Friction detent apparatus for seat accessory

A friction detent apparatus includes a resistance washer having a planar circular body with a central portion fixedly mounted to a pivot rod attached to a support structure, the body having a first arcuate friction contact surface spaced a first predetermined distance from the central portion and a second arcuate friction contact surface spaced a second greater predetermined distance from the central portion, a first detent nub formed on the first contact surface and a second detent nub formed on the second contact surface. First and second follower pins are fixedly mounted on a device pivotally mounted on the pivot rod for engaging the first and second friction surfaces respectively. The pins move along the friction surfaces as the device is rotated relative to the pivot rod and the detent nubs releasably retain the pins in an "end of travel" position. In a tension beam washer form, an elongated arcuate slot in the body has the first friction surface as a side thereof and a portion of the body is deflected outwardly under tension as the first pin moves past the first detent nub. In a compression beam washer form, the first friction surface is formed as a radially recessed portion of a periphery of the body, an arcuate slot is formed in the body and the portion of the body adjacent the slot is deflected inwardly under compression as the first pin moves past the first detent nub.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to an apparatus for controlling 
pivotal movement and, in particular, to an apparatus for frictionally 
resisting and detenting pivotal movement of a vehicle seat accessory. 
2. Description of Related Art 
Many vehicular components, as well as elements in other fields, are mounted 
for selectively controlled pivotal movement. Increasingly, vehicles are 
being provided with seat accessories such as movable armrests and covered 
storage compartments centrally located between the front seats and, often, 
between the rear seats. It is desirable to have the armrests and 
compartment covers remain in the up/down or open/closed positions and to 
provide a degree of frictional resistance to movement between those 
positions. Previously, frictional forces have generally been provided by a 
relatively tight frictional engagement between opposing washers or the 
like, along the pivot pin, axle, etc. Further, provision of adjustment 
capabilities has often been provided by a mechanical, spring biased detent 
structure. However, all of these arrangements require the manufacture and 
assembly of a multiple of parts which, in turn, causes an increase in 
fabrication costs. Also, with extended use, these systems tend to loosen 
and wear. 
SUMMARY OF THE INVENTION 
The present invention concerns a friction detent apparatus for use with a 
device pivotally mounted on a pivot rod attached to a support structure. 
The apparatus includes a resistance washer having a generally planar 
circular body with a central portion fixedly mounted to a pivot rod 
attached to a support structure, the resistance washer body having a first 
generally arcuate friction contact surface spaced a first predetermined 
distance from the central portion and a second generally arcuate friction 
contact surface spaced a second predetermined distance from the central 
portion, the second predetermined distance being greater than the first 
predetermined distance. A first detent nub is formed on the first friction 
contact surface and a second detent nub is formed on the second friction 
contact surface. A first follower pin is fixedly mounted on the device 
pivotally mounted on the pivot rod for engaging the first friction contact 
surface and a second follower pin is fixedly mounted on the device for 
engaging the second friction contact surface. The first and second 
follower pins move along the first and second friction contact surfaces 
respectively as the device is rotated relative to the pivot rod and the 
first and second detent nubs releasably retain the first and second 
follower pins respectively in an "end of travel" position along the first 
and second friction contact surfaces. 
In a tension beam embodiment, the resistance washer body has an elongated 
arcuate slot formed therein with the first friction contact surface being 
an outermost edge or side of the slot. A portion of the resistance washer 
body between the first friction contact surface and a periphery of the 
body is deflected outwardly under tension as the first follower pin moves 
past the first detent nub. In a compression beam embodiment, the first 
friction contact surface is formed as a radially recessed portion of a 
periphery of the resistance washer body. The body has an arcuate slot 
formed therein between the first detent nub and the central portion and a 
portion of the body between the first friction contact surface and the 
slot is deflected inwardly under compression as the first follower pin 
moves past the first detent nub. In both embodiments, the second friction 
contact surface is formed on the periphery of the resistance washer body, 
the body has an arcuate slot formed therein between the second detent nub 
and the central portion and a portion of the resistance washer body 
between the second friction contact surface and the slot is deflected 
inwardly under compression as the second follower pin moves past the 
second detent nub. 
The apparatus includes a stop adapted fixedly mounted to the pivot rod and 
having a first radially extending finger for engaging the first follower 
pin at said "end of travel" position and a second radially extending 
finger for engaging the second follower pin at the "end of travel" 
position. The resistance washer body is attached to the stop. The 
apparatus includes another detent nub formed on the first friction contact 
surface for releasably retaining the first follower pin in another "end of 
travel" position along the first friction contact surface. 
The compression beam resistance washer varies from prior art designs inter 
alia, in that it places the resistance beam in compression instead of 
tension. Thus, it is an object of the present invention to achieve desired 
resistance forces while providing a more durable product. This increased 
durability is the result of a decrease in creep as a result of the beam 
configuration and kinematics. 
The previously known "tension" type beams have a tendency to exhibit wear 
and loss of resistance after fewer cycles are applied as compared to a 
compression beam. It is a further object of the present invention to 
provide greater initial resistance forces maintained over a longer cycle 
life. An outer/follower resistance feature reduces or eliminates the 
effects of production variation.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the Figures, wherein like numerals indicate like or 
corresponding parts throughout the several views, there is shown in FIG. 1 
a vehicle seat assembly 10 including a left hand seat 12 and a right hand 
seat 14. The left hand seat 12 has a left hand seat back 16 attached to a 
left hand seat bottom 18 which is typically mounted on a vehicle floor 
(not shown). Similarly, the right hand seat 14 has a right hand seat back 
20 attached to a right hand seat bottom 22 which is typically mounted on 
the vehicle floor. The seats 12 and 14 are spaced apart by a seat 
accessory 24 which also is typically mounted on the vehicle floor. 
As shown in the FIG. 2, the seat accessory 24 includes a support structure 
in the form of a seat accessory base 26. The seat accessory base 26 is 
constructed of a pair of sidewalls 28 and 30 and a rear wall 32. The left 
hand sidewall 28 extends in a generally vertical plane parallel to a 
generally vertical plane of the right hand sidewall 30. The sidewalls 28 
and 30 are connected at rear edges thereof by the generally vertically 
extending rear wall 32 to form a three-sided support structure. The seat 
accessory 24 can be mounted to the vehicle floor (not shown) by any 
suitable means such as fasteners and mounting tabs. For example, a 
mounting tab 34 is shown as extending generally horizontally from a lower 
edge of the left sidewall 28 and having an aperture 36 formed therein for 
receiving a fastener (not shown). A rear portion of an armrest 38 is 
pivotally mounted to the sidewalls 28 and 30 adjacent the rear wall 32. 
The armrest 38 is shown in a generally vertically extending "up" position 
which locates it between the seat backs 16 and 20 as shown in the FIG. 1. 
Although not shown, the armrest 38 can be pivoted to a "down" position 
wherein it extends generally horizontally above the upper edges of the 
sidewalls 28 and 30. 
The area between the sidewalls 28 and 30 can be used as a storage area. 
Although not shown, a feature tray can be positioned between the sidewalls 
28 and 30 for receiving loose articles such as sunglasses, coins, a garage 
door opener, a cellular telephone, etc. Therefore, it is desirable to 
close this storage space to provide a degree of security for the stored 
articles. The feature tray space can be closed by a device such as a 
feature tray cover 40 shown in the "closed" position in the FIG. 1. The 
feature tray cover 40 is pivotally mounted on the sidewalls 28 and 30 near 
a front edge thereof for movement between the "closed" position and an 
"open" position shown in phantom in the FIG. 1 and in solid line in the 
FIG. 2. A loop or strap 42 can be attached to a rear portion of the 
feature tray cover 40 to assist an occupant of the vehicle in moving the 
feature tray cover from the "closed" position to the "open" position. The 
feature tray cover 40 is pivotally attached to the sidewalls 28 and 30 by 
a mounting assembly 44 shown in more detail in the FIG. 3. 
There is shown in the FIG. 3 a portion of a first support bracket 46 which 
is attached to the sidewall 28 and a portion of a second support bracket 
48 which is attached to the sidewall 30. The mounting assembly 44 includes 
a pivot rod 50 which is fixedly attached at opposite ends thereof to the 
brackets 46 and 48. Fixedly attached to a central portion of the pivot rod 
50 is a stop 52 having a central aperture formed therein for receiving the 
pivot rod. The stop 52 includes a first finger 54 radially extending from 
the pivot rod a first predetermined distance. A second finger 56 is formed 
on the stop 52 generally diametrically from the first finger 54 and 
extends in a radial direction from the pivot rod 50 a second predetermined 
distance which is greater than the first predetermined distance. Attached 
to the stop 52 is a generally circular resistance washer 58 which is shown 
in more detail in the FIG. 4. The mounting assembly 44 further includes a 
bracket assembly 60 for pivotally mounting the feature tray cover 40 on 
the seat accessory base 26. The bracket assembly 60 includes a first cover 
mounting bracket 62 attached to an inner surface of the feature tray cover 
40. The first bracket 62 has a first upstanding leg 64a and a spaced apart 
second upstanding leg 64b. The first leg 64a is positioned adjacent the 
first support bracket 46 and has an aperture formed therein for pivotally 
receiving the pivot rod 50. The bracket assembly 60 includes a second 
cover mounting bracket 66 which also is attached to the inside surface of 
the feature tray cover 40. The second bracket 66 is positioned adjacent 
the second support bracket 48 and has an aperture formed therein for 
pivotally receiving the pivot rod 50. Thus, the mounting brackets 62 and 
66 are free to rotate about a longitudinal axis of the pivot rod 50 
thereby permitting the feature tray cover 40 to be pivoted between the 
"open" and the "closed" positions. 
The second leg 64b extends toward but does not contact a central portion of 
the pivot rod 50. Extending from the second leg 64b toward the second 
bracket 66 are a first follower pin 68 and a second follower pin 70. The 
first follower pin 68 extends generally parallel to the longitudinal axis 
of the pivot rod 50 and is spaced from the pivot rod the first 
predetermined distance for abutting the first finger 54 in the position 
shown. The second follower pin 70 also extends generally parallel to the 
longitudinal axis of the pivot rod 50 and is spaced therefrom at the 
second predetermined distance to abuttingly engage the second finger 56. 
The resistance washer 58 is shown in more detail in FIG. 4 as having a 
generally planar circular body 72. An aperture 72a is formed in a central 
portion of the body 72 for receiving the pivot rod 50. A pair of posts 72b 
extend from the body 72 and are received by a corresponding pair of 
apertures formed in the stop 52 for attaching the washer 58 to the stop. 
The posts 72b can be staked or otherwise deformed (FIG. 3) to fix the 
resistance washer 58 in place. An elongated arcuate slot 72c is formed in 
the body 72 adjacent a periphery 74 thereof. The first follower pin 68 is 
aligned with and extends through the elongated arcuate slot 72c. The pin 
68 is dimensioned to frictionally engage opposite sides 72d of the slot 
72c. Thus, as the feature tray cover 40 is rotated about the pivot rod 50 
to open and close, the first follower pin 68 will be moved in the 
directions of arrows 76 and frictional contact between the follower pin 
and contact surfaces of the sides 72d of the slot 72c will provide some 
resistance to this rotation. A pair of detent nubs 78 are formed in the 
sides 72d of the slot 72c adjacent opposite ends 72e and 72f of the slot. 
The detent nubs 78 provide a positive releasable locking of the first 
follower pin 68 at each end 72e and 72f of the slot 72c to retain the 
feature tray cover 40 in the "open" and "closed" positions. At the end 
72f, the pin 68 contacts the first finger 54 and at the end 72e, contacts 
the second finger 56. 
The second follower pin 70 frictionally engages a contact portion of the 
periphery 74 of the body 72. Rotation of the feature tray cover 40 causes 
the second follower pin 70 to be moved in the directions of arrows 80. A 
third detent nub 82 is formed on the periphery 74 adjacent the end 72e of 
the slot 72c. When the feature tray cover 40 is rotated to the "closed" 
position, the second follower pin 70 rides over the third detent nub 82 to 
provide a locking function. Therefore, it is necessary to exert additional 
force to initiate movement of the feature tray cover 40 from the "closed" 
position in order to force the pin 70 back over the detent nub 82. A 
relatively short arcuate slot 84 is formed in the body 72 of the 
resistance washer 58 adjacent the third detent nub 82 to permit the 
periphery 74 and the third detent nub to deform sufficiently to allow the 
second follower pin 70 to pass. The portion of the body 72 between the 
side 72d and the periphery 74 deforms in a similar manner when the pin 68 
passes the detent nubs 78. 
There is shown in the FIG. 5 and the FIG. 6 an alternate embodiment 
resistance washer 100 which is attached to the stop 52 in place of the 
resistance washer 58. The resistance washer 100 has a generally planar 
circular body 102. An aperture 102a is formed in a central portion of the 
body 102 for receiving the pivot rod 50. A smaller diameter aperture 102b 
is formed in the body 102 for receiving a fastener 102c received by a 
corresponding aperture formed in the stop 52 for attaching the washer 100 
to the stop. Alternatively, one or more of the posts 72b (FIG. 4) can be 
used fix the resistance washer 100 in place. A portion of a periphery 104 
of the body 102 is radially recessed to form a contact surface 102d for 
engaging the first follower pin 68. Thus, as the feature tray cover 40 is 
rotated about the pivot rod 50 to open and close, the first follower pin 
68 will be moved in the directions of arrow 76 and frictional contact 
between the follower pin and the contact surface 102d will provide some 
resistance to this rotation. A pair of detent nubs 106 are formed at 
opposite sides of ends 102e and 102f of the contact surface 102d. The 
detent nubs 106 provide a positive releasable locking of the first 
follower pin 68 at each end 102e and 102f to retain the feature tray cover 
40 in the "open" and "closed" positions. At the end 102f, the pin 68 
contacts the first finger 54 and at the end 102e, contacts the second 
finger 56. 
Rotation of the feature tray cover 40 on the pivot rod 50 also rotates the 
second follower pin 70 in the directions of the arrow 80. However, in 
order to move from the position shown, the second follower pin 70 must 
pass by a third detent nub or ramp 108 formed in the periphery 104 
adjacent the end 102e. An arcuate slot 110 is formed in the body 102 
adjacent the detent nub 108 to permit the periphery 104 of the resistance 
washer 100 to deflect when the second follower pin 70 passes that point. A 
pair of similar arcuate slots 112 are formed in the body 102 adjacent the 
ends 102e and 102f to permit the contact surface 102d to deform when the 
first follower pin 68 passes the detent nubs 106. 
The resistance washers 58 and 100 are formed of a resilient material such 
as a plastic material. In the washer 100, those portions of the body 102 
adjacent the slots 110 and 112 function as compression beams. Thus, the 
compression beam resistance washer 100 described above allows an adjacent, 
but separate, component to move rotationally with respect to the washer, 
and to be captured at the two "end of travel" positions. The pins 68 and 
70 function as the component to be captured. At the "end of travel" 
positions, the detent nubs 106 are provided as an obstacle to overcome in 
order to disengage the pins. Utilizing a slight interference between the 
detent 108 and the second pin 70, the washer is able to nest the first pin 
68 further into the "closed end of travel" position and reduce or 
eliminate "chucking" caused by normal production variation. To disengage 
the pins and move out of the "closed end of travel" position, a rotational 
motion about the pivot pin 50 is required. As the motion begins, the 
detents cause an interference to the pins that can only be overcome by 
deflecting the adjacent beams toward the center of the washer body. This 
deflection process provides the resistance force that captures the pins at 
the "end of travel" position. As the rotational motion continues, the pins 
68 and 70 travel beyond the detent nubs to portions of the contact 
surfaces which are at distances from the longitudinal axis of the pivot 
pin 50 to return the adjacent slots to the uncompressed shapes. 
Creep is a permanent set or plastic deformation caused by the application 
of stress, and can be both time and temperature dependent. The compression 
beam concept allows for a change in overcoming resistance force simply by 
varying the distance between the pivot point and detent nubs (i.e., an 
increase in distance will yield a higher resistance). Additionally, 
varying the areas of the slots 110 and 112 will effect the resistance 
(i.e., a larger area will yield greater flex and a lower resistance). If 
the washer 100 is constructed from a thermal plastic material, wear is 
typically a concern to the conventional tension beam concepts, 
specifically at the detent nubs. Allowing the beams to deflect away from 
the pins significantly reduces the wear (as compared to tension beams) at 
these points by minimizing or eliminating the possibility of creep of the 
material. This reduction of wear provides a more durable component by 
lengthening the useful cycle life, i.e., maintains the initial resistance 
force longer. 
The resistance washer 58 functions on a tension beam concept to allow an 
adjacent, but separate, component to move rotationally with respect to the 
washer, and be captured at the "end of travel" positions. As with the 
compression beam design, detents 78 and 80 provide a stop that retains the 
pins within the "closed end of travel" position. The anti-chuck feature 
also can be incorporated into the tension beam construction by causing a 
slight interference between the second pin 70 and the detent nub 82 which 
nests the first pin 68 further into the "end of travel" position to reduce 
or eliminate the effects of normal production variation. To disengage the 
pins from the "closed end of travel" position, a rotational motion causes 
the pins to move and they must overcome the two stops created by the 
detent nubs 78 and 80. The first pin 68 creates an interference with the 
beam material between the slot 72c and the periphery 74 that causes the 
beam to deflect and "stretch", thus placing it under a tension load. The 
disadvantage of this system is that the beam is unable to "stretch" 
sufficiently enough to provide a large overcoming force without causing 
the material adjacent the detent nub 78 to creep. In order to increase the 
resistance force, the detent nub 78 must be moved closer to the pivot 
point at the pivot rod 50 in order to create a greater interference to the 
first pin 68. As this interference grows, the amount of stress increases 
and, in turn, increases the amount of creep experienced in the body 72. 
The increased creep results in a shorter life cycle expectancy, and 
therefore a less durable component. The second pin 70 and detent nub 80 
react very similarly to the first pin 68 and the detent nub 78 with 
respect to creep, when the compression beam design is not utilized. 
Because the material has no means of deflecting away from the pin, the 
material creeps under the stress. 
Because the tension beam resistance washer 58 does not allow for an 
equivalent amount of flex with respect to the compression beam resistance 
washer 100, the material undergoes more creep and results in a less 
durable product. It is also difficult to obtain the same initial 
resistance forces over an extended cycle life. Finally, the tension beam 
resistance washer 58 typically exhibits a tendency to fracture as a result 
of the continuous "stretching" and high stress which is placed upon the 
detent nub 78 during the disengaging process. However, the tension beam 
resistance washer 58 may be suitable for use with light weight covers 
requiring little resistance and holding force. 
The invention has been described in an illustrative manner, and it is to be 
understood that the terminology which has been used is intended to be in 
the nature of words of description rather than of limitation. 
Obviously, many modifications and variations of the present invention are 
possible in light of the above teachings. It is, therefore, to be 
understood that within the scope of the appended claims, wherein reference 
numerals are merely for convenience and are not to be in any way limiting, 
the invention may be practiced otherwise than as specifically described.