JPS634979Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an overload prevention mechanism for upper pan balances, which has a relatively simple configuration and has a weighing limit for an unbalanced load in which the load center is shifted from the center of the receiving tray (upper tray). The value and the weighing limit value for a center load where the load center coincides with the center of the saucer can be set and adjusted independently.

FIG. 1 is an explanatory diagram of the principle of a top balance.
1 is a Roberval mechanism, 2 is a saucer, 3 is a load detection mechanism, and 4 is a main body base. Roberval mechanism 1
is a pair of parallel stays 11, 12, and two connecting sides 13, 14 arranged in parallel so as to be orthogonal to these stays 11, 12 and connected to each stay 11, 12 via a flexure. It is configured. The saucer 2 is attached to one end with the connecting side 13 serving as a tray bearing shaft. The load detection mechanism 3 is attached to one end of the stay 11. Note that one end of the connecting side 14 is attached to the base 4. In such a configuration, the connection point between the stay 11 and the connection side 13 is a, and the connection point between the stay 11 and the connection side 14 is
Let b be the connection point between the stay 11 and the load detection mechanism 3, c be the connection point between the stay 11 and the load detection mechanism ₃ , and let the length between a and b be l 1 and the length between b and c be l ₂ , then a load W is applied to the saucer 2. In this case, a force P expressed as P=l ₁ /l ₂ W (1) acts on the load detection mechanism 3. The load detection mechanism 3 converts the magnitude of the force P into a predetermined signal form and sends it out as a measured value of the load W.

By the way, in such a device, if a load greater than the allowable value of the load detection mechanism 3 is applied to the saucer 2, there is a risk that the load detection mechanism 3 will be destroyed. Therefore, conventionally, an overload prevention mechanism is provided at the connection portion between the Roberval mechanism 1 and the receiving tray 2 to prevent a force exceeding a certain value from being applied to the load detection mechanism 3.

FIG. 2 is a simplified configuration diagram showing an example of a conventional overload prevention mechanism, in which a is a side view and b is a plan view. In FIG. 2, reference numeral 5 denotes a leaf spring disposed between the tray 2 and the main body 4 concentrically with respect to the tray bearing shaft 13. In such a configuration, when a load W is applied to the saucer 2 as a central load whose load center coincides with the center of the saucer 2, all leaf springs 5 are equally displaced, and the saucer 2 is moved in the axial direction of the saucer support shaft 13. Displaced along. Here, by appropriately selecting the distance L between the saucer 2 and the main body 4 and the spring constant of the plate spring 5, it is possible to prevent a load of more than a certain magnitude from being applied to the saucer support shaft 13. However, in the case of Fig. 2, when the load W is applied to the tray 2 as an unbalanced load with the load center deviating from the center of the tray 2, only a part of the leaf spring 5 is displaced, so that the center load is The overload prevention mechanism will operate with a smaller load. As a result, if the Roberval mechanism is ideally manufactured and configured so that no error occurs even when an unbalanced load is applied, the weighing limit value of the unbalanced load cannot be set to the maximum allowable value of the Roberval mechanism. become.

The present invention solves these drawbacks and will be described in detail below with reference to the drawings.

FIG. 3 is an explanatory diagram of the configuration of essential parts showing one embodiment of the present invention, and parts equivalent to those in FIGS. 1 and 2 are given the same reference numerals. In Figure 3, 6 is the first
7 is a guide member, 8 is a second elastic member, 9 is an E-ring, and 10 is a screw. Note that a stepped through hole 21 is provided in the center of the saucer 2, and the outer periphery of the saucer 2 is bent in a right angle direction. Further, the main body 4 is formed with a surface that faces the end surface of the outer periphery of the saucer 2, and a mounting hole is provided in the central portion.

One end 61 of the first elastic member 6 is formed into a disk shape, and the other end 62 is formed into a cylindrical shape and is formed to fit into the end of the countersunk shaft 13 whose interior is formed into a truncated cone shape. and the intermediate portion 6 between these ends
3 is formed into a cylindrical shape to provide flexibility. Further, an E-ring 9 is provided on the outer periphery of the cylindrical portion 62.
A groove 64 for fitting is provided.
The disc-shaped portion 61 is formed to fit into the large diameter portion of the stepped through hole 21 provided in the center of the saucer 2 so as to be movable in the depth direction of the through hole 21 and to face the stepped surface. The cylindrical portion 62 is formed such that it can be inserted through the small diameter portion of the through hole 21. Guide member 7
is formed into a substantially cylindrical shape such that it is movably fitted into the small diameter portion of the stepped through hole 21 of the saucer 2 and one end protrudes from the end surface of the small diameter portion, and the cylindrical shape of the first elastic member 6 is formed on the side surface. A cut groove is provided for passing the portion 63 through. This guide member 7 is screwed to the disk-shaped portion 61 via the screw 10 so as to enclose the column-shaped portion 63 of the first elastic member 6 . Second
The elastic member 8 is disposed between the saucer 2 and the cylindrical portion 62 of the first elastic member 6 so as to be substantially coaxial with the first elastic member 6. In this embodiment, a coil spring is used as the second elastic member 8, and one end of the coil spring 8 contacts the end surface of the through hole 21 of the saucer 2 and encloses the end of the guide member 7.
The other end encloses the cylindrical portion 62 of the first elastic member 6 and comes into contact with the E-ring 9. This coil spring 8 is connected to the saucer 2 in a non-overloaded state.
The saucer 2 is urged so as to maintain a distance between the outer peripheral end face of the main body 4 and the opposing face of the main body 4. Further, in this embodiment, a top lid 22 is placed over the saucer 2.

These are assembled as follows.

First, the guide member 7 is screwed to the first elastic member 6. Then, the first elastic member 6 and the guide member 7 are inserted into the through hole 21 of the saucer 2. Thereafter, the second elastic member 8 is attached so as to be substantially coaxial with the first elastic member 6, and the E-ring 9 is attached.
is fitted into the groove of the cylindrical portion 62 of the first elastic member 6. This constitutes the overload prevention mechanism according to the present invention.

The operation of the mechanism configured in this way will be explained.

For example, when a load is applied to the tray 2 such that the center of the load deviates from the center of the tray 2, the cylindrical portion 63 of the first elastic member 6 bends in the direction of the load, and the second elastic member 8 also bends in the direction of the load. When the receiving tray 2 bends in the direction and bends over a certain angle, the outer peripheral end of the tray 2 bent in the right angle comes into contact with the opposing surface of the main body 4. On the other hand, when a load is applied to the tray 2 such that the load center coincides with the center of the tray 2, only the second elastic member 8 is compressed along the axial direction of the tray support shaft 13, and the tray 2 is moved to the main body 4. The end of the saucer 2 comes into contact with the main body 4 by being pushed down a certain length or more.

That is, the first elastic member 6 mainly acts as an overload prevention mechanism against uneven loads, and the second elastic member 8 acts as an overload prevention mechanism against center loads. Therefore, by appropriately selecting the spring constants of these elastic members 6 and 8 and the distance between the end of the saucer 2 and the main body 4, the weighing limit value for eccentric loads and the weighing limit value for center loads can be set arbitrarily. (for example, approximately equal values).

As a result, the weighing limit value of the unbalanced load can be set to the maximum allowable value of the Roberval mechanism, and even though the external appearance of the object to be measured is uniform and it is placed in the center of the upper plate, the internal mass distribution etc. This is effective in cases where the load becomes substantially unbalanced, and it is possible to realize a top balance that is easier for the user to use.

In the above embodiment, a coil spring is used as the second elastic member, but a plate spring as shown in FIG. 2 may also be used. Also, the first
The elastic member is not limited to the shape of this embodiment, but can be modified in various ways to have similar functions.

As is clear from these, according to the present invention,
With a relatively simple configuration, it is possible to realize an overload prevention mechanism that can independently set and adjust the weighing limit values of the eccentric load and the center load, and is suitable as an overload prevention mechanism for various types of upper balances.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the principle of a top balance, Figure 2 is a simplified configuration diagram showing an example of a conventional overload prevention mechanism, and Figure 3 is a diagram explaining the principle of a balance.
The figure is a configuration explanatory diagram showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Roberval mechanism, 2... Receiver, 3... Load detection mechanism, 4... Main body, 6... First elastic member,
7... Guide member, 8... Second elastic member, 9...
E-ring, 10...screw.

Claims (1)

[Scope of Claim for Utility Model Registration] A saucer with a stepped through hole in the center and whose outer periphery is bent at right angles, a surface facing the end surface of the outer periphery of the saucer, and a mounting hole in the center. A main body is provided, and a dish support shaft disposed in the mounting hole of the main body, one end of which is engaged movably along the depth direction of the stepped through hole of the saucer, and the other end of which is engaged with the dish support shaft disposed in the mounting hole of the main body. a first elastic member formed in a cylindrical shape so as to be engaged with the shaft and have a portion between both ends flexible; and a first elastic member that is substantially coaxial with the first elastic member. is disposed between the ends of the elastic member that engages with the tray receiving shaft, and biases the tray so as to maintain a distance between the outer peripheral end surface of the tray and the opposing surface of the main body in a non-overloaded state. and a second elastic member.