US3390908A

US3390908A - Pivoted blade lock device

Info

Publication number: US3390908A
Authority: US
Inventors: Ernest L Schlage
Original assignee: Schlage Lock Co LLC
Current assignee: Schlage Lock Co LLC
Priority date: 1965-03-04
Filing date: 1965-03-04
Publication date: 1968-07-02
Anticipated expiration: 1985-07-02

Description

y 2, 1963 E. L. SCHLAGE 3,390,908

PIVOTED BLADE LOCK DEVICE Filed March t 1 y 2, 1968 j E. SCHLAGE 3,390,908

PIVOTED BLADE LOCK DEVICE Filed March 4, 1965 5 Sheets-Sheet 2 mvsmon.

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0...] MZWJ lrraaviqy 1968 E. SCHLAGE 3,390,908

Q PIVOTED BLADE LOCK DEVICE Filed March 4, 1965 5 Sheets-Sheet 3 mvEN'rOR. izwrsr L. Janus! flrraaviri United States Patent 3,390,908 PIVOTED BLADE LOCK DEVICE Ernest L. Schlage, Burlingame, Califi, assignor to Schlage Lock Com any, a corporation Filed Mar. 4, 1965, Ser. No. 437,205 7 Claims. (Cl. 292195) My invention relates to means for holding a door in position in a door frame and is particularly concerned with such a device especially for use in doors that are quite thin, so thin as not to admit of the installation of the customary commercial lock, and also relates to installations in which the door is able to swing both ways through the door frame on which it is mounted by the customary hinges.

An object of the invention is to provide a pivoted blade lock device which can be manufactured in a relatively thin form so that it can easily be installed within the confines of a thin door.

Another object of the invention is to provide a pivoted blade lock device which can be used, although not necessarily so, in connection with a door designed and mounted to swing both ways with respect to its door frame.

Another object of the invention is to provide a pivoted blade lock device which cannot easily be actuated in an unauthorized fashion.

Another object of the invention is to provide a pivoted blade lock device having a deadlatch feature.

An additional object of the invention is to provide a pivoted blade lock device that can be utilized effectively with a standard strike device or a special strike device.

Another object of the invention is in general to pro vide an improved lock device.

Other objects together with the foregoing are attained in the embodiments of the invention described in the accompanying description and illustrated in the accompanying drawings, in which:

FIGURE 1 is an isometric view showing one form of pivoted blade lock device constructed pursuant to the invention as it is installed in a typical environment;

FIGURE 2 is a side elevation of the structure shown in FIGURE 1 with portions of the mechanism broken away to disclose the interior and with portions of the environmental structure broken away to reduce the size of the figure;

FIGURE 3 is a detail in elevation, the view being indicated by the line 33 of FIGURE 2;

FIGURE 4 is a detail cross section, the plane of which is indicated by the line 44 of FIGURE 2;

FIGURE 5 is a side elevation of a modified form of pivoted blade lock device;

FIGURE 6 is a cross section on a vertical longitudinal plane of a further modified form of pivoted blade lock device in installed condition, certain parts being omitted to reduce the size of the figure;

FIGURE 7 is a cross section, the plane of which is indicated by the line 77 of FIGURE 6;

FIGURE 8 is a cross section, the plane of which is indicated by the line 88 of FIGURE 6;

FIGURE 9 is a cross section on a vertical longitudinal plane through a still further modified form of the pivoted blade lock device shown in installed condition; and

FIGURE 10 is a cross section, the plane of which is indicated by the line Ill-10 of FIGURE 9.

As particularly shown in FIGURES 1-4 inclusive, a practical form of the pivoted blade lock device pursuant to the invention is designed for installation in connection with a door frame 6 including an upright door jamb 7 having a transverse, vertical face 8 and connected by means of a lintel 9 with an upright hinge post 11 of the door frame. Designed to operate on the door frame and within the opening 12 defined thereby is a door 13. Along one edge 14 the door is connected to the frame 6 by ap- 3,3903% Patented July 2, 1968 "ice propriate hinges 16. These are designed to permit the door 13 to swing With respect to the door frame about a vertical axis 17. Depending upon the installation, the door panel 13 can be mounted to swing on one side only of the door frame. In this case, the hinges are arranged so that the axis 17 is displaced to one side of the frame 6 and of the door 13. Another installation can be arranged by providing appropriate hinges permitting the door 13 to swing on both sides of the door frame. In this instance the axis 17 of the hinges, whether single or double hinges are used, can be considered to be midway between the sides of the door frame substantially in the median vertical plane of the door 13.

In the first instance, there is customarily provided a door stop (not shown) to limit the movement of the door in one direction, whereas in the second instance no door stop is provided as the door is free to swing to either side of its center position and to swing through the center position when appropriately operated. Under both instances, the door 13 has an upright, planar face 19. In one, central position of the door in the door frame, the face 19 confronts the planar face 8 of the door frame, there being a slight clearance between the confronting faces 8 and 19 to afford room for the arcuate movement of the door.

Despite the fact that the door always swings in a circular are about the axis 17, it can be considered that the motion of the door edge when near its center or closed location is substantially in a horizontal direction approximately perpendicular or normal to the plane of the closed door 13 and parallel to the plane of the faces 8 and 19. Since the door is customarily quite thin, the faces 8 and 19 need not be exactly planar nor parallel, and may be curved or divergent, but these geometric designations are close approximations and are used for clarity of description.

Pursuant to the invention, there is mounted on the door 13 an appropriate latch unit 21. This is associated and interconnected with an actuator 22 not disclosed in detail since it is of a generally recognized, standard form mounted on and secured to the door 13. Usually, there is an actuating knob 23 on one side provided with a key mechanism 24. Usually, there is also a comparable actuating knob 23 on the other side of the door panel. When either of the knobs is actuated, the mechanism transmits a corresponding motion to the latch unit 21.

The latch 'unit includes a housing 26 or frame of thin, generally rectangular contour enclosing a central chamber 27 and joined to a latch plate 28 recessed within and substantially coplanar with the face 19 and secured in position by fasteners 29. The plate 28 has a generally rectangular latch opening 31 within and through which moves a blade 32 mounted on a cross pin 33 serving as a pivot mounting with the axis of the pin 33 disposed in a horizontal direction. When the door is closed, the pin axis is parallel to the planes of the surfaces 8 and 19 and also is parallel to the direction of motion of the door. The pin 33 is mounted in the housing 21 and in the blade at a location close to the plate 28 so that most of the blade swings through the latch opening 31 and when in a retracted position substantially fills most of the opening 31. In a projected position, the blade tipextends a desired distance from the surface 19, in practice approximately three-quarters of an inch.

In order that motion of the actuator 22 can be imparted to the blade 32, the blade is provided with a slot 38 within which fits an actuating pin 39 mounted in the upcurved end of a bar 41. The bar is confined to rectilinear translation by the walls of a passage 42 formed in the thickened interior end of the housing 21. The pin 39 operates within the slot 38 and the swinging of the blade is in accordance with the motion of the bar. The radial location of the pin 39 with respect to the pivot pin 33 is such that the desired excursion of the tip of the blade 32, such as three-quarters of an inch, is accomplished with a shorter motion of the bar 41 imparted to it by the knob 23 acting through an appropriate bar terminal 43, the actuator 22 and the housing 21 being connected by a similar interengagement 44-.

Conveniently, the housing is made in two halves secured together by through fastenings 46 and is installed by mortising the door, whereas the actuator is installed in the usual way by a through bored hole. Various interconnections may be provided between the bar 41 and the actuator. They can be connected without substantial lost motion or there can be lost motion permitting the bar to be moved inwardly While the actuator is stationary. If the actuator return springs (not shown) are also effective on the bar 41, no other spring is needed, but in any case the bar 41 can also have a biasing means such as a return coil spring 45 held between the housing and a bar shoulder. The return spring is compressed when the blade 32 is depressed into the housing by pressure on the exterior portion of the blade.

Pursuant to this invention, a strike device is provided to cooperate with the blade 32. Recessed into the door frame 6 by appropriate mortising through the face 8 of the door jamb 7 is a strike unit 51. This includes a generally planar plate 52 set with its outer face substantially flush with the surface 8 and held in position by fasteners 53. The strike plate is adjacent a strike recess 54 within the jamb 7, the recess being of sufficient width and depth readily to receive the projected blade 32. The strike plate 52 is provided with a strike opening 56 of generally rectangular configuration positioned substantially to confront the latch opening in the latch unit 21 so that when the door is in central position or is closed, the blade 32 can readily be received through the latch opening 56 with substantial clearance in a vertical direction if desired, but with substantially no lateral clearance in a horizontal direction.

The strike unit includes means for engaging and actuating the blade 32. The plate 52 on one side only, in the event the door is mounted to swing only in one direction, but on both sides in the event the door is designed to swing in both directions, has an integral extension 58 or wing located in substantially horizontal alignment with the opening 56. The extension 58 has a cam edge 59 along one portion and has a relatively straight edge 61 along another portion, the edges 59 and 61 merging in a smooth curved edge 62. The cam edge 59 merges smoothly with one of the side edges 63 of the strike plate.

The configuration of the cam edge 59 is such as to abut or engage a similar cam edge 64 on the exposed portion of the blade 32. The edges 59 and 64 are approximately at right angles. The configuration is such that the portion of the cam edge 59 farthest from the door jamb first encounters the portion of the substantially radial cam edge 64 closest to the pivot pin 33. As the door swings with respect to the door frame, or as there is relative motion between the strike unit and the latch unit, particularly as the door approaches its closed position substantially in a predetermined direction, the cam edge 59 bears upon the cam edge 64 in a progressive fashion. The blade 32 is progressively depressed until the lowermost portion of the blade or that portion farthest from the pivot pin 33 is substantially flush with the plate 28. The tip of the blade can then ride over the strike plate until the blade is in alignment with the strike opening 56. Thereupon the spring mechanism in the actuator, being effective through the bar 41, causes the blade 32 quickly to swing through the

openings

31 and 56, to span the gap 12, and to be positioned within the strike recess 54. The blade is laterally confined between the sides of the opening 56, to index and hold the door in position with respect to the door frame.

FIGURE 1 includes projection lines 66 to indicate that for selected increments of the radial length of the blade 32 the cam surface 59 can be appropriately contoured so as to afford any desired amount of depression of the blade as the door swings toward its closed position. Usually, substantially equal increments of latch blade motion are provided for equal angular intervals of door closure. With this arrangement, the vertical height of the cam surface 59 can be substantial. Even though the cam surface is on a planar plate located approximately in the direction of closure of the door substantially normal to the plane in which the blade 32 swings, there is nevertheless a favorable mechanical interengagement with approximately point contact. The blade 32 swings in regularly and easily and the door is closed and latched with little effort. If the door is mounted to swing through the opening, then the extension 58 is duplicated by a mirror symmetrical wing or extension 67. Since the blade 32 is already symmetrical, no alternation need be made in it for either type of installation. In practice, some rounding of the contacting edges is preferred either on the blade 32 or on the plate 52 or on both.

Under some circumstances, it is advisable to rovide a blade lock device which is proof against tampering. A thin instrument such as a card inserted into the opening 12 above the blade and then lowered will cam against the blade surface 64 and will release the lock. To prevent this, there is provided in the form of device particularly shown in FIGURE 5 a latch unit housing 81 associated with a latch plate 82 slightly recessed in the face 83 of a door 8-: and secured by fasteners 35. The housing 81 is associated with a standard lock actuating unit (not shown) connected to operate a bar 87 to swing a latch blade 88 mounted on a pivot pin 89 situated in the housing 81. The connection between the rectilinearly movable bar 87 and the blade 88 is by means of a connecting pin 91 operating in a slot 92. Thus when the bar 87 is translated, the blade 88 is swung.

To cooperate with the latch unit, there is provided in the door jamb 93 a strike plate 94 secured on the jamb face 96 by fasteners 97. The plate 94 opposite the blade 88 has a strike opening effective to receive projecting portions of the blade and the door jamb also has a recess 98 for that purpose.

The blade 88 does not have a continuous exposed edge, but rather is contoured to afford a substantially radial carnming edge 99 merging with a circular are surface 361 and a rectilinear surface 102. This is arranged with the arcuate surface 101 to define a notch in the blade edge 99. The location of the surfaces is such that the only portion of the blade exposed within the gap between the faces 83 and 96 when the blade is projected has a surface substantially circular about the pin 89 as a center. With this arrangement, when any blade or card is moved in the gap 100 either upwardly or downwardly, no substantial rotational component can be imparted to the blade. The blade is substantially deadlatchcd and cannot be reversed by vertical forces exerted upon the blade itself.

The cam edge 99 is not sufficiently extensive to swing the blade 88 for its full travel. The strike plate 94, therefore, is provided with an angularly extending wing 163 so that when the door 8:3 moves toward closed position the leading point or nose 164 of the blade is cammed horizontally and laterally against the inclined wing 103. The blade 88 is thus swung into its retracted position and then springs out through the opening in the strike plate 94. This action is different from that in the FIGURES 1-4 device. Therein all of the camming action to depress the strike plate occurs along the radial cam edge in a generally vertical direction, whereas in the FIGURE 5 device the carnming action occurs on the nose 164 of the blade and in a generally horizontal direction. If the door 84 swings both ways through the opening of the jamb, there are extensions such as 103 on both sides of the plate 94.

Under some circumstances, the scrni-dcadlatch action of the FIGURE 5 device may not be sutlicient and a full deadlatch arrangement is provided. As shown in FIG-

URES

6, 7 and 8, the swinging door 111 is mounted, as before, to cooperate with a door jamb 112. The door 111 carries a latch housing 113 secured in position by a latch plate 114 having fasteners 115 entering into the door material. The housing 113 confines an actuating bar 116 to rectilinear translation. A projecting spring 117 at one end bears against a cross pin 118 spanning the sides of the housing 113 and operating in a slot 119 in the bar 116. At the other end, the spring 117 bears against a cross pin 121 in the bar so that the bar is projected toward the left in FIGURE 6. The casing and the bar are both provided with interconnecting devices 122 and 123 to an actuator (not shown) in the usual fashion.

The forward end of the bar 116 is provided with an upturned end 124 having an inclined slot 126 therein. A pin 127 operates in the slot and is mounted on a center blade 128 supported in the housing 113 by a pivot pin 129. Also pivoting around the pin 129 are

deadlatch plates

131 and 132 approximately coextensive with the blade 128. These have free motion with respect to the blade 128 by reason of a lost motion connection. This includes slots 133 in both of the

plates

131 and 132 which cooperate with a cross pin 134 in the central blade 128. The

deadlatch plates

131 and 132 adjacent their lower ends are each provided with a radial surface 136 adapted to abut the forked, straight end 137 of a leaf spring 138. A loop 139 at one end of the leaf spring is seated within a correspondingly shaped portion of the housing 113 and is recurved to provide a finger 141 resting against the side of the housing and holding the blade 128 in position approximately normal to the surface 136.

With this relationship of the parts, any force exerted on the

side plates

131 and 132 tending to rock them inwardly of the housing 113 quickly takes up the lost motion between the radial surfaces 136 and the forked end 137 of the spring so that the

plates

131 and 132 are restrained and cannot then be depressed. This affords an appropriate deadlatch. However, if the blade 128 is itself forced inwardly, a cam surface 142 thereon bears against a downturned cam follower 143 at the center of the spring 138 and cams the leaf spring 138 downwardly out of the way, thus removing the bifurcated end 137 from the path of the surfaces 136. This motion is permitted by movement of the pin 134 toward the other end of the slots 133. When this occurs, all three of the

plates

128, 131 and 132 can be depressed. When released, they spring back to their projected position.

In this instance, the nature of the strike plate 146 on the door jamb 112 is substantially the same as that shown 1 in FIGURE 5, extending on one side only of the jamb in the event the door panel swings in only one direction, but being duplicated on the other side and extending in mirror symmetry therefrom in the event the door swings in both directions.

Under many circumstances, the friction between the nose of the latch blade 128 and the strike plate 146 is reduced by providing the blade 128 with an antifriction roller 147 mounted on a radial pin 148 seated in the central blade 128, there being appropriate notches 149 cut from the

side plates

131 and 132 to afford adequate freedom of motion of the roller 147. Conveniently, the

plates

131 and 132 can be joined or can be made integral by a bridge over the center blade 128, as shown in FIGURE 6.

A somewhat simplified version of the deadlatching arrangement is provided as shown in FIGURES 9 and 10. A latch housing 151 is mounted in a swinging door 152 of the type previously disclosed, the housing being secured to a latch plate 153 appropriately fastened in place. The housing 151 confronts a strike plate 154 mounted in the face of the door jamb 156 in asuitable fashion and has an extension wing 157 for a door swinging only one way and provided with a symmetrical extension wing 158 for a door swinging both ways.

The strike plate 154 has an opening 159 leading to a cavity 161 in the door jamb 156 designed to receive a swinging latch blade 162. This is mounted on a pin 163 supported in the housing 151 and extends through a latch blade opening 164 in the plate 153. The blade 162 is normally urged to project by a coil spring 165 at one end seated in a recess 166 within the housing 151 and at the other end seated in a recess 167 in the blade 162. Also connected to the blade 162 is an actuating bar 168 at its end 169 provided for interconnection with a standard operating device interconnecting with projections 171 on the housing 151.

The bar 168 is confined to rectilinear translation relative to the housing 151 and at its forward end carries a cross pin 172 designed to operate in a straight, horizontal path. The pin 172 extends on opposite sides of the bar 168 and on both sides lies within recesses 173 virtually inverted L-shaped in configuration. This affords a clearance 174 in a horizontal direction for the pin 172, affords a shoulder 176 adjacent the pin 172, and also provides a depending portion 177 beneath the pin 172. The blade 162 cannot swing about the pin 163 when the pin 172 is in the upper portion of the slot 173 adjacent the upper boundary of that slot and the shoulder 176. This is because the blade 162 in rotating about the pin 163 tends to lift the shoulder 176 against the pin 172, but the pin 172 is constrained by the rectilinearly movable bar 168 against any rising or lifting motion. Thus a force exerted along the outer edge 178 of the blade 162 is ineffective and the blade is held in its projected position. This is a fully deadlatched blade.

In order that the blade can swing inwardly upon contact with the

strike plate wings

157 or 158, the blade 162 is provided with a stepped bore 181 extending tangentially to the pivot pin 163 and emerging from the blade at its nose 182. Projecting from the nose is a follower 183 of larger diameter than a rod 184 lying within the stepped bore. A spring 185 at one end bears against the follower 183 and at the other end bears against a shoulder 186 in the stepped bore. The follower 1'83 and the rod 184 are joined together with an enlarged portion 187 of the rod bearing within the smaller diameter of the stepped bore and having its end adjacent the forward end of the bar 168.

When the follower 183 projects in its normal situation under the urgency of the spring 185, it is slightly spaced from the end of the bar 168. When the follower contacts the wing 157, for example, of the strike plate 154, the lateral force thereon is caused by the favorable angularities to drive the follower 183 into the stepped bore 181. This not only compresses the spring 185, but the inner end of the rod 184 bears against the adjacent forward edge of the bar 168 and cams the bar 168 slightly to the right in FIGURE 9. That moves the pin 172 away from the shoulder 176 to occupy the upper right-hand portion of the slot 173. Further tangentially inward movement of the follower 183 is precluded. Either the bearing of the follower or the bearing of the nose 182 of the blade 162 against the strike plate wing 157 swings the blade inward- 1y. This can easily occur since the pin 172 is received in the depending portion 177 of the slot 173 and the discrepancy between the circular motion of the blade 162 and the rectilinear motion of the bar 168 is accommodated.

When the force tending to depress the blade is removed, the spring 165 urges the blade to project into the cavity 161 through the strike plate opening 159. The bar 168 is transmitted to its extreme left-hand position in FIGURE 9 by the normal spring mechanism in the actuator (not shown) which always urges the bar 168 to the left unless a superior force actuates it to the right. With this form of device, the door, although extremely thin, carries an effective, swinging blade latch device with a deadlatch feature, the door being effective to swing to one side only of the door frame or, if desired, to swing to 7 either side of the door frame and in either case to be firmly locked in its center location.

What is claimed is:

1. A pivoted blade lock device comprising a strike unit and a latch unit having two vertical faces adapted to move substantially into and out of confronting relationship by motion relative to each other in a predetermined substantially horizontal direction parallel to said faces, said strike unit having a plate defining one of said vertical faces and having a strike opening therein, means on said plate horizontally aligned with said strike opening and defining a first cam edge the active portion of which has a slope inclined toward said strike opening; and said latch unit having a plate defining the other of said vertical-faces and having a latch opening therein adapted to confront said strike opening, a vertically disposed blade, and means for mounting said blade on said latch unit for swinging movement through said latch opening about a pivotal axis adjacent one end of said latch opening and extending in said predetermined horizontal direction when said faces are in said confronting relationship, said blade having a second cam edge adapted to abut said first cam edge.

2. A pivoted blade lock device as in claim 1 in which said second cam edge extends approximately radially of said axis.

3. A pivoted blade lock device as in claim It in which the part of said active portion of said first cam edge horizontally farthest from said strike opening abuts the part of said active portion of said second cam edge radially closest to said axis.

4. A pivoted lade lock device comprising a latch unit including a plate having a latch opening therein, a vertically disposed blade, means for mounting said blade on said latch unit for swinging movement through said latch opening about a pivotal axis adjacent one end of said latch opening and extending in a horizontal direction, said blade having a cam edge extending approximately radially of said axis, and a strike unit including a plate having a strike opening therein adapted to receive said blade, and edge means on said plate adapted to abut said cam edge radially closest to said axis when said latch unit and said strike unit are relatively far apart and progressively to abut said cam edge radially farther and farther from said axis as said latch unit and said strike unit move relative to each other toward a position with said strike opening and said latch opening substantially in confronting relationship.

5. A pivoted blade lock device comprising a strike unit including a substantially planar upright plate having a strike opening therein and having a side remote from said opening and defining cam edge with an active portion inclined to the vertical, and a latch unit including a blade receivable in said strike opening and mounted to pivot about a substantially horizontal axis and having an edge extending substantially radially of said axis and having different portions thereof engaging different portions of said cam edge when said latch unit is moved in the direction of said axis relative to said strike unit.

6. A pivoted blade lock device comprising a strike unit adapted to be mounted in an upright door frame, said strike unit includin" a strike plate having an opening therein and having a side extension in substantially horizontal alignment with said opening and comprising a latch unit adapted to be mounted in a door hinged to said door frame for movement substantially in a horizontal direction, said latch unit including a vertically disposed blade of substantially the same vertical extent as said opening, means 2" r mour. ng said blade near the upper end thereof to pivot on said latch unit about a horizontal axis in substantial alignment with the upper part of said opening whereby said blade can swing into and out of said opening, abutting means on said blade and on said extension of said strike plate including a radial edge on said blade and a marginal edge on said strike plate having contours to engage each other with progressive points of contact as said blade moves over said strike plate to swing said blade about said horizontal axis and in a vertical plane as said door and said door frame move relative to each other substantially in a horizontal direction.

7. A pivoted blade lock device as in claim 6 and including means confined to reciprocation in said latch unit and engaging said blade for swinging said blade about said axis.

References Cited UNITED STATES PATENTS 111,995 2/1871 Vvarren 292-224 429,948 6/1890 Page 292-224 452,777 5/1891 Eckert 292-225 464,478 12/1891 Matthews 292-223 X 478,917 7/1892 Candee. 1,526,164 2/1925 McCune 292-224 X 1,708,444 5/1929 Hampton 292-224 2,062,073 11/1936 Tendler 292-223 X 2,534,693 12/1950 Adams 292-223 2,942,906 6/ 1960 Gilpatrick 292-224 RICHARD E. MOORE, Primary Examiner.

Claims

1. A PIVOTED BLADE LOCK DEVICE COMPRISING A STRIKE UNIT AND A LATCH UNIT HAVING TWO VERTICAL FACES ADAPTED TO MOVE SUBSTANTIALLY INTO AND OUT OF CONFRONTING RELATIONSHIP BY MOTION RELATIVE TO EACH OTHER IN A PREDETERMINED SUBSTANTIALLY HORIZONTAL DIRECTION PARALLEL TO SAID FACES, SAID STRIKE UNIT HAVING A PLATE DEFINING ONE OF SAID VERTICAL FACES AND HAVING A STRIKE OPENING THEREIN, MEANS ON SAID PLATE HORIZONTALLY ALIGNED WITH SAID STRIKE OPENING AND DEFINING A FIRST CAM EDGE THE ACTIVE PORTION OF WHICH HAS A SLOPE INCLINED TOWARD SAID STRIKE OPENING; AND SAID LATCH UNIT HAVING A PLATE DEFINING THE OTHER OF SAID VERTICAL FACES AND HAVING A LATCH OPENING THEREIN ADAPTED TO CONFRONT SAID STRIKE OPENING, A VERTICALLY DISPOSED BLADE, AND MEANS FOR MOUNTING SAID BLADE ON SAID LATCH UNIT FOR SWINGING MOVEMENT THROUGH SAID LATCH OPENING ABOUT A PIVOTAL AXIS ADJACENT ONE END OF SAID LATCH OPENING AND EXTENDING IN SAID PREDETERMINED HORIZONTAL DIRECTION WHEN SAID FACES ARE IN SAID CONFRONTING RELATIONSDHIP, SAID BLADE HAVING A SECOND CAM EDGE ADAPTED TO ABUT SAID FIRST CAM EDGE.