JP2008076069A - Electronic balance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic balance capable of preventing a resin body case from being charged with an inexpensive constitution without adding processing to the body case after being sealed. <P>SOLUTION: This electronic balance 1 is equipped with a weighing dish 3 for placing a weighing object thereon; a strain generating element 30 onto which the weight of the weighing object placed on the weighing dish 3 is loaded through a mounting member 42 and a movable part; a metal base 10 for supporting a fixed part of the strain generating element 30; and the resin body case 2 having a through hole 21h into which the mounting member 42 is inserted, for storing the base 10. The balance 1 has a constitution wherein a metal plate in contact with the surface or the back of an upper plate part 21u wherein the through hole 21h in the body case 2 is formed, or a conductive member 7 comprising a metal film is provided, and the charge in the body case 2 is allowed to escape to the base 10 through the conductive member 7. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electronic balance.

In recent years, a main body case of an electronic balance is generally formed of a resin from the viewpoint of weight reduction and ease of processing. However, if the resin main body case is charged due to friction or the like, there is a risk that various problems such as malfunction of the built-in electronic substrate may occur due to high insulation and no escape from static electricity. In particular, the weighing accuracy is lowered because the metal weighing pan is attracted to the case side. Then, the proposal which forms all or one part of a main body case with an electroconductive resin material is made | formed (patent document 1).
In addition, based on the measurement method, the measuring unit of the electronic balance is sealed in one case after being tested (Patent Document 2).
JP-A-61-288123 (Claim 1) JP 7-43198 (2nd page)

  However, the conductive resin material is expensive, and an increase in the cost of the electronic scale is inevitable. Moreover, it is not allowed to add any processing to the sealed main body case after passing the test.

  Accordingly, an object of the present invention is to provide an electronic scale capable of preventing charging of a resin-made main body case with an inexpensive configuration without releasing the sealed main body case.

Incidentally, some users have a desire to add a communication function or the like to the electronic scale. On the other hand, a user who does not need a communication function or the like causes unnecessary cost increase. For this reason, it is preferable to additionally mount components that are not essential for measurement, such as communication functions, as optional components.
However, as described above, since the main body case is sealed, it is difficult to mount the optional parts with good appearance.

  Accordingly, another object of the present invention is to provide an electronic balance that can be attractively accommodated in an optional part such as a communication board.

  In order to achieve the above object, an electronic balance according to the present invention includes a weighing pan for placing an object to be weighed, and the weight of the object to be weighed placed on the weighing pan is loaded via an attachment member and a movable part. A strain relief body, a metal base that supports a fixing portion of the strain relief body, a through hole through which the mounting member is inserted, and a resin main body case that houses the base. In the electronic scale, a conductive member made of a metal plate or a metal film is provided in contact with the front surface or the back surface of the upper plate portion in which the through hole is formed in the main body case, and the electric charge of the main body case reduces the conductive member. And is configured to escape to the base.

According to the present invention, since the electric charge of the resin main body case escapes to the base, the strain generating body and the like through the conductive member, the main body case can be prevented from being charged. Therefore, it is possible to prevent the weighing pan from being attracted to the main body case by the electrostatic force, and it is possible to prevent a reduction in weighing accuracy.
In particular, the strain body is formed by cutting out an ingot of aluminum, and the base and the fixed portion and the movable portion of the strain body are formed by a thick aluminum die-cast to make a robust structure that does not cause distortion. Therefore, it has a sufficient volume for releasing the charge.
In addition, the addition of a metal plate or metal film, unlike the case where the main body case is made of conductive resin, does not increase the cost as much as possible, and only attaches conductive members to necessary models such as high-resolution electronic scales with high resolution and accuracy. I get out.

In this invention, it is preferable that the said electroconductive member is provided in the upper surface of the said main body case which faces the said weighing pan.
According to this aspect, since it is possible to prevent electric charges from being accumulated at the portion facing the weighing pan, the reliability of the weighing accuracy is further increased.

In the present invention, the conductive member comprises a metal plate provided on the upper surface of the main body case facing the weighing pan, and the metal plate is formed by a metal male screw member that penetrates the main body case and the metal plate. It is preferable that the metal plate is fixed in a state in pressure contact with the main body case, and the metal plate is electrically connected to the base via the metal male screw member.
According to this aspect, the contact pressure between the main body case and the plate is obtained by the axial force of the male screw member, and the charge can be surely and instantaneously released to the base.

  In order to achieve another object of the present invention, an electronic balance of the present invention includes a weight detector in a sealed space of a sealed main body case, and the weight of an object to be weighed based on a detection output from the weight detector. In the electronic balance that stores the electronic circuit for calculating the storage unit, a storage part in which a part of the main body case protrudes toward the sealing space is formed on the outer surface side of the main body case, and the storage part and the sealing space are formed. A communication hole to be communicated is formed in the main body case, a signal line drawn out from the electronic circuit is led out to the storage part through the communication hole, and a connector provided at a tip of the signal line is disposed in the storage part. And is provided so as to be able to be pulled out from the storage portion.

According to the present invention, an optional electronic device such as a communication board (for example, a communication device) can be provided in the recess of the storage unit without releasing the seal, and the option can be provided in the recess of the storage unit. It can be stored nicely.
In particular, since the signal line is inserted into the communication hole and the connector can be pulled out from the storage portion, an optional electronic device to be stored in the storage portion can be coupled to the connector outside the storage portion.

In the present invention, in the state where the signal line is connected to the connector, the connector can be inserted into the storage portion from the sealing space through the communication hole, and the signal line is inserted into the sealing space of the main body case. It is preferable that the communication hole and the connector are formed so that the connector engages with a portion of the body case around the communication hole and does not enter the sealing space when pulled in the direction.
According to this aspect, when the electronic balance is manufactured, the connector connected to the signal line can be inserted into the storage portion from the sealing space side through the communication hole. On the other hand, when the product is used, the connector in the storage portion is connected to the sealing space. There is no risk of getting in.

In the present invention, a cover that covers a communication electronic device housed in the recess of the housing portion is attached to the main body case, and the main body case has a main body case that is substantially orthogonal to a surface on which the cover is provided. It is preferable that an insertion hole for connecting a communication cable to the connector of the electronic device is formed on the outer surface.
According to this aspect, since the surface on which the cover is mounted and the surface on which the insertion hole of the connector is provided are substantially orthogonal, no load is applied to the cover when the connector is pushed in and pulled out. Hard to be damaged.

In the present invention, it is preferable that a positioning portion for positioning the electronic device in the main body case is formed in the main body case and the cover.
According to this aspect, the electronic device is stored without rattling in the recess of the storage unit.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
Electronic scale 1:
As shown in FIG. 1, the electronic balance 1 includes a resin-made main body case 2 and a weighing pan 3 for placing an object to be weighed. The main body case 2 is provided with a display unit 4 and operation buttons 5. When an operator places a measurement object on the weighing pan 3 after performing a predetermined operation on the operation button 5, The weight of the weighing object is displayed on the display unit 4.

  As shown in FIG. 2, when the weighing pan 3 (FIG. 1) is removed, the tray receiving member 6 and the metal plate 7 (an example of a conductive member) appear. The metal plate 7 is attached to the upper surface of the main body case 2 by metal first and second male screw member members 16a and 16b.

  As shown in FIG. 3, the main body case 2 includes an upper case 21 and a lower case 22, and a sealing space 2 </ b> S is formed between the upper and lower cases 21 and 22. A control board 9 having a weight detector 8 and an electronic circuit is accommodated in the sealing space 2S.

Weight detector 8:
As shown in FIG. 4, the weight detector 8 includes a strain body 30. The strain body 30 is formed with a substantially H-shaped hollow portion 34. A fixed portion 31 and a movable portion 32 are formed at both ends of the strain body 30. The raised portion 11 and the mounting member 42 of the base 10 are fastened to the fixed portion 31 and the movable portion 32 via bolts 12, respectively. In FIG. 3, the base 10 is shaded.

  The metal plate 7 and the upper case 21 are formed with first and second through holes 7h and 21h through which the attachment member 42 is inserted (see FIG. 3). A dish receiving member 6 is fixed to the upper end of the attachment member 42, and the weighing dish 3 is placed on the dish receiving member 6. Therefore, the weight of the object to be weighed placed on the weighing pan 3 is loaded on the movable portion 32 of the strain body 30 via the tray receiving member 6 and the attachment member 42.

  On the other hand, as shown by the halftone dots in FIG. 3, the upright portion 11 is formed integrally with the metal base 10 fixed on the lower case 22. Therefore, the fixing portion 31 of the strain body 30 shown in FIG. 4 is supported by the base 10 in a cantilever state via the upright portion 11.

Strain body 30:
A pair of beams 33 are formed above and below the strain body 30, and the hollow portion 34 is formed inside the beam 33. Four thin strain generating portions 35 are formed at both ends of the beam 33. Detection elements 36 are provided at positions above and below the strain body 30 corresponding to each strain section 35. The detection element 36 is connected to the control board 9 (FIG. 3).

  When an object to be weighed is placed on the weighing pan 3 and a load is applied, the strain generating portion 35 of the strain generating body 30 is deformed via the tray receiving member 6 and the mounting member 42, and the control substrate 9 (FIG. 3) The electronic circuit detects the weight of the object to be measured by detecting the distortion of the surface of the strain generating portion 35 by the change in the electric resistance of the four detecting elements.

Control board 9:
On the control board 9 shown in FIG. 3, an analog circuit, an A / D converter, an arithmetic circuit, a display unit 4, an operation button 5, and the like (not shown) are mounted. The arithmetic circuit is composed of a digital circuit composed of, for example, a microcomputer.
The electric signal from the detection element 36 (FIG. 4) is digitized by an A / D converter, and then the weight is calculated by an arithmetic circuit, and the weight is displayed on the display unit 4.

Degradation of weighing accuracy due to static electricity:
Here, if the resin-made main body case 2 is charged due to friction or the like and there is no place for static electricity, the analog circuit may be disturbed and the measurement accuracy may be reduced. In particular, due to the charging of the main body case 2 in FIG. 1, the metal weighing pan 3 may be attracted to the main body case 2 and the measurement accuracy may be reduced.
Therefore, in the electronic balance 1, static electricity charged in the main body case 2 is released from the metal plate 7 attached to the main body case 2 in FIG. 3 to the base 10 and the strain body 30.

Antistatic structure:
As shown in FIG. 4, the metal plate 7 is in contact with the surface of the upper plate portion 21 u in which the second through hole 21 h of the upper case 21 is formed.

  As shown in FIG. 3, the metal plate 7 is provided with a first hole 7a therethrough. A second hole 21 a is provided in the upper case 21 so as to penetrate the upper case 21. On the other hand, a metal connection plate 15 is raised on the base 10 in the vertical direction. The connecting plate 15 is formed with a female screw portion. The first male screw member 16a is inserted into the first hole 7a and the second hole 21a and is screwed into the female screw portion of the connecting plate 15, thereby The plate 7 is electrically connected to the base 10 via the male screw member 16 a and the connection plate 15.

  The base 10 is formed of, for example, a thick aluminum die cast, for example, in order to obtain a robust structure that does not cause distortion. On the other hand, the strain body 30 is formed by cutting out an aluminum ingot, for example.

As described above, since the conductive strain generating body 30 and the base 10 are connected to each other, the conductive strain generating body 30 and the base 10 have a sufficient volume for releasing the charge of the main body case 2.
Therefore, even if charges are generated in the main body case 2 due to friction or the like, the charges can be released from the metal plate 7 to the strain body 30 or the base 10 via the male screw member 16a and the connection plate 15.

On the other hand, the metal plate 7 is provided with a mounting hole 7b therethrough, and the upper case 21 is formed with a female screw 21b. The first and second male screw member members 16 a and 16 b are screwed into the upper case 21 and the connection plate 15, respectively, so that the metal plate 7 is fixed in a state of being pressed against the upper case 21.
Therefore, the contact pressure between the main body case 2 and the metal plate 7 is obtained by the axial force of the male screw members 16a and 16b, and the metal plate 7 comes into close contact with the upper plate portion 21u of the upper case 21, thereby Electric charges can be reliably and instantaneously released to the base 10 and the strain body 30.

In particular, since the metal plate 7 is formed in substantially the same size as the circular planar shape of the weighing pan 3, the contact area with the main body case 2 is sufficiently large. The base 10 and the strain body 30 can be surely and instantaneously released.
Further, as described above, since the metal plate 7 is provided facing the weighing pan 3, it is possible to prevent electric charge from being accumulated in a portion facing the weighing pan 3. It is prevented from being attracted to the second side, and the reliability of weighing accuracy is improved.

  Moreover, since the metal plate 7 can also be expected to have a shielding effect against incoming radio waves, the measurement accuracy can be further prevented from being lowered.

Sealing the electronic balance 1:
The electronic balance 1 shown in FIG. 3 includes upper and lower cases 21, which are mounted by assembly screws 28 shown by broken lines in FIG. 5 after the weight detector 8 and the control board 9 are stored in the sealed space 2S of the main body case 2. 22 are assembled together. After the assembly, after receiving the test, the electronic balance 1 that has passed the test is sealed with a sealing tape 29 on the assembly screw 28.

Optional parts mounting structure:
By the way, as shown in FIG. 6, the electronic balance 1 can be attached to the electronic balance 1 after sealing as an optional device, such as a communication card 60, as an optional device. It is.

  As the communication card 60, for example, in addition to an IEEE standard communication card including Ethernet (registered trademark), USB (Universal Serial Bus), serial interface, parallel interface, interface to an external display, etc. are necessary for verification. Some have functions other than the weighing function.

Hereinafter, the mounting structure of the communication card 60 will be described.
As shown in FIG. 3, the lower case 22 has a storage portion 23 that protrudes toward the sealing space 2 </ b> S of the lower case 22 on the outer surface 22 u of the lower case 22 shown in FIG. 5.
The lower case 22 shown in FIG. 3 is provided with a communication hole 24 that allows the storage portion 23 and the sealing space 2S to communicate with each other through the storage portion wall 23b of the storage portion 23. In the communication hole 24, a communication line (an example of a signal line) 51 drawn from the electronic circuit of the control board 9 is led out into the storage portion 23 through the communication hole 24.

  As shown in FIG. 5, the first connector 50 is connected to the tip of the communication line 51. In addition to the communication line 51, for example, a power line may be connected to the first connector 50.

The first connector 50 is disposed in the recess 23 a of the storage portion 23 and is provided so as to be able to be pulled out from the recess 23 a of the storage portion 23.
As shown in FIGS. 3 and 6, when the electronic balance 1 is assembled, the first connector 50 is connected to the control hole 9 and the first connector 50 from the communication hole 24 in a state where the control board 9 and the first connector 50 are connected via the communication line 51. It is pushed toward the recess 23 a of the storage part 23.
The shape and size of the communication hole 24 is such that the first connector 50 can be inserted into the storage portion 23 from the sealed space 2S through the communication hole 24 in a state where the communication line 51 is connected to the first connector 50. Further, when the communication line 51 is pulled toward the sealing space 2S of the main body case 2, the first connector 50 is formed so as to engage with the portion of the lower case 22 around the communication hole 24 and not enter the sealing space 2S. ing. For example, the length L1 and the width W1 of the communication hole 24 in FIG. 6 are larger than the length L2 and the width W2 of the first connector 50 in FIG. 5 and the length L2 of the first connector 50 is the communication hole 24. It is larger than the width W1.

As shown in FIG. 6, a second connector 61 for connecting a communication cable is provided at the end of the communication card 60.
The lower case 22 is formed with an insertion hole 26 into which the second connector 61 of the communication card 60 is fitted when the communication card 60 is connected. The insertion hole 26 is formed on the outer surface on the rear side of the lower case 22 that is substantially orthogonal to the surface on which the cover 25 is provided.

  As shown in FIG. 5, the electronic balance 1 is provided with a cover 25 that covers the communication card 60 stored in the recess 23 a of the storage unit 23. By sliding the cover 25 in the longitudinal direction X, the cover 25 can be opened and closed.

How to install the communication card 60:
In order to attach the communication card 60 to the electronic balance 1, the cover 25 is opened as shown in FIG. 5, the first connector 50 is pulled out from the recess 23a, and then the communication card 60 is connected to the first connector 50 as shown in FIG. 60 is connected. After the connection, the end of the second connector 61 of the communication card 60 is opposed to the insertion hole 26 and the communication card 60 is stored in the recess 23 a of the storage unit 23. Thereafter, the cover 25 is attached to the lower case 22. The second connector 61 faces the outside of the main body case 2 through the insertion hole 26, and a communication cable (not shown) from an external device can be connected to the second connector 61.

Thus, even after the main body case 2 of the electronic balance 1 is sealed, it is convenient because the communication card 60 can be added without releasing the sealing.
Further, since the surface on which the cover 25 is mounted and the surface on which the insertion hole 26 of the second connector 61 of the communication card 60 is provided are orthogonal, the communication cable connected to the second connector 61 is inserted or removed. Since the load is not applied to the cover 25 sometimes, the cover 25 is hardly damaged.

  In addition, since the insertion hole 26 is provided at the rear of the electronic balance 1, the communication cable connected to the second connector 61 can be connected to the rear of the electronic balance 1 instead of the front where the display unit 4 is located. The kind of handling is good and does not get in the way.

Positioning portions 25a and 25b:
Here, the cover 25 is formed with a first positioning portion 25 a for fixing one side surface of the communication card 60. On the other hand, a second positioning portion 25 b for fixing the other side surface of the communication card 60 is formed in the storage portion 23. The 2nd positioning part 25b is comprised by the groove | channel by which the other side surface of the communication card 60 fits, and the groove | channel by which the 2nd connector 61 part fits.
Therefore, the communication card 60 is stored in the storage unit 23 without rattling by mounting the communication card 60 according to the positioning portions 25a and 25b.

Program storage device:
By the way, in recent electronic balances 1, application software functions such as aggregation and sales management functions which are additional functions are evolving day by day. On the other hand, the software related to the basic measurement cannot be changed by the test.
Therefore, in the present electronic balance 1, in order to protect the software related to the verification from falsification and to allow the application software to be upgraded, the software portion related to the verification is encrypted to prevent the falsification.

  Various methods such as stream cipher and block cipher can be used for the encryption, but in the following description, a method of generating a secret key made up of an encrypted file as a seed based on the bit information of the target file will be exemplified. I will explain.

The main body case 2 of the electronic balance 1 is provided with a mounting portion (card slot) (not shown) in which a memory card (an example of a program storage device) can be mounted from the outside of the sealed main body case 2.
As the memory card 70, for example, a commercially available memory card SD card (registered trademark) or memory stick (registered trademark) with a security function can be used.

As shown in FIG. 7, the memory card 70 is provided with a protect area 71 and a normal area 72.
The protected area 71 can be read and written only by a dedicated device. The protected area 71 stores the encrypted file F1.
On the other hand, in the normal area 72, an encrypted verification target file F2 and an unencrypted non-verification target file F3 are stored.

The electronic balance 1 is provided with a decryption means. The encryption file F1 stores an encryption file (seed) of application software to be tested. The encryption file is generated by dedicated application software based on the bit information of the verification target file and written by a dedicated device.
The verification target file F2 stores a verification target file made of software related to verification encrypted (scrambled) with the seed of the encryption file F1. The verification target file is decrypted by the decryption means of the electronic balance 1 based on the encrypted file and executed. The electronic balance 1 does not have a function of correcting or writing the encryption file or the verification target file.
Application software other than the test target is stored in the non-test target file F3.

In this way, the application software related to the verification is encrypted to prevent falsification, and the application software not related to the verification can be rewritten, thereby facilitating software upgrade.
Therefore, conventionally, in order to upgrade the software other than the verification target, after the seal of the main body case 2 is released and the control board is replaced with a new control board on which the upgraded software is installed, The electronic balance 1 needs to be tested again, but by replacing the memory card 70, it is possible to upgrade the software other than the test target very easily without releasing the seal of the main body case 2. .
Therefore, maintainability becomes extremely easy, and the substrate inventory can be greatly reduced.

In the above description, the male screw member 16a and the connection plate 15 are used for the connection between the metal plate 7 and the base 10. However, the male screw member 16 is connected to the base 10 without the connection plate 15. The metal plate 7 and the base 10 may be connected by a conductive wire or the like.
Further, the metal plate 7 may be provided on the back surface of the upper plate portion 21u of the upper case 21.
In addition to the metal plate 7, the conductive member may be, for example, a conductive metal film, a metal sheet, or a metal seal.

Further, the conductive member may not be provided on the normal product, but may be provided on the surface of the main body case 2 as an option as required, such as a product requiring high accuracy. In particular, in an electronic balance that requires an examination, it is convenient because the conductive member can be easily attached without releasing the seal even after the main body case 2 is sealed.
Further, the metal plate 7 may be smaller in diameter and size than the weighing pan 3 so as not to impair the appearance design of the product.
Further, the weighing pan 3 does not have to be circular, and may be square, for example. In such a case, it is preferable that the metal plate 7 has a shape similar to the shape of the weighing pan 3.

  This apparatus can be used for an electronic balance.

It is a schematic perspective view which shows the electronic balance concerning a present Example. It is a schematic perspective view which shows the electronic balance of the state which removed the weighing pan. It is a disassembled perspective view of the electronic balance of the state which removed the weighing pan and the tray receiving member. It is a schematic sectional drawing which shows the part of a weight detector. It is the schematic perspective view seen from the back surface of the electronic scale of the state which removed the cover. It is a schematic perspective view from the back surface of the electronic scale which shows the back surface and storage part of a cover. It is a conceptual diagram which shows the memory content of a memory card.

Explanation of symbols

1: Electronic scale 2: Body case 2S: Sealing space 3: Weighing pan 7: Metal plate (an example of a conductive member)
8: Weight detector 9: Control board 10: Base 16a: Male screw member 21h: Second through hole 21u: Upper plate part 23: Storage part 24: Communication hole 25: Cover 25a, 25b: Positioning part 26: Insertion hole 30: strain body 31: fixed part 32: movable part 42: mounting member 50: first connector 50
51: Communication line (an example of a signal line)
60: Communication card (electronic device for communication)
61: Second connector

Claims (7)

A weighing pan for placing an object to be weighed;
A strain body in which the weight of the object to be weighed placed on the weighing pan is loaded via an attachment member and a movable part;
A metal base that supports the fixed portion of the strain body;
In an electronic scale having a through-hole through which the mounting member is inserted, and a resin-made main body case that houses the base,
A conductive member made of a metal plate or a metal film is provided in contact with the front or back surface of the upper plate portion in which the through hole is formed in the main body case,
An electronic balance configured to allow the electric charge of the main body case to escape to the base via the conductive member.   The electronic balance according to claim 1, wherein the conductive member is provided on an upper surface of the main body case facing the weighing pan. In Claim 1, the conductive member comprises a metal plate provided on the upper surface of the main body case facing the weighing pan,
The metal plate is fixed in a state of being pressed against the main body case by the main body case and a metal male screw member penetrating the metal plate, and the metal plate is fixed to the base via the metal male screw member. Electronic balance that is electrically connected to the. In an electronic balance containing a weight detector in the sealed space of the sealed main body case, and an electronic circuit for calculating the weight of an object to be measured based on the detection output from the weight detector,
A storage part in which a part of the main body case protrudes toward the sealing space is formed on the outer surface side of the main body case,
A communication hole for communicating the storage portion with the sealing space is formed in the main body case,
A signal line drawn out from the electronic circuit is led out to the storage portion through the communication hole;
An electronic balance in which a connector provided at the tip of the signal line is disposed in the storage portion and is provided so as to be able to be pulled out from the storage portion.   5. The connector according to claim 4, wherein the connector can be inserted into the housing portion from the sealing space through the communication hole in a state where the signal line is connected to the connector, and the signal line is sealed in the sealing space of the main body case. An electronic balance in which the communication hole and the connector are formed so that when the connector is pulled toward the connector, the connector engages with a portion of the main body case around the communication hole and does not enter the sealed space. In Claim 4, the cover which covers the electronic equipment for communication stored in the recess of the storage part is attached to the main body case,
An electronic balance in which an insertion hole for connecting a communication cable to a connector of the electronic device is formed in the outer surface of the main body case that is substantially orthogonal to the surface on which the cover is provided.   The electronic balance according to claim 6, wherein the main body case and the cover are formed with positioning portions for positioning the electronic device on the main body case.

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