Patent Application
20050255186
1. Field of the Invention
The present invention relates to injection molding machines and, more particularly, to an electric injection molding machine having a lubrication mechanism and a lubricating method thereof.
2. Description of the Related Art
Generally, an injection molding machine, which performs resin molding, molds a resin component by filling a resin, which has been heated and melted in a heating cylinder, into a cavity of a mold, and cooling and solidifying the resin. Generally, a mold for resin-molding consists of a stationary mold and a movable mold, and opening and closing of the mold is performed by moving the movable mold relative to the stationary mold by a clamping apparatus.
Although various mechanisms can be used for driving the clamping apparatus, an apparatus, which moves the movable mold by attaching a toggle mechanism to the movable mold and driving the toggle mechanism by an electric motor, is used in many cases in recent years. Additionally, there is a system, which converts a rotational movement of an electric motor into a linear movement without using a toggle mechanism and uses the linear movement directly as a drive source. As for such an electric motor for moving a movable mold, there is used generally a servo motor. A ball screw is use as a mechanism for converting a rotational movement of a rotational shaft of the servo motor. Such a ball screw engages with the rotational shaft of the servo motor, and it is a mechanism in which a ball screw nut engages with the ball screw via a plurality of balls. In such a mechanism, when the rotational shaft of the serve motor rotates, the ball screw nut moves relatively in an axial direction of the rotational shaft. Additionally, if the ball screw nut is fixed, the rotational shaft moves relative to the ball screw nut in the axial direction. A moving distance, a moving speed and a moving direction of the ball screw nut or the rotational shaft are determined by an amount of rotation, a rotating speed and a rotating direction of the rotational shaft.
Here, in a case where the ball screw nut is fixed to a housing of the motor, the movable mold (a movable platen) can be driven via a toggle mechanism by connecting a drive part of the toggle mechanism to the rotational shaft of the motor. In this case, at portions where the screw part of the rotational axis and the screw part of the ball screw nut are in contact with the balls, a large load is applied in accordance with a drive force for driving the movable mold (that is, a drive force for driving the toggle mechanism). Accordingly, in order to elongate a service life of the ball screw by suppressing abrasion of the contacting portions of the balls, a lubrication material is supplied to the portions where the balls contact. That is, there are many cases in which a grease is used as a lubrication material in a ball screw drive mechanism used for a conventional injection molding machine (for example, refer to Japanese Laid-Open Patent Application No. 11-151741).
As mentioned above, it is general to use grease as a lubrication material to be supplied to a portion where the balls contact. However, since grease has a low fluidity and a high viscosity, the grease supplied to a part of the ball screw cannot maintain a lubrication film uniformly in its entirety, and a lubricating condition of the entire ball screw may become uneven.
Thus, a large amount of grease must be supplied so that the grease reaches sufficiently to each part of the ball screw. However, according to such a method, an amount of consumption of the grease, which is relatively expensive, is increased, which results in an increase in a maintenance cost of the injection molding machine. Additionally, if the amount of grease is increased, excessive grease scatters in and around the molding machine, which creates an extremely bad environment due to pollution of in surrounding area of the molding machine.
Moreover, since the ball screw operates frequently during an operation of the molding machine and a large load is applied to the contact portions of the balls, a frictional heat is generated at the contact portions of the balls. Thereby, the ball screw becomes a high temperature, which is a factor of reducing the service life of the ball screw. Thus, if a lubrication material supplied to the ball screw has an effect of promoting release of heat or an effect of cooling, the service life of the ball screw can be elongated further. However, the above-mentioned grease provides only a lubricating action by staying at the heat-generating portion, and a heat-releasing effect or a cooling effect cannot be expected.
It is a general object of the present invention to provide an improved and useful molding machine having a lubrication mechanism.
A more specific object of the present invention is to provide a lubrication mechanism of an electric injection molding machine that can elongate a service life of a ball screw by effectively lubricating the ball screw by directly spraying a screw part of the ball screw with a lubrication material and by a cooling effect of a gas used for the spray.
In order to achieve the above-mentioned objects, there is provided according to one aspect of the present invention a molding machine having a lubrication mechanism, comprising: a conversion mechanism that converts a rotational movement of a rotational shaft of a motor, which is a drive source, into a linear movement in an axial direction; and a spray nozzle that sprays an atomized lubrication material onto a component part of the conversion mechanism.
According to the above-mentioned invention, the lubrication material of a liquid state is directly sprayed in the vicinity of a part, which needs lubrication, since the lubrication material is atomized and sprayed over the component part of the conversion mechanism. Accordingly, sufficient lubrication is achieved even if the lubrication material is in a liquid state. Additionally, heat generated by the conversion mechanism is caused to be absorbed by the lubricant material in a liquid state so as to suppress a temperature rise of the conversion mechanism.
In the above-mentioned invention, it is preferable to further comprise a recovery route adapted to recover the lubrication material sprayed from the spray nozzle, wherein the spray nozzle is a nozzle that atomizes the lubrication material of a liquid state by an injection of a gas. Since the atomized lubrication material changes into a liquid state by being brought into contact with the component part, the lubricant material in the liquid state can be recovered and reused. Further, since the liquid state lubrication material, which has absorbed heat of the component part of the conversion mechanism, is recovered, the temperature rise of the conversion mechanism can be suppressed.
Additionally, it is preferable that the gas supplied to the spray nozzle is a compressed air, and the component part of said conversion mechanism is cooled due to adiabatic expansion when the compressed air is injected from the spray nozzle.
In one embodiment of the above-mentioned invention, the recovery means comprises a cover member surrounding the component part of the conversion mechanism, a recovery pipe, which leads the liquid state lubrication material collected in the cover member or the component part of said conversion mechanism, to a recovery container, and a pump for supplying the lubrication material collected in the recovery container to the spray nozzle. It is preferable to have cooling means for cooling the recovered lubrication material.
Additionally, in one embodiment of the present invention, said conversion mechanism is a ball screw mechanism that comprises a ball screw shaft and a ball screw nut, and said spray nozzle is attached to said ball screw nut so as to directly spray the lubrication material inside said ball screw nut. Said spray nozzle may be communicated with an aperture opening in an inner surface of a groove in which balls inside said ball screw nut roll, the aperture opening at a position where no load is applied by the balls. Alternately, said spray nozzle may be communicated with an aperture opening between grooves in which balls inside said ball screw nut roll.
Additionally, the conversion mechanism may be a ball screw mechanism comprising a ball screw shaft and a ball screw nut, and the spray nozzle may be located in the vicinity of the ball screw shaft so as to directly spray the lubrication material onto the ball screw shaft.
A molding machine having the lubrication mechanism according to the present invention may further comprise a temperature detector that detects a temperature of the ball screw nut. Additionally, it may further comprise an iron powder amount detector that measures an amount of iron powder contained in the recovered lubrication material.
Additionally, the molding machine having the lubrication mechanism according to the present invention may be an electric injection molding machine.
Additionally, there is provided according to another aspect of the present invention a lubrication method of a molding machine, comprising spraying an atomized lubrication material to a component part of a conversion mechanism that converts a rotational movement of a rotational shaft of a motor, which is a drive source of a clamping apparatus, into a linear movement in an axial direction. In the lubrication method of a molding machine according to the present invention, it is preferable to spray the lubrication material of a liquid state by atomizing by an injection of a gas, recover the lubrication material that has been sprayed and lubricated the conversion mechanism, and reuse the recovered lubrication material. Additionally, the gas may be a compressed air, and the component part of the conversion mechanism may be cooled due to adiabatic expansion when the compressed air is injected.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.
A description will be given, with reference to the drawings, of a mode for carrying out the present invention.
First, a description will be given of an example of a clamping apparatus of an injection molding machine into which a lubrication mechanism according to the present invention is incorporated.
The clamping apparatus shown in
A stationary mold (not shown in the figure) is attached to a surface of the stationary platen 11 facing the movable platen 12, and a movable mold (not shown in the figure) is attached to a surface of the movable platen facing the stationary platen 11.
A drive apparatus for an ejector is attached to a rear side of the movable platen 12. The drive apparatus for the ejector has a motor 15 as a drive source so as to move an ejector rod 16 forward or rearward. By driving the ejector rod 16, ejector pins (not shown in the figure) are driven so as to push a molded component out of the cavity of the movable mold.
A toggle mechanism 17 is provided between the movable platen 12 and the toggle support 13. Additionally, a drive apparatus 18 as drive means for clamping is provided on a rear end (a left end in
According to the operation of the toggle mechanism 17, the movable platen 12 is moved toward the stationary platen 11 so as to perform mold closing, and a clamping force, which is a thrust force by the motor 19 multiplied by a torque magnifying power, is exerted on the movable platen 12. Thereby, the movable mold attached to the movable platen 12 is pressed against the stationary mold attached to the stationary platen 11 so as to perform mold clamping. It should be noted that although the clamping apparatus shown in
The above-mentioned toggle mechanism 17 comprises a toggle lever 21 movably supported with respect to the cross head, a toggle lever 22 swingably supported with respect to the toggle support 13, and a toggle arm 23 swingably supported with respect to the movable platen 12. Between the toggle lever 21 and the toggle lever 22 and between the toggle lever 22 and the toggle arm 23 are connected by link connections.
The above-mentioned clamping apparatus uses the motor 19 as a drive source of the link mechanism 17, which drives the movable platen 12, and, a ball screw mechanism is incorporated into the motor 19. That is, it is constituted so that one of the ball screw shaft and the ball screw nut of the ball screw mechanism moves in an axial direction when the rotational shaft of the motor 19 rotates, and the toggle mechanism will is also operated in connection with it.
Next, a description will be given, with reference to
In the injection apparatus 100 shown in
Then, a hopper (not shown in the figure) is connected to a resin supply port formed in a predetermined portion of the heating cylinder 112. The resin supply port is formed in the portion at a rear end portion of the groove 126 in a state where the screw 122 is at the forefront position (left side in
Therefore, if the screw 122 is moved rearward by a predetermined distance while rotating during a metering process, pellet-like resin is supplied to the heating cylinder 122 from inside the hopper and the resin is moved in a direction toward the screw head 122a in the groove 126.
Moreover, a heater (not shown in the figure) is provided as heating means around the heating cylinder 122 so that the resin in the groove 126 is melted by heating the heating cylinder 112 by the heater and rotating the screw 122. Accordingly, if the screw is moved rearward by a predetermined distance while rotating, a melted resin corresponding to one shot can be stored in front of the screw head 122a.
Next, if the screw 122 is moved forward without rotation during an injection process, the resin stored in front of the screw head 122a is injected from the injection nozzle 112a, and is filled into the cavity of the mold apparatus.
Behind the heating cylinder 112, a drive part 115 for reciprocating and rotating the screw 122 is provided. The drive part 115 is equipped with a frame 117, a metering motor 181 movably provided to the frame 117 and an injection motor fixed to the frame 117. A motor 182 for injection and the screw 122 are arranged on the same axis.
A guidance bar 183, which extends in parallel with the screw 122, is provided on the frame 117, and the metering motor 181 is moved along the guidance bar 183. Thus, a support board 184 is slidably provided with respect to the guidance bar 183, and the metering motor 181 is attached to the support board 184.
Additionally, a drive-side pulley 186 is fixed to an output shaft 185 of the metering motor 181, and an driven-side pulley 188 is fixed to an outer circumference of a box body 187 of the bearing box 133. A timing belt 189 is provided over the drive-side pulley 186 and the driven-side pulley 188. It should be noted that transmission means connecting the bearing box 113 with the metering motor 181 is constituted by the by the drive-side pulley 186, the driven-side pulley 186 and the timing belt 189.
On the other hand, the motor 182 for injection comprises a stator fixed to the frame 117 and a rotor 192 provided an inner circumference side of the stator 191, and the rotor 192 is rotatably supported with respect to the frame 117. Accordingly, a hollow rotor shaft 193 is fitted and fixed to the rotor 192, and both ends of the rotor shaft 193 are supported on the frame by bearings 194 and 195.
Additionally, bearings 196 and 197 are provided in the bearing box 113, and the screw 122 and a ball screw shaft/spline shaft unit 198 are coupled in a relatively rotatable manner by the bearings 196 and 197. A ball nut 199 fixed to the frame 117 via a load meter 205 as load detecting means is engaged with a ball screw shaft part 198a as a movement direction conversion part formed on a front part of the ball screw shaft/spline shaft unit 198.
It should be noted that drive transmission means for restricting a relative movement in an axial direction and permitting a relative movement in a rotating direction is constituted between the screw 122 and the ball screw shaft/spline shaft unit 198 by the bearing box 113. Additionally, means for converting a rotational movement into a linear movement is constituted by the ball nut 199 and the ball screw shaft part 198a.
Accordingly, when the metering motor 181 is driven in the metering process, the rotation of the metering pump is transmitted sequentially to the drive-side pulley 186, the timing belt 189, the box body 187 and the screw 122, and the screw 122 is rotated. In this case, since the screw 122 and the ball screw shaft/spline shaft unit 198 are coupled relatively rotatably via the bearing box 113, the rotation transmitted to the box body 187 is not transmitted to the ball screw shaft/spline shaft unit 198. On the other hand, a pressure of the resin in the heating cylinder 112 is transmitted to the ball screw shaft/spline shaft unit 198 via the bearing box 113. Accordingly, the ball screw shaft/spline shaft unit 198 moves rearward while rotating, and, in connection with this, the screw is caused to rotate and move rearward. It should be noted that a back pressure is applied to the screw 122 against the pressure of the resin when the screw 122 is moved rearward.
On the other hand, the screw 122 can be gradually advanced without rotating the screw 122 by supplying an electric current of a predetermined frequency to the stator 191 in the motor 182 for injection. In order for that, an annular engaging member 201 is fixed to a substantially middle of an inner side of the rotor shaft 193. Additionally, a spline 202 formed on an inner circumference of an engagement member 201 is brought into engagement with a spline shaft part 198a as a rotation transmission part formed on an outer circumference of a rear part of the ball screw shaft/spline shaft unit 198. It should be noted that rotation transmission means by which a rotation of the motor 82 for injection motor 82 is transmitted is constituted by the spline 102 and the spline shaft part 198b.
Accordingly, when the motor 182 for injection is driven in the injection process, the rotation of the motor 182 for injection is transmitted sequentially to the rotor shaft 193, the engagement member 201 and the screw shaft/spline shaft unit 198. Thus, since the ball nut 199 is fixed to the frame 117, the screw shaft/spline shaft unit 198 is rotated and also moved forward, which moves the screw 122 forward without rotation. Additionally, at this time, the injection pressure applied to the screw shaft/spline shaft unit 198 is transmitted to the load meter 205 via the ball nut 199, and is detected by the load meter 205. It should be noted that the screw shaft/spline shaft unit 198 is moved forward or rearward in the axial direction by a stroke S.
Although the metering motor 181 and the screw shaft/spline shaft unit 198 are arranged on different axes in the above-mentioned example, the motor for injection, the ball screw shaft/spline unit and the screw may be arranged on different axes from each other.
Next, a description will be given, with reference to
The
As mentioned above, since a power is transmitted between the ball screw shaft 26 and the ball screw nut 25 while the plurality of balls 27 roll, there is almost no slide friction between the ball screw shaft 26 and the ball screw nut 25, thereby transmitting a power smoothly. Accordingly, when the ball screw nut 25 is fixed, the rotational movement of the ball screw shaft 26 is efficiently changed into the linear movement in the axial direction of the ball screw shaft 26.
Although the power transmission members of the above-mentioned ball screw mechanism are the plurality of balls, a plurality of rollers having about the same size as the balls may be used as the power transmission members. Additionally, a planetary roller may be used as the power transmission members. It should be noted that the rotational/linear movement converting mechanism using a plurality of rollers or the rotational/linear movement converting mechanism using a planetary roller is well-known, and a detailed description thereof will be omitted.
Next, a description will be given of the lubrication mechanism according to a first embodiment of the present invention.
The drive apparatus 30 shown in
The drive apparatus 30 comprises a motor 19 as a power source and a ball screw mechanism 31 driven by the motor 19. The motor 19 is an electric servo motor of which rotating direction and rotating speed are controllable. The ball screw mechanism 31 has the ball screw nut 25 and the ball screw shaft 26 as shown in the
A moving member 32 is attached to an end of the ball screw shaft 26 via a baring. The moving member 32 is connected to the cross head 20 of the toggle mechanism 17 so that the toggle mechanism 17 operates with a reciprocating movement of the moving member. Additionally, when the drive apparatus 30 is provided to the injection apparatus, the moving member 32 corresponds to the box body 187 of the bearing box 113.
In the present embodiment, a generally cylindrical cover member 33 is provided so as to cover the ball screw mechanism 31 and the moving member 32. The moving member 32 is constituted to be movable in the cover member 33, and a seal member 34 is provided between the moving members 32 and the cover member 33 so as to form a sealed space 45.
A spray nozzle 35 for spraying lubrication oil, which is the lubrication material for lubricating the ball screw mechanism 31, is attached to the cover member 33. In the present embodiment, an end portion of the spray nozzle 35 extends to inside the ball screw nut 25 so as to directly spray the atomized lubrication oil inside the ball screw nut 25 as mentioned later.
The lubrication oil and compressed air are supplied to the spray nozzle 35 so as to atomize the lubrication oil into appropriate particles by powerfully injecting the compressed air from a nozzle tip. The atomized lubrication oil adhere onto the ball groove of the ball screw shaft 26 and the ball groove of the ball screw nut 25 an surfaces of the balls 27, which are component parts of the ball screw mechanism so as to form lubrication oil films at contact portions between each of the ball groove of the ball screw shaft 26 and the ball groove of the ball screw nut 25 and each of the balls 27.
Under this circumstance, the compressed air injected inside the ball screw nut 25 adiabatically expands, thereby absorbs heat in surrounding area. That is, the balls 27, the ball screw nut 25 and the ball screw shaft 26 of which temperatures are raised due to friction heat generated by a movement of the balls inside the ball screw nut 25 are cooled by the adiabatically expanded injection air.
Additionally, the lubrication oil turned into a liquid state by adhering onto the balls 27, the ball screw nut 25 and the ball screw shaft 26 is discharged from the inside of the ball screw nut 25. Under this circumstance, the lubrication oil also absorbs heat from the surrounding area and discharged from the inside of the ball screw nut 25, there also is a cooling effect by the lubricant oil itself.
It should be noted that although the lubrication oil is atomized using the compressed air in the present embodiment, the gaseous matter (gas) for atomization is not limited to the compressed air. For example, an inert gas such as nitrogen (N2) or a nontoxic compressible gas such as carbon dioxide (CO2) may be used as the gas for atomization.
An aperture (opening) for recovering the lubrication oil is provided in a lower-side portion of the ball screw nut 25 and a lubrication oil recovery pipe 36 is connected thereto. The lubrication oil recovery pipe 36 extends through the cover member 33, and is connected to the lubrication oil recovery tank 37. Accordingly, the lubrication oil turned into a liquid state in the ball screw nut 25 flows into the lubrication oil recovery pipe 35, and is guided to the lubrication oil recovery tank 37. An iron amount detector 39 and a cooler 40 are provided in the middle of the lubrication oil recovery pipe 36.
The iron amount detector 39 detects an amount of iron component contained in the lubrication oil. The iron component contained in the lubrication oil is caused by abrasion of component parts of the ball screw mechanism 31, and, thus, an amount of abrasion of the ball screw mechanism 31 can be estimated by detecting the amount of iron component. Accordingly, an operator or a maintenance can estimate a service life of the ball screw mechanism by causing the detection result of the iron amount detector 39 to be displayed on a display unit. Additionally, the detection result of the iron amount detector 39 may be supplies to a controller to calculate a service life and display or an operator is notified of a fact that a service life of the ball screw mechanism is ended when an amount of iron component exceeds a predetermined value.
The cooler 40 is for cooling the recovered lubrication oil. As mentioned above, the lubrication oil collected from the ball screw nut 25 has a high temperature due to absorption of heat from the ball screw nut 25 and the ball screw shaft 26, and it is for reuse by cooling it.
It should be noted that a part of the lubrication oil in the ball screw nut leaks out from an end of the ball screw nut 25, and stored in the cover member 33. An aperture (opening) 33a for discharging the lubrication oil is provided in a lower portion of the cover member 33, and a lubrication oil recovery pipe 38 is connected thereto. The lubrication oil recovery pipe 38 is connected to the lubrication oil recovery tank 37, and, thus, the lubrication oil stored in the bottom portion of the cover member 33 flows through the lubrication oil recovery pipe 38 and is guided to the lubrication oil recovery tank 37. It should be noted tat the lubrication oil recovery pipe 38 is not limited to a pipe having a totally closed cross section, and a garter or a channel through which the lubrication oil can flow may be used. The lubrication oil recovery pipe 38 or the garter forms a recovery route to recover the lubrication oil.
The lubrication oil recovery tank 37 is provided with a recessed portion 37a on the bottom of the center so as to be configured so that impure ingredient such as metal powder (iron powder) or the like contained in the flowing lubricant oil is stored therein. The impure ingredient stored in the recessed portion 37a is discharged by opening a drain valve periodically or when accumulated in some amount.
The lubrication oil recovered and stored in the lubrication oil recovery tank 37 is suctioned by a lubrication oil pump 41, and is supplied to the spray nozzle 35 through a lubrication oil supply pipe 42. The lubrication oil supplied to the spray nozzle 35 is atomized by injection of the compressed air supplied through a compressed air supply pipe 43, and sprayed inside the ball screw nut 25 again.
Thus, in the present embodiment, since the lubrication oil is circulated and is reused, the cost spent on lubrication can be reduced. Moreover, a service life can be estimated by detection of iron using the recovered lubrication oil as mentioned above, and the recovered lubrication oil can be reused by cooling it. Additionally, since the cover 33 forms the sealed space 45, heat generated by the ball screw does not leak to a surrounding area of the drive apparatus, and, therefore, a temperature of the surrounding area of the drive apparatus can be prevented from rising.
It should be noted that the cooling effect can be checked by detecting a temperature of the ball screw nut 25 by providing a temperature sensor 44 to the ball screw nut 25, and the ball screw mechanism 31 can be efficiently cooled by adjusting an amount of supply and a temperature of the lubrication oil.
Moreover, although the iron amount detector 39 and the cooler 40 are provided in the middle of the lubrication oil recovery pipe 36 in the example shown in
Next, a description will be given of a position of spraying the lubrication oil in the ball screw nut 25.
In the example shown in
Moreover, since the ball screw incorporated into the injection molding machine receives a load mainly only in one direction, the load is applied to only one side of the ball screw groove. Thus, the opening may be provided at a position of the ball screw groove offset in a direction where no load is received.
When the ball screw shaft 26 moves in the ball screw mechanism 31, the balls 27 are brought into contact with a side surface portion in the inner surface of the ball screw groove of the ball screw nut 25. That is, a load is hardly applied to a center portion of the ball screw groove. In the example shown in
It should be noted that a lubrication oil recovery aperture 25b is provided to a lower portion of the opposite side of the lubrication oil supply aperture 25a, and the lubrication oil recovery pipe 36 is connected thereto. The atomized lubrication oil sprayed from the spray nozzle 35 hits the balls 27 by passing through the lubrication oil supply aperture 25a and adheres onto the surfaces of the balls 27 so as to form lubrication oil films. The lubrication oil lubricating the balls 27 is stored in a lower part of the inside of the ball screw nut 25, and is discharged outside the ball screw nut 25 through the lubrication oil recovery aperture 25b and the lubrication oil recovery pipe 36.
In the example shown in the
It should be noted that although one spray nozzle 35 is provided in the examples shown in
Moreover, generally, seal materials are provided on both ends of the ball screw nut 25 so as to store the lubrication oil in the ball screw nut 25. However, seal materials are not provided in the present invention so as to configure so that the lubrication oil and the compressed air can be easily discharged from both ends of the ball screw nut 25. Accordingly, the compressed air injected from the spry nozzle 35 is rapidly discharged from the ball screw nut 25. Thereby, the spray of the lubrication oil can be performed efficiently in the ball screw nut 25, which causes the atomized lubrication oil being efficiently diffused to an entire interior of the ball screw nut 25.
Next, a description will be given, with reference to
Although the lubrication mechanism shown in
It should be noted that although the lubrication oil is used as a lubrication material in the above-mentioned first and second embodiments, any lubrication materials may be used if they are in a liquid state and can be atomized by the spray nozzle 35.
Moreover, although the ball screw mechanism is explained as an example in the above-mentioned first and second embodiments, it can be applies to a rotational/linear movement conversion mechanism according to a roller screw mechanism or a planetary gear.
It should be noted that the example in which the present invention is applied to the clamping drive part and the injection drive part is mainly explained in the present embodiments. The present invention can be more effectively applied in a case it is applied to an injection apparatus in which a maximum load is generated over a whole injection stroke than in a case where it is used for a ball screw in which a section where a maximum load is generated is a part of a hole opening and closing stroke. Additionally, the same effect is obtainable when applying the present invention to an ejector apparatus, a plasticizer moving apparatus or the like.
The present invention is not limited to the specifically disclosed embodiments, and various variations and modifications may be made without departing from the scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-017556 | Jan 2003 | JP | national |
This application is a U.S. continuation application filed under 35 U.S.C. 111(a) claiming benefit under 35 U.S.C. 120 and 365(c) of PCT application JP2004/000578, filed Jan. 23, 2004, which claims priority to Application Ser. No. 2003-017556, filed in Japan on Jan. 27, 2003. The foregoing applications are hereby incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP04/00578 | Jan 2004 | US |
| Child | 11188812 | Jul 2005 | US |
