Latch assembly

Abstract

A latch assembly includes a chassis, a latch bolt movably mounted on the chassis and having a closed position for retaining a striker and an open position for releasing the striker, and a pawl having an engaged position at which the pawl is engaged with the latch bolt to hold the latch bolt in the closed position and a disengaged position at which the pawl is disengaged from the latch bolt thereby allowing the latch bolt to move to the open position. The pawl is rotatably mounted via a pawl pivot pin about a pawl axis, and the pawl pivot pin includes a first arcuate portion having a first radius about the pawl axis. A cross-sectional area of the pawl pivot pin, taken perpendicular to the pawl axis, is greater than an area of a circle having the first radius.

Description

REFERENCE TO RELATED APPLICATIONS[0001]This application is a United States National Phase Application of PCT Application No. PCT / GB2008 / 000328 filed Jan. 31, 2008, which claims priority to United Kingdom Application No. GB 0703597.5 filed Feb. 23, 2007.BACKGROUND OF THE INVENTION[0002]The present invention relates to latch assemblies, and in particular latch assemblies for use with car doors and car boots.[0003]Latch assemblies are known to releasably secure car doors in a closed position. Operation of an inside door handle or an outside door handle would release the latch, allowing the door to open. Subsequent closure of the door will automatically relatch the latch. Electric actuators are commonly employed in car latches in order to release them. Known latches incorporate a rotatable claw which engages with a striker mounted on an opposing surface (for example, a car door frame) in order to retain the door in a closed position. This rotating claw is often held in position by a paw...

AI Technical Summary

Benefits of technology

[0016]By having a pawl pivot pin cross sectional area substantially greater than the area of the circle having the radius of the first arcuate portion, it is possible to have a first arcuate portion of relatively small radius without compromising the strength of the pawl pivot pin. This lower radius of the first arcuate portion means that the detrimental effect of dust and contaminants is reduced, as the mating area between the pawl pivot pin and the surface against which it rotates is reduced. This also reduces the minimum backdrive angle compared to known latches.

[0019]According to a second aspect of the present invention, there is provided a latch assembly having a chassis, a latch bolt movably mounted on the chassis and having a closed position for retaining a striker and an open position for releasing the striker, and a pawl having an engaged position at which the pawl is engaged with the latch bolt to hold the latch bolt in the closed position and a disengaged position at which the pawl is disengaged from the latch bolt, thereby allowing the latch bolt to move to the open position. The pawl is rotatably mounted via a pawl pivot pin about a pawl axis, and the pawl pivot pin is rotatably mounted in a pawl pin orifice including a pawl pin orifice arcuate portion having a second radius about the pawl axis. A cross-sectional area of the pawl pin orifice, taken perpendicular to the pawl axis, is greater than an area of a circle having the second radius.

[0020]By making the cross sectional area of the pawl pin orifice greater than that of a circle having the radius of the second arcuate portion, it is ensured that less than an entire perimeter of the pawl pivot pin is in contact with the pawl pin orifice. Therefore, the contact area between the pawl pivot pin and the pawl pin orifice is reduced compared to known arrangements, and as such, the effect of dust and contaminants is reduced. Furthermore, the fact that the area of the pawl pin orifice is significantly larger than the area of the pawl pivot pin leaves a gap from which dust and contaminants can escape and be ejected from the mechanism. In this manner, the amount of friction in the latch is reduced, and consequently, the size of the actuators may also be reduced. Furthermore, the likelihood of the latch becoming stuck or jammed because of friction arising from dust or contaminants is also reduced.

Problems solved by technology

A problem with this type of known latch is that a radius of the pawl pivot pin, which as described must be of a certain magnitude to withstand loads, is directly related to the size of the contact area between the pawl and said pawl pivot pin.

This is problematic as the amount of friction between these two components is influenced by the amount of dust and contaminants that may accrue between them.

Therefore, larger and more expensive actuators are required which is undesirable.

This is problematic as dust contamination can cause excessive friction between the first pawl 16 and the crankshaft 50, increasing the effort required to rotate them relative to each other.

This is undesirable as larger actuators are required to rotate the two components relative to each other.

Any attempt to reduce the radius of the crankshaft 50 to distances below the minimum required radius rmin would result in significant weakening of the crankshaft and consequently likely failure of this component.