JPS623477B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a zero return device for a scale wheel used in a planimeter or the like.

Conventionally, planimeters are usually equipped with a zero return device that returns the lower scale wheel and the upper scale wheel to zero at the same time using one operating lever, but this zero return device has a zero return cam coaxially fixed to each scale wheel. Since the two dials are pressed and rotated by engagement portions provided on the operating lever to return to the zero point, it is extremely difficult to adjust the scale wheels so that they return to the zero point position at the same time, and this adjustment requires a large amount of man-hours. There are some drawbacks.

In order to avoid this, if one of the two engaging parts provided on the operating lever is supported by a spring on the operating lever, the space within the operating lever and the housing in which it is installed is small. If the support spring of the engaging portion and the return spring of the operating lever do not interfere with each other, the spring elasticity will not only decrease and the operation will be uncertain, but also the structure will become complicated and the cost will increase. Become.

The present invention deals with this problem by inserting a friction joint into the interlocking mechanism between the lower scale wheel and the upper scale wheel, each of which has a zero return cam coaxially fixed to the other. In a zero return device for a scale wheel in which an operating lever is pivotally connected to a housing, an auxiliary lever including an engaging portion for the other zero return cam is pivoted to the operating lever so as to be able to swing freely within a certain range, and the auxiliary lever A spring is installed between the auxiliary lever and the housing so as to always urge the engaging portion of the auxiliary lever to rotate toward the other zero return cam and to always urge the operating lever to rotate toward the non-operating position. , characterized in that the two engaging parts are arranged in relation to each other so that the zero point return of the corresponding zero return cam by the auxiliary lever side engaging part precedes the zero point return of the corresponding zero return cam by the operating lever side engaging part. do.

The figure shows one embodiment of the present invention, in which 1 is a cylindrical zero return cam fixed coaxially to a rotating shaft 3 that is integrated with a lower scale wheel 2, and 4 is the lower end of a hollow rotating shaft 6 that is integrated with an upper scale wheel 5. A heart-shaped zero return cam is coaxially fixed to the cam, and 7 indicates an operating lever whose terminal is pivoted 9 to a housing 8. The operating lever 7 is integrally provided with an engagement portion 10 for the heart-shaped zero return cam 4. It is being

Reference numeral 11 denotes an auxiliary lever having a pin-shaped engagement portion 12 for the zero return cam 1 implanted at one end and a spring mounting pin 13 implanted at the other end. The pin-like engagement portion 12 and spring attachment pin 13 are loosely fitted through holes 15 and 16 formed in the operating lever 7 and protrude upward. Therefore, the auxiliary lever 11 is centered around the pivot shaft 14, and the pin-shaped engaging portion 12 and the hole 15 are connected to each other.
It is swingable relative to the operation lever 7 by the amount of play between the spring mounting pin 13 and the hole 16.

Reference numeral 17 denotes a tension spring tensioned between the spring mounting pin 13 and a pin 18 implanted on the housing 8 side.
2 is constantly urged to rotate toward the cam surface 19 of the zero return cam 1, and the pin-shaped engaging portion engages with the hole edge of the hole 15.
Alternatively, the operating lever 7 is always urged to rotate to the non-operating position shown in FIG. 1 through the engagement between the spring mounting pin 13 and the edge of the hole 16.

The casing 8 is made up of a base 20 that supports the rotating shafts 3 and 6 and the operating lever 7, and a lid 22 that fixes a measuring rod 21 so as to be slidable and adjustable, which are connected together with a set screw. A seat plate 24 is fixed to the base 20 with two setscrews 23 so as to be able to be finely adjusted in the front, back, left and right directions, and a hollow rotating shaft 6 is fitted onto a shaft 25 (FIG. 3) that is fixed upright to the seat plate 24. A worm gear 28 that meshes with the worm 27 of the rotating shaft 3 is fixed to the lower end of the hollow transmission shaft 26 fitted on the outside of the hollow rotating shaft 6.
8 and the zero return cam 4 at the lower end of the hollow rotating shaft 6, a compression spring 29 is installed to bring the flange portion at the upper end of the hollow rotating shaft into frictional contact with the upper scale wheel 5.
6 are interlocked and connected, and a friction joint is provided in the interlocking mechanism.

In the figure, 30 is a pointer fixed to the upper end of the shaft 25, and 31
is an index engraving member facing the lower scale wheel 2, 32;
Reference numeral 33 indicates pivot bearings at both ends of the rotating shaft 3 attached to the base 20, 34 indicates a glass window attached to the lid 22, and the outer end of the pivot bearing 33 is attached to the index engraving member 3.
1 and a seat plate 36 whose both ends are fastened to the base 20 with set screws 35, so that the distance between the index engraving member 31 and the lower scale wheel 2 can be adjusted.

To return the scale wheels 2 and 5 to zero in the above configuration, rotate the operating lever 7 clockwise about the pivot shaft 9 from the non-operating position shown in FIG.
The auxiliary lever 11 is attached to the pivot shaft 1 by the elasticity of the spring 17.
4, the pin-shaped engaging portion 12 rotates along with the operation lever 7 while being pressed and held toward the zero-cam side hole edge of the hole 15, and the pin The shaped engaging portion 12 engages with the cam surface 19 to return the zero return cam 1 or scale wheel 2 to the zero point.

In this state, the operating lever 7 is in the position shown by the chain line in FIG. 3, and the pin-shaped engaging portion 12 is engaged with the V-shaped recess at the left end of the cam surface 19. When the operating lever 7 is further rotated from this state, the pin-shaped engaging portion 1
2 of the auxiliary lever 11 engages with the left end of the cam surface 19. Since its pivot shaft 14 rotates along with the operating lever, the pin-shaped engaging portion 12 and the spring mounting pin 13 are respectively connected to the hole 15. , 16, while
The engaging portion 10 of the operating lever 7 engages with the cam surface around the zero return cam 4 to return the zero return cam or scale wheel 5 to the zero point. When the user releases the operating lever 7, the operating lever automatically returns to the non-operating position due to the elasticity of the spring 17.

In the conventional zero return device in which the operating lever is pivoted to the housing, the pin-shaped engagement part moves in an arc, so
In order to accurately return the corresponding zero return cam to the zero point, the zero point side end of the zero return cam had to be made into a V-shaped recess, making it extremely difficult to adjust both scale wheels to return to the zero point at the same time. According to the present invention, this adjustment can be made for each scale wheel, making it really easy to adjust.Furthermore, since it can be operated accurately just by adding one auxiliary lever, it is easy to assemble and is extremely effective in terms of cost. It is.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional plan view when not in operation, FIG. 2 is a sectional view taken along line XX in FIG. 1, and FIG. 3 is a plan view of the main parts when in operation. 1, 4...Return cam, 2...Lower scale wheel, 5...
...Upper scale wheel, 7...Operation lever, 8...Housing,
9... Pivoting shaft, 10... Engaging portion, 11... Auxiliary lever, 12... Pin-shaped engaging portion, 13... Spring mounting pin, 14... Pivoting shaft, 15, 16... Hole,
17...Tension spring.

Claims (1)

[Claims] 1. A friction joint is inserted into the interlocking mechanism between the lower scale wheel and the upper scale wheel, each of which has a zero return cam fixed on the same axis, and an operating lever with an engaging portion for one of the zero return cams is pivoted to the casing. In the zero return device for a scale wheel, an auxiliary lever having an engaging portion for the other zero return cam is pivotally attached to the operating lever so as to be swingable within a certain range, and the engaging portion of the auxiliary lever is connected to the other zero return cam. A spring is installed between the auxiliary lever and the housing so as to always force the rotation toward the cam and the operating lever to the non-operating position, and a corresponding return is applied by the engaging part on the auxiliary lever side. 1. A zero return device for a scale wheel, characterized in that both engagement parts are arranged in relation to each other so that the return of the zero cam to zero point precedes the return to zero of the corresponding zero return cam by the engagement part on the operating lever side.