Abstrict The invention provides an adjustable bed frame having a main support
including head and foot ends. The support is movable between raised
and lowered positions and independent first and second elevating
mechanisms are coupled to the main support. The mechanisms are spaced
from one another on the main support to carry the bed frame on a
support surface. An electrical supply system provides power to actuate
the mechanisms to change the height of the main support above the
support surface and a controller is coupled to the supply system
to selectively activate the first and second elevating mechanisms
to move the main support between raised and lowered positions. DC
motors and worm drives are used independently to drive the elevating
mechanisms and stops are provided at the raised and lowered positions
to ensure that the main support is horizontal in the raised and
lowered positions.
Claims What is claimed is:
1. An adjustable bed frame including:
an elongate main support extending longitudinally and having head
and foot ends and moveable between raised and lowered positions;
an independent first elevating mechanism coupled to the main support;
an independent second elevating mechanism coupled to the main support
and spaced from the first elevating mechanism to combine with the
first elevating mechanism to carry the main support on a support
surface;
an electrical supply system coupled to the first and second elevating
mechanisms to provide power to actuate the mechanisms to change
the height of the main support above said support surface between
the raised and lowered positions;
a controller coupled to the supply system to selectively activate
the first and second elevating mechanisms to move the main support
between raised and lowered positions; and
each of the first and second elevating mechanisms including a DC
motor and a worm drive coupled to the DC motor, the worm drive having
stops corresponding to said raised and lowered positions so that
on using the controller to move the independent first and second
elevating mechanisms to bring the main support into said raised
or lowered positions, the worm drives will meet the corresponding
stops to ensure the main support is horizontal in the raised and
lowered positions,
each of the first and second elevating mechanisms includes pairs
of outer and inner links arranged in parallel, the outer links being
rotatable about transverse first axes above the main frame, the
inner links being rotatable about transverse second axes vertically
below the corresponding first axes and below the main frame, and
the respective pairs of inner and outer links of the first and second
elevating mechanisms extending from the associated first and second
axes away from one another.
2. An adjustable bed frame as claimed in claim 1 in which the pairs
of inner and outer links of the first elevating mechanism are pivotally
coupled to respective first upright elements, the first elevating
mechanism including a pair of wheels attached one to each of the
first upright elements for engagement on the support surface, and
in which the inner and outer links of the second elevating mechanism
are pivotally coupled to second upright elements, the second elevating
mechanism including a pair of feet attached to the second upright
elements for engagement on the support surface to locate the bed
frame on the support surface as the main support is moved between
the raised and lowered positions, the wheels providing horizontal
movement over the support surface to accommodate angular motion
of said outer and inner links in the first and second elevating
mechanisms.
3. An adjustable bed frame as claimed in claim 2 in which said
inner and outer links are parallel to the elongate main support
and adjacent the main support with the main support in the lowered
position.
4. An adjustable bed frame as claimed in claim 2 in which said
outer links of the first and second elevating mechanisms are horizontal
with the main support in the lowered position.
5. An adjustable bed frame as claimed in claim 4 in which the outer
links extend from the respective first axes towards the respective
head and foot ends of the main support with the main support in
the lowered position.
6. An adjustable bed frame including:
an elongate main support extending longitudinally and having head
and foot ends and moveable between raised and lowered positions;
an independent first elevating mechanism coupled to the main support;
an independent second elevating mechanism coupled to the main support
and spaced from the first elevating mechanism to combine with the
first elevating mechanism to carry the main support on a support
surface;
an electrical supply system coupled to the first and second elevating
mechanisms to provide power to actuate the mechanisms to change
the height of the main support above said support surface between
the raised and lowered positions;
a controller coupled to the supply system to selectively activate
the first and second elevating mechanisms to move the main support
between raised and lowered positions; and
each of the first and second elevating mechanisms including pairs
of outer and inner links arranged in parallel, the outer links being
rotatable about transverse first axes above the main frame, and
the inner links being rotatable about transverse second axes positioned
below the corresponding first axes below the main frame such that
with the bed frame in the lowered position the respective pairs
of first links are in horizontal alignment adjacent to and immediately
above the main support and the respective pairs of second links
are in horizontal alignment adjacent to and immediately below the
main support.
7. An adjustable bed frame as claimed in claim 6 in which with
the main support in the lowered position there is a clearance between
the support surface and the main support between the first and second
elevating mechanisms for receiving equipment such as a patient lifting
structure.
8. An adjustable bed frame as claimed in claim 6 in which the respective
first and second elevating mechanisms extend from the associated
first and second axes towards the respective head and foot ends
of the main support.
9. An adjustable bed frame as claimed in claim 8 in which the pairs
of inner and outer links of the first elevating mechanism are pivotally
coupled to respective first upright elements, the first elevating
mechanism including a pair of wheels attached one to each of the
first upright elements for engagement on the support surface, and
in which the inner and outer links of the second elevating mechanism
are pivotally coupled to second upright elements, the second elevating
mechanism including a pair of feet attached to the second upright
elements for engagement on the support surface to locate the bed
frame on the support surface as the main support is moved between
the raised and lowered positions, the wheels providing horizontal
movement over the support surface to accommodate angular motion
of said outer and inner links in the first and second elevating
mechanisms.
10. An adjustable bed frame as claimed in claim 9 in which the
wheels are adjacent the head end of the main support and the feet
are adjacent the foot and of the main support with the main support
in the lowered position.
11. An adjustable bed frame as claimed in claim 10 and further
including a castor assembly coupled to the main support adjacent
the second elevating mechanism and having a pair of castors which
contact the support surface only when the main support is moved
into the lowered position so that in the lowered position the bed
frame is supported on the wheels and castors to facilitate moving
the bed frame on the support surface.
12. An adjustable bed frame as claimed in claim 8 and further including
a castor assembly coupled to the main support adjacent the second
elevating mechanism and having a pair of castors which contact the
support surface only when the main support is moved into the lowered
position so that in the lowered position the bed frame is supported
on the wheels and castors to facilitate moving the bed frame on
the support surface.
13. An adjustable bed frame as claimed in claim 6 in which with
the main support in the lowered position, the bed frame has a height
above the support surface of about 16.2 cm.
14. An adjustable bed frame as claimed in claim 13 in which the
clearance under the main support between the first and second elevating
mechanism is about 5.4 cm.
15. An adjustable bed frame as claimed in claim 6 in which each
of the first and second elevating mechanisms including a DC motor
and a worm drive coupled to the DC motor, the worm drive having
stops corresponding to said raised and lowered positions so that
on using the controller to move the independent first and second
elevating mechanisms to bring the main support into said raised
or lowered positions, the worm drives will meet the corresponding
stops to ensure the main support is horizontal in the raised and
lowered positions.
Description FIELD OF THE INVENTION
This invention relates to adjustable beds and more particularly
to bed frames used in such beds. The bed frames are of the type
which provide for elevation of a main support between raised and
lowered positions and are particularly suitable for use by patients
who require that the bed be lowered into a minimal height position.
BACKGROUND OF THE INVENTION
Adjustable bed frames are available in many forms. Mechanisms used
to elevate and lower the bed frames include electro-mechanical,
pneumatic, cable and pulley, and various devices involving a variety
of mechanical linkages. In general, the structures include a main
support and a pair of mechanisms located at the respective head
and foot ends of the main support. The mechanisms are operable to
change the elevation of the main support and in some cases to change
the longitudinal orientation of the main support relative to horizontal.
Such structures are often complicated require mechanical interconnection
between the mechanisms to ensure that during elevation the main
support is maintained in a fixed relationship to the horizontal.
The present invention is intended to provide an adjustable bed
frame capable of being lowered as close to a support surface as
possible while providing access under the bed frame for the feet
of a patient lifting device and also maintaining the option of elevating
the bed fame into a normal position for use.
SUMMARY OF THE INVENTION
In one of its aspects the invention provides an adjustable bed
frame having a main support including head and foot ends. The support
is movable between raised and lowered positions and independent
first and second elevating mechanisms are coupled to the main support.
The mechanisms are spaced from one another on the main support to
carry the bed frame on a support surface. An electrical supply system
provides power to actuate the mechanisms to change the height of
the main support above the support surface and a controller is coupled
to the supply system to selectively activate the first and second
elevating mechanisms to move the main support between raised and
lowered positions.
Preferably each of the first and second elevating mechanisms includes
a DC motor and a worm drive coupled to the DC motor. The worm drive
has stops corresponding to the raised and lowered positions so that
on using the controller to move the independent first and second
elevating mechanisms to bring the main support into said raised
or lowered positions, the worm drives will meet the corresponding
stops to ensure the main support is horizontal in the raised and
lowered positions.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partially exploded isometric view of a bed frame according
to the invention and ready to receive a mattress support structure,
the bed frame being shown in a raised position;
FIG. 2 is a side view of the bed frame showing the mattress support
structure in ghost outline and indicating movement of parts of the
bed frame when moving from the raised position (as shown) towards
a lowered position; and
FIG. 3 is a view similar to FIG. 2 and showing the bed in the lowered
position.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Reference is first made to FIG. 1 to describe a bed frame designated
generally by the numeral 20. The bed frame is shown in a raised
position about to receive a headboard 22 and footboard 24 and consists
essentially of an elongate main support 22 carried by a pair of
first and second independent elevating mechanisms 24 26 powered
by an electrical supply system 28. A controller is connected to
the supply system 28 to permit a user to elevate and lower the bed.
The independent elevating mechanisms 24 26 are similar but differ
in detail as will be explained. The movements of the mechanisms
24 26 are independent in the sense that they are not mechanically
connected but are driven simultaneously by the electrical supply
system 28 when directed to do so by the controller 30. They independently
meet raised and lowered positions so that if one of the mechanisms
24 26 lags behind the other sightly, the mechanisms will reset
on meeting either the raised or the lowered positions. This will
be more fully explained later.
Returning to the structure of the bed frame, it will be seen that
the main support 22 consist of inverted L-shaped side members 32
34 extending longitudinally and arranged in parallel and defining
the length of the bed frame. The side members 32 34 have respective
head and foot ends meeting corresponding channel-sectioned head
and foot members 36 38 which define respective slots 40 42. Brackets
44 46 on the respective head and footboards 22 24 are made to
slide vertically into the respective slots 40 42 so that the head
and footboards can be dropped into place by engagement of the brackets
44 46 in the slots 40 42 and removed by reversing the procedure.
Reference is next made to FIGS. 1 and 2 to describe the elevating
mechanism 24 which is similar to the elevating mechanism 26 but,
as mentioned previously, differs in detail. Once the mechanism 24
has been described, the differences between that mechanism and mechanism
26 will be explained.
The mechanism 24 has a parallel linkage which is attached to the
side members 32 34 at respective trunnions 48 50 mounted above
the side members 32 34 and at a pair of bearing blocks 52 54 mounted
below the trunnions 48 50 on the underside of the side members
32 34. The elevating mechanism 24 is also attached at a pivot block
56 which can be better seen in FIG. 2. This block is attached to
the head member 36.
The mechanism 24 includes parallel outer links 58 60 connected
by a transversely extending shaft 62 which is fixed to the outer
links 58 60 and passes through the trunnions 48 50 to permit rotation
of the assembly relative to the axis of the shaft 62. Similarly,
a pair of inner links 64 66 are independently pivotally attached
to the respective pivot bearing blocks 52 54 and the inner links
64 66 are fixed in relation to one another by a transverse member
68 welded to the links. Unlike the outer links 58 60 the inner
links 64 66 are not straight. The links 64 66 are cranked outwardly
below the transverse member 68 in order to bring the lower ends
(as drawn) of the inner links 64 66 into alignment with the corresponding
ends of the outer links 58 60 to facilitate pivotal attachment
to upright elements 70 72. These elements carry respective wheels
74 76 mounted on a transverse axis and a bumper rail 78 is provided
to locate the bed against a wall when the bed is in the lowered
position as will be described with reference to FIG. 3.
The outer links 58 60 and inner links 64 66 are rotatable about
respective transverse first and second parallel axes 80 82 positioned
one above the other. The axes 80 82 are arranged so that the upright
elements 70 72 are maintained in a vertical orientation as the
outer and inner links rotate about the respective axes 80 82. Consequently
the wheels 74 76 are continuously in contact with the support surface
regardless of the orientation of the outer and inner links 58 60
and 64 66.
The elevating mechanism 24 also includes an electrically driven
actuator 84 connected to the pivot block 56 and to a pair of cranks
86 attached to the shaft 62. The actuator 84 is pivotally connected
between the cranks 86 so that operation of the actuator 84 will
create a turning force around the axis 80 and this will drive the
mechanism 24 to either raise or lower the main support 22. The actuator
84 includes a DC motor 88 which receives DC power from the supply
system 28 which has a connection lead 90 to receive AC power. The
system 28 converts AC input to DC output to supply the motor 88.
In turn, the motor powers a worm drive 92 which causes a rod 94
to move linearly outwardly and inwardly thereby rotating the cranks
86. It will now be evident from FIG. 2 particularly, that operation
of the actuator 84 can cause the outer links 58 60 to rotate about
the axis 80. The inner links 64 66 act as slave links in that they
simply maintain the relationship of the upright elements 70 72
as the links 58 60 are driven to move angularly.
The actuators 84 are preferably made by Linak A/S of Denmark, Model
No. LA31.
The actuator 84 has a high mechanical advantage so that it is capable
of lifting heavy loads which could be found for instance when a
patient or visitor sits on the end of a bed. This extreme situation
will not normally exist when changing the elevation of the main
support, but nevertheless, the actuator 84 is designed to change
the elevation of the bed in such conditions. Before discussing this
in detail, the mechanism 26 will be described.
Those parts in mechanism 26 which are similar to those described
with reference to mechanism 24 will be indicated with numerals which
are similar to those in mechanism 24 but increased by 100. For instance,
outer link 60 in mechanism 24 has a corresponding link 160 in mechanism
26. The differences between mechanisms 24 and 26 lie in the slightly
different purpose given to the mechanism 26. Whereas the mechanism
24 always has the wheels 74 76 on the support surface, mechanism
26 includes a pair of upright elements 96 (one of which can be seen)
which terminate in padded feet 98 which are shown resting on the
support surface to locate this mechanism on the support surface.
Consequently, when the bed is moved vertically, the resulting change
in length between the wheels 74 76 and the padded feet 98 is accommodated
by the wheels 74 76 rolling on the support surface (as indicated
in FIG. 2) while the padded feet 98 remain stationary on the support
surface. This will be more fully explained with reference to FIG.
3.
The mechanism 26 does not include wheels but a castor assembly
100 is provided attached to the main support 22 and including castors
102 104 which will only come into contact with the support surface
when the bed frame is in the lowered position as shown in FIG. 3.
FIG. 2 also illustrates in ghost outline how a mattress support
106 is assembled on the main support 22 and includes the usual adjustments
for Trendelenburg positions.
Reference is next made to FIGS. 2 and 3 to describe how the bed
frame is adjusted to change the height of the main support. It will
be seen in FIG. 2 that the main support 22 is in an elevated condition
in which the mechanisms 24 26 have been activated by rotating the
respective cranks 86 186 about respective axes 80 180 thereby
rotating the outer links 58 60 and 158 160. The first upright
elements 70 72 and second upright elements 96 are maintained in
a vertical orientation as was described previously by the combination
of the associated links. The bed frame is supported on the wheels
74 76 and on the padded feet 98 which engage the floor to limit
the likelihood of accidental movement.
When it is desired to lower the main support 22 the controller
30 is actuated which in turn causes power to be provided through
the supply system 28 to the DC motors 88 188. The result is that
the worm drives 92 192 operate to withdraw the shafts 94 194 thereby
turning the cranks 86 186 so that the wheels 74 76 will move to
the left as shown in FIG. 2 and the main support 22 of the bed frame
20 will be lowered as this happens. The movement will continue until
the actuators 84 184 reach the ends of their travels, which may
be exactly at the same moment, or there could be a slight lag one
after the other. This possible lag is immaterial because the actuators
will continue independently to meet their individual limits to travel
resulting in the main support reaching the position shown in FIG.
3. In this position, the movement of the actuator 26 is such that
the padded feet 98 are raised slightly off the support surface as
the castors 102 104 come into play. The bed is then supported on
these castors and on the permanently supporting wheels 74 76 in
the mechanism 24. The bed can now be moved in any direction because
the castors 102 104 can rotate about respective vertical axes as
they roll on the support surface.
FIG. 3 illustrates an important aspect of the invention. As seen
in this figure, links 60 and 160 are in horizontal alignment and
positioned slightly above a plane containing the upper surface of
the side member 34. Similarly, the inner links 66 and 166 are also
in horizontal alignment and positioned below the side member 34.
It will be appreciated that it is necessary to have a significant
separation between the parallel axes 80 82 and similarly between
axes 180 182 in order to provide stability. If these axes are too
close, there will be limited stability in the parallel linkage provided
by the outer and inner links 60 66 and 160 166. Consequently,
in order to provide a compact and very low bed frame in the lowered
position, it is necessary to accommodate the separation between
these axes while at the same time maintaining a very compact arrangement.
This has been achieved as can be seen in FIG. 3 while providing
space under the main support 22 between the mechanisms 24 26. This
space results in part because the mechanisms 24 26 are independent
and not connected by mechanical hardware which would likely take
up some of the space. As a result, there is adequate clearance space
to receive the feet of lifting equipment used to move patients,
and the location of the space is such that the equipment can be
located above the patient in the ideal position for lifting.
Upon elevating the main support 22 the cranks 86 186 will be
rotated back towards the position shown in FIG. 2. As this happens,
the padded feet 98 will come into contact with the support surface
to stabilize the position of the bed and the wheels 74 76 will
roll to allow the change in length as the wheels 74 76 move towards
the padded feet 98.
Although not shown in the drawings, it will be evident that because
the mechanisms 24 26 are independent, the electrical supply system
can be arranged to drive one or the other of the motors 88 188
thereby tilting the main support either with the head down or the
foot down. The bed can then be brought back to horizontal using
the controller and judging the position of the main support with
reference to horizontal, or by driving the main support into either
the lowered or the raised positions, thereby causing the individual
actuators to meet the ends of their travels. If one actuator reaches
the end of its travel first and the other is continued to be driven
to the end of its travel, then the main support 22 will automatically
come into a horizontal position. Similarly, if there is a slight
variation in travel due to the weight differences at the ends of
the main frame 24 although the frame may tilt very marginally in
travelling, it will meet the horizontal position at the end of its
travel. It has been found that with a suitable mechanical advantage
in the actuators, this is not a problem.
As seen in FIG. 3 when the bed frame is moved on the support surface,
it will normally be moved in the lowered position with the castors
102 104 (FIG. 1) on the surface. The bumper rail 78 can then be
used to meet a wall to locate the bed frame relative to the wall.
As the main support 24 is raised, the feet 98 will remain in place
and the wheels 74 76 (FIG. 1) will move towards the feet taking
the bumper rail 78 away from the wall.
In the preferred embodiment, the wheels 76 and castors 104 have
diameters of 7.6 cm; the outer links 60 and 160 have a length of
48.3 cm between axes of rotation; the overall height of the bed
frame 20 in the lowered position (without mattress frame 106) is
16.2 cm with a clearance above the support surface between castors
and wheels of 5.4 cm.
It will be evident that variations can be made to the described
embodiments and such variations are within the scope of the invention
as claimed. |