Vehicle seat backrest arrangement

Abstract

A vehicle seat back assembly (10) comprising: a first core (34) of a seat back mechanism mounted on a support (30); a second core (34) of a seat back mechanism mounted on another support (32); and a cross member (14) connected to the first and second cores (34) and transmitting torque from the first core (34) of the seat back mechanism to move the second core (34) of the seat back mechanism with the first core (34) of the seat back mechanism between a secured state and an unsecured state, wherein the cross member (14) has a central part (78) and a plurality of projections (80) extending radially around and away from the central part (78) such that the plurality of projections (80) are spaced apart from one another, wherein: the cross member (14) comprises a first section (74) and a second section (76) adjacent to the first section (74),The first section (74) has a first cross-sectional shape that differs from a second cross-sectional shape of the second section (76). The first cross-sectional shape of the first section (74) has an X-shaped form, and the central part (78) and the multitude of projections (80) are formed in one piece and work together to define the first section (74).

Description

TECHNICAL FIELDThe present disclosure relates to vehicle seat back assemblies, and more particularly to cross members for a seat back mechanism.BACKGROUNDThis section provides background information related to the present disclosure, which is not necessarily prior art.Vehicle seat arrangements, as described for example in U.S. Pat. No. 2017 / 0021743 A1, DE 10 2011 075 364 A1 and DE 20 20 2018 105 268 U1, typically comprise a seat back arrangement which allows selective adaptations of the angular position of a backrest relative to a seat lower part to be carried out. Such seat back assemblies may include a pair of seat back mechanisms disposed at opposite ends of a base of a seat back for maintaining a torque stiffness of the seat back when the seat back is in a secured position. Because each seat back mechanism maintains the seat back in the secured position, each seat back mechanism must be moved from a secured state to an unsecured state to allow movement of the seat back relative to the seat bottom. Because a single hand lever is often used to release both seat back mechanisms, both seat back mechanisms must be synchronously and simultaneously secured and released.Such synchronization is often achieved using a cross member that extends between two seat back mechanisms and can transfer torque from the release mechanism to the seat back mechanism. Typically, such cross members are rigid metal bars having an axial end with a threaded opening that allows a hand lever to be secured to the cross member by a threaded fastener. Such stable cross members are comparatively expensive to produce. The present disclosure provides an improved cross member while maintaining sufficient performance.This section provides a general summary of the disclosure and is not a complete disclosure of the entire scope and all features.In one embodiment, the present disclosure provides a seat back assembly that includes a first core piece of a seat back mechanism, a second core piece of a seat back mechanism, a hand lever, and a cross member. The first core piece of the seat back mechanism is mounted on a bracket. The second core piece of the seat back mechanism is mounted on another bracket. The hand lever is mounted to the first core piece of the seat back mechanism and is rotatable relative to the brackets to move the first core piece of the seat back mechanism between a secured state and an unsecured state. The cross member is connected to the first and second core pieces of the seat back mechanism and transmits torque from the hand lever to the second core piece of the seat back mechanism to move the second core piece of the seat back mechanism with the first core piece of the seat back mechanism between the secured and unsecured states. The cross member has a central portion and a plurality of protrusions extending radially about and from the central portion such that the plurality of protrusions are spaced apart from one another. The cross member includes a first portion and a second portion that is adjacent to the first portion. The first portion has a first cross-sectional shape that is different from a second cross-sectional shape of the second portion. The first cross-sectional shape of the first portion has an X-shaped shape, and the central part and the plurality of protrusions are integrally formed and cooperate to define the first portion.In some configurations of the seat back assembly of the above paragraph, the second portion has a rectangular cross section.In some configurations of the seat back assembly of one or more of the above paragraphs, the second portion defines a central opening.In some configurations of the seat back assembly of one or more of the above paragraphs, each of the first and second core pieces of the seat back mechanism includes a center having an opening extending therethrough. The center includes a plurality of ribs defining the opening.In some configurations of the seat back assembly of one or more of the above paragraphs, the plurality of protrusions and the plurality of ribs of the center cooperate to rotatably fix the center and the cross member together.In some configurations of the seat back assembly of one or more of the above paragraphs, each of the first and second core pieces of the seat back assembly includes a cam and a plurality of pawls. The cams engage the pawls so that rotation of the cams causes corresponding movement of the pawls into and out of engagement with teeth of a grid plate. The centers are coupled to the cams so that the cams can rotate together with the cross member.In some configurations of the seat back assembly of one or more of the above paragraphs, the cross member has opposing ends. One of the opposite ends has an X-shaped cross section and another of the opposite ends has a rectangular cross section.In some configurations of the seat back assembly of one or more of the above paragraphs, a fastener extends through the hand lever and threadedly engages the other of the opposing ends.In another embodiment, the present disclosure provides a seat back assembly that includes a seat bottom, a seat back, a first core of a seat back mechanism, a second core of a seat back mechanism, a hand lever, and a cross member. The seatback is mounted to the seat bottom and rotatable relative to the seat bottom between a reclined position and an upright position. The first core of the seat back mechanism is mounted to a first lateral side of the seat bottom and the seat back. The second core piece of the seat back mechanism is mounted on a second lateral side of the seat bottom and the seat back. The hand lever is mounted to the first core piece of the seat back mechanism and rotatable relative to the seat bottom to move the first core piece of the seat back mechanism between a secured state and an unsecured state. The cross member is connected to the first and second core pieces of the seat back mechanism and transmits torque from the hand lever to the second core piece of the seat back mechanism to move the second core piece of the seat back mechanism with the first core piece of the seat back mechanism between the secured and unsecured states. The cross member has a central portion and a plurality of protrusions extending radially about and away from the central portion such that the plurality of protrusions are spaced apart from one another. The cross member includes a first portion and a second portion that is adjacent to the first portion. The first portion has a first cross-sectional shape that is different from a second cross-sectional shape of the second portion. The first cross-sectional shape of the first portion has an X-shaped shape, and the central part and the plurality of protrusions are integrally formed and cooperate to define the first portion. The second cross-sectional shape of the second portion has a rectangular shape.In some configurations of the seat back assembly of the above paragraph, the second portion defines a central opening.In some configurations of the seat back assembly of one or more of the above paragraphs, each of the first and second core pieces of the seat back mechanism includes a center having an opening extending therethrough. The center includes a plurality of ribs defining the opening.In some configurations of the seat back assembly of one or more of the above paragraphs, the plurality of protrusions and the plurality of ribs of the center cooperate to rotatably fix the center and the cross member together.In some configurations of the seat back assembly of one or more of the above paragraphs, each of the first and second core pieces of the seat back assembly includes a cam and a plurality of pawls. The cams engage the pawls so that rotation of the cams causes corresponding movement of the pawls into and out of engagement with teeth of a grid plate. The centers are coupled to the cams so that the cams can rotate together with the cross member.In some configurations of the seat back assembly of one or more of the above paragraphs, the cross member has opposing ends. One of the opposite ends has an X-shaped cross section and another of the opposite ends has a rectangular cross section.In some configurations of the seat back assembly of one or more of the above paragraphs, a fastener extends through the hand lever and threadedly engages the other of the opposing ends.Further areas of applicability will be apparent from the description provided herein. The description and specific examples in this summary are for purposes of illustration only and are not intended to limit the scope of the present disclosure.DRAWINGSThe drawings described herein are for illustrative purposes of individual embodiments only and not all possible implementations, and are not intended to limit the scope of the present disclosure. FIG. 1 is a partial perspective view of a vehicle having a seat with a seat back assembly according to the principles of the present disclosure; FIG. 2 is a side view of the seat back assembly of FIG. 1 with the seat in a reclined position; FIG. 3 is a perspective view of the seat back assembly of FIG. 1 ; FIG. 4 is an exploded view of a portion of the seat back assembly of FIG. 1 ; FIG. 5 is a cross-sectional view of a seat back mechanism of the seat back assembly of FIG. 1 in a secured state; FIG. 6 is a close-up view of a portion of the seat back mechanism designated as region 6 in FIG. 5 ; FIG. 7 is another cross-sectional view of the seat back mechanism of the seat back assembly of FIG. 1 in a secured state; FIG. 8 is a close-up view of a portion of the seat back mechanism designated as region 8 in FIG. 7; FIG. 9 is a cross-sectional view of a manufacturing assembly in a first position when a cross member of the seat back assembly is passed therethrough; FIG. 10 is a cross-sectional view of the fabrication assembly in a second position as the cross-member is passed therethrough; FIG. 11 is another cross-sectional view of the fabrication assembly in the second position when the cross-member is passed therethrough; FIG. 12 is a perspective view of the manufactured cross member; and FIG. 13 is a perspective view of the manufacturing assembly manufacturing a plurality of cross members.Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.DETAILED DESCRIPTIONExemplary embodiments will now be described more fully with reference to the accompanying drawings.Example embodiments are provided so that this disclosure will be thorough and will fully convey the scope to those skilled in the art. Numerous specific details are set forth as examples of specific components, devices, and methods to provide a detailed understanding of the embodiments of the present disclosure. One skilled in the art will understand that specific details need not be practiced, that example embodiments may be embodied in various forms, and that nothing is intended to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.The terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. As used herein, the singular forms of "a / an" and "the / s" may also include the plural forms unless the context clearly indicates otherwise. The terms "comprises," "comprising," "comprising," and "possessing" are inclusive and thus specify the presence of the named features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more features, integers, steps, operations, elements, components, and / or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring to be performed in the order discussed or illustrated, unless expressly characterized as the order of performance. It is also to be understood that additional or alternative steps may be employed.When an element or layer is referred to as being "on," "engaged to," "connected to," or "coupled to" another element or layer, it may be directly on, engaged to, connected to, or coupled to the other element or layer, or an intermediate element or layer may be present. In contrast, when an element is referred to as being "directly on," "directly engaged to," "directly connected to," or "directly coupled to" another element or layer, there may be no intervening elements or intervening layers present. Other terms used to describe relationships between elements are to be interpreted in a similar manner (e.g., "between" and "directly between", "adjacent" and "directly adjacent", etc.). As used herein, the term "and / or" is intended to include any and all combinations of one or more of the correspondingly listed terms.Although the terms first, second, third, etc. are used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections are not intended to be limited by these terms. These terms may be used to distinguish only one element, component, region, layer, or portion from another region, layer, or portion. Terms such as "first," "second," and other numerical terms are not intended to imply a sequence or order when used herein unless clearly indicated by the context. Therefore, a first element, component, region, layer, or portion discussed below may also be referred to as a second element, component, layer, or portion without departing from the teachings of the example embodiments.Spatially relative terms such as "inner," "outer," "below," "below," "lower," "above," "above," and the like may be used herein for purposes of description to describe the relationship of one element or feature to another element or feature as shown in the figures. Spatially relative terms may encompass different orientations of the device used, in addition to the orientation depicted in the figures. For example, if a device in the figures is turned over, elements referred to as "beneath" or "beneath" other elements or features would then be disposed "above" the other elements or features. Thus, the example term "below" may include both an orientation above or below. The device may be otherwise oriented (rotated 90 degrees or other orientations) and the spatially relative terms used herein interpreted accordingly.Referring to FIGS. 1-3, a vehicle seat back assembly 10 is provided that may be incorporated into a vehicle seat assembly 18 having a seat back 22 and a seat bottom 24. The seat back 22 and the seat bottom 24 may include a seat back frame 26 and a seat bottom frame 28, respectively. The seat assembly 18 may be positioned in a vehicle 20 as shown in FIG. 1. The vehicle seat back assembly 10 may include a first seat back mechanism 12, a second seat back mechanism 13, a cross member 14, and a hand lever 16 (or release lever).The first and second seat back mechanisms 12, 13 are operable in a secured state that prevents relative rotation between the seat back 22 and the seat bottom 24, and an unsecured state that permits relative rotation between the seat back 22 and the seat bottom 24 between an upright position (FIG. 1 ), a rearward-facing reclined position (FIG. 2 ), and a forward-facing reclined position (not shown). As shown in FIG. 4, the first seat back mechanism 12 includes a first bracket 30, a second bracket 32, a core piece of the seat back mechanism (or securing mechanism) 34, an outer coil spring 46, an inner coil spring 48, and a center 50.As shown in FIGS. 4, 5, and 7, the first bracket 30 includes a generally round main body 37 and a pair of fixing wings 31 extending outward from the main body 37. The main body 37 may include a central opening 35 and an adjuster 42. The mounting wings 31 may include a plurality of openings 33 through which fasteners (not shown) may extend to securely attach the first bracket 30 to the seat bottom frame 28 of the seat assembly 18.As shown in FIG. 4, the second bracket 32 may be generally rectangular and include a plurality of apertures 41 and a central aperture 44 through which the cross member 14 extends. Fasteners (not shown) may extend through the plurality of openings 41 to securely attach the second bracket 32 to the seatback frame 26 of the seat assembly 18.Referring to FIG. 4, the core 34 of the seat back mechanism may be mounted to the first and second brackets 30, 32, and may include a guide plate 38, a grid plate 45, a cam 52, a plurality of pawls 54, a connecting disk 56, a plurality of coil springs 58, a control ring 60, and an encapsulating ring 64. The seat back mechanism core 34 is operable to secure the first seat back mechanism 12 and thereby prevent relative rotation between the seat back 22 and the seat bottom 24, and also to unlock the first seat back mechanism 12 and thereby allow relative rotation between the seat back 22 and the seat bottom 24.The guide plate 38 may be mounted on the first bracket 30. The guide plate 38 may be generally a round, flat disc having a central opening 39 (FIG. 4 ) and a plurality of bosses 43 (FIG. 5 ). Each of the pawls 54 is movably received between respective adjacent hubs 43.As shown in FIG. 4, the grid plate 45 may be generally a round flat disk and may include a central opening 65 and a cylindrical recess 67. The cylindrical recess 67 may include a plurality of teeth 69 (FIG. 5 ) disposed on an inner diameter defining the cylindrical recess 67. The second bracket 32 may be welded and / or otherwise suitably attached to the seat back 22 and the grid plate 45 to attach the grid plate 45 to the seat back 22. The grid plate 45 may be mounted to the guide plate 38 with the cylindrical recess 67 disposed substantially concentric with the outer radii of the hubs 43. the encapsulation ring 64 has a U-shaped cross-section and may be generally disposed about the peripheries of the grid plate 45 and the guide plate 38 to rotatably couple the grid plate 45 to the guide plate 38.The plurality of pawls 54 may be radially disposed about the central opening 39 on the guide plate 38 and may be slidably mounted on the guide plate 38 generally between the hubs 43 (FIGS. 5 and 7 ). An edge of each pawl 54 may include a tooth 57 adapted to engage with the teeth 69 of the grid plate 45.The cam 52 may be generally a round disk including an opening 59 and a plurality of radial latch protrusions 61 disposed about the opening 59. The cam 52 is rotatable relative to the pawls 54 and the grid plate 45 such that the latch protrusions 61 can selectively engage the latches 72 of the pawls 54 to move the pawls 54 out of engagement with the teeth 69 of the grid plate 45 (i.e., an unlocked state).The connecting disk 56 engages the cam 52 and the center 50. As shown in FIG. 4, the bonding disk 56 may include a disk portion 88 and an extrusion 90 extending orthogonally from the disk portion 88. The disc portion 88 may have a plurality of flanges 92 extending therefrom. Each flange 92 engages a corresponding one of the coil springs 58. As each flange 92 engages the corresponding coil spring 58, the connecting washer 56 rotationally biases the cam 52 in a manner that causes the locking protrusions 61 to urge the pawls 54 radially outward to the secured state with the teeth 57 of the pawls 54 engaging the teeth 69 of the grid plate 45.The extrusion 90 of the connecting disk 56 engages the center point 50 and the cam 52 such that rotation of the center point 50 (caused by rotation of the hand lever 16) causes rotation of the cam 52 to radially engage and move the pawls 54 out of engagement with the teeth 69 of the grid plate 45.The outer coil spring 46 may exert a torsional force urging the first seat back mechanism 12 against the secured state. The outer coil spring 46 may wrap around the center 50 and engage the first bracket 30 and the hand lever 16. The inner coil spring 48 may extend along the cross member 14 and may engage the first and second brackets 30, 32 to rotatably urge the seatback 22 to the upright position relative to the seat bottom 24.The center point 50 may extend through the length of the seat back mechanism core 34 and may include a first end 70 and a second end 71. The first end 70 can engage with the hand lever 16 such that the center point 50 and the hand lever 16 are rotationally fixed to one another. A fastener 36 (e.g., a screw; shown in FIGS. 2-4 ) may extend through the hand lever 16 and threadedly engage the cross member 14. The center point 50 may include a rectangular shaped opening 73 (FIGS. 5-8 ) that receives the cross member 14. The cross-sectional shape of the opening 73 generally corresponds to the cross-sectional shape of a portion of the cross member 14 such that the cross member 14 and the center 50 are rotatably fixed relative to each other. To allow the seat back 22 to pivot relative to the seat bottom 24, a user may pivot the hand lever 16 clockwise (relative to the view shown in FIG. 5 ) while rotating the center point 50 (and thus the cross-member 14). Accordingly, clockwise rotation of the cross member 14 causes the cam 52 to simultaneously rotate clockwise relative to the plurality of pawls 54, overcoming a counterclockwise rotational bias of the outer coil spring 46.The structure and function of the second seat back mechanism 13 may be similar or identical to that of the first seat back mechanism 12, and therefore will not be described in detail again.Referring to FIGS. 3-8, a cross member 14 may extend in a lateral direction of the vehicle and may connect the first seat back mechanism 12 to the second seat back mechanism 13. In this manner, the cross member 14 may transmit rotational movement of the first seat back mechanism 12 to the second seat back mechanism 13 to move the second seat back mechanism 13 between the secured and unsecured states simultaneously with movement of the first seat back mechanism 12 between the secured and unsecured states.As shown in FIGS. 4 and 12, the cross member 14 may have a first portion 74 having an X-shaped cross section and a second portion 76 having a rectangular-shaped cross section that is adjacent the first portion 74. As shown in FIG. 8, the first portion 74 may have an X-shaped cross-section and may include a central portion 78 and a plurality of protrusions 80. The plurality of protrusions 80 may extend radially about and away from the central portion 78 such that the protrusions 80 are spaced apart from each other. As shown in FIG. 6, the second portion 76 may have a rectangular cross-sectional shape and may include a central opening 83. In some configurations, the central aperture 82 may include a thread to engage the thread with a fastener 36.As shown in FIG. 8, the center point 50 may include a plurality of walls 84 defining the rectangular opening 73 that receives the cross member 14. Each wall 84 may have a plurality of ribs 91 extending inwardly from the wall 84 toward the center of the opening 73. The ribs 91 may also extend from the wall 84 at or near the opposite ends of the wall 84. When the cross member 14 is connected to the seat back mechanisms 12, 13, ends of each of the protrusions 80 may be in contact with two ribs 91 of adjacent walls 84 such that the cross member 14 and the center 50 are rotatably fixed relative to each other. As shown in FIGS. 5 and 6, the shape of the opening 73 generally corresponds to the shape of the second portion 76 of the cross member 14 such that the cross member 14 and the center 50 are further rotatably fixed relative to each other. In other words, the ribs 91 may contact sides of the second portion 76 such that the cross member 14 and the center 50 are rotatably fixed relative to each other.As shown in FIGS. 2 and 3, the hand lever 16 may include a center portion 87 and a handle portion 89. The center portion 87 may include a recess 86. The recess 86 may include an opening 94 (FIG. 4 ) through which a fastener 36 extends. The handle portion 89 may extend outwardly from the center portion 87 and may be shaped to provide a comfortable grip surface that a user can grip to actuate the hand lever 16. The hand lever 16 may be securely attached to the first end 70 of the center point 50 such that rotational movement of the hand lever 16 causes the center point 50 (and therefore also the cross-member 14) to rotate. This rotational movement may cause the seat back mechanism 12, 13 to be secured or unlocked to correspondingly prevent or enable rotational movement of the seat back 22 relative to the seat bottom 24.With further reference to FIGS. 1-13, a method of manufacturing the cross member 14 will now be described in detail. The cross member 14 may be cast or machined as a single stable elongate member. Thereafter, as shown in FIGS. 9-11, the cross-member 14 is guided by a manufacturing assembly 96 (i.e., moved by the manufacturing assembly 96 in a direction along the longitudinal axis of the cross-member 14) that includes a first set of opposing tools 98 and a second set of opposing tools 100. Each tool 98 of the first set of opposing tools 98 includes a triangular-shaped cutting head 102. Similarly, each tool 100 of the second set of opposing tools 100 includes a triangular-shaped cutting head 104. In some configurations, the cutting heads 102 and the cutting heads 104 may have a different shape (e.g., square). In some configurations, the cutting heads 102 and the cutting heads 104 may be, for example, a milling tool or an impact milling tool.As the cross-member 14 is guided by the manufacturing assembly 96, the first and second sets of opposing tools 98, 100 move between first positions (i.e., they move orthogonally to the longitudinal axis of the cross-member 14 and into engagement with the cross-member 14 (FIG. 10 )) for a predetermined amount of time and second positions (i.e., they move orthogonally to the longitudinal axis of the cross-member 14 and out of engagement with the cross-member 14 (FIGS. 9 and 11 )) for a predetermined amount of time. It will be understood that the first set of opposing tools 98 moves between the first and second positions via a controller (not shown) and one or more actuators (e.g., hydraulic or electromechanical actuators), and the second set of opposing tools 100 moves between the first and second positions via a controller (not shown) and one or more actuators. In some configurations, the first and second sets of opposing tools 98, 100 move between the first and second positions using a single controller.As the first and second sets of opposing tools 98, 100 move to the first position, the cutting heads 102 of the first set of opposing tools 98 and the cutting heads 104 of the second set of opposing tools 100 form V-shaped cuts 106 (FIGS. 10 and 11 ) in the cross-member 14, thereby producing the first portion 74 of the cross-member 14 (i.e., the central portion 78 and the plurality of protrusions 80). When the first and second sets of opposing tools 98, 100 are moved to the second position, the rectangular second portion 76 of the cross member 14 is formed. In some configurations, the first and second sets of opposing tools 98, 100 may further engage the cross-member 14 when in the second position to form the second portion 76.As shown in FIG. 12, after the cross member 14 has been passed through the manufacturing assembly 96, the central opening 82 is formed in the second portion 76 of the cross member 14. In some configurations, the central aperture 82 may be threaded.It should be understood that the fabrication assembly 96 can be used to fabricate a plurality of cross beams 14 from a single, stable elongated member. That is, the single stable elongated member may be passed through the manufacturing assembly 96 where the first and second sets of opposing tools 98, 100 are repeatedly moved between the first and second positions. In this manner, as shown in Fig. 13, a plurality of cross beams 14, 14', 14" are made of the single stable elongated member. The plurality of cross members 14, 14', 14" may be separated from each other before each cross member 14, 14', 14" is formed into the central opening in the second portion 76. For example, FIG. 13 shows a section line 110 between the cross members 14', 14". It should be understood that in some configurations, each of the cross members 14 has an X-shaped cross-section along the entire length, other than having only a portion thereof with an X-shaped cross-section.The X-shaped first portion 74 of the cross member 14 described herein causes the cross member to have a lower weight (i.e., by removing material from the cross member 14) than a conventional stable cross member with drilled-in holes at the ends, while maintaining sufficient strength and rigidity. Moreover, the X-shaped portion 74 of the cross member 14 and the seat back mechanisms 12, 13 of the vehicle seat back assembly 10 may be rotatably fixed relative to each other. Moreover, manufacturing cross-members 14 according to the processes described herein makes cross-members 14 significantly more inexpensive to manufacture, reducing the cost of the cross-members for consumers.The foregoing description of the embodiments is illustrative and illustrative. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but are interchangeable where appropriate and may be used in a selected embodiment, although not specifically shown or described. The same can also be varied in various ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Claims

A vehicle seat back assembly (10) comprising: a first seat back mechanism core (34) mounted on a bracket (30); a second seat back mechanism core (34) mounted on another bracket (32); and a cross member (14) connected to the first and second core pieces (34) and transmitting torque from the first seat back mechanism core piece (34) for moving the second seat back mechanism core piece (34) with the first seat back mechanism core piece (34) between a secured state and an unsecured state, wherein the cross member (14) has a central portion (78) and a plurality of protrusions (80) extending radially about and away from the central portion (78) such that the plurality of protrusions (80) are spaced apart from one another, wherein: the cross member (14) includes a first portion (74) and a second portion (76) adjacent the first portion (74), the first portion (74) has a first cross-sectional shape different from a second cross-sectional shape of the second portion (76), the first cross-sectional shape of the first portion (74) has an X-shaped shape, and the central portion (78) and the plurality of protrusions (80) are integrally formed and cooperate to define the first portion (74).The vehicle seat back assembly of claim 1, wherein the cross-sectional shape of the second portion (76) has a rectangular cross-section.The vehicle seat back assembly of claim 2, wherein the second portion (76) defines a central opening (35).The vehicle seat back assembly of claim 1, wherein each of the first and second core pieces (34) of the seat back mechanism comprises a center having an opening extending therethrough, the center comprising a plurality of ribs (91) defining the opening.The vehicle seat back assembly of claim 4, wherein the plurality of protrusions (80) and the plurality of ribs (91) of the center cooperate to rotatably fix the center and the cross member (14) to each other.The vehicle seat back assembly of claim 5, wherein each of the first and second core pieces (34) of the seat back mechanism comprises a cam (52) and a plurality of pawls (54), the cams (52) engaging the pawls (54) such that rotation of the cams (52) causes corresponding movement of the pawls (54) into and out of engagement with teeth of a grid plate (45), the centers coupled to the cams (52) such that the cams (52) rotate together with the cross member (14).The vehicle seat back assembly of claim 1, wherein the cross member (14) has opposing ends, one of the opposing ends having an X-shaped cross-section, and another of the opposing ends having a rectangular cross-section.A vehicle seat back assembly comprising: a seat bottom; a seat back mounted on the seat bottom and rotatable relative to the seat bottom between a reclined position and an upright position; a first core piece (34) of a seat back mechanism mounted on a first lateral side of the seat bottom and the seat back; a second core piece (34) of the seat back mechanism mounted on a second lateral side of the seat bottom and the seat back; and a cross member (14) connected to the first and second core pieces (34) of the seat back mechanism and transmitting torque from the first core piece (34) of the seat back mechanism to the second core piece (34) of the seat back mechanism for moving the second core piece (34) of the seat back mechanism with the first core piece (34) of the seat back mechanism between a secured state and an unsecured state, wherein the cross member (14) has a central portion (78) and a plurality of protrusions (80) extending radially outward from the central portion (78) and disposed about the central portion (78) such that the plurality of protrusions (80) are spaced apart from one another, wherein: the cross member (14) includes a first portion (74) and a second portion (76) adjacent the first portion (74), the first portion (74) has a first cross-sectional shape different from a second cross-sectional shape of the second portion (76), the first cross-sectional shape of the first portion (74) has an X-shaped shape, the central portion (78), and the plurality of protrusions (80) are integrally formed and cooperate to define the first portion (74), and the second cross-sectional shape of the second portion (76) has a rectangular shape.The vehicle seat back assembly of claim 8, wherein the second portion (76) defines a central opening (35).The vehicle seat back assembly of claim 8, wherein each of the first and second core pieces (34) of the seat back mechanism comprises a center having an opening extending therethrough, the center comprising a plurality of ribs (91) defining the opening.The vehicle seat back assembly of claim 10, wherein the plurality of protrusions (80) and the plurality of ribs (91) of the center cooperate to rotatably fix the center and the cross member (14) to each other.The vehicle seat back assembly of claim 11, wherein each of the first and second core pieces (34) of the seat back mechanism comprises a cam (52) and a plurality of pawls (54), the cams (52) engaging the pawls (54) such that rotation of the cams (52) causes corresponding movement of the pawls (54) into and out of engagement with teeth of a grid plate (45), the centers coupled to the cams (52) such that the cams (52) rotate together with the cross member (14).The vehicle seat back assembly of claim 8, wherein the cross member (14) has opposite ends, one of the opposite ends having an X-shaped cross-section, and another of the opposite ends having a rectangular cross-section.

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