Patent Description:
The invention relates to control panel unit having a closed internal space for use in a machine tool.

It is known that a control panel unit for a machine tool such as a lathe is provided with a cooling device to prevent overheating of a control device arranged in the internal space. When the cold outside air is taken into the internal space, an oil filter is necessarily used to catch the oil mist produced from the lubricant. The filter is necessarily often exchanged to keep desired cooling efficiency. A heat exchanger or a heat sink as a cooling alternative would make the control panel unit larger in size and higher in cost. Another cooling device using a fan is proposed in <CIT> wherein the outside air is not taken into the internal space. <CIT> discloses a control panel unit according to the preamble of claim <NUM> in which a cooling fan is provided that actively sucks outside air into a case of the control panel and in which heat is discharged through exhaust ports at the case's ceiling.

According to the publication, the control panel unit comprises a control panel box containing a control device therein and a cooling space member cooperating with a ceiling plate of the control panel box to form a cooling space box entirely covering the control panel box from above. The control panel unit further comprises a side air passage member cooperating with a side plate of the control panel box to form a vertical air passage. The ceiling plate of the control panel box has an air outlet having a circulation fan. The vertical passage connects the cooling space with an air inlet. The internal air in the control panel box enters the cooling space through the air outlet, passes down the vertical passage, and then returns to the control panel box through the air inlet.

In the control panel unit disclosed in the publication, however, the cooling space is provided entirely over the control panel box, making the control panel unit larger in vertical size. Such problem resides in a control panel unit for any type of a machine tool.

The problem underlying the present invention is therefore to downsize a control panel unit for use in a machine tool.

This problem is solved by the subject-matter of claim <NUM>.

The present invention can downsize a control panel unit for use in a machine tool.

Hereinafter, an embodiment of the present invention will be described.

Technology included in the invention will be described with reference to <FIG>. The drawings only schematically show an example of the invention. They may have a mismatch to each other due to different maginification in each direction. Each element denoted by a symbol is only an example.

(Embodiment <NUM>) A control panel unit <NUM> for use in a machine tool <NUM> of an embodiment of the invention comprises a casing <NUM>, a duct <NUM>, and a fan <NUM>. The casing <NUM> is provided with an openable door <NUM> to close an internal space <NUM> in which a control device <NUM> is arranged. The duct <NUM> has a groove <NUM> and a ventilation opening <NUM>. One end of the groove <NUM> is closed and the other end thereof is open to the internal space <NUM>. The closed end of the groove <NUM> may be referred to as a closed end <NUM>. The open end of the groove <NUM> may be referred to as an open end <NUM>. The ventilation opening <NUM> is provided nearer the closed end <NUM> to connect the groove <NUM> with the internal space <NUM>. The duct <NUM> is fixed to an inner wall <NUM> of the casing <NUM> in such manner as the groove <NUM> faces the inner wall <NUM> of the casing <NUM>. The fan <NUM> is mounted on the ventilation opening <NUM>. The air (Ar) in the internal space <NUM> is taken into the groove <NUM> enclosed by the inner wall <NUM> and the duct <NUM> when the fan <NUM> is operated.

The open end <NUM> of the groove <NUM> of the duct <NUM> is open to the internal space <NUM>. The duct <NUM> is shorter than the inner wall <NUM> of the casing <NUM> with respect to an AX1 direction of the groove <NUM>. The air (Ar) in the internal space <NUM> is taken into the groove <NUM> enclosed by the inner wall <NUM> and the duct <NUM> when the fan <NUM> is operated. For example, the air (Ar) in the internal space <NUM> may pass along the inner wall <NUM> of the casing <NUM>, enter the groove <NUM> through the open end <NUM> thereof, and then flow out of the groove <NUM> toward the internal space <NUM> through the ventilation opening <NUM>. For example, the air (Ar) in the internal space <NUM> may enter the groove <NUM> through the ventilation opening <NUM> and flow out of the groove <NUM> toward the internal space <NUM> through the open end <NUM> thereof.

The exterior of the casing <NUM> is exposed to the outside air of lower temperature. Heat energy of the air passing down the groove <NUM> is discharged to the outside air through the casing <NUM>. The air flow is accelerated on the inner wall <NUM> of the casing <NUM> when passing down the groove <NUM>. The faster air flow improves the heat transfer coefficient. Heat radiation to the outside air is thereby further improved. The internal space of the control panel unit can be cooled without an expensive heat exchanger or heat sink. The duct <NUM> can be made shorter than the inner wall <NUM> of the casing <NUM> with respect to the AX1 direction of the groove <NUM>. The invention provides efficient heat radiation from the control panel unit without providing a cooling space box entirely covering the control panel box from above. The invention can downsize the control panel unit.

The closed internal space may be a space at least inhibiting dust or oil mist. Air flow to and from the outside is not necessarily totally cut off. The internal space connects with the outside when the door is opened. Accordingly, the closed internal space may be a space at least inhibiting dust or oil mist when the door is closed. Air flow to and from the outside is not necessarily totally cut off when the door is closed. The groove is open to the internal space to the extent that part of the internal space exists between the inner wall of the casing and the open end of the groove. The ventilation opening is nearer the one end of the groove than the other end thereof to the extent that the shortest distance between the ventilation opening and the one end of the groove is shorter than the shortest distance between the ventilation opening and the other end of the groove. The above remarks may be also applied to the following embodiments.

(Embodiment <NUM>) The inner wall <NUM> may comprise a bottom <NUM>, a ceiling <NUM>, and an upright wall <NUM> connecting the bottom <NUM> and the ceiling <NUM>. The duct <NUM> may be fixed on at least one of the upright wall <NUM> and the ceiling <NUM>. Particularly, the duct <NUM> may be nearer the ceiling <NUM> than the bottom <NUM> when mounted on the upright wall <NUM>. The upper air in the internal space <NUM> is likely higher in temperature than the lower air. The duct attached in a higher position provides further efficient heat radiation from the control panel unit. The invention can further downsize the control panel unit. The duct is nearer the ceiling than the bottom to the extent that the shortest distance between the duct and the ceiling is shorter than the shortest distance between the duct and the bottom. The above remark may be also applied to the following embodiments.

According to the present invention, the fan <NUM> comprises an exhaust fan <NUM> and an intake fan <NUM>. The exhaust fan <NUM> may discharge the air from the groove <NUM> to the internal space <NUM> through the ventilation opening <NUM>. The intake fan <NUM> may suck the air from the internal space <NUM> into the groove <NUM> through the ventilation opening <NUM>. The duct <NUM> comprises an exhaust duct <NUM> and an intake duct <NUM>. The exhaust duct <NUM> is provided with the exhaust fan <NUM>. The intake duct <NUM> is provided with the intake fan <NUM>. The intake duct <NUM> is fixed on the internal wall <NUM> in such manner as the exhaust fan <NUM> faces the intake fan <NUM>.

The air (Ar) in the internal space <NUM> is taken into the groove <NUM> of the exhaust duct <NUM> through the open end <NUM> by the operation of the exhaust fan <NUM>. The air passing down the groove <NUM> is discharged to the internal space <NUM> through the ventilation opening <NUM>. The air is then taken into the groove <NUM> of the intake duct <NUM> through the ventilation opening <NUM> by the operation of the intake fan <NUM>. The air passing down the groove <NUM> is discharged to the internal space <NUM> through the open end <NUM>. A wider air circulation flow C1 is generated in the casing <NUM>. Heat energy of the air in the internal space <NUM> is widely radiated to the outside air through the casing <NUM>. The embodiment provides further efficient heat radiation from the control panel unit. The invention can further downsize the control panel unit.

The duct <NUM> may be detachable with respect to the internal wall <NUM>. The duct may be attached in different positions according to the control panel unit <NUM>. The embodiment provides further efficient heat radiation according to the control panel unit. The invention can further downsize the control panel unit.

The control device <NUM> may comprise an amplifier <NUM> which activates a driven unit. An upper end 200a of the fan <NUM> may be positioned above un upper end 32a of the amplifier <NUM>. An amplifier produces a large amount of heat. Most amplifiers suck in the air from below and discharge it from above. For example, the air having higher temperature discharged toward above is sucked in the groove <NUM> of the duct <NUM> by the operation of the intake fan <NUM>. Heat energy of the air is efficiently radiated to the outside through the casing <NUM>. For example, the air having lower temperature in the groove <NUM> of the duct <NUM> is exhausted to the internal space <NUM> above the amplifier <NUM> by the operation of the exhaust fan <NUM>. The air of higher temperature discharged from the amplifier <NUM> is not allowed to stay. The embodiment provides further efficient heat radiation from the control panel unit. The invention can further downsize the control panel unit.

<FIG> is an illustration of the control panel unit <NUM> whose door <NUM> is opened. The illustration is only a simplified example for explanation of the invention. The invention is not limited thereto.

The machine tool <NUM> comprises a machining unit <NUM> and the control panel unit <NUM> which controls the operation of the machining unit <NUM>. The machine tool <NUM> may be an NC (numerical control) lathe. The NC lathe may comprise a headstock having a main spindle for chucking a workpiece, a tool post provided with a tool applied to the workpiece, a driving unit which relatively moves the headstock and the tool post, and a lubricant supplier for the workpiece. The control panel unit <NUM> may comprise the control device <NUM> including a printed circuit board <NUM> and the amplifier <NUM>. The printed circuit board <NUM> may have a circuit including a CPU (Central Processing Unit) and a semiconductor memory. The amplifier <NUM> may drive a motor to operate the machining unit. The control panel unit <NUM> controls the operation of the machining unit <NUM> including chucking of the workpiece, rotation of the main spindle, movement of the headstock and the tool post, and supply of lubricant. The semiconductor memory may comprise a ROM (Read Only Memory) and a RAM (Random Access Memory). The control device <NUM> is arranged in the internal space <NUM> of the casing <NUM> made of metal. The control device <NUM> produces heat when activated by externally supplied electricity. Especially, the amplifier <NUM> produces a large amount of heat when drives the motor to operate the machining unit. The amplifier <NUM> sucks in the air from below. The air of higher temperature is discharged above the amplifier <NUM>. There may be provided a gap between the upper end <NUM> of the amplifier <NUM> and the ceiling <NUM> of the inner wall <NUM>. To prevent overheat of the control device <NUM>, the control panel unit <NUM> may be provided with the duct <NUM> having the fan <NUM>. The duct having the fan may be referred to as the duct with fan <NUM>.

The casing <NUM> may comprise a rectangular bottom plate <NUM> under the control device <NUM>, a rectangular top plate <NUM> above the control device <NUM>, the rectangular door <NUM> openable in front of the control device <NUM>, a rectangular back plate <NUM> behind the control device <NUM>, a rectangular left-side plate <NUM> on the left side of the control device <NUM>, and a rectangular right-side plate <NUM> on the right side of the control device <NUM>. The back plate <NUM>, the left-side plate <NUM>, and the right-side plate <NUM> are mounted on the bottom plate <NUM> to hold the top plate <NUM>. The door <NUM> is joined to the left-side plate <NUM> by using a hinge. The door <NUM> is opened frontward and closed rearward on the hinge. The internal space <NUM> is opened to the air when the door <NUM> is opened. The internal space <NUM> is closed when the door <NUM> is closed. The casing <NUM> is of a box-shape made of the bottom plate <NUM>, the top plate <NUM>, the back plate <NUM>, the left-side plate <NUM>, and the right-side plate <NUM>.

Machining the workpiece produces oil mist due to the supplied lubricant. The control panel unit needs a dust/oil filter to take the outside air (cool air) into the internal space <NUM>. The filter is necessarily often exchanged to keep desired cooling efficiency. A heat exchanger or a heat sink as a cooling alternative would make the control panel unit larger in size and higher in cost. The control panel unit <NUM> of the embodiment can provide the closed internal space <NUM> only by closing the door <NUM>. The internal space <NUM> is closed to the extent that dust or oil mist is blocked. The internal space <NUM> is opened to the air when the door <NUM> is opened.

The casing structure is not limited to the <FIG> structure. The door <NUM> may be replaced by a front plate having an openable door.

The duct with fan <NUM> is fixed to the inner wall <NUM> of the casing <NUM> to cool the closed internal space <NUM>. The inner wall <NUM> corresponding to the inner wall of the bottom plate <NUM> may be referred to as the bottom <NUM>. The inner wall <NUM> corresponding to the inner wall of the top plate <NUM> may be referred to as the ceiling <NUM>. The inner wall <NUM> corresponding to the inner wall of the door <NUM>, the left-side plate <NUM>, and the right-side plate <NUM> may be referred to as the upright wall <NUM>. The upright wall <NUM> connects the bottom <NUM> with the ceiling <NUM>. The duct <NUM> may comprise the exhaust duct <NUM> fixed on the upright wall <NUM> of the left-side plate <NUM>. The duct <NUM> may comprise the intake duct <NUM> fixed on the upright wall <NUM> of the right-side plate <NUM>. The exhaust duct <NUM> may be provided with the exhaust fan <NUM>. The intake duct <NUM> may be provided with the intake fan <NUM>. The duct <NUM> and <NUM> on the upright wall <NUM> each is nearer the ceiling <NUM> than the bottom <NUM>.

<FIG> shows an appearance of the duct with fan <NUM>. The exhaust duct <NUM> and the intake duct <NUM> are the same in shape. The exhaust fan <NUM> and the intake fan <NUM> are the same in shape. The both ducts <NUM> and <NUM> are collectively shown as the duct <NUM>. The both fans <NUM> and <NUM> are collectively shown as the fan <NUM>. <FIG> is a horizontal section view of the control panel box <NUM> taken along a line passing through the exhaust fan <NUM>. The duct <NUM> has the groove <NUM> through which the air passes and the ventilation opening <NUM> on which the fan <NUM> is mounted.

The groove <NUM> is formed by a wider side <NUM> of the duct <NUM> opposite the inner wall <NUM> and shorter sides <NUM> and <NUM> thereof opposite to each other. One end of the groove <NUM> is closed by a closed side <NUM> of the duct <NUM> connected to the wider side <NUM> and the shorter sides <NUM> and <NUM>. The duct <NUM> has a plurality of fitting parts <NUM>. The other end of the groove <NUM> is open to the internal space <NUM>. The closed end of the groove <NUM> may be referred to as the closed end <NUM>. The open end of the groove <NUM> may be referred to as the open end <NUM>. The groove <NUM> is open to the internal space <NUM> to the extent that the open end <NUM> is apart from the opposite inner wall <NUM>. Particularly, the open end <NUM> is apart from the bottom <NUM> as shown in <FIG>. Part of the internal space <NUM> therefore exists between the open end <NUM> and the inner wall <NUM>. The fitting parts <NUM> may comprise a pair of parts near the closed end <NUM> and another pair of parts near the open end <NUM> as shown in <FIG>. One of the fitting parts <NUM> near the closed end <NUM> is protruded from the side <NUM> toward the door <NUM> while the other is protruded from the side <NUM> toward the rear plate <NUM>. The fitting parts <NUM> near the open end <NUM> are bent from the sides <NUM> and <NUM> toward the groove <NUM> and protruded toward the bottom plate <NUM>.

The ventilation opening <NUM> of the duct <NUM> is formed on the wider side <NUM> opposite the inner wall <NUM>. The ventilation opening <NUM> is nearer the closed end <NUM> than the open end <NUM> of the groove <NUM>. The ventilation opening <NUM> connects the groove <NUM> with the internal space <NUM>.

The duct <NUM> is fixed to the inner wall <NUM> of the casing <NUM> in such manner as the groove <NUM> faces the inner wall <NUM>. The groove <NUM> enclosed by the inner wall <NUM> and the duct <NUM> may be an air passage of the air in the internal space <NUM>. The duct <NUM> may be detachably fixed to the inner wall <NUM> by using a screw SC1 or a bolt. A bolt may be fitted into a through-hole formed on the fitting part <NUM> and a through-hole formed on the casing <NUM> and then fastened by a nut. A screw SC1 fitted into the through-hole of the casing <NUM> may be screwed in a screw hole formed on the fitting part <NUM>. The fitting direction is not limited to <FIG>. The screw SC1 may be fitted in a opposite direction. In <FIG>, the duct <NUM> is attached to an upper part of the upright wall <NUM> in such manner as the closed side <NUM> is apart from the ceiling <NUM>.

The duct <NUM> may be made of metal or other materials such as resin. A metal duct would be joined to the inner wall <NUM> by welding the fitting parts <NUM>. Any other methods such as a high heat resistant double-sided tape would be useful to join them.

The fan <NUM> is mounted on the duct <NUM> to cover the ventilation opening <NUM>. The fan <NUM> is driven by electricity. The air (Ar) in the internal space <NUM> is taken into the groove <NUM> enclosed by the inner wall <NUM> and the duct <NUM> by the operation of the fan <NUM>. The air flow in the AX1 direction along the groove <NUM> may be perpendicular to an AX2 air flow direction of the fan <NUM>. The air flow would be smooth even when the duct is attached in a corner of the casing <NUM>. The AX2 air flow direction of the fan <NUM> may necessarily cross the AX1 direction, but not necessarily be perpendicular.

The fan <NUM> may be the exhaust fan <NUM>. The duct <NUM> may be the exhaust duct <NUM>. The air in the internal space <NUM> may be taken into the groove <NUM> through the open end <NUM>. The air passing down the groove <NUM> in the AX1 direction is exhausted to the internal space <NUM> through the ventilation opening <NUM>. The exhausted air then flows in the AX2 air flow direction of the fan <NUM>.

The fan <NUM> may be the intake fan <NUM>. The duct <NUM> may be the intake duct <NUM>. The air in the internal space <NUM> may be sucked in the ventilation opening <NUM> in the AX2 air flow direction. The air passing down the groove <NUM> in the AX1 direction is discharged to the internal space <NUM> through the open end <NUM>. The air discharged from the exhaust fan <NUM> is delivered to the intake fan <NUM> when the exhaust fan <NUM> is opposite the intake fan <NUM> as shown in <FIG>.

The outer wall of the casing <NUM> is exposed to the outside air of lower temperature. Heat energy of the air passing down the groove <NUM> is radiated to the outside air through the casing <NUM>. The air flow in the groove <NUM> is accelerated near the inner wall <NUM>. The heat transmission coefficiency is improved, thereby achieving efficient heat radiation to the outside air.

The upper end 200a of the fan <NUM> is positioned above the upper end 32a of the amplifier <NUM> as shown in <FIG>. (The upper end 200a of the fan <NUM> is nearer the ceiling <NUM> than the upper end 32a is. ) Such arrangement prevents a stay of the air of higher temperature discharged from the amplifier <NUM>. The air of higher temperature discharged from the amplifier <NUM> is sucked in the groove <NUM> of the duct <NUM> by the operation of the intake fan <NUM>. Heat energy of the air passing down the groove <NUM> is radiated to the outside air through the casing <NUM>. The fan <NUM> above the amplifier <NUM> may be desirably the intake fan <NUM>. The fan <NUM>, however, may be the exhaust fan which sends the air of lower temperature out of the groove <NUM> toward above the amplifier <NUM>, preventing a stay of the air of higher temperature above the amplifier <NUM>.

The amplifier <NUM> may be fixed on the back plate <NUM>. The fan <NUM> of the duct <NUM> attached to the side-plates <NUM> and <NUM> may be desirably nearer the back plate <NUM> than the door <NUM>. Such arrangement further prevents a stay of the air of higher temperature discharged from the amplifier <NUM>.

The depth L1 of the groove <NUM> may be desirably smaller than the width L2 of the groove <NUM> to bring the air nearer the inner wall <NUM>, thereby achieving efficient heat radiation. In <FIG>, the depth L1 corresponds to the length of the groove <NUM> in the direction perpendicular to the wider side <NUM>. The width L2 corresponds to the distance between the sides <NUM> and <NUM>. The dimensions of the duct <NUM> may be variable according to heat emission conditions of the control panel unit. The dimensions may be defined as, for example, "L1<L2/<NUM>" or "L1<L2/<NUM>". The depth L1 may be desirably smaller than the diameter D of the fan <NUM>. The width L2 may be desirably greater than the diameter D of the fan <NUM>. To keep the air flow near the inner wall <NUM> in the groove <NUM>, the length L3 may be desirably greater than the width L2. In <FIG>, the length L3 corresponds to the length of the wider side <NUM> in the AX1 direction. The dimensions may be defined as, for example, "L3><NUM> × L2" or "L3><NUM> × L2". The length L3 may be shorter than the length of the upright wall <NUM> in the groove direction.

The operation and the effect of the embodiments are being described referring to <FIG>. <FIG> schematically shows the heat radiation passage of the control panel unit.

The air (Ar) in the internal space <NUM> of the casing <NUM> is taken into the groove <NUM> of the exhaust duct <NUM> through the open end <NUM> by the operation of the exhaust fan <NUM>. The air passes down the groove <NUM> in the AX1 direction toward the ventilation opening <NUM>. The outer wall of the casing <NUM> is exposed to the outside air of lower temperature. Heat energy of the air passing down the groove <NUM> is therefore radiated to the outside air through the casing <NUM> in the H1 direction as shown in <FIG>. The upper air in the internal space <NUM> is higher in temperature than the lower air in the internal space <NUM>. Since the exhaust duct <NUM> is attached on the upper part of the upright wall <NUM>, heat energy of the air of higher temperature passing down the groove <NUM> is efficiently radiated to the outside air. The accelerated air flow in the groove <NUM> provides efficient heat radiation to the outside air.

The air flow in the AX1 direction of the groove <NUM> is changed to the air flow in the AX2 direction of the exhaust fan <NUM> after through the ventilation opening <NUM>. The air in the internal space <NUM> is delivered to the intake fan <NUM> along the ceiling <NUM>. Heat energy of the air is radiated to the outside air in the H1 direction through the top plate <NUM> as shown in <FIG>. The upper air in the internal space <NUM> is higher in temperature. Heat energy of the air is efficiently radiated to the outside air. The air is taken into the groove <NUM> of the intake duct <NUM> by the operation of the intake fan <NUM>. The air flow in the AX2 direction is changed to the air flow in the AX1 direction after through the ventilation opening <NUM>. The air passes down the groove <NUM> toward the the open end <NUM>. Heat energy of the air is radiated to the outside air in the H1 direction through the right-side plate <NUM> as shown in <FIG>. The intake duct <NUM> is attached to an upper part of the upright wall <NUM>. The heat having higher temperature passes down the groove <NUM> of the intake duct <NUM>. Heat energy of the air is efficiently radiated to the outside air. The accelerated air flow in the groove <NUM> provides efficient heat radiation to the outside air.

The air discharged through the open end <NUM> goes downward along the inner wall <NUM> of the right-side plate <NUM>. Heat energy of the air is radiated to the outside air through the right-side plate <NUM>. The air flow direction is then changed toward the exhaust duct <NUM>. The air is taken into the groove <NUM> of the exhaust duct <NUM> through the open end <NUM> by the operation of the exhaust fan <NUM>.

As described above, the wider air circulation flow C1 is generated in the casing <NUM>. Heat energy of the air in the internal space <NUM> is efficiently radiated to the outside air through the casing <NUM>. The internal space <NUM> is closed to prevent invasion of dust and mist. The duct <NUM> can be made shorter than the upright wall <NUM> in the AX1 direction of the groove <NUM>. The invention eliminates the need of an expensive heat exchanger or an expensive heat sink. The invention efficiently radiates heat energy from the control panel unit <NUM> without providing a cooling space entirely over the control panel unit. The invention can downsize the control panel unit. The duct <NUM> may be detachably attached to the inner wall <NUM>. The duct <NUM> may be attached in different positions according to the control panel unit <NUM>, providing efficient heat radiation suitable for the control panel unit. The invention can further downsize the control panel unit.

The invention may be embodied in various ways. The number of the duct with fan <NUM> is not limited to two. Three or more ducts may be applied. The duct <NUM> may be fixed to the upright wall <NUM> in such manner as the closed end <NUM> is apart from the ceiling. The duct <NUM> may be also fixed in such manner as the closed end <NUM> is in contact with the ceiling <NUM>. The duct <NUM> may be fixed to the upright wall <NUM> of the side-plates <NUM> and <NUM>. The duct may be fixed to any of the upright wall <NUM>, the ceiling <NUM>, and the bottom plate <NUM> of the back plate <NUM>.

A plurality of the intake ducts <NUM> may be used to generate an air circulation flow C2 in the casing <NUM>. <FIG> schematically shows another example of a control panel unit <NUM> whose door is open. The control panel unit <NUM> is denoted by a dot line for ease of understanding. The embodiment in <FIG> is different from the embodiment in <FIG> in that the duct with fan <NUM> on the upright wall <NUM> of the left-side plate <NUM> is replaced by the intake duct <NUM> provided with the intake fan <NUM>.

The air in the internal space <NUM> is taken into the groove <NUM> of the intake duct <NUM> attached to the left-side plate <NUM>. The air entering the groove <NUM> through the ventilation opening <NUM> goes toward the open end <NUM>. Heat energy of the air passing down the groove <NUM> is radiated to the outside air through the left-side plate <NUM>. The air passing through the open end <NUM> goes downward along the upright wall <NUM> of the left-side plate <NUM> and then turns upward. The air in the internal space <NUM> is taken into the groove <NUM> of the intake duct <NUM> attached to the right-side plate <NUM>. The air entering the groove <NUM> through the ventilation opening <NUM> goes toward the open end <NUM>. Heat energy of the air passing down the groove <NUM> is radiated to the outside air through the right-side plate <NUM>. The air passing through the open end <NUM> goes downward along the upright wall <NUM> of the right-side plate <NUM> and then turns upward.

The air circulation flow C2 is thereby generated in the casing <NUM>. Heat energy of the air in the internal space <NUM> is widely radiated to the outside air through the casing <NUM>. Efficient heat radiation from the control panel unit <NUM> is available without providing a cooling space entirely over the control panel unit. The embodiment can also downsize the control panel unit.

One of the intake ducts <NUM> may be attached to the ceiling <NUM> and the other may be attached to the upright wall <NUM> of the back plate <NUM> to generate an air circulation flow C3 in the casing <NUM>. <FIG> schematically shows another example of a control panel unit <NUM> whose door is open. The control panel unit <NUM> is denoted by a dot line for ease of understanding. The closed end <NUM> and the intake fan <NUM> of the intake duct <NUM> on the ceiling <NUM> is near the left-side plate <NUM> while the open end <NUM> thereof faces the upright wall <NUM> of the right-side plate <NUM>. The closed end <NUM> and the intake fan <NUM> of the intake duct <NUM> on the upright wall <NUM> of the back plate <NUM> is near the ceiling <NUM> while the open end <NUM> thereof faces the bottom plate <NUM>.

The air in the internal space <NUM> is taken into the groove <NUM> of the intake duct <NUM> attached to the ceiling <NUM>. The air entering the groove <NUM> through the ventilation opening <NUM> goes toward the open end <NUM>. Heat energy of the air passing down the groove <NUM> is radiated to the outside air through the top plate <NUM>. The upper air in the internal space <NUM> is higher in temperature. Since the intake duct <NUM> is attached to the ceiling <NUM>, the air passing down the groove <NUM> is higher in temperature, providing efficient heat radiation to the outside air. The air passing through the open end <NUM> goes downward along the ceiling <NUM> and then turns rightward. Heat energy of the air is radiated to the outside air through the top plate <NUM>.

The air in the internal space <NUM> is taken into the groove <NUM> of the intake duct <NUM> attached to the upright wall <NUM> of the back plate <NUM>. The air entering the groove <NUM> through the ventilation opening <NUM> goes toward the open end <NUM>. Heat energy of the air passing down the groove <NUM> is radiated to the outside air through the back plate <NUM>. The upper air in the internal space <NUM> is higher in temperature. Since the intake duct <NUM> is attached to the upper part of the upright wall <NUM>, the air passing down the groove <NUM> is higher in temperature, providing efficient heat radiation to the outside air. The air passing through the open end <NUM> goes downward along the upright wall <NUM> of the back plate <NUM> near the right-side plate <NUM>. Heat energy of the air is radiated to the outside air through the back plate <NUM>. The air then turns toward the intake fan <NUM> and enters the groove <NUM> of the intake duct <NUM> on the ceiling <NUM> through the ventilation opening <NUM>.

The air circulation flow C3 is thereby generated in the casing <NUM>. Heat energy of the air in the internal space <NUM> is widely radiated to the outside air through the casing <NUM>. Efficient heat radiation from the control panel unit <NUM> is available without providing a cooling space entirely over the control panel unit. The embodiment can also downsize the control panel unit.

Claim 1:
A control panel unit (<NUM>) for a machine tool (<NUM>) comprising
an openable door (<NUM>);
a casing (<NUM>) which closes an internal space (<NUM>) in which a control device (<NUM>) is arranged;
a duct (<NUM>) having a groove (<NUM>) and a ventilation opening (<NUM>), the groove (<NUM>) being closed at a closed end (<NUM>) and open to the internal space (<NUM>) at an open end (<NUM>), the ventilation opening (<NUM>) being provided nearer the closed end (<NUM>) of the groove (<NUM>) to connect the groove (<NUM>) with the internal space (<NUM>), and the duct (<NUM>) being fixed to an inner wall (<NUM>) of the casing (<NUM>) in such manner as the groove (<NUM>) faces the inner wall (<NUM>) of the casing (<NUM>); and
a fan (<NUM>) mounted on the ventilation opening (<NUM>),
wherein the fan (<NUM>) comprises an exhaust fan (<NUM>) which discharges the air from the groove (<NUM>) to the internal space (<NUM>) through the ventilation opening (<NUM>), and the duct (<NUM>) comprises an exhaust duct (<NUM>) provided with the exhaust fan (<NUM>), wherein air in the internal space (<NUM>) is taken into the groove (<NUM>) enclosed by the inner wall (<NUM>) and the exhaust duct (<NUM>) through the open end (<NUM>) by the operation of the exhaust fan (<NUM>),
characterized in that the control panel unit further comprises an intake fan (<NUM>) and an intake duct (<NUM>) having a groove (<NUM>) and a ventilation opening (<NUM>), wherein said intake duct (<NUM>) is provided with the intake fan (<NUM>) and fixed to the inner wall (<NUM>) in such manner as the intake fan (<NUM>) faces the exhaust fan (<NUM>), and the air is taken into the groove (<NUM>) of the intake duct (<NUM>) through its ventilation opening (<NUM>) by the operation of the intake fan (<NUM>) and discharged to the internal space (<NUM>) through the open end (<NUM>).