Note: Descriptions are shown in the official language in which they were submitted.
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PATIENT BED WITH CPR SYSTEM
Field of the Invention
The present invention relates to patient beds, particularly to adjustable
patient
beds for healthcare facilities, such as hospitals and long-term care
facilities. In
particular, the present invention relates to an emergency system for such
beds.
Background of the Invention
Patient beds in healthcare facilities are designed so that various parts of
the
bed can adopt a number of positions to provide for greater patient comfort
and/or to
facilitate the tasks of an attendant, for example a nurse. For example, beds
may be
raised or lowered to different heights. Patient support platforms may be
tilted to
achieve the Trendelenburg and reverse Trendelenburg positions. Patient support
platforms may comprise back rests and/or knee rests that can be raised or
lowered to
support a patient's back and knees in a variety of positions.
Adjusting the position of the bed or parts of the bed may be accomplished by a
variety of means, for example, by mechanical, hydraulic and electrical means
and
combinations thereof. Purely mechanical means, including linkages, gears,
cranks,
etc., have traditionally been used but generally require manual power for
their
operation. Consequently, physical limitations of the bed's operator represent
significant limitations to the design of beds where position changes are
accomplished
solely by mechanical means. The additional use of hydraulics permits bed
design
where the physical limitations of the operator are less of a factor. However,
the use
of electrical components, for example motors, switches, electronic
controllers, etc., in
combination with mechanical and/or hydraulic components has greatly simplified
the
design and use of patient beds throughout the healthcare industry. Beds
designed
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with electrical components permit extensive operation of the bed with minimal
operator effort.
Electrically operated patient beds are generally equipped with a plurality of
switches to control the various adjustments that can be made to the bed.
Switches
are often localized on a single control panel for easy access by an operator.
Where
access to the switches by the patient is undesirable, the control panel may be
located
in an area of the bed that is normally inaccessible to the patient in the bed,
for
example, on the outside face of the foot board.
Despite the flexibility offered by the use of electrical components, there
remains limitations, often driven by regulatory considerations, to the use of
electrical
components in patient beds. Thus, in a number of instances, mechanical means
are
still used for some operations of the bed. This is particularly evident in the
design of
emergency systems for patient beds.
Design of medical electrical equipment is regulated by International
Standards.
In particular, two standards applicable to electrically operated patient beds
are:
UL 2601-1, the Underwriters Laboratories Inc. Standard for Safety, Medical
Electrical Equipment, Part 1: General Requirements for Safety (1997); and,
IEC 601-2-38 International Standard, Medical Electrical Equipment - Part 2:
Particular requirements for the safety of electrically operated hospital beds
(1996).
According to Section 22.4 of UL 2601-1,
"Movements of EQUIPMENT or EQUIPMENT parts which may cause physical
injury to the PATIENT shall be possible only by the continuous activation of
the control by the OPERATOR of these EQUIPMENT parts."
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According to Section 22.4.101 of IEC 601-2-38,
"Electrically powered functional movements of the BED shall be possible only
by means of MOMENTARY CONTACT SWITCHES."
Momentary Contact Switch is defined in Section 2.1.106 of IEC 601-2-38:
"Control device which initiates and maintains operation of operating elements
only as long as the control (actuator) is actuated. The manual control
(actuator) returns automatically to the stop position when released.
MOMENTARY CONTACT SWITCHES are also known as "hold-to-run control
devices"."
In an emergency situation, for instance when a patient has a heart attack or
goes into shock, an attendant must quickly perform emergency procedures on the
patient, for example CPR (cardiopulmonary resuscitation). However, a patient
in a
patient bed, may be in any number of positions at the onset of the emergency.
For
instance, the back and knee rests may be raised so that the patient is in a
sitting
position, for example, to watch television, to eat, etc. In such an instance,
it is
necessary for the back and knee rests to be lowered quickly to a flat position
so that
emergency procedures may be administered more effectively. It is desirable,
therefore, that the bed have a system by which the back and knee rests may be
lowered quickly to the flat position, while at the same time permitting the
attendant to
begin administering emergency procedures.
However, in light of the above-noted standards, all electrical control of
moving
parts on an electrically operated patient bed has heretofore been by way of
momentary contact switches. Since momentary contact switches turn off the
functioning of a moving part when the switch is released, electrical
activation of an
emergency system on a patient bed has been heretofore considered impossible
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within the context of the above-noted standards. Instead, emergency systems on
patient beds have been designed to activate manually, even on beds otherwise
electrically operated, in order to remain within the above-noted standards.
Therefore, there is a need in the art for an electrically activated emergency
system on a patient bed, which meets the regulatory requirements of the
standards
governing electrically operated patient beds.
Summary of the Invention
According to an aspect of the present invention, there is provided an
emergency system for a patient bed comprising: an electrically powered linear
actuator operable to drive a back rest of the patient bed from a lowered back
rest
position to a raised back rest position, and operable to permit the back rest
to lower
from the raised back rest position to the lowered back rest position without
being
driven by the linear actuator; and, an independent electrical activation means
for
activating the liriear actuator to permit the back rest to lower from the
raised back rest
position to the lowered back rest position without being driven by the linear
actuator,
the electrical activation means not requiring continued operator attendance
for
continued lowering of the back rest.
According to another aspect of the present invention, there is provided a
patient bed comprising a patient support platform having a back rest portion;
an
electrically powered linear actuator operable to drive the back rest from a
lowered
back rest position to a raised back rest position, characterized in that the
linear
actuator is operable to permit the back rest to lower from the raised back
rest position
to the lowered back rest position without being driven by the linear actuator;
and, the
bed further comprises an emergency back rest lowering system comprising an
independent electrical activation means for activating the linear actuator to
permit the
back rest to lower from the raised back rest position to the lowered back rest
position
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without being driven by the linear actuator, the electrical activation means
not
requiring continued operator attendance for continued lowering of the back
rest.
The patient support platform generally comprises a hard support surface and
may also comprise a mattress, sheets, blankets or other bedding to provide
greater
5 comfort to the patient. A patient support platform useful in the present
invention has
a back rest portion. The back rest may be raised from a lowered position to a
raised
position so that a patient is able to sit up in the bed, for example, to watch
television,
to eat, etc. Conversely, the back rest may be lowered from the raised position
to the
lowered position. For administering emergency procedures, for example CPR, the
lowered position is preferably a flat position in respect of the patient
support platform.
The raised position may be any position between the lowered position and a
maximum raised position. It is clear to one skilled in the art that the back
rest may
also be raised and lowered between positions intermediate between the lowered
position and the maximum raised position.
The patient support platform may also have a knee rest portion and/or other
portions that may be adjustable to provide different options for patient
positioning on
the patient support platform. Raising and lowering the knee rest and/or other
portions of the support platform is similar to that described for the back
rest.
The patient support platform is generally supported on the ground or floor by
a
support means. There are numerous suitable ways in the art for supporting a
patient
support platform on the ground or floor. For example, United States Patent
Publication 2003/0172459 published September 18, 2003, the disclosure of which
is
herein incorporated by reference, describes a suitable leg arrangement for
supporting
a patient support platform.
In electrically operated patient beds, various parts of the bed may be
adjusted
to achieve various positions. Positional adjustment may be accomplished by a
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variety of means known in the art. Electrically powered linear actuators are
particularly preferred in patient beds of the present invention. Linear
actuators may
adjust the height of the bed, for example as disclosed in United States Patent
Publication 2003/0172459. Linear actuators may also be used to adjust the
position
of the back rest, knee rest and other portions of the patient support
platform. A single
linear actuator may be used to adjust a number of features, however, it is
preferred to
use a linear actuator for each feature to be adjusted. Thus, the back rest and
knee
rest are each preferably adjusted by its own linear actuator.
A linear actuator useful in the present invention is operable to drive the
back
rest from a lowered back rest position to a raised back rest position, and
operable to
permit the back rest to lower from the raised back rest position to the
lowered back
rest position without being driven by the linear actuator. Thus, the linear
actuator
drives the back rest when it is being raised but does not actually drive the
back rest
when it is being lowered. The back rest lowers only under an applied external
force,
such as gravity, the weight of the patient, etc. As a consequence, lowering of
the
back rest is not an electrically powered functional movement of the bed that
may
cause injury, and is therefore not subject to the standards described above.
This
aspect of the linear actuator surprisingly may be utilized in an electrically
activated
emergency system that meets the standards described above. A particularly
preferred electrically powered linear actuator is a LinakT"~-LA31 having a
spline
feature.
Control of electrically powered linear actuators is accomplished by electrical
activation means. The term "electrical activation means" in this context
encompasses any component that may be used in a control circuit that functions
using electricity, for example, switches, timers, microprocessors, voltage
regulators,
logic gates, and any other electrical or electronic components. Such
components
may be embodied in software of a controller. Electrical power to operate all
electrical
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functions of the bed may be supplied by the main power of a building and/or by
an
internal power supply (e.g. a battery).
While the emergency system of the present invention and other control
systems of the bed may share various common elements, activation of the
emergency system is independent of activation of the other control systems.
Other
control systems include the systems that control the raising and lowering of
the back
rest and knee rest under normal conditions. Thus, the electrical activation
means for
the emergency system may comprise its own switch, whereby triggering the
switch
activates the linear actuator to permit the back rest to lower from the raised
back rest
position to the lowered back rest position. Preferably, a single, dedicated
user
operated switch activates all elements of the emergency system. For example,
triggering one switch may cause both the back rest and a knee rest to lower.
The
switch may be any suitable type, for example, push button switches, leaf
switches,
etc. The switch may be located anywhere on or off the bed. For example, the
switch
may be conveniently located on a control panel or a control pendant containing
other
control switches for the bed. The switch may be hard wired in the emergency
system's control circuit or signals from the switch may be sent to the control
circuit
wirelessly.
It is an important aspect of the emergency system of the present invention
that
the electrical activation means does not require continued operator attendance
for
continued functioning. As stated above, the standard for electrically powered
beds
requires that electrically powered functional movements of the bed be possible
only
by means of momentary contact switches that stop the movement when the switch
is
released. Therefore, it is surprising to one skilled in the art that an
electrically
activated emergency system, such as the emergency system provided by the
present
invention, can work without momentary contact switches that stop the linear
actuators
when the switch is released.
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Preferably, the electrical activation means comprises a timer for continuing
to
provide a signal so that the linear actuator is powered for at least a maximum
time
required for the back rest to achieve the lowered back rest position. The
timer frees
an operator to immediately begin administering emergency procedures to the
patient
(e.g. CPR) rather than attending to the activation means until the back rest
reaches
the lowered back rest position. The maximum length of time depends on the type
of
bed and the type of linear actuator. For example, for a bed of the type
described in
United States Patent Publication 2003/0172459 and a LinakT"'-LA31 having a
spline
feature, the maximum time required to lower the back rest to the lowered back
rest
position is about 8 seconds. In this case, the timer should be set for at
least 8
seconds, and may be set for longer. A setting of from about 8-20 seconds is
preferred, particularly about 15 seconds.
Limit switches may also be used to cut power to electrically activated
components of the emergency system and/or other electrically operated parts of
the
bed. In such instances, movement of a moving part beyond a pre-selected point
would trip a limit switch to cut electrical power to the moving part. Limit
switches are
generally used as an added safety measure, to reduce power consumption, etc.
Further features of the invention will be described or will become apparent in
the course of the following detailed description.
Brief Description of the Drawincts
In order that the invention may be more clearly understood, embodiments
thereof will now be described in detail by way of example, with reference to
the
accompanying drawings, in which:
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Figure 1 is an electrical schematic of an emergency system of the present
invention;
Figure 2 is a schematic drawing of a linear actuator useful in an emergency
system of the present invention;
Figure 3 is a schematic drawing of a disengaging spline of the linear actuator
of Figure 2;
Figure 4a is a perspective view of an electrically operated patient bed
comprising the emergency system of Figure 1;
Figure 4b is a schematic perspective view of the patient support platform of
the bed depicted in Figure 4a;
Figure 4c is a schematic side view of a support platform of the bed depicted
in
Figure 4a in which back and knee rests are in a raised position; and,
Figure 4d is a perspective view of the bed depicted in Figure 4a in which back
and knee rests are in a raised position.
Description of Preferred Embodiments
Referring to Figure 1, an electrical schematic of an emergency system of the
present invention is depicted. A single push-button emergency switch 127 is
located
on a control panel 126 on a foot board of an electrically operated patient
bed.
Associated with the control panel 126 is a control panel microcontroiler 161,
which
together form a foot board staff control unit 160. Other control buttons (not
shown)
are also on the control panel 126 and are associated with the control panel
microcontroller 161. The control panel microcontroller 161 comprises, among
other
elements (not shown), a button decoder 162, a timer 163 and a first UART
serial port
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164. In an emergency situation, an attendant pushes the emergency switch 127
thereby sending a signal to the button decoder 162 which is programmed to
distinguish between the buttons on the control panel. Having determined that
the
emergency switch 127 was pushed, the button decoder 162 sends a signal to the
5 timer 163 which is programmed to continue sending the signal for 15 seconds.
The
signal goes from the timer 163 to the first UART serial port 164 and is
carried by a
wire 165 to an actuator control box 170 located elsewhere on the bed.
The actuator control box 170 comprises, among other elements (not shown), a
second UART serial port 171 in an actuator microcontroller 172, and two sets
of NPN
10 transistors 173,174, relays 175,176 and field effect transistors (FET)
177,178. The
signal carried by the wire 165 enters the actuator microcontroller 172 at the
second
UART serial port 171. The actuator microcontroller 172 recognizes the signal
as one
intended to operate a first linear actuator 140 and a second linear actuator
150. The
first linear actuator 140 operates a back rest of the bed and the second
linear
actuator 150 operates a knee rest of the bed. From the actuator
microcontroller 172,
the signal is sent to the NPN transistors 173,174, which power the coils
180,181 of
the relays 175,176. Powering the coils 181,182 activates armatures which pull
down
on contacts 183,184 thereby permitting 24V DC power to flow to the linear
actuators
140,150. The field effect transistors 177,178 momentarily keep the circuit
open when
the contacts 183,184 close in order to prevent arcing in the contacts. Power
to the
linear actuators 140,150 drives motors in the linear actuators which permits
lowering
of the back and knee rests as described below. Fifteen seconds after the
emergency
switch 127 is pushed, the timer 163 terminates the signal. The linear
actuators
140,150 may switch off before the timer 163 terminates the signal since the
linear
actuators may reach the fully retracted position before the 15-second time
period
elapses. The 15-second time period is programmed into the timer 163 to allow
ample
time for the linear actuators to reach the fully retracted position.
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Referring to Figure 2, a linear actuator having a disengaging spline is
depicted. A DC
motor 50 drives a worm gear 51 which in turn drives a bevel gear 52. The bevel
gear
52 is connected to a flexible clutch 53 which is connected to a ball bearing
spindle
mount 54. The spindle mount is connected to a lead screw 55. Rotation of the
bevel
gear 52 causes rotation of the lead screw 55. The lead screw 55 is
disengageably
connected to a hollow steel piston rod 57 by a disengaging spline (not shown).
Part
of the lead screw, the disengaging spline and part of the piston rod are
housed in an
outer tube 58. End stroke limit switches 59 are mounted near one end of the
outer
tube 58. A casing 70 houses most of the elements of the linear actuator. The
piston
rod 57 comprises an eye 71 at one end for connection to bed elements which
raise
and lower the back or knee rest.
Referring to Figure 3, a schematic drawing of the disengaging spline of the
linear actuator of Figure 1 is shown in context with the lead screw 55, piston
rod 57
and outer tube 58. The disengaging spline comprises a female part 61 connected
to
the piston rod 57, and a male part 62 on a lead screw nut 63 threaded on to
the lead
screw 55. The lead screw nut 63 comprises an O-ring 64 for sealing against the
inside of the outer tube 58. For clarity, Figure 3 depicts the male part 62
and the
female part 61 of the disengaging spline in a disengaged position.
Referring to Figures 2 and 3, when the lead screw 55 is driven in a forward
(extending) direction (to the left in Figures 2 and 3), and the male part 62
of the
disengaging spline on the lead screw nut 63 is seated in the female part 61 of
the
disengaging spline, the lead screw nut 63 cannot rotate. Instead, the lead
screw 55
rotates in a threaded portion inside the lead screw nut 63 driving the lead
screw nut
forward thereby driving the piston rod 57 forward. Since the piston rod is
connected
to bed elements which raise the back or knee rest, the back or knee rest is
thereby
raised. When the lead screw 55 is driven in a reverse (retracting) direction
(to the
right in Figures 2 and 3), the lead screw nut 63 threads in the retracting
direction
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along the lead screw 55 and the male part 62 of the disengaging spline
disengages
from the female part 61. Therefore, the piston rod 57 is not driven in the
retracting
direction and the piston rod 57 only moves in the retracting direction by
virtue of
applied forces (e.g. the weight of the patient, weight of the back or knee
rest, etc.).
Movement of the piston rod 57 by such applied forces keeps the female part 61
of
the disengaging spline seated in the male part 62. Use of the disengaging
spline
means that the piston rod is not attached to the lead screw nut and that the
piston
rod is free to move independently of the lead screw nut. Therefore, during
lowering
of the back or knee rest, an applied force on the back or knee rest in the
opposite
direction, such as when the back or knee rest meets an obstacle, will cause
the male
part 62 to disengage from the female part 61. The male part continues along
with the
lead screw nut 63 while the female part stays with the piston rod 57 which
cannot
move due to the opposite applied force. In fact, it is possible to physically
lift the
back or knee rest to a raised position even while the linear actuator is
causing the
lead screw nut 63 to travel in the reverse (retracting) direction.
At the end of the forward and reverse strokes of the linear actuator, the
outer
tube 58 is urged forward and backward respectively thereby triggering limit
switches
59 which cut power to the motor 50 to automatically stop the linear actuator
at the
end of each stroke.
Referring to Figures 4a, 4b, 4c and 4d, an electrically operated patient bed
comprising the emergency system of the present invention is shown in which a
patient support platform 100 (shown in broken line in Figure 4a), having a
back rest
portion 105 and a knee rest portion 110, shown in their lowered (flat)
positions in
Figures 4a and 4b, rests on a bed frame 115. A head board 120 and a foot board
125 are located at the ends of the patient support platform. All switches for
electrical
activation of bed features are located on a single control panel 126 located
on the
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outside of the foot board 125. The control panel 126 has a single push-button
emergency switch 127 dedicated to activating the emergency system.
Pivotally attached to the frame 115 are legs 130 having foot/caster
arrangements 131, which support the bed on the floor or ground. Electrically
powered linear actuators 135 activated from the control panel 126 operate to
raise
and lower the bed.
Referring specifically to Figure 4b, the back rest portion 105 is hingedly
attached to the support platform 100 along axis A-A. Along axes A-B and B-B,
the
back rest is not attached to the support platform so that the back rest can be
raised to
a raised back rest position by pivoting on the axis A-A. The knee rest portion
110 is
hingedly attached to the support platform 100 along axis C-C. The knee rest is
divided into two sections defined by rectangles C-C-D-D and D-D-E-E
respectively.
Axis D-D is also hinged to permit the two sections of the knee rest to pivot
in respect
of each other. Along axes C-E and E-E, the knee rest is not attached to the
support
platform so that the knee rest can be raised to a raised knee rest position by
pivoting
on the axes C-C and D-D. The raised back rest and knee rest positions are
illustrated in Figures 4c and 4d.
Under normal conditions, raising and lowering of the back rest 105 is
accomplished by a first linear actuator 140 activated by momentary contact
switches
on the control panel 126. The first linear actuator 140 is linked to a
transverse back
rest pivot element 141 rotationally mounted on the frame 115. Back rest
support
arms 142 are each fixed at one end to the back rest pivot element 141.
Proximal
another end of each of the back rest support arms 142 are back rest support
wheels
143 rotationally attached to the support arms 142. The back rest 105 rests on
the
support wheels 143 without being fixedly attached to the back rest support
arms 142.
When the first linear actuator 140 is activated to raise the back rest 105 by
pressing
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one of the momentary contact switches, the linear actuator rotationally drives
the
back rest pivot element 141 which causes the back rest support arms 142 to
raise
which in turn causes the back rest 105 to raise while riding on the back rest
support
wheels 143. Lowering the back rest 105 requires pressing a separate momentary
contact switch which drives the first linear actuator 140 in the reverse
direction which
permits the back rest to lower. Under normal conditions, raising and lowering
the
back rest requires continued pressing of the appropriate momentary contact
switch
by the operator.
Under normal conditions, raising and lowering of the knee rest 110 is
accomplished by a second linear actuator 150 activated by momentary contact
switches on the control panel 126. The second linear actuator 150 is linked to
a
transverse knee rest pivot element 151 rotationally mounted on the frame 115.
Knee
rest support arms 152 are each fixed at one end to the knee rest pivot element
151.
Proximal another end of each of the knee rest support arms 152 are knee rest
support wheels 153 rotationally attached to the support arms 152. The section
of the
knee rest 110 described by rectangle C-C-D-D rests on the support wheels 153
without the knee rest 110 being fixedly attached to the knee rest support arms
152.
When the second linear actuator 150 is activated to raise the knee rest 110,
the
linear actuator rotationally drives the knee rest pivot element 151 which
causes the
knee rest support arms 152 to raise which in turn causes the C-C-D-D section
of the
knee rest 110 to raise while riding on the knee rest support wheels 153. The D-
D-E-
E section of the knee rest 110 pivots down along the axis D-D so that the knee
rest
assumes an inverted V-configuration in the raised position, as illustrated in
Figures
4c and 4d. Lowering the knee rest 110 requires pressing a separate momentary
contact switch, which drives the second linear actuator 150 in the reverse
direction
which permits the knee rest to lower. Under normal conditions, raising and
lowering
CA 02472502 2004-06-25
the knee rest requires continued pressing of the appropriate momentary contact
switch by the operator.
In an emergency situation, with the back rest 105 and the knee rest 110 in the
raised position, as depicted in Figures 4c and 4d, an operator may press the
5 emergency switch 127, which is electrically connected to both the first
linear actuator
140 and the second linear actuator 150 in a manner as described above with
reference to Figure 1. Thus, pressing the emergency switch 127 causes the
linear
actuators 140,150 to operate in the reverse direction and after the operator
releases
the emergency switch 127, power continues to flow to bath of the linear
actuators.
10 However, since the linear actuators 140,150 are equipped with disengaging
splines
as described above with reference to Figures 2 and 3, the back and knee rests
lower
to the flat position under the weight of a patient in the bed, rather than
being driven
by their respective linear actuators. When the linear actuators reach their
fully
retracted positions, the switch off. The 15-second time period programmed into
the
15 timer is enough time for the back and knee rests to achieve their
respective flat
positions. During lowering of the back and knee rests the operator is free to
begin
performing emergency procedures such as CPR. Since the linear actuators
140,150
do not actually drive the back and knee rests, body parts of the operator
and/or
patient will not be badly hurt if they get caught under the back and/or knee
rest.
Other advantages which are inherent to the structure are obvious to one
skilled in the art. The embodiments are described herein illustratively and
are not
meant to limit the scope of the invention as claimed. Variations of the
foregoing
embodiments will be evident to a person of ordinary skill and are intended by
the
inventor to be encompassed by the following claims.
