Abstrict A tilt-preventing mechanism for a height-adjustable bed of the
type including a mattress which is supported in a substantially
horizontal position on a support structure which can be moved up
and down by means of an electric motor. When the mattress, or its
support structure, encounters during its up or down movement an
obstruction which causes one region of the mattress to discontinue
its movement while other regions continue to move with attendant
tilting of the mattress, a position-sensitive switch arrangement
of the mechanism senses the tilting and, once the degree of tilt
approaches or reaches the limit of acceptable tilting, inactivates
the motor so that the tilting is not aggravated any more. The position-sensitive
switch arrangement includes one or two switches arranged normal
to the expected axis or axes of tilting and moving with the support
structure. The position-sensitive switches can be constructed as
mercury switches.
Claims What is claimed as new and desired to be protected by Letters Patent
is set forth in the appended claims; I claim:
1. An anti-lateral tilt-preventing adjustable bed, especially for
use in hospitals and similar institutions for bedridden patient
care, comprising:
a mattress having a longitudinal axis that is parallel to and extends
along a predetermined plane at least when a patient resting thereon
is to assume a prostrate position;
a support for said mattress;
means for maintaining said support at an adjustable distance above
ground in a plurality of positions in which said predetermined plane
extends substantially horizontally, with freedom of movement of
said support substantially normal to said predetermined plane, and
at least limited freedom of undesired tilting in either circumferential
direction about said longitudinal axis, with attendant angular deviation
of said predetermined plane from the horizontal;
means for moving said support substantially normal to said predetermined
plane between said positions with the possibility of undesired tilting
of said support in either circumferential direction about said longitudinal
axis upon application of external forces thereto laterally and radially
of said longitudinal axis at least during the operation of said
moving means, including a motor and means for energizing said motor
when adjustment of said distance is desired; and
anti-lateral-tilt means including a level-sensitive switch for
sensing the magnitude of said angular deviation when said switch
is tilted from the horizontal, and for inactivating said energizing
means when said magnitude exceeds a predetermined value selected
to prevent the patient from tending to roll in a radial direction
off the side of the bed.
2. The tilt-preventing adjustable bed as defined in claim 1 wherein
said motor is an electric motor; wherein said energizing means includes
a source of electric energy and an electric circuit connected to
said source and having said electric motor interposed therein; and
wherein said level-sensitive switch is incorporated in said electric
circuit between said source and said electric motor and is mounted
on said support for movement therewith.
3. A tilt-preventing adjustable bed, especially for use in hospitals
and similar institutions for bedridden patient care, comprising:
a mattress extending along a predetermined plane at least when
a patient resting thereon is to assume a prostrate position;
a support for said mattress;
means for maintaining said support at an adjustable distance above
ground in a plurality of positions in which said predetermined plane
extends substantially horizontally, with freedom of movement of
said support substantially normal to said predetermined plane, and
at least limited freedom of tilting about at least one axis that
is parallel to said predetermined plane and above another axis substantially
normal to said axis, with attendant deviation of said predetermined
plane from the horizontal;
means for moving said support substantially normal to said predetermined
plane between said positions with the possibility of tilting of
said support about said axis upon application of external forces
thereto at least during the operation of said moving means, including
an electrical motor and means for energizing said motor when adjustment
of said distance is desired, said energizing means including a source
of electric energy and an electric circuit connected to said source
and having said electric motor interposed therein; and
anti-tilt means for sensing the magnitude of said deviation and
for inactivating said energizing means when said magnitude exceeds
a predetermined value, said sensing and inactivating means including
position-sensitive switching means incorporated in said electric
circuit between said source and said electric motor and mounted
on said support for movement therewith, said switching means including
at least two position-sensitive switches each sensitive to the tilting
of said support about a different one of said axes.
4. The tilt-preventing adjustable bed as defined in claim 3 wherein
at least one of said switches is a mercury switch extending substantially
normal to one of said axes and substantially parallel to said predetermined
plane.
5. The tilt-preventing adjustable bed as defined in claim 4 wherein
the other of said switches is also a mercury switch extending substantially
normal to the other of said axes and substantially parallel to said
predetermined plane.
6. The tilt-preventing adjustable bed as defined in claim 3 wherein
said switches are arranged in said electric circuit in series with
one another and with said electric motor.
7. An anti-lateral tilt-preventing mechanism for an adjustable
bed of the type including a mattress extending along a longitudinal
axis, and a drive for adjusting the elevation of said mattress,
said mattress being undesirably angularly tiltable in either circumferential
direction about said longitudinal axis upon application of external
forces laterally and radially of said longitudinal axis to said
mattress, said mechanism comprising:
means including a level-sensitive switch for sensing the magnitude
of the undesirable angular tilt about said longitudinal axis; and
means for inactivating said drive when said switch is tilted and
when said magnitude of undesirable angular tilt exceeds a predetermined
value selected to prevent a person resting on the mattress from
tending to roll in a radial direction off the side of the bed.
8. The mechanism as defined in claim 7 wherein said level-sensitive
switch is a position-sensitive switch operatively connected to said
drive.
9. An anti-lateral tilt-preventing adjustable bed, especially for
use in hospitals and similar institutions for bedridden patient
care, comprising:
a mattress having a longitudinal axis that is parallel to and extends
along a predetermined plane at least when a patient resting thereon
is to assume a prostrate position;
a support for said mattress;
means for maintaining said support at an adjustable distance above
ground in a plurality of positions in which said predetermined plane
extends substantially horizontally, with freedom of movement of
said support substantially normal to said predetermined plane, and
at least limited freedom of undesired tilting in either circumferential
direction about said longitudinal axis, with attendant angular deviation
of said predetermined plane from the horizontal;
means for moving said support substantially normal to said predetermined
plane between said positions with the possibility of undesired tilting
of said support in either circumferential direction about said longitudinal
axis upon application of external forces thereto laterally and radially
of said longitudinal axis at least during the operating of said
moving means, including an electric motor and means for energizing
said motor when adjustment of said distance is desired, said energizing
means including a source of electric energy and an electric circuit
connected to said source and having said electric motor interposed
therein; and
anti-lateral-tilt means for sensing the magnitude of said angular
deviation from the horizontal and for inactivating said energizing
means when said magnitude exceeds a predetermined value selected
to prevent the patient from tending to roll in a radial direction
off the side of the bed, said sensing and inactivating means including
position-sensitive switching means incorporated in said electric
circuit between said source and said electric motor and mounted
on said support for movement therewith, said switching means including
at least one mercury switch extending substantially normal to said
axis and substantially parallel to said predetermined plane.
Description BACKGROUND OF THE INVENTION
The present invention relates to adjustable beds in general and,
more particularly, to a tilt-prevention mechanism for use in adjustable
beds of the type used in hospitals.
Various constructions of adjustable and/or tiltable beds and similar
equipment are already known, for instance, from the U.S. Pat. Nos.
3220019; 3371358; 3373453; 3462772; 3611453; 3694830;
3972081 and 4324010. In many instances, the mattress of an adjustable
hospital bed can be adjusted not only as to its elevation from the
ground, but also as to its shape, i.e. it can be contoured to afford
comfort to, or aid in the recovery of, the patient occupying the
bed. The positional adjustment is usually achieved by means of an
electric motor and a transmission arrangement which converts the
rotation of the output shaft of the motor into displacement of the
desired portions of the bed.
Experience with the adjustable beds of the conventional constructions
has shown that, as advantageous as they may be in various respects,
they all suffer from a serious drawback which resides in the fact
that, when an external obstruction hampers the displacement of the
mattress and/or its movable support structure at any region thereof,
the remainder of the mattress and its support structure continues
its movement unimpeded, so that the mattress begins to tilt, typically
toward one of the sides of the bed, and continues tilting unless
the operation of the motor is discontinued by the patient or an
attendant or nurse, until the degree of the lateral tilt is such
that the patient may be thrown against a raised side guard rail
of the bed, or if the guard rail is lowered, the patient may be
caused to fall off the bed. This, of course, is highly undesirable,
since it can result in injury to the patient, aggravation of an
already existing condition, or disconnection of various life-support
apparatus with attendant grave consequences. Of course, this possibility
could be avoided if the attendants or nurses were paying attention
not only to the operation of the bed, but also to the presence of
possible obstructions in the path of movement of the adjustable
part of the hospital bed. Unfortunately, this cannot always be assured,
so that it occasionally happens that the mattress of an adjustable
bed moves into its undesirable tilted position, and the patient
is at least inconvenienced, if not injured.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to
avoid the disadvantages of the prior art.
More particularly, it is an object of the present invention to
provide a tilt-prevention mechanism for an adjustable bed, particularly
a hospital bed, which does not possess the disadvantages of the
conventional beds of this type.
Still another object of the present invention is to provide a height-adjustable
bed with a mechanism for avoiding undesirable tilting of the bed
during the raising and/or the lowering thereof.
It is yet another object of the present invention so to design
the mechanism of the above type as to be simple in construction,
inexpensive to manufacture, easy to use and install in existing
hospital beds, and reliable in operation nevertheless.
A concomitant object of the present invention is to develop a mechanism
for use on the bed of the above type which would restrict the extent
of tilting of the bed to an acceptable degree, and discontinue the
movement of the bed once this degree is reached.
In pursuance of these objects and others which will become apparent
hereafter, one feature of the present invention resides in a tilt-prevention
mechanism for use in an adjustable bed, especially for use in hospitals
and similar institutions for bedridden patient care, the bed comprising
a mattress extending along a predetermined plane at least when a
patient resting thereon is to assume a prostrate position; a support
for the mattress; means for maintaining the support at an adjustable
distance above ground in a plurality of positions in which the predetermined
plane extends substantially horizontally, with freedom of movement
of the support substantially normal to the predetermined plane,
and at least limited freedom of tilting about at least one axis
that is parallel to the predetermined plane, with attendant deviation
of the predetermined plane from the horizontal; and means for moving
the support substantially normal to the predetermined plane between
the aforementioned positions with the possibility of tilting of
the support about the aforementioned axis upon application of external
forces thereto at least during the operation of the moving means,
the moving means including a motor and means for energizing the
motor when adjustment of the distance is desired. The tilt-prevention
mechanism itself advantageously comprises means for sensing the
magnitude of the deviation and for inactivating the energizing means
when the magnitude exceeds a predetermined value.
An advantage of the mechanism as described so far is that the sensing
and inactivating means discontinues the operation of the moving
means, so that the degree of tilt cannot exceed a predetermined
value which is well within the acceptable range, that is, within
the range in which the patient is only mildly inconvenienced by
the tilt, but in which no danger of patient's shifting or rolling
under the influence solely of gravitational forces exists.
According to an advantageous aspect of the present invention, the
motor is constructed as an electric motor; the energizing means
includes a source of electric energy, and an electric circuit connected
to the source and having the electric motor interposed therein.
Then, the sensing and inactivating means of the mechanism advantageously
includes position-sensitive switching means incorporated in the
electric circuit between the source and the electric motor and mounted
on the support for movement therewith. This results in a particularly
simple and otherwise advantageous construction since the operation
of the electric motor can be easily controlled, for instance, by
a high-voltage switch which is, in turn, included in the aforementioned
circuit that is operated at relatively low voltage under these circumstances.
Advantageously, the switching means includes at least one mercury
switch that extends substantially normal to the aforementioned axis
and substantially parallel to the predetermined plane. However,
when the maintaining means also gives the support freedom of tilting
about another axis substantially normal to the aforementioned axis,
the switching means includes at least two position-sensitive switches
each sensitive to the tilting of the support about a different one
of the aforementioned two axes. Then, at least one of such switches
is a mercury switch extending substantially normal to one of the
axes and substantially parallel to the predetermined plane. However,
it is also advantageous when the other of the switches is also a
mercury switch extending substantially normal to the other of the
axes and also substantially parallel to the predetermined plane.
It is particularly advantageous, especially as far as the simplicity
of the arrangement is concerned, when the switches are arranged
in the electric circuit in series with one another and with the
electric motor.
The novel features which are considered as characteristic of the
invention are set forth in particular in the appended claims. The
improved tilt-prevention mechanism itself, however, both as to its
construction and its mode of operation, together with additional
features and advantages thereof, will be best understood upon perusal
of the following detailed description of certain specific embodiments
with reference to the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a perspective view of a hospital bed embodying the present
invention, and its environment;
FIG. 2 is a top plan view of a fragmentary detail of a frame of
the bed of the present invention, taken along the plane 2--2 of
FIG. 1;
FIG. 3 is a somewhat enlarged longitudinal sectional view through
a mercury switch used in the arrangement of the present invention,
taken along the line 3--3 of FIG. 2 and with the frame in a desired
horizontal position; and
FIG. 4 is a view similar to that of FIG. 3 but with the frame in
an undesirably tilted position.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawing in detail, and first to FIG. 1 thereof,
it may be seen that the reference numeral 1 has been used therein
to identify a hospital bed constructed in accordance with the present
invention, in its entirety. The bed 1 comprises, as its main components,
a headboard 2 a footboard 3 a frame 4 which interconnects the
headboard 2 with the footboard 3 to constitute a support therewith,
a boxspring 5 which is supported on the frame 4 and a mattress
6 which rests on the boxspring 5. However, it will be appreciated
that, if desired, the boxspring 5 could be omitted and then the
mattress 6 would rest directly on the frame 4 and/or on planks or
spring mesh spanning the opening of the frame 4 as usual. Also,
instead of or in addition to the frame 4 one could use a substantially
plate-shaped support structure of, for instance, plyboard or particle
board or the like, to support either the boxspring 5 or the mattress
6 thereon. Both the headboard 2 and the footboard 3 are shown to
be supported on respective casters, as also well known, to give
the bed 1 mobility over the floor on which it is supported.
Optionally, and as also shown in FIG. 1 the bed 1 can be equipped,
at least on one of its lateral portions, with a guard rail 8 which
is shown to be mounted on the headboard 2 and on the footboard 3
by means of respective brackets 9. If desired, the brackets 9 can
be so constructed, in accordance with well known principles, that
the guard rail 8 can be moved relative to the headboard 2 and the
footboard 3 in the vertical direction, to adjust the extent to which
the guard rail 8 extends above the upper plane of the mattress 6.
Thus, if need be, the guard rail 8 can be moved towards its upper
position in which it confines the patient in the bed 1 against unintentional
rolling off the bed 1 during sleep or the like, or towards its lower
position to permit the patient to sit on the edge of the bed 1 and,
if desired, to rise from the bed 1 and walk away, if the patient's
faculties permit this. A stool 10 may be positioned close to the
bed 1 to help the patient in this task or to let the patient rest
his or her feet thereon when sitting on the edge of the bed 1 with
the legs depending downwardly. Also, a nightstand 11 may be arranged
next to the bed 1 for use by the patient and/or the nursing staff.
The frame 4 or its equivalent as described above is mounted on
the headboard 2 and the footboard 3 or on any construction which
interconnects the headboard 2 and the footboard 3 and constitutes
a solid base therewith, for movement in the vertical direction,
so that the elevation of the mattress 6 above ground can be adjusted
as desired. So, for instance, it may be desired to raise the mattress
6 and its supporting structure 4 and 5 when the patient is to be
examined in bed 1 or when the nursing staff or attending physician
has to perform certain operations involving the patient, such as
introduction of intravenous or nasal tubes or other tasks frequently
performed in hospitals, to assure unproblematical performance of
such tasks in view of their performance at the most advantageous
elevation. Moreover, it may be necessary or desirable to displace
the mattress 6 to the proper elevation for transfer of the patient
to or from a transporting device. On the other hand, it may be desired
to lower the mattress 6 for the patient's feet to be able to reach
the floor or the stool 10 for instance, so that the patient can
walk away from the bed 1. Under some circumstance, it may also be
desired to be able to tilt the mattress 6 with its supporting structure
4 and 5 to a certain extent about a longitudinal axis of the bed
1 for example, to help the nurse roll the patient over or for other
similar purposes, or about the transverse axis of the bed, to change
the elevation of the patient's head relative to that of the feet.
These various movements of the mattress 6 may be the only movements
which the mattress 6 may be able to perform while supported on the
support structure 4 and/or 5 or it may be able to perform other
movements as well while so supported; so, for instance, the mattress
6 and its support structure 4 and 5 may be partitioned in various
zones in the longitudinal direction of the bed 1 and these sections
or zones may be capable of assuming different positions relative
to one another, for supporting the patient, for instance, in a comfortable
sitting position or the like. Even in this instance, however, the
mattress 6 is returnable to its basic position in which it extends
along a substantially horizontal plane.
To be able to raise and lower the mattress 6 with its support structure
4 and/or 5 there is provided a moving mechanism indicated generally
in FIG. 1 by the reference numeral 12. It will be appreciated that
this mechanism 12 may be of any of many currently known and used
constructions; yet, an exemplary construction of the mechanism 12
is indicated in the drawing. In this construction, the mechanism
12 includes an electric motor 13 which drives a distributing transmission
14 that is of a conventional construction that need not be discussed
here. The transmission 14 drives two output shafts 15 and 16 which
may be constituted by sections of a unitary shaft passing through
the transmission 14. The output shafts 15 and 16 respectively terminate
in auxiliary transmissions 17 and 18 which, in turn, drive respective
branch shafts 19 20 21 and 22 in rotation. Here again, the branch
shafts 19 and 20 and 21 and 22 may be parts of throughgoing unitary
shafts. The branch shafts 19 20 21 and 22 may carry, at their
free ends, respective gears or pinions which have not been shown
in detail in FIG. 1 in order not to unduly encumber the drawing,
since they are conventional. These pinions then may mesh with associated
racks provided on the headboard 2 and on the footboard 3 respectively.
A supply cable 23 which is shown to be equipped with a plug 24
insertible into a wall outlet or a similar electric receptacle,
serves to supply electric current to the electric motor 13 to energize
the same. The electric motor 13 is preferably of the reversible
type to cause forced movement of the frame 4 both in the raising
and lowering directions. As usual, the operation of the motor 13
may be accomplished either by plugging the plug 24 into the outlet,
or by operating a switch which, as usual, may be provided in the
supply cable 23 or at any location between the source of electric
energy and the motor 13. It will be understood that the construction
of the mechanism 12 as described above has been chosen for the purpose
of illustration alone, and that other constructions of the mechanism
12 could be used as well in the bed 1 constructed according to the
present invention, so long as they employ a motor which can be conveniently
and quickly energized and de-energized. Of course, the electric
motor 13 is particularly suited for the purposes of the present
invention and for the contemplated use; yet, other motors, such
as hydraulic or pneumatic motors could be used as well, if sources
of the respective energizing media are readily available.
Now, as mentioned before, it could happen that the mattress 6
or its supporting structure 4 and/or 5 could be interfered with
during its travel in the upward or downward direction, at only a
limited region thereof. Thus, it could occur that further movement
of this region is rendered impossible, for instance, by interference
with the nightstand 11 the stool 10 or any other objects or equipment
located close to the bed 1 while the remainder of the mattress
6 and its supporting structure 4 and/or 5 continues to move. This,
obviously, would result in tilting of the mattress 6 about either
the longitudinal axis, or the transverse axis, of the support structure
5 and/or 6 provided that the mechanism 12 permits such tilting
movement, as it usually does. The tilting about the longitudinal
axis would be the more dangerous of the two, since it could easily
and rapidly result in such a degree of tilt that the patient would
be caused to roll off the bed and fall on the floor, with attendant
danger of injury either as a result of the fall itself, or of the
disconnection of the patient from lifesupport equipment, or of the
catapulting of the patient against a raised guard rail.
To avoid this possibility, the bed 1 according to the tilt-prevention
mechanism of the present invention is provided with at least one
position-sensitive switch 25 or, as illustrated, also with an additional
position-sensitive switch 26. The switch 25 and/or the switch 26
is inserted in an electric line 27 (see particularly FIG. 2) which
connects one conductor of the cable 23 with the electric motor 13.
The switch 25 is shown to be arranged on the frame 4 so that its
longitudinal axis extends along the plane of the frame 4 and thus
the plane of the mattress 6 and transversely of the bed 1; that
is, substantially normal to the longitudinal axis of possible tilting
of the mattress 6 with its supporting structure 4 and/or 5. The
switch 26 on the other hand, extends in the longitudinal direction
of the bed 1 and, hence, normal to the other, transverse axis of
possible tilting, and also parallel to the plane of the mattress
6.
As shown in FIGS. 3 and 4 the switch 25 and, similarly, also the
switch 26 may be constructed as a mercury switch which is interposed
between two sections of the circuit line 27 and which includes an
enclosed envelope 28 partially filled with a body 29 of mercury.
So long as the section of the frame 4 on which the switch 25 or
26 is mounted extends substantially horizontally, as it does during
the normal operation of the mechanism 12 as well as when the mechanism
12 is out of operation, the upper level of the mercury body 29 assumes
the position shown in FIG. 3 in which it establishes an electric
current path between respective terminations 30 and 31 of the sections
of the line 27. This, of course, means that electric current would
be able to flow through the switches 25 and 26 and the line 27
and the electric motor 13 will be capable of being energized or,
if already energized, will continue to be energized.
On the other hand, should a portion of the mattress 6 or of its
supporting structure 4 and/or 5 be retarded or stopped in its vertical
movement, while other portions of the same continue such movement,
the respective portion of the frame 4 will be gradually tilted until
it reaches its position illustrated in FIG. 4. When this happens,
the switch 25 or 26 mounted on this portion of the frame 4 for movement
therewith will assume its position of FIG. 4 in which the mercury
body 29 is out of contact with the termination 30 (or, if the tilt
is in the opposite direction, with the termination 31). This means
that the path for the electric current flow through the switch 25
or 26 is interrupted and the electric motor 13 is de-energized or
inactivated. Hence, no further movement of the mattress 6 and its
supporting structure 4 and/or 5 can occur, and the mattress 6 will
remain in its slightly tilted position until the condition which
has caused the mattress 6 to tilt is remedied.
It may be seen that the switches 25 and 26 are arranged in series
with one another, so that the flow of electric current through the
line 27 is interrupted, regardless of whether the tilting takes
place about the longitudinal axis of the bed 1 the transverse axis
of the bed 1 or both. Of course, the shown construction of the
switches 25 and 26 as mercury switches, while currently preferred,
is exemplary only, and could be replaced by other known constructions
of position-sensitive switches, such as those working on the principle
of a pendulum, for instance.
The drawing of the present invention shows the switches 25 and
26 to be incorporated in the line 27 which connects one of the conductors
of the cable 23 with the electric motor 13. However, it is also
conceivable and contemplated by the present invention to include
the switches 25 and 26 in a separate control circuit operating at
a relatively low voltage which controls the operation of a high-voltage
switch that is interposed between the cable 23 and the electric
motor 13. This solution has the advantage that it is not necessary
to switch the usually high-wattage electric current supplied to
the motor 13 for energizing the same, so that the switches 25 and
26 can be built less robustly than otherwise. Also, it is not necessary
to take special safety precaution that would otherwise be needed
if the high-wattage electric energy were flowing through the line
27 to prevent flow of the high-voltage current into the framework
of the bed 1. This solution is particularly advantageous when a
switch operating the motor 13 and controlled by a relatively low
voltage is incorporated in the high-voltage circuit to begin with,
in that only a relatively simple and inexpensive solid-state circuitry
need be added at the control input of this switch (e.g. an AND-gate)
to achieve the operation of the mechanism 12 only when the main
control switch and the switches 25 and 26 are simultaneously closed.
It will be understood that each of the elements described above,
or two or more together, may also find a useful application in other
types of arrangements differing from the type described above.
While the invention has been illustrated and described as embodied
in a tilt-prevention mechanism and in an improved hospital bed,
it is not intended to be limited to the details shown, since various
modifications and structural changes may be made without departing
in any way from the spirit of the present invention. For example,
one or more switches of the type identified by numeral 25 may be
employed at one or more corners of the bed. Alternatively, one or
more switches of the type identified by numeral 26 may be employed
at one or more corners of the bed. The tilt-prevention mechanism
is easily installed and retro-fitted in existing adjustable beds.
Without further analysis, the foregoing will so fully reveal the
gist of the present invention that others can, by applying current
knowledge, readily adapt it for various applications without omitting
features that, from the standpoint of prior art, fairly constitute
essential characteristics of the generic and specific aspect of
my contribution to the art and, therefore, such adaptations should
and are intended to be comprehended within the meaning and range
of equivalence of the claims.
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