[0001] The present application is concerned with person support apparatus, such as a bed,
and with apparatus having a deck and a deck lift system.
[0002] Many person support apparatus, such as hospitals and long-term care (LTC) beds, include
a deck and a person support surface or element such as a mattress, supported by the
deck. Such beds may also include side rails.
[0003] It is known for person support apparatus such as hospital beds to be provided with
lifting systems (often including an hydraulic actuator) which allow the care giver
to change the height of the person support surface of the bed, and to articulate a
deck under the person support surface so as to modify the configuration of the person
support surface. The known arrangements for raising and lowering a person support
surface include arrangements in which an hydraulic actuator is coupled to a pivotable
supporting structure or leg and the controlled extension of the hydraulic actuator
raises the deck surface whereas the controlled retraction of the hydraulic actuator
lowers the deck surface by causing deck supporting frame or legs to fold, respectively,
away from and towards the underside of the deck. A problem with the known arrangements
is that when the deck is in its lowermost position with the supporting structure folded
into the underside of the bed, the hydraulic actuator is also folded into the underside
of the bed and almost parallel to the deck and therefore perpendicular to the direction
in which it must exert a lifting force to counteract gravity and raise the deck and
person on the deck. This means that a very high power actuator is (or a number of
actuators acting in parallel are) required so that it can provide a force having a
sufficiently strong vertical component in the vertical direction to overcome the force
of gravity acting on the weight of the bed and anyone supported within the bed. Such
high power actuators are relatively expensive and/or bulky, and of course doubling
up actuators would also increase costs. A known LTC bed with articulated legs controllably
foldable using hydraulic actuators is the Volker 5380 low-height healthcare bed sold
by Volker Healthcare (GB) Limited.
US 6,473,922 describes a system for the kinematic motion of an articulated bed which uses a defined
bed and support structure geometry to reduce the force necessary to start the legs
in motion to raise the bed.
[0004] US 6,405,393 describes a height and angle adjustable bed with a support arm mechanism which provides
an initial assist force when the bed is in a nearly or fully lowered position and
thereby minimises the force required by the linear actuators used to raise the bed.
The arrangement of
US 6,405,393 includes a compression spring mounted on the support arm adjacent its connection
to the bed, to and which moves with the support arm, and engaged by the support arm
when the support arm and spring are near the horizontal. The arrangement of
US 6,405,393 is complicated, prone to failure, requires a powerful spring and presents an entrapment
risk for fingers and other body parts. It also cannot be used with a raising and lowering
mechanism in which the bottom of the support arm does not move as the bed is raised
and lowered.
[0005] The present invention provides a patient support as defined in claim 1 to which reference
should now be made. Some preferred and/or alternative features are set out in the
dependent claims.
[0006] A preferred example of the invention will now be described by way of non-limiting
example with reference to the attached figures in which:
Figure 1 is a perspective view of a hospital or LTC bed embodying the invention;
Figure 2 is a side and partially cross-sectional (the left-hand portion of the figure)
view of the bed of Figure 1 with the deck in its uppermost position, and with the
deck in its flat position;
Figure 3 is a side and partially cross-sectional view (similar to that of figure 2)
of the bed of figure 1 illustrating the deck in an alternative configuration;
Figure 4 is a side and partially cross-sectional view (similar to that of figure 2)
of the bed with the deck in a position intermediate its lowermost and uppermost positions;
Figure 5 is a side and partially cross-sectional view (similar to that of figure 2)
of the bed with the deck approaching its lowermost position;
Figure 6 is a side and partially cross-sectional view (similar to that of figure 2)
of the bed in its lowermost position;
Figure 7 is an expanded view of the spring arrangement shown in Figures 2 to 6 above;
Figure 8 is a side view of the spring arrangement in its extended unbiased position
such as shown in, for example, Figures 2, 4 and 5;
Figure 9 is a view of the spring arrangement in a compressed and biased position corresponding
to Figure 6;
Figures 10a to 10d are, respectively, a rear schematic view of the spring arrangements
of Figures 7 to 9, a side schematic view of the spring arrangement of
Figures 7 to 9, a sectional view along section B-B of Figure 10b, and a sectional
view along section A-A of Figure 10a;
Figure 11 is a graph showing the force the actuator would have to exert to raise the
deck in the absence of the spring arrangement;
Figure 12 is a graph showing the force of the actuator must exert to raise the deck
in a system including the spring arrangement.
[0007] A hospital bed 1 embodying the invention (see figure 1) includes a deck 2 for supporting
a mattress or other patient support element. The sides of the deck include retaining
loops 3 to hold the mattress in position. The deck is divided into four sections 4,
5, 6, 7. Three of these 4, 5, 7 are articulated and can be moved by a controller (under
the command of the care giver or patient) so as to move the patient support surface
between lying down (see figure 2) and various seating (see figure 3) configurations.
Articulated beds with a controllable articulation system for the patient support surface
are known and not a novel or inventive part of the subject invention so will not be
described in detail.
[0008] Referring to figures 1 and 2, the hospital bed includes a headboard 8 at a first
end and a footboard 9 at a second end. The deck 2 is supported on a base frame 10
to which the head 8 and foot boards 9 are mounted. The sections 4, 5, 7 of the deck
may articulate and move relative to that base frame 10 to take up possible alternative
configurations in the known manner (see figures 1 and 3 for examples of alternative
deck configurations).
[0009] The base frame 10 has two leg or support structures 11 pivotally coupled to its under
surface 12. Each leg structure includes a pair of legs 13 each coupled to the base
frame 10 by a moveable upper pivot 14 at their deck or upper end. The moveable upper
pivots 14 can move parallel to the longitudinal axis of the deck and frame (for example,
the moveable upper pivot of the left-hand leg in figure 2 can move in the direction
shown by arrow B in figure 2).
[0010] As shown in figures 1 and 2, the legs of each pair of legs are connected together
by lower and upper bracing cross-elements 15, 16 at, respectively, the bottom of the
legs and at a point of the legs near their mid-points. The lower bracing cross-elements
15 are coupled to wheel arrangements 17 for engaging a floor surface, and are connected
to the bottoms of their respective legs by lower leg pivots 18 so that they (and the
wheels they support) may pivot relative to the respect leg pairs as the legs pivot
and the patient support surface is raised and lowered. In an alternative embodiment
of the invention (not shown) the lower ends of the legs they may be connected to a
support frame which itself has wheels. Alternatively, the legs or support frame may
omit the wheels.
[0011] The upper bracing cross-elements 16 are each pivotally connected to a pair of stabiliser
elements 19. The stabiliser elements 19, which are each coupled to a leg, are pivotally
connected at their first upper ends to the underside of the deck at a fixed upper
pivot 20 displaced from the leg upper moveable pivot 19 of the respective leg 13,
and are pivotally connected at their second lower ends to the respective pairs of
legs at a pair of respective lower stabiliser pivots 21. Each of the two upper cross-bracing
elements 16 is pivotally connected to a respective pair of stabilisers (and an actuator
22) at actuator pivots 23 on the stabiliser elements. Each stabiliser element has
a slight kink or bend in its length at the stabiliser portion adjacent the actuator
pivot 23. The kink or bend in the stabiliser is to allow room for the cross bars on
the underside of the frame i.e. as the legs are moved up alongside the frame (see
Figure 7).
[0012] An actuator-stabiliser yoke 29 or connection piece is pivotally coupled at a first
end to the actuator pivot 23 and thence to the respective upper cross-bracing element
16 and thence indirectly coupled to a respective pair of stabiliser elements 19. The
actuator-stabiliser yoke 29 is pivotally coupled to an end 25 of an actuator 22 (which
may be a hydraulic rod actuator) such that the actuator controllably extends and retracts
a rod 26. Extension and retraction of the actuator rod 26 causes the respective stabiliser
19 to rotate and hence the leg 13 to rotate relative to the deck 2 and hence raises
or lowers the base frame 10 and the patient support surface on the base frame. The
actuators 22 may be controlled by either the patient or a care-giver. Control mechanisms
for such actuators are well known and may be either a foot operated pedal, a control
panel on the side of the bed, remote control or other control mechanism. Suitable
actuators are well known and are therefore not described in detail in this application.
They may be hydraulic, electric, or pneumatic.
[0013] The bed also includes resilient spring assist elements 27 located in the base frame
for engaging the support structure ensemble comprising the stabilisers, actuator-stabiliser
yoke and actuator rod as the base frame 10 moves towards and is in its lowermost position
(see figures 5 and 6). In the described embodiment, there is a spring assist element
27 to engage each leg 13 and thence interact with each actuator 22. Only one support
structure and corresponding spring assist element is described as the support structure
and spring assist mechanism are the same for each of the two support structures. In
the embodiment shown in the attached figures it is the surface of the respective upper
bracing element 16 which engages the spring assist element 27 as the bed is lowered
to its lowermost position. In alternative embodiments, it may be any surface of the
support structure which moves up towards the patient support surface as the patient
support surface is lowered, and moved downwards away there from as the patient support
surface is raised.
[0014] Each resilient spring assist element 27 includes (see figure 7) a housing 28 for
attachment to a side or longitudinal portion of to the base frame 10, or some other
part if the patient support surface towards which the leg structures move on the bed
is lowered (and move away from as the bed is raised) using screws. The spring assist
elements 27 may be located anywhere on the frame 10 or bed 1 where they engage and
interact with a surface of the support or leg structure 11 as this is pivoted up into
the underside of the bed and the bed is lowered into its lowermost position. A pair
of compression springs 30 are located within the housing 28 and their upper ends engage
a downwardly facing inner surface 31 in the top of the respective housing 28 (see
Figures 7 to 10d). The lower ends of the compression springs 30 engage an upwardly
facing inner surface 32 in an engagement member or bolt 33. The bolt-like engagement
member 33 includes a screw or guide element 34 which runs in a guide 35 in the housing
28. The engagement member 33 is biased by the compression springs to extend from the
housing by the springs (see figure 8) when it is not engaged and being pushed back
into the housing. If a force sufficient to overcome the springs is exerted upwardly
on the biased engagement member, it can be pushed back into the housing (see figure
9).
[0015] Referring to figures 2, 4, 5 and 6, when the actuator rod 26 is fully extended (as
shown in figure 2), the deck 2 is in its uppermost or highest position. As the rod
26 is retracted (see figure 2), the stabiliser 19 is pivoted about its fixed pivot
20 in the direction shown by arrow A, and the upper moveable pivot 14 moves in the
direction shown by arrow B, and the base frame 10 (and deck mounted thereon) is lowered.
As the base frame 10 approaches its lowermost position (see figure 5) the upper surface
of the upper bracing element 16 on each leg structure contacts the bottom 36 of each
of the biased engagement members 33 of each of the two spring assist elements 27.
As the base frame is lowered further, the weight of the deck and base frame (and anything
supported thereon) compresses and biases the two compression springs 30 (see figure
6) of each of the spring assist elements. As shown in figure 6, when the base frame
is in is lowermost position the actuator 22 is in an almost horizontal orientation.
That means that the direction in which the actuator rod force acts is almost perpendicular
to the vertical direction in which gravity acts and therefore has only a small vertical
component to counter-act and overcome gravity when the base frame 10 (and the bed
and any patient on the beds patient support surface) is to be raised from its lowermost
position.
[0016] However, the two spring assist elements 27 store energy in the compressed oil springs
30 when these have been biased by the weight of the bed and are in their lowermost
position as shown in figure 7. The force exerted by the compressed springs acts against
the weight of the bed and thereby effectively reduces the weight which the actuator
must overcome when raising the base frame from its lowermost position.
[0017] Figure 11 shows an example of what the actuator force would have to be to raise a
bed from its lowermost to its uppermost position at the various heights it must go
through. It shows that the force necessary as it is first lifted form the lowermost
position is a high one. Figure 12 shows how adding in the two spring assist elements
described above significantly reduces the initial force required. The example of Figure
11 allows one to achieve this with an actuator which need not produce a force of greater
than 6000N. The calculations used to create the examples of Figures 11 and 12 were
based on a maximum weight on the bed of 230kg which requires a maximum lifting force
of about 8500N. The springs used in the example of Figure 12 were coil springs with
reference D12670 from the Associated Spring Spec catalog with the properties set out
below:
LIFT SPRING |
|
|
PARAMETER |
VALUE |
UNITS |
OUTSIDE DIAMETER (OD) |
14.50 |
mm |
WIRE DIAMETER (d) |
2.00 |
mm |
FREE LENGTH (FL) |
49.50 |
mm |
LOAD LENGTH (L1) |
23.50 |
mm |
SOLID HEIGHT (SH) |
21.00 |
mm |
LOAD (P) at L1 |
254 |
N |
SPRING RATE (k) |
9.81 |
N/mm |
MATERIAL |
MUSIC WIRE |
--- |
END CONDITION |
SQUARED AND GROUND |
--- |
[0018] The embodiment of the invention described above uses a compression spring. Any arrangement
which stores energy as it is compressed and then releases it as it then relaxes is
suitable.
1. A patient support comprising
a frame;
a deck supported by the frame;
a support structure for supporting the frame, the support structure including at least
one support element having an upper portion pivotally coupled to the frame at an upper
support element pivot, and at least one actuator configured to move between a first
and a second position to controllably pivot the support element relative to the frame
between a first uppermost raised position and a second lowermost lowered position
wherein the support element subtends a smaller angle relative to the frame in the
second lowered position than when it is in the first raised position;
an energy storage mechanism for storing energy as the frame is lowered, and for using
that stored energy as the frame is raised;
wherein
the energy storage mechanism comprises a spring arrangement located on the frame and
having a downwardly facing resilient spring surface, the patient support includes
an upwardly facing spring engagement surface which moves with the support element,
and wherein the spring engagement surface contacts the spring surface as the frame
approaches and reaches its lowermost position to thereby compress the spring arrangement
as the frame is lowered to its lowermost position, and wherein the compressed spring
acts to push the spring surface against the spring engagement surface as the frame
is raised away from the second lowermost lowered position.
2. A patient support according to claim 1 wherein the downwardly facing spring surface
is substantially horizontal.
3. A patient support according to any preceding claim wherein the spring arrangement
is a compression spring arrangement.
4. A patient support according to any preceding claim wherein the energy storage mechanism
comprises a housing having a first internal surface, a bolt element projecting from
and slideable relative to the housing, and a compression spring having a first end
against the first internal surface and a second end against the bolt element so that
the spring biases the bolt to extend from the housing and engage the spring engagement
surface as the frame approaches and reaches its lowermost position.
5. A patient support according to any preceding claim wherein the actuator includes a
moveable element having a first end pivotally coupled to the support element , the
actuator moveable element actuator being controllably extendable and retractable to
pivot the support element relative to the frame between the first uppermost raised
position and the second lowermost lowered position.
6. A patient support according to claim 5 wherein the support element includes a stabiliser
element , a lower portion of the stabiliser being pivotally coupled to an intermediate
portion of the support element at a lower stabiliser pivot and the upper portion of
the stabiliser element being pivotally coupled to the frame at an upper stabiliser
pivot.
7. A patient support according to any preceding claim wherein the actuator moveable element
is coupled to a portion of the stabiliser proximal the support element.
8. A patient support according to claim 7 wherein the actuator and stabiliser are coupled
by a connection element, a first portion of the connection element being pivotally
connected to the stabiliser and a second portion being pivotally connected to the
actuator moveable element.
9. A patient support according to any preceding claim wherein the upper support element
pivot is moveable in a direction parallel to the longitudinal axis of the support
element.
10. A patient support according to claim 6 and claim 9 wherein the upper stabiliser pivot
is at a fixed position on the frame.
11. A patient support according to any preceding claim wherein the support structure includes
two support elements coupled by at least one bracing element and wherein a portion
of the bracing element is the spring engagement surface.
12. A patient support according to claim 11 and either of claims 7 or 8, wherein the actuator
moveable element is pivotally connected to the bracing element, and the bracing element
is pivotally connected to the two stabilisers, at a portion of the two
stabilisers proximal their respective lower stabiliser pivot.