Clevis Safety Belt Buckle

Known prior art safety belt buckles are disclosed in the following U.S. Pat. Nos.: 3,131,451; 3,237,256; 3,242,546; 3,274,655; 3,277,548; 3,449,800; 3,465,393; 3,483,599; 3,588,969; 3,623,191; 3,639,951; 3,686,720; 3,716,895; 4,015,094; 4,052,775; 4,060,879; 4,064,603. Additional prior art includes a safety belt buckle disclosed in co-pending United States Patent Application Ser. No. 06/161,424 filed on June 20, 1980. A common feature of such prior art buckles is a connector constructed as a flat metal tongue having an aperture slot for engagement by a latch projection spring loaded to an engagement position and having a ramp surface for deflecting the latch upon introduction of the tongue and deflected by a push button for disengagement. The latch projection is commonly provided on a pivoted element anchored in the buckle housing which is under compression from separating stress applied to the buckle and accordingly subject to bending stress limiting the effective strength of the connection under crash loading.

Embodiments of the present invention disclosed herein employ a clevis haivng side apertures extending over the aperture in the connector tongue and a latch projection which extends through the tongue aperture and seats on both sides of the clevis to provide a latch connection subject to close coupled compressive shear stresses which are transmitted through primary tensile stresses in the connector and clevis members to the associated belt connections. Such inherently stronger latch construction has made it possible to achieve the surprising result of a 6,500 pound separating test load without damage in a buckle of substantially the same size and proportions as the standard prior art buckle having a capacity of only a fraction of such test load.

In a first embodiment suitable for a semi-permanent buckle connection, as in a passive system wherein the buckle is manually opened only under emergency conditions, the initial connection as well as disconnection is made with a manual push button depressed. In a second embodiment provision is made for deflecting the latch to accommodate insertion of the connector tongue without need for depressing the push button thereby providing an insertion feature completely equivalent to conventional prior art buckles which facilitate buckle connection made through mere insertion of the connector tongue.

FIG. 1 is a plan view of the first embodiment of the invention;

FIG. 2 is a side elevation of the first embodiment;

FIG. 3 is a sectional view taken along the line 3--3 of FIG. 1 showing the buckle latched;

FIG. 4 is a sectional view taken along the line 4--4 of FIG. 1 showing the buckle with the push button depressed;

FIG. 5 is a plan view of the latch hinge employed in the buckle illustrated as the first embodiment;

FIG. 6 is a side elevation of the latch hinge;

FIG. 7 is a plan view of a somewhat modified version of the first embodiment;

FIG. 8 is a sectional side elevation taken along the line 8--8 of FIG. 7;

FIG. 9 is a fragmentary sectional view taken along the line 9--9 of FIG. 7 illustrating the latch button in depressed condition;

FIG. 10 is a plan view of a second embodiment of the present invention;

FIG. 11 is a side elevation of the second embodiment;

FIG. 12 is an enlarged sectional view taken substantially on the line 12--12 of FIG. 10;

FIG. 13 is a sectional view taken along the line 13--13 of FIG. 10 showing the latch in depressed condition;

FIG. 14 is a sectional view taken along the line 14--14 of FIG. 10 showing the buckle in latched condition;

FIG. 15 is a sectional plan view taken along the line 15--15 of FIG. 12;

FIG. 16 is a sectional end view taken along the line 16--16 of FIG. 12;

FIG. 17 is a sectional end view taken along the line 17--17 of FIG. 12;

FIG. 18 is a plan view with the push button lever employed in the embodiment of FIGS. 10 to 17;

FIG. 19 is a side elevation of the push button lever;

FIG. 20 is a plan view of the clevis employed in the embodiment of FIGS. 10 to 17;

FIG. 21 is a sectional view taken along the line 21--21 of FIG. 20;

FIG. 22 is a plan view of the latch hinge employed in the embodiment of FIGS. 10 to 17;

FIG. 23 is a side elevation of the latch hinge of FIG. 22;

FIG. 24 is a plan view of the connector guide employed in the embodiment of FIGS. 10 to 17;

FIG. 25 is a side elevation of the connector guide of FIG. 24;

FIGS. 26, 27 and 28 are respectively plan, end and side views of one electrical switch housing employed in the embodiment of FIGS. 10 to 17.

With reference to the embodiment of FIGS. 1 to 6, fabric belt ends 10 and 11 are attached by conventional means respectively to connector tongue 12 and cylindrical pin 13 extending through spaced ends 14 of clevis 15 having conically tapered apertures 16 formed to seat latch 17 which, as best shown in FIG. 3, is constructed as the frustum of a cone seated by a press fit on hinge 18 having integral ears 19 pivoting on cylindrical pin 13. Coiled compression spring 20 piloted on locator pin 21 seated in cover 22 engages spring pocket 23 urging latch 17 into seated position as shown in FIG. 3. Resilient rubber push button 24 seated on clevis 15 within aperture 25 in cover 22 has a central projection 26 engageable with tapered planar surface 27 at the top of latch 17 providing a push button means to manually depress latch 17 to the release position shown in FIG. 4 where surface 27 of latch 17 retracts within the lower aperture 16 providing clearance for partial retraction of connector tongue 12, whereupon release of push button 24 will permit complete retraction to disengage the buckle.

To engage the buckle, depression of push button 24 will likewise permit partial insertion of connector tongue 12 up to projection 26 following which release of the push button will permit completion of insertion to the point where spring 20 engages latch 17. From the above description and inspection of FIG. 3 it will be understood that the solid metal latch 17 engages both conical aperture surfaces 16 to place both legs of clevis 15 under tensile load as a like tensile load is applied to connector 12. The solid metal construction of conical latch 17 is well able to withstand any tensile load imparted by the respective clevis and connector elements. Thus, no compressive loading on any elongated pivoted latch plate leading to bending loads and failures under high emergency impact is in any way involved in the present buckle. As applied to an emergency release belt connection in a passive restraint system which need be engaged only once upon installation subject to emergency release if necessary at the time of an accident, any inconvenience in requiring depression of the push button for initial engagement is a minor consideration and the simplicity as well as the inherent strength recommends this construction for such installations.

With reference to FIGS. 7, 8 and 9 a modification of the first embodiment illustrates a still simpler construction dispensing with hinge 18 as a mounting element for modified latch 28 which is directly mounted in recess 29 in modified cover 30 which houses push button 31 adapted to engage an upper shallow conical surface of latch 28 providing required clearance for either insertion or withdrawal of connector tongue 33 when push button 31 is depressed as shown in FIG. 9 in a manner similar to the previously described embodiment.

The latch in both versions of the first embodiment is provided with a conical surface matching the conical tapered apertures in clevis and connector elements. The included angle of the conical surface, such as 10.degree., is less than the angle of friction for mating surfaces to provide self-locking under load that is sufficiently close to the angle of friction to assist in unlocking under load when the release button is manually depressed. The top surfaces 27 and 32 of the respective latches are beveled sufficiently to provide clearance for partial insertion and withdrawal in the deflected conditions shown in FIGS. 4 and 9. Each of the two versions of the first embodiment has been test loaded to provide a six thousand pound system using a clevis of the proportions shown with 0.067" thickness of clevis stock made of SAE 4130 steel together with a 0.090" thick connector tongue.

With reference to FIGS. 10 to 28, in order to provide the convenience feature of conventional prior art buckle latches which are automatically deflected to provide engagement upon insertion of the connector tongue without need for manually depressing the release button, the same principle of high load capacity is achieved for a latch engagement of clevis and connector tongue similar to the first embodiment with an added feature of latch deflection responsive to beveled extension 34 and latch hinge 35 pivoted through ears 37 to cylindrical attachment pin 38 and otherwise similar to construction and operation to hinge 18 of the first embodiment. Supplemental slot 39 in connector tongue 40 accommodates the return of latch hinge 35 from a fully deflected position as shown in FIG. 13 to a latch engaging position as shown in FIG. 12 through the action of a pair of spring clips 41 attached to the upper outer edges 42 of clevis 43 retained by a dimpled engagement 44 in spring and clevis surfaces and effective through spring arms 45 shown in FIG. 17 to normally retain latch 46 in fully engaged position as shown in FIGS. 12 and 16. In order to maintain latch 46 in proper orientation side slots 47 are provided to engage retaining margins 48 formed in hinge 35.

As best shown in FIGS. 12, 15, 18 and 19, release lever 49 is formed as a stamping having side projections 50 projecting down to engage hinge 35 between its upwardly projecting locating ears 51. Release lever 49 having arcuate extension fingers 52 engaging annular projections 53 in plastic switch housing 54, shown per se in FIGS. 26, 27 and 28, accommodating switch wires 55 which provide a circuit closed by forward end 56 of connector 40. With reference to FIG. 27 slots 57 in switch housing 54 engage corner projections 58 of clevis 43 shown in FIGS. 20 and 21 to provide a fixed pivot fulcrum for release lever 49.

Plastic guide 59, illustrated per se in FIGS. 24 and 25, is secured to the end 60 of clevis 43 by projections 61 having holes 62 corresponding to clevis holes 63 for suitable attachment screws or rivets 64. Guide 59 is recessed at 65 to accommodate tapered cam projection 34 of hinge 35 and is recessed above guide surfaces 66 to accommodate depression of release lever 49. Tapered guide surfaces 67 assist in locating the nose of connector 40 for insertion between spaced sides 68 of clevis 43.

Cover 69 is provided with square opening 70 exposing lever 49 for thumb depression to release the latch. Retention projections 71 of cover 69 engage adjacent surfaces 72 of clevis 43 when the assembled latch with guide 59 secured thereto is inserted through the end of the cover and pressed into the position shown in FIGS. 12 and 14.

In the above described embodiments the clevis is formed as an integral unit by bending steel strip stock, having a central opening stamped out to accommodate fabric belt attachment, with arcuate sides to accommodate cross pin insertion. As an alternate construction the clevis strength can be provided in a substantially equivalent manner by fabrication of two pieces of like strip stock slotted at the ends for belt attachment with suitable provision for radiused engagement at the loop end of the fabric belt.

With regard to the engaging surfaces of the latch with clevis and connector apertures, conical configuration of aligned clevis apertures matching the conical surface of the latch pin has been illustrated in the respective embodiments which may be theoretically optimum for minimizing unit compressive stress at the engaging surfaces under high belt loading. Nevertheless as a practical matter it has been found satisfactory and in some respects preferable to construct the clevis apertures as well as the connector aperture as cylindrical holes of the same diameter as the base of the latch pin cone. In using such alternative construction the latch pin is provided with a 10.degree. included angle and polished conical surface at Rockwell C-50 for minimizing friction. A lower hardness such as Rockwell C-38 is provided for the clevis and connector in order to avoid brittle fractures and allow mating surfaces of both clevis and connector to "Brinell" or yield in compressive contact with the harder latch and conform to its smooth surface. This approach avoids any tolerance problems in manufacturing which might allow the forward edge of the latch to contact and hang up on the underside of the top hole in the celvis causing a "false latch" condition with only one-half of the clevis engaged. With the two holes of equal diameter and reamed to provide accurate alignment as well as equal size, any such false latching is geometrically impossible. In samples tested to 6,000 pounds it was found that at a 600 pound load the latch pin leaned sufficiently to contact the edge of the upper hole and, after the maximum load was released, the latch returned to its original position with no permanent set in the latch carrier. With the latch hinged as shown there is always more clearance at the top hole than at the bottom and any misengagement is accordingly impossible.

From the foregoing description of both embodiments it will be understood that the same clevis latch engagement of the connector is accomplished; however, with a convenience feature of automatic latching upon insertion of the connector tongue being provided by the second embodiment of FIGS. 10 to 28.