Note: Descriptions are shown in the official language in which they were submitted.
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This inventioll relates to a penetrometer device a~ used in
the art of soil mechanics. More particularly, this invention relates to a
portab]e penetrometer, that is, one which is hand-held and is more versatile
tl;an many prior art devices.
In the field of soil mechanics it is often desirable to
be able to make measurements, in situ of certain properties of the soil.
These properties include such things as resistance to penetration and shear.
It is to be recognized that such properties may have an influence in deciding
what traffic routes or load bearing capability pertaining to vehicle mobility,
]() or evell what effects~explosive excavation techniques might have on the
soil.
Present devices in this art may incorporate both the ability
to mcaqtJre penetration resistance and shear resistance using a large pene-
trometer on which a standard torque wrench is used to measure shear resis-
tance at the blades mounted on the penetration head. However, these devices
suffer from certain disadvantages, such as not being able to measure both
penetration and shear rcsistance (without requiring the torque wrench);
and lacking compactness. As examples of prior art devices of the kind
el-lvisaged above, tlle reader is referred to Canadian Patent Nos. 522,142
2() and 686,807 which respectively issued on February 28, 1956 to Compagnie
Internationale des Pieux Armes Frankignonl Société Anonyme, and on May 19,
1964 to A.B. Chance Company of Canada Ltd.
The present invention, on the other hand, will overcome a
number of the disadvantages noted above. Moreover, the present invention
is easy to use and reliable. Accordingly, there is provided by this inven-
tion a portable penetrometer apparatus for measuring both the penetration
and shear properties of soil, comprising a tubular body; an elongated shaft
adapted to be supported over a portion thereof in the body, the shaft
being moveable longitudinally thereof in response to a force tending to
cause the shaft to penetrate the soil; first measuring means on the body
to provide a measurement of the force causing penetration; a coil spring
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of predetermined characteristics supported so as to be operatively connected
at one end to both the shaft and to a handle; and second measuring means on
the handle for providing a measurement of torque required to rotate the
shaft in the soil, the coil spring being calibrated so as to enab]e measure-
ment of both the amount of the force causing penetration and the torque
needed to rotate the shaft in the soil. In a more preferred form of this
invention the first measuring means includes a scale and slider assembly,
the scale being calibrated with respect to the coil spring and the slider
being moveable in response to movement of the shaft, to give a reading of
the force at which penetration of~the soil occurs. In another preferred
form, the second measuring means includes a calibrated dial, the dial and
handle being rotatable relative to one another, such that the dial gives a
reading of the torque needed to rotate the shaft in the soil.
These and other features and advantages of this invention will
become more apparent from the detailed description below. That descrip-
tion is to be read Ln conjunction with the accompanying drawing which
illustrates by way of example only, a portable penetrometer apparatus
shown in perspective and embodying this invention.
The penetrometer apparatus is shown overall at lO, and includes
20 a tubular body 12, attached to a lower shaft 14, an upper shaft 15, and a
dual functioning coil spring 16. The upper shaft 15 is of larger diameter
than shaft 14, and is carried within the coil spring 16. A bit 18 of con-
ventional design is attached to one end of the lower shaft 14, and a handle
20 is moveably mounted on one end of the upper shaft 15.
The tubular body 12 is adapted to support the shaft 15 over a
portion of its length in a manner which allows for movement of the shaft
axially of the same. The tubular body 12 includes a diametrically enlarged
sleeve portion 22 which is of a size to closely receive one end of the
spring 16. A suitable locking or restraining means is provided in the
sleeve portion 22 to prevent rotation of the spring 16 therein, in at
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least one of a counterclockwise or clockwise direction. The tubular body
12 is further provided with first measuring means in the form of a slot
and a calibrated scale 24, in which slot and over which scale a plug slider
26 is moveable. The plug slider 26 is moveable in response to movement oE
the shaft 15 relative to the body 12, as occurs when a user attempts to
push the tip or bit 18 into the soil or ground.
The other end of the spring 16 is connected to the handle 20 in
a manner which provides for relative rotational movement between the handle 20
and upper shaft 15. Such movement will typically be unidirectional for the
following reason. In accordance with the present invention, the coil spring 16
is dual functioning, both to provide a calibrated resistance enabling a measur-
ing of the force needed to enable the bit 18 to penetrate the soil, as well as
for providing a measure of the torque needed to rotate the bit 18 in that soil.
The coil spring 16 has inherent spring characteristics. These are predetermined,
although they can be varied by design when choosing the type of metal, the coil
diameter, the wire diameter and so on when manufacturing the spring 16. The
handle 20 is tubular in cross-section, and formed with a shoulder or stop
interiorly thereof (not shown). This stop will engage the free end of the wire
making up the coil spring 16, such that rotation of the handle 20 with the stop
butting against the free end of the spring 16 will enable the spring to deliver
a measurable amount of torque to the tubular body 12, shaft 14 and bit 18
when attempting to rotate the latter in the soil. The upper end of the shaft
15 carries a calibrated dial 28, i.e., the dial being marked with graduations
calibrated with respect to the torsional properties of the spring. An
appropriate marker 30 is provided on the handle 20, such that rotation of
that handle against resistance of the bit 18 in the soil will be indicated
by the marker 30 read against the dial 28. The marker 30 will advance
against the dial 28 until such time as the torque has reached a value at
which the soil resistance breaks down allowing the bit 18 to rotate. It
clearly is preferable that marker 30 would constitute a pointer, supported
so as to be advanced upon rotation of the handle as torque increased, but
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remaining at the point of greatest ~dvancement when the torque backed off
due to shearing of the soil. Such a pointer would need resetting to a
datum (zero) after each shear measurement was taken.
In use, therefore, a person would grasp the penetrometer 10
and push downwards on the soil whose properties were to be examined. Push-
ing downwards causes the spring 16 to compress somewhat until such time as
the downwardly directed force equalled the resistance to penetration of the
soil. Compressing of the coil spring 16 is accompanied by downward move-
ment of shaft 15 relative to the body 12, thus causing the plug/slider 26
to advance over the scale 24. This yields a reading of force needed to
penetrate the soil.
To measure the shear properties of the soil, the user now
grasps the handle and turns it. The stop within the handle engages
the end of coil spring 16, which begins to resist the turning force. As
the latter is increased, the marker 30 advances against the dial 28 until
a torque is developed which equals or just overcomes the resistance of the
soil to shear. The bit 18 will then rotate in the soil, and no further
advancement of the marker 30 occurs.
It i8 to be aeen that a series of coil springs 16 could be
supplied with each apparatus 10. Each spring would have predetermined
spring characteristics which could be interchanged to give added accuracy/
sensitivity in obtaining the penetration and shear characteristics of the
soil.
Further yet, the specific structure of the measuring means
shown herein at 24/26 and 28/30 can vary, so long as their operation is
compatible with operation of the penetrometer apparatus described herein.
The foregoing has described a preferred ernbodiment of a pene-
trometer apparatus according to the present invention. Some modifications
have also been suggested. It is intended herein to encompass all such
variations as would be evident to practioners skilled in this art, and
which fall within the scope of the claims below.
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