Note: Descriptions are shown in the official language in which they were submitted.
2 ~
~LECTRIC PLAS~ER CaST 8AW CO~ROL SYSTE~
BACKGROUND OF THE I~VENTI~N
This invention relates to a control system for
electric plaster cast sawr particulc~rly a control system to
stop electric plastic cast saw automatically and promptly
during cutting of plaster cas-t or other covering mat~rials.
Human lim~s may be fractured under a great external
force. Infant's limbs may be deformed congenitally or
acquiredly. Currently, the medical treatm~nt dealiny with
bone fracture or deformity always involves wrapping of
medical pla~ter around the lnjured area and allowing the
plaster to harden so that the limb can be healad ~uickly
without external influence.
After a certain period, the plaster cast surrounding
the injured limb mus-t be cut with an electric saw for
removal and examination. ~he limb may have to receive
other therapy or surgery if necessaLy.
In general, depth which the saw has gone into the
plaster cast is judged by visual inspection, accuracy of
which depends on operator's experience. Hence, skill is
indispensable to avoid injury to patient's muscle.
However, even sawing is carried out carefully, patent's
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skin or muscle may ba hurt accidentally, and such kind of
accident occurs frequently. Therefore, patien-t is always
afraid of such sawing, operator may hesitate to carry ou-t
the sawing/ and consequently the opera-tion is prolonged.
Accident hurt to p~tient's skin or muscle may happen due to
unexpected movement or uncontrolled shaking of limb
especially when the patient is a baby or person who has
lost the capacity to control his body.
Therefore, -there is an urgent need in the medical
field for a controller which can stop electric saw
automatically as soon as the plaster cast is cut off.
SUMMARY OF T~E INUENTIO~
The main object of the present invention is to provide
a control system for electric plaster cast saw to stop
electric saw automatîcally on the instance the plaster cast
is cut off in order to prevent from injury to patient's
skin or muscle.
Another objef-t of the present invention is to provide
a control system for electric plaster cast saw which can
effectively prevent from injury to patient's skin or
muscle, and hence the patent's fear can be eliminated,
operator's confidence for safe operation is improved, and
unnecessary dispute can be avoided.
Another object of the present invent.ion is to provide
a control sys-tem for elec-tric plaster cast saw which can
cut of power supply an~ stop electric saw automatically on
the instant the plaster cast is cut off so that cutting o~f
of plater cast can be performed by any nurse or operator
and then work burden of experienced nurse or surgeon can be
relieved.
The electric plaster cast saw control system according
to the present invention include a thin conduct:ive plate
between the plaster layer and absorbent cotton layer o~
each plastic cast with an extended end o.E the thin
conductive plate exposed outside -the plastic cast so that
it can be connected to the control system by a conductive
wire. On the instant the electric saw gets contact with
the thin conductive plats, a relay is triggered to trip
from its normal closed contact to normal open contact, and
consequently cut o~f power supply to the electric saw
instantaneously. The electric saw is hence stopped
immediately to prevent ~rom injury to patient's skin or
muscle. The control system has also a reset device to
resume power supply to the electric saw, and a warning
device to give audible or visible warning signal.
BRIEF ~ESCRIPTION OF THE DRaWI~GS
These and other objects and features of the invention
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will become more apparent from the following description
taken in connection with the accompanying drawings wherein:
Fig. 1 is a perspective view oE th~e first em~odiment
of the electric pl~ster cast saw control system according
to the present invention.
Fig. 2 is a perspective view of the second embodiment
of the electric pla~ter cas-t saw control system according
to the present invention, in which an automatic reset
device is used to replace the manual reset d~vice shown in
Fi~. 1
~ig. 3 is a sec-tional view taken along line 3-3 in
Fig. 3.
Fig. 4 is a block diagram for the first embodiment of
the present invention.
Fig. 5 is a block diagram for the second embodiment of
the present invention.
D~TAILED DESCRIPTION OF THE P~EFERRED EMB~DIMENT
Referring to Figs. 1 and 3, each plaster cast 80 to
wrap patient's fractured limb 90 has an inner layer 82
composed tearable absorbent cotton to contact with
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patient's skin, an outer layer 84 composed of a covering
material which is hardened upon contact with water,
normally plaster or resin for medical purpose, and a thin
conductive plate lO located be-tween the inner layer and th0
outer layer. The thin conduc-tive plate lO is made of
electric conductive material such as tin foil or aluminum
foil which does not affect X-ray reading or diagnosis. The
thin conductive plate 10 has an extended end 12 extended
outside the plaster cast 80. ~he extended end 12 is
designed to connect to a control system located in a power
control box 20 by means o a clamp 14 and a conductive wire
16. An electric saw 86 to cut off the outer layer 84
comprises a high speed motor (not shown iII the figures) and
a circular saw blade 8B fi~ed to a shaft 87 of the motor.
The shat is connected to the control system in the control
box 20 with a conductive wire 18 to form a control circuit.
The electxic saw 86 is connected to a socket 22 on the
control box 20 with a plug 89 for an electric power to
operate the electric saw 86. The control sys-tem in the
control box 20 is incorporated with a selector switch 24, a
warning device 26, and a reset pedal 28. The control box
20 is connected to an external power source with a plug 30.
The warning device 26 is an electric or electronic alarm to
give audible or visible warning signal. The warning device
is preferably installed on the surface of the control box
20 or the Plectric saw 86 or other appropriate location so
that it can be seen during the sawing process.
2~ 3
Please refer to Fig. 2 for the second embodiment of
the control system for plaster cast saw accordin~ to the
present invention. -ft is same with the embodiment shown in
Fig~ 1 except a reset knob 32 is used instead of the reset
pedal 28.
Please reer to Fig. 4 for a block diagram for the
first embodiment of con'rol system for plaster cast saw
according to the present invention. The control system
comprises a power supply 40, a selector switch 24, a relay
device 42, a warning device 26, and a reset device 46. The
relay device 42 i6 composed of a relay 48, a driver 50 and
a control circuit 52 to cut off power supply to the
electric saw 86 ins-tantaneously as soon as the saw blade 88
gets contact with -the thin conductive plate 10. The reset
device 46 is composed of the reset pedal 28 and a reset
circuit 54 to restart the electric saw 86. The power
supply 40 is connected to an external power source for
pro~ision of electric power to the electric saw 86
directly, or to the elec~ric saw 86 through the relay
device 42 by selection of its operator. If the selector
switch 24 is located at the first contact A, the electric
saw is started directly for continuous operation, the relay
device 42, the warning device 26 and the reset device 46 do
not function. If the selector switch 24 is located to the
second contact B, the power source is not provided to the
electric saw directly, but is connected to a common contact
C for the relay 48 which is normally closed at NC so that
the electric saw 85 can not be operated. The power source
also provides an electric power to the cont~ol circuit
52 so that the control circuit is ready to receive signal
and upon triggering of the reset device 46 by ~tepping the
reset pedal 28, which causes the reset circuit 54 to
trig~er the control circuit 52, start the driver 50 to
drive to relay 48 to trip from the normal closed contact NC
to a normal open contact NO, and consequently the power
supply 40 provides the electric saw 86 with an electric
power through the common contact C and the norma:L open
contact NO for operation o the electric saw 86. ~y this
way, the electric saw 86 can be operated to cut o~f plaster
cast. Whenever the saw blade 8B gets contact wi~h the thin
conductive plate 10 after cutting off of the outer layer
84, the saw blade 88, the thin conductive plate 10, the
warning device 26 and the control circuit 52 become a
closed loop, the warning device 26 is activated to give a
warning light or voice, the control circuit 52 cut off the
driver 50 instantaneously so that -the relay 48 trips from
the normal open contact NO to the normal closed contact NC
to cut off power supply to the electric saw 86, and
consequently, the electric saw 86 is stopped Lmmediately.
Hence, the patent's skin or muscle can be prevented form
hurting by the saw blade 88. To restart the electric saw
86, only the reset pedal 28 has to be stepped so that, as
described above, the reset circuit 54 triggers the control
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circuit 52 again to cause the driver 50 to drive the relay
48 to trip from the normal closed contact NC to the normal
open contact NO, and start the electric saw 86 again.
The relay 48 of can be of solid state or mechanically
controlled. ~he warning device shown in the figures is a
warning indicator. It can be replaced by a buz2er to
provide audible warning signal.
Please reer to Fig. 5, a block diagram for the second
embodLment of -the present invention, the plug 30 t the power
supply 40, the selector switch 24, the relay control device
42, the warning device 26, the electric saw, and the thin
conductive plate 10 are same with that used in the first
embodiment shown in Fig. 4, but an automatic reset device
56 is used instead of the reset device 46 in Fig. 4. The
automatic reset device 5S can be an adjustable pulse
generator which i5 triggered to send a pulse to the relay
device 42 on the instant that the saw blade 88 gets contact
with the thin conductive plate 10. Upon input of the
pulse, the relay 48 trips from the normal open contact NO
to the normal closed contact ~C, and consequently the power
supply to the electric saw 86 is cut off, the patent's skin
or muscle can be prevented form hurting by the saw blade
88. After elapse of a delay time caused by the pulse, the
relay 48, in the absence of pulse input, trips from the
normal closed contact NC to the normal open contact NO, and
~ ~d ,1 s 1
consequently power supply to the e:Lectric saw 86 is resumed
to continue the opera-tion. The length of the delay time
can be adjusted by a variable resistor 58. The reset kno~
32 on the control box 20 can be -turned to adjust resistance
of the variable resistor, and consequently adjust the
length of delay time.
Procedures to operate the first embodiment of the
electric plaster cast saw control ~ystem according to the
present invention are described below:
(1) Connect the control box to an external power
source with the plug 30.
15(2) Connect the electric saw 86 to the control ~ox 20
by inserting the plug 89 to the socket 22.
(3) Attach the conducti~e wlre 1~ to the extended end
12 of the thin conductive plate with -the clamp 14, and
20attach another end o~ the conductive wire 16 to the
electric saw 86.
(4) Sek the selector switch 24 -to contact B position.
25(5) Step the reset pedal 28 to start the electric saw
86. The indicator of the warning device 26 is o~ at this
inskant, which means that the control box 20 is in good
f~
working condition.
(6) Cut off -the outer layer 84 of the plaster cast 84
by the electric saw 86. The power so-lxce is cut off and
5 the electxic saw is stopped immediately, and the indicator
of the warning device 26 is on to warn khe operator not to
operate the electric saw 86 on the instant the saw blade 88
gets contact with the thin condu~tive plate 10 90 that the
patent's skin o~ muscle can be prevented form hurting by
the saw blade 88.
(7) If required, step the reset pedal 28 to resumQ
operation of the electric saw 86. The indicator of the
warning device 26 is off when the reset pedal 28 is
stepped.
(8) Repeat steps (6) and (7) till the plaster cast is
completely cut off.
~9) If opexation of the electric saw 86 without
control of the control system according to the present
invention, set the selector switch 24 at the contact A
position, then the electric saw 86 is operating continuous
and will not stop when the saw blade 8~ gets contack with
the thin conductive plate 10.
(10) It is recommendable to explain and demonstrate
the patient the whole operating process before sawing is
started.
Procedures to operate the second embodiment of the
electric plaster cas-t saw control system according to the
present invention are described bel~w:
(1) through (4) are same with that for the first
embodiment.
(5) Turn the reset knob to select the de~ired length
of delay time for interruption of the electric saw 86.
~ 6) Cut o~f the outer layer 84 of the plaster cas~ 80
by the elect~ic saw 86. The power source is cut off and
the electric s~w 86 is stoppecl Lmmediately, and the
indicator of the warning device 26 is on to warn the
operator not to operate the electric saw ~6 on the instant
the saw blade 88 gets contact with the thin concluctive
plate 10 so that the patent's skin or muscle can be
prevented form hurting by the saw blade 88.
(7) After elapse of the delay time, power supply to
the electric saw 86 is resumed, the electric saw 86 is
started again, the indicator of the warning device 26 is
off.
(8) Repeat steps (6) and (7) till the pla~ter cast is
completely cut off.
(9) If opera-tion of the electric ~aw 86 without
control of the control system according to the present
invention, set the selector switch 24 at th~ c~ntact A
position, then the electric saw 86 is operating continuous
and will not stop when the saw blade 8~ gets contact with
the thin conductive plate 10.
(10) It is recommendable to explain and demonstrate
the pakient the whole operating process ~efore sawing is
started.
While cutting off plaster cast with the control system
according to the present invention, the power supply to the
electric saw is cut of f instantaneously on the instant the
saw blade gets contact with the thin conductive plate, and
consequently, the electric saw is stopped, and the patent's
skin and muscle is preven~ed from hurt which may be caused
by the saw blade. With such an invention, the patent's
fear can be eliminated, the operator has confidence to
remove the plaster cast safely, and consequently the time
required to remove the plaster cast can be shortened.
Moreover, the with the present invention, the electric saw
can be operated by any nurse or operator, and hence work
burden of surgeon or experienced nurse can be reduced.
