Nozzle structure

A nozzle structure is mounted in a compression molding machine that compresses using a punch a powder material filled in a die to manufacture a compressively molded product, and sprays a lubricant at least toward a tip of the punch prior to filling the powder material and includes a guide path that guides the lubricant, and a spraying portion that is provided at an end of the guide path so as to communicate therewith and that sprays the lubricant guided along the guide path so as to be substantially aligned with a predetermined straight line intersecting at least in a direction of relative displacement of the punch.

TECHNICAL FIELD

The present invention relates to a nozzle structure for use in a compression molding machine that compresses a powder material to mold a product such as a medical tablet and a food item.

BACKGROUND ART

As described in a Patent Document (International Publication No. WO 2005/110726 Pamphlet), a conventionally known rotary powder compression molding machine used for production of tablets includes a spray nozzle that sprays a powder lubricant so as to allow the powder lubricant to adhere to a punch and/or an inside of a die. In the rotary powder compression molding machine described in the Patent Document, the powder lubricant sprayed from the spray nozzle is charged electrostatically and differently so as to adhere to each of an upper punch, a lower punch and the die.

The spray nozzle for the powder lubricant has a concave portion formed of three-dimensional curved surface and an electrode projecting into the concave portion. The powder lubricant is supplied into the concave portion using a pressurized gas and is electrostatically charged in the concave portion by a direct voltage that is applied to the electrode then to be guided toward the upper punch or the like along the three-dimensional curved surface of the concave portion.

However, in such a configuration, the powder lubricant possibly adheres to regions other than a target region, resulting in deterioration in efficiency of the powder lubricant. Specifically, the powder lubricant is sprayed along the three-dimensional curved surface in the nozzle provided with the concave portion described above, so that the powder lubricant scatters into a relatively large area. Therefore, increased is a quantity of the powder lubricant which is sprayed but does not adhere to the target region, that is, which does not contribute to product molding, resulting in deterioration in efficiency of the powder lubricant.

DISCLOSURE OF THE INVENTION

It is therefore an object of the present invention to solve the above defect.

Specifically, a nozzle structure according to the present invention sprays a lubricant at least toward a tip of a punch prior to filling a powder material in a compression molding machine that compresses using the punch the powder material filled in a die to manufacture a compressively molded product, and the nozzle structure includes: a guide path that guides the lubricant; and a spraying portion that is provided at an end of the guide path so as to communicate therewith, and that sprays the lubricant guided along the guide path so as to be substantially aligned with a predetermined straight line intersecting at least in a direction of relative displacement of the punch.

In the above configuration, the spraying portion sprays the lubricant toward the punch, which is being relatively displaced, so as to be substantially aligned with the straight line. Thus decreased, in comparison with a case of radially spraying the lubricant, is a quantity of the lubricant that does not adhere at least to the punch. Accordingly, it is possible to improve efficiency of the lubricant.

The lubricant in the present invention inhibit, upon compressively molding a tablet in a powder compression molding machine, a powder medical material from adhering to an inside of the die as well as to tips of upper and lower punches. Specific examples of the lubricant, particularly the powder lubricant, include stearic acids, stearates (metal salts of Al, K, Na, Ca, Mg and the like) and water-shedding substances such as sodium lauryl sulfate.

In order to broaden utility regardless of the shape of the compressively molded product, the spraying portion is preferably formed of a groove that has a width smaller than a width of the tip of the punch and a length greater than a length of the tip of the punch, and a through hole that is opened substantially at a center of a bottom surface of the groove and allows the groove and the guide path to communicate with each other.

For easier production, preferably, the guide path is provided in a path main body, and the spraying portion is provided to a plate body that is detachably attached to the path main body.

In order to have the lubricant effectively adhere to a target region, preferably there is further included electric field generation means that charges the lubricant sprayed near the spraying portion. In order to efficiently charge the lubricant using the electric field generation means, the electric field generation means may include an electrode that has an end exposed into the guide path near the spraying portion.

The compression molding machine applying the present invention preferably includes: a frame; an upright shaft that is provided rotatably in the frame; a turret that is mounted to the upright shaft; a plurality of dies each that are provided with a die hole and are attached to the turret at a predetermined interval in a circumferential direction thereof, upper punches and lower punches that are disposed so as to allow tips thereof to be inserted into the die holes of the dies from upwards and downwards, respectively; and an upper roll and a lower roll that compress the powder material filled in the die holes when the upper punches and the lower punches pass therebetween with the tips thereof being inserted into the die holes, respectively.

In order to improve adhesion accuracy of the lubricant to the upper punches and the lower punches in the above rotary powder compression molding machine, preferably, the path main body includes a first guide path and a second guide path that are formed substantially in parallel with each other in the path main body, a first plate body provided with a first spraying portion that sprays the lubricant toward the upper punches, is detachably attached to the path main body so as to correspond to the first guide path, a second plate body provided with a second spraying portion that sprays the lubricant at least toward the lower punches, is detachably attached to the path main body so as to correspond to the second guide path, and the electric field generation means includes a first electrode having an end exposed into the guide path near the first spraying portion, and a second electrode having an end exposed into the guide path near the second spraying portion.

In the above described configuration according to the present invention, in comparison with the case of radially spraying the lubricant, decreased is the quantity of the lubricant that does not adhere at least to the punches. Therefore, it is possible to improve efficiency of the lubricant.

BEST MODE FOR CARRYING OUT THE INVENTION

Described below with reference to the drawings is an embodiment of the present invention.

The embodiment described below is applied to a rotary powder compression molding machine.

As shown inFIG. 1, the rotary powder compression molding machine includes a frame1, an upright shaft2that is provided rotatably in the frame1, a turret3that is mounted to the upright shaft2, a plurality of dies4each that have a die hole41and are attached to the turret3at a predetermined interval in a circumferential direction thereof, upper punches5and lower punches6that are disposed to allow tips thereof to be inserted into the die holes of the dies4from upwards and downwards, respectively, and upper rolls91and93as well as lower rolls92and94that compress a powder material filled in each of the die holes41when the upper punches5and the lower punches6pass therebetween with the tips thereof being inserted into the die holes41, respectively. The rotary powder compression molding machine further includes a nozzle structure7that has a nozzle portion and is disposed on an upper side of the turret3.

The upright shaft2is rotatably supported by a bearing21, which is supported by the frame1. There is fixed a worm wheel22in the vicinity of a lower end of the upright shaft2. The upright shaft2is rotated when a drive force of a motor25is transmitted to the worm wheel22by way of a worm23and a belt24.

The turret3is mounted to the upright shaft2and has a circular plate shape in planar view. The turret3includes an upper punch retaining portion32in an upper portion thereof, and a die portion33beneath the upper punch retaining portion32. The upper punch retaining portion32retains the plurality of upper punches5so as to be vertically slidable, and is provided with punch retaining holes of the number corresponding to the number of the upper punches5at a predetermined interval in the circumferential direction. The punch retaining holes retains the upper punches5respectively. The die portion33retains the lower punches6so as to be vertically slidable using punch retaining holes of the number corresponding to the number of the lower punches6provided at the predetermined interval in the circumferential direction. The die portion33has a plurality of die mounting holes provided at a predetermined interval in the circumferential direction so as to correspond to the positions of the upper punches5and the lower punches6thus retained. The dies4are detachably mounted in the die mounting holes, respectively.

In the rotary powder compression molding machine configured as described above, a surface of the turret3can be sectioned in accordance with functions. As shown inFIG. 2, the surface of the turret3is provided with a powder filling section PFS, a powder leveling section PWS, a compression molding section PMS, a product ejecting section PES, and a lubricant spraying section LJS, sequentially along the direction of rotation of the turret3. These sections each are described below.

In the powder filling section PFS, the powder material for products Q is filled substantially evenly into the respective dies4sequentially with the lower punches6being descended to the lowest position. During this process, the upper punches5are retained at a high position so as not to disturb the operation of filling the powder material.

In the powder leveling section PWS, the lower punches6are ascended to a predetermined position set for each type of the products Q so that the quantity of the powder material filled in each of the dies4is made equal to a quantity required for manufacturing the product Q. As a result, the powder material that overflows out of the dies4is removed from the turret3so that the quantities of the powder material filled in the respective dies4are made substantially the same. The upper punches5are retained at a high position also in the powder leveling section PWS as in the powder filling section PFS.

In the compression molding section PMS, after the upper punches5having been descended to the position of starting compression, the upper punches5and the lower punches6are made to pass between the upper and lower pre-compression rolls91and92so as to preliminarily compress the powder material filled in the dies4. Then, the upper punches5and the lower punches6retained at the position of passing between the upper and lower pre-compression rolls91and92are made to pass between the upper and lower main compression rolls93and94so as to further compress the powder material that has already been preliminarily compressed.

In the product ejecting section PES, the upper punches5are ascended to pull the tips thereof out of the dies4, respectively, and the lower punches6are then ascended to push the products Q out of the dies4. The pushed out products Q are conveyed at an ejecting position by the turret3and collected.

In the lubricant spraying section LJS, the upper punches5are descended until the tips thereof are positioned below an air outlet78dof a nozzle assembly79, while the lower punches6are descended to the position of starting filling the powder material. In other words, the upper punches5are descended to a position of minimizing the distance between the tips thereof and a first spraying portion72a, while the lower punches6are lowered to a position where a powder lubricant adheres to portions expected to be in contact with the powder material, namely, entire inner walls of the dies4as well as the tips of the lower punches6.

In the respective sections described above, the upper punches5and the lower punches6are ascended or descended using any type of a rail and a cam employed in a conventional rotary powder compression molding machine. Therefore, the rail and the cam are neither described in detail nor shown in the drawings herein.

As shown inFIGS. 3 to 6, the nozzle structure7includes guide paths71that guide the powder lubricant, spraying portions72that are provided at ends of the guide paths71respectively so as to communicate therewith, and spray the powder lubricant guided along the guide paths71so as to be substantially aligned with a predetermined straight line intersecting at least with the direction of relative displacement of the upper punches5and the lower punches6, and electric field generation means8that charges the powder lubricant sprayed in the vicinity of the spraying portions72. In the nozzle structure7according to the present embodiment, the nozzle assembly79is configured by a first plate body74that is provided with the first spraying portion72a, a second plate body75that is provided with a second spraying portion72b, a path main body76that is provided with the guide paths71, connecting pipes77that communicate with the guide paths71, and a housing78that supports the path main body76. The nozzle assembly79is mounted with a first electrode81and a second electrode82that configure the electric field generation means8. It is possible to employ a direct high voltage supply device such as that disclosed in the above Patent Document, wherein the direct high voltage supply device configures the electric field generation means8and supplies each of the first electrode81and the second electrode82with a direct high voltage.

The path main body76is a thick and substantially flat plate made of fluorocarbon resin or the like. Formed in a solid core of the path main body76are a first guide path71aand a second guide path71bsubstantially in parallel with each other so as not to change relative positions therebetween. Although the path main body76may not be necessarily solid in the core thereof, the first guide path71aand the second guide path71bneed to be formed therein immovably as well as independently from each other. The path main body76further includes electrode mounting holes that are each provided substantially in parallel with corresponding one of the guide paths71and that allow the first electrode81and the second electrode82to be inserted thereinto independently from each other.

The first guide path71aguides the powder lubricant to the first plate body74such that the powder lubricant is sprayed toward the upper punches5. The first guide path71ais thus formed substantially in parallel with an upper surface of the path main body76and is then redirected upwards to be substantially vertical at the end thereof. On the other hand, the second guide path71bguides the powder lubricant to the second plate body75such that the powder lubricant is sprayed toward the lower punches6as well as toward the inside of the dies4, namely, the inner wall surfaces of the die holes41. The second guide path71bis thus formed substantially in parallel with a lower surface of the path main body76and is then redirected downwards to be substantially vertical at the end thereof. The path main body76has a first concave portion76cand a second concave portion76dprovided on the upper and lower surfaces at regions corresponding to the ends of the first guide path71aand the second guide path71b, respectively, so as to comply with the configurations of the guide paths71aand71b. Attached into the first concave portion76cand the second concave portion76dare the first plate body74and the second plate body75that configure the spraying portions72.

There are provided connecting pipes77aand77bthat connect supply conduits of a powder lubricant supply device to the guide paths71aand71b, respectively. The connecting pipes77aand77bare each made of fluorocarbon resin or the like similarly to the path main body76, and each have a bar shape in which connecting paths77cand77dare formed to have inner diameters substantially equal to those of the first and second guide paths71aand71b, respectively. The first and second guide paths71aand71bare connected with the connecting paths77cand77d, respectively, by inserting the connecting pipes77aand77binto mounting holes that are provided in the path main body76so as to have central axes identical to those of the guide paths71aand71b. Male screws are formed at outer ends of the connecting pipes77aand77b, respectively, that are used for connecting the supply conduits therewith. Further provided in the connecting pipes77aand77bso as to be substantially in parallel with the connecting paths77cand77dare through holes that allow the first and second electrodes81and82, which configure the electric field generation means8, to pass therethrough respectively.

It may be able to adopt a powder lubricant supply device widely known in this art. Specifically, a device according to the above Patent Document can be exemplified, which continuously feeds a small quantity of a powder lubricant such as 5 to 25 g per hour to the guide paths71aand71b, respectively. In order to feed the powder lubricant at a predetermined rate, a feed rate thereof is optically detected according to the low-angle light diffusion system or is electrically detected according to the electrostatic capacitance system or the like, so as to calculate a difference between the quantity of supplied powder lubricant based on the detected feed rate and the quantity of the powder lubricant that does not adhere but is retrieved. The quantity of the supplied powder lubricant is then feedback controlled according to the calculation result so as to feed the powder lubricant at the predetermined rate.

The first plate body74and the second plate body75are detachably attached, using screws, into the first concave portion76cand the second concave portion76din the path main body76. The first plate body74is provided with the first spraying portion72awhile the second plate body75is provided with the second spraying portion72b. The first spraying portion72ahas a shape identical to that of the second spraying portion72b, and the first spraying portion72aand the second spraying portion72bare each provided on a surface substantially aligned with the surface (the upper surface or the lower surface) of the path main body76when mounted. The first spraying portion72aand the second spraying portion72bare configured by grooves74aand75aand through holes74band75b, respectively.

The grooves74aand75ahave widths smaller than those of tips51and61of the upper punches5and lower punches6, and have lengths greater than those of the tips51and61of the upper punches5and lower punches6. The grooves74aand75amay each have a deepest portion at the center thereof and each form an opening in the surface of the plate body74or75. The grooves74aand75aeach have a depth made gradually smaller from the center thereof. The grooves74aand75aare formed in the plate bodies74and75, respectively, such that the nozzle structure7mounted to the frame1has a longitudinal direction substantially perpendicular to a trajectory100of the centers of the dies4.

The through holes74band75bcommunicate with the insides of the grooves74aand75a, respectively. The through holes74band75bpenetrate into the grooves74aand75afrom the surfaces opposite to the surfaces provided with the grooves74aand75a, respectively, that is, from the surfaces in contact with bottom surfaces of the first and second concave portions76cand76d. The through holes74band75bhave inner diameters substantially equal to those of the first and second guide paths71aand71b, and are formed to communicate with the first and second guide paths71aand71bin a case where the first and second plate bodies74and75are attached into the concave portions76cand76d. There are formed electrode holes, which allow the first and second electrodes81and82to pass therethrough, so as to be perpendicular to the central axes of the through holes74band75b. When the nozzle assembly79is build up, exposed to the through holes74band75bare the ends of the first and second electrodes81and82that pass through the electrode holes.

The housing78is used for attaching the path main body76to the frame1, and hollows in the substantial center thereof such that the path main body76is partially exposed from a hollow portion78a. Specifically, the housing78is a plate body made of fluorocarbon resin and is thicker than the path main body76. The hollow portion78ais opened on the upper surface of the housing78into a substantially parallelogram shape in planar view. The housing78is provided on the lower surface thereof with a spray opening78band a retrieval opening78c. The spray opening78bis provided at a region corresponding to the second spraying portion72bof the second plate body75, and the retrieval opening78chas a half oval shape and is provided at a region in the vicinity of as well as apart from the spray opening78b. There is no limitation in the shape to the opening of the hollow portion78aon the upper surface of the housing78as long as the first spraying portion72ais entirely exposed when the path main body76is inserted from an opening formed on a side surface of the housing78into the hollow portion78ain the housing78. Further, the shape of the retrieval opening78cis not limited as long as the retrieval opening78cis used for retrieving the powder lubricant sprayed out of the spray opening78bonto the turret3and is positioned behind the turret3in the direction of rotation thereof.

An air outlet78dand an air inlet78eare positioned such that the upper opening of the hollow portion78ain the housing78is interposed between the air outlet78dand the air inlet78e. The air outlet78dis used for forming an air curtain that prevents the powder lubricant being sprayed from the first spraying portion72abut not adhering to the upper punches5from scattering above the lower ends of the upper punches5. In a state where the path main body76is incorporated in the housing78, the air outlet78dextends in both directions from the first spraying portion72asubstantially as a center thereof and is opened substantially in parallel with the upper surface of the housing78in planar view. At the position where the powder lubricant is made to adhere to the upper punches5, the air outlet78dis provided such that the air curtain is formed above the lower ends of the upper punches5. The air inlet78eis provided so as to face the air outlet78d, and sucks the excess powder lubricant floating between the air curtain and the upper surface of the housing78. The air inlet78eis an opening wider than the air outlet78dand is provided substantially as high as or slightly higher than the air outlet78d.

The powder lubricant sucked from the retrieval opening78cand the air inlet78eis retrieved into a dust pickup device (not shown) by way of a dust pickup conduit73. As described above, the housing78is provided with a retrieval path73bthat allows the powder lubricant retrieved through the retrieval opening78cand the air inlet78eto pass therethrough.

As shown inFIG. 7, the electric field generation means8includes the first electrode81and the second electrode82described above, as well as a power supply83, a first high voltage generator84, a second high voltage generator85, and a voltage controller86. The power supply83generates a direct voltage. Each of the first high voltage generator84and the second high voltage generator85is electrically connected to the power supply83and converts the direct voltage outputted from the power supply83into a high voltage. The voltage controller86controls voltage values outputted from the first high voltage generator84and the second high voltage generator85independently from each other. Applied to the first electrode81and the second electrode82are negative direct high voltages, namely, a first direct high voltage and a second direct high voltage, each that are outputted from the first high voltage generator84and the second high voltage generator85and are controlled by the voltage controller86. On the other hand, a positive direct high voltage is applied to the frame1that is maintained at a reference potential. As the frame1is maintained at the reference potential, that is, is grounded, also grounded are the upper and lower punches5and6as well as the dies4to which the powder lubricant adheres.

The first direct high voltage outputted from the first high voltage generator84and the second direct high voltage outputted from the second high voltage generator85have output voltage values different from each other. The first direct high voltage is set to have the voltage value lower than that of the second direct high voltage. The powder lubricant sprayed from the first spraying portion72aadheres to only the tips of the upper punches5, while the powder lubricant sprayed from the second spraying portion72bis required to adhere to the tips of the lower punches6as well as to the inner peripheral walls of the dies4. Thus, the powder lubricant is electrostatically charged by setting the voltage value of the second direct high voltage to be higher than that of the first direct high voltage, so as to increase the quantity of the powder lubricant adhering to the relevant parts. The first high voltage generator84and the second high voltage generator85may be controlled by the voltage controller86in a manner similar to that of the above Patent Document.

As shown inFIG. 2, in this configuration, the nozzle assembly79is mounted at a position between the powder filling section PFS and the product ejecting section PES in the rotary powder compression molding machine. At this position, the nozzle assembly79is mounted in the vicinity of the turret3with the lower surface of the housing78being partially in contact with the upper surface of the turret3in the lubricant spraying section LJS. In this case, the nozzle assembly79is mounted such that the centers of the through holes74band75bof the respective first and second spraying portions72aand72bare aligned with an extended line of the trajectory100of the centers of the dies4. After the nozzle assembly79is mounted to the frame1, the powder lubricant supply conduits are connected to the connecting pipes77aand77b, respectively. Further, connected to a connecting end that is provided to the nozzle assembly79is an air supply conduit that supplies high pressure air forming an air curtain.

When the rotary powder compression molding machine is in operation, the powder lubricant is supplied to the nozzle assembly79and the electric field generation means8forms an electric field. The powder lubricant is conveyed through each of the connecting pipes77aand77bby an airflow, and reaches the through holes74band75bof the spraying portions72aand72bby way of the guide paths71aand71b, respectively. The powder lubricant is electrostatically charged while passing through the through holes74band75band scatters in the grooves74aand75a, respectively. The grooves74aand75aeach have a width smaller than the diameter of the tip51of the upper punch5or the like. The grooves74aand75aeach have a length greater than the length of the tip51of the upper punch5. Accordingly, the powder lubricant is sprayed from the spraying portions72aand72btoward the upper punches5, the lower punches6, and the die holes41, respectively, not in a circular shape but substantially in a straight line shape.

In such a state where the powder lubricant is continuously sprayed from the respective spraying portions72aand72b, the lower end surfaces of the upper punches5, the upper end surfaces of the lower punches6, and the die holes41pass through the area into which the powder lubricant is sprayed. The powder lubricant is sprayed in the straight line shape, through which the upper punches5, the lower punches6, and the die holes41pass, so that the powder lubricant is regarded to be sprayed entirely to the lower end surfaces of the upper punches5, the upper end surfaces of the lower punches6, and the inner peripheral surfaces of the die holes41. The electrostatically charged powder lubricant is attracted to and adheres substantially evenly to the upper punches5, the lower punches6, and the die holes41each that are electrostatically charged to maintain at the reference potential. As there is an electrostatic attractive force working between the powder lubricant and the adhering surfaces in the state where the powder lubricant adheres thereto, the powder lubricant does not easily fall off the adhering surfaces. In the present embodiment, the path main body76is provided with the first guide path71aand the second guide path71b, and the first guide path71aand the second guide path71bare made to communicate with the first spraying portion72aand the second spraying portion72b, respectively. In this configuration, there occurs no relative displacement between the first spraying portion72aand the second spraying portion72b. In a case where a conventional nozzle in a bar shape is mounted, the powder lubricant is sometimes sprayed in a direction different from a set direction depending on its mounted state. However, in the present embodiment, the path main body76is formed of a thick plate body as well as the first spraying portion72aand the second spraying portion72bare each provided as a plate body, so as to prevent such a conventional problem. The powder lubricant is therefore allowed to securely adhere to the upper punches5, the lower punches6, and the insides of the dies4.

Moreover, as described above, the grooves74aand75aof the first and second spraying portions72aand72binhibit the powder lubricant from scattering radially in planar view around the outlets of the through holes74band75b. In comparison with a conventional nozzle, decreased is the quantity of the powder lubricant that does not adhere but is retrieved, so that improved is efficiency of the powder lubricant. In addition, the powder lubricant sprayed in the straight line shape is made to adhere to the desired regions since the upper punches5, the lower punches6, and the dies4are displaced with respect to the nozzle assembly79. Even in a case where the punch tips each have a shape such as a circular shape, an elliptical shape, or an oval shape, that is, even in a case where the shapes of the products Q are changed, the powder lubricant is allowed to adhere to each of such various shapes using the spraying portions having a uniform shape. Furthermore, the present embodiment adopts the configuration in which the guide paths71aand71bare detachable from the corresponding spraying portions72aand72b, respectively. Therefore, it is possible to easily detach the respective spraying portions72aand72band to prepare spraying portions72aand72bhaving shapes corresponding to the above various shapes of the products.

Below described are results of evaluation tests on adhesion of a powder lubricant employing magnesium stearate in the rotary powder compression molding machine configured as described above. It is quite difficult to directly measure quantities of the powder lubricant adhering to the upper and lower punches5and6as well as to the dies4. Thus, in the adhesion evaluation tests, the products Q were continuously molded for a predetermined period, specifically for five hours, to evaluate degrees of adhesion based on the quantity of the powder lubricant adhering to the products Q during this period.

Upon an adhesion evaluation test, in the rotary powder compression molding machine (hereinafter, referred to as the present machine), a rotational speed of the turret3was set to 40 rpm (rotation/minute), an air volume for spraying the powder lubricant was set to 12 l/min (liter/minute), a purge air volume for sucking the powder lubricant was set to 12 l/min, an exhaust pressure was set to 500 Pa (Pascal), and 10 g of the powder lubricant was supplied to the nozzle structure7per one hour. It should be noted that no voltage was applied to the first electrode81or the second electrode82in this adhesion evaluation test. For the purpose of comparison, another adhesion evaluation test was performed under the conditions same as described above with use of the rotary powder compression molding machine described in International Publication No. WO 2005/110726 Pamphlet (hereinafter, referred to as a comparative machine).

Firstly, in a normal operation of molding a powder material into the products Q with the powder lubricant being sprayed, the products Q were ejected every one hour to measure the quantity of the powder lubricant adhering to the ejected products Q. As a result, each of the products Q had the powder lubricant contained therein of a weight equal to 0.01% of one of the products Q. The same result was obtained with the comparative machine.

Described next are adhesion evaluation tests in which a voltage is applied to the first electrode81and the second electrode82so as to change the adhesion conditions. Measured in these adhesion evaluation tests were the quantities of the powder lubricant contained in each of the products in cases where the applied voltages were set to 20 kV and 40 kV, respectively. Then, in the present machine, the quantities of the powder lubricant contained in each of the products were both 0.04% in both of the cases with 20 kV and 40 kV. On the other hand, with the comparative machine, in the case where the voltage of 20 kV was applied to the electrodes to be charged in order to electrostatically charge the powder lubricant, the quantity of the powder lubricant contained in each of the products was 0.01%, and the quantity was increased to 0.03% in the case of raising the voltage up to 40 kV.

These results prove that the present machine increases adhesion efficiency with the same voltage set.

Described in the above embodiment is the configuration inclusive of the electric field generation means8that electrostatically charges the powder lubricant. However, the electric field generation means8may not be included, that is, an electrostatically uncharged powder lubricant may be sprayed. Upon adopting this configuration in the above embodiment, no electrode mounting hole is obviously required in the path main body76.

Further, described in the above embodiment is the configuration in which the guide paths71aand71beach are formed in the solid core of the path main body76and the path main body76is mounted with the plate bodies74and75having the spraying portions72aand72bprovided thereto, respectively. Alternatively, the nozzles may be formed independently from each other as in the above Patent Document. Specifically, in order to configure one nozzle, a guide path may be formed in a bar or cylindrical member, and a plate body formed with a spraying portion may be mounted onto an end of the member.

In the above embodiment, there is described the air outlet78dthat is used for forming an air curtain. Alternatively, there may be provided an additional air outlet at a predetermined position below the air outlet78din order to inhibit the sprayed powder lubricant from scattering in the lateral direction. Specifically, there may be provided a pair of short air outlets each that are opened along the upper surface of the housing78, so that air curtains are formed on the opposite sides of the width of the groove74aof the first spraying portion72a. Further alternatively, openings of a width substantially same as that of the air outlet78dmay be formed from the opposite ends of the air outlet78ddownwards to reach the upper surface of the housing78.

Correspondingly to the air outlets configured to form the air curtains, in order to suck the excess powder lubricant and thus to increase the retrieval rate thereof, there may be provided another air inlet in addition to the air inlet78edescribed above. Specifically, such an air inlet may be formed so as to be paired with the additional air outlet described above.

Other specific configurations in the respective portions are not limited to the above embodiment, but various modifications are applicable without departing from the objects of the present invention.

INDUSTRIAL APPLICABILITY

Described above is an example in which the present invention is applied in a rotary powder compression molding machine. The present invention is also applicable to any powder compression molding machine that is not of a rotary type but is configured to displace upper and lower punches as well as dies relatively to a nozzle assembly in a nozzle structure.