Patent Description:
Conventionally, as a mechanism to automatically open and close a door of a windshield, various mechanisms are proposed. For example, in Patent Literature <NUM>, an air cylinder to open and close a door is disposed right beside the door, and a rod is fixed to the door through a suction cup. Patent Literature <NUM> shows a balance of the state of the art in accordance with the preamble of claim <NUM>. Patent Literatures <NUM>-<NUM> show further background art for the present invention.

However, the mechanism in Patent Literature <NUM> has a problem in which it is difficult to smoothly move the door. A certain degree of attaching area is necessary for connecting the door and the air cylinder, so that the connection location is limited to a door central portion, and a torsion is generated with respect to upper and lower edge portions of the door that slides when opening and closing, and difficulty in sliding and sudden opening and closing occur.

The present invention was made in view of the problem described above, and an object thereof is to provide an electronic balance with a windshield having a door to be automatically opened and closed smoothly.

In order to solve the problem described above, an electronic balance of the present invention includes a balance main body including a weighing mechanism connected to a weighing pan, a windshield configured to form a weighing chamber by covering the weighing pan, a slidable door provided in the windshield and constituting a portion of the weighing chamber, holders disposed at front and rear end portions of the door configured to support the door from an upper portion in a hanging manner, a guide member configured to engage with the holders and slidably support the holders, and an air cylinder connected to the holders and configured to slide the door through the holders. The holders supporting the door in a hanging manner can be directly slid by the air cylinder, so that the door can be smoothly opened and closed.

In an embodiment, the guide member has a guide hole formed along a sliding direction of the door, and is configured to engage with the holders in a state where a portion of the holders are inserted through the guide hole from above, the door is supported at a portion lower than the guide member by the holders, and the holders are connected to a rod of the air cylinder at a portion higher than the guide member. The air cylinder serving as a drive source is disposed parallel to the door and substantially right above the door, so that force transmissibility is high, the door can be smoothly opened and closed, and the air cylinder can be housed neatly, so that the appearance is favorable.

In an embodiment, the guide member is formed to be hollow so as to enclose the air cylinder. Accordingly, dust entering from the air cylinder can be prevented so as to prevent disturbing opening and closing of the door.

In an embodiment, a lower end of the door is disposed without contact inside a recessed rail groove formed below the door. Opening and closing of the door can be prevented from being disturbed by dust and other dusty substances.

In an embodiment, an engagement surface of the guide member with the holders is inclined toward the guide hole. The door is supported substantially vertically, and force applied to the door has no bias, so that the door can be smoothly opened and closed.

With the configuration described above, an electronic balance with a windshield having a door to be automatically opened and closed smoothly can be provided.

Hereinafter, preferred embodiments relating to a configuration of the present disclosure are described with reference to the drawings. <FIG> is a perspective view of an electronic balance <NUM> with a windshield according to a first embodiment.

As illustrated in <FIG>, the electronic balance <NUM> with a windshield includes a balance main body <NUM>, a windshield <NUM> to be attached to the balance main body <NUM>, a connector <NUM> that connects the balance main body <NUM> and the windshield <NUM>, and a control panel <NUM>.

The balance main body <NUM> includes, on an upper surface thereof, a weighing pan <NUM> on which a specimen is placed. A control unit <NUM> that controls a weighing mechanism connected to the weighing pan <NUM> and the windshield <NUM> is disposed inside the balance main body <NUM>. Onto the upper surface of the balance main body <NUM>, a floor member <NUM> is fixed, a dust plate <NUM> is placed on an upper surface of the floor member <NUM>, and further, a ring-shaped windshield ring <NUM> is placed on the dust plate <NUM>. The dust plate <NUM> prevents a specimen spilling out of the weighing pan <NUM> from falling on the balance main body <NUM>, and the windshield ring <NUM> plays a role in preventing wind effects on the weighing pan <NUM>.

The windshield <NUM> is disposed on the upper surface of the balance main body <NUM> so as to enclose a periphery of the weighing pan <NUM>, and prevents air flow during weighing, for example, wind from an air conditioner, breath of a person at the time of weighing, and an air flow generated when a person walks, etc., from acting as a wind pressure on a load-applied portion centered on the weighing pan <NUM> and influencing weighing.

The windshield <NUM> has a bottomless box shape, and has a front glass <NUM> at a front surface, a box-shaped case <NUM> at a back portion, doors <NUM> at portions of left and right side walls, and an upper surface door <NUM> at the upper surface, and as a space defined by these, a weighing chamber <NUM> having a rectangular parallelepiped shape is formed inside.

The doors <NUM> can respectively move forward and rearward along rails 14a provided on a frame <NUM> as a frame member at a lower portion of the windshield <NUM>, and the door <NUM> can move forward and rearward along rails 20a provided in cylinder boxes <NUM> as frame members at an upper portion of the windshield <NUM>. The front glass <NUM> is fixed to the front sides of the frame <NUM> and the cylinder boxes <NUM> by fixing members such as bolts.

The front glass <NUM>, the upper surface door <NUM>, and the left and right doors <NUM> are made of transparent glass or resin so that an internal state can be observed. To each of the upper surface door <NUM> and the doors <NUM>, a handle <NUM> that assists sliding is attached.

The cylinder boxes <NUM> are provided to form the left and right upper sides of the windshield <NUM> having a substantially rectangular parallelepiped shape. In the cylinder box <NUM>, an air cylinder <NUM> that is a means for opening and closing the door <NUM> is housed. Inside the case <NUM>, a power chamber <NUM> is formed.

The control panel <NUM> is for operating the balance main body <NUM> and the windshield <NUM>, and is provided separately from the balance main body <NUM>. This is to prevent vibration caused by an operation such as pushing on a switch from influencing weighing. The control panel is separated from the balance main body, so that a user can freely arrange the control panel at a position easy to operate. The control panel <NUM> is connected to the balance main body <NUM> by a cable <NUM>. The control panel <NUM> and the balance main body <NUM> may be connected by wireless communication.

The control panel <NUM> includes, on an upper surface thereof, a display unit <NUM> to display weighing results and states, switches <NUM> for operation, and an infrared sensor <NUM>. The infrared sensor <NUM> is an opening and closing switch of the doors <NUM>, and only by holding a hand over the infrared sensor, can the doors <NUM> be automatically opened and closed. A press switch may be provided in place of the infrared sensor <NUM>, and a configuration in which both of a press switch and the infrared sensor <NUM> are provided is also preferable. To the infrared sensor <NUM>, a balance operating function other than the door <NUM> opening and closing function may be assigned. It is also possible that two left and right infrared sensors <NUM> are provided and configured to respectively open and close corresponding doors <NUM>.

The windshield <NUM> and the balance main body <NUM> are connected by the connector <NUM>. The windshield <NUM> receives electric power and command signals from the balance main body <NUM> through the connector <NUM>.

In the frame <NUM>, a pair of left and right attaching and detaching mechanisms <NUM> are provided. The attaching and detaching mechanisms <NUM> are described in detail. In the frame <NUM>, an engagement hole <NUM> is formed that penetrates through the frame to the inside, and in the engagement hole <NUM>, an engagement member <NUM> is inserted. The engagement member <NUM> is inserted through the engagement hole <NUM> and engaged with or disengaged from the floor member <NUM> fixed to a bottom surface of the balance main body <NUM>, and accordingly, the windshield <NUM> is attached to or detached from the balance main body <NUM>.

The engagement member <NUM> includes a flat plate <NUM> and a housing <NUM>. <FIG> is a plan view of the engagement member <NUM>, <FIG> is a bottom view of the engagement member <NUM>, <FIG> is a right side view of the engagement member <NUM>, <FIG> is a perspective view of the engagement member <NUM>, and <FIG> is a perspective view of the flat plate <NUM>.

The flat plate <NUM> is attached to the housing <NUM>, and directly engages with the floor member <NUM> fixed to the balance main body <NUM>. The flat plate <NUM> is made of a material with high strength such as a metal plate. The flat plate <NUM> is fixed to the housing <NUM> by a fixation means such as a machine screw <NUM> in a state where a contact portion 73a, which is the tip end portion, protrudes. The contact portion 73a is a portion that comes into contact with the floor member <NUM> of the balance main body <NUM>, and is formed to be wider than other portions to increase the contact area.

In the housing <NUM>, an end portion at the side opposite the end portion at the side from which the contact portion 73a protrudes is a grip portion 74a to be gripped at the time of an operation of inserting and pulling out the engagement member <NUM>.

At upper portions of side wall portions 74b of the housing <NUM>, eaves portions 74c overhanging to the outer sides of the side wall portions 74b are formed.

Holes are formed so as to become orthogonal to the side wall portions 74b of the housing <NUM>, and inside the holes, a pair of left and right lock pins <NUM> are disposed. Both of the lock pins <NUM> are energized so as to protrude to the outer sides of the side wall portions 74b (the arrow directions in <FIG>) by an elastic body such as a coil spring (not illustrated) interposed between the lock pins <NUM>.

Next, the engagement holes <NUM> provided in the frame <NUM> are described. <FIG> is an enlarged view of portion A in <FIG>, and illustrates a state where the engagement member <NUM> is pulled out from the engagement hole <NUM>. <FIG> is a sectional view taken along line VIII-VIII in <FIG>.

At two positions opposed to each other on the left and right wall portions of the frame <NUM>, the engagement holes <NUM> are formed. The engagement holes <NUM> are orthogonal to the side walls of the frame <NUM>, and are formed to penetrate through the frame <NUM>. The engagement holes <NUM> are guide holes to guide advancing/retreating movements of the engagement members <NUM>.

A front surface shape of the engagement hole <NUM> is a substantially I shape consisting of an upper horizontal portion 19a, a lower horizontal portion 19c, and a vertical portion 19b connecting both horizontal portions. The engagement hole <NUM> is configured so that the eaves portions 74c of the housing <NUM> are fitted into the upper horizontal portion 19a, the side wall portions 74b of the housing <NUM> are positioned at the vertical portion 19b, and the flat plate <NUM> is inserted through the lower horizontal portion 19c. Accordingly, the engagement member <NUM> is smoothly inserted and pulled out along the engagement hole <NUM> without slipping out of the engagement hole <NUM>.

In the vertical portion 19b of the engagement hole <NUM>, locking recess portions (19d and 19e) are formed at two positions in the depth direction. The locking recess portions (19d and 19e) are formed at a deepness at which they engage with the lock pin <NUM>, and when the engagement member <NUM> is inserted in and pulled out from the engagement hole <NUM>, the lock pins <NUM> of the engagement member <NUM> engage with either the locking recess portion 19d or 19e. Accordingly, the engagement member <NUM> is stopped and fixed at a predetermined position in the engagement hole <NUM>.

Subsequently, the floor member <NUM> of the balance main body <NUM> with which the windshield <NUM> directly engages is described with reference to <FIG>. The floor member <NUM> itself is a component conventionally attached to the balance main body <NUM>.

In the upper surface of the balance main body <NUM>, a through hole (not illustrated) is provided. This through hole communicates with the inside of the balance main body <NUM>, and makes the air pressure inside the balance main body <NUM> and the air pressure around the balance main body <NUM> equal to each other, and prevents weighing errors caused by an air pressure change. To prevent dust from entering from the through hole while making the through hole and the atmosphere communicate with each other, the floor member <NUM> is attached to the upper surface of the balance main body <NUM> in a state where the floor member is separated from the balance main body <NUM> by a spacer <NUM>.

The floor member <NUM> is disposed to be centered at the weighing pan <NUM>, and is fixed to the upper surface of the balance main body <NUM> by machine screws or the like. The floor member <NUM> is normally made of stainless steel, or a chromed steel material, etc. A casing constituting the balance main body <NUM> is formed of an aluminum die-casting or synthetic resin molding product, but if the weighing pan <NUM> is directly disposed on this casing, it becomes difficult to remove a specimen that fell onto the casing surface. Further, in the case where the casing is made of synthetic resin, depending on the kind of specimen, a situation in which the casing itself is dissolved by the specimen is assumed to occur. By disposing the floor member <NUM>, even if a specimen such as a liquid or powder falls, the floor member <NUM> is highly resistant to the specimen, and the surface of the floor member is machined to be flat and smooth by mirror-like finishing, so that the specimen can be easily wiped off. In addition, the material forming the floor member is a metal plate, so that its original physical strength is also extremely high. In the present embodiment, by locking the engagement members <NUM> to this floor member <NUM>, the windshield <NUM> is fixed to the balance main body <NUM>.

<FIG> are views each illustrating a fitting-through state of the engagement member <NUM> and the engagement hole <NUM>, and illustrate perspective views of the frame <NUM> from the inside of the windshield <NUM>. <FIG> are conceptual diagrams illustrating an engagement state between the floor member <NUM> and the engagement member <NUM>.

<FIG> and <NUM>(A) illustrate a state where the engagement member <NUM> is disengaged from the engagement hole <NUM>.

<FIG> and <NUM>(B) illustrate a state where the engagement member <NUM> is inserted in the engagement hole <NUM>, and the lock pins <NUM> are positioned at the locking recess portions 19e recessed in the engagement hole <NUM>. The lock pins <NUM> are energized so as to protrude outside by the coil spring not illustrated, and engage with the locking recess portions 19d (or 19e) and fix the engagement member <NUM> at the position of the locking recess portions. In this state, the contact portion 73a of the flat plate <NUM> is not in engagement with the floor member <NUM>, and the windshield <NUM> is detachable from the balance main body <NUM>.

<FIG> and <NUM>(C) illustrate a state where the engagement member <NUM> is further inserted in the engagement hole <NUM>, and the lock pins <NUM> are positioned at the locking recess portions 19d. The lock pins <NUM> engage with the locking recess portions 19d and fix the engagement member <NUM> in a state where the tip end of the flat plate <NUM> protrudes to the inside of the windshield <NUM>. Accordingly, the contact portion 73a of the flat plate <NUM> closely engages with a back surface of the floor member <NUM>, and by this engagement, the windshield <NUM> is firmly fixed to the balance main body <NUM>.

In the present embodiment, the windshield <NUM> has a door <NUM> automatic opening and closing function, however, a drive source and a drive mechanism for automatic opening and closing are all housed inside the windshield <NUM> in a form that does not influence weighing (described in detail later). The attaching and detaching mechanism <NUM> fixes the windshield <NUM> by using the floor member <NUM> conventionally provided, so that without making any modification to the balance main body <NUM> side, the windshield <NUM> can be fixed. Conventionally, a windshield with a door opening and closing function has a problem in which the degree of freedom of design is low because the balance and the windshield are configured and designed as an integrated body. In the present embodiment, the balance and the windshield are configured as separate bodies independent from each other, and the balance main body <NUM> and the windshield <NUM> can be designed separately, so that the degree of freedom of design is high. The balance main body <NUM> can be freely designed without restrictions in design caused by the windshield <NUM> and the addition of the door automatic opening and closing function.

A balance with a windshield having an automatic opening and closing function is expensive, however, when either the windshield or the balance main body malfunctioned, both of these became unusable, and this was uneconomical. In the present embodiment, a malfunctioning one can be immediately replaced with a new one, and this is economical. Also during repair, the other that is not malfunctioning can be continuously used.

Further, the windshield <NUM> is fixed by using the floor member <NUM> conventionally provided, so that if the conditions such as dimensions are met, the windshield <NUM> having the door automatic opening and closing function can be fitted to an existing electronic balance, and in addition, the windshield <NUM> can be firmly fixed and used, and this is highly convenient. Although the windshield <NUM> is freely attachable and detachable, the windshield <NUM> and the balance main body <NUM> can be firmly held and integrated, and are easy to carry around, and no troublesome assembling operations are required.

When the electronic balance <NUM> with a windshield is disposed inside a glovebox the opening of which is narrow, the electronic balance <NUM> with a windshield can be disassembled into the balance main body <NUM> and the windshield <NUM>, and these can be put into the glovebox separately, and further, they can be easily assembled inside the glovebox.

The cylinder box <NUM> has a cover 20b covering the upper surface and the side surfaces of the cylinder box. <FIG> is a plan view of the cylinder box <NUM> in a state where the cover 20b is removed, and is an explanatory view to describe the inside of the cylinder box <NUM>. <FIG> is a right side view of the windshield <NUM> in the state where the cover 20b is removed. <FIG> is a sectional view taken along line XIII-XIII in <FIG>, and is an explanatory view to illustrate the shape and operation of a holder <NUM>. <FIG> is a perspective view of the cylinder box <NUM> and the door <NUM>, and is an explanatory view to describe the structures of these.

Inside the cylinder box <NUM>, the air cylinder <NUM> is fixed. The air cylinder <NUM> is a double-acting type, and both of the forward and backward strokes of reciprocating motion of a piston <NUM> inside the air cylinder <NUM> are made by air pressure. Therefore, ports to feed air to the inside of the air cylinder <NUM> are provided at two positions. At the front side of the cylinder tube <NUM> having the piston <NUM> inside, a retreat-side port <NUM> for making the piston <NUM> move rearward by fed air is provided. In the same manner, at the rear side of the cylinder tube <NUM>, an advance-side port <NUM> for sending the piston <NUM> forward is provided.

Air tubes <NUM> connected to the respective ports pass through a hole 20c provided in a bottom surface 20f of the cylinder box <NUM> and connect to the power chamber <NUM> inside the case <NUM>. In the power chamber <NUM>, pumps serving as drive sources of the air cylinder <NUM> and solenoid valves to control the flow and stoppage of air are housed.

The power chamber <NUM> is formed by being separated from the weighing chamber <NUM> so as not to influence weighing with vibration, etc. Air intake and exhaust ports (not illustrated) formed in the power chamber <NUM> are directed in a direction opposite to the weighing chamber <NUM> so that air intake and exhaust do not influence weighing.

Conventionally, when for example, a rack-and-pinion or a rubber pulley is selected as a drive mechanism, a motor serving as a drive source is disposed close to the door from the viewpoint of transmission efficiency. However, in this case, vibration of the motor serving as a drive source is transmitted to the weighing chamber, so that there is concern that the vibration influences weighing. By selecting an air cylinder as a drive mechanism, it becomes unnecessary to dispose the air pump as a power source close to the door, and the air pump can be disposed at a free place. By providing the power chamber <NUM> in which the air pump is housed by separating to be away from the weighing chamber <NUM>, influences of vibration of the power source on weighing can be reduced.

The cylinder box <NUM> is formed to be hollow, and inside this, the air cylinder <NUM> is disposed parallel to the door <NUM> and fixed while being separated from the bottom surface 20f of the cylinder box <NUM>. The air cylinder <NUM> is disposed inside the cylinder box <NUM>, and this prevents dust entrance and transmission of air vibration from the air cylinder <NUM> to the weighing chamber <NUM>.

At front and rear end portions of the door <NUM>, holders <NUM> are disposed. The door <NUM> is vertically sandwiched by two U-shaped clamp portions 16a formed at upper and lower portions of the holder <NUM>, and held by being wrapped by the holder <NUM> consisting of a combination of the clamping portions 16a and a side surface portion 16b connecting the upper and lower clamping portions 16a. If the door <NUM> is simply clamped and hung down from above, there is a risk that the door <NUM> may fall off, however, since the door <NUM> is firmly held by the holder <NUM> by being wrapped by the holder <NUM>, there is no risk of falling off.

In the bottom surface of the cylinder box <NUM>, a guide hole 20d is formed in a front-rear direction that is a sliding direction of the door <NUM>. At a portion higher than the upper clamping portion 16a, a flange portion 16c is formed orthogonally to the door <NUM> (guide hole 20d). The flange portion 16c protruding leftward and rightward engages in this guide hole 20d and supports the door <NUM> in a hanging manner. Accordingly, the door <NUM> is disposed in a non-contact manner t with the rail 14a formed on the frame <NUM>, and held slidably along the guide hole 20d. When dust and sand, etc., enter the rail 14a, a problem occurs in which the sliding resistance when the door <NUM> opens or closes increases and it becomes difficult to open and close the door, however, this problem is prevented by hanging the door <NUM> itself from the upper portion.

In the holder <NUM> disposed at the front end of the door <NUM>, a coupling portion 16d is formed on an upper surface of the flange portion 16c. At the center of the coupling portion 16d, a coupling hole 16e is formed along the door opening and closing direction, and the tip end of a piston rod <NUM> extending from the piston <NUM> of the air cylinder <NUM> is fitted in this coupling hole 16e and fixed. By the piston <NUM> (piston rod <NUM>) connected to the door <NUM> through the holder <NUM> and by the piston <NUM> moving forward and rearward by air, the holder <NUM> slides along the guide hole 20d and the door <NUM> opens and closes. The air cylinder <NUM> is fixed while being separated from the bottom surface inside the cylinder box <NUM>, so that the air cylinder does not obstruct movements of the door <NUM>.

The air cylinder <NUM> serving as a drive source of the door <NUM> is disposed substantially right above the door <NUM> and parallel to the sliding direction of the door <NUM>. The holders <NUM> that support the door in a hanging manner support the door <NUM> by lower portions, and are connected at upper portions to the air cylinder <NUM>, and the air cylinder <NUM> opens and closes the door <NUM> by directly sliding the holders <NUM> that supports the door <NUM> in a hanging manner. The holder <NUM> on which the door is hung, specifically, the flange portion 16c that serves as a sliding portion when opening and closing the door <NUM> is disposed close to the air cylinder <NUM> serving as a drive mechanism. Further, only front and rear end portions of the door <NUM> are hung with the holders <NUM>, and a sliding area when the door <NUM> opens and closes is small, and sliding resistance when the door <NUM> opens and closes is also small. In the present embodiment, the holders <NUM> and the cylinder boxes <NUM>, and in addition, the doors <NUM> are also made of resin, so that they are light in weight and have small sliding resistance. With this configuration, force transmissibility from the air cylinder is high, the door <NUM> can be opened and closed with small force, and the door <NUM> can be smoothly opened and closed.

When the door of the windshield is opened and closed by using a conventional opening and closing mechanism, for example, a rubber pulley, in order to transmit power of the motor to the door having a certain degree of weight, the pulley at the door portion must be made large or the power of the motor must be made high. The balance is easily influenced by wind, and wind is easily produced by high-speed opening and closing of the door, so that in order also to decrease the opening and closing speed, the pulley must be made large for decreasing the speed. If the door is formed to be thin and light in weight, it is difficult to transmit power to the door and the motor is inevitably made large. Further, the motor needs to be disposed near (substantially, at the upper portion of) the door, and this disposition of a large-sized motor is awkward, and makes the appearance unsightly. By disposing the air cylinder <NUM> long in one direction along the door <NUM> at the upper portion of the door <NUM>, the windshield <NUM> can be formed into a substantially rectangular parallelepiped shape, and the appearance and configuration become simple.

<FIG> is a block diagram illustrating an opening and closing mechanism <NUM> of the left or right door <NUM> of the electronic balance <NUM> with a windshield. The opening and closing mechanism <NUM> is a mechanism to open and close the left or right door <NUM>, and another set of the components illustrated in <FIG> is present, and the components are the same, so that they are omitted in illustration. In the present embodiment, a pump to move forward (advance) the piston <NUM> of the air cylinder <NUM> and a pump to move rearward (retreat) the piston <NUM> are present separately.

Both of a first pressurization pump 62A and a second pressurization pump 62B are air pumps. These pumps are drive sources of the air cylinder <NUM>, and compress air and feed the compressed air to the air cylinder <NUM>, and move the piston <NUM> by air pressures to open and close the door <NUM>.

Outlet sides of a first one-way solenoid valve 66A and a second one-way solenoid valve 66B are opened to the atmosphere, and by opening and closing the valves, the flow and stoppage of air are controlled.

A first pressure sensor 64A monitors a pressure of air discharged from the first pressurization pump 62A, and a second pressure sensor 64B monitors a pressure of air discharged from the second pressurization pump 62B.

To the advance-side port <NUM> provided at the rear side of the air cylinder <NUM>, the first pressurization pump 62A is connected. This connection has a branch halfway, and the first pressure sensor 64A and the first one-way solenoid valve 66A are further connected. To the retreat-side port <NUM> provided at the front side of the air cylinder <NUM>, the second pressurization pump 62B is connected. This connection has a branch halfway, and the second pressure sensor 64B and the second one-way solenoid valve 66B are connected to this branch. These components are connected by the air tubes <NUM>, respectively.

Operations of the respective components of the opening and closing mechanism <NUM> are controlled by the control unit <NUM> of the balance main body <NUM>. For this reason, an instruction for the opening and closing mechanism <NUM> is performed through the balance main body <NUM>, however, a configuration is also preferable in which a windshield control unit to control the windshield <NUM> is provided inside the windshield <NUM>, and a command input is directly transmitted from the control panel <NUM> to the windshield control unit. In this case, a configuration is also preferable that a command input unit is provided in the windshield <NUM> itself so that the windshield <NUM> can be operated alone.

Next, operations of the respective components when the door <NUM> is automatically opened and closed are described. <FIG> is an operation chart of the opening and closing mechanism <NUM>.

First, in a "standard state" in which a user can manually open and close the door <NUM>, neither of the first pressurization pump 62A and the second pressurization pump 62B is activated, and the first one-way solenoid valve 66A and the second one-way solenoid valve 66B are open. Because neither of the pressurization pumps (62A and 62B) operates, and both of the one-way solenoid valves (66A and 66B) are opened and communicate with the atmosphere, so that no load is applied from the air cylinder <NUM>, and the door <NUM> can be smoothly manually opened and closed.

When a command to "open/close door" is input from the infrared sensor <NUM> of the control panel <NUM>, the control unit <NUM> commands the respective components to operate.

In a case of an "automatic opening operation" to open the door <NUM>, that is, in a case where the piston <NUM> of the air cylinder <NUM> is moved rearward, the second one-way solenoid valve 66B is closed, and pressurization of the second pressurization pump 62B is started. At this time, the first pressurization pump 62A is not activated, and the first one-way solenoid valve 66A is open, so that the piston <NUM> is moved rearward by an air pressure, and the door <NUM> is opened.

When the door <NUM> fully opens, the air pressure rapidly increases, so that when this change is detected by the second pressure sensor 64B, the second pressurization pump 62B is stopped, the second one-way solenoid valve 66B is opened, and the compressed air inside the air cylinder is released to the atmosphere, and the mechanism returns to the standard state.

In a case of an "automatic closing operation" to close the door <NUM>, that is, in a case where the piston <NUM> of the air cylinder <NUM> is moved forward, the first one-way solenoid valve 66A is closed, and pressurization of the first pressurization pump 62A is started. At this time, the second pressurization pump 62B does not operate, and the second one-way solenoid valve 66B is open, so that the piston <NUM> is moved forward by an air pressure, and the door <NUM> is closed.

When the door <NUM> fully closes, the air pressure rapidly increases again, so that when this change is detected by the first pressure sensor 64A, the first pressurization pump 62A is stopped, the first one-way solenoid valve 66A is opened, and the compressed air inside the air cylinder is released to the atmosphere, and the mechanism returns to the standard state.

On the other hand, when calibration is performed, the first one-way solenoid valve 66A and the second one-way solenoid valve 66B are closed. Both of the one-way solenoid valves (66A and 66B) are closed, the piston <NUM> can move neither forward nor rearward, and the door <NUM> is locked. This is to prevent the door from being unexpectedly opened during calibration operation and influencing calibration. After the calibration is finished, the first one-way solenoid valve 66A and the second one-way solenoid valve 66B are opened, and the mechanism returns to the standard state.

In this way, the door <NUM> is automatically locked during calibration operation. The door <NUM> may be configured to be locked according to a command from the switch <NUM>. Not only during calibration, the door <NUM> can also be locked during transportation.

Next, a flow of opening and closing operations of the door <NUM> is described with reference to the flowchart in <FIG>.

In Step S101, from the infrared sensor <NUM> of the control panel <NUM>, which is a switch to open and close the door <NUM>, a command signal to open/close the door <NUM> is input. When the signal is not input, the mechanism waits until the signal is input.

When a command is input, the process shifts to Step S102, and whether the door position is at a closed position or an open position is checked. In the present embodiment, the control unit <NUM> keeps a last opening/closing operation of the door <NUM> in memory, and makes determination according to the content. A configuration is also possible in which a position sensor is provided to check the position of the door <NUM>.

First, a case where the door <NUM> is at the closed position (Steps S103 to S108) is described.

The process shifts to Step S103, and in order to open the door <NUM> that is at the closed position, the "automatic opening operation" for the door <NUM> is performed. In detail, the second one-way solenoid valve 66B is closed, and operation of the second pressurization pump 62B is started. At this time, the first one-way solenoid valve 66A is left open, and the first pressurization pump 62A is not activated (refer to <FIG>).

Next, the process shifts to Step S104, and whether the door <NUM> has started to move is checked. When the door <NUM> starts to move, the air pressure rapidly decreases, so that when a value of the second pressure sensor 64B rapidly decreases within a predetermined time, for example, within one second, it is determined that the door <NUM> has started an opening operation. When the door <NUM> does not start to move within the predetermined time, the control unit <NUM> determines that "door <NUM> has already been opened," and the process shifts to Step S109, and then, the "automatic closing operation" is started (described later). Alternatively, when a value of the second pressure sensor 64B exceeds a predetermined value, it is also possible to determine that the door has not started to move. A last position of the door <NUM> is kept in memory, however, in the present embodiment, manual opening and closing are also possible, and the position of the door <NUM> is moved by a user in some cases. Against such a case or an erroneous determination of the door <NUM> position, security is provided by this Step S104.

When movement of the door <NUM> is started, the process shifts to Step S105, and whether the opening operation of the door <NUM> has been finished is checked. When the movement of the door <NUM> is completed, the air pressure increases again, and when a value of the second pressure sensor 64B increases again within a predetermined time, it is determined that the opening operation of the door <NUM> has been finished. When the value of the second pressure sensor 64B does not increase within the predetermined time, air leakage or malfunction is suspected, so that to perform error handling, the process shifts to Step S106.

In Step S106, as the error handling, a warning tone is produced, an error is displayed on the display unit <NUM>, the operation of the second pressurization pump 62B is stopped, the second one-way solenoid valve 66B is opened, and the mechanism is brought to an emergency stop.

When completion of the opening operation of the door <NUM> is confirmed according to an air pressure increase, the process shifts to Step S107, the operation of the second pressurization pump 62B is stopped, the second one-way solenoid valve 66B is opened, and the automatic operation is normally finished.

Last, the process shifts to Step S108, the mechanism returns to the standard state, and manual opening and closing are enabled.

Next, a case (S109 to S113) where the door <NUM> is at the open position in Step S102 is described.

The process shifts to Step S109, and in order to close the door <NUM> that is at the open position, the "automatic closing operation" of the door <NUM> is performed. In detail, the first one-way solenoid valve 66A is closed, and operation of the first pressurization pump 62A is started. At this time, the second one-way solenoid valve 66B is left open, and the second pressurization pump 62B is not activated (refer to <FIG>).

Next, the process shifts to Step S110, and whether the door <NUM> has started to move is checked. As in Step S104, when a value of the first pressure sensor 64A rapidly decreases within a predetermined time, it is determined that the door <NUM> has started a closing operation. When the door <NUM> does not start to move within the predetermined time, the control unit <NUM> determines that "the door <NUM> has already been closed," and the process shifts to Step S103, and then, the "automatic opening operation" is started. Like Step S104, this step S110 also provides security against a case where the door <NUM> position is moved by manual opening and closing and an erroneous determination.

When movement of the door <NUM> is started, the process shifts to Step S111, and whether the closing operation of the door <NUM> has been finished is checked. Completion of the movement of the door <NUM> is determined when the value of the first pressure sensor 64A increases again within a predetermined time. When the value of the first pressure sensor 64A does not increase within the predetermined time, to perform error handling again, the process shifts to Step S112. When completion of the door closing operation is confirmed according to an increase in value of the first pressure sensor 64A within the predetermined time, the process shifts to Step S113.

In Step S112, as error handling, a warning tone is produced, an error is displayed on the display unit <NUM>, the operation of the first pressurization pump 62A is stopped, the first one-way solenoid valve 66A is opened, and the mechanism is brought to an emergency stop.

When an increase in value of the first pressure sensor 64A within the predetermined time is confirmed, the process shifts to Step S113, the operation of the first pressurization pump 62A is stopped, and the first one-way solenoid valve 66A is opened.

Last, the process shifts to step S108, the mechanism returns to the standard state, and manual opening and closing are enabled.

Step S111 and Step S105 double as a safety function to prevent finger pinching, etc. When the door <NUM> is about to be automatically closed or opened, even if one of the operator's fingers is pinched in the door <NUM>, a specimen or the like is caught in the door <NUM>, or trouble occurs in the movement of the door <NUM> and the movement is forcibly stopped, the air pressure increases, so that this air pressure increase is detected by the first pressure sensor 64A (or the second pressure sensor 64B), and the operation of the door <NUM> is immediately stopped, both of the one-way solenoid valves (66A and 66B) are made to communicate with the atmosphere, and the load on the door <NUM> is eliminated, and safety is secured.

When one pressurization pump operates, the other pressurization pump does not operate, and only one solenoid valve is closed, and the other solenoid valve is opened and communicates with the atmosphere. When the pump that has been operating stops, the closed solenoid valve opens and communicates with the atmosphere. In other words, all of the one-way solenoid valves are configured to open and communicate with the atmosphere when the pressurization pumps stop. After the door <NUM> is automatically opened/closed, air is released to the atmosphere, and the load on the door <NUM> is eliminated, and it becomes possible to smoothly manually move the door <NUM>. The door <NUM> is automatically openable and closable, however, after it is automatically opened/closed, manual opening and closing are enabled immediately without a special operation. A mechanism to disconnect the drive source and the drive mechanism for manual/automatic switching and an operation therefor itself are unnecessary, so that extremely high usability is obtained.

When the door is opened/closed by using resistance of rubber as in the case of using a conventional mechanism, for example, a pulley or the like, a problem occurs in which even when the door is to be manually opened, the door is heavy or cannot be opened due to a load (sliding resistance) caused by interlock of the rubber with the drive source. In the present embodiment, as a door <NUM> opening and closing mechanism, an air cylinder is employed, and after finishing opening and closing, all of the valves are opened to communicate with the atmosphere, so that no air pressure is applied and the door can be opened and closed smoothly, and even when the door is manually opened/closed, there is no risk of breakage and malfunction.

The door can be manually opened and closed, so that the door <NUM> can be stopped at an arbitrary position, and the degree of freedom in use is high. Even when the door <NUM> is at a halfway position, according to an input of a command from the infrared sensor <NUM>, the door <NUM> is closed or opened.

Also when the door opening and closing mechanism malfunctions or degrades with age, the door cannot be opened or closed with a conventional mechanism, however, by using the air cylinder <NUM>, even when a packing to prevent air leakage degrades with age, only the door opening and closing speed decreases due to the air leakage, and even when malfunction occurs, manual opening and closing are possible, and this is highly convenient.

When weighing is to be performed by using a space around the balance main body <NUM>, the windshield <NUM> can be detached, and when the windshield <NUM> is attached to the balance main body <NUM>, the doors <NUM> of the windshield can be opened and closed either automatically or manually, so that the degree of freedom for use is high.

The mechanism is also configured so that by switching between the "automatic opening operation" and the "automatic closing operation" according to monitoring of the air pressure, opening/closing of the doors <NUM> is secured even when an erroneous operation occurs or the door <NUM> is at a halfway position, and the automatic opening operation or automatic closing operation is stopped when an abnormality occurs, and therefore, a high degree of safety and a high degree of usability are obtained.

<FIG> is a perspective view of a balance <NUM> with a windshield according to a second embodiment. <FIG> is a block diagram of an opening and closing mechanism <NUM> of the balance <NUM> with a windshield according to the second embodiment.

The balance <NUM> with a windshield according to the second embodiment is configured in common with the electronic balance <NUM> with a windshield according to the first embodiment except that the balance <NUM> with a windshield includes an automatic calibration mechanism <NUM> that performs automatic calibration inside the balance main body <NUM> and that the configuration of the opening and closing mechanism <NUM> serving as a mechanism to automatically open and close the door is different. Unlike the opening and closing mechanism <NUM> of the first embodiment, the opening and closing mechanism <NUM> of the present embodiment serving as a mechanism to open and close the door is provided not independently between the left and the right. Therefore, left and right doors are described as a left door 11A and a right door 11B. Left and right air cylinders for opening and closing these doors are distinguished as a left air cylinder 40A and a right air cylinder 40B. Each of the air cylinders (40A/ 40B) includes a retreat-side port (46A/46B) and an advance-side port (44A/44B) to take in air, and a piston (41A/41B).

As illustrated in <FIG>, the left air cylinder 40A and the right air cylinder 40B shares one pressurization pump 62C as a drive source. One pressure sensor 64C monitors the pressure of air discharged from the pressurization pump 62C. Outlet sides of all of five one-way solenoid valves (66C, 66D, 66E, 66F, and <NUM>) are opened to the atmosphere. Two-way solenoid valves (68C, 68D, 68E, 68F, and <NUM>) provided in the present embodiment each have two connect ports, and inlet sides are each connected to the pressurization pump 62C, and outlet sides are each connected to the left air cylinder 40A, the right air cylinder 40B, or an air bag <NUM> to control the flow and stoppage of air.

To the advance-side port 44A provided at the rear side of the left air cylinder 40A, the first two-way solenoid valve 68C is connected. This connection has a branch halfway, and the first one-way solenoid valve 66C is also connected. To the retreat-side port 46A provided at the front side of the left air cylinder 40A, the second two-way solenoid valve 68D is connected, and this connection has a branch halfway, and the second one-way solenoid valve 66D is also connected.

In the right air cylinder 40B, in the same manner as described above, to the advance-side port 44B provided at the rear side, the third two-way solenoid valve 68E and the third one-way solenoid valve 66E are connected, and to the retreat-side port 46B provided at the front side, the fourth two-way solenoid valve 68F and the fourth one-way solenoid valve 66F are connected.

The automatic calibration mechanism <NUM> automatically calibrates the balance <NUM> with a windshield by loading and unloading a built-in weight <NUM> onto and from the balance by inflation and deflation of the air bag <NUM>. Automatic calibration using an air bag is disclosed in detail in <CIT>. To the air bag <NUM>, the fifth two-way solenoid valve <NUM> and the fifth one-way solenoid valve <NUM> are connected.

<FIG> illustrates operations of the respective components to operate the left door 11A, the right door 11B, and the built-in weight <NUM> of the automatic calibration mechanism <NUM>.

As illustrated in <FIG>, in a "standard state" where the respective functions are not activated at all, the pressurization pump 62C does not operate, and all of the one-way solenoid valves (66C, 66D, 66E, 66F, and <NUM>) are opened, and all of the two-way solenoid valves (68C, 68D, 68E, 68F, and <NUM>) are closed. In this state, both of the left door 11A and the right door 11B can be manually opened and closed.

First, automatic opening and closing of the left door 11A are described. In the case of an "automatic opening operation" of the left door 11A, that is, when the piston 41A (and the left door 11A connected to this piston) is moved rearward, the second one-way solenoid valve 66D is closed, the second two-way solenoid valve 68D is opened, and pressurization of the pressurization pump <NUM> is started. At this time, air passes through the opened second two-way solenoid valve 68D, and the piston 41A is moved rearward by an air pressure, and the left door 11A is opened.

When the left door 11A fully opens, the air pressure rapidly increases, so that when this change is detected by the pressure sensor 64C, the pressurization pump 62C is stopped, the second two-way solenoid valve 68D is closed, the second one-way solenoid valve 66D is opened, compressed air inside the left air cylinder 40A is released to the atmosphere, the pressure inside the left air cylinder 40A decreases to the atmospheric pressure, and the mechanism returns to the standard state.

In the case of an "automatic closing operation" of the left door 11A, that is, when the piston 41A (and the left door 11A connected to this piston) is moved forward, the first one-way solenoid valve 66C is closed, the first two-way solenoid valve 68C is opened, and pressurization of the pressurization pump 62C is started. Air passes through the opened first two-way solenoid valve 68C, and by the air pressure, the piston 41A is moved forward, and the left door 11A is closed.

When the left door 11A fully closes, the air pressure rapidly increases, so that when this change is detected by the pressure sensor 64C, the pressurization pump 62C is stopped, the first two-way solenoid valve 68C is closed, the first one-way solenoid valve 66C is opened, and compressed air inside the left air cylinder 40A is released to the atmosphere, and the pressure inside the left air cylinder 40A decreases to the atmospheric pressure, and the mechanism returns to the standard state.

The same applies to the right door 11B, and an "automatic opening operation" and an "automatic closing operation" are performed through the same operations in which the left air cylinder 40A corresponds to the right air cylinder 40B, the piston 41A corresponds to the piston 41B, the first one-way solenoid valve 66C corresponds to the third one-way solenoid valve 66E, the first two-way solenoid valve 68C corresponds to the third two-way solenoid valve 68E, the second two-way solenoid valve 68D corresponds to the fourth two-way solenoid valve 68F, and the second one-way solenoid valve 66D corresponds to the fourth one-way solenoid valve 66F.

Further, an operation of the automatic calibration mechanism <NUM> when the control unit <NUM> receives a command to automatically calibrate the balance is as follows.

First, in order to inflate the air bag <NUM> and load the built-in weight <NUM> onto the balance, all of the one-way solenoid valves (66C, 66D, 66E, 66F, and <NUM>) are closed, the fifth two-way solenoid valve <NUM> is opened, and pressurization of the pressurization pump 62C is started. Other two-way solenoid valves (68C, 68D, 68E, and 57F) connected to the pressurization pump 62C are all closed, so that air passes through the fifth two-way solenoid valve <NUM> and inflates the air bag <NUM>. By the inflation of the air bag <NUM>, the built-in weight <NUM> is loaded onto the balance. When the air bag <NUM> is fully inflated, the air pressure rapidly increases, so that when this is detected by the pressure sensor 64C, the pressurization pump 62C is stopped.

When the built-in weight <NUM> with a known mass is weighed and the calibration process ends, then, in order to unload the built-in weight <NUM> from the balance, the fifth one-way solenoid valve <NUM> is opened, and the fifth two-way solenoid valve <NUM> is closed. Accordingly, when the air that inflated the air bag <NUM> passes through the fifth one-way solenoid valve <NUM> and is released to the atmosphere, the air bag <NUM> gradually deflates, and the built-in weight <NUM> is unloaded from the balance. The remaining one-way solenoid valves (66C, 66D, 66E, and 66F) are opened, and the mechanism returns to the standard state.

During the calibration operation, all of the one-way solenoid valves (66C, 66D, 66E, 66F, and <NUM>) are closed, so that air cannot move, and the left door 11A and the right door 11B are locked. When the calibration operation ends, the left door 11A and the right door 11B are unlocked, and become manually openable and closable.

By locking the doors during automatic calibration, the operator is prevented from opening the left door 11A or the right door 11B by mistake without noticing automatic calibration, and causing influence on calibration.

In the balance <NUM> with a windshield according to the second embodiment, the pressurization pump 62C is used as a drive source shared by the left and right air cylinders (30A and 30B), and accordingly, the number of components can be reduced to be less than in the first embodiment, and the cost can be reduced. A pressurization pump as a drive source that raises and lowers a built-in weight incorporated in the balance at the time of automatic calibration, and the pressurization pump 62C, are configured as a shared one, and accordingly, the number of components can be further reduced.

<FIG> is a block diagram of an opening and closing mechanism <NUM> for a balance <NUM> with a windshield according to a third embodiment. The balance <NUM> with a windshield is configured in common with the balance <NUM> with a windshield according to the second embodiment except that an opening and closing mechanism <NUM> is different.

As illustrated in <FIG>, the opening and closing mechanism <NUM> of the balance <NUM> with a windshield includes a right air cylinder 40I to open and close the right door 11B, a left air cylinder <NUM> to open and close the left door 11A, and an automatic calibration mechanism <NUM>. A common drive source shared by these components is a pressurization/decompression pump <NUM>.

The pressurization/decompression pump <NUM> can perform both pressurization and decompression of air. The right air cylinder 40I and the left air cylinder <NUM> are double-acting air cylinders for the pressurization/decompression pump, and each of the air cylinders is provided with only one port (45I/<NUM>) at the rear side. In response to pressurization of the pressurization/decompression pump <NUM>, a piston <NUM> inside the left air cylinder <NUM> moves forward and the left door 11A closes, and in response to decompression of the pressurization/decompression pump <NUM>, the piston <NUM> moves rearward and the left door 11A opens. The same applies to the right air cylinder 40I.

The pressure sensor 64J monitors an air pressure inside a connected air tube to prevent the air pressure from becoming equal to or more than a set upper limit value or becoming equal to or lower than a set lower limit value. Outlet sides of all of the three one-way solenoid valves (<NUM>, 66I, and 66J) are opened to the atmosphere. Each of the two-way solenoid valves (<NUM>, 68I, and 68J) has two connect ports, and the inlet sides are connected to the pressurization/decompression pump <NUM>, and the outlet sides are connected to the left air cylinder <NUM>, the right air cylinder 40I, and the air bag <NUM>, respectively, to control the flow and stoppage of air.

To the port <NUM> of the left air cylinder <NUM>, the first two-way solenoid valve <NUM> is connected. This connection has a branch halfway, and the first one-way solenoid valve <NUM> is also connected. Similarly, to the port 45I of the right air cylinder 40I, the second two-way solenoid valve 68I and the second one-way solenoid valve 66I are connected in the same manner. To the air bag <NUM> of the automatic calibration mechanism <NUM>, the third one-way solenoid valve 66J and the third two-way solenoid valve 68J are connected.

In a standard state where the respective functions are not activated at all, the pressurization/decompression pump <NUM> does not operate, and all of the two-way solenoid valves (<NUM>, 68I, and 68J) are closed, and all of the one-way solenoid valves (<NUM>, 66I, and 66J) are opened so as to be open to the atmosphere. In this state, both of the left door 11A and the right door 11B can be manually opened and closed.

First, automatic opening and closing of the left door 11A are described. In the case of an "automatic opening operation" of the left door 11A, that is, when the piston <NUM> (and the left door 11A connected to this piston) inside the left air cylinder <NUM> is moved rearward, the first one-way solenoid valve <NUM> is closed, the first two-way solenoid valve <NUM> is opened, and decompression of the pressurization/decompression pump <NUM> is started. Accordingly, the pressure inside the left air cylinder <NUM> becomes low, and the piston <NUM> moves rearward and the left door 11A is opened.

When the left door 11A is opened, the air pressure rapidly decreases, so that when this decrease is detected by the pressure sensor 64J, the pressurization/decompression pump <NUM> is stopped, the first two-way solenoid valve <NUM> is closed, and the first one-way solenoid valve <NUM> is opened, and the mechanism returns to the standard state.

In the case of an "automatic closing operation" of the left door 11A, that is, when the piston <NUM> is moved forward, the first one-way solenoid valve <NUM> is closed, the first two-way solenoid valve <NUM> is opened, and pressurization of the pressurization/decompression pump <NUM> is started. Accordingly, the pressure inside the left air cylinder <NUM> becomes high, and the piston <NUM> is pushed forward by an air pressure, and the left door 11A is closed.

When the left door 11A is closed, the air pressure rapidly increases, so that when this increase is detected by the pressure sensor 64J, the pressurization/decompression pump <NUM> is stopped, the first two-way solenoid valve <NUM> is closed, the first one-way solenoid valve <NUM> is opened, and the mechanism returns to the standard state.

An "automatic opening operation" and an "automatic closing operation" of the right door 11B are the same as described above, and are performed through the same operations in which the left air cylinder <NUM> corresponds to the right air cylinder 40I, the first one-way solenoid valve <NUM> corresponds to the second one-way solenoid valve 66I, and the first two-way solenoid valve <NUM> corresponds to the second two-way solenoid valve 68I.

Further, an operation of the automatic calibration mechanism <NUM> to be performed when the control unit <NUM> receives a command to automatically calibrate the balance is as follows.

First, in order to inflate the air bag <NUM> and load the built-in weight <NUM> onto the balance, all of the one-way solenoid valves (<NUM>, 66I, and 66J) are closed, the third two-way solenoid valve 68J is opened, and pressurization of the pressurization/decompression pump <NUM> is started. Since other two-way solenoid valves (<NUM> and 68I) connected to the pressurization/decompression pump <NUM> are closed, when air passes through the third two-way solenoid valve 68J and inflates the air bag <NUM>, due to the inflation of the air bag <NUM>, the built-in weight <NUM> is loaded onto the balance. When the air bag <NUM> is fully inflated, the air pressure rapidly increases, so that when this increase is detected by the pressure sensor 64J, the pressurization/decompression pump <NUM> is stopped.

When the built-in weight <NUM> with a known mass is weighed and the calibration process ends, then, in order to unload the built-in weight <NUM> from the balance, the third one-way solenoid valve 66J is opened, and the third two-way solenoid valve 68J is closed. Accordingly, when the air that inflated the air bag <NUM> passes through the third one-way solenoid valve 66J and is released to the atmosphere, the air bag <NUM> gradually deflates, and the built-in weight <NUM> is unloaded from the balance. The remaining one-way solenoid valves (<NUM> and 66I) are opened, and the mechanism returns to the standard state.

During the calibration operation, all of the one-way solenoid valves (<NUM>, 66I, and 66J) are closed, so that air cannot move, and the left and right doors (11A and 11B) are locked. When the calibration operation ends, the left and right doors (11A and 11B) are unlocked, and become manually openable and closable.

By using the pressurization/decompression pump <NUM> as a common drive source for the respective components of the balance <NUM> with a windshield, the number of components can be reduced to be further less than that of the balance <NUM> with a windshield of the second embodiment and assembly man-hours can be reduced.

Preferred modifications with respect to the embodiments described above are described. The same components as in the embodiments described above are provided with the same reference signs, and descriptions of these are omitted.

<FIG> illustrates a modification of shapes of the cylinder box <NUM> and the holder <NUM>. A bottom surface 20f of the cylinder box <NUM> which serves as an engagement surface to engage with the door <NUM> is inclined toward the guide hole 20d. A bottom surface of the flange portion 16c which serves as an engagement surface to engage with the cylinder box <NUM> is formed to be inclined at the same angle as the angle of the bottom surface 20f. The inclination angles of the bottom surfaces 20f (and the bottom surface of the flange portion 16c) at the left and right of the guide hole 20d are equal to each other, and the door <NUM> maintains a substantially vertical posture. Due to the inclination of the engagement surface toward the guide hole 20d, the door <NUM> easily maintains its posture in the vertical direction.

<FIG> is a modification in which, for door position detection, position sensors are used instead of the pressure sensors. At the fully opened position and the fully closed position of the door <NUM>, photointerrupters <NUM> are provided as position sensors. Each photointerrupter <NUM> has a slit 92a, and in alignment with the position of the slit 92a, a projection portion 16f is formed on the coupling portion 16d of the holder <NUM>. In the slit 92a, a light emitting unit and a light receiving unit facing each other are provided, and by detecting, by the light receiving unit, interruption of light from the light emitting unit by the projection portion 16f, a position of the door <NUM> is checked.

Claim 1:
An electronic balance (<NUM>) comprising:
a balance main body (<NUM>) including a weighing mechanism connected to a weighing pan (<NUM>);
a windshield (<NUM>) configured to form a weighing chamber (<NUM>) by covering the weighing pan (<NUM>); and
a slidable door (<NUM>) provided in the windshield (<NUM>) and constituting a portion of the weighing chamber (<NUM>);
characterized in that
the electronic balance (<NUM>) further comprising:
holders (<NUM>) disposed at front and rear end portions of the door (<NUM>) configured to support the door (<NUM>) from an upper portion in a hanging manner;
a guide member (<NUM>) configured to engage with the holders (<NUM>) and slidably support the holders (<NUM>); and
an air cylinder (<NUM>) connected to the holders (<NUM>) and configured to slide the door (<NUM>) through the holders (<NUM>)