JPS6221938Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE PRESENT DISCLOSURE The present invention relates to a zero adjustment mechanism.
More specifically, the present invention relates to a zero adjustment mechanism used in, for example, a measuring instrument, for adjusting the indicated position of a pointer so that it coincides with the zero position of a scale plate when the input is zero.

An object of the present invention is to provide a zero adjustment mechanism that can prevent zero shifts caused by the zero adjustment mechanism.

FIG. 1 shows one embodiment of the present invention, and an example in which the present invention device is used in a force balance type instrument using a force motor will be explained.

In the figure, 1 is the base of the meter, 2 is the input current
This is a force motor that converts Iin into force in the direction of the arrow in the figure. 3 is a beam supported by a fulcrum 4 in the middle. 5 is a feedback bellow provided between the base 1 and the beam 3. 6 is beam 3
The nozzle arranged opposite to the beam 3 constitutes a nozzle flapper mechanism, and its back pressure is supplied to the bellows 5 and transmitted as an output signal. 7
is a zero adjustment mechanism disposed between the beam 3 and the base 1, as shown in FIG. In FIG. 2, 71 is a zero adjustment spring whose one end is fixed to the beam 3. 72 is a plate-shaped spring terminal attached to the other end of the zero adjustment spring 71. 73 is a drive shaft attached to the base 1. The drive shaft 73 has a threaded portion 731 provided on the distal end side that is screwed into a threaded hole 721 provided on one end side of the terminal fitting 72.
By rotating the drive shaft 73, the terminal tool 72
is displaced in the axial direction of the zero adjustment spring 71.
A guide pin 74 has one end fixed to the base 1 and the other end inserted into a hole 722 provided in the terminal fitting 72. Reference numeral 75 denotes a looseness removing spring provided between the terminal tool 72 and the base 1. The rattling spring 75 strongly presses the terminal tool 72 in the axial direction of the zero adjustment spring 71, and is designed to apply a force stronger than the zero adjustment spring 71 to the terminal tool 72.

In the above configuration, the force motor 2 and the bellows 5 to which the back pressure of the nozzle 6 is applied are balanced, and a pneumatic output Pout corresponding to the input current Iin is output. In this case, when the drive shaft 73 of the zero adjustment mechanism 7 is rotated, the spring terminal tool 71 is displaced in the axial direction of the zero adjustment spring 71. As a result, the amount of displacement of the zero adjustment spring 71 changes, so the force applied to the beam 3 changes, allowing zero adjustment of the instrument.

In this case, the position of the terminal fitting 72 is held by the screw hole 7
21 and the threaded surface of the threaded portion 731 of the drive shaft 73. This frictional force is easily affected by external disturbances such as changes over time, temperature changes, and shocks, and this effect appears as a zero shift in the output. For this reason, it is desirable that the frictional force be strong.

In the conventional device, only the zero adjustment spring 71 was used, and the backlash removing spring 75 was not used. Therefore, the zero adjustment spring 71 not only adjusts the zero position of the instrument, but also serves as a source of frictional force on the threaded surface.

In such a device, the frictional force changes depending on the amount of zero position adjustment, and the frictional force is determined by the amount of adjustment. In particular, when the zero adjustment spring 71 is used at a position close to the free length state of the zero adjustment spring 71, the frictional force becomes minute. Furthermore, also in the case of force-balanced instruments, it is desirable that the force exerted on the beam 3 by the zeroing spring be close to zero. Therefore, zero shift is even more likely to occur.

In the present invention, a spring stronger than the zero adjustment spring 71 is provided opposite to the zero adjustment spring 71.
A backlash removing spring 75 is provided parallel to the drive shaft 73 so as to always apply a constant strong frictional force to the threaded surface. Since the looseness removing spring 75 is provided separately in parallel with the zero adjustment spring 71, there is no restriction imposed on performing the zero adjustment function, and the spring 75 can be designed to have any strength.

As a result, it is possible to prevent the zero shift caused by the disturbance force.

In the above-mentioned embodiments, the looseness removing spring was described as one that applies a compressive force to the terminal tool 72, but it goes without saying that it may be a spring that applies a tensile force.

As explained above, according to the present invention, it is possible to realize a zero adjustment mechanism that can prevent zero shift caused by the zero adjustment mechanism.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention, in which the device of the present invention is used in a force balance type instrument using a force motor, and FIG. 2 is an explanatory diagram of the main part of FIG. 1. 1...Base, 2...Force motor, 3...
Beam, 4... Fulcrum, 5... Feedback bellow, 6... Nozzle, 7... Zero adjustment mechanism, 71...
... Zero adjustment spring, 72 ... Spring terminal fitting, 721 ... Screw hole, 722 ... Hole, 73 ...
...Drive shaft, 731...Threaded portion, 74...Guide pin, 75...Backlash removal spring.

Claims (1)

[Scope of utility model registration request] a zero adjustment spring having one end fixed to the zero adjustment mechanism; a spring terminal fitting having one end attached to the other end of the zero adjustment spring; and a screw for displacing one end of the terminal fitting in the axial direction of the zero adjustment spring. A zero adjustment mechanism comprising: a guide pin provided parallel to the screw mechanism at the other end of the terminal tool and engaged at one end; and a zero adjustment spring wound around the guide pin and attached to the terminal tool. A zero adjustment mechanism characterized by comprising a backlash removing spring that applies a force greater than the zero adjustment spring in the axial direction.