Resetting mechanism for electronic theodolite

Abstract: The resetting mechanism for electronic theodolite of the present invention comprises a horizontal shaft (2) for vertically turning telescope (1), first cam (3) provided at one end of the horizontal shaft, a lock lever (4) limited by the first cam, a second cam (5) locked or released by the lock lever, a lock member (6) operated by the second cam, a lock concave (1a) provided on the telescope to be locked by a lock member when the telescope is turned to right down lock position, and an encoder set to a zero position when the telescope is turned to a right down lock position.

Description: 1. Field of the Invention The present invention relates to an electronic theodolite, more particularly to a resetting mechanism thereof. 2. Background Information To set a reference position on a vertical plane of a telescope of usual electronic the odolites, in general, the telescope has to be directed just above once. After this, it is turned in a desired direction before an elevation angle OR depression angle is measured. A device for setting a theodolite is, for example, disclosed in GB-A-1 344 287. However, it is a problem that such an apparatus is hard to reset and needs a high skill. SUMMARY OF THE INVENTION To solve the above-mentioned problem, an object of the present invention is to provide an electronic theodolite that zero setting is already made at start of use. The resetting mechanism for electronic theodolite according to the present invention comprises a horizontal shaft to vertically turn a telescope, first cam provided at one end of the horizontal shaft, a lock lever limited by the first cam, a second cam locked or released by the lock lever, a lock member operated by the second cam, and an encoder set to a zero position when the telescope is turned to a right down lock position. The telescope has a lock concave which is locked at the zero position by the lock member, and the first cam has a projection portion which presses the lock lever when the telescope is turned right down. The second cam has a step which is locked by the lock lever when the lock lever is operated by the first cam, a cam portion which presses the lock member at the same time, an interlocking mechanism which turns on or off a power switch of the whole theodolite apparatus and a handle. The lock member has a projection portion which is inserted into the lock concave of the telescope when it is pressed by the second cam. Other objects and advantages of the invention will become more apparent from the following portion of this specification and from the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig.1 is a partially cross-sectioned front view of the electronic theodolite according to the present invention, with it being locked. Fig. 2 is a partially cross-sectioned front view of the electronic theodolite according to the present invention, with a telescope being held horizontally in use. Fig. 3 is a side view of the electronic theodolite according to the present invention, with a cover for the telescope and upper portion being omitted wherein the dotted line illustrates the housed position and the solid line illustrates the activated position. DESCRIPTION OF THE PREFERRED EMBODIMENTS A front side of a main body of the theodolite according to the present invention is U-shaped. The U-shaped main body has horizontal shaft 2 held at upper portions of two sides thereof. Telescope 1 is held by horizontal shaft 2 to be able to turn in a vertical plane. The main body is connected with a front panel thereunder. The front panel has function switches and indicators which are arranged thereon, the detailed description of which is omitted here. The main body has first cam 3 provided on one inside wall thereof. First cam 3 is fixed at an end of horizontal shaft 2. Turning shaft 7 is held obliquely below first cam 3. L-shaped lock lever 4 is turnably held by turning shaft 7. An upper end of lock lever 4 is positioned so that it can be pressed by projection 3a of first cam 3 and retreats. A lower end of lock lever 4 is selectively positioned so that lock lever 4 can lock or release second cam 5 which will be described below, however, the lower end is biased to lock second cam 5 by spring 8. Second cam 5 has a horizontal center shaft extending parallel to the side wall of the main body. Also, second cam 5 has cam portions 5b at both ends thereof to press or release lock member 6 which will be described below, and cam sides 5d. Front cam portion 5b has step 5a so that it can be locked by the lower end of lock lever 4. Second cam 5 also has handle 5c provided outside of the front side of the main body. Lock member 6 has fixing portion 6a to mount it on the main body, spring piece 6b a top of which is fixed on fixing portion 6a, and projection portion 6c provided at a center of spring piece 6b to project in the inner space defined by the U-shaped main body. Spring piece 6b has a width so that it can operate on both cam portions 5b of second cam 5. The projecting end of projection portion 6c is tapered a little so that it can be easily inserted into lock concave 1a of telescope 1 provided at a position corresponding thereto when projection portion 6c projects. When projection portion 6c is completely be inserted into lock concave 1a, telescope 1 can be held at a zero position and a reset error is substantially zero. Also, lock member 6 is formed so that it can turn a power switch on or off together with an interlocking mechanism (not shown) of second cam 5, simultaneous with the operation of lock member 6. In turn, the following describes the operation of the resetting mechanism according to the present invention. Fig. 1 shows that the theodolite is in a housed state. If the theodolite is turned 180 degrees from the housed state, then it is set at a reference position. Therefore when the theodolite is in the housed state, it should indicate 180 degrees. In the housed state, projection portion 3a of first cam 3 fixed on horizontal shaft 2 of telescope 1 is at a position where it presses the upper end of lock lever 4. The lower end of lock lever 4, therefore, is out of step 5a of second cam 5 and second cam 5 is fully turned counterclockwise. In this state, the power switch is off and lock member 6 is pressed by cam portion 5b and the end of projection portion 6c is inserted into lock concave 1a of telescope 1. Therefore telescope 1 is fixed right down. An encoder not shown is set to zero position by lock member 6. If handle 5c of second cam 5 is turned clockwise from the housed state around 90 degrees, the power is turned on. At the same time, cam portion 5b releases spring piece 6b of lock member 6 and spring piece 6b presses cam side 5d. This limits turning of second cam 5. The theodolite enters a measurement ready state. At that position, projection portion 6c of lock member 6 is fully receded inside of the main body and come out of lock recess 1a of telescope 1. Telescope 1 can be freely turned. At the same time, second cam 5 can be locked by lock lever 4, however it should be noted that the locking is not done yet in this state. When telescope 1 is directed in an object direction, the encoder which was reset in the locked position described above, provides an angle signal to an operating means which converts the angle to an angle from just right overhead to the object direction and the indicator shows the converted angle. At the same time, projection portion 3a of first cam 3 fixed on horizontal shaft 2 of telescope 1 releases the top end of lock lever 4. The lower end of lock lever 4 locks step 5a of second cam 5 utilizing a restoring force of spring 8. To house the theodolite after measurement, telescope 1 is turned downward, and projection portion 3a of first cam 3 then presses the top of lock lever 4 to lift the lower end of lock lever 4 against the restoring force of spring 8, thereby releasing second cam 5. In turn, if second cam 5 is turned counterclockwise, the power switch is turned off. At the same time, cam portion 5b presses spring piece 6b of lock member 6 to protrude projection piece 6c. Projection piece 6c is inserted into lock concave 1a of telescope 1, thereby holding telescope 1 right down. Even if the telescope is deviated a little, it can be corrected and set right down by the end of projection piece 6c is tapered in the state. As described so far, telescope 1 can be reset whenever it is housed after measurement. The telescope needs no resetting work at the start-up. While the principles of the invention have been described above in connection with specific embodiments, and particular modifications thereof, it is to be clearly understood that this description is given only by way of example and not as a limitation on the scope of the invention.

Claims: A resetting mechanism for an electronic theodolite, comprising horizontal shaft means (2) for vertically rotating a telescope (1); a first cam (3) provided at one end of the horizontal shaft; a lock lever (4), the first cam (3) limiting the position of the lock lever (4); a second cam (5) locked or released by the lock lever (4); a lock member (6) operated by the second cam (5); means setting the electronic theodolite to a zero position when the telescope (1) is rotated to a fully down locked position; the telescope (1) having a concave locking recess (1a) for locking it in a zero position by the lock member (6), the first cam (3) having a projection portion (3a) contoured to press the lock lever (4) when the telescope (1) is turned fully down; the second cam (5) having a stepped portion (5a) locked by the lock lever (4) when the lock lever (4) is not pressed by the first cam (3), a cam portion (5b) pressing the lock member (6) when said second cam (5) is rotated, and means (6c) for turning on or off a power switch of the electronic theodolite in accordance with a rotation of said second cam (5); the lock member (6) having a projection piece (6c) engaging the concave lock recess (1a) of the telescope (1) when the lock member (6) is pressed by the second cam (5).

Inventors: KUBO AKIO, KUBO, AKIO
Applicants: KUBO AKIO, KUBO, AKIO
Application year: 1993
Main classification: G01C1
IPC codes: G01C1