Geometrical instruments – Straight-line light ray type – Rod or target
Reexamination Certificate
2000-06-28
2004-11-09
Gutierrez, Diego (Department: 2859)
Geometrical instruments
Straight-line light ray type
Rod or target
C033S506000
Reexamination Certificate
active
06813840
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention concerns retroreflecting metrology devices used, in particular, to measure deformation of natural structures (the ground, rock formations) or manmade structures (civil engineering works, embankments, cuttings).
Metrology measurements on such structures are conventionally effected by rangefinders which use “Invar” (registered trademark) wires. In outline, they entail implanting supports in the structure whose dimensional evolution is to be checked, and wire attachment members are removably mounted on the supports. An adjustment member is used to stretch wires whose ends have been attached to two respective attachment members, measuring (allowing for the length of the wires) the distances between reference points of the attachment members, removing the equipment with the exception of the supports, and repeating the above operations each time the dimensional evolution of the structure is to be checked.
The supports are therefore permanently anchored in the structure but the rest of the equipment is removable. The attachment members have a structure such that merely knowing the distance between the respective attachment points of two members, between which one or more wires are stretched, enables the distance between the reference points thereof to be deduced so that, in the absence of deformation, the measurements are reproducible, even at intervals of several years, and so that the changes in the measured distances are a perfect reflection of the deformations of the structure. To enable measurements to be effected over a wide range of distances, wires of calibrated length can be joined together end-to-end. To obtain great accuracy, an attachment member, one or more wires, and an adjustment member comprising a section of measurable adjustable length and a calibrated tensioner are inserted between two reference points. Thus, the wires are always tensioned with the same tension. As the are made of Invar, their length varies little with temperature. The distance between the two, reference points in a straight line from one reference point to the other is therefore equal to the sum of the lengths of the wires tensioned to the appropriate tension plus the length of the adjustment member plus the length of the attachment member between the calibrated wire and the corresponding reference point. The reproducibility of the measurements is naturally related to the necessity for the reference point to always be identically positioned relative to the supports of all the attachment members.
FIG. 1
illustrates the use of such rangefinders to measure changes in the cross section of the vault of a tunnel, for example a railway tunnel in an underground station.
Seven supports, each of which can removably carry an attachment member, are anchored in the plane of the cross section. A support A is anchored into the keystone, two supports B and C are symmetrically anchored at the corners of the platforms overlying the tracks, two supports D and E are symmetrically anchored to the skewbacks of the vault at the same level, and two supports F and G are symmetrically anchored in the vault or at the springers, at the same level, respectively between the supports D and E and the keystone support A.
The wires are respectively tensioned between B and D, D and F, F and A, A and G, G and E, E and C, C and B, and there are therefore only seven distances to be measured. With seven supports it is theoretically possible to check 21 distances, but in most cases it is sufficient to check 17 distances to obtain a good image of the evolution of the structure.
FIG. 2
shows diagrammatically a device including a support
1
and an attachment member
2
(which are known in the art), and an assembly member
3
by means of which the attachment member is fixed to the support.
The support
1
includes, along a central axis, a support base
11
adapted to be fixed into the structure whose evolution is to be checked, and a receptacle head
12
connected by a transition region
13
. The head
12
is adapted to carry the assembly member, externally of the structure. The support base can have projections at its perimeter to anchor it more reliably into the structure, for example a longitudinal succession of annular projections or a screwthread of appropriate profile if it is cylindrical (not shown). It can be anchored by embedding it in resin or in expanding cement, for example. The head
12
is generally cylindrical and has an external screwthread
14
to enable the assembly member
3
, which has an inside screwthread
31
for this purpose, to be screwed onto it. The transition region
13
is frustoconical. The head
12
includes a generally cylindrical housing
15
open to the outside at the free end opposite the support base
11
via a frustoconical seat
16
consisting of a bevel at an angle in the range of approximately 40° to approximately 50°. For technological reasons, the outside screwthread
14
preferably does not extend as far as the free end of the support, and in the region of the free end of the support the outside diameter of the support is not greater than the diameter at the root of the screwthread.
The attachment member
2
is made up of several components, and to be more precise includes a bush
21
having a generally cylindrical body adapted to be inserted into the housing
15
and a flange which bears on the frustoconical seat
16
. The bush
21
includes a central passage in which is accommodated a fixing rod
22
for an attachment finger
23
fixed to the rod externally of the head
12
to pivot about a pivot
24
perpendicular to the longitudinal central axis of the support
1
. The fixing rod
22
has a screwthread along its end region accommodated in the head
12
onto which is screwed a nut for fixing the rod to the bush, bearing against a face of the bush with a washer between them. The pivot
24
is accommodated in a transverse bore in the opposite end region of the fixing rod
22
. This region of the fixing rod has an area which bears against the face of the flange of the bush
21
outside the head
12
so that the longitudinal axis of the pivot
24
is at a fixed distance from the outside face of the flange. The point of intersection of the axis of the pivot
24
and of the longitudinal central axis of the support
1
to which it is perpendicular therefore constitutes the reference point of the attachment member
2
. The axis of the pivot
24
can therefore be oriented in any direction in the plane parallel to the face of the flange external to the head
12
at a distance equal to that between the reference point and that face, and the attachment finger
23
can be pivoted in a vertical plane through an angle of at least 180° if its outside shape is chosen accordingly. The attachment finger
23
has a hook for attaching Invar wires near its end opposite its articulation to the pivot
24
.
The assembly member
3
takes the form of a ring forming a nut whose inside screwthread
31
cooperates with the outside screwthread
14
of the support
1
. It has an inside surface
32
for clamping the flange against the head
12
, with the lateral surface of the flange pressed against the frustoconical seat
16
, and the outside surface of the ring can be knurled to facilitate tightening it.
When the respective attachment members of two devices as described above are connected to each other by Invar wires and an adjustment member, and the wires and the adjustment member have been aligned with the attachment finger
23
, the distance whose evolution is to be checked is that between the longitudinal axes of the respective two pivots
24
of the two devices.
Repetitive measurements using the above equipment are time-consuming and costly and it is desirable to use simpler and faster means of studying the evolution of the same structures.
However, measurements effected until now by other techniques, in particular optical techniques, supply results that are comparable with those obtained using the equipment just described only after lengthy and difficult (or even impossible
Benoit Alain
Brouard Christophe
Delmas Jean-François
Duranthon Jean-Paul
Guadalupe Yaritza
Gutierrez Diego
Regie Autonome des Transports Parisiens
Wenderoth , Lind & Ponack, L.L.P.
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