U.S. patent number 3,561,330 [Application Number 04/872,456] was granted by the patent office on 1971-02-09 for fluid operable motor.
This patent grant is currently assigned to Alfred H. Rosen, Leonard L. Krasnow, Stanley R. Rich. Invention is credited to Stanley R. Rich.
United States Patent |
3,561,330 |
Rich |
February 9, 1971 |
**Please see images for:
( Certificate of Correction ) ** |
FLUID OPERABLE MOTOR
Abstract
A fluid operable motor element made of a tube of elastic
deformable material (e.g. rubber) closed at one end. The tube is
restrained against deformation transverse to its longitudinal axis,
and against longitudinal deformation in a limited region of its
side walls. The remainder of the sidewalls is free to execute
elastic deformation in the longitudinal direction. When fluid
pressure in the tube is changed to a pressure different from the
ambient pressure, the tube flexes about the
longitudinally-restrained region of its sidewalls. Methods of
making the motor element, several forms of it, and combinations of
such motor elements with other devices and with other motor
elements to form a pressure gauge, a clamping device, pliers,
wrenches, a self-wrapping hook, and an artificial human hand, are
described.
Inventors: |
Rich; Stanley R. (Worcester,
MA) |
Assignee: |
Stanley R. Rich (Worchester,
MA)
Alfred H. Rosen (Newton, MA)
Leonard L. Krasnow (Worchester, MA)
|
Family
ID: |
25359606 |
Appl.
No.: |
04/872,456 |
Filed: |
November 24, 1969 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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622183 |
Mar 10, 1967 |
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Current U.S.
Class: |
92/92; 294/119.3;
73/741 |
Current CPC
Class: |
F15B
15/103 (20130101); B25B 5/061 (20130101); B25B
5/065 (20130101); B25J 15/0023 (20130101); B25B
13/52 (20130101) |
Current International
Class: |
B25J
15/00 (20060101); B25B 13/52 (20060101); B25B
13/00 (20060101); F15B 15/00 (20060101); B25B
5/06 (20060101); B25B 5/00 (20060101); F15B
15/10 (20060101); F01b 019/04 () |
Field of
Search: |
;73/418,410,409,388
;92/91,92 ;3/1.2,12.7 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Woodiel; Donald O.
Parent Case Text
This application is a streamlined continuation of the copending
application Ser. No. 622,183, filed Mar. 10, 1967, now abandoned.
Claims
I claim:
1. An elongated tubular body comprising a structure which is
limited against circumferential extension substantially uniformly
throughout its length, a longitudinal section of said structure
being limited against extension in the longitudinal direction, the
remainder of said structure being reversibly extensible in said
longitudinal direction, whereby inflation of said structure with a
fluid will cause said structure to flex.
2. An elongated tubular body comprising a flexible structure, means
for limiting said structure against circumferential extension
substantially uniformly throughout its length, means for limiting a
longitudinal section of said structure against extension in the
longitudinal direction, the remainder of said structure being
reversibly extensible in the longitudinal direction, whereby
inflation of said structure with a fluid will cause said structure
to flex.
3. A tubular body according to claim 2 in which said means for
limiting against circumferential extension comprises elongated
substantially nonextensible material oriented transversely to said
longitudinal direction in restraining relation with the walls of
said body.
4. A tubular body according to claim 3 in which said limiting means
is a continuous helix of said elongated material.
5. A tubular body according to claim 2 in which said means for
limiting said longitudinal section against extension comprises
flexible but substantially nonextensible material oriented in said
longitudinal direction in restraining relation with said
longitudinal section.
6. A tubular body according to claim 2 in which said structure is a
tube of flexible elastic material, and said limiting means are
cordlike members of substantial nonextensible material.
7. A tubular body according to claim 1, a wall of which varies in
thickness along said longitudinal direction, whereby inflation of
said structure with a fluid will cause said structure to flex
nonuniformly along said direction.
Description
BACKGROUND OF THE INVENTION
This invention relates in general to a new form of motor element
having the property that it flexes and can exert a force in
response to an applied fluid force, and to combinations of such
motor elements to provide grasping tools and manipulative and
prosthetic devices.
Many classes of tools, grasping devices and manipulative and other
devices are known which make use of motor or force-exerting
elements which pivot or execute a quasiflexural motion to
accomplish their purposes. Some devices such as pliers, some
wrenches and clamps (both hand operated and powered) use levers;
chain wrenches are another type of device which may be said to
encircle the workpiece. Manipulative devices range from small part
clamping and assembling devices to remote handling components and
systems for radioactive and corrosive materials, and materials at
high temperatures. Prosthetic devices, some including manipulative
components, frankly seek to duplicate the flexural mode of
operation of fingers and other jointed members of the body. To my
knowledge, except for rather simple devices of limited application,
as in a Bourdon pressure gauge, only levers and links, and
combinations of the same, together with cables, pulleys and
supporting members supplied with pivots, have heretofore been
available for these purposes. Such structures and combinations of
them become unwieldy, complex and costly in all but the simplest
applications and when the source of applied force is remote from
the location at which the result of that force is sought to be
used. The present invention is addressed to an entirely new
approach which removes the need for levers, links, pivots, pulleys,
cables and the like in the foregoing and similar applications.
DESCRIPTION OF THE INVENTION
It is a principal object of the invention to provide a
fluid-operable motor element capable of executing a flexural motion
in response to an applied fluid force, and methods of making such
motor elements. Another important object is to provide such a motor
element which can exert force while executing flexural motion, and
thereby be used to do work, and to manipulate heavy objects.
A further object of the invention is to provide combinations of
such motor elements with other elements, including but not limited
to other similar motor elements, for the purpose of making tools
such as pliers and wrenches, clamping devices, grasping devices,
both hand and power operated, manipulative devices, prosthetic
devices, self-actuating hooks, and wrapping devices, as
examples.
A more specific object of the invention is to provide an artificial
human hand which closely duplicates a human hand in both function
and appearance, and which is simple in construction yet capable of
executing complex movements.
Another specific object of the invention is to provide pliers,
wrenches, clamping and manipulative devices and the like which can
conform themselves to the contour of an article being handled.
According to the general object of the invention there is provided
a fluid-operable motor element comprising a hollow member of
substantially tubular form having sidewalls surrounding a chamber
extending on an axis located between said sidewalls, restraining
means connected to a portion of said sidewalls for substantially
preventing a change in dimension of said portion parallel to said
axis, at least a portion of the remainder of said sidewalls in the
same transverse region of said member as said restraining means
being capable of and free to execute elastic deformation parallel
to said axis. The restraining means may, for example, be an
elongated flexible but longitudinally substantially inextensible
member associated with the wall of the hollow member and extending
in the axial direction. When fluid under pressure is admitted to
and confined in the chamber of such a motor element, the motor
element executes a flexural motion about the restraining means due
to elastic deformation parallel to the tube axis of the sidewalls
of the hollow member remote from the restraining means. When the
fluid is released from the chamber, the motor element returns to
its relaxed posture. Only the strength of the materials used, and
the pressure applied to the operating fluid, limit the force that
can be applied by the motor element, or the work that can be done
by it.
I have found, moreover, that when the fluid pressure in the chamber
is reduced below the ambient (e.g: atmospheric) pressure, the motor
element executed a flexural motion opposite in direction to that
executed when the fluid pressure in the chamber is increased above
the ambient pressure. Thus, it will be convenient in the
specification and the claims to refer to " absolute pressure."
Since the construction, materials, modes of use, methods of
manufacture, and applications of new motor elements of the
invention, singly or in combination with other similar motor
elements, or with other devices or different motor elements, will
be limited only by the imagination of the reader, it would be
futile to attempt to mention all that are possible. The following
description of certain embodiments of the invention, and of several
methods to make it, and to apply it singly and in combinations,
will suggest more, and will disclose additional objects and
features of the invention. Obviously, it is intended that this
description shall be taken as illustrative of the invention, and
not in a limiting sense, and that, having regard to the fact that
the invention opens new areas of development in the art or arts to
which it relates, the claims that follow the description are to be
given the broadest possible interpretation of which they are
susceptible under the law.
This description refers to the accompanying drawings, in which:
FIG. 1 (A--D) shows a method of making a motor element according to
the invention;
FIG. 2 (A,B) shows another method of making the motor element;
FIG. 3 (A,B) shows another method of making the motor element;
FIG. 4 (A--C) illustrates a mode of operation of motor elements
according to the invention;
FIG. 5 illustrates another embodiment of the invention;
FIG. 6 illustrates still another embodiment of the invention;
FIG. 7 and 7A illustrate a prosthetic device according to the
invention;
FIGS. 8 and 8A illustrate a manipulative device according to the
invention;
FIG. 8B illustrates a modification of the device of FIG. 8;
FIG. 9 illustrates another manipulative device according to the
invention;
FIG. 10 shows another embodiment of the motor element according to
the invention;
FIG. 11 shows an alternative structure according to the concept of
FIG. 10;
FIG. 12 shows a modification applicable in general to motor
elements of the invention;
FIG. 13 illustrates a modification of the device of FIG. 8
according to FIG. 12; and
FIG. 14 illustrates a pressure gauge incorporating a motor element
according to the invention as the sole movable element thereof.
FIG. 1 illustrates a method of making a motor element 15 according
to the invention. Starting with a tube 10 of hand wrapped india or
gum rubber, shown in side view in FIG. 1A, a longitudinal restraint
member 11, such as a piece of nylon or cotton cord, is attached to
the tube along its outer side, running in the axial direction. The
restraint member has the property that it is flexible but, compared
to the tube 10, substantially nonextensible; it is attached by a
rubber cement, or other suitable adhesive to the tube 10. A rubber
cement available as "Pliobond" (Trademark) from the Goodyear Rubber
Co., is suitable. Next as shown in FIG. 1B, a split mandrel 12, 13
is fitted into the tube 10 and the parts pushed together to fit it
snugly in the tube. Then a cord 14, such as nylon or cotton cord,
is helically wrapped tightly around the tube 10 and longitudinal
restraint member 11, as shown schematically in FIG. 1C, until the
tube 10 is substantially entirely wrapped helically. This helical
winding 14 may then also be bonded to the tube 10, like the
restraint member 11. As shown in FIG. 1D, the mandrel 12, 13 is
removed by pulling its parts away from each other. This is
facilitated by lubricating the mandrel parts 12 and 13 with talcum
powder, for example, before they are put in the tube (FIG. 1B).
The resulting motor element 15 is capable of longitudinal
elongation except where restrained by the longitudinal restraint
member 11. The helically-wrapped cord 14 provides restraint against
radial expansion of the tube 10, while permitting its longitudinal
expansion. It is therefore obvious that the motor element of the
invention is distinguished from the Bourdon tube and similar
devices in both form and function. As is well known a Bourdon tube
is flattened in cross section in the relaxed state, and tends to
distend or deform transverse to its longitudinal axis when under
pressure, thereby producing a straightening effect. There is no
differential elastic deformation of its walls parallel to its
longitudinal axis. In the present invention, moreover, radial
distortion is restrained, and does not enter into the motor
function.
A motor element 15 may also be made as shown in FIG. 2, where FIG.
2A shows a rectangular sheet 20 of india or gum rubber, to one side
of which the longitudinal restraint member 11 has been attached as
by rubber cement. Crossing the rubber sheet, on the same side, and
passing over the longitudinal restraint member, are a plurality of
pieces of cord 14' closely placed and fastened as by rubber cement
or other suitable adhesive to the rubber sheet 20. One edge 23 of
the sheet, parallel to the transverse cord pieces 14', is shown
crosshatched, so that it can be found in FIG. 2B. After being so
prepared, the sheet 20 is wrapped into a tube, as shown in FIG. 2B,
with the transverse cord pieces 14' on the outside and the
longitudinal restraint member 11 embedded in the wall of the tube
and extending essentially parallel to the axis of the tube. This
procedure provides a motor element similar to that made according
to FIG. 1, and may lend itself more easily to mass production. It
will be seen that pieces of sheet rubber 20 with cord pieces 11 and
14' attached can be cut from larger sheets to which longer cords
have been previously attached in an appropriate array, and then
wrapped into tubes as in FIG. 2B.
FIG. 3 shows another method of producing a motor element 15, which
uses part of the process of FIG. 2 and part of the process of FIG.
1. A sheet 30 of suitable rubber is fitted with the longitudinal
restraint member 11, as shown in FIG. 3A, and then rolled into a
tube as shown in FIG. 3B, with the longitudinal restraint member in
the desired place, which may be embedded in the wall of the tube,
and extending in the axial direction. These steps provide the part
shown in FIG. 1A, which is then processed as described above in
connection with FIGS. 1B--D, inclusive. It will be understood that
further layers or plies of rubber and/or restraint elements may be
added, if desired, to motor elements produced by the foregoing
methods.
The fundamental mode of operation of a motor element 15 is
illustrated in FIG. 4. One end of the tube is stopped with a plug
41. The other end is fitted over an input pipe 42. Control
mechanism, shown in reduced scale compared to the motor element 15,
comprises a reservoir 43 for a liquid, a pump P for providing a
source of fluid under pressure, represented by a box 44 to which
the pump is connected via a one-way valve, a stopcock 45 in a riser
46 from the source 44, and a two-way (three-port) valve 47
connected between the stopcock and the input pipe 42. A pipe 48
connects from the two-way valve to the reservoir input 49, to carry
exhaust fluid back to the reservoir. A suitable fluid for operating
the motor element 15 is water, oil, or other liquid. A compressed
gas may also be used, but FIG. 4 is drawn to illustrate operation
with a liquid under pressure in excess of ambient.
As the valves 45 and 46 are set in FIG. 4A, the fluid under excess
pressure is not permitted to enter the motor element 15, and it
remains relaxed, and undistorted, as shown. When however the
stopcock 45 is turned to pass fluid under excess pressure from the
source 44 through the three-port valve 47 into the motor element
15, the motor element flexes about the longitudinal restraint
member 11, as shown in FIG. 4B. Assuming the length of the motor
element 15 to be l in the relaxed, or unflexed, state, the outer
surface of it furthest removed from the longitudinal restraint
member 11 stretches, or elongates, a distance = .DELTA. l, and
assumes the length l + .DELTA. l. Under the condition that the
motor element 15 has elastic properties that are uniform along its
length l, when it is made by fluid pressure to flex from a straight
to a curved posture, as shown in FIG. 4B, the longitudinal
restraint member 11 describes the arc of a circle, so that l =
R.alpha., where R is the radius of the circle; and .alpha. is the
angle of the arc.
Similarly:
l+.DELTA.l = .alpha. (R+d) where d is the diameter of the motor
element 15.
Where .alpha. = 1 radian:
l+.DELTA.l = R+d
l = R
and .DELTA.l = d.
This relationship enables the computation of the amount of fluid
that must be added to a given motor element that is full but
undeflected in order to achieve a known deflection that will
provide an angle .alpha. = 1 radian.
In the deflected state under excess pressure the motor element is
restrained from radial expansion by the circumferentially-wrapped
cords 14, 14'. The tubular structure can change its longitudinal
dimension, parallel to its axis, everywhere except where restrained
by the longitudinal restraint member 11. When the fluid under
excess pressure is released from the motor element it returns to
its relaxed state, due to the elasticity of the underlying tubular
member (10 in FIG. 1, for example), as is shown in FIG. 4C. The
stopcock 45 is closed, and the three-port valve 47 is turned to
pass fluid from the interior of the motor element 15 to the exhaust
conduit 48. Exhaust fluid may be discarded, or returned to the
reservoir 43, as desired.
As is noted pressure," the motor element 15 can flex in the
direction opposite to that shown in FIG. 4B if the fluid in it is
brought to a pressure below the ambient (e.g.: atmospheric)
pressure. Thus, if one thinks of the applied pressure as an
"absolute pressure," which can be less than or greater than the
ambient pressure, it will be understood that the motor element 15
can be made to flex in the direction shown in FIG. 4B, or in the
opposite direction, as desired.
In FIGS. 4B and 4C the motor element 15 is illustrated, for
convenience, simply as a tubular structure having a longitudinal
restraint member 11 on it, the radial restraint member(s) 14 or 14'
being omitted but understood to be present. Also, for simplicity, a
motor element may be illustrated simply as a tubular structure
without showing a stopper for one end or a fluid input for the
other, since it is easily understood that such parts will be
present in practice. This convention serves to illustrate the basic
structure of a motor element, and will be followed in illustrating
other embodiments of the invention. Thus, in FIG. 5 there is shown
a motor element 55 in tubular form having a restraint member 51
attached to the outer surface of its wall, which extends from one
end to the other of the tubular member but in a direction having
components both longitudinal and circumferential. When caused to
flex, this motor element will tend to take the form of a helix,
illustrated in FIG. 9, and if it is long enough will assume the
shape of a prehensile tail.
FIG. 6 illustrates the basic structure of another motor element 65,
made of a tubular member 60 having short sections of
longitudinal-restraint members 61, 62, etc. on its outer wall,
displaced circumferentially one from another. A motor element made
this way will, when caused to flex, execute a compound motion, one
transverse region 62.5 flexing about its restraint member 62, while
the adjacent transverse region 61.5 flexes in a different direction
about its restraint member 61.
Motor elements of the invention can be made in any desired shape in
the relaxed condition, and can be made to assume another desired
shape in the energized condition. Thus, while the embodiments
illustrated generally show motor elements which are straight when
relaxed and flexed into a curved shape when energized, it will be
understood that a motor element can be curved in the relaxed state
and straight in the energized state, or can be curved in the
relaxed state and further curved in the energized state. In any
case, it is characteristic of motor elements of the invention to
flex with an attendant change of shape when energized.
Motor elements of the invention can be combined to cooperated for
various manipulative purposes. FIG. 7 shows such a combination to
provide an artificial human hand, which can be used as a prosthetic
device. A manifold 70 has an input port 71 for operating fluid, and
five output ports 72 for a thumb and 73, 74, 75 and 76 for index,
middle, ring and little fingers, respectively. Attached to the
thumb port 72 is a thumb motor element 152 which has its remote end
or tip 152.1 closed and in the general shape of a finger tip. This
motor element is bent in the relaxed state at a joint region 152.2
corresponding to the large joint in a human thumb.
A first portion 151.3, nearer to the thumb port 72, is essentially
straight in the relaxed state, and has a restraint member 112.3. A
second portion 151.4 between the joint region and the tip has a
second restraint member 112.4, and is slightly curved in a convex
shape to resemble the ball portion of a human thumb. The thumb
motor element 152 can be rotated about the thumb port 72 so that
when it is energized its motion will closely approximate that of a
human thumb.
An index finger motor element 153 is connected to the index finger
port 73. As seen in FIG. 7A, this motor element can be made with a
thicker wall near the root on the palm side of the hand than at the
tip or back side, so that when energized its flexure about the
restraint member 113 will be nonuniform in a desired pattern. The
tip 153.1 is closed and rounded to resemble a finger tip. The
remaining fingers 154, 155 and 156 have similarly disposed and
oriented restraint members 114, 115 and 116, respectively, so that
when energized all the fingers will flex together, as in a human
hand.
The entire structure of FIG. 7 can be enclosed in a suitable sheath
77, indicated partially enclosing the structure by a dashed line in
FIG. 7, to make it look like a human hand. It will be understood
that in practice means to affix the artificial hand to an arm, and
means to bring fluid to the manifold input 71, and to discharge
fluid therefrom, will be provided. When a suitable fluid, under
pressure is introduced into the manifold 70 at the input port 71
the fingers 113--116, inclusive, flex toward the palm and the thumb
152 flexes toward the flexed fingers, as in a human hand. The
forefinger 113 is shown partly flexed at 113', in FIG. 7A. When the
fluid pressure is released, the fingers and thumb relax, and resume
the shape shown in FIG. 7.
An artificial human hand has been constructed according to FIG. 7,
and has shown itself capable of grasping objects such as cans,
bottles and ping-pong balls, and has actually "shaken hands" with a
person with an effect remarkably similar to a true human hand.
FIGS. 8 and 8A illustrate a manipulative tool which can be used as
a grasping device, or a wrench. A manifold member 80 has an input
port 81 and four output ports, of which only three ports 82, 83 and
84 are shown, connected together by an interior plenum chamber 85.
Operating fluid (not shown) under suitable pressure is brought to
the input port 81 over a conduit 90 through a normally closed
control valve 91, pipe section 86 and tee 88. A normally closed
pressure-relief valve 92 is fitted to the tee 88. Each valve 91 or
92 is of a type which can be momentarily opened by pressing a
button 91.5 or 92.5, respectively, fitted to it, and which resumes
its normally closed state when the button is released. Thus, when
the control valve button 91.5 is depressed, fluid under pressure
may be admitted to the plenum chamber 85, and when the
pressure-relief valve button 92.5 is depressed fluid under pressure
may be released from the plenum chamber.
A motor element 158 with restraint member 118 is fitted to each
output port. As seen in FIG. 8A, there are two output ports on each
sloped side 85, 87 of the manifold. The FIG. shows one pair of
adjoining motor elements fitted to the output ports 83, 84 on one
sloped side 85, connected together by a web 89. Referring to FIG.
8, when fluid under pressure is admitted to the plenum chamber 85
the motor elements flex toward each other from the sloped sides 85
and 87. If an object, such as a can or bottle 95 (shown in dotted
line) is being grasped, the use of pairs of motor elements joined
to each other as by a web 89 assures a firm grasping of the object.
I have found that if a single motor element 158 is used on each
side of the grasping device, there is a risk of scissorslike
motion, as when one attempts to grasp a device between only two
fingers, which may result in dropping the article being
grasped.
The ends of the motor elements 158 are closed with fingerlike
projections 141, which are useful in picking up small objects.
Either or both of the projections 141 and the confronting surfaces
of the motor elements along the restraint regions may be made
rough, to enhance the ability of the device to hold objects, and to
function as a wrench.
The tool of FIG. 8 can be modified as shown in FIG. 8B, to
substitute a platform member 80.5 on one side of the manifold
member 80.1, which in other respects is the same as the manifold
member 80. The motor element or elements 158 on the sloped side 87
which remains will then act to flex toward and away from the
platform member 80.5 when the tool is in use.
FIG. 9 shows a greatly elongated motor element 160 having restraint
161 along its side, an input conduit 162 at one end and a closure
163 at the other end. The constraint may be configured according to
FIG. 5. A motor element in this configuration will wrap itself
around an object in helical fashion when fluid under pressure is
supplied to it. It may be used as a grasping device for objects of
various shapes. If attached at the end of a lifting device, such as
a chain fall or a cable, it can function as a self-attaching
hook.
The fundamental mode of operation of the invention can be realized
in structures different from that shown in FIGS. 1 to 3. Thus, in
FIG. 10, a bellows 170, which can be made of metal, closed at one
end 171 and having an input conduit 172 at the other, is
constrained at one side by a flexible but substantially
longitudinally inextensible member 173. Alternatively in FIG. 11 a
tubular member 175 having convoluted walls may be used, with
constraint 176 along one side of the walls; in this case the walls
may be made of a material which is longitudinally extensible, like
the circumferentially restrained motor element 15, the convoluted
form of the walls contributing additional longitudinal freedom.
A motor element which resists the tendency to assume a helical
configuration when flexed due to applied fluid under pressure is
shown in FIG. 12. Here a tubular member 180, similar in all
respects to the circumferentially restrained tubular member of the
motor element 15 (FIGS. 1--3) is supplied with a longitudinal
restraint member 181 in the form of two side elements 182 and 183
joined by cross-elements 184. This restraint member is preferably
made in the manner of a bicycle chain, so that it resists twisting,
and a motor element using it will then tend to flex in a plane.
Such motor elements may be used singly on either side 85, 87 of the
manipulative tool shown in FIG. 8, as is illustrated in FIG. 13. In
this case, the restraint member 181, if in the form of a bicycle
chain, can be a single restraint member extending between both
motor elements, and can be joined at an intermediate region to the
top wall 188 of the manifold 80. This arrangement provides a highly
improved chain wrench.
FIG. 14 shows a pressure gauge 190 incorporating a motor element
191 according to the invention. The gauge has a housing 192
provided with a cover (not shown) having an arcuate window 193
shown in dashed outline. The motor element is mounted at the
pressure input end 191.5 in a tube 194 passing through the housing
192 and bent inside the housing so that when the motor element 191
is in the relaxed state its closed end 191.7 lies under the left
hand end (in FIG. 14) of the window 193. An indicator mark 195 is
on the motor element near the closed end 191.7 and disposed to be
visible through the window 193. The longitudinal restraint member
196 of the motor element 191 is so oriented that when fluid under
pressure in excess of ambient atmospheric pressure is admitted to
the motor element (via the tube 194) the motor element flexes to
the right (in FIG. 14) and the indicator mark 195 moves along the
window 193. Indicia (not shown) can be located along the window so
that deflection of the indicator mark 195 can indicate the pressure
applied at the tube 194. This arrangement is a sensitive pressure
gauge, which can be made to measure small pressure changes over a
full scale deflection of the indicator mark 195. Unlike Bourdon
gauges, which flex only very slightly, the gauge of FIG. 14 does
not require additional mechanical elements to move a pointer over a
scale. The motor element 191 is the sole movable member. It will be
understood that the gauge 190 can be designed to measure absolute
pressures as well as relative pressures, since as is explained
above, the motor element 191 can flex in response to applied
pressure below ambient in addition to applied pressure in excess of
ambient.
* * * * *