JPH0649400B2 - Scale balance device for universal parallel ruler - Google Patents

Description

The present invention relates to a balance device for a scale in a universal parallel ruler.

[Conventional technology]

Conventionally, the spring is applied to the eccentric position of the scale mounting plate itself or the rotating body that rotates in conjunction with the scale mounting plate,
This spring force causes the scale mounting plate or the rotating body to generate a rotating torque in a direction opposite to the rotating torque in the gravitational direction due to the weight of the scale or the like to balance the scale.

[Problems to be solved by the invention]

The rotational torque T1 due to the weight of the scale of the scale mounting plate to which the scale is connected when the drawing plate is inclined is T1 = F1 × R1.

Here, F1 is a downward load due to the weight of the scale acting on the center of gravity G of the scale mounting plate, and R1 is the radius of the scale mounting plate as a rotational torque generating element.

This radius R1 changes in a sine curve as the scale mounting plate rotates. However, the above F1 is constant.

Rotational torque T of the above scale mounting plate due to constant load F1
When the rotational torque that cancels out 1 is applied to the scale mounting plate, the scale mounting plate can be perfectly balanced. However, according to the conventional method, the spring is bent and the spring force is changed as the scale mounting plate is rotated. If the spring force changes, the scale mounting plate cannot be perfectly balanced. That is, the force F1 acting on the center of gravity G of the scale mounting plate due to the weight of the scale or the like is constant regardless of the rotation of the scale mounting plate. Therefore, unless the spring force is also constant, the weight of the scale of the scale mounting plate is constant. It is not possible to cancel out the rotation moment due to and the rotation moment due to the spring force. However, when the spring force is constant, the scale cannot be perfectly balanced unless the direction of action of the spring on the scale mounting plate or the rotating body is always constant. However, the action direction of the spring cannot be constant unless the position of the spring is infinitely far from the scale mounting plate or the rotating body. That is, even if the spring force applied to the scale mounting plate or the rotating body is constant, the scale cannot be precisely balanced.

An object of the present invention is to solve the above problems and achieve a highly accurate balance of the scale.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention is a head 1 that is movable to an arbitrary position while maintaining a predetermined orientation on a drawing board 2.
6, a main shaft 22 rotatably supported by a support substrate 18 of the head 16, a handle 26 fixed to an upper part of the main shaft 22, a scale mounting plate 28 fixed to a lower part of the main shaft 22, In a universal parallel ruler including scales 30 and 32 attached to the scale attachment plate 28, a rotary body 38 that is rotatable in association with the scales 30 and 32.
A cam pulley 54 having a substantially frustoconical cam portion rotatably supported by the supporting substrate 18 of the head and having a rope guide groove formed spirally in the cam portion; and the cam pulley 54.
Is wound around the rope guide groove of the cam pulley 54 a plurality of times, and one end is connected to the expanded side of the cam pulley 54 and the other end is the rotating body 3.
8 of the rope-shaped member 58 connected to the eccentric portion, and the winding end S of the rope-shaped member 58 expands as the force of the spring 56 increases as the cam pulley 54 rotates. The rope-shaped member 58 is configured to move in the radial direction, and the end of the rope-shaped member 58 is set at a position infinitely distant from the rotary body 38 on the axis M passing through the center of the rotary body 38 and the center of the cam pulley 54. The angle formed by the actual pulling direction F2 of the rope-shaped member 58 with respect to the rotary body 38 with respect to the pulling direction F1 of the rope-shaped member 58 with respect to the rotary body 38 is set to θ. The rotating body 3 when it is assumed that the pulling direction of 58 with respect to the rotating body 38 does not change.
The rope-like member 58 for balancing with the rotational force of 8
If the balance pulling force is F, then the rope-like member 5
The balance pulling force F ′ on the rotating body 38 of No. 8 is F ′ =
The diameter of the cam pulley 54 is set so as to be F / cos θ.

[Action]

The head 16 is stopped on the inclined drawing board 2, and the scale 30,
When 32 is set in a free rotation state around the main shaft 22,
Due to the weight of the scales 30, 32, etc., a rotational torque in the direction of gravity is generated in the rotating body 38, and the scales 30, 32 tend to rotate in the falling direction along the drawing board 2. On the other hand, the tension force of the rope-shaped member 58 wound around the cam pulley 54, which is urged in the rotation direction by the spring 56, acts on the rotating body 38. This pulling force F ′ is applied to the rotating body 3 of the rope-like member 58.
When the ideal tensile force assumed when the tensile direction with respect to 8 does not change is F and the angle formed by the rope-shaped member 58 with respect to the ideal constant tensile direction is θ, F ′ = F /
cos θ. The rotational torque of the rotating body 38 due to the pulling force F ′ is precisely offset with the rotating torque of the rotating body 38 in the direction of gravity, so that the scales 30 and 32 are precisely balanced.

Hereinafter, the configuration of the present invention will be described in detail with reference to the embodiments shown in the accompanying drawings.

〔Example〕

Reference numeral 2 is a drawing plate, which is fixed to a support frame of a tiltable drafting table so that it can be fixed at a desired inclination angle between horizontal and vertical. Reference numeral 4 denotes a horizontal rail arranged on the upper side of the drawing board 2, to which a horizontal cursor 6 is movably attached. An upper end of a vertical rail 8 is connected to the horizontal cursor 6. The lower end of the vertical rail 8 is movably placed on the drawing board 2 via the tail roller. Reference numeral 12 is a vertical cursor movably attached to the vertical rail 8, to which a supporting substrate 18 of the head 16 is connected via a known double hinge mechanism 14. The support substrate 18
A tubular double shaft 20 is fixed to the tube portion of the device by a nut. Reference numeral 22 denotes a tubular main shaft, the outer peripheral surface of which is rotatably fitted into the inner peripheral surface of the double shaft 20. A mounting plate 24 is fixed to the upper portion of the main shaft 22 by a nut, and a handle 26 is fixed to the mounting plate 24. A scale mounting plate 28 is fixed to the lower end flange of the main shaft 22, and scales 30 and 32 are fixed to the scale mounting plate 28. Reference numeral 34 denotes a pipe body fixed to the mounting plate 24, and a first rotating body 36 is fixed to the outer peripheral surface of the pipe body 34 with a screw so that the rotation angle can be adjusted with respect to the pipe body 34. A gear 37 is formed on the lower pulley portion of the rotating body 36. Reference numeral 38 denotes a second rotating body, which is rotatably supported on the support substrate 18 by a shaft 40. A timing belt 48 is stretched between the teeth 45 formed on the pulley portion of the second rotating body 38 and the teeth 37 of the first rotating body 36. Reference numeral 42 denotes a screw shaft diametrically mounted on the rotating body 38, with which a molding 44 is screwed, and a piece member 46 is fitted in the recessed portion of the molding 44. Piece member 46
Is supported by a linear guide along the screw shaft 42 of the rotating body 38, and the piece member 46 is interlocked with the molding 44 to move the piece member 46.
Is configured to move along. The piece member 4
The metal fitting terminal 58 a of the rope-shaped member 58 is fitted to the cable 6. A belt guide pulley 50 is rotatably provided on the bracket 52. Reference numeral 54 designates the shaft 5 on the support substrate
5 is a cam pulley having a truncated cone-shaped cam portion rotatably supported by 5, and a spring spring 56 is arranged on the outer peripheral surface of the outer peripheral portion of the cylindrical portion of the cam pulley 54. The spring 56 is engaged with the cylindrical portion, and the other end of the spring 56 is engaged with the tube wall of the tube portion 18 a formed on the support substrate 18. A rope guide groove is spirally formed on the cam of the cam pulley 54, and a rope-shaped member 58 is wound along the rope groove. One end of the rope-shaped member 58 is locked to the bottom portion of the cam pulley 54 on the enlarged diameter side by a screw. As shown in FIG. 7, the distance L between the spring 56 and the rotating body 38 is infinite, and the pulling direction of the rope-shaped member 58 with respect to the rotating body 38 does not change with the rotation of the rotating body 38 and is constant. If it is assumed that the tensile force F of the rope-shaped member 58 acting on the rotating body 38 is constant, the balance rotating torque acting on the rotating body 38 is the gravity direction rotating torque due to the weight of the scales 30, 32 and the like. And completely offset. However, the spring 56 sequentially becomes stronger as the angular position of the horizontal scale 30 changes from 90 degrees to zero degrees to -90 degrees. Since the torque T of the cam pulley 54 is generated by the spring 56, it increases as the angular position of the scale 30 changes from 90 degrees to zero degrees to -90 degrees, as shown in FIG. On the other hand, since the force F for pulling the piece member 46 by the rope-shaped member 58 should be constant, if the distance from the center of the cam pulley 54 to the contact point of the rope-shaped member 58 is l, T = lF∴l = T / If the diameter of the cam pulley 54 is configured so that 1 changes in proportion to the change of the spring 56, even if the spring 56 increases, the above l increases in proportion to this and the rope-like member 5
The tensile force F of 8 can be made constant, and the scale 30,
32 can be balanced. As described above, by changing the diameter of the cam pulley 54, the scale 30,
Should be able to achieve a perfect balance of 32,
The above-mentioned principle is premised on L = ∞, and since L = ∞ cannot be actually created, correction is required for that.

As shown in FIG. 9, when the end of the rope-shaped member 58 is set at a position infinitely separated from the rotating body 38 on the axis M passing through the center of the rotating body 38 and the center of the cam pulley 54. The angle formed by the actual pulling direction F2 of the rope-shaped member 58 with respect to the rotary body 38 with respect to the assumed pulling direction F1 of the rope-shaped member 58 with respect to the rotary body 38 is θ. Rotating body 3
If the balance pulling force of the rope-shaped member 58 for balancing with the rotating force of the rotating body 38 on the assumption that the pulling direction with respect to 8 does not change is F, then the actual rotating force of the rotating body 38 is Balancing rope member 5
The tensile force F ′ of 8 is F ′ = F / cos θ. That is,
As shown in FIG. 10, the distance l1 between the center of the cam pulley 54 and the contact point between the rope-shaped member 58 and the characteristic of l at L = ∞ is corrected in consideration of the change in θ, and F ′ =
It is set so that F / cos θ holds.

11. FIG. 11 is an explanatory diagram showing how the above l and l1 change when the cam pulley 54 is viewed from above.

Next, the operation of this embodiment will be described.

When the horizontal scale 30 is substantially parallel to the horizontal rail 4,
The rotation torque centered on the main shaft 22 due to the weight of the scales 30, 32, etc. of the scale mounting plate 28 is maximized. At this time, the rotation angle of the second rotating body 38 is adjusted as shown in FIG. 6 so that the radius of the second rotating body 38 as the rotational torque generating element by the spring 56 is maximized. . At this time, the cam pulley 5 of the rope-shaped member 58
The winding end S on the feeding side in No. 4 is set to be located in the middle of the cam portion of the cam pulley 54. Drawing board 2
If the scale is inclined, the weight of the scales 30, 32, the scale mounting plate 28, etc. causes the spindle 2
A rotation moment is generated in the direction of rotation of the hour hand in FIG. The rotation moment of the scale mounting plate 28 is transmitted to the second rotating body 38 via the first rotating body 36 and the timing belt 48. On the other hand, a tension is generated in the rope-shaped member 58 by the rotation moment of the cam pulley 54 by the mainspring 56, and the tension of the rope-shaped member 58 causes the second rotor 38 to cancel the rotation moment due to the weight of the scale 30 or the like. The rotation moment of is given. As a result, the scale mounting plate 28 holds the stationary state at an arbitrary rotation angle.

Next, the operation of adjusting the distance of the rope connecting point with respect to the rotation center of the second rotating body 38 will be described.

When the molding 44 is rotated, the molding 44 moves along the screw shaft 42, and in conjunction with the molding 44, the piece member 46 moves on the rotating body 34 in the radial direction. By the movement of the piece member 46 along the screw shaft 42, the distance of the connection point of the rope-shaped member 58 with respect to the rotation center of the rotating body 38 changes.
When the inclination angle of the drawing board 2 is changed, the value of the load W applied to the scale mounting plate 28 due to the weight of the scales 30 and 32 or the like changes accordingly. Therefore, when the inclination angle of the drawing board 2 is changed, the eccentric amount of the rope-shaped member 58 with respect to the rotating body 38 is adjusted by rotating and adjusting the molding 44 to rotate the second rotating body 38 in the balance direction. Adjust the amount of torque.

In the practice of the present invention, the spring that applies the rotational force to the cam pulley 54 is not particularly limited to the mainspring, and the rotating body that applies the tension of the rope-shaped member 58 is
The second rotating body 38 is not limited to a particular one, and may be configured to apply a tension for balancing the rope-shaped member 58 to the rotating body that interlocks with the scales 30, 32 such as the scale mounting plate 28 and the handle 26. Incidentally, in the universal parallel ruler, the scale can be rotated outside the range of -90 degrees to 90 degrees, but the operator does not rotate and draw the scale in that way. Use range of scale is -90
The range is from 90 degrees to 90 degrees. Further, when the scale is close to 90 degrees or −90 degrees, the pulling directions F2 and F1 are close to parallel, so θ is close to zero, F ′ is close to F, and l
Decreases or increases.

It is shown in FIG. 10 that F ′ = F / cos θ becomes almost the same as F ′ = F near 90 ° or −90 ° where θ approaches zero.

〔effect〕

As described above, according to the present invention, a spring force for imparting a rotational moment to a rotating body in which the weight of a scale or the like acts as a rotating moment in a direction of canceling the rotating moment is applied to the rotating body by changing the diameter of the cam pulley. Since it adjusts automatically according to the change of the acting direction of force,
There is the effect that the scale can be precisely balanced.

[Brief description of drawings]

1 is a sectional view, FIG. 2 is a sectional view, FIG. 3 is a sectional view, FIG. 4 is a plan view, FIG. 5 is a plan view, FIG. 6 is an explanatory view, and FIG.
FIG. 8 is an explanatory diagram, FIG. 8 is an explanatory diagram, FIG. 9 is an explanatory diagram, and FIG.
The figure is an explanatory diagram, and FIG. 11 is an explanatory diagram. 2 ... Drawing board, 4 ... Horizontal rail, 6 ... Horizontal cursor, 8 ...
… Vertical rail, 12 …… Vertical cursor, 14 …… Double hinge mechanism, 16 …… Head, 18 …… Support substrate, 20 ……
Multi-axis, 22 ... Spindle, 24 ... Mounting plate, 26 ... Handle, 28 ... Scale mounting plate, 30, 32 ... Scale, 34 ... Tube, 36 ... First rotating body, 37 ... …
Teeth, 38 ... Second rotary body, 45 ... Tooth, 48 ... Timing belt, 44 ... Mole, 42 ... Screw shaft, 46
...... Piece member, 54 ...... cam pulley, 56 ...... spring spring, 58 ・ ・ ・ rope-shaped member

Claims (1)

[Claims] 1. A head 16 movable to an arbitrary position while maintaining a predetermined orientation on a drawing board 2, a main shaft 22 rotatably supported by a supporting substrate 18 of the head 16, and the main shaft 22. Handle 26 fixed to the upper part of the main shaft 22
In a universal parallel ruler including a scale mounting plate 28 fixed to the lower part of the scale and scales 30 and 32 mounted to the scale mounting plate 28, a rotatable body 38 that is rotatable in conjunction with the scales 30 and 32. A cam pulley 54 having a substantially frusto-conical cam portion rotatably supported on the supporting substrate 18 of the head and having a rope guide groove formed in a spiral shape in the cam portion; and the cam pulley 54 in a predetermined rotation direction. A urging spring 56 and a rope shape in which a plurality of turns are wound around the rope guide groove of the cam pulley 54, one end of which is connected to the enlarged diameter side of the cam pulley 54 and the other end of which is connected to an eccentric portion of the rotating body 38. The winding end S of the rope-like member 58 moves in the radial direction of the cam pulley 54 as the force of the spring 56 increases with the rotation of the cam pulley 54. In addition, the rope shape assumed when the end of the rope-shaped member 58 is set at a position infinitely separated from the rotation body 38 on the axis M passing through the center of the rotation body 38 and the center of the cam pulley 54. The angle formed by the actual pulling direction F2 of the rope-shaped member 58 with respect to the rotating body 38 with respect to the pulling direction F1 of the member 58 with respect to the rotating body 38 is θ, and the pulling of the rope-like member 58 with respect to the rotating body 38 is performed. Assuming that the balance pulling force of the rope-shaped member 58 for balancing the rotational force of the rotary body 38 when the direction is not changed is F, the balance pulling force of the rope-like member 58 with respect to the rotary body 38 is shown. A scale balance device characterized in that the diameter of the cam pulley 54 is set so that the force F'becomes F '= F / cos θ.