of the pawl is control by engagement between the chassis controlled surface and the pawl control surface.

Description

Latch Assembly The present invention relates to latch assemblies, in

particular latch assemblies for use with car doors and car boots.

Latch assemblies are known to releasably secure car doors in a closed position. Operation of an inside door handle or an outside door handle will release the latch allowing the door to open. Subsequent closure of the door will automatically relatch the latch.

In order to ensure that rain does not enter the vehicle, the doors are provided with weather seals around their peripheral edge which close against an aperture in the vehicle body in which the door sits. In addition to providing protection from rain, the weather seals also reduce the wind noise. The ongoing requirement for improved vehicle occupant comfort requires minimising of wind noise which in turn requires the weather seals to be clamped tighter by the door. The door clamps the seals by virtue of the door latch and accordingly there is a tendency for the seal load exerted on the latch to be increased in order to meet the increased occupancy comfort levels required. Because the seal forced on the latch is increased, then the forces required to release the latch are correspondingly increased.

US3386761 shows a vehicle door mounted latch having a rotatable claw which releasably retains a vehicle body mounted striker to hold the door in a closed position. The claw is held in the closed position by a first pawl. The first paw! is held in the closed position by a second paw!. The second paw! can be moved to a release position by an electric actuator which in turn frees the first pawl which allows the claw to rotate to the open position.

The system is arranged such that once the second pawl has disengaged the first pawl, the first pawl is driven to a release position by the seal!oad acting on the claw.

US2004/0227358 shows a rotatable claw is held in the closed position by a rotatable lever and a link. The rotatable lever can in turn be held in position by a pawl. Disengaging the pawl from the lever allows the lever, link and pawl to move to an open position. One end of the link remains in permanent engagement with the claw. The system is arranged such that once the paw! has disengaged from the!ever, the lever and link are driven to the open position by the seal load acting on the claw.

EP0978609 shows a rotatable claw that can be held in a closed position by a pawl. The pawl is mounted on a cam and during an initial part of opening of the latch, the cam rotates relative to the pawl thereby initially slightly increasing and then significantly reducing the seal load. During the final part of opening of the latch the cam and pawl rotate in unison thereby disengaging the pawl tooth from the claw tooth. However, the arrangement is such that the cam must be driven by a motor to release the latch. In particular, in the closed position the particular configuration of cam axis, paw! pivot axis and paw! tooth is such that latch will remain shut. In other words, the paw! is an over- centre position, such that the cam is driven in a closing direction when the latch is closed.

Thus EP0978609 shows a latch in which the component in direct contact with the claw (the paw!) is in a stable position whereas US3386761 and US2004/0227358 both show latches wherein the component in direct contact with the claw is in an unstable position, and therefore requires a further component (the second pawl in US3386761, and the paw! in US200410227358) to hold the component that directly engages the claw in its unstable position.

An object of the present invention is to provide a compact latch arrangement. Another object of the present invention is to provide a latch arrangement that requires reduced force to release.

Thus, according to the present invention there is provided a latch arrangement as defined in the accompanying independent claims.

The invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figures 1 to lB shows a view taken from the backp!ate side of the latch of certain components of a latch arrangement according to the present invention in a closed position, Figure 1C show a view taken from the retention plate side of the latch of certain components of the latch arrangement of Figure 1 in a closed position, Figure 2 and 2A show certain components of figure 1 whilst the latch is being opened, Figure 3 to 3B show certain components of the latch of figure 1 in an open position, Figure 4 shows certain components of the latch of figure 1 during closing, and Figures 5 to 9 show a second embodiment of the present invention.

With reference to the figures there is shown a latch assembly 10, the major components of which are a latch chassis 12, a latch bolt in the form of a rotating claw 14, a pawl 16, a crank shaft assembly 18 and a release actuator assembly 20. Latch assembly 10 is mounted on a door 8 (only shown in figure 1).

The major components of the latch chassis 12 are a retention plate 22 and a back plate 24.

Retention plate 22 is generally planar and includes a mouth 26 for receiving a striker (not shown). The retention plate 22 includes three threaded holes 27 which in use are used to secure the latch assembly to the door. Projecting from the retention plate is a claw pivot pin 28, and stop pins 29 and 30. Stop pin 29 includes a cylindrical outer surface 29A, the purpose of which will be described below.

Backplate 24 includes holes 31A, 31B and 31C for receiving ends of claw pivot pin 28, stop pin 29 and stop pin 30 respectively. During assembly the ends of pins 28, 29 and 30 are peened over in order to secure the backplate 24 relative to the retention plate 22.

Rotating claw 14 is pivotally mounted on claw pivot pin 28 and includes a mouth 32 for receiving the striker, a first safety abutment 33 and a closed abutment 34. A spring abutment 35 is engaged by spring 36 to bias the rotating claw towards its open position.

The rotating claw is generally planar and includes a reset pin 37 which projects out of general plane of the rotating claw.

The pawl 16 includes a pawl tooth 40, a first arm 41 having an abutment surface 42, a second arm 43, a third arm 44 having an abutment surface 45. Pawl 16 also has a pivot hole 46 of internal diameter D. Pawl 16 is biased in a clockwise direction when viewing figure 1 C by spring 47 engaging second arm 43. Stop pin 30 acts to limit rotation of the paw! in an anticlockwise direction when viewing figure 3 by engaging third arm 44.

The major components of crank shaft assembly 18 are a crank shaft 50, a reset lever 51 and release lever 52.

Crank shaft 50 includes a crank pin 54 in the form of disc having a crank pin axis Y. A square shaft 55 projects from one side of crank pin 54 and a cylindrical pin 56 projects from the other side of crank pin 54. Square shaft 55 and cylindrical pin 56 together define crank shaft axis A. Cylindrical pin 56 is rotatably mounted in a hole (not shown) of retention plate 22. The retention plate thereby provides a bearing for pin 56.

The diameter of crank pin 54 is a running fit in paw! pivot hole 46, i.e. the diameter of crank pin 54 is slightly less than D. The radius of crank pin 54 is R. The thickness of crank pin 54 is substantially the same as the thickness of paw! 16.

Reset lever 51 includes an arm 60 and a boss 61 secured to arm 60. Boss 61 has a cylindrical outer surface 62 and has a central hole of square cross section. Accordingly, when the boss 61 is assembled onto square shaft 55, as shown in figure 3, then arm 60 becomes rotationally fast with crank shaft 50. Cylindrical outer surface 62 of boss 61 is mounted in a hole in the backplate, which thereby provides a bearing surface for outer surface 62. It will be appreciated that cylindrical outer surface 62 and the outer surface of cylindrical pin 56 are concentric and together define the crank shaft axis A. Arm 60 includes an edge 60A (also known as a reset abutment) which interacts with reset pin 37 as will be described further below.

Release lever 52 is generally elongate and includes a square hole 64 at one end to receive an end of square shaft 55, and includes a release abutment 65 at the other end thereof.

A bolt and washer (not shown) is screwed into threaded hole 57 of square shaft 55 to secure the crank shaft, reset lever and release lever together. Accordingly, it will be appreciated that the crank shaft, reset lever and release lever are all rotationally fast relative to each other.

When assembled, the crank pin 54 and the reset lever 51 are positioned between the retention plate and backplate with the cylindrical outer surface 62 of boss 61 being rotationally mounted in a hole (not shown) of the backplate 24. It will be appreciated that the release lever 52 lies on an opposite side of backplate 24 to the reset lever 51 and crank pin 54 (best seen in figure 3A).

The major components of release actuator assembly 20 are bracket 70, electromagnet 71 and release plate 72. Bracket 70 is bent from retention plate 22 and is used to mount electromagnet 71. The bracket is also used to pivotally mount release plate 72 which is made from a magnetic material, such as steel. Release plate 72 is planar and generally rectangular in plan view and it can be seen from figure 2A that it projects equally either side of where it pivots on bracket 70. Thus, release plate 72 is balanced.

Release plate 72 is biased in an anticlockwise direction when viewing figure lB by spring 73 (shown schematically). Release plate 72 includes an abutment 74 at one end.

Operation of the latch assembly 10 is as follows:- Consideration of figures 1 to IC show the latch assembly 10 and associated door 8 in a closed condition. The claw is in a closed position, retaining the striker (not shown). The pawl is in an engaged position whereby pawl tooth 40 is engaged with the closed abutment 34, thereby holding the claw in its closed position. The weather seals of the door are in a compressed state and the striker therefore generates a seal force FS on the mouth 32 of claw 14, which tends to rotate the claw in a clockwise direction when viewing figure 1 (an anticlockwise direction when viewing figure IC).

Force FS in turn generates a force FP onto the pawl tooth 40 and hence onto the pawl 16.

Note in particular that the direction of force FP does not pass through the crank shaft axis A, rather it passes to the right hand side of axis A and above axis A when viewing figure IC. This generates a relatively small anticlockwise torque (when viewing figure IC) on crank shaft assembly 18 about crank shaft axis A. However, the crank shaft assembly 18 is prevented from rotating anticlockwise when viewing figure 1C (clockwise when viewing figure 1B) by virtue of the engagement between release abutment 65 of release lever 52 and abutment 74 of release plate 72. Release plate 72 has been biased to the position shown in figure lB by spring 73. Note that in the closed position no electric current is flowing through electromagnet 71 which accordingly exerts no magnetic force of the release plate 72.

In order to release the latch, electric current is supplied to electromagnet 71 which creates a magnetic force which attracts the right hand end (when viewing figure IB) of release plate 72, causing the release plate to rotate clockwise to the position shown in figure 2A. This in turn allows the release lever 52 and crank shaft 50 to rotate clockwise (when viewing figures 2 and 2A) in an opening direction.

Considering figure 1 C, the crank shaft rotation upon opening is anticlockwise about axis A. It will be appreciated that crank shaft axis A is defined by cylindrical pin 56 being rotatably mounted in the retention plate (as mentioned above) and boss 61 being rotatably mounted in the backplate (as mentioned above). Accordingly, crank shaft axis A is fixed relative to the latch chassis 12.

As mentioned above, when viewing figure 1C, force FP generates a small anticlockwise torque upon the crank shaft 50 about the crank shaft axis A. Once the crank shaft is freed to rotate (i.e. once abutment 74 has disengaged from release abutment 65) then the crank shaft will move in an anticlockwise direction since crank pin axis Y is constrained to move about an arc centred on crank shaft axis A. It will be appreciated that since pawl pivot hole 46 is a close running fit on crank pin 54, then the pawl axis Z (i.e. the centre of pawl pivot hole 46) is coincident with the crank pin axis Y. Accordingly, the pawl axis Z is similarly constrained to move about an arc centred on crank shaft axis A. As the crank shaft 50 starts to rotate in an anticlockwise direction from the position shown in figure Ic, it will be appreciated that the claw 14 starts to open. it will also be appreciated that it is the action of the claw pushing on the pawl that causes the pawl to move. As the pawl moves, the angular position of the pawl is controlled by engagement between abutment surface 42 of arm 41 and stop pin 29, more particularly contact point B defined between abutment surface 42 and part of the cylindrical outer surface 29A.

Note that generally speaking the movement of the paw! can be approximated to rotation about point B (i.e. rotation about the contact point between abutment surface 42 and cylindrical outer surface 29A). However, the movement is not truly rotational since a part of the pawl (namely the pawl axis Z) is constrained to move about axis A rather than about point B. Thus, the movement of the pawl at contact point B relative to stop pin 29 is a combination of rotational movement and transitional (sliding) movement. Indeed contact point B is not stationary and will move a relatively small distance around the cylindrical outer surface 29A, and will also move a relatively small distance along abutment surface 42. Thus, contact point B is position where (at the relevant time during opening of the latch) abutment surface 42 contacts the cylindrical outer surface 29A.

It will be appreciated that, starting from the figure ic position, once abutment 74 has disengaged from release abutment 65, the closed abutment 34 of the claw pushes the pawl (via the paw! tooth) to a position whereby the closed abutment 34 can pass under the pawl tooth 40 when viewing figure C (see in particular figure 6 in relation to the second embodiment of the invention), continued anticlockwise rotation of claw 14 will cause the first safety abutment 33 to approach the pawl tooth 40. As this occurs, pawl tooth 40 will momentarily engage the first safety abutment 33, since pawl 16 is biased in a clockwise direction when viewing figure iC by spring 47. However, the geometry of the system is such that immediately after momentary engagement between first safety abutment 33 and pawl tooth 40, the first safety abutment pushes the pawl (via pawl tooth 40) to a position whereby the first safety abutment 33 continuous to rotate in an anticlockwise direction when viewing figure iC under the pawl tooth 40.

Once the paw! tooth 40 has thus disengaged from first safety abutment 34 of the claw, the claw is then free to rotate past the position shown in figure 2 to the fully open position as shown in figure 3. However, in doing so the reset pin 37 engages and then moves edge 60A of reset lever 60. This in turn rotates the crank shaft back to the position shown in figure 1, thereby resetting the crank pin axis Y to the figure 1 position, and also returning the release lever 52 to the figure 1 position. As the reset lever 52 passes over the right hand end of release plate 72, the release plate is momentarily deflected and then snapped back into engagement (under the influence of spring 73) such that abutment 74 re-engages release abutment 65. Thus, when considering figures 3 and 3A, the paw! 16 crank shaft assembly 1 8, and release actuator assembly 20, are all in the same position as figures 1 to I B. However, in figures 3 and 3A the claw is in the open position, whereas in figures 1 to 113 the claw is in the closed position. Also, in figure 3 and 3A the rotational position of the pawl is controlled by engagement between third arm 44 and stop pin 30, whereas in figures I to lB the rotational position of the pawl is determined by engagement between the pawl tooth 40 and closed abutment 34.

Once the latch and associated door has been opened, then closing of the door will automatically relatch the latch. Note however that no rotation of the crank shaft occurs during closing of the door. Accordingly, the crank pin axis does not rotate and as such the crank pin itself acts as a simple pivot having a fixed axis. Figure 4 shows the latch assembly 10 during the closing process and it can be seen that the paw! is free to rotate about paw! axis Z to provide conventional closing dynamics for the first safety and fully latched positions.

As mentioned above, the crank shaft assembly 18 is supported in a bearing of the retention plate on one side of crank pin 54 and is also supported in a bearing in the backplate on the other side of crank pin 54. Thus, the crank shaft is supported on both sides of the crank pin which is a particularly compact and strong arrangement. However, in further embodiments, the crank shaft need only be supported on one side, i.e. the crank shaft can be an overhung crank shaft. An example of such an overhung crank shaft would be provided by deleting cylindrical pin 56. Note that the crank shaft axis would still be in exactly the same position since it would be defined by cylindrical outer surface 62.

Consideration of figure 1 C shows that the crank pin has radius R and the cylindrical pin 56 has radius r. The crank throw (the distance between the crank shaft axis A and the crank pin axis Y) is (R - r). Accordingly, no part of cylindrical pin 56 sits outside the circumference of disc 54. This provides a particularly compact arrangement. It will be appreciated that the crank pin axis is offset from the crank shaft axis by the crank pin radius minus the crank shaft radius.

Consideration of figure 3 shows that cylindrical outer surface 62 of boss 61 is larger in diameter than cylindrical pin 56. Thus, in this case, a crescent shaped portion of boss 61 sits outside the diameter of crank pin 54. Whilst this is a less compact arrangement than cylindrical pin 56, nevertheless the crank pin axis is offset from the crank shaft axis by less than the radius of the crank pin. In further embodiments, the crank pin axis can be offset from the crank shaft axis by more than the radius of the crank pin.

Figures 5 to 9 show a second embodiment of a latch assembly 110 in which components that fulfil substantially the same function as shown in latch assembly 10 are labelled 100 greater. Figures 5, 5A and 5B show the latch assembly 110 in a closed position.

Figures 6 and 6A show the latch assembly during opening. In particular, figure 6 shows the closed abutment 134 just passing underneath the pawl tooth 140. It can be seen from figure 6 that the claw 114 has rotated clockwise slightly (i.e. it has started to open) when compared with the fully closed position shown in figure 5B.

Figure 6A best shows the generally rectangular plan view of release plate 172. Release plate 172 further includes pivot lugs 176 which are received in respective holes 177 of side plates I 78 to allow the release plate 172 to pivot thereby allowing abutment 174 to disengage subsequently engage release abutment 165.

Release plate 72 is mounted in a similar manner to release plate 172.

Figure 7 shows the latch assembly 110 in an open condition.

Figure 8 shows the latch assembly 110 closed to a first safety position, i.e. a position where the door is not fully closed but nevertheless is prevented from being opened. Accordingly, pawl tooth 140 has engaged first safety abutment 133. Note that as shown in figure 8 the paw! 116 and the crank shaft assembly 118 are in an identical position to that shown in figure 5B.

As best seen in figure 6A, the release actuator assembly 120 and release lever 152 lies on one side of backplate 124, whilst the crank pin 154, paw! 116 and claw 114 lie on the other side of the backplate 124. Because mouth 126 must receive and release the striker, then the claw and pawl must inevitably be in an environment that is exposed to dirt and moisture.

However, figure 9 shows a housing 190 made of a plastics material which closes off the various cut outs in backplate 124 and provides an appropriate housing enclosure 191 for release actuator assembly 120 and release lever 152 thereby providing a dry and dirt free environment. In particular, the bearing of the backplate which supports boss 161 would prevent dirt and moisture entering the housing enclosure. A cover (not shown) encloses the open side of the housing enclosure 191 and is secured to the housing via screws screwed into holes 192. A seal (not shown) sits in groove 193 to provide a waterproof seal between housing 190 and the cover.

Latch assembly 10 and 110 are released by a control system allowing current to flow through the electromagnet 71 or 171 which thereby attracts release plate 72 or 172 as appropriate. However, in further embodiments the release plate could be actuated manually, for example by provision of a suitable connection to an inside door handle or an outside door handle. Alternatively, the release plate could be actuated by an alternative power actuator, such as a motor.

Claims

Claims 1. A latch assembly having a chassis a latch bolt, moveably mounted

on the chassis and having a closed position for retaining a striker and an open position for releasing the striker, a paw! having an engaged position for holding the latch bolt in the closed position and a disengaged position allowing the latch bolt to move to the open position, a crank shaft being rotatably mounted on the chassis about a crank shaft axis and having a crank pin in which the paw! is rotatably mounted on the crank pin so as to be rotatable about a paw! axis, the chassis including a chassis control surface engageable by a paw! control surface of the paw! in which during movement of the pawl from the engaged position to the disengaged position the crank shaft rotates in an opening direction such that pawl axis is constrained to move a!ong an arc centred on the crank shaft axis and the angular position of the paw! is control by engagement between the chassis controlled surface and the paw! control surface.
2. A latch assembly as defined in claim 1 in which the pawl generally rotates about the chassis control surface during movement of the paw! from the engaged position to the disengaged position.
3. A latch assembly as defined in claim I or 2 in which movement of the latch bolt from the closed position towards the open position drives the paw! to the disengaged position.
4. A latch assembly as defined in any preceding claim in which the latch has a closed condition where:- the claw is in the closed position, the pawl is in the engaged position, and the pawl axis is in a first position, and the latch has an open condition wherein:- the claw is in the open position the paw! is in the disengaged position and the paw! axis is in said first position.
5. A latch assembly as defined in claim 4 in which during movement of the pawl from the engaged position to the disengaged position the crank shaft rotates in an opening direction such that the paw! axis moves to a second position and the latch bolt rotates the crank shaft in a second direction such that the pawl axis is returned to the first position.
6. A latch assembly as defined in claim 5 in which the latch bolt engages a reset abutment of the crank shaft.
7. A latch assembly as defined in claim 6 in which the reset abutment is defined on a reset lever of the crank shaft.
8. A latch assembly defined in any one of claims 4 to 7 in which with the latch in the closed condition a release abutment of the crank shaft engages a moveable abutment to prevent the crank shaft moving in the opening direction.
9. A latch assembly as defined in claim 8 in which release abutment is defined on a release lever of the crank shaft.
10. A latch assembly as defined in claim 8 or 9 in which the moveable abutment is

pivotable.
11. A latch assembly having a chassis a latch bolt, moveably mounted on the chassis and having a closed position for retaining a striker and an open position for releasing the striker, a pawl having an engaged position for holding the latch bolt in the closed position and a disengaged position allowing the latch bolt to move to the open position, a crank shaft being rotatably mounted on the chassis about a crank shaft axis and having a crank pin in which the pawl is rotatably mounted on the crank pin so as to be rotatable about a pawl axis, in which movement of the pawl from the engaged position to the disengaged position rotates the crank shaft in an opening direction and with the pawl in the engaged position a force applied to the pawl by the latch bolt creates a turning moment on the crank shaft in the opening direction of the crank shaft and the crank shaft is prevented from rotating in the opening direction by a moveable abutment.
12. A latch assembly as defined in any one of claims 8 to 11 in which the moveable abutment is actuatable by a release actuator, such as an electromagnet.
13. A latch assembly as defined in any one of claims 8 to 12 in which the moveable abutment is manually actuable.
14. A latch assembly as defined in any preceding claim in which the crank shaft is supporting in a bearing on a first side of the crank pin and is supported in a bearing on a second side of the crank pin.
15. A latch assembly as defined in any preceding claim in which the crank pin axis is offset from the crank shaft axis by less than a radius of the crank pin.
16. A latch assembly as defined in any preceding claim in which the crank shaft has a crank shaft radius and the crank pin axis is offset from the crank shaft axis by less than the crank pin radius minus the crank shaft radius.