Note: Descriptions are shown in the official language in which they were submitted.
1 337076
-- 1 --
Hospital Bed for Weiqhing Patients
Background of the Invention
This application is a division of co-pending
Canadian Application Serial No. 569,320 filed June 13,
1988.
This invention relates to a hospital bed, and
more particularly, to a hospital bed having the capability
of measuring and maintaining a record of a patient's weight
as well as changes in the patient's weight.
The bed of the present invention has its
principal use in intensive care or critical care units of
a hospital. There, it is necessary to monitor vital
functions of a patient on a r~gular basis. Some must be
monitored continuously. One of the vital functions that
must be measured on a regular basis is the patient's
weight.
Since the patient's health is in such a state
that the patient is required to be in intensive or critical
care, it is highly likely that the patient cannot leave the
bed for a weight measurement and that the patient probably
should not be subjected to the trauma attending moving the
patient to some sort of scale.
Patient weighing has been done in various ways.
A cumbersome sling overlying the bed has been provided, and
it has been necessary to move the patient onto the sling
and to lift the patient, by means of the sling, off the bed
to effect the weighing operation.
Thin weighing scales adapted to be slid under the
patient have been disclosed. See U.S. Patents Nos.
3,217,818 and 3,463,368.
A weigh system forming part of a bed assembly has
been disclosed in U.S. Patent No. 4,015,677. Since
- 1 337n76
there is practically no bed structure disclosed, it is
assumed that the total bed and patient are weighed.
It is known that Stryker Corp. of Kalamazoo,
Michigan is marketing a bed having a weight monitoring
capability, but not much is known about how the weighing is
accomplished. The literature indicates that there are
provisions for changing tare to accommodate things added or
taken from the bed. Aside from the background art
heretofore disclosed, there is little art relating to weigh
beds.
Summary of the Invention
In accordance with an embodiment of the present
invention there is provided in a hospital bed having a
weigh frame supported by at least one load cell on a
support frame, a control/readout apparatus connected to the
load cell comprising: a display for weigh data; control
means including keys for entering weigh units connected
between the load cell and the display; the control means
for entering and displaying tare weight and changing tare
when an unknown change in tare occurs, and for displaying
the patient's weight; and means for initiating an alarm at
a central station when a patient leaves the bed.
In accordance with another embodiment of the
present invention there is provided, in a hospital bed
having a weigh frame supported by at least one load cell on
a support frame, a control/readout apparatus connected to
the load cell comprising: a display for weigh data;
control means including keys for entering weigh units
connected between the load cell and the display; the
control means for entering and displaying tare weigh~ and
changing tare when an unknown change in tare occurs, and
for displaying the patient's weight; a SET switch for
activating the display to show alarm weight and to activate
keys for setting or changing existing a'arm weight value;
and a MODE switch for sequencing the control means through
"exit" weight, "over" weight, and "under" weight; and an
_ 3 _ 1 3 3 7 07 6
alarm that is activated when any of the preset mode
conditions occur.
In accordance with a further embodiment of the
present invention there is provided, in a hospital bed
having a weigh frame supported by at least one load cell on
a support frame, a control/readout apparatus connected to
the load cell comprising: a display for weigh data;
control means including keys for entering weigh units
connected between the load cell and the display; the
control means for entering and displaying tare weight and
changing tare when an unknown change in tare occurs, and
for displaying the patient's weight; and means for
initiating an alarm at a central station when a patient
leaves the bed; an ALARM switch for programming the
following alarm types: Silent - flashing LED on readout
unit; Local - flashing LED plus audio beep on readout unit;
REMOTE - audio beep transmitted to central station.
In accordance with yet another embodiment of the
present invention there is provided, in a weigh apparatus
having a weigh frame supported by at least one load cell on
a support frame, a control/readout apparatus operatively
connected to the load cell and comprising: a display for
weigh data;.control means including keys for entering weigh
units connected between the load cell and the display; the
control means for entering and displaying tare weight and
changing tare when an unknown change in tare occurs; and
for displaying the weight of a load supported by the weigh
frame; and means for initiating an alarm at a central
station when a load is removed from the weigh frame.
In another embodiment of the present invention
there is provided, in a weigh apparatus having a weigh
frame supported by at least one load cell on a support
frame, a control/readout apparatus operatively connected to
the load cell and comprising: a display for weigh data;
control means including keys for entering weigh units
1 337076
connected between the load cell and the display; the
control means for entering and displaying tare weight and
changing tare when an unknown change in tare occurs; and
for displaying the weight of a load supported by the weigh
frame; a SET switch for activating the display to show
alarm weight and to activate keys for setting or changing
existing alarm weight value; a MODE switch for sequencing
the control means through "exit" weight, "over" weight, and
"under" weight; and an alarm that is activated when any of
the preset mode conditions occur.
In accordance with yet another embodiment of the
present invention there is provided, in a weigh apparatus
having a weigh frame supported by at least one load cell on
a support frame, a control/readout apparatus operatively
connected to the load cell and comprising: a display for
weigh data; control means including keys for entering weigh
units connected between the load cell and the display; the
control means for entering and displaying tare weight and
changing tare when an unknown change in tare occurs; and
for displaying the weight of a load supported by the weigh
frame; means for initiating an alarm at a central station
when a load is removed from the weigh frame; and an ALARM
switch for programming the following alarm types: Silent -
flashing LED on readout unit; Local - flashing LED plus
audio beep on readout unit; Remote - audio beep transmitted
to central station.
In a preferred embodiment, a weigh frame that
contains the patient supporting surface is mounted at its
four corners by load cells to a bed support frame. The
weight from the four load cells is summed, as will ~e
described below.
Each load cell may be fixed at one end to the
support frame and at the other to the weigh frame by
universal swivels having upper and lower ball joints.
Thus, the weigh frame "floats" with respect to the support
frame and does not bind, thereby eliminating possible error
_ 5 _ 1337076
in the weighing function.
In a preferred feature, the weigh frame is an
inverted U that telescopes over a support frame that is
preferably formed of a hollow rectangular section tube.
The depending legs of the inverted U provide points of
attachment for the connection of the weigh frame to the
swivel joint and thus to the support frame. The
relationship of inverted U weigh frame and the rectangular
tube support frame provides freedom of vertical movement of
the weigh frame while restricting horizontal or lateral
movement, thus providing a stable support of the weighing
assembly with respect to the support frame and lower bed
structure.
In another preferred feature, a four panel
patient support surface is mounted entirely on the weigh
frame. Pistons and cylinders connect the support surface
to the weigh frame to permit normal articulation of the
four panels to permit the patient to assume the
conventional reclining and sitting attitudes associated
with hospital beds. The system for providing pressure to
the pistons and cylinders is mounted on the lower base
frame and does not form a part of the weight applied to the
load cells, with flexible hoses being provided to connect
the pressure system to the pistons and cylinders that
operate the patient support surface
In another preferred embodiment, the support
frame projects at both of its ends beyond the weigh frame.
The projecting portions of the support frame carry
accessories such as infusion pumps, I.V. bags, drainage
bags, head and foot-boards and the like. By mounting those
accessories on the support frame, the adjustments of tare
are minimized and the monitoring of the patient's weight is
more accurate. For example, with the drainage bag off the
weigh frame, the loss of fluids by discharge from the
patient into the drainage bag is accurately reflected in
loss of patient's weight. Similarly, by mounting the I.V.
- I 337076
- - 5a -
bag off the weigh frame, increases in the patient's weight
by virtue of the introduction of the I.V. fluids is
accurately monitored.
The invention provides for changes in tare even
when the incremental change in tare is unknown. In a
particularly preferred embodiment, alarm options may be
provided including an alarm at a remote location such as a
nurse's station, an illuminated alarm, an audible alarm and
no alarm. The alarms provide notification of the patient's
exit from the bed, which is particularly useful for
patient's whose acuity is impaired. The patient's loss or
gain of a predetermined amount of weight can be programmed
to operate the alarm. The invention provides for
displaying of weight in either pound units or kilogram
units. All of the controls for the scale may be battery-
operated and the weight control system provides, on its
display, an indicator for low battery supply.
Brief DescriPtion of the Drawinqs
The several features of the invention will become
more readily apparent from the following detailed
description taken in conjunction with the accompanying
drawings in which:
Fig. 1 is a perspective view of a bed employing
the present invention;
Fig. 2 is a perspective view of the support frame
and weigh frame combination;
Fig. 3 is a cross-sectional view taken along
lines 3-3 of Fig. 2;
Fig 4 is a cross-sectional view taken along
lines 4-4 of Fig. 2; and
Fig. 5 is a plan view of the display for the
control/readout unit associated with the weigh scale.
The bed to which the present invention is applied
is shown in Fig. 1. That bed is more fully described and
claimed in U.S. Patent No. 4,751,754, issued June 21, 1988.
1 3370~6
--6--
The bed has a base frame 10 that is suppor'-
ed on casters 11. Bosses 1 fixed to the base frame
pivotally support the ends of a cantilevered support
- arm 13 and a stabilizer arm 14. The ends of the
cantilevered support arms 13 and the stabilizer arm 14
are pivotally connected to a bracket 15, thereby
providing a parallelogram linkage support ~or the bed.
The bracket 15 is bolted to support frame 16. A
piston and cylinder 20 driving a piston rod 21 is
mounted on the base frame 10 with the piston rod 21
being connected to the support arm 13 by ~eans of a
clevis mount 22. Actuation of the piston and cylinder
20 causes the piston rod 21 to extend and contract,
thereby raising and lowering the parallelogram linkage
and the support frame 16 of the bed.
Referring to Figs. 1-4, the support frame 16
consists of two tubular rectangular section beams 25
joined together by transverse bars 26 mounted at each
end of the beams 25. A weigh frame 30 is ~.ounted on
the support frame 16. The weigh frame consists of two
inverted U-shaped beams 31 that are shorte_ than the
rectangular beams of the support frame. The rectangu-
lar beams of the support frame are nested within theU-shaped beams of the weigh frame with front and rear
portions 33 and 34 of the support beam projecting
beyond the weigh frame 30.
1 337076
.
,
At each corner of the weigh frzme 30, the
weigh frame is supported on the supporl fr~me by a
load cell 35. The load cell is an elongated element
36, containing a strain gauge, not shown, and having a
boss 37 connected by bolts 38 to the inside of the
- rectangular beam 25. Thus, the major portion of the
load cell is cantilevered from the boss 37 presenting
a free end 39. The free end 39 is connected to a
swivel 40 by means of a bolt 41 threaded into the free
end 39 of the load cell. The projecting end or head
of the bolt 4, is a ball 42. The ball sits in a
housing 43 to form a ball joint. The housing has a
female thread 44 that is connected to a male thread 45
on a second housing 46. The second housing 46 re-
ceives a ball 47 to form a second ball joint. Theball 47 is mounted on a pin 48 that is secured to a
clevis mount 49 on a bracket 50.
At each corner of the weigh frame flanges 55
project laterally. The brackets 50 are bolted to said
flanges 55 across the open end of the U-shaped beams
31. Thus, each swivel mounting securely connects the
~ree end of the load cell to the weigh beam 31. The
swivel connection permits limited universal movement
of the weigh frame in the horizontal dlrection,
thereby preventing any binding of the weigh frame with
respect to the support frame. Preferably, a set screw
56 is provided in free end 39 to limit the movement of
the load cell in a downward direction while permittin.s
1 337~`7~
--8--
the load cell to be stressed to the point or reflect-
ing a weigh level well beyorld ~he e~pected loading of
the corner of the weiah frzme, thereby preventing
damage to the load cell. The lcad cell is provided
with suitable strain gauces configurated into a
~heatstone bridge as is conventional. The strain
gauges~~ are connected to a computerized control 58
-~ which in turn is connected to a control/readout unit
60, to be described more fully below. The output of
the strain gauges are read seauentially and then
summed to provide the total weight on the weigh frame_
The weigh frame has two laterally-projecting
brackets 65. A patient support 66 having a head panel
67, a seat panel 68, a thigh panel 69 and a foot panel
is secured by means of the seat panel to the
brackets 65 and, hence, to the weigh frame. The head
panel 67 is hinged to the seat panel 68 and is con-
- nected by a bracket 71 to a piston and cylinder 72
~~ which is secured to a bracket 73 on the weigh frame.
Thus, the piston and cylinder 72 on the weigh frame
causes the raising and lowering of the head panel 67.
The foot panel 70 is pivotally connected to
a bracket 75 which is pivoted to the weigh frame. The
foot panel is hinged to the thigh panel 69 which is in
turn pivoted to the seat panel. A piston and cylinder
76 connects the thigh panel to the weigh frame. The
pistons and cylinders 72 and 76 are connected by
hoses, diagrammatically indicatea at 77 and 78, to 2
1 337076
hydraulic system 79 mounted on the base frame. The
~anipulation of the panels of the patlent support and
manipulation of the support frame are all performed in
a manner as described in U-S- Patent ~ro. 4,751,754
issued June 2~, 1988 and forms no part of the present
-- - invention except to note the pistons and cylinders for
operating the patient support panels are mounted on
the weigh frame and become a part of its tare whereas
the hydraulic system including pump and fluid reser-
voir is mounted on the main frame with only hoses
beir.g connected between the two. It should b~
understood that the manipulation of said panels could
be performed using electric motors mounted on the
weigh frame and a power source mounted on the base,
with conductors connecting the power source to the
weigh frame.
The portions 33 and 34 of the support frame
that project beyond the weigh frame provide elements
directly connected to the main frame for supporting
accessories such as infusion pumps, I.~. bags, drain-
- age bags, headboards and the like. All of those
accessory elements are thus supported separately from
the weigh frame and the weighing system.
The bed as thus described will be outfitted
with a mattress, sheets, pillows, blankets, and the
like. These items become part of the tare. When
these are varied, as by addinq a blan~et or removing
pillow, the tare can be chansed, whether the weight of
1 337075
--10--
the items be known or unknown, by followir.g an easy
sequence of ste~s on the control/readout unit 60.
Further, an attendant can set the controls to provide
an alarm, visual or audible, to warn an attendant that
the patient has lost or gained weight beyond prede-
termined limit, or that the patient has left the bed.
Since---lV bags and drainage bags are supported on the
- support frame 16 and/or bracket 15 and are thus out of
the weighing system, losses from the IV bags and sains
in the drainage bag do not influence the determination
of the patient's true weight.
The alarm is adapted to be connected to a
central nurse station 74 so as to initiate an immedi-
ate response to an emergency situation such as a
patient's falling or climbing out of bed; or a delayed
response for weight gain or loss beyond the pre-set
limit.
The control/readout unit 60 is preferably
-- mounted on the front or foot end of the bed convenient
for reading and manipulating by the attendant.
The panel has a liquid crystal display 80
that will display the nu~bers indicating the weight
and will display the weight units as KG or LB. The
units, KG or LB, are set by the units key 81. The
display will also show one of four modes: OFF, EXIT,
WEIGHT (+), WEIGHT (-). The monitoring mode is
selected by mode key 82. The display will also show
the alarm which is one of three alternatives: silent,
- 1 337076
local, remote. The alarm concit,on is determined by
the alarm key 83. Four digits are displayed to
reflect weight. These digits are controlled by four
digit stepping ke~s: 85 for tenths, 8 6 for units, 8 7
for tens and 8~ for hundreds. The hundreds key
- - sequences the display through 0, 100, 200, 300, 400,
-400, -300, -200, -100, -0, ~0. Thus, by proper
sequencing of the hundreds key, the units can be
changed from plus to minus.
10A read key 90 is provided to activate a
weight reading. A zero key 91 is provided to activat~
a tare reading or effect tare adjustments and a set
key 92 is provided to activate monitoring controls.
The key functions are set forth more particularly as
lS follows:
READ Initiates 5 to 8 sec weight measurement upon
release.
Causes display "+" and preset units, either
LB or KG, as previously set, to blink upon
closure and while measurement is in process.
Signa]s measurement display with a chime.
UNITS Always comes up in previously set units.
Alternately displays in LB or KG upon
contact closure.
Freezes displav when activated
and held during weight display.
~ 1 337076
Resets 10 sec. displa~--hold-timer upon
contact openins.
ZERO *Initiates automatic zero-tare o~ empty bed
when held while touching READ.
- - *Activates digit stepping keys for entry of
known tare change, plus or minus, when held.
*Increments total tare value by difference
between display and memory, when activated
and held during display while then touching
READ.
Recalls total system tare value when acti-
vated and held; displays for 10 sec after
release, or until cancelled by READ or SET.
*All tare operations are protected from
accidental change by dual-key or sequenced
operation.
SET Activates display when held, to show exist-
ing alarm weight value for monitoring modes.
Activates digit stepping keys when held, to
allow settin~ or changing existing alarm
weight value.
Facilitates MODE and ALAR~ setup when held,
by activating display when display is
otherwise inactive. Releasing SET causes
display to clear.
1 337076
-13-
PrGvides memory recall cf last weight when
held while activating READ.
MODE/OFF Selects monitoring mode, shown in display,
and as described:
OFF: Automatically timed monitoring
~-~ functions inactive.
-`- EXIT: Rough weight measurement (+ 0,
-10~ accuracy) taken every 3 to 4
seconds.
Places EXIT alarm if weight
falls below existing alarm-weight
value for two successive
readings.
WT-: Precise weight measurement (+1%
accuracy, +0.1% repeatability)
taken every 10 minutes. Places
weight-loss alarm if weight falls
~- below existing alarm- weight
value for two successive
readings. Last weight value is
stored in memory for recall.
WT+: Precise weight measurement (+1%
accuracy, +0.1% repeatability)
taken every 10 minutes. Places
weight-gain alarm if weight
exceeds existing alarm-weight
1 337076
-14-
value for two successive re2dinss.
Last weight value is stcred in
memorv for recall.
Cancels alarm with single touch; requires
resetting, as before, to re-arm monitoring
- - mode.
-~ Sequences through available settings in
rotation with each touch, or rolls at a l/2
sec. rate if held for l sec.
Skips settings that are not available due t~
hard-wire inhibit or programmed inhibit.
Settable any time a full display is present,
that is, during weight display holding time,
during total tare display holding tlme, or
any time SET is held act,ivated.
ALARM Selects alarm type, shown in the display,
~~ and as described:
SILENT: Flashing yellow LED on Nurse
Panel Facade.
LOCAL: Flashing yellow LED plus audio
beep from Nurse Panel.
REMOTE: Flashing yellow LED plus
room-cancellable call with
identifying audio beep
transmitted through SIDECOM to
nurse station.
1 337376
-15-
During all alarms the preset monitoring
condition (EXIT, WT-, or WT+) flashes in the
display to identify the type of alarm
placed.
Audio tone for EXIT is 400 Hz gated ON for ~
sec., OFF for ~ sec., for WT+ and WT-, a 400
~~ Hz tone gated ON for 2 sec., OFF for 12 sec.
-~ The LED and DISPLAY flash at the same ON/OFF
rate as the audio.
Yellow alarm LED burns steadily anytime a
monitoring mode has been set; then flashes
upon alarm.
Sequences through rotation from SILENT to
LOCAL to REMOTE to SILENT with each touch of
the key, or rolls at a ~ second rate if held
for l second.
Settable any time a full display is present,
that is, during weight display holding time,
~ during total tare display holding time, or anytime SET is held activated.
Alarm placement occurs within ten seconds if
the set weight, when entered, is already in
the alarm condition when the SET key is
released. This alerts the staff while still
in the room.
DIGIT Four (4) digit stepping keys, each
KEYS associated with a single decade numerai of
1 337076
-16-
the display, are used to increment the
display for ZERO and SET, when either of the
latter keys are held.
Dual key activation reduces the opportunity
for accidental changes in tare resulting
from touching a wrong key.
~~ ~undreds sequence is +0, +1, +2, +3, +4, -4,
~ -3, -2, -1, -0, etc; tens, units and tenths
step incrementally from 0 to 9 and then jump
back to zero without a carryover into the
next decade.
Digits step with each touch of the key, or
roll at a ~ second rate if held more than 1
second.
BAT Annunciator flashes in display when charge
is within 5 to 15% of depletion. Scale is
fully functional yet with this reserve, and
meets all accuracy requirements. Automatic-
ally places a nurse call every 10 minutes
when BAT display is activated.
NOTE: In tare or recall operations involving
holding ZERO or SET while momentarily
activating READ, there will be a tendency to
release simultaneously. To prevent
activation of an unintentional function when
READ is released last, controls are designed
such that if READ opens last, bu~ wit;~in -
1 3~7076
sec. of ZERO or SET opening, the operation
will not be affected.
The steps in the various procedures for
weighing the patient, changing the tare, changing the
alarm, etc., are as follows:
I0
~ ~ 337076
--18--
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~ 1 337076
--19--
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- 1 337076
--20--
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1 337076
- --21--
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- 1 337076
The control system a~mits of the possibility
of makinq an initial setting t~at eliminates the bed
tare and the patient's weight. Thus, the display will
provide a continuous display of the change in
patient's weight.
- - It will be appreciated that while the
preferred embodiment of the invention is described in
connection with hospital beds, the invention may be
adapted for use in connection with other forms of
weigh apparatus, such as patient supporting wheel-
chairs, livestock scales, or the like.
From the above disclosure of the general
principles of the present invention and the preceding
detailed descript~on of a preferred embodiment, those
skilled in the art will readily comprehend the various
modifications to which the present invention is
susceptible. Therefore, we desire to be limited only
by the scope of the following claims and equivalents
thereof:
