Geometrical instruments – Distance measuring – Single contact with a work engaging support
Reexamination Certificate
1998-04-13
2001-10-09
Fulton, Christopher W. (Department: 2859)
Geometrical instruments
Distance measuring
Single contact with a work engaging support
C033S0010HH, C033S624000
Reexamination Certificate
active
06298574
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field or the Invention
The present invention pertains to instruments to depth measurement or loosely laid pavement mixtures and more particularly to depth measurement instruments used to measure a hot bituminous pavement layer while paving before compaction to determine whether the proper depth or pavement has been set in place.
2. Related Prior Art
Presently, measuring the mat thickness of a bituminous paving layer before compaction is normally done by a very simple portable device. This device usually consists of a one quarter inch rod that has an adjustable washer. The rod with washer fixed in place is inserted into the recently laid bituminous pavement mixture of aggregates and asphalt cement. The rod may be several feet long so that it is easy to handle and can measure significant depths of pavement. The rod may also be threaded so that a lock nut can be used in conjunction with the washer. The washer may be fixed to the nut so that it will not slide when the nut is screwed in place. In most instances, the washer is used in conjunction with a set screw. This arrangement avoids the problem of asphalt tar filling in the threads and preventing movement to the nut.
A ruler normally is used to measure the distance from the end of the rod to the washer to set the desired mat thickness. The washer is then locked down on the rod usually by means of a set screw. The person measuring the mat or bituminous paving layer thickness then walks where the mat has just been laid and shoves the rod into the bituminous paving layer. The rod is pushed into the bituminous paving to see if the rod goes to or exceeds the distance of the washer from the end of the rod. If the washer does not touch the mat, the thickness of the mat is increased. If the bituminous paving exceeds the depth of the washer, the thickness is decreased.
One problem associated with such a device comes from the composition of the paving material itself. This problem occurs primarily because of the size of some of the aggregates used to make certain types of bituminous paving. In some types of bituminous paving the larger aggregates may be one and one half inches in diameter and larger in size. The washer generally is two inches in diameter. If the rod is pushed into the bituminous paving when the mat depth exceeds the desired depth, the washer may be held up by one of these large aggregates before the rod reaches the bottom of the paving layer. This can lead to an inaccurate reading witch results in a false measurement of the thickness of the mat.
When the washer hits a large aggregate and fails to reach the bottom of the pavement layer and an inaccurate measurement is taken. In one situation, the spreader operator may mistakenly believe the depth to be proper and continues to lay down a mat too thick. Or, possibly in another situation, the operator may receive an indication of the depth being too thick. However, since the washer was held up by a large aggregate, the operator would correct for a paving layer having a thickness of too great of a depth by the measured amount. Unfortunately, a correction was made but not great enough because the depth gauge did not measure the true depth. This would result in the amount of reduction to be too small and result in a loss because of the error in the measurement obtained by the rod and washer device. In both of these cases, too much bituminous is being laid and costs can increase by as much as twenty percent.
SUMMARY OF THE INVENTION
The method and apparatus of the present invention eliminates the problem of faulty depth measurement encountered by prior art depth measurement gauges. The bituminous paving depth gauge of the present invention eliminates the need of the fixably attached washer that in some cases can prevent the rod from going down to the complete depth of the mat.
The method of the present invention for measuring the paving layer depth in a bituminous paving operation includes inserting a rod member into the pavement layer, aligning an indicator on the rod with a graduated measuring section on a support member and reading the depth. The rod member has an indicator at its top and a gradually narrowing end for insertion into the paving layer. The gradually narrowing end is designed so that the rod member can easily be inserted into the uncompacted bituminous paving mixture by pushing the aggregates out of the way, allowing the tip of the rod to touch the prepared surface for receiving the pavement. The rod member is supported by a support device having a top portion and a bottom portion. The top portion includes a measuring section having predetermined graduations. This measuring section acts in cooperation with the indicator to provide a measurement of the pavement layer or mat. The bottom portion has support sections for receiving and sildeably holding the rod member. Reading a depth measurement is done according to the position of the indicator with respect to the measuring section. The method for measuring the paving layer depth in a bituminous paving operation may also include preventing the support device from sinking into the paving with a base member mounted on the bottom portion of the support device.
The apparatus of the present invention provides a top reading bituminous paving depth gauge to determine the thickness of paving layers. The gauge of the present invention includes a depressible rod operatively associated with a structural rod support system. The depressible rod has a bottom portion that is slideably mounted in the rod support system. The rod support system has an upper portion and a lower portion. The upper portion includes a graduated measuring gauge fixed on the rod support system. The lower portion has a bottom support device fixed to the lower end of the rod support system. The bottom support device acts as a foot for the measuring gauge. This foot rests on the bituminous paving when the measuring gauge is set in place to measure the depth of the mat. The bottom support device also acts to receive the lower portion of the depressible rod. The top reading bituminous paving depth gauge operates without any washers on the measuring depressible rod to prevent false measurements due to the presence of large aggregates. The upper portion with its graduated measuring gauge fixed on the rod support system operates in conjunction with an indicator on the top of the depressible rod to provide a mark for accurately measuring the depth of the bituminous paving. The indicator is at zero on the measuring gauge when the bottom of the depressible rod is flush with the foot of the bottom support device.
The rod portion of the present invention has no washer that would prevent the rod from going the complete depth of the mat. The rod is preterably five feet long and has a cone shaped bottom to allow insertion into the bituminous paving layer or mat. With the narrowed tip of the cone shaped bottom at the end of the rod, the rod is pushed into the bituminous paving with little effort by the operator of the bituminous layer measuring device. The measuring of the thickness is done from the top of the device of the present invention. When the rod enters the paving the top of the rod lines up with the gauge which is in one quarter inch increments giving an accurate measurement of the mat thickness. The foot on the bottom of the rod support portion of the device of the present invention is preferably three inches by three inches and keeps from sinking into the bituminous paving. The total length of the bituminous paving depth gauge of the present invention is approximately five feet. In this manner the measuring portion of the apparatus of the present invention is places at eye level for easy reading of the depth of the mat. The bituminous paving depth gauge of the present invention is preferably made from aluminum so that is light weight and portable. Thus, it may be carried in a vehicle or in a case mounted on the spreader which would give personnel easy access to the device of the present invention for measuring the bituminous pav
APAC Inc.
Connaughton Martin
Fulton Christopher W.
Kowalski Frank J.
Venne Vernon F.
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