US3711904A

US3711904A - Safety belt buckle

Info

Publication number: US3711904A
Application number: US00195107A
Authority: US
Inventors: J Gavagan
Original assignee: Irvin Automotive Products Inc
Current assignee: Irvin Automotive Products Inc
Priority date: 1971-11-03
Filing date: 1971-11-03
Publication date: 1973-01-23
Anticipated expiration: 1990-01-23

Abstract

An improved safety belt buckle adapted to receive a tongue having an aperture therethrough adjacent one edge is disclosed. The buckle includes a base having a steep upwardly extending projection adjacent the buckle''s front edge, a tongue dislodging member on the base adjacent to the projection, and a tongue control member which normally overlies and locks the tongue in position and which is moved rearwardly to free the tongue. During rearward movement of the control member, it contacts the dislodging member effecting upward movement of the dislodging member and tongue to forceably free the tongue.

Description

United States Patent 91 Gavagan et al.

[ Jan. 23, 1973 SAFETY BELT BUCKLE 211 App]. No.: 195,107

[52] U.S. Cl. ..24/230 AK [51] Int. Cl. ..A44b 11/26 [58] Field of Search ..24/23O AK, 230 AN [56] References Cited UNITED STATES PATENTS 3,399,431 9/1968 Shanklin ..24/230 AK 3,568,267 3/l97l Lefort ..24/230 AK Primary Examiner-Bernard A. Gelak Attorney-James E. Ryder et al.

[57] ABSTRACT An improved safety belt buckle adapted to receive a tongue having an aperture therethrough adjacent one edge is disclosed. The buckle includes a base having a steep upwardly extending projection adjacent the buckles front edge, a tongue dislodging member on the base adjacent to the projection, and a tongue control member which normally overlies and locks the tongue in position and which is moved rearwardly to free the tongue. During rearward movement of the control member, it contacts the dislodging member effecting upward movement of the dislodging member and tongue to forceably free the tongue.

PAIENTEDJAN 23 mm W 1 m 3 3.71 1. 904

5 Nmz m m w fl AP PATENKB m 23 1975 SHEET 2 [1F 3 INVENTORS Jknas 4. Gal/46am Pmimmm 23 ms 3.711.904

' SHEET 3 OF 3 ":2 no no I64 lo I00 41 9 66 5e 40 mo Ti E 28 I N VEN TORS 24 (Lives 4. 69m GAA/ 50 BY 4011/6 Ewe/x2 J SAFETY BELT BUCKLE BACKGROUND This invention relates to seat belt or safety belt buckles assemblies and, more particularly, to a safety belt buckle having an improved release mechanism which increases the release reliability of the buckle, especially under high load.

A safety belt buckle assembly includes a tongue attached to a safety belt webbing and a buckle attached to another strip of webbing. Both webbings are firmly attached to the vehicle and the tongue is insertable and releasably lockable within the buckle. Many different types of safety belt buckles have been designed for the automotive and aircraft industry. The two major design criteria for safety belt buckles are (a) to remain closed holding the tongue when the buckle assembly is placed under high tensile load, such as during a crash and (b) to reliably and quickly release the tongue when desired with slight effort even though the buckle assembly is under high load. It also is desirable to minimize the size of the buckle assembly.

One type of safety belt buckle design incorporates a push button release mechanism and a slide action latch or blocker, the blocker serving to retain the tongue and being moved into a release position by depression of the push button. Such a design is described in U.S. Pat. application Ser. No. 781,016 filed on Dec. 4, 1968, now U.S. Pat. No. 3,644,967 and assigned to the assignee of the present invention. The present invention constitutes an improvement over that design in that specific means are provided to insure release of the tongue when so desired, even under high tensile load, and to improve the locking characteristics when it is desired for the safety belt buckle to retain the tongue.

Accordingly, it is one object of this invention to provide an improved safety belt buckle which effectively maintains the tongue locked within the buckle when subjected to a high tensile load which tends to pull the tongue out of the buckle and yet will easily and quickly release the tongue when so desired even though the safety belt buckle assembly is subjected to a high load.

Another object of this invention is to provide a seat belt buckle capable of repeated use with minimum wear and damage.

BRIEF DESCRIPTION Briefly described, this invention in one form comprises the buckle portion of a safety belt buckle assembly, the buckle being adapted to releasably receive a tongue and lock the tongue within the buckle. The buckle is of the push button type whereby depression of the push button forces a cam pad downwardly to react against a cam surface on a slidably mounted blocker. The blocker is slidably mounted on the base of the buckle and is spring biased toward the front or entrance of the buckle. Adjacent the front of the buckle the base is embossed to form an upwardly projecting ramp designed to mate with an aperture extending through the tongue so that when the tongue is placed in position within the buckle, the ramp fits within the aperture providing an abutment to prevent the tongue from being accidentally retracted. The blocker normally overlies a portion of the tongue to prevent the tongue from becoming displaced.

In previous buckle designs, the ramp has had an inclined surface on the rearward side thereof with a slope of approximately 96 or less with respect to the base; however, by virtue of this invention the rearward side of the ramp may be formed with a 94 1 slope. The corners of the rear edge are rounded and sloped inwardly to prevent catching the tongue during tongue removal. Because the ramp more closely approaches a vertical position, the component in the vertical direction of a tensile force exerted on the buckle assembly is reduced thereby reducing the force exerted on the blocker resulting in an increased life of the buckle. Furthermore, the more vertical ramp provides an increased abutment surface to prevent accidental release of the tongue.

In order to assist removal of the tongue from the buckle when such is desired a stripper is provided within the buckle. The stripper has a forward nose portion normally resting in a depression provided in a position spaced rearwardly from the ramp and designed to reside under the forwardmost portion of the tongue when the tongue is placed within the buckle. The stripper is also provided with a shoulder adjacent its rear end positioned such that when the blocker is moved rearwardly away from the tongue, it will abut against the stripper shoulder carrying the front portion of the stripper rearwardly and upwardly for a short distance.

When using this safety belt buckle assembly, the vehicle passenger inserts the tongue within the buckle. During this insertion the forward portion of the tongue rides up over the ramp and abuts against the forward portion of the blocker causing the blocker to move rearwardly until suchtime as the aperture of the tongue is aligned with the ramp. At that moment the tongue is forced downwardly by the blocker so that the ramp fits within the aperture and serves as a restraining abutment. The blocker is forced forwardly by a spring causing it to ride over the front portion of the tongue locking the tongue in position. The forward position of the stripper rests under the forwardmost portion of the tongue. When it is desired to separate the tongue from the buckle, the push button is depressed forcing the cam pad downwardly resulting in rearward motion of the blocker until such time as the blocker no longer is over the forward portion of the tongue. As the blocker moves rearwardly, the forward portion of the stripper is forced to ride up along the stripper depression forcing the forward portion of the tongue upwardly and releasing it from the ramp abutment permitting the tongue to be easily removed from the buckle.

DESCRIPTION OF THE DRAWINGS These and other objectives and advantages of this invention will be better understood from the detailed description below taken in conjunction with the drawings in which:

FIG. 1 is a perspective illustration of a safety belt buckle assembly of the push button type.

FIG. 2 is a perspective view of a safety belt buckle assembly formed in accordance with this invention with the cover removed to expose the interior of the buckle.

FIG. 3 is a perspective exploded view of the safety belt buckle assembly of FIG. 2.

FIG. 4 is a partially cut away plan view of the safety belt buckle of FIG. 2.

FIG. 5 is a sectional view taken along the line 5-5 of FIG. 4.

FIG. 6 is a sectional view taken along the line 66 of FIG. 4.

FIG. 7 is a sectional view taken along the line 55 of FIG. 4 but illustrating the buckle in its tongue release position.

FIG. 8 is a plan view of a portion of the buckle illustrating the stripper in its normal position.

FIG. 9 is a magnified partial sectional view illustrating the normal position of the stripper and its relationship with the tongue.

DETAILED DESCRIPTION The safety belt buckle assembly 10 of this invention is formed of two primary portions, a buckle 12 and a tongue 14. Both the buckle 12 and tongue 14 have safety belt webbing l6, 18 attached thereto respectively with the remote ends of the webbing (not shown) being firmly attached to the vehicle by conventional means not part of this invention. The tongue is formed with a webbing receiving aperture 20 and a locking aperture 22 which enables the tongue 14 to be locked within the buckle 12. In order to simplify description of this invention but not to limit the scope of the invention, the entrance end of the buckle is referred to as the front end and the terms upper and lower refer to the assembly orientation illustrated in FIG. 1.

The buckle 12 comprises a base 24 formed with a pair of

upstanding guide rails

26, 28 having inwardly extending

guide shoulders

30, 32 formed therewith near the front end of the buckle. An aperture 34 is provided through the rear end of the base 24 to receive the safety belt webbing l6. Centrally located adjacent the front end of the buckle is an upwardly projecting ramp 36 designed to mate with the locking aperture 22 through the front end of the tongue 14. As can be seen in FIG. 5, the front wall 37 of the ramp 36 is sloped upwardly at an angle 38 of approximately 30 to the horizontal or upper surface of the base 24. This relatively shallow slope guides the front end of the tongue 14 upwardly and over the ramp 36 and into the buckle 12. The rear wall 39 of the ramp 36 is steep and forms an angle 40 of 94 1 94 to the horizontal or upper surface of the base. Since the rear wall 39 of the ramp 36 serves as an abutment against which the front bar 42 of the tongue 14 reacts when a tensile load is placed on the safety belt, it is preferred to have the rear wall slope approach 90 so that the high load reaction forces will be in a horizontal direction and be resisted by the ramp rather than in a vertical direction tending to force the tongue upwardly to permit the tongue to be dislodged from the ramp. In other words, it is preferred to minimize the vertical component of the load forces. While this was realized in the past, prior art designs usually limited the rear wall slope to 96 or less because if the slope was steeper, release of the tongue was found to be more difficult and less reliable since the tongue often failed to ride up and over the ramp. Also, it has been found that the tongue tends to wear a small groove 41 (see FIG. 9) in the rear wall of the ramp which hinders intentional release of the tongue. When such a groove was formed in a ramp rear wall of prior art buckle designs especially if the ramp rear wall had a slope steeper than approximately 96, the buckle release reliability was poor. The buckle of this invention permits the use of a steep 94 ramp rear wall and improves the buckle release reliability.

The ramp also is provided with rounded

rear corners

43, 44 which slope inwardly toward their respective opposed front corners. This structure is to prevent unintentional locking of the tongue within the buckle when it is desired to release the tongue such as may be caused when the load applied to the tongue is at an angle to a longitudinal axis through the buckle and tongue of the assembly 10. By rounding and sloping the

corners

43, 44 the tongue will ride up and over the ramp 36 even if an angular force is applied to the tongue 14.

Displaced rearwardly from the ramp 36 and aligned therewith is a U-shaped depression or recess 50 wherein the

opposed legs

52, 54 and the center portion 56 slope upwardly toward the rear upper surface 58 of the base. The depression 50 is located so that it lies below the tongue front bar 42 as may be seen in FIG. 9. Aligned with the depression 50 and spaced rearwardly therefrom is an upwardly extending flange 59 having a pair of holes 60, 62 therethrough. The flange 59 can be forged from the wall fonning the inner periphery of the aperture 34.

The depression 50 and flange 59 receive a tongue dislodger or stripper 64 which may be formed of steel wire. The stripper has a pair of upwardly bent mounting ends 66, 68 adapted to be inserted through and abut against the flange 59. The stripper then extends forwardly and forms a pair of

wings

70, 71 which extend upwardly and transverse to the longitudinal axis of the buckle and each of which have a

portion

72, 73 thereof extending forwardly to provide resilience. The stripper then continues forwardly with two

legs

74, 76 and terminates with a front nose 78. The two

side bars

74, 76 at the nose section are bent downwardly to fit within the depression 50 and the front bar 79 of the nose is provided with a slightly elevated central section 80. As can be seen in FIGS. 4, 5, 7, 8 and 9, the rear end of the stripper is retained in place by the flange 59 and the remainder of the stripper rests on the upper surface 58 of the base while the nose 78 fits within the depression 50 and, therefore, lies under the tongue front bar 42.

A slide action latch or blocker is slidably mounted on the base 24 and is guided in its front-to-rear movement by the

base guide rails

26, 28. The guide shoulders 30, 32 prevent upward displacement of the blocker front end 91. To facilitate this sliding action of the blocker 90 on the base 24, three spaced apart runners 92, 94, 96 are formed on the lower surface of the blocker, two of the runners 92, 94 being formed along the outer longitudinal edges while the third runner 96 is formed axially along the center of the blocker 90. The blocker can be injection molded of a plastic such as polyoxymethylene polymer (for example, Delrin by E. I. duPont de Nemours & Co.) which has a low coefficient of friction on metal. Two

grooves

98, 99 are provided on opposite sides of the center runner 96 to receive the

arms

74, 76 of the stripper 64. A blocker spring 100 is partially inserted through a cylindrical channel 101 through the rear end of the blocker 90 and has its remote end abuting against the upwardly extending flange 59 of the base 24. The spring forces the blocker forwardly so that the blocker front end 91 normally resides in position to overlie the front bar 42 of the tongue 14 in order to maintain the tongue in position within the buckle.

As can be seen from FIGS. 4 and 5, the forward end 102 of the blocker 90 is peculiarly shaped to receive, cam and restrain the front bar 42 of the tongue 14. More particularly, as the tongue enters the buckle 12 it encounters a downwardly sloped cam surface 104 which tends to force the tongue downwardly; however, because the front bar 42 of the tongue is in contact with the upper surface of the ramp 36, the tongue cannot move downwardly. Continued pressure on the tongue toward the rear of the buckle 12 forces the blocker 90 rearwardly against the spring 100 until such time as the tongue aperture 22 is aligned with the ramp 36. At that point the tongue is forced downwardly and the ramp 36 protudes through the aperture 22 and the blocker is rapidly moved forwardly by the spring 100 to place a restraining portion 109 over the tongue bar 42. A recess 110 is provided in the lower front end of the blocker to receive the tongue bar 42 when in the locked position. The contour of the front end 91 of the blocker 90 generally conforms to the contour of the tongue so that the force of the tongue on the blocker during insertion of the tongue in the buckle 12 and the force of the blocker on the tongue when in the closed or locked mode is distributed over a significant area of the blocker rather than being concentrated on a few points. Any tendency of the tongue to move the blocker upwardly away from the base 24 is resisted by the guide shoulders 30, 32.

The upper surface of the blocker 90 is formed with a pair of cam surfaces 112, 114 which slope toward the front end of the buckle 12. These cam surfaces 112, 114 are designed to react with a cam pad 120 for activation of the blocker 90 to release the tongue 14. The cam pad is formed with two triangular bearing surfaces 122, 124 which conform in shape and size to the cam surfaces 112, 114 of the blocker 90. The cam pad may be made of metal or plastic for example zinc, aluminum or Lexan.

A push button 130 having a flat lower surface to press against the upper surface of the cam pad 120 is slidably mounted within a housing 132 of the buckle 12. The housing 132 is formed with a central aperture 134 to provide access to the push button 130. The push button 130 has a pair of

guides

136, 138 spaced apart along one side thereof and a central guide 140 on the opposite side thereof. These guides reside within vertical grooves formed in the

walls

142, 144 of the housing 132 which define the aperture 134 (see FIG. 5). The front wall 144 further includes a camming surface 146 which the forwardly facing surfaces of the cam pad contact. Manual depression of the push button 130 forces the cam pad downwardly and the housing cam surface 146 forces the cam pad to move rearwardly during its downward motion. The cam pad 120 can move rearwardly by sliding along the lower surface of the push button 130. As the cam pad moves downwardly it applies a rearwardly directed force on the blocker 90 forcing the blocker to move toward the rear of the buckle 12 against the force of the blocker spring 100. When the push button 130 is released, the blocker spring 100 forces the blocker 90 forwardly and the blocker cam surfaces 112, 114 apply a force against the cam

pad bearing surfaces

122, 124 forcing the cam pad 120 and push button upwardly to their normal position. 7

To increase the strength and rigidity of the buckle so that it can withstand the extreme forces to which it may be subjected during a crash without collapsing and accidentally releasing the tongue, the buckle housing 132 is formed with a pair of internal recesses 148, 150 each of which receives a steel or

aluminum crush bar

152, 154 respectively. When the housing is snap-fitted onto the base, the crush bars rest against the

upstanding walls

26, 28 of the steel base 24.

When it is desired to release the tongue 14 from the buckle 12, the push button 130 is depressed and the sliding action of the blocker 90 toward the rear of the buckle takes place as described above. As the blocker moves rearwardly from its forwardmost locking position, the rear portion of the blocker contacts the

wings

70, 71 of the stripper 64 forcing the stripper rearwardly. As the stripper moves rearwardly (see FIG. 7) the front nose rides up the

inclined slopes

52, 54 of the stripper depression 50 resulting in an upward force on the front bar 42 of the tongue 14 dislodging the tongue from its normal locked position with respect to the ramp 36. The dimensions of the blocker and stripper are set to permit the blocker to move rearwardly sufficiently far as to no longer restrain upward movement of the tongue 14 before the stripper begins to ride upwardly on the

ramps

52, 54. This delayed action in moving the stripper is accomplished by making the distance between the rear end of the blocker and the

stripper wings

70, 71 equal to the desired amount of travel required of the blocker before the stripper begins to move. This distance is indicated by the dimension line in FIG. 5.

It should be understood that the purpose of the stripper 64 is not to lift the tongue front bar 42 entirely off the ramp 36 but merely to dislodge it from its normal locked position. As is illustrated in FIG. 9, after considerable use of the buckle assembly 10, there is a tendency for the front bar 42 of the tongue 14 to wear a groove 41 in the lower corner of the rear wall of the ramp. Such a groove may tend to hinder release of the tongue when desired, especially if a high load force is applied to the belt buckle assembly. This tendency is overcome by the stripper 64 which dislodges the tongue from its normal position and begins the tongue in its upward movement over the ramp. Since the ramp does have a slope, the tongue will continue to ride up and over the ramp once this motion is begun by the stripper. Through this design, the release qualities of the buckle assembly are improved considerably without increasing the size of the buckle assembly.

FIG. 8 clearly depicts the rounded and sloped

rear corners

43, 44 on the ramp 36 and the purpose of this structure can be best understood by looking at FIG. 8. If the tongue 14 is rotated with respect to the longitudinal axis of the buckle 12 and a high tensile load is applied to the assembly, there is a tendency for the tongue to get wedged in position and not ride up and over the ramp 36. This position will be experienced especially with a shoulder harness safety belt arrangement. By providing the

rounded corners

43, 44 it has been found that the tongue will ride up and over the ramp even if a high load is applied to the tongue at an angle to the buckle. The combination of this corner construction with the action of the stripper 64 provides a highly efficient and reliable buckle release mechanism and the in creased verticality of the ramp wall 39 improves the buckle locking mechanism. These improvements have been obtained without increasing the size of the buckle assembly.

What is claimed as new and desired to be secured as Letters Patent of the United States is:

1. A safety belt buckle adapted to receive a tongue having an aperture therethrough adjacent one edge, the edge and aperture defining a bar, the buckle comprisa. a base having an upwardly extending projection adjacent a front edge, the projection being adapted to project through the tongue aperture,

. tongue dislodging means on the base and having a longitudinally movable nose portion normally located adjacent to the projection,

c. a tongue control member slidably mounted on the base for sliding motion between a locking position adjacent the front edge of the base and a release position spaced from the front edge, the control member being biased toward the locking position and having means for contacting the dislodging means during rearward movement toward the release position, the control member having a restraining portion adapted to overlie the bar when the control member is in its locking position, and

d. activation means for moving the control member rearwardly from the locking position to its release position, the control member contacting the dislodging means during such movement causing the nose portion to move rearwardly and upwardly.

2. A safety belt buckle as defined in claim 1 including a depression in the upper surface of the base on the rearward side of the projection and wherein the nose portion of the tongue dislodging means resides within the depression when the tongue control member is in its locking position.

3. A safety belt buckle as defined in claim 1 wherein the activation means is a push button which moves at an angle to the movement of the tongue control member.

4. A safety belt buckle as defined in claim 1 wherein the means on the tongue control member for contacting the dislodging means is adapted to permit the tongue control member to slide rearwardly from its locking position a predetermined distance before it contacts the dislodging means.

5. A safety belt buckle as defined in claim 4 wherein the predetermined distance is at least equal to the distance the restraining portion must move to cease overlying the bar.

6. A safety belt buckle as defined in claim 2 wherein the wall defining the rear side of the depression remote from the projection forms an obtuse angle with the upper surface of the base.

7. A safety belt buckle as defined in claim 1 wherein the wall of the projection remote from the base front edge inclines forwardly at an angle of substantially 94 56 from the upper surface of the base.

8. A safety belt buckle as defined in claim 4 wherein the wall of the projection remote from the base front edge inclines forwardly at an angle of substantially 94 i 74 from the upper surface of the base.

9. A safety bel buckle as defined in claim 1 wherein the projection is formed with a front wall adjacent the front edge of the base, a rear wall spaced from the front wall and two side walls, the front wall and rear walls sloping toward each other and the rear corners formed by the rear wall and side walls being rounded and sloped inwardly toward their respective opposed front corners.

10. A safety belt buckle as defined in claim 9 wherein the rear wall slopes forwardly at an angle of substantially 94-: 54 from the upper surface of the base.

11. A safety belt buckle adapted to receive a tongue having an aperture therethrough adjacent one edge, the edge and aperture defining a bar, the buckle comprismg:

a. a base having an upwardly extending projection adjacent a front edge, the projection being adapted to project through the tongue aperture, and a depression spaced rearwardly from the projection, the projection having a rear wall sloping forwardly at an angle of substantially 94 i from the upper surface of the base,

b. tongue dislodging means on the base and having a longitudinally movable nose portion normally residing within the depression.

. a tongue control member slidably mounted on the base for sliding motion between a locking position adjacent the front edge of the base and a release position spaced from the front edge, the control member being biased toward the locking position and having means for contacting the dislodging means during rearward movement toward the release position, the control member having a front facing recess adapted to receive the tongue bar and a restraining portion adapted to overlie the bar when the bar is in the recess and the control member is in its locking position, and

. push button activation means for moving the control member rearwardly from the locking position to its release position, the control member contacting the dislodging means during such movement causing the nose portion to move rearwardly and upwardly, the push button moving at an angle to the movement of the control member.

12. A safety belt buckle as defined in claim 11 wherein the means for contacting the dislodging means is adapted to permit the tongue control members to slide rearwardly from its locking position a distance at least equal to the distance the restraining portion must move to cease overlying the bar.

13. A safety belt buckle as defined in claim 11 wherein the tongue dislodging means is biased toward the depression and returns to its normal position when the control member ceases contacting the dislodging means.

14. A safety belt buckle as defined in claim 11 including spring means for biasing the control member toward the locking position, the spring means effecting return of the control member and push button to their normal position upon removal of an activating force on the push button.

Claims

1. A safety belt buckle adapted to receive a tongue having an aperture therethrough adjacent one edge, the edge and aperture defining a bar, the buckle comprising: a. a base having an upwardly extending projection adjacent a front edge, the projection being adapted to project through the tongue aperture, b. tongue dislodging means on the base and having a longitudinally movable nose portion normally located adjacent to the projection, c. a tongue control member slidably mounted on the base for sliding motion between a locking position adjacent the front edge of the base and a release position spaced from the front edge, the control member being biased toward the locking position and having means for contacting the dislodging means during rearward movement toward the release position, the control member having a restraining portion adapted to overlie the bar when the control member is in its locking position, and d. activation means for moving the control member rearwardly from the locking position to its release position, the control member contacting the dislodging means during such movement causing the nose portion to move rearwardly and upwardly.

7. A safety belt buckle as defined in claim 1 wherein the walL of the projection remote from the base front edge inclines forwardly at an angle of substantially 94* + or - 3/4 * from the upper surface of the base.

8. A safety belt buckle as defined in claim 4 wherein the wall of the projection remote from the base front edge inclines forwardly at an angle of substantially 94* + or - from the upper surface of the base.

9. A safety belt buckle as defined in claim 1 wherein the projection is formed with a front wall adjacent the front edge of the base, a rear wall spaced from the front wall and two side walls, the front wall and rear walls sloping toward each other and the rear corners formed by the rear wall and side walls being rounded and sloped inwardly toward their respective opposed front corners.

10. A safety belt buckle as defined in claim 9 wherein the rear wall slopes forwardly at an angle of substantially 94* + or -3/4 * from the upper surface of the base.

11. A safety belt buckle adapted to receive a tongue having an aperture therethrough adjacent one edge, the edge and aperture defining a bar, the buckle comprising: a. a base having an upwardly extending projection adjacent a front edge, the projection being adapted to project through the tongue aperture, and a depression spaced rearwardly from the projection, the projection having a rear wall sloping forwardly at an angle of substantially 94* + or - from the upper surface of the base, b. tongue dislodging means on the base and having a longitudinally movable nose portion normally residing within the depression. c. a tongue control member slidably mounted on the base for sliding motion between a locking position adjacent the front edge of the base and a release position spaced from the front edge, the control member being biased toward the locking position and having means for contacting the dislodging means during rearward movement toward the release position, the control member having a front facing recess adapted to receive the tongue bar and a restraining portion adapted to overlie the bar when the bar is in the recess and the control member is in its locking position, and d. push button activation means for moving the control member rearwardly from the locking position to its release position, the control member contacting the dislodging means during such movement causing the nose portion to move rearwardly and upwardly, the push button moving at an angle to the movement of the control member.