VEHICLE DOOR LATCH

Abstract: A vehicle door latch assembly including a latch operatively co-acting with a striker as the door nears its closed position, a latching pawl (16) self-engaging with the latch to hold it in a latched condition retaining the door, and unlatching means selectively operable to disengage the latching pawl for opening the door; the unlatching means comprising a pawl lifter (20) movable from a position of rest to carry the latching pawl out of engagement with the claw, a manually operable release member (25) operatively linked to a handle of the door for movement to engage and displace the pawl lifter from said position of rest, a power output member (24) movable also to engage and displace the pawl lifter from said position, an input member (30) power actuated between first and second positions, clutch means releasably drive connecting the input member to the output member to cause shifting of the latter as the input member moves to its second position, and an overriding element carrying the clutch means into and out of drive connection: characterised in that the overriding element is resiliently urged to its clutch disconnecting condition and in that the release member includes a formation coacting with the overriding element to displace it to its clutch connecting condition whereby, in use, power actuation of the input member can only take place by shifting of the release member (Fig. 4).

Description: VEHICLE DOOR LATCH This invention relates to latches for vehicle doors, particularly for light passenger and goods vehicles. Powered locking and powered latching of doors is becoming more favoured, both as part of central locking systems, and to enable more effective weathersealing of doors and greater freedom in styling and design. There are also advantages in providing for power actuated unlatching of doors in terms of dispensing with much of the mechanical linkage and components needed for conventional manual inside and outside door handles, and in providing unitary lock and latch modules of standard form which can be speedily installed in doors of a wide range of vehicle models and types without special adaptation. An example of the provision of power closing is described and claimed in our co-pending patent application GB 9710602.5 dated 23rd May 1997, and the present invention may conveniently be combined with that construction if desired. Examples of the provision of power actuated unlatching are described and claimed in our co-pending patent applications GB 9713407.6 dated 26 June 1997 and GB 9815374.5 dated 15 July 1998. The object of the invention is to provide improvements in vehicle door latches having a power unlatching facility in an economical, effective and reliable form, and providing enhanced safety in their use and operation. According to the invention there is provided a vehicle door latch assembly as defined by Claim 1 of the appended claims. An example of the invention is now more particularly described with reference to the accompanying drawings in which: Fig. 1 is a diagram of parts of a vehicle door latch assembly in a rest position with some parts not relevant to the invention removed for clarity, Fig. 2 is a like diagram showing the parts during a power unlatching operation, Fig. 3 is a like diagram with the parts in a door released position, and Fig. 4 is a perspective view of said parts of the assembly. Referring firstly to Fig. 1, the latch assembly, which will be operatively secured in a door (not shown) in known manner, includes a conventional rotating latch claw 10 having a mouth 12 for co-acting with a striker (not shown) operatively mounted to the associated door post. Claw 10 is biased by a claw spring (not shown) in an anticlockwise direction. A pawl tooth 16A of a latching pawl 16 self engages with the claw in known manner to retain it, and hence the door, releasably at a first safety position at which the door is near closed, and an inner position shown in figure 1 at which the door is fully shut. The assembly may include powered closing/latching of the door as described in our said co-pending patent application GB 9710602.5. Unlatching means includes a pawl lifter 20 in the form of a lever pivoted co-axially with pawl 16 which engages the latter when angularly displaced from its position of rest shown in figure 1, so causing disengagement of pawl 16 from claw 10 to free the door for opening. Manually operable release means of the assembly is of known construction including a release lever 25, best seen in Fig 4, operatively connected to the inside and outside door handles and pivoted co-axially but independently of pawl lifter 20, overlying the latter as viewed in Figs 1 to 3 in which parts of said lever are broken away for clarity. Motion of lever 25 is only transmitted to operate pawl lifter 20 when a lock link 27 (shown in part in Fig 1 only) is positioned between a drive projection 29 of lifter 20 and a drive projection 31 of lever 25. When lock link 27 is withdrawn lever 25 is disabled from moving pawl lifter so locking the door so far as manual release is concerned. An output member in the form of a power release lever 24, best seen in Figure 4, is fulc mmed on a fixed pivot whose axis is parallel to the claw axis. Its left-hand arm 26 is positioned to engage the lower face of a rightward extension 20B of pawl lifter 20 so that when it is turned clockwise it displaces lifter 20 and so causes disengagement of pawl 16 independently of the manually operable release means. The right hand arm of lever 24 terminates in a drive formation in the form of a shoulder 28. An input member in the form of a crank 30 extending alongside said right hand arm has a drive pin 32 which, is engageable with shoulder 28 so that clockwise angular movement of crank 30 is transmitted to lever 24 (see figures 1 and 2). An electric push-pull actuator motor (not shown) is coupled to crank 30 by a vertical power drive link 34, selectively operable to drive crank 30. Crank 30 is pivoted on the lower end of a swinging overriding element 36, the upper end of which is mounted on a fixed pivot 38 in spaced parallel relationship to the axis of release lever 24. In the angular position shown in Figs. 2, 3 and 4 the pivot axes of crank 30 and lever 24 are substantially coincident, so maintaining the clutch means constituted by shoulder 28 and pin 32 in drive engagement. Release lever 24 is resiliently urged anti-clockwise to its Fig 1 position, and overriding element 36 is also resiliently urged anti-clockwise to the position shown in Fig 1 in which the clutch means is disengaged. Overriding element 36 is the form of a bell-crank lever having a longer arm on which crank 30 is pivoted and a shorter arm at its upper end carrying a follower formation in the form of a camming pin 50. The right hand end edge of release lever 25 is formed to provide a stepped camming face 52 co- acting with pin 50. In the rest position of Fig 1 pin 50 abuts the part of face 52 which is at lesser radius from the axis of lever 25 so that the crank 30 is displaced to the right, positioning pin 32 out of drive engagement with shoulder 28. In this condition powered unlatching cannot occur. This is an important safety feature in that any malfunctioning of the actuator or its power supply and control circuitry, e.g. due to a short circuit or ingress of moisture causing the actuator to run uncommanded will not be transmitted to pawl lifter 20 as even if crank 30 is power shifted element 36 remains unaffected. It will be realised that inadvertent power unlatching, particularly while a vehicle was in motion and possibly at high speed, could be very dangerous. Power unlatching can only be initiated by movement of the release lever 25, i.e. by operation of either door handle. Lever 25 has to be shifted to a predetermined angular extent from the rest position of Fig 1 to put the mechanism in the condition shown in Fig 2. Here pin 50 is engaged with the larger radius part of camming face 52 by anti-clockwise movement of lever 25 so camming overriding element 36 clockwise and drawing link 30 to engage the clutch means (shoulder 28 and pin 32). At the same time a switch (not shown) will operate to power the actuator motor, turning release lever 24 clockwise to operate pawl lifter 20 and unlatch the door by putting the mechanism in the condition shown in Fig 3, this taking place without the user having to further move or operate the door handle. With the handle released and ceasing of power actuation the mechanism will self-restore to the rest condition shown in Fig 1. It will be seen that as this rest condition declutches the power actuator drive the mechanism associated with the latter cannot block or impede subsequent closing and relatching of the door or unlatching by manual operation as referred to above independently of the power unlatching provision. The door can still be opened and closed in the normal way even if power actuation should fail, for example due a flat battery.

Claims: CLAIMS 1. A vehicle door latch assembly including a latch operatively co-acting with a striker as the door nears its closed position, a latching pawl self-engaging with the latch to hold it in a latched condition retaining the door, and unlatching means selectively operable to disengage the latching pawl for opening the door; the unlatching means comprising a pawl lifter movable from a position of rest to carry the latching pawl out of engagement with the claw, a manually operable release member operatively linked to a handle of the door for movement to engage and displace the pawl lifter from said position of rest, a power output member movable also to engage and displace the pawl lifter from said position, an input member power actuated between first and second positions, clutch means releasably drive connecting the input member to the output member to cause shifting of the latter as the input member moves to its second position, and an overriding element carrying the clutch means into and out of drive connection: characterised in that the overriding element is resiliently urged to its clutch disconnecting condition and in that the release member includes a formation coacting with the overriding element to displace it to its clutch connecting condition whereby, in use, power actuation of the input member can only take place by shifting of the release member. 2. An assembly as in Claim 1 characterised in that the latch is a pivotally mounted claw. 3. An assembly as in Claim 1 or 2 characterised in that the output member is a power release lever having a first arm positioned for engagement with the pawl lifter and a second arm provided with a drive formation forming a first element of the clutch means. 4. An assembly as in Claim 1, 2 or 3 characterised in that the input member is a crank element coupled to an electric or other power actuator for angular movement and carrying a drive formation forming a second element of the clutch means, the pivot of the crank element being carried on the overriding element so that shifting of the latter carries said second element into and out of engagement with the first element. 5. An assembly as in any preceding claim characterised in that the release member is a pivoted lever including a camming formation coacting with a follower formation on the overriding element. 6. A vehicle door latch assembly substantially as hereinbefore described with reference to and as shown in the accompanying drawings. 7. A vehicle including a latch assembly as in any preceding claim.

Inventors: KALSI GURBINDER SINGH, KALSI, GURBINDER, SINGH
Applicants: KALSI GURBINDER SINGH, MERITOR LIGHT VEHICLE SYS LTD, KALSI, GURBINDER, SINGH, MERITOR LIGHT VEHICLE SYSTEMS (UK) LTD.
Application year: 1999
Main classification: E05B47
IPC codes: E05B65