U.S. patent number 3,638,897 [Application Number 04/876,397] was granted by the patent office on 1972-02-01 for elevation-adjusting assembly for seat.
This patent grant is currently assigned to Coach and Car Equipment Corporation. Invention is credited to Raymond A. Bilancia, Arthur J. Harder, Jr..
United States Patent |
3,638,897 |
Harder, Jr. , et
al. |
February 1, 1972 |
ELEVATION-ADJUSTING ASSEMBLY FOR SEAT
Abstract
Seat for vehicle operator is mounted on an assembly which
automatically moves seat vertically to a selected elevation
corresponding to a setting on an elevation selector. Seat is
automatically maintained at the selected elevation regardless of
changes in the external load on the platform.
Inventors: |
Harder, Jr.; Arthur J.
(Franklin Park, IL), Bilancia; Raymond A. (Palatine,
IL) |
Assignee: |
Coach and Car Equipment
Corporation (Elk Grove Village, IL)
|
Family
ID: |
25367610 |
Appl.
No.: |
04/876,397 |
Filed: |
November 13, 1969 |
Current U.S.
Class: |
248/550; 248/631;
297/344.16; 248/585; 267/117 |
Current CPC
Class: |
B60N
2/505 (20130101); B60N 2/501 (20130101); B60N
2/507 (20130101); B60N 2/527 (20130101); B60N
2/522 (20130101); B60N 2/502 (20130101); B60N
2/525 (20130101); B60N 2/544 (20130101) |
Current International
Class: |
B60N
2/50 (20060101); B60n 001/02 () |
Field of
Search: |
;248/400,399,372,378,157
;267/131,117 ;188/88 ;297/345 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Foss; J. Franklin
Claims
What is claimed is:
1. An elevation-adjusting assembly comprising:
a base;
a platform vertically spaced in relation to said base;
means mounting said platform for vertical movement relative to said
base;
an elevation selector;
means for setting said selector at any one of a multiplicity of
positions each corresponding to a different selected elevation for
said platform;
and means, responsive to the setting of said selector, for
automatically vertically moving said platform to the elevation
selected;
said last recited means comprising:
flexible rod means bendable from a first position thereof;
said flexible rod means including means normally urging said
flexible rod means to its first position;
means for bending said flexible rod means from its first position
to another position in response to a change in the setting of said
selector;
an elevator mechanism actuable to raise or lower said platform;
means, responsive to the bending of said flexible rod means from
its first position, for actuating said elevator mechanism;
means for unbending said flexible rod means in response to movement
of said platform to said selected elevation;
and means, responsive to a return of the flexible rod means to its
first position, for deactuating said elevator mechanism.
2. As assembly as recited in claim 1, wherein said means for
actuating the elevator mechanism comprises:
means, responsive to the bending of said flexible rod means in a
first direction, for actuating said elevator mechanism to raise the
platform;
and means, responsive to the bending of said flexible rod means in
a second direction opposite said first direction, for actuating
said elevator mechanism to lower the platform.
3. An assembly as recited in claim 1 and comprising:
means for maintaining said elevator mechanism in a deactuated
condition while said flexible rod means is in its first
position.
4. An assembly as recited in claim 1, wherein said elevator
mechanism comprises:
a cylinder;
a piston within said cylinder;
means connecting said platform to the top of said piston;
a fluid passageway in said cylinder below said piston;
and means communicating said fluid passageway with a fluid
supply.
5. As assembly as recited in claim 4 and comprising:
accumulator means in fluid communication with said fluid
passageway.
6. As assembly as recited in claim 4 wherein said elevator
mechanism further comprises:
valve means including first and second depressible buttons;
and means, including said valve means, for introducing fluid into
said cylinder, through said passageway, in response to depression
of said first button and for withdrawing fluid from said cylinder,
through said passageway, in response to depression of said second
button;
said means for actuating said elevator mechanism comprising means,
attached to said flexible rod means, for depressing said first
button in response to the bending of the flexible rod means in a
first direction from its first position and for depressing said
second button in response to the bending of the flexible rod means
in a second direction from its first position, opposite said first
direction.
7. As assembly as recited in claim 6 wherein said last-recited
means comprises:
an element having one end rigidly connected to said flexible rod
means and another end pivotally mounted on said valve means;
means on said element for depressing said first button;
and means on said element for depressing said second button.
8. An assembly as recited in claim 1 wherein:
said elevation selector is fixed to said movable platform;
and said flexible rod means has one end connected to said selector
and another end connected to said base.
9. An assembly as recited in claim 8 wherein said selector
comprises;
an immovable first member attached to said platform;
a second member movably mounted on said first member;
and means connecting said second selector member to said one end of
the flexible rod means.
10. An assembly as recited in claim 8 wherein said selector
comprises;
a friction member immovably attached to said platform;
a second member;
means mounting said second member for rotation, relative to said
friction member, about an axis extending through both of said
members;
and spring means normally urging said rotatable selector member
against said friction member.
11. An assembly as recited in claim 10 and comprising:
means connecting said rotatable selector member to said one end of
the flexible rod means.
12. An assembly as recited in claim 11 wherein said connecting
means comprises:
a link member having one end pivotally connected to said one end of
the flexible rod means and another end pivotally connected to said
rotatable selector member.
13. An assembly as recited in claim 10 wherein said selector
further comprises:
a pair of angularly spaced stop means immovably attached to said
platform;
and means on said rotatable selector member for engaging said pair
of stop means to define opposite limits of rotation for the
rotatable selector member.
14. An assembly as recited in claim 1 and comprising:
shock absorber means for said movable platform;
and means for maintaining the platform at the selected elevation
regardless of changes in the external load on the platform, said
last-recited means including means, cooperating with said shock
absorber means, to permit an initial change from said selected
elevation in response to a change in said external load;
and means, responsive to a change from said selected elevation, for
automatically returning said platform to the selected
elevation.
15. As assembly as recited in claim 14 wherein:
said change-permitting means comprises means responsive to an
increase in the load on said platform for permitting a descent of
the platform below said selected elevation;
and said returning means comprises means responsive to said descent
below said selected elevation for automatically raising said
platform to said selected elevation.
16. An assembly as recited in claim 14 wherein:
said change-permitting means comprises means responsive to a
decrease in the load on said platform for automatically raising
said platform above said selected elevation;
and said returning means comprises means responsive to said raising
of said platform above said selected elevation for automatically
lowering said platform to said selected elevation.
17. A position-adjusting assembly comprising:
a first member;
a second member spaced from said first member;
means mounting said second member for movement to change the
position of the second member relative to said first member;
a positioning selector;
means for setting said positioning selector at any one of a
multiplicity of settings each corresponding to a position for said
second member;
and means, responsive to the setting of said selector, for moving
said second member to the position selected;
said last-recited means comprising:
flexible rod means bendable from a first position thereof;
said flexible rod means including means normally urging said
flexible rod means to its first position;
means, responsive to a change in the setting of said selector, for
bending said flexible rod means from its first position to another
position;
means actuable to impart said movement to said second member;
means, responsive to a bending of said flexible rod means from its
first position, for actuating said movement-imparting means;
means, responsive to movement of said second member to the selected
position, for returning said flexible rod means to its first
position;
and means, responsive to a return of the flexible rod means to its
first position, for deactuating said movement-imparting means.
18. An assembly as recited in claim 17 wherein said flexible rod
means comprises:
a first end portion connected to said positioning selector;
a second end portion connected to said means for actuating the
movement-imparting means;
and a third portion, between said two end portions, comprising a
coil spring.
19. An assembly as recited in claim 17 wherein said means for
actuating the movement-imparting means comprises:
means, responsive to the bending of said flexible rod means in a
first direction, for actuating said movement-imparting means to
move the second member in one direction;
and means, responsive to the bending of said flexible rod means in
a second direction opposite said first direction, for actuating the
movement-imparting means to move the second member in another
direction opposite said one direction.
20. An assembly as recited in claim 17 and comprising:
means for maintaining said movement-imparting means in a deactuated
condition while said flexible rod means is in its first
position.
21. An assembly as recited in claim 17 wherein said positioning
selector comprises:
a friction element immovably attached to said second member of the
assembly;
a rotatable element;
means mounting said rotatable element for rotation, relative to
said friction element, about an axis extending through both of said
elements;
and spring means normally urging said rotatable element against
said friction element.
22. An assembly as recited in claim 21 and comprising:
means connecting said rotatable selector element to one end of the
flexible rod means;
and means connecting the other end of the flexible rod means to
said first member of the assembly.
23. An assembly as recited in claim 22 wherein said first-recited
connecting means comprises:
a link element having one end pivotally connected to said one end
of the flexible rod means and another end pivotally connected to
said rotatable selector element.
24. An assembly as recited in claim 21 wherein said selector
further comprises:
a pair of angularly spaced stop means immovably attached to the
second member of the assembly;
and means on said rotatable selector element for engaging said stop
means to define opposite limits of rotation for the rotatable
selector element.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to elevation-adjusting
assemblies, and more particularly to elevation-adjusting assemblies
for seats on vehicles such as tractors or self-propelled farm
equipment, for example.
A vehicle operator's seat adjustable to various elevations is
desirable because different operators are comfortable at different
elevations and, for a given operator, the optimum operating
elevation changes in accordance with changes in operating
conditions.
Conventional vertically adjustable seats utilize an assembly
comprising a base, a seal platform located above the base and
vertically movable relative to the base, a shock absorber for the
seat platform, and a hydraulic cylinder having its bottom mounted
to the base and containing a piston movable in the cylinder and
connected to the bottom of the seat platform. Oil is introduced
into or withdrawn from the bottom of the cylinder to respectively
raise or lower the piston, inturn raising or lowering the seat
platform.
The conventional elevation-adjusting assembly has a number of
drawbacks. In order to change the elevation of the seat, the
operator must manually open a valve through which the oil passes
toward or away from the hydraulic cylinder and then manually close
the valve when the seat attains the desired elevation. If the
operator's attention is distracted so that he does not close the
valve at the instant the desired elevation is attained, the seat
will move past the desired elevation.
Another drawback is that the desired elevation cannot be obtained
when the operator is off the seat. This is because, when the
operator sits on a seat previously adjusted to a desired elevation
with the operator off the seat, the seat is depressed by the weight
of the rider to a lower elevation.
A further drawback is that, when the operator gets off the seat,
thereby reducing the external load on it, the seat springs or
rebounds to a higher elevation. When the seat rebounds to a higher
elevation it crowds the space between the seat and the steering
wheel of the vehicle, and this is undesirable to an operator who is
temporarily standing in this space while steering.
The rebound of the seat to a higher elevation also causes problems
for a short operator who has to climb up on a seat which has
rebounded to a higher elevation.
Changes in seat elevation in response to changes in the external
load on the seat resulted from the conventional provision of a
shock absorber for the seat (e.g., an accumulator connected to the
hydraulic cylinder). To return the conventional vertically
adjustable seat to the selected elevation required a manual
manipulation of the elevation controls by the vehicle operator.
SUMMARY OF THE INVENTION
A seat with an elevation adjustment assembly, in accordance with
the present invention, eliminates the drawbacks of conventional
assemblies.
The desired elevation for the seat may be selected with the
operator either on or off the seat, and the seat will automatically
adjust to the selected elevation. The operator is not required to
manually close a valve at the instant the seat reaches the desired
elevation. A selector is manually set at the desired elevation, and
this is the only manual operation required. Once the selector is
set, the assembly automatically adjusts to the selected elevation;
and the selected elevation will be automatically maintained
regardless of changes in the external load on the seat.
If the elevation is selected and the adjustment occurs while the
operator is off the seat, and the operator then sits on the seat,
there is a momentary descent of the seat, but the selected
elevation is automatically reattained. When the operator gets off
the seat, there is a momentary upward rebound, but the seat is
automatically returned to the selected elevation. Therefore, an
operator standing between the seat and the steering wheel is not
crowded by a seat which has rebounded to a higher elevation.
Similarly, a little man doesn't have to climb up to a seat which
has rebounded to a higher elevation.
Other features and advantages are inherent in the structure claimed
and disclosed or will become apparent to those skilled in the art
from the following detailed description in conjunction with the
accompanying diagrammatic drawing.
BRIEF DESCRIPTION OF DRAWING
FIG. 1 is a perspective of an elevation-adjusting assembly for a
seat, in accordance with an embodiment of the present
invention;
FIG. 2 is another perspective of the assembly, partially cut
away;
FIG. 3 is a side elevational view illustrating the assembly at an
intermediate elevation with an elevation selector positioned to
maintain the assembly at the intermediate elevation;
FIG. 4 is a side elevational view of the assembly at an
intermediate elevation with the selector positioned to increase the
elevation;
FIG. 5 is a side elevational view showing the assembly at a
relatively high elevation with the selector positioned to maintain
the relatively high elevation;
FIG. 6 is a side elevational view showing the assembly at a
relatively high elevation with the selector positioned to lower the
elevation;
FIG. 7 is a side elevational view showing the assembly at a
relatively low elevation with the selector positioned to maintain
the assembly at the relatively low elevation;
FIG. 8 is a fragmentary front view, partially in section, showing
an elevation selector constituting part of the elevation
assembly;
FIG. 9 is a fragmentary side view showing the elevation
selector;
FIG. 10 is a fragmentary side view showing valve structure
constituting part of the assembly; and
FIG. 11 is a schematic diagram of a hydraulic system used in the
assembly.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Referring initially to FIGS. 1-3, indicated generally at 20 is an
embodiment of an elevation-adjusting assembly for a seat, in
accordance with the present invention.
Assembly 20 includes a base 21, a seat platform 22 located above
the base and means, including pairs of upper and lower pivotal
links 23,24, respectively, mounting platform 22 for vertical
movement relative to base 21. Assembly 20 also includes an
elevation selector indicated generally at 25 and a handle 26 for
setting the selector 25 at any one of a multiplicity of positions
each corresponding to a different selected elevation for platform
22. In response to the setting of selector 25 at one of these
positions, platform 22 is automatically vertically moved to the
elevation selected and is automatically maintained at the selected
elevation regardless of changes in the external load on platform
22.
Base 21 comprises a pair of horizontally extending, L-shaped
members 30, attached to a vehicle floor 31 (FIG. 3) by fasteners
32. Extending between the front end of base members 30, 30 is a
crossmember 34 (FIG. 2). Extending upwardly from the back ends of
horizontal base members 30, 30 are vertical base members 35, 35;
and extending between the upper ends of vertical base members 35,
35 is a crossmember 37. Also extending between vertically disposed
base members 35, 35 are a pair of vertically spaced horizontal rods
38, 39.
Each pivotal link 23, 24 has its back end pivotally mounted on a
respective rod 38, 39 and its front end pivotally mounted on a
respective one of a pair of vertically spaced rods 40, 41 extending
between a pair of vertically disposed platform members 42, 42 each
depending from the front end of a horizontally disposed platform
member 43, 43. Extending between the upper ends of vertically
disposed platform members 42, 42 is a crossmember 44, and extending
between the back ends of horizontally disposed platform members 43,
43 is a crossmember 45. Extending between upper links 24, 24 is a
stabilizing member 46 (FIG. 1).
Resting atop horizontally disposed platform members 43, 43 is a
seat shown in phantom lines at 50 in FIG. 3.
Referring to FIGS. 1-3 and 8-9, elevation selector 25 is fixed to
movable seat platform 22 by a bracket member 52 having a vertically
disposed portion 53 to which is fixed a vertically disposed
selector friction member 54 composed of material conventionally
used on clutch discs. Engaging friction member 54 is a movable
selector member 55 to which handle 26 is attached. A bolt 56
extends horizontally through vertically disposed bracket portion
53, through selector friction member 54 and through selector
movable member 55. Selector movable member 55 is rotatable,
relative to selector friction member 54, about the axis of bolt
56.
Selector movable member 55 is urged against selector friction
member 54 by a coil spring 57 located between movable selector
member 55 and a washer 58 held in place by a nut 59 screwed onto
bolt 56. Nut 59 may be tightened or loosened to compress or expand
coil spring 57 to adjust the pressure urging rotatable selector
member 55 against selector friction member 54. The pressure on
rotatable selector member 55 is adjusted to permit rotation of of
member 55 by manually moving handle 26, while holding member 55 in
place against rotational movement, relative to selector friction
member 54, in the absence of manual movement of handle 26 to select
a new elevation setting.
Immovably attached to vertically disposed bracket portion 53 and
bracket member 52 respectively, are a pair of angularly spaced
stops 60, 61. Radially extending from movable selector member 55 is
a projection 62 for engaging stops 60, 61 to define the opposite
limits of rotation for rotatable selector member 55.
Referring to FIG. 9, stops 60, 61 are in the form of bolts threaded
through nuts 105, 106 respectively fixed to small projections 107,
108 extending respectively from vertically disposed bracket portion
53 and from bracket member 52. This arrangement permits adjustment
of the distances stops 60, 61 extend inwardly from projections 107,
108, in turn permitting adjustment of the angle through which
rotatable member 55 may be rotated.
Movable selector member 55 is connected by a linkage to elevating
mechanism actuable to raise or lower platform 22. The elevating
mechanism comprises a valve 81 mounted on base 21 by a pair of rods
82, 83 having outer ends attached to valve 81 and inner ends
attached to a bracket 84 fixed to vertically extending base member
35. Valve 81 is actuable to introduce or withdraw hydraulic fluid
into a hydraulic cylinder 90 to raise or lower a piston 91 (FIG.
11) from which upwardly extends a piston rod 92 connected to seat
platform 22. As piston 91 and piston rod 92 move upwardly or
downwardly, seat platform 22 moves correspondingly. Cylinder 90 is
pivotally mounted on base 21 at 93 (FIG. 3).
The linkage connecting elevation selector 25 to the elevating
mechanism will now be described, with reference to FIGS. 1-3. Fixed
to rotatable selector member 55 is a radially extending projection
70 having an outer end pivotally connected at 72 to one end of a
link member 73 having another end pivotally connected at 74 to a
rigid first end portion 75 of a flexible rod 76 having a coil
spring center portion 77 integral with rigid first end portion 75
and with a rigid second end portion 78 connected to a
channel-shaped valve actuator 79 pivotally connected at 80 to valve
81.
Referring to FIGS. 10 and 11, valve 81 is of conventional
construction and comprises a first button 94 depressible to cause
valve 81 to direct fluid from a fluid supply (not shown) via a
supply line 95 through valve 81 to hydraulic cylinder 90 via a line
96 communicating valve 81 with a passageway or opening 97 in
cylinder 90 below piston 91. Button 94 is depressed by a first
projection 98 extending inwardly from the web 99 of channel-shaped
valve actuator 79.
Valve 81 also includes a second bottom 100 depressible to cause
valve 81 to direct fluid from cylinder 90 via line 96 through valve
81 to the fluid supply via a return line 101. Button 100 is
depressed by a second projection 102 extending inwardly from web 99
of channel-shaped valve actuator 79.
Projections 98 and 102 are in the form of bolts threaded through
nuts 103, 104 fixed to the outside of web 99. This arrangement
permits adjustment of the distances projections 98 and 102 extend
inwardly from web 99 toward their respective depressible
buttons.
Structure for connecting piston rod 92 to seat platform 22 is
illustrated in FIGS. 1 and 2. At the top of upwardly extending
piston rod 92 is a head 110, and on opposite sides of head 110 are
a pair of pivotal connections 111, 112 having a common axis and
connecting head 110 to the inner ends of a pair of links 113, 114
having outer ends attached to crossmember 44 of platform 22.
The operation of the election adjusting assembly can be
conveniently understood by referring to FIGS. 3 through 7.
FIG. 3 shows seat 50 and platform 22 at an intermediate elevation
corresponding to the setting of elevation selector 25 shown in FIG.
3. At an intermediate elevation setting, selector projection 62 is
located between stops 60, 61.
To elevate seat platform 22 and seat 50, handle 26 is pushed
forwardly from the position shown in FIG. 3 to the position shown
in FIG. 4, for example. The position of handle 26 in FIG. 4 is that
which will cause raising of seat platform 22 to its highest
elevation, it being noted that, in FIG. 4, limit projection 62 on
rotatable selector member 55 engages stop 60. When handle 26 is
moved to the position of FIG. 4, rotatable selector member 55 and
radially extending linkage projection 70 are rotated from the
positions shown in FIG. 3 to the positions shown in FIG. 4, and
this causes a change in the position of the linkage 73, 76, 79
connecting elevation selector 25 to valve 81. Flexible rod 76 is
bent downwardly, from the straight position shown in FIG. 3 to the
bent position of FIG. 4. As flexible rod 76 bends, valve actuator
79 is pivoted in a counterclockwise sense about axis 80 until
actuator projection 98 engages and depresses button 94 on valve 81.
Depression of valve button 94 causes flow of hydraulic fluid from
the fluid supply through line 95, through valve 81, through line 96
and through passageway 97 into hydraulic cylinder 90 below piston
91 (FIG. 11). Flow of fluid into cylinder 90 forces piston 91 and
piston rod 92 upwardly, in turn elevating seat platform 22
connected to the top of piston rod 92.
As illustrated in FIG. 11, hydraulic fluid flowing through line 96
also passes through a connector conduit 116 into a conventionally
constructed accumulator 115 which serves as a shock absorber for
seat platform 22. Accumulator 115 includes a bladder 117 separating
an accumulator lower compartment 118, for containing hydraulic
fluid, from an accumulator upper compartment 119 for containing a
gas such as air. The flow of fluid into lower accumulator
compartment 118 urges flexible bladder 117 upwardly into upper
compartment 119 compressing the gas therein.
As seat platform 22 is elevated from the position shown in FIG. 4
it eventually reaches the position shown in FIG. 5 in which
flexible rod 76 is in a straight unbent position. As flexible rod
76 is returned to its unbent position, valve actuator 79 is pivoted
in a clockwise sense about axis 80 until projection 98 no longer
engages button 94, as shown in FIG. 5. When this occurs, the flow
of fluid from the fluid supply to cylinder 90 stops.
Seat platform 22 and seat 50 are maintained in a selected elevation
corresponding to the setting of elevation selector 25 regardless of
changes in the external load on the seat. For example, assuming the
seat is at the elevation shown in FIG. 5 and the load on seat
platform 22 is increased by a heavier operator sitting on the seat,
there is initially a momentary descent of platform 22 and of all
the elements connected thereto including elevation selector 25 and
link 73 connecting selector 25 to flexible rod 76. This causes a
bending of flexible rod 76 downwardly, to a position like that of
flexible rod 76 in FIG. 4. When this occurs, projection 98 on valve
actuator 79 is pivoted into engagement with depressible button 94
on valve 81, causing hydraulic fluid to be introduced into cylinder
90 to raise platform 22. Raising of platform 22 continues until
depressible button 94 is no longer engaged by projection 98 on
valve actuator 79. This occurs when flexible rod 76 has been
returned to its unbent position illustrated in FIG. 5; and that
happens when seat platform 22 has been returned to the elevation
illustrated in FIG. 5. 5.
On the other hand, if a load is removed from seat platform 22, for
example by an operator getting off the seat, seat platform 22 would
momentarily rebound upwardly due to the urging of the compressed
air in upper compartment 119 of accumulator 115 (FIG. 11). More
specifically; the compressed air forces flexible bladder 117
downwardly in turn forcing hydraulic fluid out of lower accumulator
compartment 118 through connector conduit 116 and line 96 into the
bottom of cylinder 90, thereby causing piston 91 and piston rod 92
to move upwardly and raise seat platform 22.
However, as seat platform 22 is being raised there is an
accompanying upward movement of all the elements connected to seat
platform 22 including elevation selector 25 and line 73; and this
bends flexible rod 76 upwardly from the position shown in FIG. 5.
That is, the rod's first rigid end portion 75 is substantially
higher than the rod's second rigid end portion 78, connected to
valve actuator 79, with the rod's central coil spring portion 77
curved upwardly from right to left (e.g., as in FIG. 6).
When rod 76 is bent upwardly, valve actuator 79 is pivoted about
axis 80 in a clockwise sense until projection 102 thereon engages
depressible button 100 on valve 81. Depression of button 100 causes
hydraulic fluid to flow from cylinder 90 through the opening 97
therein, through line 96, through valve 81 and through line 101
back to the fluid supply. As fluid is withdrawn from cylinder 90,
the weight of seat platform 22 and the elements attached thereto
pushes piston 91 downwardly causing the platform to drop and
flexible rod 76 to unbend. As flexible rod 76 unbends, valve
actuator 79 rotates about axis 80 in a counterclockwise sense until
projections 102 no longer engages depressible button 100, and this
occurs when flexible rod 76 is in the unbent position of FIG. 5.
When depressible button 100 is no longer engaged by projection 102,
fluid no longer flows out of hydraulic cylinder 90, and the
downward movement of seat platform 22 stops.
To lower seat platform 22, handle 26 is moved rearwardly, for
example from the position of FIG. 5 to the position illustrated in
FIG. 6. When handle 26 is moved rearwardly, the linkage connecting
elevation selector 25 with flexible rod 76 causes the rod to be
bent upwardly as illustrated in FIG. 6, in turn rotating valve
actuator 79 about axis 80 in a clockwise sense and causing
projection 102 to engage depressible valve button 100 in turn
causing the flow of fluid from cylinder 90 back to the fluid
supply, as previously described. As fluid is withdrawn from
cylinder 90, seat platform 22 drops; and, as the platform drops,
flexible rod 76 is returned to its unbent position. As rod 76
unbends, valve actuator 79 rotates about axis 80 in a
counterclockwise sense until projection 102 no longer engages
depressible valve button 100; and, when this occurs, withdrawal of
fluid from cylinder 90 ceases. Projection 102 is disengaged from
depressible button 100 when flexible rod 76 has returned to its
unbent position, as illustrated in FIG. 7. At the same time, seat
platform 22 has descended to the elevation corresponding to the
setting of elevation selector 25. In FIG. 7, the elevation is the
lowest one for the platform because projection 62 on movable
selector member 55 engages lower limit stop 61.
From the foregoing, it will be noted that, whenever flexible rod 76
is bent, there is an automatic adjustment of the elevation of seat
platform 22. If flexible rod 76 is bent as a result of a change in
the setting of elevation selector 25, there will be a change in the
elevation at which seat platform 22 is maintained. If flexible rod
76 is bent while the setting of the elevation selector remains
unchanged, as occurs when there is a change in the external load on
seat platform 22 changing the elevation thereof, seat platform 22
will be automatically returned to the elevation corresponding to
the setting of elevation selector 25.
The mechanism for changing the elevation of the seat platform is
actuated in response to a bending of flexible rod 76 and is
deactuated in response to a return of the flexible rod to its
unbent position. When flexible rod 76 is bent upwardly (FIG. 6),
the elevation mechanism is actuated to lower seat platform 22;
whereas, when flexible rod 76 is bent downwardly (FIG. 4) the
elevation mechanism is actuated to raise platform 22. Flexible rod
76 is normally urged to its unbent position by coil spring central
portion 77.
* * * * *