nht74-5.47 | NHTSA

DATE: 04/22/74

FROM: AUTHOR UNAVAILABLE; James B. Gregory; NHTSA

TO: American Safety Equipment Corporation

TITLE: FMVSS INTERPRETATION

TEXT: This is in reply to your letter of August 3, 1973, petitioning for amendments to paragraphs S4.9 and S5.3.1 of Motor Vehicle Safety Standard No. 213 which would allow the use of a buckle release mechanism design that requires, before release, some foreshortening of the belt system to reduce the load on the release mechanism. This design cannot meet the existing requirements of S4.9 of Standard No. 213 with the device under load. We wrote to you on August 20, 1973, and on December 17, 1973, requesting additional data. We have not received a response from you to either letter.

We have decided that your petition should be denied. Our objection to the design you wish to employ is that it cannot be released when the belt restraint system is under load. The NHTSA believes, and has adopted its position in Standard No. 213, that a fundamental safety requirement for any occupant restraint release mechanism is the ability to release when it is under a load imposed by the weight of the occupant. In many vehicle crashes restraint systems may be loaded in this fashion when occupants must be removed.

We do not disagree with your argument that mechanisms which release under load may more readily be released by children when release is undesirable. We believe the greater safety problem, however, is presented by designs which are difficult to operate because they require a prior unloading of the release mechanism. These systems may not be able to be released, even by adults, in crash situations. Data we have received indicates substantial difficulty in the ability of adults to release a child from a child seat in situations (total darkness) simulating emergencies. The study in question has been conducted by the National Swedish Road and Traffic Research Institute and is on file in Docket No. 2-15.

Moreover, we believe buckle release mechanisms should be operable by older child occupants, particularly in situations such as in upside-down configurations where a load is imposed on the mechanism. This purpose is met by the existing requirements of the standard but would not be met were we to grant your petition.

In your petition you argue that even a lower release force does not necessarily mean that the occupant will be able to escape easily from the restraint system. While this may be true, as no requirements are specified in Standard No. 213 regarding ease of belt removal, it is not a justification for increasing the difficulty of operating the buckle release mechanism.

SINCERELY

August 3, 1973

Administrator National Highway Traffic Safety Administration Subject: Petition for Rule Making

Reference: MVSS213, S4.9 and S5.3.1

American Safety Equipment Corporation is a major developer and manufacturer of safety belt restraint systems for automobile manufacturers. American Safety personnel have a great deal of experience designing aircraft and automotive restraint systems, particularly hardware such as buckles, retractors and associated items. The Company has been active since 1966 in the business of designing and producing restraint harnesses and complete seating systems for children in the 20 to 40 pound size range. The Company has been working on development of a new child safety seat since 1970 basing the basic design criteria on dynamic performance under simulated crash testing, while also observing the current static testing regulation. Final testing of prototype models has been completed on the design considered optimum for performance, economy and simplicity of use.

This petition is submitted in accordance with the procedure described in Subpart B Section 553.31. This proposal is to add a performance requirement and test procedure for an occupant harness release mechanism not currently considered by the Child Seating Systems regulation. The mechanism is not of a nature normally classified or described as a "buckle", but for purposes of MVSS213, is being considered a release mechanism.

The proposed additions and revisions to MVSS213 are shown underlined:

S4.9 (b) Release when a force of not more than 20 pounds is applied when tested in accordance with S5.3 expect for systems described by S4.9 (c).

2 (c) Release when a force of not more than 10 pounds is applied when the release mechanism requires foreshortening of the webbing restraint components to activate and is tested in accordance with S5.3.1 (d).

S5.3.1 For forward-facing child seating systems where foreshortening of the webbing restraint components is not required by the release mechanism -

(a) -- unchanged --

(b) -- unchanged --

When foreshortening of the webbing restraint components is required to actuate the release mechanism -

(d) Test the system with a 1,000-pound force as specified in S5.1, remove the force completely and then release the mechanism in a manner typical of that employed in actual use.

Photographs are enclosed showing the release mechanism actuation under normal and simulated emergency conditions and a typical testing set-up to determine release force. The application of force to release the occupant harness must simultaneously pull down on the abdominal pad and the shoulder straps thereto attached and upwards under the metal latch. This is very simply described as a "pinching" action of the thumb and first and/or second finger. The shoulder straps are thereby foreshortened and the occupant will be forced rearward (unless lifted or pushed) toward the back surface of the child seat. The hand not activating the release mechanism can be used to move the child's torso away from contact with the restraint straps. The actuation of the release mechanism with the belts in a slackened condition is an easy one-hand operation with a low force requirement.

The performance criteria on which our restraint release mechanism design is based are as follows:

1. The mechanism must be capable of restraining the occupant when the system undergoes dynamic forces of an auto crash without distortion of any kind which could result in a jammed or difficult-to-release condition.

2. Child must not be able to easily release himself.

3. The mechanism must be extremely easy to understand from the standpoint of an adult learning how to actuate. Similarity to current production adult safety belt hardware assures the shortest possible learning time by an adult.

3 These criteria were formulated after studying field experience of consumers and consulting with experienced people in various phases of the child and adult restraint business. This experience indicated to us that -

1. A common possible problem with many child seat harness buckle release mechanisms is that the release mechanisms could be easily actuated by the child occupant. The child is protected only while sitting in the seat with the harness secured.

2. Emergency removal of a child occupant from a wrecked automobile should be accomplished within a minimum time. Emergency removal always involves supporting at least a portion of the child's weight while releasing the harness mechanism. After an accident the child's weight is forced against the restraining straps if the car has overturned or if the car seat back is exerting pressure on the child and/or child's seating system.

3. Restraint harness buckles which have a low release force (even under occupant's weight load) may not completely detach all components of the harness system from the occupant. Such components as shoulder and/or lap belts may remain wholly or partially attached to the buckle and could interfere with the removal of the occupant from the seating system.

Much subjective information from consumers was also evaluated by us to finalize the release mechanism design since it is considered one of the key components of the overall child seating system. Real-world data is scarce on crash performance of child restraint systems, but accident experience is reasonably hypothesized from experience with children and emergency post-crash situations. It is considered reasonable by us that release mechanisms which actuate under the test procedures now in effect are likely to be released wholly or partially be a child prior to a crash. Protection in low speed, as well as high speed crashes, is important and a securely fastened harness is mandatory for protection. Driver distraction by unrestrained children can also cause accidents which is minimized by a release mechanism not easily operable by the child. Supporting the child's weight or otherwise relieving pressure of the child's body from the harness webbing during emergency removal is consistent with a majority of conceivable accident conditions and always would be a requirement with the impact-shield type restraints (no harness) where the occupant would be expected to be wrapped around the impact shield after a crash. Self-removal from a harness restraint under emergency conditions by a child in the 20 to 40 pound age group

4 is not reasonable unless the child is taught expressly for this purpose. In such a case, training in body articulation and hardware manipulation is probably difficult for the proposed release mechanism.

American Safety is planning procurement of the necessary tooling for manufacturing the child seat design incorporating the proposed release mechanism. The proposed child restraint release mechanism and release procedure is nearly identical to the release of the detachable shoulder harness pin-connector in production for adult restraints in certain cars for three years. The pin and plastic grommet used on the child restraint mechanism proposed are parts produced for several different 1973 model cars. The Company requests the addition of the proposed requirements to MVSS213 to permit it to manufacture and sell the child restraint product.

Gordon M. Bradford Vice President, Corporate Development

enclosures

(Graphics omitted)

PHOTOGRAPH NO. 1

Restraint release mechanism -- This general view shows the similarity to the established pin and connector design now in production for shoulder belts on adult restraints. The two straps above the release mechanism are adjustable upper torso restraints. The release mechanism is affixed to the abdominal pad and the adjustable crotch strap is sewn permanently to the release mechanism connector.

PHOTOGRAPH NO. 2

Release mechanism activation -- The initial step in activating the release is as shown. The thumb depresses the abdominal pad and foreshortens the upper torso restraints. The index finger or middle finger holds up the connector while the pin is forced downward.

PHOTOGRAPH NO. 3

Release mechanism activation -- The completion of the releasing operation shows the pin and grommet now moved downward into the enlarged opening of the connector where it is completely separated from the crotch strap and connector. A slight forward pull with the finger finishes the release. The connector is then dropped and the abdominal pad with upper torso straps attached is swung upward over the occupant's head for removal when the seat is situated in a normal horizontal attitude.

PHOTOGRAPH NO. 4

Release force requirements -- A possible form of measurement device which operates the release mechanism in a manner typical of that employed in actual use is shown. This test would be performed after the child seating system had been subjected to a static load of 1,000 lbs in accordance with MVSS213, S5.1. Following this the release force test would be done in accordance with the proposed procedure S5.3.1(d).

PHOTOGRAPH NO. 5

The position illustrated simulates a nose-down car attitude. The child's full weight is resting on the harness. The adult is about to release the harness.

PHOTOGRAPH NO. 6

The adult has pushed upward with her left hand on the abdominal pad. This slackens the crotch strap allowing normal operation of the buckle with her right hand. The load required to release the buckle in this way is no greater than normal.

PHOTOGRAPH NO. 7

The buckle has opened and the adult has begun to lower the child. The abdominal pad has slid naturally from her left to her right hand. Her left hand continues to support the abdomen.

PHOTOGRAPH NO. 8

The adult's right hand continues to guide the abdominal pad while the left hand continues to support the abdomen. The crotch strap is completely clear of the child.

PHOTOGRAPH NO. 9

The child is out of the harness and is now on what would be either the car's dash or front seat back, depending on where the child seat was installed in the vehicle. The harness is clear of the child. No force greater than the child's weight was exerted. There were no "practice" runs after instructions on how to correctly release the child were given to the Mother.

Interpretation ID: nht74-5.47