Note: Descriptions are shown in the official language in which they were submitted.
CA 02374118 2002-03-01
-1-
Title: PATIENT LOWERING DEVICE
FIELD OF THE INVENTION
This invention relates generally to the field of mobility devices, and
more particularly to patient lifting and carrying devices of the type that
may be used to raise or lower a physically disabled person for the
purpose of moving them.
BACKGROUND OF THE INVENTION
Personal lift or patient lift devices have been known and used in
the past for the purpose of assisting with the mobility of otherwise
immobilized patients. An attendant may help physically disabled patients
who are elderly, or who may have suffered a traumatic injury, stroke or
one form of illness or another, and who are unable to move about.
However, often such patients may be too heavy to lift or the attendant
may not have enough strength to help the patient move. This can be
especially true for disabled patients who have reduced mobility but
otherwise normal bodily functions. Getting up, going to the bathroom or
having a bath, for example, can be difficult for such patients. Patient
carrying devices have been used in the past, which include a strap or
chain hanging down from a motor assembly, which in turn may be
suspended from a movable stand, or from a rail carriage riding along an
overhead track. An overhead track can be organized to extend from over
a bed and into, for example, an adjoining bathroom area, to permit the
patient to be raised, suspended, and then moved along the track to a
position where they can be lowered into the bathtub for the purposes of a
bath or onto a toilet.
Typically such patient carrying devices are provided with an electric
lift motor, which provides the power to lift the patient. In operation, such a
device will be used to lift the patient, transport him laterally, and lower
the
patient. However, a problem can arise in the event of a malfunction or
power failure, namely, that the patient cannot be lowered using the motor,
CA 02374118 2002-03-01
-2-
and thus may be stranded above the floor in the patient harness.
Solutions to this problem have been attempted. For example, US
patent number 5,038,425 issued in 1991 to Merry discloses a device for
raising and lowering a patient from a bed and for moving the patient to
other locations. The device includes a motor for lifting and lowering the
patient via a gearing mechanism. Also included is a hand crank to
actuate the gearing mechanism in the event of a power failure. Thus, if
the patient is suspended in mid-air when the power fails, it is possible to
lower the patient using the hand crank, even though the electric motor is
unavailable because of the power failure.
This device suffers from a number of deficiencies. First, the hand
crank is by necessity located adjacent to the motor's gearing mechanism,
because the hand crank operates through that mechanism. Thus, in
cases where the motor is mounted high off the floor, reaching the hand
crank to lower the patient can be inconvenient and awkward. Second, the
hand crank feature is not easily or inexpensively retrofittable onto an
existing patient carrying device. Therefore, if there is a system in place
which does not have the hand crank feature, it could be necessary to
replace the whole system in order to obtain the benefits of the hand crank.
Such a replacement would also be expensive. Third, while the hand
crank can be used to lower the patient in the event of a power failure, the
hand crank simply actuates the gears that would otherwise have been
actuated by the motor. In the event of other types of malfunctions, such
as, for example, the gear machanism seizing up, the hand crank would
not be effective for lowering the patient.
SUMMARY OF THE INVENTION
Therefore, what is desired is a patient lowering device that
will allow a patient that has been lifted by a patient carrying device to be
lowered in the event of a power failure, and preferably, in the event that
the patient carrying device malfunctions. Preferably, the patient lowering
device will be positionable such that reaching and using the patient
lowering device is straightforward and convenient. Also, preferably, the
CA 02374118 2002-03-01
-3-
patient lowering device will be installable on existing patient carrying
devices.
Therefore, according to one aspect of the invention, there is
provided, in a patient-carrying device comprising a primary patient
manipulation mechanism for lifting, lowering or laterally moving a patient,
wherein the primary patient manipulation mechanism is supportable from
a mechanism support, and a patient harness coupled to the primary
patient manipulation mechanism, an improvement comprising a patient
lowering device positioned intermediate the harness and the primary
patient manipulation mechanism, the patient lowering device comprising:
(1) an extendable patient bearing means for bearing the weight
of the patient, the patient bearing means being coupled to the patient
harness and to the primary patient manipulation mechanism; and
(2) an actuator, coupled to the patient bearing means for
actuating the patient bearing means;
whereby, if the primary mechanism malfunctions or is unavailable
while the patient is being transported, the patient can be lowered to a
chair, a bed or the ground by means of the patient lowering device.
According to another aspect of the invention, there is provided a
patient lowering device for lowering a patient being carried by a patient
carrying device which includes a primary patient manipulation mechanism
and a patient harness, the lowering device comprising:
(1) an extendable patient bearing means for bearing the weight
of the patient, the patient bearing means being adapted to be coupled to
the patient harness and to the primary patient manipulation mechanism,
and to be positioned intermediate the harness and the mechanism; and
(2) an actuator, coupled to the patient bearing means, for
actuating the patient bearing means without actuating the primary
mechanism;
whereby, if the primary mechanism malfunctions or is unavailable
while the patient is being transported, the patient can be lowered to a
chair, a bed or the ground by means of the patient lowering device.
CA 02374118 2002-03-01
-4-
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described, by way of example only, with
reference to the drawings which depict a preferred embodiment of the
invention, and in which:
Figure 1 is a perspective view of a patient-carrying device including
a patient lowering device;
Figure 2 is a perspective view of the patient-carrying device when
the patient lowering device is being prepared for use;
Figure 3 is a perspective view of the patient-carrying device
showing the patient lowering device in operation;
Figure 4 is a perspective view of the patient lowering device with
the cover on;
Figure 5 is a perspective view of the patient lowering device
without the cover;
Figure 6 is a perspective view of an inner portion of the patient
lowering device shown without the cover and housing; and
Figure 7 is a cross-sectional view of the patient lowering device
along line 7-7 of Figure 4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figures 1-3 show a patient-carrying device comprising a primary
patient manipulation mechanism 12, typically including a motor and
gearing system (details not shown), an extendible primary weight bearing
element in the form of a lift strap 14, a patient lowering device 16, and a
patient holder in the form of a carry bar 18, a patient harness 20 and a
swivel element 24. The patient carrying device is mounted on a support in
the form of a track 22. Typically, the track 22 will be mounted on some
kind of chassis or frame (not shown) which could include the ceiling or a
cross-bar positioned under the ceiling.
In typical operation, the patient-carrying device is used to lift, lower
or laterally transport a patient (not shown). To lift the patient, the patient
is placed in the harness 20. Then, by use of a controller (not shown), the
motor is activated so as to cause the lift strap 14 to be raised by the motor
CA 02374118 2002-03-01
-5-
12 to which the lift strap 14 is coupled.
The lift strap 14 is coupled to the patient-lowering device 16, which
is in turn coupled via the swivel element 24 and the carry-bar 18 to the
patient harness 20. As the lift strap 14 is raised by the motor 12, the
hamess 20 is raised, thus lifting the patient.
To transport the patient laterally, the controller is used to activate
the motor so as to move the patient carrying device along the track 22.
The result is that the patient is held in the harness and transported
laterally.
Similarly, to lower the patient in normal operation, the controller is
activated in order to extend the lift strap 14. The patient harness 20 is
lowered, thus lowering the patient.
It will be appreciated that the strap 14 acts as an extendible
primary weight bearing element. When the motor is used to lower the
patient, the strap 14, bearing the weight of the patient, is extended from
the mechanism 12. The strap 14 is also movable upward. Thus, when
the patient is lifted, the strap 14 bearing the patient's weight, is moved
upward, preferably by being retracted into the mechanism 12 by the motor
12.
In the event that it is impossible, inconvenient or not preferred to
lower the patient by means of the primary patient manipulation
mechanism 12 (for example, if the motor is broken or otherwise
malfunctioning, or if there is a power failure), the patient lowering device
16 provides an alternative for lowering the patient.
The patient lowering device 16 includes a base 26, which includes
a base coupler in the form of a base bore 28. The base bore 28 is sized
and shaped to receive a base shaft 30 which carries the swivel element
24. Thus, the base 26, and in particular the base coupler included therein,
permits the patient lowering device 16 to be coupled at its bottom via the
swivel element 24 and the carry-bar 18 to the harness 20.
The patient lowering device 16 further includes a top portion 32
and a housing 34. The top portion 32 includes a top coupler which
comprises, in the preferred embodiment, a pair of top bores 36 for
CA 02374118 2002-03-01
-6-
receiving a top shaft 38. The top shaft 38 acts as an attachment point for
the lift strap 14 which is looped around the shaft 38 and fastened. Thus,
when the lift strap 14 is attached to the top portion 32, the patient lowering
device is coupled to the primary patient manipulation mechanism 12, and
positioned intermediate the patient harness 20 and the mechanism 12.
The patient lowering device 16 further includes a cover 40, which
includes an actuator access in the form of a cover bore 42, and a tamper-
resistant cap 44. The cover 40 is attached to the patient lowering device
16 by means of cover threading 46 positioned on the housing 34 adjacent
the base 26. The cover threading 46 cooperates with inner threading (not
shown) positioned on the inner bottom portion of the cover 40. Thus, the
cover 40 can be attached to the patient lowering device 16 by screwing it
onto the cover threading 46 and removed by unscrewing it.
The patient lowering device 16 further comprises an actuator, for
actuating the device 16, which in the preferred embodiment takes the
form of a head 48 attached to a worm shaft 50 housed within the housing
34. The worm shaft 50 is rotatably mounted within a bearing 52 carried by
the housing 34. The worm shaft 50 has a threaded surface comprising
spiral threading 55.
The patient lowering device 16 further comprises a first driven
element in the form of gear 56 having teeth 58. The gear 56 is positioned
such that the teeth 58 are engaged by the threading 55. The gear 56 is
mounted on the housing shaft 60, which is carried by the housing 34.
Because of the engagement between the teeth 58 and the threading 55,
when the shaft 50 is rotated, the threading 55 acts on the teeth 58,
pushing on the teeth 58 and driving the gear 56, causing it to rotate
about the shaft 60.
Also mounted on the shaft 60 is a patient-bearing-means-carrier,
sized, shaped and positioned to extendibly carry a patient bearing means
and preferably in the form of a spindle 62. Wound around and carried by
the spindle 62 is an extendible patient bearing means, for bearing the
weight of the patient, in the form of the cable 64. Thus, before actuation,
the spindle 62 extendibly carries the cable 64 in an unextended state
CA 02374118 2002-03-01
-7-
(that is, carries the cable 64 in a manner that permits the cable 64 to be
extended). At one end, the cable 64 is attached to the spindle 62. At its
other end, the cable 64 is attached to the underside of the top portion 32.
As can be seen from the above description, in the preferred
embodiment, the housing 34 carries, directly or indirectly, the head 48, the
bearing 52, the shaft 50, the gear 56, the shaft 60, the spindle 62 and the
cable 64.
In the preferred embodiment, the patient lowering device will
include an infection control seal 66 positioned between the top portion 32
and the cover 40. Preferably, the infection control seal 66 will be in the
form of silicone caulking. The purpose of the infection control seal is to
prevent microbes which may be present under the cover 40 from
migrating, or being passed, out from under the cover 40, particularly
through the place where the cover 40 meets the top portion 32. As the
patient lowering device will often be in used in hospitals where patients
who are susceptible to disease are present, it is preferred to include an
infection control seal that will inhibit the migration of microbes from inside
the cover 40 to outside it.
It will be appreciated that, though the use of silicone caulking as
the infection control seal is preferred because it is effective and relatively
easy to apply, other seals may be used. For example, a removable or
breakable plastic film over the cover 40 may be used. What is important
for the infection control seal is that it be effective in inhibiting the
migration
of microbes from under the cover 40 while the cover 40 is covering the
patient lowering device 16.
It can now be appreciated how the patient lowering device 16 is
preferably operated. First, the tamper-resistant cap 44, which is typically
positioned within the cover bore 42 in an interference fit, is removed from
the cover bore 42. This can preferably be accomplished either by using a
plier to grip the tamper-resistant cap 44 and remove it from the cover bore
42, or simply by a person applying pressure with his thumb to pop the
tamper-resistant cap 44 out. It will be appreciated that the tamper-
resistant cap 44 can be placed in the cover bore 42 by other methods
CA 02374118 2002-03-01
-8-
than an interference fit, for example, by screwing it in. In such a case, the
tamper-resistant cap 44 would be removed by unscrewing it. What is
important is that the cover 40 and cap 44 impede access to the head 48,
thus providing resistance to tampering.
Once the tamper-resistant cap 44 is removed, the cover bore 42
provides access to the head 48. Preferably, the head 48 is a six-sided
(hexagonal) head which is sized and shaped to receive a hexagonal
actuating tool 68 which can be used to turn the head 48.
Preferably, the head 48 is first turned one or two turns in a non-
actuating direction. This has the effect of causing the shaft 50 to rotate,
which causes the the gear 56 to rotate, which in turn causes the spindle
62 to wind the cable 64 more tightly. This draws the top portion 32
downward relative to the cover 40, thus breaking the infection control seal
66. Also, this action removes any slack that may be present in the cable
64, such that, when the lowering process begins, there is less likely to be
a sudden release of the cable 64 which would cause a sudden and
unpleasant drop for the patient.
Then, the cover 40 is unscrewed from the base 26 and raised so
as to remove the cover 40 from the lowering device 16. The tool 68 is
then used to rotate the head 48 in the actuating direction. When the head
48 is rotated, the threading 55 exerts a force on the teeth 58 causing the
gear 56 to rotate in a actuating direction. The spindle 62, which is also
carried by the shaft 60 and is attached to the gear 56, is rotated so as to
unwind and thus extend the cable 64, which acts as the patient bearing
means. As the head 48 is rotated more, the cable 64 extends further and
further, thus lowering the patient. It will be appreciated that the cable 64
is attached to the top portion 32, which is itself attached to the lift strap
14.
Thus, as the cable 64 is extended, it lowers the patient downward from
the top portion 32 until the patient is lowered sufficiently to be placed in a
wheelchair, bed or other convenient location.
It will be appreciated that the patient lowering device 16 of the
preferred embodiment is self-locking. This is because the teeth 58 are
engaged with the threading 55 on the shaft 50. The threading 55 runs in
CA 02374118 2002-03-01
-9-
a direction transverse to the direction of movement of the teeth 58. As a
result, when the shaft 50 is not being rotated, the threading 55 holds the
teeth 58 in place, and the threads 55 act as a lock on the gear 56, and
therefore on the spindle 62 and the cable 64. When the shaft 50 is
rotated, the threading 55 exerts a force on the teeth 58 causing the gear
56 to rotate about the shaft 60. It will be appreciated that the invention
comprehends the lowering device 16 having self-locking features other
than the threads 55 and teeth 58 of the preferred configuration described
above. For example, the self-locking feature could comprise a friction
brake or friction lock which prevents the cable 64 from unwinding, but is
released when the device is actuated. What is important for the self-
locking features is that they lock the patient-bearing means unless the
patient bearing means are being actuated.
In the preferred embodiment, the patient lowering device further
includes a backup lock in case the self-locking features of the emergency
lowering device 16 fail for some reason. The backup lock includes a
locking arm 70, a biasing spring 72 and a stop 74. The locking arm 70 is
pivotally mounted to the spindle 62 by a screw 76. When the patient
lowering device16 is not being actuated, or when it is being actuated so
as to cause the spindle 62 to rotate at a moderate speed as a result of the
actuation, the biasing spring 72, which is attached to the spindle 62 and
the locking arm 70, biases the locking arm 70 to a position which permits
the rotation of the spindle. However, in the event that the self-locking
features of the patient lowering device 16 fail, and the spindle begins to
rotate at a high rate of speed, the centrifugal force associated with the
rotating of the spindle 62 will cause the locking arm 70 to pivot outward
and catch on the stop 74 which is mounted to the housing. The stop 74 is
positioned to catch the arm 70 when it pivots outward. The limiter 75,
mounted on the side of the spindle 62, prevents the arm 70 from pivoting
so far that the arm 70 rotates past the stop 74 and allows the spindle 62
to continue rotating. Thus, when the spindle 62 is rotating quickly enough
to cause the arm 70 to pivot outward, the limiter 75 and the stop 74
combine cause the arm 70 to catch the stop 74 and lock the spindle. The
CA 02374118 2002-03-01
-10-
biasing spring 72 is adapted such that its biasing force is small enough to
be overridden by the centrifugal force when the rotation is sufficiently fast
such that backup locking is warranted, but large enough to bias the arm
70 to an unlocked position otherwise.
Once the patient has been lowered using the patient lowering
device, the cable 64 can be rewound around the spindle 62 using the
head 48 and the tool 68. A new infection control seal 66 can be applied to
the cover 40, and the cover can be screwed on to the base 26 so as to
position the bore 42 over the head 48, such that access to the head 48 is
available through the bore 42. Then, the tamper-resistant cap 44 can be
replaced in the cover bore 40, and the patient lowering device is thus
ready for use once again if needed.
Preferably, the cable 64 will be a steel cable, and most preferably a
stainless steel cable, most preferably covered by a plastic sheathing.
Thus, the cable 64 is preferably composed at least in part of stainless
steel to provide both strength and resistance to corrosion, while still
providing sufficient flexibility for winding.
It will be appreciated that, though the preferred extendable patient
bearing means is the cable 64 described above, the extendable patient
bearing means need not be a cable. Rather, the invention comprehends
the extendable patient bearing means being any element which can be
extended to lower the patient, and can bear the weight of the patient.
Thus, for example, the patient bearing means could comprise a strap that
is extended by being unwound from around a spindle. Alternatively, the
extendable patient bearing means could be a series of rods that can be
controllably extended telescopically relative to one another to lower the
patient. As another example, the patient bearing means could be a series
of bars that are connected end to end and are folded until the patient
lowering device 16 is actuated, at which time they unfold, thus extending
and lowering the patient while bearing the weight of the patient.
It will also be appreciated that, though the preferred actuator is the
head 48 attached to the worm shaft 50 as described above, the actuator
need not take this preferred form. Rather, the invention comprehends any
CA 02374118 2002-03-01
-11-
actuator which functions to cause the extendable patient bearing means
to extend, thus lowering the patient. For example, the patient lowering
device 16 could include a friction brake which, when the lowering device
16 is not in use, prevents the spindle 62 from unwinding the cable 64.
The actuator, in such a case, could be in the form of a brake release
which, when actuated, gradually lowers the frictional force braking the
spindle until it slowly starts to unwind the cable. What is important is that
the actuator functions to cause the extendable patient bearing means to
extend and lower the patient.
It will be appreciated that the invention comprehends means to
resisting tampering other than the preferred form of cover and tamper-
resistant cap described above. For example, the cover could be made
tamper resistant by providing a key lock that must be opened in order to
remove the cover and access the actuator.
It will further be appreciated that, because the lowering device 16 is
preferably positioned apart from the primary mechanism 12, and thus
intermediate the primary mechanism 12 and the harness 20, the lowering
device is more conveniently located and easier to reach. The lowering
device 16 is preferably located adjacent the patient just above the
harness 20 and the bar 18; it is preferabiy not located adjacent the
primary mechanism 12, and therefore not within the same casing as the
primary mechanism 12. In such a case, the lowering device 16 is not
located out of reach near the ceiling, but rather is located near the patient
to allow for easy operation.
Also, the lowering device is preferably couplable as described
above to the lift strap 14 and the harness 20. Thus, if a traditional patient
carrying device is in use, which includes a lift strap and harness, it is
usually possible to conveniently and cheaply retrofit the lowering device
16 into the patient carrying device. Doing so would simply involve
detaching the strap from the harness, attaching the strap to the shaft 38,
and attaching the harness to the base 26. It will be appreciated that, even
in embodiments other than the one described herein, it is preferred that
the patient lowering device have top and bottom couplers sized, shaped
CA 02374118 2002-03-01
-12-
and positioned to facilitate retrofitting of the device 16 to an existing
patient carrying device.
Furthermore, it will be appreciated that the preferred lowering
device 16 operates separately and independently from the gearing and
other mechanical components contained in the primary mechanism 12.
Thus, if the primary mechanism's gearing seizes up or malfunctions, the
user of the device 16 is not dependent on the malfunctioning gearing.
Rather, the preferred lowering device 16 has its own actuator, extendible
patient-bearing means and gearing mechanism for lowering the patient.
While the foregoing embodiments of the present invention have
been set forth in considerable detail for the purpose of making a complete
disclosure of the invention, it will be apparent to those skilled in art that
various modifications can be made to the device without departing from
the broad scope of the invention as defined in the attached claims. Some
of these variations are discussed above and others will be apparent to
those skilled in the art. For example, the back-up-lock described above
can be a lock other than the centrifugal lock described above. What is
considered important in the present invention is to provide a patient
lowering device that allows the patient to be lowered when the patient
carrying device is not available.
