Two-position latch system

A power boat helmsman's station chair having a two-section seat bottom articulated by a pivotal hinge framework so that the front section of the seat can be folded up from its normal position as a horizontal extension of the rear section of the seat bottom to a position raised and disposed over the rear section. Port and starboard hinge subassemblies include a L-shape angle corner bracket that is fastened to both the bottom and the side boards of the rear seat section framework, thereby reinforcing the same, and that pivotally carries one end of an associated hinge arm fastened at its other end to the framework of the seat bottom front section. A one piece plastic member of generally inverted V-shaped configuration has one arm fixed to the upright flange of the comer bracket with the other arm disposed for spring latching, camming engagement with a cam follower edge surface of the pivot end of the hinge arm. The mobile arm of the spring latch member is cam profile configured and oriented to yieldably hold the hinge arm in the upright position of the seat front section and its spring stabilizing force can be overcome by pulling forwardly on the upright seat bottom front section with a predetermined force to unlatch the same and fold it down to its normal horizontal use position.

FIELD OF THE INVENTION 
This invention relates to pivotal frame work two-position latch systems, 
and more particularly to a power boat helmsman's station chair having a 
two-section seat bottom articulated by such a latch system. 
BACKGROUND OF THE INVENTION 
Framework support systems that are articulated by a hinge or like pivotal 
support structure for pivoting a section of the framework between two 
alternate in-use positions, and that are spring-biased so as to be stable 
in either position, are found in a myriad of applications too numerous to 
enumerate. 
One of such applications to which the present invention is directed 
involves problems encountered with helmsman operation of power boats or 
similar water-borne pleasure craft due to the close orientation of the 
steering wheel and helmsman seat in the helmsman station of the power 
boat. The seat bottom construction of the helmsman chair is designed to 
comfortably support the helmsman in seating position with his knees 
beneath the steering wheel so that the helmsman can comfortably manually 
grip the steering wheel for guiding the power boat. This requires that the 
front edge of the seat bottom be located at a lower elevation and only 
slightly aft of the closest portion of the steering wheel. Hence there is 
little or no clearance between the steering wheel and the front edge of 
the seat bottom to allow the helmsman to comfortably stand up and steer 
the boat with the steering wheel centered in front of him. However, as is 
often the case when docking, the helmsman needs to quickly standup for 
better visibility all around the boat, and particularly over the bow. With 
one-section seat bottoms of fixed construction he cannot do this easily 
because typically the seat bottom of the helmsman chair is in his way. 
In an effort to overcome this problem a helmsman seat bottom construction 
recently has been provided that is constructed in two sections, a fixed 
immobile rear section and a movable front section hinged to the main 
framework of the chair so as to be normally supported in a horizontal 
position as a horizontal forward extension of the seat bottom rear 
section. When the aforementioned docking situation arises and the helmsman 
needs to standup, the front section may be manually pivoted upwardly and 
rearwardly so as to be disposed over the rear section, thereby providing 
the needed increase in standing room clearance between the steering wheel 
and seat bottom. 
However this prior swinging front section was stabilized only by 
gravitational forces in both up and down positions. Although this manner 
of pivot stabilization is satisfactory for the horizontal position of the 
front section when the helmsman is sitting on the chair, due to the 
typical rocking and pitching motion encountered in power boat operation 
the front section was found to be not satisfactorily stabilized by 
gravitational forces in the up position, even when the up position was set 
by stops slightly over-center in the aft direction. 
The use of hook and eye type catches or the like is not a satisfactory 
solution to this stabilization problem since hooking such a catch diverts 
the attention of the elmsman from control of the power craft precisely at 
the time when all his attention is most needed for maneuvering. Likewise, 
although power boat seats are often mounted for fore and aft adjustment on 
sliding rail constructions, the mechanism for locking the chair in place 
in adjusted position is not adapted to enable quick, automatic push back 
of the chair seat to provide the needed standing room clearance. 
OBJECTS OF THE INVENTION 
Accordingly, an object of the present invention to provide an improved 
pivotal framework two-position spring latch system adapted to stabilize 
and support a hinged section of the framework in either of two positions 
spaced angularly from one another about the pivot axis, and that is 
particularly adapted for use in combination with the aforementioned 
two-section helmsman chair seat bottom construction to enable the helmsman 
to quickly and easily fold up the front of the seat by use of his hand, or 
by the motion of the back of his legs, as he moves from a sitting to a 
standing position while docking or in similar close quarters maneuvering 
situations. 
Another object is to provide a pivotal framework latch system for a chair 
seat bottom construction of the aforementioned or like character that can 
support the hinged section in a horizontal position with a load bearing 
downwardly on the same, and which can be folded up and rearwardly to a 
generally vertical position in which the hinged section is sufficiently 
strong and stabilized to be load weight bearing in the up position to 
thereby serve as an alternate elevated seat for enhanced visibility at the 
helm. 
A further object is to provide an improved pivotal framework two-position 
latch support system of the aforementioned character that is strong, and 
corrosion resistant so as to be suitable for outdoor saltwater marine use, 
and which is simple in construction and assembly, hidden from view, 
non-catching on adjacent seat covering materials, efficient and reliable 
in operation for the aforementioned purposes and which provides a long 
service life.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring in more detail to the accompanying drawings, FIGS. 1 and 2 
illustrate the helmsman station of a medium sized power boat of the "cabin 
cruiser" type. The helmsman station includes a conventionally upholstered 
helmsman's chair 20 supported in adjustable fixed position by suitable 
chair rail support structure 22 fastened to the floor deck 24 of the 
helmsman station, a conventional steering wheel 26, instrument panel 28, 
and throttle control handle 30. Chair 20 has a fixed seat back 32 
extending upright as supported by the internal framework (not shown) of 
the seat, and a two-section seat bottom 34 made up of a generally 
horizontally disposed rear section 36 having conventional supporting 
framework, (not shown), fixed to that of seat back 32 so as to be immobile 
relative to thereto, and a front section 38 shown in its folded down 
position in FIG. 1 and its folded up position in FIG. 2. 
The interior as well as exterior construction of chair 20 is generally 
conventional and therefore not shown or described in detail. However, as 
indicated in FIGS. 3 and 4, rear section 36 of the seat bottom 34 has a 
bottom board support 40 suitably secured to a pair of flanking side 
boards, the port side board 42 being partially shown in phantom in FIG. 3 
and in solid lines in FIG. 4. A conventional seat cushion 44 (FIG. 1) 
comprising the usual cushion padding and seat covering materials are 
suitably mounted on seat bottom board 40, either affixed thereto or made 
as a separable cushion movably seated thereon. The port and starboard 
sides of cushion 44 are spaced laterally slightly inwardly from the 
associated port and starboard arm rests 46 and 48, which in turn may be 
formed as extensions of back 32 and have cushioning and covering material 
upholstered to the port and starboard rear section side boards 42. 
For clarity of illustration seat cushion 44 is omitted from FIGS. 3 and 4. 
However FIG. 4 does show a portion of the cushioning material 46 that 
covers the port arm rest 46 and wraps under the bottom board 40, the same 
typically being affixed thereto by adhesive material. 
The front section 38 of seat bottom 34 likewise is constructed with 
conventional seat cushion and covering materials to provide a forward 
cushion 48 with interior conventional foam rubber cushion material 52 
(FIG. 4) in which a bottom framework board 50 is embedded. 
The articulation and support of the seat bottom front section 38 on chair 
20 is provided by port and starboard hinge sub-assemblies constructed as 
the mirror-image of one another and otherwise being identical. The port 
hinge sub-assembly 60 is best seen in FIGS. 3 and 4 and comprises two main 
components, namely a right angle mounting bracket 62 and a pivotally 
mobile hinge arm 64. Bracket 62 is L-shaped in transverse cross section 
and has a base flange 66 secured to the upper surface of seat board 40 by 
three hex-head wood screw studs 68 arranged as shown in FIGS. 3 and 4 and 
inserted through corresponding through-holes 67 (FIG. 14) in base flange 
66. Bracket 62 also has an upright hinge-arm-mounting flange 70 that abuts 
the adjacent side board 42 and is secured thereto by two flat head screws 
(not shown) inserted through bevel screw holes 72, 74 (FIGS. 13-15) and 
located in flange 70 as shown in FIGS. 3 and 4. 
Preferably bracket 62 is constructed as shown in FIGS. 13-15 as a one piece 
90.degree. angle extrusion of aluminum material of 3/16 inch thickness, 
each flange of the angle piece being 2 inches wide by 4 inches long. 
The mobile hinge arm 64 of hinge sub-assembly 60 is likewise preferably of 
a one-piece aluminum extrusion construction comprising an elongated arm 
piece 80 and a mounting base 82 each 3/16 inch thick of 2 inch width. Base 
piece 82 is suitably sized to fit frame board 50 and thus is machined away 
down to a length of say 33/8 inches, whereas arm piece 80 remains 
longitudinally elongated so as to have length dimension of say 
approximately 81/2 inches. 
The distal end 84 of arm 80 is pivotally secured to mounting flange 70 of 
bracket 62 by a pivot rivet 86 inserted through aligned rivet holes 75 and 
85 in flange 70 and arm end 84 respectively located in these parts as best 
seen in FIGS. 4-9, 11, 13 and 14. The flange end of hinge arm 64 is 
secured to frame board 50 by four hex head wood screws 68 inserted through 
drilled holes 83' in flange base 32 (FIG. 12) and screwed into board 50 in 
the locations and manner shown in FIGS. 3 and 4. 
As will be evident from FIGS. 1, 3 and 4, wherein the bottom seat 34 is 
shown with front section 38 folded down to its horizontal position to 
serve as a horizontal extension of bottom seat rear section 36, front 
section 38 is gravity biased to remain in this down position with the 
straight longitudinal under edge surface 82 of arm 80 resting on the upper 
surface of the bracket base flange 66, as best seen in FIG. 4. Normally 
the weight of the padding and frame board construction of seat front 
section 38 is sufficient to maintain it relatively stable in the folded 
down position solely under the influence of the gravitational forces 
exerted from the center of gravity of the front section 38 through the 
moment arm measured to the pivot axis of arm 64 on bracket 62. 
However with the aforementioned prior art two-section fold up seat 
construction it was found that the front section 38 was not sufficiently 
so stabilized solely by gravitational biasing in the folded-up position. 
This prior art fold up two-section bottom seat construction was generally 
the same as the fold up seat bottom construction of the present invention 
to the extent described thus far, except for certain significant 
differences therebetween. The prior construction did not have the two 
screw holes 72, 74 for mounting the upper edge flange 70 of the bracket to 
the side board 42. Instead hole 72 was in the form a threaded through-hole 
which received a stud that mounted a stop block to the inner surface of 
flange 70 so that the upper longitudinal straight edge surface 90 of the 
prior pivot arm 64 abutted the edge of the stop block when arm 64 was 
positioned as shown in FIG. 8 to provide a positive arm stop for the tilt 
up and back travel of the seat front section with the longitudinal center 
line of arm 64 positioned about 5.degree. past vertical (with flange base 
66 oriented horizontally). This "over-center" position of the center of 
gravity of seat section 38 in its up position was sufficient to maintain 
it in this position when the power boat was operating in quiet-water 
conditions, and assuming the helmsman did not inadvertently knock the 
front section down by body movements while manipulating the steering wheel 
or otherwise moving about the helmsman station. However, in rough water or 
when the power boat was decelerated and/or the power boat was in a 
bow-down orientation, the minimal gravity stabilizing force for 
maintaining the seat front section in up position was found insufficient 
to hold it in this position, and instead the same would readily and 
undesirably flop down under such conditions. 
Moreover when the helmsman wished to use the front section 38 as a elevated 
seat cushion with the same in the tilted up position of FIG. 2, its 
gravity stabilization in this up position was often found insufficient to 
prevent it from flopping to the down position under the weight and 
movements of the helmsman and/or those of the water craft. 
In addition, the distal end of the arm 64 in the prior construction was 
merely radiused through 180.degree. to provide a round nose that was 
spaced with a large clearance away from the upper surface of base flange 
66 of bracket 62. Hence when the helmsman was sitting on the seat front 
section in its tilted up position, the entire weight of the helmsman was 
carried on the two pivot fasteners of the port and starboard hinge arms. 
Due to normal vibration and bouncing caused by the motion of the boat on 
the water, the pivot fasteners supporting this weight would tend to wear 
and loosen, thereby inducing rattling noises and shortening the service 
life of the pivotal frame articulation of the seat. 
The foregoing instability and wear problems of the prior art fold up 
two-section seat bottom construction were found to render the same 
generally unsatisfactory in use. Accordingly, it was necessary to 
undertake a design and engineering effort in an attempt to resolve these 
problems by providing some type of stabilizing latch system for 
maintaining the front section folded up in a stable position but without 
changing the mode of operating the fold up section for tilting it up and 
down, i.e., without the necessity of requiring the helmsman to manually 
manipulate some sort of hook latch or similar device to hold the seat 
stable in the folded up position. The pivotal frame work spring latch 
system of the invention resulted from this effort and, with a minimum 
redesign of the prior parts, overcame the aforementioned problems of the 
prior art construction while achieving the aforestated objects by 
providing several novel features which will now be described in detail. 
In accordance with one principal novel feature of the present invention, a 
one-piece stabilizing spring latch member 100 is provided on the 
stationary seat bracket 62, as shown in FIGS. 3-9. Spring latch member 100 
is mounted generally in the location of the aforementioned fixed stop 
plate, which in turn is eliminated along with its machine screw mounting 
stud and associated mounting hole in flange 70. As described in detail 
with reference to FIGS. 8 and 10, spring latch member 100 in the presently 
preferred embodiment is injection molded from suitable plastic material so 
as to have uniform thickness dimension throughout (as shown in FIG. 9). 
Alternatively, member 100 may be molded so as to have an "I" beam 
configuration in transverse cross section taken in a plane perpendicular 
to the plane of the drawing. In the side views of FIGS. 8 and 10 it will 
be seen that member 100 is an inverted generally V-shaped member that may 
be analyzed as having three functional as well as structural portions, 
namely, (1) a mounting arm portion 102, (2) a yieldably movable latch arm 
portion 104 and (3) a bight portion 106 integrally resiliently 
interconnecting the arm portions 102 and 104. As shown in FIGS. 8 and 3 
and 4 in the free state condition of member 100 the free end 108 of 
movable arm portion 104 is held spaced away from the mounting arm portion 
102, and a tapered flexing space 110 is provided between these arm 
proportions to permit flexing motion of arm portion 104 relative to the 
mounting arm portion 102 in the plane of the drawing, i.e. parallel to the 
adjacent side face of bracket flange 70. 
The mounting arm portion 102 of spring latch member 100 has a straight 
outer side surface 112 that in the mounted condition is flush with the 
side edge 114 of bracket flange 70. The bottom edge 116 of arm portion 102 
is perpendicular to side edge 112 and is adapted to seat squarely on the 
upper surface of bracket base flange 66. The inner side surface 118 of arm 
portion 102 has an included angle with edge 116 of about 65.degree. so 
that arm portion 102 has a narrowing taper, in side view, to its junction 
with bight portion 106. 
Bight portion 106 of member 100 has concentric inner and outer curved 
surfaces 120 and 122 each having a uniform radius of curvature about their 
common center of curvature (FIG. 10). Bight portion 106 extends for 
approximately 135.degree. about the center of curvature from its integral 
junction with the upper end of arm portion 102 to its integral junction 
with the upper end of movable arm portion 104. 
Movable arm portion 104 has an inner side edge 124 that defines an included 
free-state angle with the outer side edge 112 of mounting arm portion 102 
of about 53.degree. so that flexing space 110 has a divergent taper 
widening toward its mouth. The outer side edge surface 126 of movable arm 
portion 104 is configured as a camming surface having a generally convex 
configuration oriented in the travel plane of swinging motion of movable 
arm portion 104. This generally convex configuration converges at a high 
point apex A spaced upwardly a short distance from the free end edge 
surface 128 of arm portion 104(FIG. 10). Preferably the outer edge surface 
126 of arm portion 104 is made up of a long straight line portion 160 
(FIG. 10) extending from edge 122 of bight portion 106 to a curved surface 
defining apex A and having a uniform radius of curvature oriented 
tangentially with the straight section 160 and merging into another short 
straight section 162 that perpendicularly intersects the free end edge 
128. 
Spring latch member 100 is fixedly mounted on bracket 60 by a pair of pop 
rivets 130 and 132 and, as shown in FIGS. 8 and 9, with the upset ends of 
rivets oriented against the inboard face of spring latch member 100. 
Suitable through-holes 71 and 73 are provided in bracket flange 70 (FIG. 
13) and corresponding holes 75 and 77 in mounting arm portion 102 of 
member 100 (FIG. 10), these rivet holes being precision located and 
precision machined to thereby precision mount member 100 in the 
aforementioned location on bracket 60. 
Preferably spring latch member 100 is injection molded from suitable 
semi-resilient plastic material such as that sold under the trademark 
Delrin.RTM. or equivalent material, having a low coefficient of friction 
and sufficient self-lubrosity to reduce sliding friction when engaged by 
the cam follower surfaces of arm 64, as explained in more detail 
hereinafter. In the preferred but exemplarily working embodiment disclosed 
in FIGS. 1-15 and dimensioned as set forth in FIGS. 10-15 the uniform 
thickness of spring latch member 100 is about 0.25 inch. When so 
constructed and dimensioned as shown in FIG. 10 the spring rate of member 
100 is designed to provide a five pound breakaway force during the 
tilt-down operation of the front section 38 of chair 20. 
It is to be noted that the spring rate of the spring latch member 100 can 
be readily adjusted by initial design without a changing its external 
configuration or dimensions merely by molding or machining a different 
diameter into the half circle surface 120, e.g., enlarging its diameter 
over that shown will reduce the spring rate as desired by reducing the 
width dimension of the resilient portion 106 of member 100. 
In addition, when so constructed, spring latch member 100 will not corrode 
under the influence of salt air or water, and will maintain the shape of 
the concave camming surface 126 through repetitive cycling to provide a 
long operational service life. 
Moreover, in accordance with a further feature of the invention it is to be 
noted that spring latch member 100 while serving as a stabilizing spring 
for the up and down positions of arm 64 (FIGS. 8 and 4 respectively), is 
nevertheless designed such that arm 64 and the movable arm portion 104 are 
fully disengaged in both the up and down positions. Hence latch member 100 
can assume its free state condition in both of these latch positions and 
therefore is not stressed or under tension and/or compression stresses in 
the bight portion 106 of the spring in either of these positions. Because 
the plastic material of member 100 is not so loaded in either the up or 
down position, the problem of "creep", common to most if not all plastic 
materials when the same are under a constant load, is eliminated. Hence 
the operational position of movable arm portion 104 relative to hinge arm 
80 in subassembly 60 will be accurately maintained throughout a long 
service life. The effects of stress fatigue on the spring are also thereby 
greatly reduced, thereby ensuring that the spring rate of member 100 will 
remain more uniform and constant throughout its service life, and that 
such will not be prematurely foreshortened by stress fatigue failure. 
In accordance with another principal feature of the present invention the 
distal end 84 of hinge arm 64 is specially reconfigured by precision CNC 
machining or stamping die cutting its end edge surfaces to operate as a 
sliding cam follower relative to spring arm 100, and also to operate as a 
weight bearing surface in the up position of arm 64. The pivot hole 85 
(FIG. 11) in the distal end 84 of arm 64 is also precision machined to 
precision locate the cam follower edge surfaces 150, 152 and 154 of the 
distal end 84 relative to the operative portions of camming surface 104 of 
spring member 100, and in turn the precision mounting position of member 
100 is determined by the precision pop rivet holes 71 and 73 (FIG. 13) 
formed in mounting flange 70 of mounting bracket 62. The rivet hole 75 
(FIG. 13) in mounting flange 70 is also precision machined and located 
relative to holes 71 and 73. 
More particularly, referring to FIGS. 6 and 11 the cam follower means 
provided on the distal end 84 of mobile hinge arm 64 consists of a 
straight line edge surface extension 150 of the upper longitudinal edge 
surface 90 of arm 80. Surface 150 extends to a curved nose surface 152 
having a uniform radius of curvature which merges into a transverse end 
edge surface 154-156. A straight first edge surface portion 154 extends 
generally perpendicular to edge 150, but preferably defining an obtuse 
included angle of 95.degree. with edge 90 of arm 80 (FIG. 11). The camming 
follower surface provided by the transverse end edge surface of arm 80 has 
a curved second portion edge surface 156 extending smoothly from its 
merger with the first edge surface portion 154 and having a uniform radius 
of curvature to merge with a second longitudinal edge surface 83 surface 
of arm 80, namely, the underside arm longitudinal edge 83 that extends 
parallel to and opposite the upper arm longitudinal edge 90. In the 
preferred example as disclosed herein, these cam follower edge surfaces of 
the distal end 84 of arm 80 are machined or die cut to the dimensions and 
locations shown in FIG. 11. 
In accordance with a further construction and assembly feature of the 
invention, spring latch member 100 is fixedly and securely mounted to 
mounting flange 70 of bracket 62 by the aforementioned pop rivets 130, 132 
in a precision location with its lower flat edge 116 firmly seated on the 
upper surface of base flange 66 of bracket 62. In addition hinge arm pivot 
rivet 86 is installed in bracket 62 with its head 87 oriented outboard of 
bracket flange 70, as are the heads of pop rivets 130 and 132. A spacer 
washer 89 is inserted onto the shank of rivet 86 between flange 70 and arm 
64, and another washer 91 is installed between bracket 64 and the 
swedged-over portion 93 of rivet 86 (FIGS. 8 and 9). 
Preferably, the foregoing assembly of bracket hinge arm 64 and rivet 86 is 
completed at the point of manufacture of the pivot hinge sub-assembly 60, 
but the assembly of spring latch member 100 is completed at the point of 
construction of bottom seat 34. This sequence cooperates with the two 
screw mounting holes 72 and 74 in bracket flange 70 which are designed 
with their beveled counter sinks to individually receive the conical 
shoulder of a flat head screw with the outer head face of the screw flush 
with (or preferably recessed from) the inboard surface of bracket flange 
70. The provision of additional screw holes 72 and 74 thus enables bracket 
62 to be screw-secured to either, but preferably to both, the seat frame 
side board 72 and the seat bottom board 40 of the rear section 36 of the 
seat bottom 34, while carrying pop rivets 130, 132 loosely preinstalled in 
their unfinished, pre-upset condition so as to protrude inboard from 
flange 70. After so mounting bracket 62 to the seat boards with the two 
flat head screws (not shown) bottomed in their respective bracket holes 72 
and 74, arm 100 is then assembled to bracket 62 by registering and sliding 
it onto the protruding ends of the pop rivets. The pop rivets 130 and 132 
are then severed and swedged by the pop rivet tool, access to the pop 
rivet ends for the tool thus being available at the inboard side of 
bracket flange 70. It thus will also be seen that angle bracket 62 serves 
to provide a comer reinforcement for the seat construction as well having 
both of its flanges securely fastened to the seat to thereby more securely 
support hinge bracket arm 64 in use. It also enables the bracket to be 
mounted to either a vertical or a horizontal mounting surface in those 
applications where only one such surface is available. Spacer washer 89 is 
preferably made of plastic, such as that sold under the brand name 
Mylar.RTM., and serves to eliminate any metal-to-metal contact between the 
bracket flange 70 and the adjacent surface of arm 80. Spacer washer 89 
also spaces the outboard side of the arm 80 away from the heads of the 
mounting screws secured in holes 72 and 74 and hence insures arm swing 
clearance in the event that they should protrude slightly beyond flush 
condition in some assembly situations. 
The operation of the pivotal framework latch system 60 of the invention as 
applied to the improved helmsman chair 20 embodiment of the invention will 
become apparent from the foregoing description, as well as from the 
incremental sequence of positions of hinge arm 80 illustrated in sequence 
in FIGS. 5-8, as seat front section 38 is moved from its horizontal in-use 
position of FIG. 4 vertically upwardly and rearwardly over rear seat 
section 36 and vice versa. In the fully tilted down-position of front 
section 38 (FIGS. 1, 3 and 4) it will be seen that front section 38 is 
cantilever supported from the stationary seat rear section 36 by the 
starboard and port pivotal framework latch system subassemblies 60. Frame 
board 40 in turn, is conventionally affixed to the main framework of chair 
20 (not shown). In this down position the lower longitudinal edge 83 of 
arm 80 abuts the upper surface of flange base 66 which thereby serves as 
the end limit stop for downward pivotal motion on pivot rivet 86. In this 
position the movable arm portion 104 of spring latch 100 is spaced with a 
relatively large clearance away from the curved end edge surface 156 of 
arm 80 so that spring member 100 can assume its free state position and 
thereby allow the spring section 106 thereof to be in a relaxed, 
non-stressed mode. 
In this tilt down condition of seat bottom 34 the helmsman would normally 
be seated while gripping the steering wheel 26 in the normal mode of the 
sitting position with most of his weight carried on the rear seat section 
36, with the undersides of his thighs bearing on front seat section 38 and 
with his feet resting on the cabin deck floor 24. Although front section 
38 is designed in a tilt down position under normal in-use conditions to 
bear the full weight of the helmsman when in a sitting position solely on 
section 38, or even when standing thereon, most of the weight stress 
normally imparted by the seated helmsman is born by the rear seat section 
36. Accordingly gravity biasing is sufficient to maintain the front seat 
section 38 in the down position without the need for stabilization forces 
to be exerted by spring latch 100 on arm 80 with the seat front section 38 
in this position. This is true even with the bottom seat 34 vacant 
inasmuch as the weight of front section 38 alone is sufficient to maintain 
the same in the fully tilt down position of FIGS. 1, 3 and 4. Under such 
seat-vacated conditions the helmsman station is normally unoccupied and 
hence the power boat is normally not underway and thus bouncing forces are 
not being generated. 
Now when the helmsman has a need to both quickly stand up and steer, as he 
so rises from a sitting to standing position he can keep one hand on the 
steering wheel 26 and with the other hand grip front seat section 38 
anywhere along its forward edge, then easily and quickly tilt the same up 
and back to the fully tilted up position of FIGS. 2, 8 and 9. During this 
tilt up motion hinge arm cam follower surface 154 swings into initial 
contact with the straight inclined portion 160 of latch arm camming 
surface 126, as shown by the movement from the position of FIG. 4 to the 
position of FIG. 5. Thus during this first approximately 45.degree. 
increment of upward pivotal motion from horizontal, spring latch member 
100 offers no resistance to lift up of the seat front section 38. 
During the next increment of upward pivotal motion of arm 80 
counterclockwise (as viewed in FIGS. 5-8), that is, during the 
approximately of 20.degree. of rotation from the position of FIG. 5 to the 
position of FIG. 6, the small radius arm nose 152 bears slidably against 
and along straight surface 160 of camming surface 126 as arm 80 swings 
about the axis of pivot 86. During this travel cam 20.degree. engagement 
increment, hinge arm nose 152 progressively forces the latch movable arm 
portion 104 to swing toward latch mounting portion 102, thereby partially 
closing the swing clearance space 110. Due to the tapering geometry of 
spring latch member 100, wherein both of the arm portions 102 and 104 
narrow in width as they merge with the narrowest bight portion 106, most 
of the spring flexing in member 100 to accommodate this motion of arm 104 
will occur in the yieldably, semi-resilient bight portion 106 of member 
100. Thus, although all of the material of member 100 is uniformly 
resilient throughout, this design geometry of member 100 concentrates the 
spring action in bight 106. 
During the next approximately 10.degree. of angular incremental pivoting of 
arm 80, in moving from the position of FIG. 6 to the position of FIG. 7, 
the cam follower nose 152 slides further along camming surface 126 and 
further deflects arm 104 towards arm 102, as resisted by the yieldable 
biasing force of member 100, until nose 152 reaches apex A of surface 126. 
Thus is the unstable on-center position of the articulation of the camming 
engagement of the cam follower surfaces 150-156 of arm 80 relative to the 
camming surface 126 of member 100. 
When arm 80 is swung further from the position of FIG. 7 to the position of 
FIG. 8 in the last approximately 15.degree. of angular incremental pivotal 
travel, nose 152 rides down the short straight portion 162 of surface 126 
(FIG. 10). During this last increment the articulation geometry is such 
that the spring resistance forces being exerted by arm 104 through arm 
surface 162 against surface 150 of arm 80 tends to assist, rather than to 
retard, pivotal motion of the arm to its final full-up position shown in 
FIG. 8. 
Once the seat front section 38 is thus fully tilted up the arm camming 
surface 154 will abut the upper surface of a plastic abutment pad 166. Pad 
166 is adhered to the upper surface of bracket flange 66 to cover the area 
beneath surface 154 of arm 80 in the full-up position and also beneath the 
end surface 128 of arm 104. Preferably pad 166 is made of high density 
polyethylene and thus serves to prevent metal-to-metal contact between arm 
80 and flange 66. Preferably end surface 128 of arm 104 is dimensioned so 
that it is either closely spaced from or in light contact with pad 166 at 
the point of maximum deflection of arm 104 (FIG. 7). Alternatively, a 
slight interference can be provided between surface 128 and the upper 
surface of pad 166 with arm 80 in the full-up position if it is desired to 
augment the spring resistance forces developed by latch member 100. 
As a further feature of the invention, it will be seen from the foregoing 
that in the fully tilted up position of seat front section 38 (FIG. 2) the 
weight load exerted from the center of gravity of the seat front section 
38 is born primarily by the two pivot rivets 86 and transmitted therefrom 
downwardly through the vertical flanges 70 into the base flange 66 and 
then into the support board 40. However, some of the weight load is also 
carried directly from port and starboard arm 80 through the bearing of 
their end surface 154 on pad 166 into base flange 66. Pad 166 thereby 
serves as a load bearing take-up support to limit the maximum weight 
loading applied to rivets 86. Due to this feature the rivets will not be 
damaged or unduly worn when the helmsman sits or stands on front seat 
section 38 when in its fully tilted up position of FIG. 2. 
It will also be seen that seat front section 38 is stabilized and latched 
in the upright position by port and starboard spring latch members 100 
returning to their free state condition shown in FIG. 8. Surface 162 of 
each arm 104 is now positioned either closely adjacent or in light contact 
with surface 150 of the associated arm 80. Hence any tilt down forces 
exerted on front seat section tending rotate arm 80 clockwise as viewed in 
FIG. 8 will cause surface 150 to slidably abut and be opposed by the full 
strength of the spring resistance force of member 100 tending to maintain 
arm 104 in the free state condition of member 100. Note also that arm 80 
has a minimum leverage geometry in this condition. This cooperative 
latching relationship is thus fully sufficient to maintain seat front 
section 38 in the fully upright position against those inertial forces 
induced by boat motion as well as those gravitational forces exerted by 
front section 38 that act in a tilt down direction. The latching strength 
is also sufficient to maintain seat 38 upright when the helmsman sits or 
even stands on the same when it is folded up as in FIG. 2. 
However, when it is desired to purposely move front section 38 from the 
full fold-up position of FIG. 2 down to the horizontal, seat extension 
position of FIG. 1, the resistancy forces exerted by the latching action 
of springs 100 can be readily overcome by gripping the back of section 38 
and pulling it forwardly and downwardly. Preferably, the spring latch 
system is designed so that a five pound force exerted in this manner is 
sufficient to overcome the resistance of the spring latches as arms 80 are 
pivoted from their position in FIG. 8 clockwise to their position in FIG. 
7. Once pivoted this far the seat front section 38 is unlatched, whereupon 
it will be pivoted further downwardly to the fold down position of FIG. 1 
due to the weight forces exerted from the center of gravity acting around 
axis of pivot 86 as well by the "kick" exerted by arm 104 as it flexes 
from the stressed position of FIG. 7 to the free state position of FIG. 5. 
From the foregoing description it will now be apparent that the pivotal 
framework latch system, as well as the application thereof to a 
two-section fold-up seat bottom helmsman chair construction in accordance 
with the foregoing features of the invention, fully achieves the 
aforestated objects and provides many advantages over prior two-section 
articulated pivoted framework latch systems. The two spring latch members 
100 of the port and starboard pivotal framework latch system subassemblies 
60 operate conjointly and simultaneously in an additive manner to smoothly 
latch the pivot arms 80 in their upright position. From the full down 
position of front section 38 of FIG. 1 the same can be easily pivoted up 
to smoothly slidably engage the port and starboard spring latches with 
maximum leverage. From its fully tilted up position front seat section 38 
can be intentionally manually unlatched by simply rotating it to the down 
position with enough forwardly directed pull force to overcome the spring 
bias resistance forces of the latch system. The spring latch members 100 
are thus designed with enough strength to hold front section 38 securely 
in its full up position, but not so strong that they cannot be easily 
overcome to unlatch the front seat section to tilt it down when sufficient 
pull force is properly manually applied to the rear of the front seat 
section. 
Spring latch members 100 are in their free state condition in both the up 
and down position of seat front section 38 and hence are not placed under 
tension or loaded in either the up or down positions of the seat section. 
This is particularly desirable feature when latch springs 100 are made of 
semi-resilient plastic material as described previously because it 
eliminates the "creep" problem of most plastic materials that occurs when 
plastic is held under a constant load, and also reduces the likelihood 
stress-induced fatigue failure. The lubricity of the preferred Delrin.RTM. 
plastic material makes the camming slide action a smooth motion when the 
aluminum plate arms 80 are rotated up or down. The plastic spacer washer 
89 encircling rivet 86 between pivot arm 80 and bracket flange 70 
eliminates metal-to-metal contact between these moving parts. Likewise the 
plastic strip or pad 166 in the landing area of arm cam surface 154 
prevents metal-to-metal contact when a downloading is applied to seat 
front section 38 in its upright position, and also helps absorb and share 
the downward loading applied to the pivot rivets 86. 
Due to the geometry and materials of the latch system the same is 
essentially noiseless in operation and is highly corrosion resistant, 
rendering it ideal for marine usages. Preferably the hinge arm 64 and 
bracket 62 are also electrostatically coated with a powder coat of paint. 
Preferably this paint powder is an epoxy material to further enhance 
corrosion resistance as well as appearance, and preferably selected as to 
color to match that of the upholstery cover materials of chair 20. 
The latch spring members 100 can be easily attached to bracket 62 during 
seat construction after screw mounting of bracket 62 to both the bottom 
board 40 and the side board 36 of the seat rear section 36 due to the use 
of pop rivets 130, 132 that are pre-installed with their finished heads 
outboard. The latch spring member 100 can be design "tuned" by adjusting 
the cross sectional dimension of bight portion 106 (the dimension in the 
plane of drawing in FIG. 10) by precision boring or molding the desired 
radius of curvature in the inner bight surface 120. Hence the latch 
spring-to-pivot arm mounting location and external geometrical shape of 
the component parts hinge latch assembly 60 can remain fixed for ease and 
economy of manufacture, and yet the spring rate adjusted as desired by 
utilizing either a simple drilling or boring operation performed on the 
finished latch spring member 100 during the process of its separate 
production, or by simply changing a suitably dimensional insert in the 
injection mold. 
It will also be apparent to those skilled in the art from the foregoing 
description and drawings that the pivotal framework latch system of the 
invention is useful for a variety of applications other than a two-section 
bottom seat of a helmsman chair. It can be advantageously used almost 
anywhere where corrosion is a problem. It also can be used in any 
application where a pivotal framework needs to latched, for example, a 
fold up foot rest, a folding shelf hinge assembly, a door latch spring 
application, etc. It now will also be understood that different materials 
can be used for the latch spring member 100. For example, member 100 can 
be constructed solely of spring metal, or of a plastic coated metal spring 
laminate. 
It thus will be understood from the foregoing disclosure that the 
principles of the invention are applicable to a variety of pivotal 
framework latch system applications and hence the invention is intended to 
be limited only by the applicable prior art and the appended claims.