Patent Description:
Injection molding machines are generally classified as hydraulic injection molding machines and electric injection molding machines. <CIT> describes a method for converting a hydraulic injection molding machine into an electric injection molding machine. According to this method, when converting a hydraulic injection molding machine into an electric injection molding machine, the output shaft of the gear reduction gear and the screw drive shaft are connected by a shaft coupling.

An injection molding machine mainly comprises an injection unit and a mold clamping unit. When manufacturing an injection molding machine, a mold clamping unit may be combined with one injection unit selected from a number of types. At this time, if the length of the screw of the selected injection unit is insufficient, it is possible to apply the idea described in <CIT> and attach a connecting shaft to the screw to compensate for the insufficient length.

When a connecting shaft is attached to a screw to substantially extend the length of the screw, the screw may tilt due to the weight of the connecting shaft, causing the screw to possibly come into contact with the cylinder. If, as a consequence, fine powder is generated that mixes with the injection material or the injection material is abnormally heated and thus discolored, the quality of the molded product may be affected.

An object of the present disclosure is to provide an injection unit that can suppress inclination of a screw to which a connecting shaft is attached.

The injection unit of the present disclosure includes a cylinder, a screw at least a part of which is housed inside the cylinder, a connecting shaft that connects the screw and a drive shaft that drives the screw, and a support member for the connecting shaft. The support member is located between the screw and the drive shaft, allows rotation and axial movement of the connecting shaft, and supports the connecting shaft at least in the vertical direction.

An embodiment of injection unit <NUM> and injection molding machine <NUM> equipped with injection unit <NUM> according to the present invention will be described with reference to the drawings. <FIG> shows a schematic front view of injection molding machine <NUM> according to this embodiment. Injection molding machine <NUM> generally comprises mold clamping unit <NUM> that clamps a mold, and injection unit <NUM> that heats and melts the material to be injected and injects the material. In the following description, the axial direction or direction of movement of screw <NUM> will be referred to as the X-direction. The X-direction is parallel to the horizontal direction. The direction in which screw <NUM> moves toward movable platen <NUM>, or the direction in which the material is ejected, is referred to as the +X-direction, and the direction in which screw <NUM> moves away from movable platen <NUM> is referred to as the -X-direction. The vertical direction is called the Z-direction.

Mold clamping unit <NUM> comprises fixed platen <NUM> fixed on bed <NUM> and on which fixed mold M1 is mounted, mold clamping housing <NUM> that is slidable on bed <NUM>, and movable platen <NUM> that can slide on bed <NUM> and on which movable mold M2 is mounted. Fixed platen <NUM> and mold clamping housing <NUM> are connected by a plurality of tie bars <NUM>. Mold clamping mechanism <NUM> for opening and closing the mold is provided between movable platen <NUM> and mold clamping housing <NUM>. By closing the mold, a cavity (not shown) is formed between fixed mold M1 and movable mold M2. Mold clamping mechanism <NUM> comprises toggle mechanism <NUM> and mold clamping motor <NUM> that drives toggle mechanism <NUM>. Although not shown, mold clamping mechanism <NUM> may be a direct pressure mold clamping mechanism, that is, a hydraulic mold clamping cylinder.

Injection unit <NUM> is provided on base <NUM>. Injection unit <NUM> comprises cylinder <NUM>, screw <NUM> at least a part of which is housed inside cylinder <NUM>, and drive mechanism <NUM> that drives screw <NUM>. Screw <NUM> is rotationally driven by drive mechanism <NUM> and is also driven in the X-direction. That is, screw <NUM> is rotatable around the X-direction axis C of screw <NUM> and movable in the axial direction of cylinder <NUM> (X-direction). Drive mechanism <NUM> is covered with a cover (not shown). Hopper <NUM> for supplying material to be injected is provided near the end of cylinder <NUM> in the -X-direction.

Injection nozzle <NUM> is provided at the tip of cylinder <NUM> in the +X-direction to abut against fixed mold M1 and supply injection material to the cavity. Injection unit <NUM> includes nozzle touch mechanism <NUM>. Nozzle touch mechanism <NUM> moves injection unit <NUM> forward, thereby causing injection nozzle <NUM> to touch sprue bush M3 of fixed mold M1. Nozzle touch mechanism <NUM> connects drive mechanism <NUM> and fixed platen <NUM>. Nozzle touch mechanism <NUM> is often configured with a hydraulic device.

<FIG> is a front view showing a part of injection unit <NUM>. Screw <NUM> is shown in a state of having moved to its limit in the +X-direction. Drive mechanism <NUM> comprises drive shaft <NUM> that drives screw <NUM> via connecting shaft <NUM>, rotation drive unit <NUM> that rotates drive shaft <NUM> around axis C that is aligned in the X-direction, and axial drive unit <NUM> that rotates drive shaft <NUM> in the axial direction (X-direction). Rotation drive unit <NUM> and the axial drive unit <NUM> can be configured using a motor, a reduction device, etc., but can also be configured using a hydraulic device. As drive shaft <NUM> rotates, connecting shaft <NUM> connected to drive shaft <NUM> and screw <NUM> connected to connecting shaft <NUM> also rotate. When connecting shaft <NUM> moves in the axial direction (X-direction), drive shaft <NUM> and screw <NUM> also move in the axial direction. Drive shaft <NUM> has connection hole <NUM> that receives end region 41D of connecting shaft <NUM> in the -X-direction.

Connecting shaft <NUM> connects screw <NUM> and drive shaft <NUM>. Connecting shaft <NUM> comprises connection part 41A connected to screw <NUM>, transition part 41B connected to connection part 41A, and main body part 41C connected to transition part 41B. Connection part 41A, transition part 41B, and main body part 41C have circular cross sections. Since connection part 41A surrounds the side surfaces of end region 33B of screw <NUM> in the -X-direction, connection part 41A has an outer diameter larger than the outer diameter of end region 33B. The outer diameter of main body part 41C is smaller than the outer diameter of connection part 41A. Transition part 41B is provided for the transition between different diameters of connection part 41A and main body part 41C.

Connecting hole <NUM> for receiving end region 33B is provided at the +X-direction end of connection part 41A. Splines are provided on the inner surface of connecting hole <NUM> and the side surface of end region 33B. Since connection part 41A is spline-connected to screw <NUM> in this manner, rotation of connecting shaft <NUM> with respect to screw <NUM> is prevented.

End region 41D in the -X-direction of main body part 41C is supported by connecting hole <NUM> of drive shaft <NUM>. The outer diameter of end region 41D is the same as the outer diameter of the other portion of main body part 41C. Splines are provided on the inner surface of connecting hole <NUM> in the -X-direction and on the side surface of end region 41D of main body part 41C. Since connecting shaft <NUM> is spline-connected to drive shaft <NUM> in this manner, rotation of connecting shaft <NUM> with respect to drive shaft <NUM> is prevented. The outer diameter of main body part 41C (end region 41D) can be determined according to the inner diameter of connecting hole <NUM>.

Inner restraining member <NUM> is provided at the end in the +X-direction of connecting shaft <NUM> to prevent movement of connecting shaft <NUM> in the X-direction with respect to screw <NUM>. Screw <NUM> comprises a cylindrical main part 33A in which flights 33C are formed, and a cylindrical end region 33B located outside of cylinder <NUM>, and inner restraining member <NUM> is attached to screw <NUM> in end region 33B. Groove <NUM> is provided on the outer surface of connection part 41A of connecting shaft <NUM>, and inner restraining member <NUM> includes claw part 47A that fits into groove <NUM>.

Outer restraining member <NUM> is provided at a portion of connecting shaft <NUM> adjacent to drive shaft <NUM> to prevent movement of connecting shaft <NUM> in the X-direction with respect to drive shaft <NUM>. Groove <NUM> is provided on the outer surface of drive shaft <NUM>, and outer restraining member <NUM> has claw part 49A that fits into groove <NUM>.

Explanation next regards the reason for providing connecting shaft <NUM>. Injection molding machine <NUM> mainly comprises a mold clamping unit and an injection unit, but the mold clamping unit and the injection unit do not necessarily have a one-to-one correspondence. For example, one injection unit selected from a plurality of types of injection units may be combined with a certain mold clamping unit. In the case of a standard combination of an injection unit and a mold clamping unit, no special modification of the mold clamping unit and the injection unit is required regardless of which injection unit is selected.

On the other hand, depending on the specifications of the molded product, a user may choose a combination other than the standard combination of an injection unit and a mold clamping unit. For example, since a large-sized mold clamping unit is used for manufacturing large-sized molded products, the large-sized mold clamping unit is generally combined with an injection unit having a large injection volume. For this reason, a large mold clamping unit is typically combined with an injection unit with a large injection volume. However, when manufacturing a molded product that is large in plan but thin, a large-sized mold clamping unit is required but the use of an injection unit with a small injection volume may be preferable. In this case, after having selected an injection unit of the standard combination, screw <NUM> and cylinder <NUM> may be replaced by equivalent components of an injection unit having a smaller injection volume. Since drive mechanism <NUM> (motor, etc.) of the injection unit has a sufficient margin with respect to the injection volume, no major problem arises regarding the material injection performance.

However, in an injection unit having a small injection volume, because screw <NUM> and cylinder <NUM> are generally short in length, when screw <NUM> is directly connected to drive shaft <NUM>, the tip of cylinder <NUM> in the +X-direction is accordingly moved relatively far from the mold. Therefore, the distance that cylinder <NUM> moves in the X-direction becomes longer. If this movement distance cannot be realized due to functional constraints of nozzle touch mechanism <NUM> such as limitations on the stroke of a hydraulic cylinder, injection nozzle <NUM> will not be able to contact sprue bush M3 of the mold. Therefore, in order to compensate for the inadequate distance between screw <NUM> and cylinder <NUM>, connecting shaft <NUM> is connected to screw <NUM>, and spacer member <NUM> that surrounds connecting shaft <NUM> is attached to cylinder <NUM>.

The lengths of connecting shaft <NUM> and spacer member <NUM> are not limited as long as injection nozzle <NUM> can touch sprue bush M3, but the lengths of screw <NUM> and cylinder <NUM> of the selected standard combination of injection units are preferably determined to remain substantially unchanged. That is, if the screw length of the injection unit of the selected standard combination is S1, the length of connecting shaft <NUM> in the X-direction is S2, and the length of the replaced screw (screw <NUM> in this embodiment) is S3, it is preferable to determine S2 such that S1 = S2 + S3. Similarly, if the cylinder length of the injection unit of the selected standard combination is C1, the length of spacer member <NUM> in the X-direction is C2, and the length of the replaced cylinder (cylinder <NUM> in this embodiment) is C3, it is preferable to determine C2 such that C1 = C2 + C3.

By setting the lengths of connecting shaft <NUM> and spacer member <NUM> in this manner, the substantial screw length of connecting shaft <NUM> and screw <NUM> matches the screw length of the injection unit of the selected standard combination. Furthermore, the combined substantial cylinder length of spacer member <NUM> and cylinder <NUM> matches the cylinder length of the injection unit of the selected standard combination. Therefore, parts of the injection unit of the selected standard combination, such as nozzle touch mechanism <NUM> and the running rail (not shown) of injection unit <NUM> provided on base <NUM> can be used without alteration.

Spacer member <NUM> is made of metal. Spacer member <NUM> is a generally cylindrical member that extends in the X-direction as a whole and encloses connecting shaft <NUM>. Spacer member <NUM> comprises a cylindrical base part 51A that is attached to cylinder <NUM>, a cylindrical body part 51B that is connected to base part 51A, and a cylindrical end part 51C that is connected to body part 51B. These may be integrally formed or may be joined by bolts, welding, or the like.

The injection unit <NUM> includes support member <NUM>. Support member <NUM> comprises bush <NUM> fitted around connecting shaft <NUM> and attachment part <NUM> to which bush <NUM> is attached. Attachment part <NUM> is a generally circular member when viewed from the X-direction, and its outer peripheral portion is fixed to end part 51C of spacer member <NUM> with bolts <NUM>. Bush <NUM> is a cylindrical member and is fitted to attachment part <NUM> so as to be in contact with attachment part <NUM> around the entire circumference. Therefore, a member for fixing bush <NUM> to attachment part <NUM> is not required, and the structure of support member <NUM> is simplified. Support member <NUM> allows rotation of connecting shaft <NUM> around the X-direction axis C, allows movement in the axial direction (X-direction), and supports connecting shaft <NUM> at least in the vertical direction Z.

Bush <NUM> is preferably an oilless bush. Since there is no need to inject lubricating oil between bush <NUM> and connecting shaft <NUM>, little maintenance is required. The material of bush <NUM> may be either metal or resin. Examples of the resin material include tetrafluoroethylene, polyphenylene sulfide, polyetheretherketone, thermoplastic polyimide, polyamide, polyamideimide, and polyetherimide. Examples of the metal material include pure iron-based, iron-copper-based, iron-bronze-based, iron-carbon-graphite-based, bronze, and bronze-based sintered materials as specified in Japanese Industrial Standard Z2550: <NUM> ("Sintered Metal Materials - Specifications"), cast iron with internal space impregnated with lubricating oil, and graphite-filled copper alloy having embedded lubricating oil and formed with a drilled cylindrical hole.

Since support member <NUM> supports the weight of connecting shaft <NUM>, it is possible to reduce or eliminate any inclination of screw <NUM> that is connected to connecting shaft <NUM>. Since connecting shaft <NUM> is connected to screw <NUM>, any tilting of connecting shaft <NUM> due to the weight of connecting shaft <NUM> will affect screw <NUM>. If screw <NUM> tilts inside cylinder <NUM>, screw <NUM> may come into contact with the inner wall of cylinder <NUM> during rotation and/or movement of screw <NUM>, and fine powder may be generated. If generated fine powder mixes with the injection material, there is a possibility that the fine powder will be mixed into the molded product. Furthermore, the heat generated by the contact between screw <NUM> and cylinder <NUM> may cause abnormal heating and discoloration of the surrounding injection material. In transparent molded products such as light guide plates and lenses, fine powder and discolored parts are visible from the outside as defects such as black spots and yellowed parts and may have a significant impact on product yield.

Since support member <NUM> is located between screw <NUM> and drive shaft <NUM> and supports connecting shaft <NUM>, any inclination of connecting shaft <NUM> will be reduced, whereby any inclination of screw <NUM> is reduced and any contact between screw <NUM> and cylinder <NUM> is prevented. In order to reduce the inclination of connecting shaft <NUM>, support member <NUM> is preferably installed near the middle between screw <NUM> and drive shaft <NUM>. However, since connecting shaft <NUM> moves in the -X-direction together with screw <NUM> as shown by the broken lines in <FIG>, connection part 41A and transition part 41B of connecting shaft <NUM> must be prevented from coming into contact with support member <NUM>. For this reason, support member <NUM> is installed between drive shaft <NUM> and the position of maximum retraction of transition part 41B in the -X-direction.

As shown in <FIG>, attachment part <NUM> includes holding part <NUM> that holds the tip of bush <NUM> that is closer to screw <NUM> (the tip in the +X-direction). Holding part <NUM> has a generally cylindrical shape. Screw <NUM> and connecting shaft <NUM> move at high speed in the +X-direction during an injection process, and holding part <NUM> reduces the possibility that bush <NUM> will be dragged in the +X-direction by connecting shaft <NUM> and detach from attachment part <NUM> during the injection process. In order to prevent holding part <NUM> from coming into contact with connecting shaft <NUM>, the height of holding part <NUM> is preferably slightly lower than the thickness of bush <NUM>. That is, inner diameter D1 of holding part <NUM> is preferably slightly larger than inner diameter D2 of bush <NUM>.

On the other hand, during a measurement process, screw <NUM> and connecting shaft <NUM> move in the -X-direction at a lower speed than during the injection process. Since there is a little possibility that bush <NUM> will detach from attachment part <NUM> during the measurement process, there is less need to hold bush <NUM> by attachment part <NUM>. Therefore, with the exception of holding part <NUM>, the inner diameter D3 of attachment part <NUM> is approximately equal to outer diameter D4 of bush <NUM>.

Similar to <FIG>, <FIG> shows a front view of a first modification of injection unit <NUM>. In this modification, connecting shaft <NUM> has a constant diameter in section F in which support member <NUM> can face connecting shaft <NUM>, this diameter being equal to the diameter of connection part 41A that connects with screw <NUM>. In other words, section F is included in connection part 41A. In <FIG>, screw <NUM> is at the position of maximum movement in the +X-direction. When cylinder <NUM> and connecting shaft <NUM> move in the -X-direction from this state, inner restraining member <NUM> comes to the position indicated by the broken lines. For convenience, if it is assumed that connecting shaft <NUM> is fixed and support member <NUM> moves, support member <NUM> moves relative to connecting shaft <NUM> to the position indicated by the broken lines. Support member <NUM> is movable relative to connecting shaft <NUM> in this section F because connecting shaft <NUM> has a constant diameter in the section F between the position where support member <NUM> is drawn with solid lines and the position where support member <NUM> is drawn with broken lines.

Support member <NUM> can therefore be installed closer to the screw <NUM> side, that is, closer to the midpoint between screw <NUM> and drive shaft <NUM>, and any inclination of connecting shaft <NUM> can be further reduced. In this modification, support member <NUM> must be prevented from coming into contact with inner restraining member <NUM> at the position where cylinder <NUM> is most retracted in the -X-direction.

<FIG> show diagrams of a second modification similar to the configuration of <FIG>. Since support member <NUM> need only support connecting shaft <NUM> at least in the vertical direction Z, the entire circumference of connecting shaft <NUM> need not be supported. Bush <NUM> does not have to be cylindrical. In this modification, bush <NUM> comprises only a lower semicircular part in the vertical direction Z, and accordingly, attachment part <NUM> also comprises only a lower half part.

Claim 1:
An injection unit (<NUM>) comprising:
a cylinder (<NUM>);
a screw (<NUM>) at least a part of which is housed inside the cylinder (<NUM>) and that is rotatable and movable in an axial direction of the cylinder (<NUM>);
a drive shaft (<NUM>) that drives the screw (<NUM>);
a connecting shaft (<NUM>) that connects the screw (<NUM>) and the drive shaft (<NUM>); and
a support member (<NUM>) that is located between the screw (<NUM>) and the drive shaft (<NUM>), that allows rotation and movement in the axial direction of the connecting shaft (<NUM>), and that supports the connecting shaft (<NUM>) at least in a vertical direction;
characterized in that the injection unit (<NUM>) further comprising a spacer member (<NUM>) that is connected to the cylinder (<NUM>) and that encloses the connecting shaft (<NUM>), wherein
the support member (<NUM>) includes a bush (<NUM>) fitted to the connecting shaft (<NUM>) and an attachment part (<NUM>) for the bush (<NUM>) attached to the spacer member (<NUM>).