Walkover seat with inertial latch

A vehicle seat has a seat back mounted for walkover movement from one end of the seat to the other end. Associated with the seat back is an inertial latching system which is normally inoperative so as to allow walkover movement of the seat back. During deceleration of the vehicle above a preselected magnitude, the latching system is actuated to restrain walkover movement of the seat back and to progressively absorb any impact into the seat back from behind, as would occur during a sudden stop or crash. The latching system automatically deactuates itself upon cessation of any tendency by the seat back to undergo walkover movement.

BACKGROUND OF THE INVENTION 
The present invention relates generally to seats for mass transit vehicles 
such as railroad commuter cars and more particularly to walkover seats for 
such vehicles. 
A walkover seat is one in which a seat back may be moved from the front end 
to the rear end of the seat to allow the seat occupant or passenger to 
face whichever direction the occupant desires. It also allows two adjacent 
seats in a row of seats to be arranged so that the occupants of the two 
seats face each other in a group, when the occupants desire such an 
arrangement. A walkover seat allows one to reposition the seat back to 
one's liking, creating forward facing, rearward facing or a group cluster 
of seats. 
A walkover seat employs pivotal linkages between the seat back and the 
frame of the seat to accomplish the walkover movement and employs other 
linkages to change the inclination of the seat cushion in response to 
repositioning of the seat back. Examples of walkover seats employing such 
linkages are shown in Kehl et al U.S. Pat. No. 4,407,542, and in Bilancia 
U.S. Pat. No. 3,265,435, and the disclosures thereof are incorporated 
herein by reference. 
There have been walkover seats which did not employ any provision for 
locking the backrest in either of its two rest positions. In one respect, 
this was advantageous because it allowed the seat back to be repositioned 
at will, without the need to actuate release levers, pedals, linkages or 
switches normally associated with locking mechanisms. This made it very 
convenient for passengers or train personnel to reposition the seat back, 
but it had other drawbacks. 
More particularly, in the case of an abrupt stop, as in the event of a 
vehicle crash, inertia causes a passenger to be thrown forward into the 
seat back in front of that passenger, and a walkover seat back receiving 
the impact of the passenger would, in response to that impact, move from 
the rest position it was in at the time of impact toward the opposite rest 
position of the seat back. A seat back is normally inclined, i.e. the 
angle of the seat back is displaced from true vertical. As a walkover seat 
back moves from one rest position to the other rest position, in response 
to impact by a passenger, the angle of inclination changes from a rearward 
inclination to a frontward inclination. As a result of this change in 
inclination, the seat back acts as a ramp for the passenger who has 
impacted against the seat back and directs the passenger frontwardly and 
upwardly into the overhead structure, e.g. an overhead luggage rack or the 
floor of an upper level of seating in a bi-level car. This increases the 
potential for injury to the passenger. 
One attempt to eliminate the problem described in the preceding paragraph 
was to fix the seat back against walkover movement. This proved to be very 
unpopular with passengers, most of whom preferred to face forward when the 
vehicle was in motion. In addition, it eliminated the flexibility of group 
clusters, which was available with walkover seat backs. 
Another attempt to solve the problem was to provide the walkover seat with 
a locking mechanism which normally locked the seat back against walkover 
movement but which could be unlocked with release handles or pedals, but 
this too had drawbacks. A seat employing the locking mechanism was 
considered to be not user friendly. Passengers unfamiliar with the locking 
system had to hunt for the release handles or pedals. Manually unlocking 
the walkover seat back before moving it from one position to another 
required more complicated efforts on the part of a passenger or train 
personnel, and the need to perform these additional efforts slowed down 
considerably the speed with which train personnel could change the facing 
direction of all the seat backs in an entire car. The release handles or 
pedals, and the associated locking mechanism, were susceptible to damage, 
necessitating maintenance and repair procedures not previously required 
for walkover seats. 
A serious drawback of both fixed seat backs and normally locked walkover 
seat backs was the increased impact load experienced by a passenger who 
impacted against a seat back which did not give or yield when impacted. 
Unlike an unlocked walkover seat back, a fixed seat back or a normally 
locked walkover seat back remained in place when impacted by a passenger 
who, as a result, experienced a greater impact load than did a passenger 
who impacted against an unlocked, walkover seat back. 
An example of a walkover seat employing a locking arrangement with a 
release handle is disclosed in the aforementioned Kehl et al U.S. Pat. No. 
4,407,542. 
SUMMARY OF THE INVENTION 
The present invention provides a walkover seat which eliminates the 
drawbacks and disadvantages of the seats described above. The seat back 
can be moved from one rest position to another rest position without the 
need to operate any release handle or pedal. On the other hand, when the 
seat back is impacted, as in the case of an abrupt stop or crash, 
mechanisms are provided which prevent the seat back from acting as a ramp 
that directs the impacting passenger into the overhead structure. In 
addition, the seat back gives or yields in response to impact, thereby 
decreasing the impact load experienced by an impacting passenger, and 
there is also structure which progressively absorbs the impact load. 
A walkover seat in accordance with the present invention includes a 
latching system comprising a latch element mounted for movement between a 
normal, inactive, non-latching rest position and a latching position. The 
latch element is normally maintained in its non-latching rest position to 
allow walkover movement of the seat back. The latching system is 
automatically activated and comprises structure, responsive to 
deceleration of the vehicle at a preselected magnitude, for moving the 
latch element into its latching position. Deceleration of the vehicle may 
be normal or abnormal. Normal deceleration is a relatively moderate 
deceleration as would occur during normal operation of the vehicle. The 
latching system can be adjusted so that activation occurs at a preselected 
normal deceleration, e.g. 0.3 g ("g" being the force of gravity or 32 
ft./sec..sup.2). A seat back will not usually undergo walkover movement by 
itself at such a relatively moderate deceleration. 
Abnormal deceleration of the vehicle typically occurs when the vehicle 
undergoes an abrupt stop, as in a crash, in which case a passenger seated 
behind a given seat back is usually propelled by inertia into that seat 
back. As a result of abnormal deceleration, a seat back can undergo 
walkover movement due solely to the forward inertia of the seat back 
itself. 
The latching system further comprises structure for maintaining the latch 
element in its latching position for at least as long as the seat back is 
urged to undergo walkover movement, as by abnormal deceleration of the 
vehicle. In addition, the latching system comprises structure for 
automatically returning the latch element to its non-latching, rest 
position upon cessation of the urge by the seat back to undergo walkover 
movement, although when the latching system has been adjusted to activate 
at a normal deceleration, the latch element will not return to its rest 
position until there has also been a decrease in deceleration to a 
magnitude below the activation level. The structure which moves the latch 
element into its latching position and which automatically returns the 
latch element to its rest position includes a pendulum arrangement, and 
the pendulum arrangement can be adjusted to change the magnitude of 
vehicle deceleration at which the latching system is automatically 
activated. 
The latching system also includes dampening structure actuable in response 
to movement of the latch element to its latching position for absorbing 
the impact against the seat back occurring as a result of abnormal 
decleration and for progressively opposing walkover movement of the seat 
back. The dampening structure is typically in the form of a torsion member 
the effective length of which can be preset to vary the give or yield 
which occurs when a passenger impacts against the seat back. The dampening 
structure gradually absorbs the impact of the passenger against the seat 
back, rather than simply resisting it. 
Because the latching mechanism initially resists and then gradually absorbs 
passenger impact into the seat back, there is no ramping affect as would 
otherwise result from a combination of the forward inclination of the seat 
back and the forward inertia of the passenger which combine to propel the 
passenger into the overhead structure. As a result, the potential for 
injury to the passenger is substantially decreased. 
The latching system is automatically activated only when the vehicle 
undergoes decleration, and as noted above, the magnitude of the 
deceleration at which activation occurs depends upon the adjustment of the 
pendulum arrangement. At all other times, the walkover seat may be freely 
moved between its two normal rest positions, respectively at the front end 
and the rear end of the seat, without the need to manipulate a release 
handle or pedal or the need to engage in any type of latch deactuating 
activity. Because the latching system is operated relatively seldom and 
because there are no actuating handles or pedals requiring operation by a 
passenger, the need for repairs or maintenance of the latching system is 
essentially eliminated. 
The entire latching mechanism is housed in a pocket located adjacent one 
side of the seat and is relatively inaccessible to a passenger. Because of 
this, there is no potential for injury to the passenger as might occur if 
the passenger were to come into contact with any part of the latching 
mechanism.

DETAILED DESCRIPTION 
Referring initially to FIG. 1, indicated generally at 10 is a walkover seat 
comprising a seat cushion 11 and a seat back 12 mounted for walkover 
movement between a pair of rest positions each located adjacent one of a 
pair of opposed seat ends 13, 14 respectively. 
Seat 10 comprises a pair of pedestals 18, 19 supporting a pair of tubular 
cross members 20, 21 in turn supporting a pair of side frame plates 22, 23 
each constituting part of a respective seat side also including a tubular 
frame member 24, 25 the tops of which define the respective arm rests on 
each side of the seat. 
Pivotally mounted between side plates 22, 23 are a pair of rotatable shafts 
28, 29. Fixed at each opposite end of each rotatable shaft 28, 29 is the 
lower end of a respective link member 30, 31 the upper ends of each of 
which are pivotally connected to a link element 32 in turn attached to the 
bottom of a vertically disposed portion 33 of a back frame for seat back 
12. 
There is a linkage composed of link members 30, 31 and link element 32 
located adjacent each side plate 22, 23 of seat 10. These linkages, 
together with rotatable shafts 28, 29 constitute the structure which 
mounts seat back 12 for walkover movement. Located on each side plate 22, 
23 are a pair of stops 26, 27 which engage link members 30, 31 
respectively when seat back 12 is in one of its two rest positions. 
Removably mounted on side plate 23, in any conventional manner, is a 
housing 36 enclosing a latching system which is normally inoperative, to 
permit walkover movement of the seat back, but which is actuated by 
deceleration of the vehicle above a preselected magnitude to restrain 
walkover movement of the seat back and to absorb any impact against the 
walkover seat back from behind resulting from a sudden stop or crash. 
Walkover movement of the seat back can be initiated by abnormal 
deceleration of the vehicle. In such a case, the walkover movement is due 
to the forward inertia of the seat back itself. Actuation of the latching 
system occurs at a deceleration no greater than and usually substantially 
less than the abnormal deceleration which initiates walkover movement of 
the seat, so that the latching system usually has already been activated 
before the aforementioned walkover movement is initiated. 
An embodiment of the latching system enclosed within housing 36 is 
illustrated in FIGS. 2-5. Mounted on the outer surface of the seat's side 
plate 23 are a pair of vertically disposed elements, 40, 41 each having a 
lower rectangular opening 42 for slidably mounting a first slidable member 
43 having a lower row of gear teeth 44 and an upper row of gear teeth 45. 
Engaging lower row of gear teeth 44 is a gear 46 fixedly mounted on 
rotatable shaft 29. 
When seat back 12 undergoes walkover movement, the linkage (30-32) 
connecting seat back 12 with rotatable shaft 29 causes shaft 29 to rotate, 
in turn rotating gear 46 which, by virtue of its engagement with the lower 
row of gear teeth 44, causes first slidable member 43 to undergo sliding 
movement in relation to vertical posts 40, 41. When seat back 12 moves 
from one seat end 13 to the other seat end 14 (see FIG. 1), first slide 
member 43 is moved in a direction toward seat end 14. Conversely, when 
seat back 12 is moved from seat end 14 toward seat end 13, first slide 
member 43 is moved toward seat end 13. In other words, first slide member 
43 is mounted for reciprocal sliding movement relative to vertically 
disposed elements 40, 41. 
Each vertically disposed element 40, 41 has an upper rectangular opening 47 
for slidably mounting an upper or second slidable member 48 which is 
vertically spaced from first slidable member 43. Second slidable member 48 
has a lower row of gear teeth 49 and is mounted for reciprocal sliding 
movement in relation to vertically disposed elements 40, 41. Each of first 
and second slide members 43, 48 constitutes a horizontally disposed slide 
bar mounted for reciprocal sliding movement in a horizontal direction, and 
each of the slide bars lies in substantially the same vertical plane in 
vertically spaced relation to the other slide bar. 
During normal walkover movement of the seat back (latching system 
inactive), second slidable member 48 is stationary and does not undergo 
sliding movement. During walkover movement of the seat back initiated by 
abnormal deceleration of the vehicle, (latching system active) second 
slidable member 48 does undergo slidable movement together with first 
slidable member 43, and the mechanism which effectuates that movement will 
now be described. 
Mounted on the outside surface of first slide member 43 is the lower end of 
a vertically disposed member 53 on which is rotatably mounted a shaft 54. 
Fixed on shaft 54, adjacent the outer surface of vertically disposed 
member 53, is a round gear 55, and fixed on shaft 54, adjacent the inner 
surface of vertically disposed member 53 is an elliptical gear 56 
constituting one embodiment of a latch element in accordance with the 
present invention. Also, rotatably mounted on vertically disposed member 
53 is a shaft 74 located above rotatable shaft 54. Fixed on shaft 74 is a 
reversing gear 75 engaging gear 55. 
Elliptical gear 56 is located between first and second slide members 43, 48 
and is mounted on rotatable shaft 54 for movement of gear 56 between a 
non-locking position shown in FIG. 4 and a locking position shown in FIG. 
5. When elliptical gear 56 is in its locking position, it engages both of 
first and second members 43, 48 (FIG. 5), and when elliptical gear 56 is 
in its non-locking position, it is disengaged from at least second member 
48 (FIG. 4). In the illustrated embodiment, elliptical gear 56 is 
disengaged from both first and second members 43, 48 when the elliptical 
gear is in its non-locking position. By virtue of its mounting on 
rotatable shaft 54, which is carried by vertically disposed member 53 
which in turn is carried by first slidable member 43, elliptical gear 56 
is mounted for movement with first member 43, independent of the movement 
of the elliptical gear between its locking and non-locking positions. 
Elliptical gear 56 is normally maintained in its non-locking position, 
illustrated in FIG. 4, by structure now to be described. Located near the 
upper end of vertically disposed member 53, and extending outwardly 
therefrom is a pin 59 which pivotally mounts the upper portion 60 of a 
pendulum indicated generally at 61 and comprising a pendulum arm 62 at the 
lower end of which is located a pendulum bob 63. By virtue of the mounting 
arrangement described in the preceding sentence, pendulum 61 is carried 
with first slidable member 43 as member 43 undergoes reciprocal sliding 
movement. 
Pin 59 mounts pendulum 61 for swinging movement, independent of its 
movement with first slidable member 43, between a vertically disposed 
pendulum rest position, illustrated in FIG. 4, and a second position, 
shown in FIG. 5, in which the pendulum is angularly displaced from its 
rest position. Pendulum 61 is normally maintained in its rest position 
(FIG. 4) during normal walkover movement of the seat back, and this occurs 
when the vehicle is at rest or is moving at substantially constant speed. 
In addition, the characteristics of the pendulum (e.g. length, weight, 
etc.) are such that the pendulum is maintained out of its second position 
(FIG. 5) during vehicle accelerations and during certain normal vehicle 
decelerations below a magnitude which depends upon adjustment of the 
pendulum characteristics, and this will be explained more fully 
subsequently. However, during all abnormal decelerations of the vehicle 
and during certain normal decelerations above a magnitude which depends 
upon adjustment of the pendulum characteristics, the pendulum is urged to 
its second position shown in FIG. 5, and when this occurs, a mechanism is 
actuated which moves elliptical gear 56 into its locking position shown in 
FIG. 5. 
More particularly, attached to pendulum 61, near the upper end thereof, is 
a gear segment 64 which engages reversing gear 75 which in turn engages 
gear 55. Gear segment 64 swings with pendulum 61, and as gear segment 64 
swings, it rotates reversing gear 75 which rotates engaged gear 55 in turn 
rotating shaft 54 which in turn pivots elliptical gear 56 from its 
non-locking position shown in FIG. 4 to its locking position shown in FIG. 
5. Gear 55, shaft 54 and elliptical gear 56 rotate in the same sense as 
that in which pendulum 61 swings, by virtue of the interposition of 
reversing gear 75 between gear segment 64 and gear 55. 
As shown in FIG. 5, elliptical gear 56 has a first plurality of teeth 57, 
for engagement with the upper row of gear teeth 45 on first slidable 
member 43, and a second plurality of gear teeth 58, spaced from first 
plurality of gear teeth 57, for engagement with the lower row of gear 
teeth 49 on second slidable member 48, when elliptical gear 56 is in its 
locking position shown in FIG. 5. When elliptical gear 56 is thus engaged 
with both lower first slidable member 43 and upper second slidable member 
48, the second slidable member is linked to the first slidable member for 
sliding movement together. 
When the vehicle undergoes abnormal deceleration, first member 43 undergoes 
sliding movement in response to walkover movement of the seat back due to 
the seat back's forward inertia. First member 43 is urged to undergo 
sliding movement for so long as there is a tendency for the seat back to 
undergo walkover movement. Moreover, once elliptical gear 56 has been 
pivoted into its locking position, it will remain in that position, 
linking second slidable member 48 to first slidable member 43, for 
movement together, for so long as first member 43 is urged to undergo the 
sliding movement described in the preceding two sentences. In other words, 
elliptical gear 56 is maintained in its locking position for at least as 
long as the seat back has a tendency to undergo walkover movement 
initiated by abnormal deceleration of the vehicle. 
When second slidable member 48 moves together with first slidable member 
43, in the manner described in the preceding paragraph, there is actuation 
of structure for progressively retarding that movement which in turn 
progressively retards or opposes walkover movement of the seat back, and 
this will now be described in more detail. 
Second slidable member 48 has an end 67 connected by a pin and slot 
arrangement 68, 69 to the upper end of a lever 70 having a lower end fixed 
to the unrestrained end of a torsion member 71 having a restrained end 
fixed at a location axially spaced, along the torsion member, from the 
location at which lever 70 is fixed to the unrestrained end of the torsion 
member. Torsion member 71 may be of any conventional construction 
heretofore employed for torsion members. In one embodiment, torsion member 
71 may have a cross-section comprising a plurality of alternating layers 
of spring steel and rubber strips. 
In a typical embodiment, the seat's cross member 20 is a tube enclosing 
torsion member 71, and torsion member 71 extends from the attachment of 
its unrestrained end with the lower end of lever 70, through tubular cross 
member 20, to a location within cross member 20 where the restrained end 
of torsion member 71 is fixed to cross member 20. Torsion member 71 may be 
fixed to cross member 20 at various locations between the physical ends of 
torsion member 71 to vary the torsion member's effective resistance to 
twisting. The location on the torsion member where it is fixed to the 
tubular cross member is, in effect, the restrained end of the torsion 
member. The shorter the distance between the torsion member's restrained 
and unrestrained ends, the greater the resistance to twisting. 
Torsion member 71 constitutes dampening structure, which is actuable in 
response to movement of elliptical gear 56 to its locking position, for 
progressively retarding or opposing walkover movement by the seat back 
which would occur during a sudden stop or crash on the part of the vehicle 
(abnormal deceleration). 
As a result of the linkage between torsion member 71 and end 67 of slide 
member 48, sliding movement of slide member 48 is translated into twisting 
action on the part of torsion member 71, and this action is what functions 
to progressively retard or oppose seat back walkover movement initiated by 
abnormal deceleration of the vehicle. In addition, any impact exerted 
against seat back 12, as a result of a sudden stop or crash is absorbed by 
torsion member 71. The dampening structure embodied in torsion member 71 
gradually absorbs the impact of a passenger against seat back 12, rather 
than simply resisting it. This in turn lessens the chance of injury to a 
passenger resulting from impact by that passenger into seat back 13, from 
behind, during a sudden stop or crash. As noted above, the effective 
length of torsion member 71 can be preset to vary the give or yield which 
occurs when a passenger impacts against seat back 12. 
Torsion member 71 is merely one embodiment of shock absorbing structure. 
One may also employ other embodiments of shock absorbing structure, 
including mechanical, pneumatic, hydraulic or structural shock absorbers. 
For each embodiment, the shock absorber is actuated by second member 48 as 
member 48 undergoes sliding movement. 
Because the latching mechanism initially resists and then gradually absorbs 
passenger impact into seat back 12, there is no ramping affect as would 
otherwise result from a combination of the forward inclination of the seat 
back and the forward inertia of the passenger which combine to propel the 
passenger into the overhead structure. As a result, the potential for 
injury to the passenger is substantially decreased. 
Upon cessation of the tendency of the seat back to undergo walkover 
movement initiated by abnormal deceleration of the vehicle, the normal 
functioning of pendulum 61 will return the pendulum from its second, 
angularly displaced position shown in FIG. 5, toward its vertically 
disposed rest position shown in FIG. 4. This assumes, of course, that the 
vehicle's deceleration has decreased in magnitude below the preselected 
level at which the latching system was activated. When this occurs, 
elliptical gear 56 is returned from its locking position, shown in FIG. 5, 
to its normal, non-locking position shown in FIG. 4. In other words, 
elliptical gear 56 is automatically returned to its rest position by the 
pendulum upon cessation of walkover movement initiated by abnormal 
decleration of the vehicle and upon the requisite decrease in vehicle 
deceleration. Prior thereto, the pendulum was restrained from returning 
toward its rest position by the forces maintaining elliptical gear 56 in 
its locking position, i.e. (1) the tendency of the seat back to undergo 
walkover movement initiated by abnormal deceleration of the vehicle and 
(2) the vehicle's deceleration above a preselected magnitude. 
Elliptical gear 56 lies in substantially the same vertical plane as that in 
which slidable members 43, 48 lie. Torsion member 71 extends in a 
direction transverse to that vertical plane, and pendulum 60 swings in an 
arc lying in a vertical plane parallel to the vertical plane in which 
slidable members 43, 48 and elliptical gear 56 lie. Elliptical gear 56 is 
mounted for pivotal movement about the pivot axis of shaft 54 which 
extends transversely to the vertical plane in which lie slidable members 
43, 48 and elliptical gear 56. 
The latching element illustrated in FIGS. 2-5 is in the form of an 
elliptical gear. Other embodiments of a latching element are shown in 
FIGS. 6 and 7. Like elliptical gear 56, these latching elements are 
mounted on shaft 54, and they are moved between locking and non-locking 
positions in the same manner as is elliptical gear 56, under the same 
conditions. 
Referring initially to FIG. 6, there is shown a latch element 76 fixed on 
rotatable shaft 54. Latch element 76 has a pair of upper corner portions 
77, 77 and a pair of lower corner portions 78, 78. Located at each upper 
corner portion 77 is a tooth or projection 79, 80 and located at each 
lower corner portion 78 is a tooth or projection 81, 82. First slidable 
member 43 has a pair of indentations 84, 84 each for engagement with one 
of the lower teeth 81, 82 on latch element 76, when the latch element has 
been moved to a locking position. Upper or second slide member 48 has a 
plurality of indentations 85, 85 one of which is engaged by an upper tooth 
79, 80 on latching element 76 when the latching element has been moved 
into a locking position. 
A normal, non-locking rest position for element 76 is shown in full lines 
in FIG. 6. When pendulum 61 is in the position shown in FIG. 5, latch 
element 76 is moved into the position shown in dash dot lines in FIG. 6 
wherein its lower tooth 82 engages an indentation 84 on first slidable 
member 43, and upper tooth 79 on latching element 76 engages an 
indentation 85 on upper slide member 48, thereby connecting the two slide 
members together for slidable movement together. 
In FIG. 7 there is shown an embodiment of latch element 86 fixedly mounted 
on rotatable shaft 54 and having a knurled peripheral surface including a 
pair of spaced apart knurled surface portions 87, 88 for engaging 
respective knurled surface portions 89, 90 on slidable members 43, 48 
respectively, when latch element 86 is in its locking position, a 
condition which occurs when pendulum 61 is in the position shown in FIG. 
5. 
The structure associated with latch elements 76 and 86 (FIGS. 6 and 7) is 
essentially the same as the structure associated with latch element 56, 
and the operation of all these latch elements 56, 76 and 86 is essentially 
the same. The only substantial difference between the latching system 
illustrated in FIGS. 2-5 and that employing the latch elements illustrated 
in FIGS. 6 and 7 is the shape of the latch element and the associated 
engaging structure on the first and second slide members 43, 48. 
As noted above, once the latch element is moved into its locking position, 
it is maintained in that position for at least as long as there is a 
tendency for the seat back to undergo walkover movement initiated by 
abnormal deceleration of the vehicle. This will now be described more 
fully with reference to FIG. 6 and latch element 76, although latching 
systems employing latch elements 56 or 86 would function in a similar 
fashion. 
Latch element 76 is mounted for pivotal movement in a clockwise sense, as 
viewed in FIG. 6. Latch element 76 is so positioned in relation to first 
slidable member 43 that, when the latch element is pivoted into its 
locking position (dash-dot lines in FIG. 6), tooth 82 on latch element 76 
undergoes pivotal movement having a directional component substantially 
the same as the direction of linear movement of slidable member 43 when 
the seat back undergoes walkover movement. This direction is indicated by 
arrow 50 in FIG. 6. At the same time, tooth 79 on latch element 76 
undergoes pivotal movement having a directional component substantially 
opposed to the direction of linear movement of second slidable member 48 
when latch element 76 engages both members 43 and 48 and the seat back 
undergoes walkover movement. The direction in which member 48 moves is 
indicated by arrow 51 in FIG. 6. 
For so long as the seat back has a tendency to undergo walkover movement, 
member 43 will tend to move in the direction of arrow 50, and the 
engagement of indentation 84 with tooth 82 will urge latch element 76 in a 
clockwise sense, as viewed in FIG. 6, to maintain latch element 76 in 
locking engagement with second member 48. When there is a cessation of 
walkover movement by the seat back, the tendency of member 43 to move in 
direction 50 ceases, as does the force maintaining the engagement between 
(1) tooth 82 on latch element 76 and (2) indentation 84 on member 43. As a 
result, latch element 76 can be pivoted in a counterclockwise sense under 
the urging of pendulum 61 when the normal functioning of the pendulum 
returns it to its rest position, thereby disengaging latch element 76 from 
both slidable members 43 and 48. 
The relationships described in the two preceding paragraphs occur because 
the latch element pivots in the same sense as the pendulum. This 
co-pivotal effect exists because of the three-gear linkage between the 
pendulum and the latch element. The same co-pivotal effect can be obtained 
by mounting the latch element directly on the pendulum or on a rotatable 
pivot pin for the pendulum (FIG. 8). 
There is an advantage to employing a multi-gear linkage between the latch 
element and pendulum 61 which is not available when the latch element is 
mounted directly on the pendulum or its pivot pin. More particularly, when 
the latch element is directly mounted on the the pendulum or its pivot 
pin, the latch element of necessity swings through the same arc as the 
pendulum. However, when the latch element is connected to the pendulum by 
a multi-gear linkage, one can have the latch element swing through an arc 
either more than or less than (or the same as) the arc of the pendulum, 
depending upon the selection of gear ratios. 
On the other hand, when the latch element is mounted directly on the 
pendulum or its pivot pin, there is a reduction in the number of parts 
(e.g. elimination of the gear linkage between the pendulum and the latch 
element), with its attendant economies. 
Pendulum bob 63 may be mounted for adjustable movement along the length of 
pendulum arm 62, e.g. by threadedly engaging the bob on the arm. Changing 
the position of bob 63 on arm 62 changes the distance between (a) the 
pivotal axis of the pendulum, at pivot shaft 59, and (b) the center of 
gravity of bob 63, and this is tantamount to adjusting the length of 
pendulum arm 62. The weight of bob 63 can be changed with weight shims 
(not shown) added to or removed from the bob, e.g. on flat surface 65 of 
bob 63, employing removable threaded fasteners (not shown) engaging 
internally threaded openings at surface 65. 
The expedients described in the preceding paragraph may be utilized to 
change the magnitude of vehicle deceleration at which the latching system 
is automatically activated, in accordance with known principles of 
pendulum operation. More particularly, increasing the weight of the 
pendulum bob or decreasing the length of the pendulum arm, or both, 
decreases the magnitude of vehicle deceleration required to swing pendulum 
61 to a position at which the latching system is automatically activated 
(FIG. 5). 
In the embodiment illustrated in FIG. 8, a pendulum 161 has an upper 
portion 160 fixed on a pivot pin 159 rotatably mounted on vertically 
disposed member 53, on one side of member 53. Also fixed on pivot pin 159, 
on the other side of member 53 is latch element 76. As a result of this 
arrangement, the latch element swings directly with the pendulum and moves 
directly with the pendulum as the pendulum is carried by first member 43 
(via member 53) when first member 43 undergoes movement. 
Pendulum 161 also comprises a pendulum arm in the form of an externally 
threaded rod 162, extending downwardly from pendulum upper portion 160 
through an unthreaded opening in a pendulum bob 163 which is slidably 
mounted on arm 162 and is maintained in a preselected position on 
externally threaded arm 162 by upper and lower internally threaded nuts 
164, 165. The position of bob 163 on arm 162 can be vertically adjusted by 
loosening nuts 164, 165, then sliding bob 163 on arm 162 to a newly 
selected position, and then tightening nuts 164, 165 against bob 163 to 
hold the bob in its new position on arm 162. Changing the position of bob 
163 on arm 162 is tantamount to changing the length of the pendulum arm, 
and that changes the magnitude of vehicle deceleration at which the 
latching system is automatically activated. As noted above, the 
characteristics of the pendulum arrangement can be adjusted to activate 
the latching system at a normal, relatively moderate vehicle deceleration, 
0.3 g for example. 
Referring now to FIG. 9, in this embodiment, first slidable member 43 is 
driven by a linkage other than gear 46 and lower row of gear teeth 44 (see 
embodiment of FIG. 3). The driving linkage in FIG. 9 comprises a pin 170 
extending through a slot 171 in side plate 23. Pin 170 is engaged by a 
lower inner edge portion 172 on link member 30, when link members 30, 31 
pivot in a counterclockwise sense (from right to left) as viewed in FIG. 
9; and pin 170 is engaged by a lower inner edge portion 173 on link member 
31, when the link members pivot in a clockwise sense (from left to right) 
as viewed in FIG. 9. As link members 30, 31 pivot, they urge pin 170 to 
slide along slot 171 thereby sliding member 43. The rest of the structure 
associated with the embodiment of FIG. 9 (much of which is not shown) may 
be the same as the structure in the embodiments of FIGS. 1-8, although a 
double torsion bar arrangement may be utilized, as shown in FIG. 9. 
More particularly, upper slidable member 48 has a pair of opposite ends 
167, 168 each of which is convexly curved to engage a tab 175 at the upper 
end of a respective torsion lever 176 having a lower end fixed on a 
torsion bar 177. There are a pair of levers 176 and a pair of torsion bars 
177 each associated with a respective end 167, 168 of upper slidable 
member 48. Each torsion bar 177 is similar to torsion bar 71 in the 
embodiments of FIGS. 1-8. The torsion bar associated with upper slidable 
member end 167 is actuated when slidable member 48 moves to the left, as 
viewed in FIG. 9 (toward seat end 13 in FIG. 1), and the torsion bar 
associated with upper slidable member end 168 is actuated when slidable 
member 48 moves to the right, as viewed in FIG. 9 (toward end 14 in FIG. 
1) When slidable member 48 moves to the left, the torsion bar associated 
with end 168 is inactive, and when slidable member 48 moves to the right, 
the torsion bar associated with end 167 is inactive. 
Referring again to FIG. 1, housing 36 defines a pocket located adjacent one 
side of seat 10, and the housing totally encloses the latching mechanism 
rendering that mechanism relatively inaccessible to a passenger. Because 
of this, there is no potential of injury to the passenger as might occur 
if the passenger were to come into contact with any part of the latching 
mechanism. 
The latching system is automatically activated only by vehicle deceleration 
above a preselected magnitude which typically is less than abnormal 
deceleration. At all other times, the walkover seat may be freely moved 
between its two normal rest positions, at the seat's opposite ends 13, 14, 
without the need to manipulate a release handle or pedal or the need to 
engage in any type of latch deactuating activity. Because the latching 
system is operated relatively seldom and because there are no actuating 
handles or pedals requiring operation by a passenger in order to effect 
normal walkover movement of seat back 12, the need for repairs or 
maintenance of the latching system is essentially eliminated. 
In addition, the latching system is capable of automatic activation when 
seat back 12 is at either of its two normal rest positions, i.e. at each 
of the two opposite seat ends 13, 14, or at any position therebetween. As 
shown in the drawing, both the latching elements and the members engaged 
by the latching element are mounted on frame plate 23 at a location 
displaced from seat back 12. 
The foregoing detailed description has been given for clearness of 
understanding only, and no unnecessary limitations should be understood 
therefrom, as modifications will be obvious to those skilled in the art.