The invention relates to an adaptor for mounting one instrument on another instrument so that both are pivotably movable together about a horizontal axis.
Often it is desirable to be able to mount one instrument atop another so that both can be used simultaneously. For example, electronic distance measuring devices are instruments which transmit a beam of light to a distant object, receive the reflected beam, and determine and display the distance to the object. Such devices are commonly used for surveying and it is convenient to use them in conjunction with conventional otpical devices such as telescopes and theodolites. Preferably, the electronic distance measuring device is mounted atop the optical instrument for pivotable movement therewith.
An instrument such as an electronic distance measuring device cannot simply be attached to a theodolite or the like because the balance of the two instruments together will be unsatisfactory. An adaptor must be used to attach the upper instrument to both the lower instrument and the stand and to provide compensating forces as the instruments are tilted.
One type of adaptor now in use for such systems utilizes three downwardly extending male members attached to the upper instrument which must be received in corresponding female portions in a lower member and engage springs which are horizontally compressed to produce compensating forces as the two instruments pivot together about a horizontal axis. The device must be locked in place and is unwieldy to assemble. In addition, some torque is produced by the device, and it is difficult to find springs which will compensate exactly for the forces produced by the pivoting motion of the upper instrument.
The present invention relates to an improved adaptor of the type which utilizes at least one and preferably two supporting members adapted to be coupled to the stand which supports the lower instrument for pivotable movement. Each of these supporting members engages a cam surface of the adaptor which is attached to the upper instrument. A compressible spring engages each of the support members and produces a force which varies as the support members engage different portions of the cam surface and move vertically in accordance therewith. No torque is produced and the supporting members ride on the cam surfaces rather than engage female or other portions thereof. The contour can be linear or nonlinear and can be specifically designed to exactly counteract the forces produced by any given upper instrument as it moves with the lower instrument about a horizontal axis.
Other objects and purposes of the invention will be clear from the following detailed description of the drawings.