Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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INVENTION TITLE: WORKING SURFACE ADJUSTMENT
The invention is described in the following statement:-
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TECHNICAL FIELD
This invention relates to mechanisms for use in adjustably supporting a
working
surface. Though not limited thereto, the invention is particularly suited to
the
support of keyboards, drawing and painting boards, cutting and lay-up boards,
platforms for supporting work to be assembled or repaired, and the like.
Because the working surfaces are most usually horizontal or nearly so, such a
disposition will be assumed in this specification for the sake of simplicity.
It will be
appreciated, however, that the working surface or platform may be arranged
lo vertical (or at any other angle to the horizontal), as in an adjustable
back-rest.
The terms, 'up' and 'down', 'back' and 'front' are thus relative rather than
absolute
and are employed as a matter of convenience.
BACKGROUND TO THE INVENTION
The need for adjustable keyboard supports is well recognised and many
mechanisms are known in the art that allow a keyboard support platform to be
adjusted vertically and horizontally to suit the physique and working habits
of a
keyboard operator. More recently, it has come to be recognised that it is
desirable
for a keyboard to be tilted down and rearwards by up to about 15 , the exact
angle
2 o being a matter for personal preference. A rearward tilt of a keyboard is
often called
a negative angle since, for some years, it was assumed that a forward tilt -
or
positive angle - was desirable. Because of the recognised benefit of a
negative
keyboard angle, some keyboards either have a built-in negative angle or are
fitted
with foldable feet-like supports that can be used to set the board at a preset
negative angle. Accordingly, keyboard support platforms need to have a
variable
tilt angle to allow both for the personal taste of the user and the range of
keyboards on the market. Moreover, some users find that changing the keyboard
angle from time to time during the course of a working day assists in
relieving
muscle strain.
A number of mechanisms are known in the art that allow the angle of tilt of a
keyboard support platform to be adjusted in the fore-and-aft direction. Most
require
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the use of two hands and some trouble to effect an adjustment. For example, it
is
known to pivot the keyboard support platform about a horizontal axis and to
form
slotted brackets on each side to take clamping screws. To adjust such boards,
both screws need to be loosened, the platform moved to the desired angle with
one hand while the other tightens one of the clamp screws. The other screw is
then tightened. Such an adjustment is clearly most suited to the 'set and
leave'
situation. It is poorly suited to the situation where a worker needs to adjust
a
keyboard during the course of a day or when a variety of people use the one
board
and each wishes to adjust the board to his or her preference. Moreover, the
slotted
lo side brackets normally project downwardly into the knee-space and can cause
injury to the knees of the user or damage to his or her clothing.
OBJECTIVES OF THE INVENTION
It is the general object of the present invention to provide means for
adjusting the
tilt of a platform or surface that is suited for use with a keyboard support
platform
OUTLINE OF INVENTION
From one aspect the present invention comprises a mechanism for adjusting the
tilt of a work surface or platform with respect to a frame or fixture, the
platforrfi
2 o being pivotally supported cantilever-fashion from the frame or fixture so
as to
project forwardly therefrom, and the mechanism including a transversely
slidable
and manually operable cam follower located by the frame/fixture or located by
the
platform, the cam follower being adapted to engage a transversely extending
and
sloping cam surface that is located by the platform or the frame/fixture,
respectively, so that transverse movement of the cam follower causes a pivotal
tilting movement of the platform with respect to the frame or fixture. The cam
follower may be conveniently located slightly above and to the rear of the
platform,
or it may be arranged below and near the front of the platform. Preferably,
the cam
follower may be guided for transverse movement by a guide bar or slot.
The use of such a transversely sloping cam surface and cam follower can avoid
the need for clamps or other nobs and provides an immediate visual indication
of
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the angular position of the platform. It allows the tilt of the platform to be
adjusted
and re-adjusted at any time or frequency without delay or inconvenience and
can
be readily implemented without any intrusion in the space below the platform
or
frame. Furthermore, the tilting mechanism requires little if any enlargement
of the
normal fixed (non-adjustable) frame and platform arrangement.
In one form, the cam means can comprise a transversely sloping surface formed
on the front portion of the frame or on the rear portion of the platform
against
which portion of the cam follower can ride to effect the tilt of the platform,
the
1o sloping surface being located some distance in front of or behind the
transverse
axis about which the platform is pivotally mounted to the frame so that the
platform
is effectively supported by the pivotal mounting and the cam follower at the
point
where it bears upon the sloping surface. In so doing, however, the arrangement
can be such that the cam follower is placed under a compression or tension.
Mechanisms of this type are well suited for use with the type of parallel arm
linkages disclosed in my US patent 5,292,097 that can be employed for the
vertical adjustment of a keyboard support platform without the need for nobs,
levers or other clamping devices. However, the tilting mechanism of the
present
invention is also applicable to many other basic mechanisms for raising and
lowering working surfaces, for moving them toward and away from the user
and/or
for turning or swivelling them. When so used, the basic mechanism becomes the
frame that supports the tiltable platform. Alternatively, the tilting
mechanism of the
present invention may be attached directly to a fixture such as a desk, table,
wall-
bracket or the like.
DESCRIPTION OF EXAMPLES
Having broadly portrayed the nature of the present invention, various examples
will now be described by way of illustration only. In the following
description,
3 o reference will be made to the accompanying drawings in which:
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Description of the Drawings
Figure 1 is a perspective view of a keyboard support platform having a tilting
mechanism that comprises the first example.
5 Figure 2A is an enlarged partial end elevation of the support of Figure 1.
Figure 2B is a sectional end elevation of the support of Figure 1, the section
being taken on plane II-II of Figure 3.
Figure 3 is a sectional front elevation of the support of Figure 1, the
section
being taken on plane III-III of Figure 2A.
Figure 4 is a sectional side elevation of an alternative tilting mechanism to
that of Figures 1-3.
Figure 5 is a diagrammatic illustration, in front elevation, of a third type
of
mechanism suitable for use in the type of support of Figure 1.
Figure 6 is a diagrammatic illustration, in front elevation, of a fourth type
of
mechanism suitable for use in the type of support of Figure 1.
Figures 7 and 7A are diagrammatic illustrations of a fifth type of mechanism
suitable for use in the type of support of Figure 1, Figure 7 being a front
elevation and Figure 7B being a partial end elevation of Figure 7A.
Figures 8 and 8A are diagrammatic illustrations of a sixth type of mechanism
suitable for use in the type of support of Figure 1, Figure 8 being a front
elevation and Figure 7B being a partial end elevation of Figure 8A.
Figures 9 and 9A are diagrammatic illustrations of a fifth type of mechanism
suitable for use in the type of support of Figure 1, Figure 9 being a front
elevation and Figure 9B being a partial end elevation of Figure 9A.
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Referring to Figures 1-3, the first example concems a keyboard support
mechanism 10 shown in 'Figure 1 including a tiltable keyboard support
platform 12 that is pivotally attached by rivets 14 to a frame or bracket 16
that
is pivotally mounted on the ends of a parallel arm mechanism 17 for raising
and lowering keyboard platform 12. Bracket 16 is channel shaped, havinQ
vertical sides 18 and a hor'iiontal base 20. Mechanism 17 can be like any of
those dsdosed in Unted States Pa6ent No. 5,292,097, having a bw par of inks 22
and 24
pivoted to the bbttom of respective frame sides 18 by rivets 26 and 28,
io respectively, and having a channel like upper member 29 pivotally attadhed
to the top of frame sides 18 by rivets 30.
In this example a cam-follower 32 is slideably and rotatably mounted on a
horizontal crossbar 34 and runs in a slot 36 formed in platfonn 12 at tlw rear
is thereof, but in front oF, the plvot axis 37 (Figure 3) running through
rivets 14.
The lower portion of cam follower 32, which protrudes downwardly throuqh
slot 36, carries a grooved roller 38 that rides on a downwardly extending
tapered flange or cam surface 40 formed on the front edge of slot 36. (See
Figures 2B and 3). Roller 38 is free to rotate about a stub axle 42 fnced to
and
20 carried by the lower end of follower 32.
It will be seen from Figure 3 that the cam-like flange 40 is tapered, having
little or no depth at the left-hand 44 end but a substantial depth at the
right-
hand end 46. Thus, as cam follower 32 is moved from left to right, roller 38
25 rides on cam flange 40 and lifts keyboard support platform 12 up and
backwards about its axis 37 from a horizontal position (shown at 48 In broken
lines in Figures 2A and 2B. The weight of platform 12 is therefore taken by
follower 32 and crossbar 34.
30 The second example of a platform support mechanism 60 shown in Figure 4
is similar in some respects to that of Figures 1-3. A bracket 62 is pivotally
supported by link arms 64 and 66 in a similar manner to that of the first.
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example, the platform 66 again being pivotally attached to the sides 68 of
bracket 62 by rivets 70. However, in this case, platform 66 has an upturned
flange 72 at its rear extremity behind the axis of rivets 70 and flange 72 is
of
constant height (ie, it does not taper like flange 40 of the first example).
Instead, the sloping cam face is formed by the top surface 74 of the bracket
62, which rises as it extends away from the viewer in Figure 4. In this
example, the cam follower 76 is provided with a roller 78 that runs on the
edge of flange 72, the upper face of follower 76 simply sliding along the
underside of bracket top face 74 guided by a slot 78. Thus, in this case, the
cam follower 76 is held in compression by the weight of the platform 66.
It will be appreciated that the mechanism of Figure 4 can be modified to vary
the manner in which the follower 76 engages on the platform 66. For
example, flange 72 can be eliminated so that an enlarged narrow-edged
roller rides directly on the flat surface of the rear of platform 66, which is
preferably inclined upwards by about half the maximum angle of platform tilt.
A pair of outside rollers may be added to follower 76 so as to ride on the
underside of bracket 74. Also, follower 76 may be provided with a neck
flange that retains it in slot 78 in bracket 74, when the platform 66 is
lifted.
Figures 5-9 illustrate various alternative possible arrangements of cam
followers and cam faces, in each case the frame or bracket is shown at 80,
the flanged sides of the platform are shown at 82 and the rivets that
pivotally
join them together are shown at 84. In each case, a crossbar 86 is employed
for the cam follower to move along and be guided, bar 86 joining and being
supported by the sides of bracket 80. And, in each case, a second crossbar
88 joining the sides of platform 82 is mounted at an angle to the first
crossbar
86 and, thus, forms the cam surface.
In Figure 5, the cam follower 90 includes a rolling cage 92 that embraces
both corssbars and has a first pair of rollers 94 that ride on bar 86 and a
second pair of rollers 96 that ride on bar 88. In this example, platform bar
88
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is mounted in front of the pivot axis of the platform so that cage 92 of
follower
91 is held under tension by pressure on platform 82. Moving follower 90 from
left to right pulls crossbar 88 toward crossbar 86, raising the front of
platform
82.
In the example of Figure 6, the second crossbar 88 is located behind the
pivot axis of the platform so that pressure on the platform 82 tends to bring
bar 88 towards rather than away from crossbar 86. In this case the cam
follower 102 is a sliding fit on bar 86 and carries a single roller 104 that
rides
io on bar 88. Again, sliding follower back and forth along bar 86 causes
platform to tilt up or down.
In the example of Figures 7 and 7A, the cam follower 110 is also a sliding fit
on bracket crossbar 86 and embraces platform crossbar 88. Crossbar 88 is
being arranged in front of the pivot axis of platform 82, so that follower 110
is
held in tension by the weight of the platform 82. In this case, a single
roller
112 is employed and locking tabs 114 are pivotally attached to the lateral
sides of follower 110, being biased away from one another by a spring 116.
Tabs 114 have holes in their faces to accommodate crossbar 86 and serve
(under the bias of spring 116) to lock the follower 110 against sideways
movement along bar 86. To move follower 110 along bar 86, the user
presses locking tabs 114 together and then exerts sliding pressure on the
follower 110.
The example of Figures 8 and 8A is a modification of that of Figures 7 and
7A where cam follower 120 carries a central locking tab 122 that has a cam
face 124 which pinches bar 86 when moved off-centre to either side. [In this
example, platform 88 is of square section.]Thus, unless tab 122 is in either
side position, the follower 120 cannot be moved.
The example of Figures 9 and 9a shows the use of square-section crossbars
86 and 88 together with a cam follower 130 that has side locking tabs 132
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which function in the same manner as described with respect to tabs 114 of
Figures 7 and 7A. In this case, platform bar 88 is located behind the platform
pivot axis so that the bars tend to be forced together. In this case, the
weight
of the platform is borne by a cluster of three rollers 132, the upper pair of
which run on bracket bar 86 and the lower one of which runs on platform bar
88.
It will be seen from the above examples that the use of a transversely
slidable cam follower riding on a transversely sloping cam face provides a
lo neat and compact way of tilting a keyboard platform. Access to the single
control is easy and straightforward and the transverse location of the control
(part of the cam follower) provides an immediate visual indication of the
angle of tilt. Graduations in terms of degrees of tilt can be readily added to
the bracket.
However, those skilled in the art will appreciate that many alterations and
additions can be made to the examples without departing from the scope of
the invention as outlined above.
Edwin Robin Russell
by his attorney
Paul A Grant
31 May, 1999
