Abstrict
A ratcheting device for use in tightening the cuff of a blood pressure
monitor has a lever, a lever mounting which is attached to one end
of the cuff and which holds the lever so that it can be moved in
a given direction or an opposite direction. An elastic body is disposed
between the lever and the lever mounting to transmit a force applied
to the lever into the lever mounting by elastic deformation of the
elastic body. Interdental spaces are formed between saw teeth on
the inner surface of a cam and extend in the given and opposite
directions in which the lever moves. A ratchet having pawls thereon
which can engage with the interdental spaces is provided; this rachet
is immobilized by the engagement of the pawls in the interdental
spaces when the pressure applied to the lever exceeds a given value.
Claims
What is claimed is:
1. A ratcheting device for use in tightening the cuff of a blood
pressure monitor, comprising:
a lever;
lever mounting means for mounting the lever so that the lever can
be moved in a given direction or a direction opposite the given
direction;
an elastic body disposed between the lever and the lever mounting
means so as to transmit a force applied to the lever into the lever
mounting means by elastic deformation of the elastic body;
interdental spaces between saw teeth provided on an inner surface
of a cam, the interdental spaces extending in the given and opposite
directions in which the lever moves;
a ratchet provided with pawls thereon which can engage with the
interdental spaces; and
immobilizing means for immobilizing the ratchet so that the pawls
engage in the interdental spaces when a pressure applied to the
lever exceeds a given value.
2. The ratcheting device of claim 1,
wherein the ratchet is mounted on a shaft on the lever mounting
means so that it can rotate about the shaft and engage in the interdental
spaces; and
the immobilizing means comprises guiding means for guiding the
ratchet when it rotates and engages in the interdental spaces, thus
immobilizing itself in response to the pressure in excess of a given
value being applied to the lever.
3. The ratcheting device of claim 2, wherein the lever mounting
means is adapted to receive an end of a cuff of a blood pressure
monitor.
4. The ratcheting device of claim 1, further comprising regulating
means for permitting the rachet to travel either in the given direction
or the opposite direction and for regulating the distance in the
given or opposite direction through which the rachet is permitted
to travel.
5. The ratcheting device of claim 4, wherein the lever mounting
means is adapted to receive an end of a cuff of a blood pressure
monitor.
6. The ratcheting device of claim 1, wherein the lever mounting
means is adapted to receive an end of a cuff of a blood pressure
monitor.
Description FIELD OF THE INVENTION
This invention relates to a ratcheting device which can be used
in the wrapping mechanism of a cuff on a blood pressure monitor
of the type which measures blood pressure by obstructing the flow
of blood in a finger artery.
BACKGROUND OF THE INVENTION
To facilitate the wrapping of the cuff onto the finger, prior blood
pressure monitors used on a finger employ the cuff wrapping mechanism
shown in FIGS. 12 and 13. In FIG. 12, 122 is the case, and 123 is
the cuff within the case. Rubber chamber 123b is attached to cuff
123.
The protruding end 123a of cuff 123 is fixed to lever 124. This
lever is installed on case 122 in such a way that it can slide both
in direction A, which tightens the cuff, and in direction B, which
loosens the cuff. An elastic pawl 125 is provided on lever 124.
As shown in FIG. 13, pawl 125 engages interdental spaces 126, which
are located in two parallel rows along the path of movement of lever
124. Thus, the pawl prevents the lever from moving in direction
B and loosening the cuff.
To measure a person's blood pressure, the person inserts a finger,
usually the index finger, into opening 122a in case 122. Lever 124
is then moved in direction A to tighten the cuff. During tightening,
pawl 125 is elastically deformed and passes over interdental spaces
126. When the appropriate cuff pressure has been attained, the operator
releases lever 124, and pawl 125 engages in interdental spaces 126.
This fixes the position of lever 124 and keeps cuff 123 wrapped
around the patient's finger. Air is then pumped into rubber chamber
123b until the flow of blood in the finger artery is obstructed,
and the blood pressure is measured.
When the blood pressure measurement has been completed, button
127 is pressed, causing pawl 125 to move down so that it is released
from interdental spaces 126. Lever 124 slides in direction B, allowing
cuff 123 to loosen.
With the existing cuff wrapping mechanism described above, the
operator has a tendency to apply great force to lever 124 at the
moment pawl 125 is slipping past teeth 126. This causes the pressure
with which the cuff is wrapped to vary. For this reason, the tightness
of the cuff is variable, and there is a pronounced tendency to overtighten
it.
If cuff 123 is not wrapped sufficiently tightly, the volume of
rubber chamber 123b will be increased, which will cause it to take
longer for the cuff to be pressurized. Further, the area of the
surface of rubber chamber 123b which contacts the finger will be
decreased, which increases the chance that the rubber will wrinkle.
If this happens, the blood pressure will not be measured correctly.
Problems such as these are well known in blood pressure monitors
employing the oscillation technique, in which the change in air
pressure inside rubber chamber 123b is used to detect the pulse
wave.
In contrast, if cuff 123 is wrapped too tightly, the blood in the
finger can be completely obstructed, which will cause pain to the
patient. To prevent cuff 123 from being wrapped too tightly, one
could conceivably use deeper teeth for the toothed portions of 126,
but this would cause the tightness to vary even more, and the operating
noise would become much louder.
SUMMARY OF THE INVENTION
In view of the above problems, the purpose of this invention is
to provide a ratcheting device which, when used in a blood pressure
monitor, will allow the cuff easily to be wrapped to the appropriate
tightness while minimizing operating noise.
The ratcheting device with which this invention is concerned includes
a mounting for a lever which can be moved in a given direction or
its opposite as the cuff is to be tightened or loosened. A lever
which is capable of moving in the given direction or its opposite
is installed on the mounting. An elastic body is situated between
this lever and its mounting which can transmit the force applied
to the lever into the lever mounting by elastic deformation. There
is a ratchet with pawls and interdental spaces provided along the
two directions in which the lever moves into which the pawls can
fall. Finally, there is a means for immobilizing the ratchet, so
that the pawls engage in the interdental spaces when the pressure
applied to the lever exceeds a given value. With this design, the
lever mounting can move smoothly until the pawls of the ratchet
engage in the interdental spaces, thus minimizing the operating
noise of the lever mounting.
In operation, the lever mounting runs into a stop, and the elastic
body is compressed. When the compressive force exceeds a given value,
the means for immobilizing the lever cause the pawls to engage in
the interdental spaces. The lever mounting can move no further in
the given direction, even if additional force is applied in that
direction. Thus, it is impossible to apply excessive force to the
person's finger.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1(a) is a cross sectional view of the cuff tightening unit
of an embodiment of this invention, shown with the cuff loosened.
FIG. 1(b) shows the cuff tightening unit of FIG. 1(a), illustrating
the relationship between the ratchet and cam when the cuff is loosened.
FIG. 2(a) cross sectional view of the cuff tightening unit of FIG.
1(a), shown with the cuff tightened.
FIG. 2(b) shows the cuff tightening unit of FIG. 1(a), illustrating
the relationship between the ratchet and cam when the cuff is tightened.
FIG. 3(a) is a cross sectional view of the cuff tightening unit
of FIG. 1(a) when the tightening of the cuff has been completed.
FIG. 3(b) shows the cuff tightening unit of FIG. 1(a), illustrating
the relationship between the ratchet and cam when the tightening
of the cuff has been completed.
FIG. 4 is an enlarged view of the cross section taken along line
IV--IV in FIG. 1(a).
FIG. 5 is an oblique exploded view of the disassembled parts of
the cuff tightening unit of FIG. 1(a).
FIG. 6 is a frontal view of the exterior of the finger cuff-type
electronic blood pressure monitor in which a cuff tightening unit
of the type depicted in FIG. 1(a) is installed.
FIGS. 7(a) and (b) show, respectively, a cross sectional view of
the cuff wrapping mechanism for the blood pressure monitor relating
to a second embodiment of this invention, and a view of the mechanism
of FIG. 7(a) as seen from the inside of the case.
FIGS. 8(a) and (b) show respectively a cross sectional view of
the cuff wrapping mechanism used in the blood pressure monitor of
FIG. 7(a), with the cuff tightened, and the view as seen from the
inside of the case.
FIG. 9 is an enlarged view of the cross section taken along line
III--III in FIG. 7(a).
FIG. 10 shows an oblique exploded view of the disassembled parts
of the cuff winding mechanism used in the blood pressure monitor
of FIG. 7(a).
FIG. 11 is a frontal view of the finger cuff-type electronic blood
pressure monitor in which the cuff winding mechanism of FIG. 7(a)
is employed.
FIG. 12 shows a cross sectional view of a cuff winding mechanism
used in existing blood pressure monitors.
FIG. 13 illustrates the interdental spaces and pawls in the cuff
winding mechanism depicted in FIG. 12.
DETAILED DESCRIPTION OF THE INVENTION
We shall now explain an embodiment of this invention with reference
to FIGS. 1 through 6, starting with a summary of how the invention
works in this embodiment.
In FIG. 6, finger-cuff electronic blood pressure monitor 1 has
a liquid crystal display 3, which displays blood pressure values
and other information, and operating buttons 4 and 5 are located
on case 2, which encloses blood pressure monitor 1. The cuff tightening
unit 10, as depicted in FIGS. 1(a) and (b), FIG. 4 and FIG. 5, is
attached to case 2. A finger can be inserted into part 2a. Slot
2b, in which the lever slides, is also provided.
FIG. 1(a) is a cross sectional view of cuff tightening unit 10
when the cuff is loose. FIG. 1(b) illustrates the relationship between
cam 15 and ratchet 48 by showing an overhead view of cuff tightening
unit 10 with cover 19 removed. FIGS. 2(b) and 3(b) show the same
view. FIG. 4 shows an enlarged cross section along the area in FIG.
1(a) indicated by line IV--IV. FIG. 5 shows an oblique exploded
view of the disassembled components of cuff-tightening unit 10.
With its housing 10a removed, cuff-tightening unit 10 includes base
11 and cover 19, cam 15, lever mounting 23, lever 33, stop 42, ratchet
48 and coil springs 18, 32 and 37 as its major components. For the
sake of convenience and simplicity, the unit is broken down vertically
in the following explanation.
The ratcheting device of this invention includes a mounting 23
for a lever which can be moved in a given direction (A) or its opposite
(B). A lever 33, capable of moving in either direction (A) or (B),
is installed on mounting 23. An elastic body 32 is situated between
lever 33 and its mounting 23 which can transmit the force applied
to the lever into the lever mounting by elastically deforming. A
ratchet 48 is provided with pawls 49 which can fall into interdental
spaces 17 provided along the two directions (A) and (B) in which
the lever moves. The means for immobilizing the ratchet is depicted
by reference numerals 45, 50; this means causes the pawls 49 to
engage in the interdental spaces 17 when the pressure applied to
the lever 33 exceeds a given value.
In this embodiment of the invention, when the lever 33 is moved
in direction (A), the force is transmitted through the elastic body
32 to the lever mounting 23, which also moves in direction (A).
When the lever has reached a certain point, the lever mounting 23
is stopped, and the elastic body 32 is compressed. When the compressive
force exceeds a given value, the means for immobilizing the lever
45, 50 causes the pawls 49 to engage in the interdental spaces 17,
thus securing the ratchet. As a result, the lever mounting 23 is
locked into its position and can move no further in direction (A),
even if more force is applied to the lever. Therefore it is not
possible to apply an excessive force to the finger disposed in the
cuff because of this arrangement. When this ratcheting device is
employed in a blood pressure monitor, it prevents overtightening
of the cuff. Also, because the lever mounting moves smoothly until
the pawls of the ratchet engage in the interdental spaces, operating
noise is kept to a minimum.
Base 11 as shown in FIG. 5 includes cylindrical cuff sleeve 12
and cam sleeve 13, which form a single unit. Inside cam sleeve 13
is U-shaped cam 15. This cam is constructed in such a way that it
can slide a certain distance within cam sleeve 13 in either direction
(A), which tightens the cuff, or direction (B), which loosens the
cuff. Guide rails 14 are provided on the inner surface of cam sleeve
13. As shown in FIG. 4, these guide rails 14 contact corresponding
ridges 16 on the underside of cam 15 in order to guide it so that
it can move smoothly.
The inside of cam 15 has parallel rows of sawteeth defining interdental
spaces 17. One end of the cam, 15a, is slightly shorter than the
other end, 15b. Coil spring 18 is interposed between cam end 15a
and vertical wall 13a of the cam sleeve so that it can absorb the
force when cam 15 slides in direction (A) to tighten the cuff. Cam
sleeve 13 is enclosed by cover 19, and is constructed in such a
way that cam 15 and coil spring 18 cannot slip out of the sleeve.
As shown in FIGS. 4 and 5, cover 19 is fastened to the cam sleeve
by tabs 20, which engage on the bottom of cam sleeve 13 to secure
the cover. Cover 19 has a long slot in it, slot 21, into which tabs
22 are inserted.
Lever mounting 23 is seated on tabs 22. The end 24 of lever mounting
23 protrudes downward between tabs 22. This end 24 has projections
25 on either side to prevent it from coming out of the tabs, and
it also has an anchor pin, 26. This pin is anchored to the protruding
end 9 of the cuff, which extends out of cuff cover 12. Lever 33
is mounted on lever mounting 23 in such a way that it can slide
in direction (A) to tighten the cuff or in direction (B) to loosen
the cuff. Tabs 34 on lever 33 are engaged, respectively, in slots
27 on lever mounting 23. These tabs serve to guide lever 33 in directions
(A) and (B).
Pin 35 depends vertically from lever 33, passes through guide track
28 on lever mounting 23, and protrudes downward, as shown in FIG.
1(a). Coil spring 32 is interposed between spring pressure plate
31 on lever mounting 23 and the base of pin 35.
Button 38 is mounted on lever mounting 23. Button shaft 40 protrudes
downward through hole 30 in lever mounting 23. Lever 33 has an opening
36 in it so that the head 39 of button 38 will not contact it. Coil
spring 37 is attached to button shaft 40 and provides force in an
upward direction.
As shown in FIGS. 1(a), 4 and 5, stop 42 is mounted to the bottom
surface of lever mounting 23 in such a way that it, too, can slide
in directions A and B. On the top surface of stop 42 there are two
guide teeth 43, which fit into guide track 28 on lever mounting
23. These teeth engage, respectively, with guide rails 29. The lower
end of the pin 35 inserts into hole 44 on stop 42 so that lever
33 and stop 42 move as a single unit.
Slot 45 is cut in stop 42 on a diagonal with respect to directions
(A) and (B). Depression 45a is on the side toward direction (B),
which loosens the cuff. It is cut one step deeper than the rest
of the slot. Button shaft 40 goes through slot 46, which allows
it to protrude downward. Ratchet 48 is mounted to this protruding
shaft 40 in such a way that it is free to rotate. Detent 41 prevents
ratchet 48 from coming loose. Ratchet 48 has two pawls 49 and two
projections 50, 51 on its upper surface. Projection 50 fits into
slot 45 as a guide. When the cuff is loosened, it is on the side
of the slot closer to direction (A). The other projection, 51, contacts
the bottom of stop 42 when the cuff is loosened. These projections
are provided in order to insure that ratchet 48 can rotate smoothly.
The following is an explanation of the cuff tightening operation
in the embodiment with reference to FIGS. 2 and 3. When force is
applied to lever 33 in direction (A), which tightens the cuff, this
force is transmitted to lever mounting 23 through coil spring 32,
and lever mounting 23 begins to slide in direction (A). The protruding
end 9 of the cuff is pulled in direction (A), and the cuff is tightened
around the finger.
When the cuff is tightened, coil spring 32 is deformed by compression,
and lever 33 and stop 42 slide against lever mounting 23 in direction
(A). At this time the center of rotation of ratchet 48, i.e., button
shaft 40, is anchored to the top surface of lever mounting 23, so
projection 50 is guided by slot 45, and ratchet 48 rotates in direction
(C).
When the value for the cuff tightening force is exceeded, pawls
49 on ratchet 48 engage in interdental spaces 17 can be seen in
FIGS. 2(a) and (b). At the same time, projection 50 is pulled into
depression 45a, projection 51 is pulled into slot 46, and ratchet
48 is secured by stop 42. When pawls 49 engage interdental spaces
17, lever mounting 23 is immobilized with respect to cam 15, and
the cuff cannot be tightened any further.
When the operator's hand is removed from lever 33, air begins to
enter the rubber chamber on the cuff, and cam 15 slides distance
b in direction (B), the direction which loosens the cuff, while
lever mounting 23 remains immobilized. This can be seen in FIGS.
3(a) and (b). This causes the cuff to loosen very slightly so the
value for the tightening force of the cuff at the start of pressurization
can be fixed at close to zero, and a correct blood pressure reading
can be obtained. This distance b can be adjusted by varying the
elasticity of coil spring 1B. Thus the movement of cam 15 can be
controlled such that the cam does not move in direction (B) farther
than is necessary.
To loosen the cuff, the operator pushes button head 39. When this
button head is pushed, ratchet 48 moves downward, projections 50
and 51 are released from depression 45a and slot 46 respectively,
and ratchet 48 becomes free to rotate. The force of coil spring
32 causes lever 33 and stop 42 to resume their former positions
with respect to lever mounting 23. Ratchet 48 rotates in the direction
opposite C, and pawls 49 disengage from interdental spaces 17. Lever
mounting 23 can then slide in direction (B), and the cuff can be
loosened. The force of coil spring 18 causes cam 15 to resume its
former position.
In the embodiment described above, coil spring 18 is used to control
the travel of cam 15. This structure acts to regulate rachet travel
by permitting the rachet to travel either in direction (A) or in
direction (B) while regulating the distance in either direction
through which the rachet is permitted to travel. However, the invention
is not limited to the use of such a coil spring. Any appropriate
design modification can be made.
Another embodiment of this invention is explained below with reference
to FIGS. 7 through 11. FIG. 11 is a frontal view of finger cuff-type
electronic blood pressure monitor 101, in which the ratcheting device
of this second embodiment is employed. The end of case 102 of this
blood pressure monitor is formed into finger insertion unit 102a,
within which a cuff with an air chamber [not pictured] identical
to those of previous versions is provided. Case 102 has a slot 102b
on it, in which the wrapping device for the cuff is located.
The wrapping device for the cuff, as shown in FIG. 10, includes
button 110, lever 108, coil springs 109 and 111, lever mounting
107, cover 104, cam 105, stop 112 and ratchet 113. Cover 104 is
fastened to the inner surface of case 102 and projects from slot
102b as shown in FIGS. 7, 9 and 11. Cam 105 is inside case 102,
and is attached to the inner surface of cover 104. Cam 105 has sawteeth
on either side of slot 102b extending along its length. The sawteeth
are positioned beneath cover 104 but do not come in contact with
it.
Lever mounting 107 is retained in slot 102b on the exterior of
case 102. It can slide on cover 104 in either direction (A), which
tightens the cuff, or direction (B), which loosens the cuff. The
end portion 107a of lever mounting 107 depends within the case between
the two portions of cover 104. Projections 107b prevent the lever
mounting from coming loose. Anchor pin 107c depends from the end
107a of the lever mounting and secures the protruding end 103 of
the cuff as shown in FIGS. 7(a) and 10. Lever 108 is mounted on
lever mounting 107 in such a way that it can slide on the mounting
in direction (A), which tightens the cuff, or in direction (B),
which loosens the cuff. Tabs 108a on lever 108 engage in respective
slots 107d on lever mounting 107. They serve to guide lever 108
in directions (A) and (B). Pin 108b depends from lever 108, passes
through guide slot 107e on lever mounting 107, and protrudes downward.
Coil spring 109 is interposed between lug 107h and the lower end
of pin 108.
Button 110 is mounted on lever mounting 107. The shaft of this
button, 110b, passes through hole 107g on lever mounting 107 and
protrudes downward. Lever 108 has an opening 108c on it, so that
the top 110b of the button Will not contact the lever. Coil spring
111 is attached to button shaft 110b. It provides a force to move
button 110 upward.
Stop 112 is mounted to the bottom surface of lever 107 in such
a way that it allows the lever to slide in directions (A) and (B)
against the lever mounting. Stop 112 has two tabs 112a on it. These
tabs insert into guide slot 107e on the lever mounting and engage,
respectively, with projections 107f. The lower end of pin 108b inserts
into hole 112b so that lever 108 and stop 112 can move as a single
unit against lever mounting 107.
Stop 112 has a slot 112c on it, which is oblique with reference
to directions (A) and (B). On the side of this slot closer to direction
(B), which loosens the cuff, there is a depression, 112d, which
is one step deep. Hole 112e is for button shaft 110b. The button
shaft passes through the hole and protrudes into the interior of
the device. Ratchet 113 is mounted to this protruding button shaft
110b in such a way that it is free to rotate. Ratchet 113 has two
pawls 113a and a projection 113b, which is higher than the rest
of the ratchet. This projection 113b is guided by slot 112c. When
no force is being applied to tighten the cuff, the projection will
be on the end of slot 112c in the direction of direction (A).
We shall next explain the operation of the cuff wrapping mechanism
in this second embodiment, with reference to FIGS. 8(a) and (b).
When force is applied to lever 108 in direction (A), which tightens
the cuff, this force is transmitted to lever mounting 107 through
coil spring 109, and lever mounting 107 begins to slide in direction
(A). The protruding end 103 of the cuff is pulled in direction (A),
and the cuff is wrapped around the finger.
When the cuff is wrapped around the finger, coil spring 109 is
compressively deformed, and lever 108 and stop 112 slide against
lever mounting 107 in direction (A), which tightens the cuff. Because
the center of rotation of rachet 113 is fixed to lever mounting
107, projection 113b is guided by slot 112c, and ratchet 113 rotates
in direction C.
When the tightening force exceeds a given value, pawls 113a on
ratchet 113 engage respective interdental spaces 106. At the same
time, projection 113b engages in slot 112c, and ratchet 113 is fixed
in that position. When pawls 113a engage interdental spaces 106,
lever mounting 107 is arrested in its position at that moment, and
the cuff cannot be tightened or loosened any further. Because pawls
113a and interdental spaces 106 do not come in contact until lever
mounting 107 is arrested, the force used to tighten the cuff is
not variable as in former designs. As a result, there is less chance
of overtightening the cuff, and operating noise is kept to a minimum.
When the measurement of blood pressure has been completed, the
operator pushes button head 110b, and the entire ratchet 113 is
moved downward toward the interior of the device. When ratchet 113
moves downward, projection 113b disengages from slot 112c, and the
ratchet becomes free to rotate in the opposing direction. Consequently,
pawls 113a disengage from interdental spaces 106, and lever mounting
107 moves in direction (B), enabling the cuff to be loosened.
Although the invention has been described with respect to two embodiments
depicted in this application, persons skilled in this art will readily
recognize and be able to practice other equivalent embodiments of
the invention upon consideration of the specification, claims and
drawings of this application. |