GB2076047A - Latch Mechanism of Reclining Seat Assembly - Google Patents

Abstract

A latch mechanism for use in a reclining seat assembly including a seat cushion structure and a tiltable seat back structure, comprising a seat cushion bracket member (12) secured to the seat cushion structure, a seat back bracket member (11) tiltable together with the seat back structure with respect to the seat cushion bracket member (12) and having a toothed portion (14), a locking member (15) having a toothed portion (16) engageable with the toothed portion (14) of the seat back bracket member (15), and an operating lever (17) rotatable about the center axis thereof and having the locking member (15) securely mounted thereon so that the locking member (15) is tiltable about the center axis of the operating lever (17) for engagement with and disengagement from the toothed portion (14) of the seat back bracket member (11). <IMAGE>

Description

SPECIFICATION Latch Mechanism of Reclining Seat Assembly The present invention relates to a reclining seat assembly and, particularly, to a latch mechanism for use in a reclining seat assembly for, a vehicle such as an automotive vehicle.

In accordance with the present invention, there is provided a latch mechanism for use in a reclining seat assembly including a seat cushion structure and a seat back structure, tiltable about a predetermined axis with respect to the seat cushion structure, comprising a seat cushion bracket member secured to the seat cushion structure, a seat back bracket member secured to the seat back structure and pivotally movable about the above mentioned axis with respect to the seat cushion bracket member, the seat back bracket member having a toothed portion, a locking member having a toothed portion engageable with the toothe d portion of the seat back bracket member, and an operating lever rotatable with respect to the seat cushion and seat back bracket members about an axis directed in a predetermined relationship to the aforesaid predetermined axis, the locking member being securely mounted on the operating lever so as to be tiltable about the axis of the operating lever between a first position having the toothed portion thereof held in mesh with the toothed portion of the seat back bracket member and a second position angularly displaced from the first position and having the toothed portion thereof disengaged from the toothed portion of the seat back bracket member. Preferably, the toothed portion of one of the seat back bracket member and the locking member is convexly arcuate and the toothed portion of the other thereof is concavely arcuate.In this instance, it is more preferable that the toothed portion of the seat back bracket member is convexly arcuate about the aforesaid predetermined axis and the toothed portion of the locking member is concavely arcuate in complementary relationship to the convexly arcuate toothed portion of the seat back bracket member.

The locking member in the latch mechanism thus constructed and arranged may be mounted on the operating lever in such a manner that the toothed portion thereof has a center plane lying at the center of the thickness of the toothed portion and offset from the axis of the operating lever. In this instance, the locking member may be configured in such a manner as to have a thickness which is substantially uniform throughout the locking member so that the locking member has a center plane lying at the center of the thickness thereof and offset from the axis of the operating lever. As an alternative, the locking member may be configured so that the toothed portion thereof is smaller in thickness than the remaining portion of the locking member.Otherwise, the locking member of the latch mechanism according to the present invention may be configured in such a manner that the toothed portion thereof is bevelled with respect to the direction of thickness of the toothed portion. In this instance, the toothed portion of the seat back bracket member is also bevelled in the direction of thickness thereof in complementary relationship to the toothed portion of the locking member.

The seat back bracket member may be formed with a depression adjacent to the toothed portion of the bracket member with an edge portion formed between the depression and the toothed portion. The toothed portion of the locking member is slidable on the surface of the depression when the seat back bracket member is being turned about the aforesaid predetermined axis toward a predetermined angular position with respect to the seat cushion bracket member.

The features and advantages of the latch mechanism according to the present invention in connection with a prior-art latch mechanism for a reclining seat assembly will be more clearly appreciated from the following description taken in conjunction with the accompanying drawings in which like reference numerals designate similar or corresponding members and elements and in which:: Fig. 1 is a side elevation view of an example of a prior-art latch mechanism for use in a reclining seat assembly; Fig. 2 is a cross sectional view taken on the line Il-Il in Fig. 1 and shows the prior-art latch mechanism in a certain condition; Fig. 3 is a view similar to Fig. 2 but showing the prior-art latch mechanism in another condition; Fig. 4 is a side elevation view showing a preferred embodiment of the latch mechanism according to the present invention; Fig. 5 is a bottom plan view of the latch mechanism illustrated in Fig. 4 and viewed in directions indicated by arrows V in Fig. 4; Fig. 6 is a vertical sectional view taken on the line VI--VI in Fig. 4; Fig. 7 is an exploded perspective view of the latch mechanism illustrated in Figs. 4 to 6;; Fig. 8 is a view similar to Fig. 6 but showing the latch mechanism in another condition; Fig. 9 is a cross sectional view showing a modification of the combination of the locking member and the operating lever included in the latch mechanism illustrated in Figs. 4 to 8; Fig. 10 is a cross sectional view showing another modification of the combination of the locking member and the operating lever in the latch mechanism shown in Figs. 4 to 8; Fig. 11 is a cross sectional view showing still another modification of the combination of the locking member and the operating lever in the latch mechanism shown in Figs. 4 to 8; Fig. 1 2 is a cross sectional view showing a modification of the combination of the locking member, operating lever and seat back bracket member included in the latch mechanism illustrated in Figs. 4 to 8;; Fig. 1 3 is a fragmentary side elevation view showing a modification of the combination of the seat back bracket member and the locking member included in the latch mechanism illustrated in Figs. 4 to 8; Fig. 14 is a fragmentary sectional view taken on the line XlV-XIV in Fig. 13; and Fig. 1 5 is a fragmentary sectional view taken on line XV-XV in Fig. 14.

For the protection of occupants of, for example, automotive vehicles from injury during collisions of the vehicles, seat assemblies have been widely used which are of the type adapted to hold the occupants restrained thereto when the occupants are on board the vehicles. One of the important requirements of such a seat assembly is an increased degree of structural strength of the seat assembly.

In a reclining seat assembly using a seat back structure which is tiltable on a seat cushion structure, a latch mechanism including two toothed members is provided between the seat back and seat cushion structures. One of the toothed members is secured to the seat back structure and the other of the toothed members is secured to the seat cushion structure. In the case of a reclining seat assembly of this type, the structural strength of the seat assembly largely depends upon the number of the teeth which the two toothed members of the latch mechanism have in mating engagement.

The latch mechanism of a known reclining seat assembly is designed so that one of the toothed members of the mechanism is movable either radially or axially with respect to the other of the toothed members when the toothed members are to be brought into, or out of, engagement with each other. In the case of a latch mechanism using a radially movable toothed member, only a limited number of teeth of the toothed member is allowed to engage the other toothed member and, for this reason, it is difficult to obtain an acceptable degree of structural strength in the seat assembly. A latch mechanism using an axially movable toothed member is free from such a drawback but is not fully acceptable by reason ofthe complexity of construction thereof and the need for skilled techniques in the assemblage of the latch mechanism.Figs. 1 to 3 of the drawings show a representative example of a prior-art latch mechanism of the type using an axially movable toothed member Referring to Fig. 1 , the prior-art latch mechanism comprises a seat back bracket member 1 having a seat back structure (not shown) supported thereon and a seat cushion bracket member 2 having a seat cushion structure (not shown) supported thereon. The seat back bracket member 1 is pivotally mounted on the seat cushion bracket member 2 and has a convexly arcuate toothed portion 1 a. The seat cushion bracket member 2 has a locking member 3 carried thereon by means of two guide pins 4 projecting from the bracket member 2 so that the locking member 3 is laterally movable on the pins 4 toward and away from the bracket member 2 as will be seen from Figs. 2 and 3.The locking member 3 has a concavely arcuate toothed portion 3a conforming in complementary relationship to the toothed portion 1 a of the bracket member 1. A guide bar 5 projects from the locking member 3 and is engaged by an operating lever 6 which has a ramp portion formed with an arcuately elongated slot 7. The guide bar 5 has a leading end portion slidably received in the slot 7 so that, when the operating lever 6 is manually raised as indicated by the arrow in Fig. 1, the ramp portion of the lever 6 is forced to turn through a certain angle and causes the locking member 3 to move laterally away from the bracket member 2 as from the position shown in Fig. 2 to the position shown in Fig. 3.

When the locking member 3 is held in the position shown in Fig. 2, the toothed portion 3a thereof is maintained in mesh with the toothed portion 1 a of the bracket member 1, which is therefore locked in position by the locking member 3. When the locking member 3 is laterally moved from the position illustrated in Fig.

2 to the position illustrated in Fig. 3 as described above, the toothed portion 3a of the locking member 3 is disengaged from the toothed portion 1 a of the bracket member 1. The seat back bracket member 1 is thus made pivotally movable with respect to the locking member 3 and accordingly also to the seat cushion supporting bracket member 2 so that the seat back structure carrying the bracket 1 can be moved into a desired angular position with respect to the seat cushion structure carrying the bracket member 2.

When the operating lever 6 moved into the raised position is released from the manual effort with the seat back structure moved into the desired angular position with respect to the seat cushion structure, the lever 6 is caused to restore to its initial position by means of a return spring 8 urging the lever 6 downward. The toothed portion 3a of the locking member 3 is brought into mesh with the toothed portion 1 a of the seat back bracket member 1 so that the bracket member 1 is for a second time locked to the locking member 3 and accordingly to the seat cushion bracket member 2. The bracket member 1 being thus locked to the bracket member 2, the seat back structure which has been moved into the desired angular position with respect to the seat cushion structure as described above is locked in the particular position by the engagement between the respective toothed portions 1 a and 3a of the bracket member 1 and the locking member 3. In Figs. 2 and 3 of the drawings springs 9 urge the locking member 3 toward the seat cushion bracket member 2.

In the prior-art reclining seat assembly thus constructed and arranged, the locking member 3 is moved toward and away from the seat cushion bracket member 2, viz., in a direction parallel to the axis of pivotal motion of the seat back bracket member 1 when the locking member 3 is to be brought into, and out of, engagement with the bracket member 1. The locking member 3 being thus arranged to be axially movable with respect to the bracket member 1, the bracket member 1 and the locking member 3 can be designed so that the respective toothed portions 1 a and 3a thereof engage each other by such large numbers of teeth as will provide a desired structural strength of the seat assembly.

Such an advantage of the prior-art latch mechanism of the described nature is, however, lessened or cancelled by the complexity of construction of the latch mechanism which comprises guide means including the pins 4 for guiding the lateral movement of the locking member 3 and the cam means for transmitting the motion of the operating lever 6 to the locking member 3.

In order, furthermore, to enable the guide pins 4 to correctly guide the lateral movement of the locking member 3 with respect to the toothed portion 1 a of the seat back bracket member 1, highly skilled techniques are required for the assemblage of the pins 4 and the associated members and elements. This results in low production efficiency of the seat assembly using the latch mechanism.

The present invention contemplates the provision of a reclining seat assembly featuring a latch mechanism which has the advantage available in a prior-art latch mechanism of the type hereinbefore described with reference to Figs. 1 to 3 and which is nevertheless free from the drawbacks inherent in such a latch mechanism. It is, accordingly, an object of the present invention to provide a reclining seat assembly featuring a latch mechanism which is acceptable in structural strength, simple in construction and easy for assemblage.

Referring to Figs. 4 to 7 of the drawings, an embodiment of a latch mechanism according to the present invention comprises a seat back bracket member 11 and a seat cushion bracket member 1 2. Though not shown in the drawings, the bracket member 11 is to be secured to the seat back structure of a reclining seat assembly of, for example, an automotive vehicle by fastening means such as screws while the bracket member 1 2 is to be secured to the seat cushion structure of the seat assembly by fastening means such as screws. The bracket members 11 and 12 are thus adapted to have supported thereon the seat back and seat cushion structure, respectively, of the reclining seat assembly. The seat back bracket member 11 has a lower end portion formed with a circular opening 1 1a as will be best seen from Fig. 7.

The latch mechanism embodying the present invention further comprises a trunnion 13 axially projecting from the seat cushion bracket member 12. The trunnion 13 has a stem portion 1 3a axially projecting from one face of the bracket member 11 and a split cotter portion 1 3b axially extending from and smaller in diameter than the stem portion 1 3a. The cotter portion 1 3b has adjacent to its leading end a circumferential groove which consists of a pair of discrete semicircular halves as will be best seen from Fig. 7.

The seat back bracket member 11 is pivotally mounted on the seat cushion bracket member 12 with the steam portion 1 3a of the trunnion 13: slidably received in the opening 11 a in the bracket member 11 and with the split cotter portion 13b of the trunnion 13 axially projecting from the opening 11 a as will be best seen from Fig. 6.

The seat back bracket member 11 has a downwardly protruding, convexly arcuate toothed portion 1 4 having a pitch circle about the center axis of the trunnion 13 rotatable in the opening 11 a in the bracket member 11. The toothed portion 14 of the seat back bracket member 11 is adapted to be brought into and out of engagement with a locking member 1 5 having a downwardly recessed, concavely arcuate toothed portion 1 6 which is toothed to conform to the toothed portion 14. The locking member 1 5 has opposite to the toothed portion 1 6 therefor a flat end face as will be best seen from Fig. 6.

The latch mechanism embodying the present invention further comprises an operating lever 1 7 having a front knob portion 1 8 which is perpendicularly bent from the remaining straight longitudinal portion of the lever 1 7. The straight longitudinal portion of the operating lever 1 7 has a center axis which is directed in a predetermined relationship to the axis of the trunnion 13 and is herein assumed, by way of example, to be directed perpendicularly in non-intersecting relationship to the axis of the trunnion 13. The operating lever 1 7 further has in the neighbourhood of its rear end a flat surface portion on which the locking member 1 5 has its flat end face received.The locking member 1 5 thus carried on the operating lever 1 7 is secured to the lever 1 7 by means of a pair of clamping members 19 having the locking member 1 5 and a portion of the operating lever 17 received therebetween and securely held together by rivets 20 through holes formed in the locking member 1 5. The operating lever 1 7 has a rear end portion axially projecting rearwardly from the locking member 1 5 and the clamping members 19 thus secured to the lever 17.

The locking member 15, the clamping member 19 and the toothed portion 14 of the seat back bracket member 11 are interposed between the seat cushion bracket member 1 2 and a side plate 21 formed with a circular opening 21a. The side plate 21 is secured to the seat cushion bracket member 12 by means of bearing blocks 22 and 22' formed with grooves 23 and 23', respectively, each having a generally U-shaped cross section.

The operating lever 1 7 is slidably received adjacent the front and rear ends of the locking member 1 5 in the grooves 23 and 23' in the bearing blocks 22 and 22', respectively, so as to be rotatable about the center axis thereof with respect to the bearing blocks 22 and 22'. The seat back bracket member 1 2 is fixedly secured to the bearing blocks 22 and 22' by fastening means such as rivets 24 as shown in Fig. 6 while the side plate 21 is fixedly secured to the bearing blocks 22 and 22' by fastening means such as rivets 25 and 25' as shown in Fig. 7.Thus, the bearing blocks 22 and 22' is adapted not only to hold the side plate 21 attached to the seat back bracket member 12 but to have the locking member 15 and accordingly the operating lever 1 7 axially held in position with respect to the seat cushion bracket member 1 2 while allowing the operating lever 1 7 to turn about the center axis thereof with respect to the bracket member 12 and side plate 21. The operating lever 1 7 being thus rotatable about the center axis thereof with respect to the bracket member 12 and the side plate 21, the locking member 1 5 on the lever 17 is tiltable about the center axis of the lever 17 between and with respect to the bracket member 12 and the side plate 21.The stem portion 1 3a of the trunnion 1 3 slightly projects from the side plate 21 through the opening 21a in the side plate 21 and is caulked to the side plate 21 along its circumferential edge adjacent the split cotter portion 13b as indicated at 26 in Fig. 6.

The seat cushion bracket member 12 and the side plate 21 have inward protrusions 27 and 38 protruding toward each other and having the toothed portion 14 of the seat back bracket member 11 slidably interposed therebetween as shown in Fig. 6 so as to prevent the bracket member 11 from being laterally moved or inclined with respect to the seat cushion bracket member 12. The seat cushion bracket member 12 and the sideplate 21 further have outward protrusions 29 and 30 protruding away from each other and having formed therebetween a space for accommodating the tilting motions of the locking member 15 between the bracket member 12 and the side plate 21.

Biasing means is provided to urge the locking member 1 5 to stay, about the center axis of the operating lever 17, at an angular position having the toothed portion 16 engaged by the toothed portion 14 of the seat back bracket member 11.

In Figs. 4, 5 and 7 of the drawings, such biasing means is shown by way of example as comprising a straight-bar torsion spring 31 having front and rear end portions 31 a and 316 which are perpendicularly bent from the remaining straight longitudinal portion of the spring 31. The torsion spring 31 has its front end portion 31 a anchored to the operating lever 17 through a hole 32 formed in a front end portion of the lever 1 7 and its rear end portion 316 anchored to the side plate 21 through a hole 33 formed in the side plate 21 as will be best seen from Fig. 7.If desired, the straight-bar torsion spring 31 thus arranged may be substituted by a cylindrical coiled torsion spring (not shown) which is arranged to have the operating lever 1 7 axially passed therethrough and which is anchored at one end thereof to the operating lever 1 7 through, for example, the hole 32 and at the other end thereof to the side plate 21 through, for example, the hole 33.

The latch mechanism embodying the present invention further comprises biasing means for urging the seat back structure to tilt forwardly about the center axis of the trunnion 1 3. In Fig. 7 of the drawings, such biasing means is shown by way of example as comprising a spiral coiled spring 34 having a hooked inner end portion 34a and a hooked outer end portion 34!;. The hooked inner end portion 34a of the spring 34 is received in the gap in the split cotter portion 13b of the trunnion 13 while the hooked outer end portion 34b of the spring 34 is anchored to an anchor element 35 secured to the seat back bracket member 11 by fastening means such as rivet 36 as shown.The spiral coiled spring 34 thus mounted on the split cotter portion 1 36 of the trunnion 13 is axially held in position on the cotter portion 13b by means of a snap ring 37 which is received in the previously mentioned circumferential groove formed in the cotter portion 13b as will be best seen from Fig. 6 in which the spring 34 is indicated by phantom lines.

When, now, the operating lever 1 7 is kept released from a manipulative effort, the lever 1 7 is maintained by the force of the torsion spring 31 in an angular position having the locking member 1 5 held in a first angular position in which the toothed portion 1 6 thereof is engaged by the toothed portion 14 of the seat back bracket member 11. The toothed portion 14 of the bracket member 11 being thus held in mesh with th toothed portion 16 of the locking member 15, the bracket member 11 and accordingly the seat back structure (not shown) are locked in certain angular positions about the center axis of the trunnion 13 with respect to the seat cushion bracket member 12 and accordingly to the seat cushion structure (not shown).

When the occupant of the seat assembly having the seat back structure held in such an angular position with respect to the seat cushion structure desires to vary the angular position of the seat back structure, the seat occupant manipulates the operating lever 1 7 at the knob portion 18 so as to turn the lever 17 about the center axis thereof in a direction indicated by arrow a in Fig. 6 against the force of the torsion spring 31.The operating lever 17 is thus caused to turn in the grooves 23 and 23' in the bearing blocks 22 and 22', respectively, and causes the locking member 1 5 to tilt about the center axis of the lever 1 7. As the locking member 1 5 is caused to tilt about the center axis of the operating lever 17, each of the teeth of the toothed portion 16eof the locking member 1 5 is moved in an arc about the center axis of the lever 17. When the operating lever 1 7 is turned through a certain angle about the center axis thereof, the locking member 1 5 reaches a second angular position about the center axis of the lever 1 7 so that the toothed portion 16 of the locking member 1 5 is disengaged from the toothed portion 14 of the seat back bracket member 11 as shown in Fig. 8 of the drawings. Being disengaged from the locking member 15, the seat back bracket member 11 is allowed to turn about the center axis of the trunnion 13 and is forced to tilt forwardly together with the seat back structure by the force of the spring 34.The seat back structure carrying the seat back bracket member 11 can now be moved by human intervention into a desired angular position about the center axis of the trunnion 13 with respect to the seat cushion structure carrying the seat cushion bracket member 12. The seat back structure can be maintained in the particular pqsition simply by releasing the operating lever 1 7 from the manual effort which has been applied to the knob 1 8 thereof. When the operating lever 1 7 is thus released from the manual effort, the operating lever 17 is forced to turn in the. reverse direction about the center axis thereof as indicated by arrow b in Fig. 8 by the force of the torsion spring 31.As the operating lever 1 7 is thus caused to turn with respect to the seat cushion bracket member 12, the locking member 1 5 is turned back from the second angular position toward the initial first angular position thereof about the center axis of the lever 1 7 with each of the teeth of the toothed portion 16 thereof moved in an arc toward the toothed portion 14 of the seat back bracket member 11. The toothed portion 1 6 of the locking member 1 5 is in this manner ultimately brought into mesh with the toothed portion 14 of the seat back bracket member 11 as illustrated in Fiat 6.

Figs. 9, 10, 11 and 12 of the drawings show modifications of the locking member 1 5 included in the hereinbefore described embodiment of the latch mechanism according to the present invention.

For eliminating loose connection between the seat back and seat cushion structures of a .reclining seat assembly, it is important to reduce to a minimum the tolerance between the locking member and the seat back bracket member of the latch mechanism. In a latch mechanism of the type in which the locking member is to be turned laterally or sidewise with respect to the seat back bracket member, the reduced tolerance between the locking member and the seat back bracket member tends to impair the smoothness in the sliding movement of the toothed portion of the locking member on the toothed portion of the bracket member when the locking member is to be brought into, or out of, the bracket member.In the worst case, the locking member once disengaged from the seat back bracket member would be disabled from being brought into reengagement with the bracket member due to the tight tolerance therebetween. The modified locking members shown in Figs. 9 to 12 of the drawings are adapted to provide seful solutions to such a problem. More specifically, each of the locking members shown in Figs. 9 to 12 is adapted to preclude an occurrence of interference which may be caused between the teeth of the toothed portion of the locking member and the teeth of the toothed portion of the seat back bracket member in a latch mechanism of the type in which the locking member is movable laterally of the seat back bracket member.

In Fig. 9 of the drawings, the locking member 1 5 is shown mounted on the flat surface portion of the operating lever 17 in such a manner as to be slightly offset from the center axis 0 of the lever 17, the center axis 0 being the axis of pivotal movement of the locking member 1 5. The locking member 1 5 is further shown having a rectangular cross section and accordingly flat, parallel side faces across the thickness h of the cross section.

In Fig. 9, furthermore, one of the teeth of the toothed portion 1 6 of the locking member 1 5 is shown having side ends at L and R. The side end L is located ctosr to the toothed portion 14 of the seat back bracket member 11 than the side end R when the locking member 15 is being pivotally moved about the center axis 0 of the operating lever 1 7 in a direction Ga in which the locking member 1 5 is to be disengaged from the bracket member 11 or in a direction Qb in which the locking member 15 is to be brought into engagement with the bracket member 11. The radius of pivotal movement of the locking member 1 5 about the center axis 0 of the operating lever 1 7 is represented by r.The locking member 1 5 shown in Fig. 9 is further assumed to have a center plane P which lies at the center of the thickness h of the locking member 1 5 throughout the extent of the locking member 15, viz., at equal distances from the flat, parallel side faces of the locking member 1 5.

The degree of interference that would occur between the toothed portion 16 of the locking member 15 and the toothed member 14 of the seat back bracket member 11 is not affected by the length OR but depends upon the length OL. In this regard, it has been ascertained by the inventors that the interference between the toothed portion 16 of the locking member 15 and the toothed portion 14 of the bracket member 11 is brought about when the length OL becomes larger by a certain value than the radius th2r of the pivotal movement of the locking member 1 5.

This is because of the fact that tip portions of the teeth of the toothed portion 1 6 of the locking member 15 are allowed to clear the teeth of the toothed portion 14 of the bracket member 11 through the gaps between the teeth of the toothed portion 14 but flank portions of the teeth of the toothed portion 16 are not allowed to clear the teeth of the toothed portion 14 so that interference takes place on the flank portions of the teeth of the toothed portion 14. The fact that the length OL is larger than the radius r by a certain value i (which is given by the difference OL-r) is tantamount to the fact that the locking member 1 5 is moved the distance itoward the seat back bracket member 11.

If, thus, the locking member 1 5 is mounted on the operating lever 1 7 in such a manner that the center plane P of the locking member 1 5 is offset a predetermined distance s from the axis 0 of pivotal movement of the locking member 15 as shown in Fig. 9, then the above mentioned distance iis given by

If, thus, the distance s of offset is selected to be less than the thickness h of the locking member 15, the distance I is smaller than the constant value

so that an occurrence of interference between the toothed portions 14 and 16 can be lessened to a degree dictated by the value of the distance s of offset.If, particularly, the, distance s of offset is selected to be equal to the value of h/2, then the distance i becomes zero so that an occurrence of interference between the toothed portions 14 and 1 6 can be completely avoided.

In the arrangement of the locking member 15 illustrated in Fig. 9, a relationship is constantly established in which the length OL is smaller than the length OR. For this reason, the teeth of the toothed portion 16 of the locking member 15 are moved out of, or into, wider portions of the gaps between the teeth of the toothed portion 14 of the seat back bracket member 11 when the locking member 15 is turned for disengagement from, or engagement with, the bracket member 11 in the direction of the arrow Qa or Qb, respectively. Thus, the locking member 15 can be smoothly disengaged from, and engaged by, the seat back bracket member 11 without causing interference between the respective toothed portions 14 and 16 of the bracket and locking members 11 and 15.

The latch mechanism using the locking member 1 5 arranged as illustrated in Fig. 9 is preferably designed in such a manner that the locking member 1 5 is tiltable through a sufficiently large degree about the center axis 0 o the operating lever 1 7 between the seat cushion bracket member 12 and the side plate 21. When the latch mechanism is designed in this fashion, a large number of teeth of the toothed portion 16 of the locking member 1 5 are permitted to engage the toothed portion 14 of the seat back bracket member 11 when the locking member 1 5 is held in engagement with the bracket member 11 so that the seat back structure of the reclining seat assembly is firmly locked to the seat cushion structure of the seat assembly.

The locking member 1 5 shown in Fig. 9 is characterized in that the locking member 1 5 is in its entirety uniform in thickness and that the center plane P of the locking member 15 as a whole is offset from the center axis of the operating lever 17 supporting the locking member 1 5. In contrast to the locking member 1 5 thus configured and arranged, each of the locking members illustrated in Figs. 10 and 11 is configured in such a manner that the toothed portion 1 6 thereof is smaller in thickness than the remaining portion of the locking member 1 5 and is mounted on the flat surface portion of the operating lever 1 7 in such a manner that the center plane Pt of the toothed portion 1 6 of the locking member 1 5 is offset a predetermined distance s' from the center axis 0 of the operating lever 1 7. The term "center plane" herein referred to in connection with the toothed portion 1 6 of the locking lever 1 7 is essentially similar to that previously referred to in respect of the locking member 1 5 and thus lies at the center of the thickness of the toothed portion 16.In the locking member 1 5 illustrated in Fig. 10, the toothed portion 1 6 is reduced in thickness from the remaining portion of the locking member 15 through an internally stepped wall surface 38. On the other hand, the toothed portion 16 of the locking member 1 5 shown in Fig. 11 is gradually reduced in thickness from the remaining portion of the locking member 1 5 through a ramp 38'.

An occurrence of interference between the toothed portions 14 and 16 of the bracket and locking members 11 and 15 can also be precluded by adoption of the combination of the bracket and locking members 11 and 1 5 having the respective gear portions 14 and 1 6 configured as shown in Fig. 12.In the arrangement illustrated in Fig. 12, the toothed portion 14 of the seat back bracket member 11 and the toothed portion 1 6 of the locking member 1 5 are bevelled in complementary relationship to each other with respect to the directions of thickness of the toothed portions 14 and 1 6. More specifically, the toothed portion 16 of the locking member 15 have pitch circles which are different from each other at the opposite side ends of the toothed portion 1 6. Furthermore, the pitch circle which the toothed portion 16 has at its side end to be located on the trailing side of the locking member 1 5 being turned in the direction of the arrow Qa for disengagement from the bracket member 11 is smaller in diameter than the pitch circle which the toothed portion 1 6 has at its side end to be located on the trailing side of the locking member being turned in the direction of the arrow Gb for engagement with the bracket member 11. The toothed portion 14 of the seat back bracket member 11 is configured in a complementary relationship to the toothed portion 1 6 thus configured of the locking member 1 5 as indicated by phantom lines in Fig. 12.

In a seat assembly of the reclining type, it is important that the seat back structure be capable of being returned with certainty into a predetermined rest position with respect to the seat cushion structure when the seat back structure once moved into a forwardly tilting position is to be moved into a desired angular position. Figs. 13 to 15 show a preferred example of the seat back bracket member adapted to satisfy such a requirement of a reclining seat assembly.

Referring to Figs. 13 to 15, the seat back bracket member 11 is shown formed with a depression 39 adjacent to the toothed portion 14 of the bracket member 11. The depression 39 is in part defind by an edge portion 40 stepping up from the depression 39 to the toothed portion 14 as will be best seen from Fio. 14. The toothed portion 1 6 of the locking member 1 5 is engageable over one side face thereof with this depression 39 when the bracket member 39 assumes an angular position having the seat back structure held in a forwardly inclined position with respect to the seat cushion structure.The edge portion 40 thus formed between the toothed portion 14 and the depression 39 is located to be engageable with the toothed portion 1 6 of the locking member 1 5 when the bracket member 11 is turned in a direction in which the seat back structure is to be turned from a forwardly inclined position to a predetermined rest position with respect to the seat cushion structure. When the seat cushion structure is thus turned back from the forwardly inclined position, the seat back bracket member 11 is caused to turn about the center axis of the trunnion 13 (Figs. 4 to 8) as indicated by arrow c in Fig. 13 with the toothed portion 16 of the locking member 1 5 held in sliding contact over one side face thereof with the surface of the depression 39.At the point of time when the seat back structure reaches the abovementioned predetermined rest position thereof with respect to the seat cushion structure, the rearmost one of the teeth of the toothed portion 1 6 of the locking member 1 5 is brought into abutting engagement with the edge portion 40 of the bracket member 11 and causes the bracket member 11 to stop in the rest position thereof. The edge portion 40 being formed adjacent the foremost one of the teeth of the toothed portion 14 of the bracket member 11, the toothed portion 14 of the bracket member 11 is enabled to correctly engage the toothed portion 16 of the locking member 1 5 without skipping over any of the teeth of the toothed portion 14 when the bracket member 11 is further turned back beyond the rest position thereof.

In lieu of the formation of the depression 39 in the seat back bracket member 11, a projection may be formed on the bracket by, for example, a pin, plate or block (not shown) projecting from or secured to the bracket member 11 and located similarly to the edge portion 40 of the bracket member 11 shown in Figs. 13 to 15.

While it has been described that the toothed portion 14 of the seat back bracket member 11 is convexly arcuate and the toothed portion 1 6 of the locking member 1 5 is concavely arcuate, the toothed portions 14 and 16 may be configured to be arcuate concavely and convexly, respectively, if desired. Each of the arrangements illustrated in Figs. 9 to 1 2 and the arrangement illustrated in Figs. 13 to 1 5 is appiicable also to a latch mechanism in which the toothed portions 14 and 1 6 of the bracket member 11 and locking member 1 5 are configured to be arcuate concavely and convexly, respectively.

White, furthermore, the toothed portions 11 and 1 6 have been described as forming part of the seat back bracket member 11 and the locking member 15, respectively, these portions may be constructed separately of and securely connected to the members 11 and 16, respectively.

Likewise, the locking member 1 5 which has been assumed to be constructed separately of, and securely attached to, the operating lever 1 7 may be formed as a portion of the lever 17, if desired.

Claims (13)

Claims

1. A latch mechanism for use in a reclining seat assembly including a seat cushion structure and a seat back structure tiltable about a predetermined axis with respect to the seat cushion structure, comprising: a seat cushion bracket member secured to the seat cushion structure, a seat back bracket member secured to the seat back structure and pivotally movable about said predetermined axis with respect to said seat cushion bracket member, the seat back bracket member having a toothed portion, a locking member having a toothed portion engageable with the toothed portion of the seat back bracket member, and an operating lever rotatable about an axis directed in a predetermined relationship to said predetermined axis, the locking member being fast on the operating lever and being tiltable about the axis of the operating lever between a first position having the toothed portion thereof held in mesh with the toothed portion of the seat back bracket member and a second position having the toothed portion thereof disengaged from the toothed portion of the seat back bracket member.

2. A latch mechanism as set forth in claim 1, in which the toothed portion of the locking member has a center plane lying at the center of thickness of the toothed portion and offset from the axis of said operating lever.

3. A latch mechanism as set forth in claim 2, in which said locking member has a center plane lying at the center of thickness of the bracket member and substantially coincident with said center plane of the toothed portion of the locking member.

4. A latch mechanism as set forth in -claim 2, in which the toothed portion of said locking member is smaller in thickness than the remaining portion of the locking member.

5. A latch mechanism as set forth in claim 4, in which the toothed portion of said locking member is reduced in thickness from said remaining portion through a stepped wall surface.

6. A latch mechanism as set forth in claim 4, in which the toothed portion of said locking member is reduced in thickness from said remaining portion through a ramp.

7. A latch mechanism as set forth in claim 1, in which the respective toothed portions of said seat back bracket member and said locking member are bevelled with respect to the directions of thickness of the seat back bracket member and the locking member.

8. A latch mechanism as set forth in any of claim 1 to 7, further comprising biasing means urging said locking member to tilt about the axis of said operating lever toward said first position thereof.

9. A latch mechanism as set forth in any of claims 1 to 7, in which said seat back bracket member is formed with a depression adjacent to the toothed portion of the seat back bracket member with an edge portion formed between the depression and the adjacent toothed portion, the toothed portion of said locking member being slidable on the surface of said depression when the seat back bracket member is being turned about said predetermined axis toward a predetermined angular position with respect to said seat cushion bracket member.

10. A latch mechanism as set forth in claim 9, further comprising biasing means urging said locking member to tilt about said axis of said operating lever toward said first position thereof.

11. A latch mechanism as set forth in any of claims 1 to 7, in which the toothed portion of one of said seat back bracket member and said locking member is convexly arcuate and the other; of the seat back bracket member and the locking member is concavely arcuate.

12. A latch mechanism as set forth in claim 11spa in which the toothed portion of said seat back bracket member is convexly arcuate about said predetermined axis and the toothed portion of said locking member is concavely arcuate in a complementary relationship to the toothed portion of the seat back bracket member.

13. A latch mechanism for use in a reclining seat assembly substantially as described with reference to Figs. 4 to 8, or Figs 4 to 8 as modified by any one of Figs. 9 to 12, or Figs. 4 to 8 as modified by Figs. 13 to 15 of the accompanying drawings.