Chairs and seats – Movable back – Tiltable
Reexamination Certificate
1999-12-23
2002-08-20
Nelson, Jr., Milton (Department: 3624)
Chairs and seats
Movable back
Tiltable
Reexamination Certificate
active
06435616
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a latching device, particularly to a latching device for vehicle seats, and more particularly to a latching device for vehicle seats foldable and lockable in either of a seat forming or a cargo carrying position.
2. Background and Material Information
In an automobile, such as a two door coupe and the like, it is desirable to include a seat having a backrest which is capable of folding between an upright seating position and a forwardly folded position permitting ingress and egress to and from a rear seat of the automobile. For safety considerations, it is also desirable, as well as mandated by federal regulations, that the backrest be lockable in the upright position.
In other vehicles, such as a station wagons, pick up trucks, and sport utility vehicles, it is desirable to include a seat which is capable of folding between a locked upright seating position and a forwardly folded position. In the forwardly folded position, the back of the seat is often used as a load carrying surface such that, once the seat is folded forwardly, the back of the seat can be used as an extension of the vehicle floor to carry loads other than passengers, such as cargo.
In order to accomplish such a function, it is necessary to provide a latching device for the seat back which can lock the backrest in the upright position for carrying passengers, and it is also desirable to lock the backrest in the cargo carrying position in order to maintain a stable surface for the cargo placed thereon during transportation.
Furthermore, in recent years such latching mechanisms for seat backs have been required by federal regulation to pass a crash test, i.e., the Federal Motor Vehicle Safety Standards Test Requirements (FMVSS Test Requirements). These FMVSS Test Requirements relate to conditions that a seatback latch would be subjected to in a vehicle crash situation. The loads on the seatback latching mechanism are much greater during a crash situation than the low loads that are present during normal operation of the seatback latching mechanism. In this regard, the test dummies and the seatback mass experience deceleration loads of 20-30 g's during the tests. Accordingly, for seatback latching mechanisms of the type that the present invention is directed to, the dynamic load imparted to the latching mechanism from the seatback mounting arm may be 10,000 kg for a very short period of time. Thus, the latching mechanism must be designed to carry 100 times the normal load during the FMVSS testing without structural failure of the latching mechanism or disengagement of the latching mechanism during the crash test.
In a known device of this type, a backrest mounting arm is pivotally mounted to a mounting bracket to which a latching lever is pivotally mounted. The backrest mounting arm includes a pair of notches at a lower end thereof at positions defining the upright position of the backrest and the forwardly folded position, and the latching/release lever includes a latching portion to engage in a respective one of the notches to retain the backrest mounting arm in either one of the upright or forwardly folded positions. Furthermore, the latching/release lever includes pivoting feature for moving the latching portion out of the notch to permit pivotal movement of the backrest mounting arm. However, in such a device, during the crash tests, it has been observed that the entire load for resisting movement of the backrest mounting arm during the FMVSS test is carried by the pivot pin mounting the latching/release lever to the mounting bracket, which often causes shearing of the pivot pin. It has also been observed that the latching portion of the latching lever is sometimes deformed laterally out of engagement with the retaining notch in the lower end of the backrest mounting arm. Either of these situations will result in a failure of the device to pass the crash test. The present inventors has determined that the reason for these failures is that previous latch designs carried the total FMVSS loads through the same latch load path that carries the loads during normal operation. Accordingly, by the present invention, a latch design has been provided that will carry a significant portion of the very high FMVSS loads through a secondary load path, thus enabling the latch design to be significantly improved for normal operation.
Additionally, in pivoting seatbacks of this type, it is also important that, in use, the seatback does not “chuck” (i.e., vibrate back and forth as the automobile is driven) due to play in the latching mechanism. This “chucking” is difficult to prevent because the radius from the seat back pivot to the latching mechanism is small, on the order of about 25-50 mm, and the radius from the seatback pivot to the top of the seatback where the “chucking” is observed is very large, on the order of about 700-1000 mm. Thus, an extremely small clearance in the latching mechanism results in a very large movement in the seatback. Furthermore, wear of the latch components during the life of the automotive vehicle also results in an increase in the amount of “chucking”.
In this regard, it has been observed that excessive “chucking” has been a problem with previous latch designs.
Moreover, another important design consideration is the load required for operation of the latch release lever. Thus, other requirements are that the load necessary for operation of the release lever be low and the length of travel during operation be short. These parameters must also be consistent from vehicle to vehicle for the 100,000 to 500,000 vehicles in which the seatback latches are installed during manufacture each year. It should be noted that during normal operation of the seatback, the only loads that must be overcome to release the latch are (1) any biasing load on the seatback due to gravity, (2) any load resulting from a seatback biasing spring, and (3) any biasing load on the release lever resulting from a return spring. Typically during normal operation, the low loads carried from the seatback mounting arm through the latch pin to the release lever pivot connected to the vehicle body (e.g., by a mounting bracket) are about 100-150 kg. It has been observed that release lever loads for previous latch designs have been too high and vary significantly from vehicle to vehicle.
Additionally, with previous latch designs, the design of the latch had to be compromised for the normal operating functions (release lever effort and chucking) in order to meet the FMVSS Test Requirements. In this regard, previous latch designs included an angled face on the detent portion of the latch. However, if the angled face on the detent portion is too great, the latch will be disengaged during FMVSS testing due to the radial component of the 10,000 kg load that is applied through the backrest mounting arm. Thus, since the latching device of the previous latch designs must be configured in order to ensure that none of the production latches would become disengaged under FMVSS loads during testing, the angled face of the detent portion had to be reduced as low as possible to prevent release during testing.
On the other hand, with previous latch designs, when the angled face on the detent portion is reduced too greatly, release handle operating loads increased significantly and large variations in operations from latch to latch in high volume production may occur due to tolerance variations in components and during assembly. Furthermore, the amount of tolerance variation that can be taken up and/or the amount of wear during durability testing that can be taken up is greatly reduced. Thus, the result of such reduction of the angle face is that to (1) release handle loads increase significantly and are more inconsistent, and to (2) minimize “chucking”, the tolerances of the latch components must be reduced significantly, thereby significantly increasing costs and manufacturing difficulty.
Accordingly, the present invention has been provided to overcome the
Takayanagi Hiroshi
Travis William H.
Greenblum & Bernstein P.L.C.
Jr. Milton Nelson
SW Manufacturing, Inc
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