JPH0343882B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, when the fixation of the drawing board mount is released and the drawing board mount is placed in a free rotation state, the drawing board mount is rotated by a downward load applied to the drawing board mount. This invention relates to a balance device for a drafting table that prevents the table from rotating suddenly in the direction of fall.

SUMMARY OF THE INVENTION An object of the present invention is to provide a balancing device for a drafting table which has a simple structure, is suitable for miniaturization, and is capable of setting a drawing board mount in a perfectly balanced state.

The configuration of the present invention will be described in detail below based on embodiments shown in the accompanying drawings.

Reference numerals 2 and 4 indicate horizontal foot levers, on which fixed leg members 6 and 8 are erected. Elevating leg members 10 and 12 are slidably fitted into the fixed leg members 6 and 8, and the elevating leg members 10 , 12 are vertical adjustment moldings 14, 16
By rotating it in the tightening direction, it can be fixed to the fixed leg members 6, 8 at a desired height.
A reinforcing rod 18 is installed between the leg members 6 and 8. A tube body 20 is installed between the upper ends of the leg members 10 and 12. Reference numerals 24 and 26 designate board mounting bodies, and these vertical parts are attached to both sides of the leg members 10 and 12 and are rotatable about an axis P horizontal to the floor surface, that is, a point on the central axis of the tube body 20. is supported by. Reference numeral 28 denotes an angle brake mechanism, which is configured so that the drawing board mounts 24 and 26 can be fixed to the leg members 10 and 12 by rotating the molding 30 in the tightening direction.

The above-mentioned drawing board attachment bodies 24, 26 are attached to the leg members 10, 1
Since the mechanism rotatably supported by the angle brake mechanism 28 and the angle brake mechanism 28 have common configurations, detailed explanations and illustrations thereof will be omitted. A drawing board 32 is fixed to the horizontal portions of the drawing board mounts 24, 26. Reference numeral 34 denotes a support rod fixed to the leg members 10, 12, and a stopper rod 36 is fixed to this. Said drawing board 3
The height of the stopper rod 36 is set so that the lower surface of the drawing plate 32 comes into contact with the upper end of the stopper rod 36 when the drawing board 32 is set in a horizontal state. A drawing machine (not shown) is attached to the drawing board 32. The rotation range of the drawing board 32 is usually set between a horizontal state and a substantially vertical state (or 70 degrees) with respect to the floor surface. Reference numeral 38 denotes a U-shaped rising portion formed on one side of the vertical portion of the drawing board mount 26, and screw rods 40 are rotatably mounted on both sides of the rising portion 38 to prevent movement in the axial direction. installed. A molding 42 is fixed to one end of the screw rod 40. 44 is a bridge member that is screwed into the threaded rod 40;
is in slidable contact with the guide surface of the rising portion 38 so as not to rotate in conjunction with the rotation of the threaded rod 40. 50 is a coil spring, one end of which is fixed to the leg member 12 with a screw. Reference numeral 52 denotes a rope guide consisting of a rope pulley that is rotatably supported by the leg member 12, and a bendable and flexible wire rope 54 is hung on the rope guide. One end 54 of the wire rope 54
a is connected to the bridge member 44, and the other end is connected to the coil spring 50. The wire rope 54 and the coil spring 50 collectively constitute a telescopic biasing body.

When the drawing plate mount 26 rotates around the axis P within a range of about 90 degrees, which is the horizontal position and the upwardly facing upward substantially vertical position in FIG. The member 44 rotates along a circular orbit centered on the axis P. As the bridge member 44 rotates, the rope 54 between the bridge member 44 and the rope guide 52 rotates in the left-right direction in FIG. move. The length between the support point 53 on the leg member 12 and one end 54a of the rope 54 when the amount of deflection of the elastic biasing body is zero, that is, in an unloaded state where no tensile force is applied to both ends. (The effective length of the elastic biasing body) is set to be the same as the distance between the support point 53 and the rotation base point E (that is, the rope restriction end E). In other words, when one end 54a of the rope 54 is moved to the rotation base point E, the spring 5
It is set so that the deflection in the direction of extension is zero. The spring 50 has a spring constant corresponding to the load applied to the drawing board mount 26 in its rotational direction. The reason why the effective length of the telescopic biasing body is set as described above is as follows.

As shown in FIG. 3, the horizontal part of the mounting body 26,
The angle between the rotation center P and the axis passing through the rotation reference point E is θ, the angle between the rope 54 and the axis is α, and the connection point between the attachment body 26 and the rope 54 is c. Assuming that the amount of extension of the spring 50 is l, this l changes depending on the above-mentioned θ, and its value is the distance between c and E. Spring force F acting on the mounting body 26 of the elastic biasing body
can be set as F=Kl. Here k is a spring constant. Further, if the torque radius applied to the mounting body 26 by the above spring force is R, the torque radius R can be set as R=(a+r)sinα, and this formula is expressed by the sine law of triangle PCE r/sinα= From l/sinθ, we can derive R=(a+r)・r・sinθ/l. Here, a is the distance between c and E when α=0, and r is the distance between Pc when α=0.

If the torque due to the above spring force F on the mounting body 26 is T, then T=F・R=kl・・(a+r)・r・sinθ/l=k・(a+r)・r・sinθ Here, the above k, a , r are constants, so the torque T is a function of sin θ.

That is, making the torque T a function of sin θ is the reason why when the one end 54a of the rope 54 is moved to the pivot point E, the deflection of the spring 50 in the extension direction becomes zero.

Next, the operation of this embodiment will be explained.

When the fixation to the mounting bodies 24 and 26 is released,
Due to the weight of the drawing board 32 and the drawing machine etc. attached to it, the mounting body 26 has a second position centered on point P.
In the diagram, rotational torque T' is generated in the direction of rotation of the hour hand.
The magnitude of this rotational torque T' and the rotational torque T acting on the mounting body 26 due to the elasticity of the spring 50 are the same, and their directions are opposite.
2 stands still at an arbitrary angle.

The above operation will be explained in more detail with reference to the explanatory diagram of FIG.

The attachment body 26 rotates around the point P with respect to the leg member 12, and the rope connection point C of the attachment body 26 connects to the rope 5.
4, when the mounting body 26 is rotated by an angle with the shortest distance between the point C and the rope regulating end E of the guide 52 being zero degree, the spring Let us consider the rotational torque T generated in the mounting body 26 by the rotational torque T.50. First, the strength F of the spring 50 when the mounting body 26 rotates is given by k being the spring constant of the spring 50 and x being the amount of extension of the spring 50. When the angle ○ of the mounting body 26 is zero degrees, the strength F of the spring 50 is When the tension of 50 is set to zero, F=kx=k(l-a).

The above l can be determined by the following formula.

l={(rsin) ² +(r+a-rcos ² )} ^1/2 = [r ² sin ² +{r(1-cos)+a} ² ] ^1/2 = {r ² sin ² +r ² (1- 2cos＋cos ² )＋2ra(
1−cos＋a ² } ^1/2 = {(r ² sin ² +r ² −2r ² cos＋r ² cos ² +2ra−2
racos + a ² } ^1/2 = {r ² (sin ² + cos ² ) + r ² −2r ² cos + 2ra (
1-cos) + a ² } ^1/2 = {2r ² -2r ² cos + 2ra (1-cos θ) + a ² } ^1/2 = {2r ² (1-cos θ) + 2ra (1-cos θ) + a ² } ^1/
2 = {(1-cos) (2r ₂ + 2ra) + a ² } ^1/2 Also, the rotation radius R required to rotate the attached body due to the tension of the rope 54 is R =
It can be calculated as (a+r)sinα.If you transform this, R=(a+r)rsin/l The torque T that rotates the mounting body 26 due to the expansion of the spring 50 is T=F×R, so use the above formula as F and R. If you enter the value of .

T=k(l-a)(a+r)r・sin/l becomes.

When a=0, T=krsin. kr is constant, and from this equation it can be seen that T is a function of sin. here,
As shown in FIG. 4, w is the load due to the weight of the drawing plate 32, etc. applied in the direction of rotation of the mounting body 26 on the center of gravity G of the mounting body, and r' is the distance between the center of gravity G and the rotation center of the mounting body 26. Then, when the horizontal plane of the mounting body 26 is rotated until it becomes approximately perpendicular to the floor surface, and the state of the mounting body in which the load w does not act on the mounting body 26 as rotational torque is set to zero degrees, the mounting body is rotated until it becomes approximately perpendicular to the floor surface. Rotational torque generated by load w when rotated
T′ is calculated by T′=wr′sin.

The value of wr′ is constant, and from this the torque T′ becomes sin
It turns out that it is a function of

This shows that when a=0, the rotational torques T and T' of the mounting body 26 in the forward and reverse directions can be perfectly balanced. Also, as shown in Fig. 5, the torque change when the above r is shortened is as follows: When the above l={(1-cos) (2r ² +2r・a)+a ² } ^1/2 is changed, l= {(1−cos)( ^2rs2 +2rsb)+ ^b2 } becomes ^1/2 .

In addition, rs is the rotation center of the mounting body 26 and the rope connection point C
b is the distance between the rope regulating end of the guide 52 and the rope connection point C' when the mounting body 26 is at zero degrees. Note that when the rope connection point C is moved to point D, the tension in the rope 82 becomes zero. The distance between this point D and the rope regulating end E of the guide 80 is a, and the point D
If the distance between the rope connection point C' and the rope connection point C' is d, the above b is expressed as b=(a+d).

The actual elongation lr of the spring 50 is lr=(l-b)+d The strength F of the spring 50 is F=K(l-b+d).

Furthermore, the radius of rotation R assumed on the rotation plane of the mounting body as a rotational torque generating element is R = (a + r) sin α = (a + r) rs · sin / l Therefore, the rotation radius R generated on the mounting body 26 by the spring 50 is as follows. The rotational torque T is as follows: T=F×R=k(lb+d)(a+r)rs·sin/l.

Since the value of l changes depending on the rotation angle of the mounting body 26, the change characteristic of the rotational torque T generated in the mounting body 26 by the spring 50 does not form a sin curve. However, since the change characteristic of the rotational torque T' generated on the mounting body 26 due to the weight of the drawing machine etc. as the mounting body rotates forms a sin curve, the rotational torque generated on the mounting body 26 in the forward and reverse directions is balanced. I can't do it. However, if the tension of the spring 50 is set to zero when the rope connection point C on the attachment body 26 is brought to the rope restriction end E of the rope guide 52 in FIG. Spring force F can be found as F=kl.

Here, if H is the distance between the rope regulating end E and the rotation center P of the attachment body, and rs is the distance between the rope connection points C and P, then the extension l of the spring 50 is: l=√ ² + ² −2・・It becomes.

The rotational radius R of the spring 50 as a rotational torque generating element is R=H・sinα and x=l・sinα=rs・sin, so R=H・rs・sin/l From this, the spring force of the spring 50 Therefore, the rotational torque T generated in the mounting body 26 is T=kl×R kl×H・rs・sin/l k・H・rs・sin Therefore, the rotational torque T due to the spring 50 becomes sin×constant, which corresponds to the SIN curve. Become. From the above formula, if the tension of the spring 50 is set to be zero when the rope end is moved to the rope restriction end E of the guide 52, the spring connection point C can be moved from the center of rotation of the mounting body 26 in FIG. It can be seen that even if the spring 50 is set at any position on the left side, the change characteristic of the rotational torque T generated in the mounting body 26 by the spring 50 can be made into a SIN curve. As shown in Fig. 6, if a rope guide is not installed, and assuming that the rope guide is infinitely far away from the mounting body, the spring force of the spring = k (rs - rs・cos) = krs ( 1-cos).
Also, since the rotational radius R of the spring as a rotational torque generating element is R=rs・sin, the rotational torque T generated on the rotating body by the tensile force of the spring is T=krs(1−cos)×rs・sin =k.rs.sin (1-cos) Therefore, the variation characteristic of the rotational torque T does not form a sin curve as shown in FIG.

Next, the operation for adjusting the rotation radius R will be explained.

When the molding 42 is rotated, the screw shaft 40 is rotated. As a result, the bridge member 44 moves along the screw shaft 40, and the rope terminal 54a moves in conjunction with the bridge member 44 on the mounting body 26 in its extending direction.
Due to the movement of the rope terminal 54a, the mounting body 26
The distance of the rope connection point C with respect to the center of rotation changes. Therefore, when replacing the drafting machine, by adjusting the rotation of the molding 42, the tension load F of the spring 50 can be applied to the rotational torque T' generated on the mounting body 26 by the load W. The magnitudes of the rotational torques T generated in the mounting body 26 can be matched. Incidentally, as shown in FIGS. 8 and 9, the cylindrical body 60 is rotatably attached to the leg member 12 using a shaft 62.
The tip 64a of the rod 64 supported by the coil spring 66 is rotatably connected to the eccentric portion of the mounting body 26, and the tension force of the rod 64 causes the mounting body 26 to move in the counterclockwise rotation direction of the hour hand. It may be energized. In this configuration, the initial elasticity of the spring is set so that when the tip 64a of the rod 64 is moved to the center of rotation of the cylinder 60, the elastic force of the coil spring 66 becomes zero.

Further, as shown in FIG. 10, both end portions 70a and 7
One end 70a of a bending spring 70, which is set so that the elasticity is zero when the two springs are overlapped, is rotatably supported by a shaft 72 on the leg member 12, and the other end 70b is rotatably attached to an eccentric portion of the mounting body 26. Even if the drawing board mounting body 26 is connected to the drawing board mounting body 26, it is possible to achieve perfect balance as in the above embodiment. In the first to third embodiments described above, the rope guide 52, the shaft 6
2. The shaft 72 is a rotation guide member that restricts the swinging motion of the telescopic biasing body due to the rotation of the drawing plate mounting body 26 to a swinging motion centered on a single pivot point on the leg member 12. It consists of In addition, the cylinder body 60, the rod 64
The coil spring 66 as a whole constitutes a telescopic biasing body, and similarly, the bending spring 70 constitutes a telescopic biasing body. In FIG. 2, when the amount of deflection of the coil spring 50 is zero (initial state), the effective length of the elastic biasing body, that is, the support point 53 on the leg member 12 of the elastic biasing body and one end 5 of the rope 54
The length up to 4a is set to be the same as the distance from the support point 53 to the rotation reference point (namely, the rope restriction end E).

In FIGS. 8 and 9, when the amount of deflection of the coil spring 66 is zero (initial state), the effective length of the telescopic biasing body (cylindrical body 60, rod 64, coil spring 66), that is, the length of the telescopic biasing body The support point on the leg member 12 (the center point of the shaft 62) and the rod 6
4 to the tip 64a is the pivot point E on the leg member 12 of the telescopic biasing body (i.e., the axis 6).
The distance is set to be the same as the distance to the center point of In the embodiment shown in FIGS. 8 and 9, the support point and the pivot point E are set at the center of a common axis 62. In the embodiment shown in FIGS. Therefore, the value of the effective length and the distance between the support point and the rotation base point E are both set to zero.

In FIG. 10, when the amount of deflection of the spring 70 is zero (initial state), the effective length of the telescopic biasing body (bending spring 70), that is, the leg member 12 of the telescopic biasing body
The length from the upper support point (the center point of the shaft 72) to the other end 70b is the distance between the support point and the leg member 12 of the telescopic biasing body.
The distance is set to be the same as the distance to the upper rotation base point E (that is, the center point of the shaft 72). In the embodiment shown in FIG. 10, the support point and the pivot point E are set at the center of a common axis 72. In the embodiment shown in FIG. Therefore, the value of the effective length and the distance between the support point and the rotation base point E are both set to zero.

Since the present invention is constructed as described above, it has the advantage that the balance of the drawing board mount can be set accurately with a simple construction.

[Brief explanation of drawings]

Figure 1 is a front view, Figure 2 is a side view, Figure 3 is an explanatory diagram, Figure 4 is an explanatory diagram, Figure 5 is an explanatory diagram, Figure 6 is an explanatory diagram, Figure 7 is an explanatory diagram, 8 is a side view showing another embodiment, FIG. 9 is an explanatory view thereof, and FIG. 10 is a side view showing another embodiment. 2, 4...Horizontal foot lever, 24, 26...Drawing board mounting body, 12...Elevating leg member, 32...Drawing board, 50...
...Spring, 54...Wire rope.

Claims (1)

[Claims] 1. In a drafting table consisting of a leg member 12 and a drawing board mount 26 rotatably supported by the leg member 12 in a plane substantially perpendicular to the floor surface, one of the telescopic biasing members is connected to the leg member. 12 side, and the other ends 54a, 64a, 70b of the elastic biasing body are rotatably connected to an eccentric position of the drawing board mounting body 26 at a predetermined distance from the center of rotation with respect to the leg member 12, The swinging motion of the telescopic biasing body on the leg member 12 side that accompanies the rotation of the drawing board mounting body 26 is restricted to a swinging motion centered on a rotational reference point E on the leg member 12. Rotation guide members 52, 62, and 72 are provided, and the effective length of the telescopic biasing body in a state where the amount of deflection is zero, the support point 53 on the leg member 12 of the telescopic biasing body, and the rotation. A balancing device for a drafting table, characterized in that the distance between the base points E and the distance between them are substantially the same.