Measuring device

A parallel suspension reed type measuring device has its internal components maintained in a weightless condition by a bouyant fluid. A pair of vertical reeds and an amplification arm mechanically amplify the movement which is imparted to a measuring spindle in response to a quantity being measured. The measured quantity is magnified optically by a lens system and is projected onto a screen.

BACKGROUND AND BRIEF DESCRIPTION OF THE INVENTION 
This invention relates in general to an improved measuring device which is 
suitable for use as an indicator in a comparator test set. More 
particularly, the measuring device of the present invention is comprised 
of a parallel suspension reed type of measuring device wherein the weight 
of its moving components is effectively eliminated to thereby improve the 
accuracy of the measurements made by the device. By maintaining the moving 
components of the device in a weightless condition, these components are 
insulated from outside forces and disturbances to thereby ensure that the 
accuracy of this device is not affected by external factors such as 
position, gravity, temperature, etc. 
Accurate measurement represents one of the most critical aspects of 
industrial inspection and production. Because a measurement is only as 
precise as the instrument used in making it, all measuring devices and 
particularly those used by industry should be extremely reliable in terms 
of accuracy and repeatability. In other words, it is highly desirable for 
a measuring device which is frequently used by industry to be capable of 
repeatedly providing accurate measurements. Another desirable feature of 
any measuring device is that it exhibit a short lag time between start and 
readout of the measurement. Finally, it is extremely important for a 
measuring device to be easy to use and capable of producing high 
amplification of the measured quantity without appreciable distortion of 
the measurement. 
A reed measuring device represents a presently known measuring device which 
exhibits many of these characteristics. A reed measuring device is 
comprised of a pair of blocks which are positioned adjacent to each other 
and are joined together by a pair of parallel reed suspension springs. One 
of the blocks is rigidly fixed while the other block is free to move 
relative to the stationary block. The movable block has a measuring 
spindle connected to its bottom and a vertical reed attached to the inside 
top part of the block. A second vertical reed is similarly attached to the 
inside top part of the stationary block. The two vertical reeds are then 
connected to each other at their upper ends and a pointer is attached to 
them at this point. During the gauging or measuring operation, the gauging 
spindle is brought in contact with the piece to be measured causing the 
movable block to be moved upward in response to the measured dimension of 
the piece. This upward movement of the movable block causes the vertical 
reed attached to this block to slip past the vertical reed attached to the 
stationary block. Since these reeds are joined at their upper ends, 
movement of one reed past the other reed is prevented causing both of the 
reeds to swing through an arc which is representative of the measured 
quantity. The pointer moves in unison with these reeds to mechanically 
amplify the measured quantity. This arcuate movement of the pointer is 
then converted into a reading suitable for display. 
Since this measuring device employs no gears, bearing surfaces or rubbing 
contacts, friction and surface wear between the movable components of this 
device are entirely eliminated. As a result, this measuring device is 
extremely reliable when properly used. This device, however, possesses an 
inherent disadvantage which is common to all fulcrum and lever type of 
measuring devices. In particular, the weight of the moving components can 
and do have a significant impact upon the operation of the device if the 
device is not used in a truly vertical position. If the measuring device 
is improperly positioned, the weight of the floating block is not properly 
carried by the reeds and the accuracy of the measurement is 
correspondingly affected. Accordingly, this type of measuring device is 
accurate only when it is used in a truly vertical position. 
The measuring device of the present invention, however, overcomes this 
problem by maintaining its movable components in a weightless condition. 
In particular, the movable block is constructed to have a hollow inner 
cavity which is either evacuated or filled with a gas that increases the 
buoyancy of the block. The vertical reeds are in turn attached to each 
other by means of a buoyant joining piece which is also constructed to 
have a hollow inner cavity. The inner cavity of the buoyant joining piece 
is either evacuated or filled with a gas that increases the buoyancy of 
this piece. A hollow amplification arm is attached to the buoyant joining 
piece to mechanically amplify the arcuate movement imparted to this piece 
during a measurement. The hollow portion of the amplification arm is 
either evacuated or filled with a gass which increases the buoyancy of 
this component. The movable components are also encompassed by a fluid 
having a density which substantially reduces the weight of these 
components. Through proper selection of the gas used to fill the hollow 
cavity in the movable block, the buoyant joining piece and the 
amplification arm and the fluid used to encompass these components, the 
movable components of the device are maintained in a weightless condition. 
By maintaining the movable components in a weightless condition, the 
parallel reed suspension springs are only used to provide gauging pressure 
and to align the movable components of the device. Since the parallel reed 
suspension springs do not have to support the weight of the movable 
components, the measuring device of the present invention may be used in 
any position without a detrimental effect upon the accuracy of the 
measurements made by the device. In addition, the parallel reed suspension 
springs and vertical reeds can now be made to have a thinner more flexible 
nature. As a result of this type of construction, the measuring device of 
the present invention is capable of providing high amplification while 
still exhibiting low gauging pressure. Another advantage of this measuring 
device is that it is capable of providing greater amplification of the 
quantity being measured. The degree of amplification is established by the 
length of the flexible portion of the vertical reeds divided by the 
distance between the center line of these reeds plus the length of the 
amplification arm. By making the vertical reeds thinner, the center line 
of these reeds can be positioned closer together to thereby increase the 
degree of amplification while reducing the size of the device. As a 
result, the measuring device of the present invention is more compact, 
easier to use, and less expensive than the reed measuring devices which 
are presently available. 
The measuring device of the present invention exhibits the added feature of 
providing improved magnification of the amplified measurement for readout. 
In the preferred embodiment of the invention, a target is attached to the 
amplification arm for movement in combination therewith. This target is 
comprised of a transparent material having a curved shape and a graduated 
face. The face of the target is then magnified by means of a lens system 
which is comprised of an objective lens positioned near the target and an 
occular lens appropriately positioned with respect to the objective lens. 
By properly arranging the distance between these lenses, they operate as 
an inverted microscope to provide an enlarged image of at least a portion 
of the target. The image of the target is then focused through an eye 
piece for projection onto a screen comprising ground glass or a similar 
type of material for easier readout of the magnified measurement. The 
screen has a reference line etched on it to provide a reference point from 
which readings may be made. This type of lens system allows for the 
measuring device to be capable of being made more compact and greatly 
extends the useful range of the instrument by eliminating the need for a 
long light path or complex electrical circuitry. 
It is therefore an object of the present invention to provide a measuring 
device wherein the device's movable components are maintained in a 
weightless condition to improve the accuracy of the device. 
Another object of the present invention is to provide an improved measuring 
device of the character described which is capable of providing extremely 
accurate measurements regardless of the position of the device. 
Another object of the present invention is to provide an improved measuring 
device of the character described which is capable of accurately 
amplifying the measured quantity. 
A further object of the present invention is to provide an improved 
measuring device of the character described which includes an inherent 
dampening effect which significantly decreases lag time between the start 
of the measurement and readout of the measured quantity. 
An additional object of the present invention is to provide a measuring 
device of the character described which is capable of providing high 
amplification while still exhibiting low gauging pressure. 
Another object of the present invention is to provide a measuring device of 
the character described which is capable of producing a greater degree of 
amplification in a fairly compact device thereby making the device small 
in size, easy to use and low in cost. 
An additional object of the present invention is to provide an improved 
measuring device of the character described which is capable of providing 
accurate measurements which are not effected external factors such as 
position, gravity, temperature, etc. 
It is another object of the present invention to provide an improved 
measuring device of the character described which is capable of magnifying 
the amplified measurement to facilitate readout of the measured quantity. 
It is a further object of the present invention to provide an improved 
measuring device of the character described which is capable of being 
incorporated into a hand tool. 
Other and further objects of this invention, together with the features of 
novelty appurtenant thereto, will appear in the course of the following 
description.

Referring now to FIGS. 1 and 2, numeral 10 generally designates a measuring 
device constructed in accordance with a preferred embodiment of the 
present invention. This measuring device is provided with an outer casing 
12 which is capable of containing a fluid therein. The outer casing is 
arranged to completely enclose the operable components of the device and 
is constructed of plastic or a sturdy metal which is not subject to 
oxidation. The outer casing may, however, be constructed of a metal which 
is subject to oxidation if the inner surface of the device is provided 
with a non-corrosive coating. 
The operable components of the measuring device include a stationary block 
14 which is fixedly secured to the inner surface of the outer housing. 
Block 14 has a rectangular base portion 16 and three rectangular extending 
portions 18, 20 and 22 which protrude outward from the base portion to 
form an E shaped structure. This block is constructed of a sturdy material 
such as plastic, glass, or a metal which is not susceptible to corrosion. 
The block may also be made out of a corrosive metal if the exterior of the 
block is properly treated to prevent corrosion thereof. 
The measuring device also includes a movable block 24 which is coupled with 
the fixed block 14 by means of a pair of gauging pressure and guide 
springs 26 and 28. Block 24 is constructed of a sturdy, lightweight 
material such as glass, quartz or any lightweight metal which is not 
subject to corrosion. The movable block may also be constructed of a 
lightweight metal which is subject to corrosion if the outer surface of 
this block is properly treated to prevent corrosion thereof. The movable 
block is made to have a hollow inner chamber 38 which is either evacuated 
or filled with a gas that increases the buoyancy of the block. 
The gauging pressure and guide springs 26 and 28 serve to couple the 
movable block 24 with the stationary block 14. In particular, one end of 
spring 26 is fixedly secured to stationary block 14 between extending 
portions 20 and 22 while the other end of this reed is fixedly secured to 
the movable block 24. Spring 28, on the other hand, is fixedly secured to 
stationary block 14 between extending portions 18 and 20 and to the 
movable block 24. These springs are constructed of a material having an 
elastic nature such as steel. Since the movable components of this device 
are maintained in a weightless condition the gauging pressure and guide 
springs do not have to support any of the weight of these components and 
are only used for alignment purposes. As a result, these springs may be 
constructed to have a thinner more flexible nature thereby allowing the 
measuring device of the present invention to exhibit a low gauging 
pressure. 
A measuring spindle 40 is attached to the bottom portion of the movable 
block so as to pass through a spindle opening 42 in the outer housing of 
the measuring device. Measuring spindle 40 is comprised of a removable tip 
44, a cylindrically shaped lower mounting piece 46 and a cylindrically 
shaped upper mounting piece 48. The removable tip 44 is constructed to 
have a contacting surface 50 which is made of a wear resistant material 
such as hardened steel. A threaded pin 52 is integrally formed with the 
tip's contacting surface to extend outward therefrom at a right angle 
therewith. This pin is arranged to be received by an internally threaded 
aperture 54 in the lower mounting piece 46. The lower mounting piece 46 is 
in turn attached to the upper mounting piece 48 by means of a threaded pin 
56 which is received by an internally threaded aperture 58 in the bottom 
surface of the upper mounting piece. The upper mounting piece is finally 
attached to the bottom portion of the movable block by means of a threaded 
pin 60 which is fixed to the top surface of the upper mounting piece. This 
pin is received by an internally threaded aperture 62 which is defined in 
the bottom of the movable block. 
A membrane 64 is provided to form a fluid seal about the measuring spindle. 
This membrane is fixed to the outer casing of the measuring device by 
means of an O-shaped mounting ring 66. Mounting ring 66 is provided with a 
threaded outer surface which is threadably engaged by an enlarged portion 
of spindle opening 42. As mounting ring 66 is tightened, the membrane is 
pinched between this ring and the outer casing of the measuring device to 
secure the membrane in place within the spindle opening. A hole (now 
shown) in the center of this membrane allows threaded pin 58 to pass 
through it en route to engagement with internally threaded aperature 58. 
As the lower mounting piece is brought in contact with the upper mounting 
piece, the membrane is pinched between the top surface of the lower 
mounting piece and the bottom surface of the upper mounting piece to form 
a fluid seal therewith. Membrane 64 is of a flexible nature which allows 
it to move in combination with the measuring spindle. While this membrane 
has an effect on the gauging pressure of the device, the resultant effect 
of this membrane is so negligable that it does not have an appreciable 
effect upon the accuracy of the device. A vertical reed 63 is attached to 
the upper portion of movable block 24 to extend upward thereform at a 
right angle therewith. Another vertical reed 65 is attached to extending 
portion 22 of stationary block 14 to extend upward from this block at a 
right angle therewith. The free ends of these reeds are in turn connected 
to each other by means of a buoyant joining piece 67. The buoyant joining 
piece is constructed of a sturdy, lightweight material such as glass, 
quartz or any lightweight metal which is not subject to corrosion. This 
piece may also be constructed of a corrosive metal if the outer surface of 
the block is provided with a non-corrosive coating. The buoyant joining 
piece has a hollow inner cavity 68 which is either evacuated or filled 
with a gas that increases the buoyancy of this piece and the vertical 
reeds to which it is attached. 
An amplification arm 69 is attached to the buoyant joining piece to 
mechanically amplify the arcuate movement imparted to this piece during a 
measurement. The amplification arm is constructed of a sturdy, lightweight 
metal which is not susceptible to corrosion. The amplification arm may 
also be constructed of a sturdy, lightweight metal which is subject to 
corrosion if the exterior of this arm is properly treated with a 
non-corrosive coating. The amplification arm is provided with a hollow 
inner chamber 70 which may be either evacuated or filled with a gas that 
increases the buoyancy of this piece. 
A flexible membrane 71 is secured to the inner surface of the outer casing 
to form an air space over an opening 72 in the outer casing of the device. 
Membrane 71 cooperates with opening 72 to compensate for variations in the 
pressure of the fluid contained within the outer casing of the device. 
A target 73 is attached to the free end of the amplification arm for 
movement in combination therewith. The target is constructed of a 
transparent material and has a scale imprinted on it to provide an 
indication of the relative position of the device's movable components to 
thereby provide a reading of the quantity being measured. 
Optical magnification of the reading is performed by a series of lenses 
which are arranged to form an inverted microscope. These lenses are 
appropriately mounted within a watertight chamber 74 which is positioned 
in the housing of the device so that the top wall 75 of the chamber sits 
below the amplification arm of the device. This chamber is also formed by 
a plurality of lateral side walls 76, 78 and 80 which are fixedly secured 
to the outer housing of the device and to the top wall of the chamber to 
form a closed watertight chamber. 
A light source 82 is secured to the outer housing and oriented to project a 
beam of light onto the target through a condenser 84 which is 
appropriately mounted within an opening 86 in the outer housing of the 
device by means of an O-shaped mounting ring 87. The condenser is mounted 
to the outer housing to form a watertight seal therewith. 
The lenses which are used to magnify the reading on the target include an 
objective lens 90 which is positioned adjacent to a transparent window 92 
in the chamber which encloses the lens system, an ocular lens which is 
comprised of lenses 94 and 96, and a simple achromatic lens 98 which is 
capable of projecting an image onto a screen 100. The objective lens 
operates to provide an enlarged image of the portion of the target which 
is in front of the transparent window 92. The enlarged image is then 
transferred by means of reflective devices 102 and 104 to the ocular lens 
for further magnification of the image. Reflective devices 102 and 104 are 
either comprised of mirrors or prisms which are appropriately positioned 
to transmit the image produced by the objective lens to the ocular lens. 
The magnified image is then projected onto a screen 100 by means of lens 
98 to allow for easier viewing of the reading. A reference line is etched 
or otherwise imprinted on screen 100 to provide a set reference point from 
which readings can be made. It should be emphasized at this time that the 
shown lenses and orientation thereof are merely illustrative and are not 
intended to limit the scope of this invention to a particular lens system. 
Referring now to FIGS. 3 and 4 a second measuring spindle 110 which is 
preferrable for use at high amplification is shown in these figures. This 
measuring spindle, like the spindle shown in FIGS. 1 and 2, is attached to 
the bottom of the floating block and passes through a spindle opening 112 
in the housing of the measuring device. As shown in these figures, this 
measuring spindle is comprised of a contact tip 114, a pair of 
cylindrically shaped adjusting pieces 116 and 118, a cylindrically shaped 
lower mounting piece 120 and a cylindrically shaped upper mounting piece 
122. 
The contact tip 114 is constructed of a wear resistant material such as 
hardened steel and is provided with a threaded member 124 which protrudes 
upward from the top surface of the tip at a right angle therewith. Member 
124 is threadably engaged by an internally threaded opening 126 which is 
defined in the bottom surface of adjusting piece 116 to removably secure 
the contact tip to this piece. Adjusting piece 116 is provided with a 
dovetail 128 which protrudes upward from the top surface of this piece. 
This dovetail is in turn received by a mortise 130 in the adjusting piece 
118. A locking screw 131 is used to fix the position of the dovetail 128 
within the mortise 130. 
Adjusting piece 118 is provided with a mounting pin 132 which protrudes 
upward from the top surface of the piece at the center axis thereof. This 
mounting pin is in turn received by an aperture 134 which is defined in 
the bottom surface of the lower mounting piece at the center axis thereof. 
A locking screw 136 is provided to secure mounting pin 132 in place within 
aperture 134. 
The lower mounting piece 120 is in turn attached to the upper mounting 
piece by means of a threaded pin 138. This pin is attached to the upper 
surface of the lower mounting piece and protrudes upward therefrom at a 
right angle therewith. An internally threaded opening 140 is defined in 
the bottom surface of the upper mounting piece 122 to threadably receive 
pins 138 to thereby secure the lower mounting piece to the upper mounting 
piece. 
A membrane 148 is located between the upper and lower mounting pieces to 
form a watertight seal about the measuring spindle. This membrane is 
secured to the outer housing of the measuring device by means of an 
O-shaped mounting ring 150 which has a threaded outer surface. The 
O-shaped mounting ring is arranged to sit within the enlarged portion of 
opening 112. The enlarged portion of this opening is internally threaded 
to engage the outer surface of the mounting ring. As the ring is 
tightened, the membrane is pinched between the top surface 152 of this 
ring and the top wall 154 of the enlarged portion of opening 112 to secure 
the membrane in place within this opening. Membrane 148 is provided with a 
center hole 156 which passes threaded pin 138 for engagement with 
internally threaded aperture 140. Once the lower mounting piece is firmly 
secured to the upper mounting piece, the membrane is pinched between these 
two mounting pieces to fixedly secure the membrane between these pieces to 
form a watertight seal about this measuring spindle. 
In operation, the movable components of the measuring device are maintained 
in a weighless condition to thereby insulate these components from various 
external factors such as position, gravity, termperature, etc. To achieve 
this condition the outer casing is filled with a fluid which totally 
encompasses the movable components of the device. In addition, the hollow 
portions of movable block 24 buoyant joining piece 67 and amplification 
arm 69 are either evacuated or filled with a gas which increases the 
buoyancy of these components. Through proper selection of the fluid which 
encompasses the movable components and of the gas placed within the 
movable block, the weight of the movable block vertical springs, buoyant 
joining piece and amplification arm may be totally eliminated or reduced 
to a point where it has a negligible effect upon the measurement. 
Selection of this fluid is determined in accordance with the combined 
weight of the movable components of the device. In particular, the 
selected fluid should have a density which matches the density of the 
movable block vertical reeds, buoyant joining piece and amplifications arm 
when the inner portion of these components are either evacuated or filled 
with gas. In this way, the weight of these components is either totally 
eliminated or reduced to the point where it is negligible. 
Thereafter, the measuring device is mounted on the stand of a comparator 
test set so that the measuring spindle is capable of contacting a 
measuring standard which is placed on the base of the test set. In 
particular, the measuring device is positioned on the stand so that the 
reading on the target is at a set zero position. 
Once the measuring device is properly positioned on the stand of the test 
set, a test piece is placed on the base of the test set and oriented so 
that the measuring spindle 40 comes in contact with the outer surface of 
this piece along the dimension to be measured. As the measuring spindle is 
brought in contact with the piece being measured, the spindle is moved a 
distance corresponding to the measured dimension of the piece. Since the 
measuring spindle is physically attached to the movable block 24, movement 
of the spindle is in turn imparted to this block causing the gauging 
pressure and guide springs to deflect slightly. Movement of the movable 
block also causes its vertical reed 63 to be laterally moved a distance 
corresponding to the quantity being measured. Since the vertical reeds 63 
and 65 are attached to each other by means of the buoyant joining piece 
67, lateral movement of reed 63 causes both of these reeds to swing 
through an arc which is proportional to the measured quantity. This 
arcuate movement of the vertical reeds and buoyant joining piece is then 
mechanically amplified by the amplification arm 69. The amount of 
mechanical amplification is controlled by the length of the amplification 
arm. A unique feature of the measuring device of the present invention is 
that the amplification arm can be made as long as necessary to provide the 
desired amplification without any adverse effects upon the accuracy of the 
measurement since the arm is maintained in a weightless condition. 
Movement of the amplification arm causes target 73 to move in unison 
therewith to provide a readout of the quantity being measured. In a normal 
comparator test set, the measuring device is arranged to obtain a reading 
indicative of the difference between the measured dimension of the 
measuring standard and the measured dimension of the test piece. Since the 
movement of the target by the amplification arm is directly proportional 
to the distance the measuring spindle has been moved, the target may be 
ruled to provide an accurate readout of the quantity being measured. 
Optical magnification of this readout is performed by a series of lenses. 
In particular, the portion of the target adjacent to the concentrator 84 
is illuminated by light source 82. The concentrator is an auxiliary lens 
which is operable to condense the light from the light source to brightly 
and uniformly illuminate the target. 
An enlarged image of this portion of the target is produced by the 
objective lens 90 which is aligned with the light source and concentrator. 
The enlarged image is then directed to the ocular by means of reflective 
devices 102 and 104. The ocular is comprised of a pair of lenses 94 and 96 
which cooperate to further magnify the enlarged image of the target. 
Another lens 98 is then used to project the magnified image of the target 
onto screen 100 for viewing. 
It should be pointed out at this time that the gauging pressure of this 
device is solely determined by the gauging pressure and guide springs, the 
rigidity of the membrane 64, and the amount of fluid contained within the 
device. As the amount of fluid increases, the pressure exerted on membrane 
64 also increases. To keep this pressure from affecting the accuracy of 
the measurement, it is desirable to keep the amount of fluid at a minimum. 
In addition, the size of the spindle opening 42 should be made as small as 
possible to minimize the surface area of membrane 64 thereby providing 
less surface area on which the fluid may act. The amount of fluid 
contained within the outer housing may be minimized through design 
features which are readily apparent to those of ordinary skill in the art. 
For example, various spacer blocks may be strategically placed within the 
measuring device to fill the open areas which would otherwise be occupied 
by fluid. These spacer blocks have not been shown in these figures for 
purposes of clarity and to facilitate the description of the device. 
The measuring spindle shown in FIGS. 3 and 4 is preferable for use in high 
amplification devices. This measuring spindle also allows for accurate 
calibration of the measuring device. 
Calibration of the device is performed before the buoyant joining piece, 
amplification arm and target are attached to the vertical reeds. The 
device to be calibrated is then mounted on a comparator test set and 
lowered until the contacting tip of the measuring spindle just comes in 
contact with an accurate spring type scale. Thereafter, the fixed block is 
lowered until a desired amount of force is exerted on the scale. The 
adjusting pieces of the device are then manipulated until both of the 
vertical reeds are parallel to each other. In this way the device can be 
calibrated to provide a desired amount of gauging pressure while still 
maintaining the measuring spindle in a preferred position directly below 
and in line with the lines of force exerted by the gauging pressure and 
guide springs upon the movable block. The buoyant joining piece is then 
attached to the vertical reeds. An amplifying arm and target are then 
temporarily attached to the buoyant joining piece. A measuring standard is 
then placed on the comparator test set and the measuring device is 
adjusted until the target is in a zero position. Thereafter, a second 
measuring standard is put on the comparator test set. The second measuring 
standard differs from the first standard by a known quantity which is 
preferably one-half the range of the instrument. A reading is then taken 
to check the accuracy of the device. If the last graduation on the scale 
corresponds exactly to this value, the amplifying arm is permanently 
attached to the buoyant joining piece and the measuring device is fully 
assembled. If the reading on the target falls short of a full scale 
deflection, amplification arms of increasing length are then attached to 
the buoyant joining piece until a full scale deflection is obtained. A 
greater than full scale deflection is corrected, on the other hand, by 
using an amplification arm of a shorter length. In this way the degree of 
amplification can be varied simply by changing the length of the 
amplification arm.