RU2364506C2 - Driver assembly for transference of rotary and linear motion to shaft - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention deals with design of driver assemblies for pressure casting machines. The driver assembly contains a cylinder for reception of a pressurised liquid medium that is mounted onto the casting machine shaft and an electric motor having a hollow shaft. The cylinder has an inner and an outer surfaces and is mounted so that to be capable of rotation. The crowned piston remains in a sliding contact with the cylinder inner surface and is mounted so that to be capable of rotation. The shaft design enables axial displacement under the liquid medium pressure through the cylinder towards the piston crown. The electric motor has housing, rotor and stator. The stator is mounted on the housing wall with the rotor connected to the cylinder outer surface. The rotor is designed to provide for rotation of the piston and rotation of the pressure casting machine shaft.

EFFECT: invention enables enhancement of the injector assembly injection properties.

12 cl, 13 dwg

Description

FIELD OF THE INVENTION

The present invention relates to a drive device for communicating rotational and translational motion to a shaft. In particular, the present invention can be used to drive a plasticizing screw in an injection molding machine. More specifically, the present invention relates to a drive device for communicating rotational and translational motion to a plasticizing screw in an injection molding machine in which the screw is rotationally driven by a hollow motor and reciprocates under the influence of a piston of a hydraulic cylinder.

State of the art

It is known to use hollow motors and pistons of hydraulic cylinders to drive plasticizing augers into motion and communicate rotational motion to them. However, none of the known systems provides for the simultaneous obtaining of the benefits provided by the use of electric motors for rotation of the plasticizing screw in combination with imparting to it translational motion in the longitudinal direction by means of a piston of a hydraulic cylinder.

In the description of the invention to US patent No. 4105147, issued in the name of Stubbe (Stubbe), a screw extruder is disclosed, driven in rotational motion by means of a gear transmission from an electric motor and moved in the longitudinal direction by means of a piston of a hydraulic cylinder. The end part of the screw is made in the form of a splined shaft with the possibility of sliding of this shaft in the longitudinal direction inside the gear transmission.

U.S. Patent No. 4,895,505, issued to Fanuc Ltd., discloses a linear electric motor for linearly moving the injection auger. A linear electric motor includes a corresponding series of permanent magnets mounted on the anchor of this electric motor, which interact with an alternating electric current passed through the stator windings, covering the armature, as a result of which linear motion of the motor armature and the screw shaft fixed to this is communicated anchor. The patent discloses the use of a hollow motor for linearly moving a screw shaft.

In the description of the invention to US patent No. 5540495, issued July 30, 1996 in the name of Krauss-Maffei (Krauss-Maffei), an extruder screw drive is disclosed, which includes a first electric motor for communicating translational movement of the screw and a second electric motor for messages of rotational movement to the screw. The embodiment of the invention discussed in the description of the invention to this patent involves the use of two hollow electric motors. The drive device for communicating the translational movement of the screw and the sliding device for communicating the rotational movement of the screw are designed so that one of them partially fits inside the other.

In the description of the invention to US patent No. 5645868, issued in the name of Reinharta (Reinhart), discloses a drive device for an injection unit, which includes a hollow electric motor, introduced into engagement with the shaft of the screw using three couplings. One such clutch communicates rotational movement of the screw, the second ensures the movement of the screw in the forward direction, and the third prevents the rotational movement of the screw while moving it in the forward direction. The use of any hydraulic components is not provided here.

U.S. Pat. No. 5,747,076, issued to Jaroschek et al., Discloses an injection molding machine that utilizes a hydraulic cylinder piston to facilitate movement of a screw driven by an electric motor transmitting to torque through the corresponding rack gear mechanism.

In the description of the invention to US patent No. 5804224, issued 08.09.1998 company "Fanuc Limited" (Fanuc Ltd.), disclosed a device that provides for the use of a screw with a ball nut, made in one piece with the rotor shaft. In this case, the rotation of the screw with a ball nut is carried out using an electric motor located coaxially to the specified shaft.

In the description of the invention to US patent No. 5891485, issued 06.04.1999 in the name of Sumitomo (Sumitomo), an injection device is disclosed, which includes two electric motors with a hollow shaft. One of these electric motors is designed to rotate the screw shaft, while the other electric motor moves the shaft in the longitudinal direction. The rotors of these two electric motors are connected to the shaft. In addition, each rotor is located in a separate chamber.

In the description of the invention to US patent No. 6068810, issued in the name of Kestle (Kestle) and others, discloses an injection unit having a hollow shaft located inside the piston, which under the influence of hydraulic pressure provides retraction and extension of the screw. The corresponding electric motor communicates rotational motion to the specified hollow shaft, which is connected to the piston by means of a slot, due to which the rotational motion is transmitted to the specified screw. The electric motor is attached to the end of the hollow shaft.

In the description of the invention to US patent No. 6108587, issued in the name of Shearer (Shearer) and others, discloses a system for injection molding, which includes a corresponding electric motor that drives the screw into rotational motion transmitted to it through a gear transmission, as well as the corresponding hydraulic cylinder, the piston of which provides translational movement of the screw.

In the description of the invention to US patent No. 6478572, issued in the name of Shad (Schad) and others, an injection unit is disclosed which provides for the use of a single electric motor that communicates rotational movement of the screw of the extruder and also provides charging of the hydraulic pressure accumulator. The charge accumulated in this pressure accumulator is used to ensure proper movement of the screw of the extruder.

US Pat. No. 6,499,989 discloses a device for removing discs from a mold. In the various embodiments of this invention described herein, the use of a hollow electric motor that imparts rotational motion to the mold ejector shaft, as well as a corresponding linear electric motor that provides linear movement of said shaft, is contemplated. In this case, the hollow electric motor drives the shaft in rotational motion using an appropriate gearbox, which provides the ability to control the shaft rotation speed. As an alternative technical solution in the description of the invention to this patent indicates the possibility of using the corresponding pneumatic or hydraulic cylinder for linear movement of the shaft. In the embodiments of the invention described herein, it is contemplated to position the corresponding actuator providing linear movement outside the rotational actuator. For this reason, the design of such a unit is more cumbersome, and its economic efficiency is markedly reduced.

In the description of the invention to US patent No. 6517336, issued in the name of Emoto (Emoto) and others, as well as in the description of the invention to European patent No. 0967064 A1, issued in the name of Emoto (Emoto), an injection molding system having a hollow electric motor is disclosed, which communicates rotational movement to the screw shaft and at the same time provides translational movement of this shaft due to its connection with the corresponding unit, which includes a screw with a ball nut and a splined part of the shaft. Using a separate metering electric motor, the screw is rotated in order to ensure that the screw is loaded with synthetic resin. This rotational movement is carried out using an appropriate drive device having a belt and pulleys, and which is able to rotate the screw regardless of the rotor of the hollow electric motor. The rotor of the hollow electric motor is attached to the spline part of the screw shaft, thereby providing rotation of the specified spline part, which, in turn, rotates the screw with a ball nut, which ensures the movement of the shaft in the longitudinal direction.

In the description of the invention to US patent No. 6530774, issued in the name of Emoto (Emoto), an injection molding system is disclosed, comprising the use of an electric motor and a corresponding gear block for driving the screw into rotational motion, as well as the presence of a linear electric motor with a hollow shaft, providing translational movement of the screw in the longitudinal direction, which occurs due to the transmission of motion through the splined part of this shaft to that part where the screw with a ball nut is located.

U.S. Patent Application No. 2002/0168445 A1, filed by Emoto et al., Discloses an injection system that also includes a metering motor and a corresponding hollow shaft motor designed to accordingly communicate the rotary screw movement and ensure the movement of the screw in the longitudinal direction.

In the description of the invention to the application for European patent application No. 1162053, filed by Krauss-Maffei (Krauss-Maffei) and published 12.12.2001, a system consisting of two electric motors is disclosed in which one of these electric motors communicates rotational motion to the auger shaft, while the other electric motor provides translational movement of the screw shaft. In order for these electric motors to be able to operate separately or, together with each other, the use of appropriate switching devices made in the form of couplings is provided.

In the description of the invention to Japanese patent No. 61266218, issued in the name of Sumitomo (Sumitomo) and published 11/25/1986, an injection system consisting of two electric motors, which provides for the use of hollow electric motors, a ball drive mechanism and splined shafts, is disclosed.

German patent DE 10135443 relates to an injection unit for a plastic injection molding machine in which a plasticizing screw with a rotary drive and an electric motor with a stationary component mounted on the frame and an output component providing linear axial movement of the screw for injecting the plastic melt into form. In known injection units of this type, the exhaust component of the electric motor is located in the power transmission between the drive component and the screw. The electric motor can be linear or rotor type, and in the latter case, in the latter case, the rotational movement is converted into translational motion of the output component in the side chain and / or at the end. In both cases, the force that can be applied to the output component is limited.

PCT Patent Application WO 03.046388 A1 discloses a drive mechanism (1) having a housing (1a) in which a drive shaft (2) is installed, made with through drilling (7), which, as a result of drilling, acts as a drive cylinder (3), at least , one piston with a piston axis (5) extending axially in said through drilling, said at least one piston and said one piston axis being rotatable together with said drive shaft. In relation to the solutions known in the prior art, the purpose of this invention is to propose an improved drive mechanism, which, as indicated in the introduction, eliminates the described disadvantages and which allows you to establish an accurate and stable position of the axis of the piston in the axial direction. The technical solution achieved by this object lies in the fact that the drive mechanism in accordance with the invention is characterized in that said at least one piston and said piston axis are capable of reciprocating movement inside said drilling, driving said cylinder . This makes it possible to precisely position the axis of the piston with respect to the drive shaft, allowing precise drive action in various operating conditions.

Despite the fact that the above links reveal a wide variety of combinations of various electrical and hydraulic systems that power the screw of an injection molding machine, nevertheless, these links do not cover any such system that combines unique the advantages provided by the hollow motor in terms of more accurate installation of the screw in a predetermined position when adjusting it, as well as a hydraulic injection unit, which allows to obtain high and zhektsionnuyu ability. The present invention aims to create a compact injection unit, which has unique advantages provided by the presence of both electric and hydraulic drive systems.

Disclosure of invention

The present invention is a drive unit for use in an injection molding machine having a shaft, said unit comprising:

a cylinder having an inner surface and an outer surface for receiving a fluid under pressure, wherein the cylinder is rotatably mounted and is located along the axis;

the piston mounted on the shaft of the injection molding machine, the piston having a head, is in contact with sliding with the inner surface of the cylinder, mounted rotatably, and is located along the axis, and the shaft is configured to move longitudinally under the action of fluid pressure through the cylinder to piston head; and

a hollow shaft electric motor having:

case with a wall;

a stator mounted on the wall of the housing; and

a rotor connected to the outer surface of the cylinder, and the rotor, which is mounted rotatably and is located along the axis, is designed to rotate the piston and rotate the shaft of the injection molding machine.

In a preferred embodiment of the present invention, the proposed hydraulic unit is located at least partially inside the hollow electric motor, thereby providing a more compact unit having smaller dimensions.

Brief Description of the Drawings

Figure 1 is a sketch of a cross section of a base drive unit made in accordance with the present invention.

FIG. 2 is a cross-sectional side view of a preferred embodiment of a drive unit for use in an injection molding machine, where the drive unit is shown in an extended position.

Fig. 2A is a cross-sectional view of the piston head used in the construction of the drive unit shown in Fig. 2.

FIG. 2B is a partial cross-sectional view illustrating a channel for supplying hydraulic fluid to the piston of the drive unit shown in FIG.

Fig. 2C is a cross-sectional view for some part of the piston and spline insert.

Fig.2D is a view in cross section of a gear belt and encoder.

Figure 3 is a cross-sectional side view of a preferred embodiment of a drive unit for use in an injection molding machine, where the drive unit is shown in a retracted position.

Figure 4 is a perspective view of the piston and spline insert in a preferred embodiment of the drive unit.

5 is a cross-sectional sketch of another embodiment of the present invention.

6A and 6B are cross-sectional views of another embodiment of the present invention in which a drive cylinder surrounds a hollow motor.

7 is a cross-sectional view of another embodiment of the present invention.

FIG. 7A is a sectional view taken along section line 7A-7A of the embodiment of the present invention shown in FIG. 7.

The implementation of the invention

1, the present invention is illustrated in a simple embodiment. As shown in FIG. 1, the hollow shaft motor 45 has a housing 61, a stator 46 and a rotor 47. The stator 46, as shown in the drawing, is mounted on the wall of the housing 61. The rotor 47 is rigidly mounted on the cylinder 48. The specified cylinder 48 has a spline portion 49, made on its inner surface. It is also possible to use a corresponding insert worn on the cylinder 48 and replacing the splined part 49. The specified splined part 49 is engaged with the splines 62 (only one such slot is shown in the drawing) made on the piston 50. The corresponding shaft (not shown) made in one piece with the piston 50 or attached to this piston, it is rotationally driven by a hollow shaft electric motor 45 due to the presence of a corresponding relationship between the rotor 47 and the piston 50.

The shaft attached to the piston 50 moves in the longitudinal direction under the influence of fluid pressure on either side of the piston head 50, to which this fluid, under pressure, is supplied through holes 51 and 52 made in the wall of the cylinder 48. In those cases when the proposed drive unit is intended to be used in the construction of an injection molding machine, the corresponding liquid for hydraulic mechanisms or a graphite solution based on water can be used as such a liquid. The piston 50 moves with sliding inside the spline part 49 and rotates in peculiar bearings, which are the corresponding wear-resistant rings 53a together with hydraulic seals 53b. The entire assembly, consisting of a rotor 47, a cylinder 48 and a piston 50, is installed with the possibility for it to rotate in bearings 63 and 64, which also provide a fixed axial location of this assembly.

Despite the fact that FIG. 1 is just an elementary sketch illustrating the present invention, those skilled in the art will be able to make any minor changes to it that may be necessary when designing an acceptable drive assembly in accordance with the present invention. For example, instead of a splined shaft, some other device may be provided that allows the shaft to move with sliding in the longitudinal direction while maintaining this shaft the ability to rotate. As such a device, in particular, a single key sliding along the corresponding key groove could be used.

Further, in the following description, the proposed drive unit will be considered in relation to a plasticizing screw intended for installation in an injection molding machine. The present invention is suitable, in particular, for use in such a system where there is a need to provide rotational movement of the screw in order to melt the injection material, as well as to move the screw in the longitudinal direction with significant driving force in order to inject this material under pressure inside the corresponding mold.

As shown in figures 2 and 3, the screw 1 is inserted into the inside of the part 2 having a cylindrical shape, and can perform a rotational movement, as well as move inside it in the axial direction. Injection material, for example, such as plastic granules, is supplied to the screw 1 through the opening 4. A cylindrical part 2 is mounted in the housing 3 of the injection unit and held there in place by means of a retaining plate 5 for the specified part. The groove 6 is designed to introduce the corresponding tool into it, which holds the screw 1 in place, while the piston 23 is rotated so that by unscrewing the piston 23, disconnect it from the screw 1 at the place where their threaded connection 29 is located. Piston stop 7 is intended to prevent possible rotation of the specified tool when the piston 23 is removed from the screw 1, and determines the fully extended position of the piston 23. The considered design allows the removal of the screw 1 and its replacement in case of occurrence This is a necessity.

The front of the piston 23 is in contact with the cylindrical wall 18, while resting on the piston rings 45a. The piston 23 moves axially along the cylinder wall 18 as the screw 1 moves forward and backward. In this case, the grooves of the slots 17 allow slipping inside the spline insert 15, thereby allowing the piston 23 to be moved in the longitudinal direction.

The hollow motor 30 provides rotational movement of the piston 23, and with it the screw 1, which is attached to the piston 23. The junction box 8 provides power to the hollow motor 30 through the current supply channel 9. Under the influence of the current passed through the stator 12, the rotor 16 rotates. Preferably, the hollow motor 30 has a rotor with permanent magnets; however, any other hollow motor may be used to rotate the piston 23 and the screw 1. The rotor 16 is attached to the wall 18 of the cylinder by means of a hot-press fit. It is also possible to use any other method for mounting the rotor 16 to the cylinder wall 18, since the rotor 16 and the cylinder wall 18 move as a single unit. The slotted insert 15 is connected to the cylinder wall 18 by means of bolts 44. The slotted insert 15 is engaged with the grooves of the slots 17 (best seen in FIG. 4) made on the outer wall of the piston 23. Thus, when the rotor 16 rotates, the wall 18 the cylinder and piston 23 also rotate, so that no relative rotational movement between the cylinder wall 18 and the piston 23 occurs.

The presence of cooling channels 10 provided in the housing 11 of the electric motor and providing the possibility of cooling the hollow electric motor 30 is envisaged.

In the piston head 24, mounted on the rear end of the piston 23 with bolts 31, a plurality of holes 37 are made (see FIGS. 2A and 4), serving as channels connecting the cavities 32 and 33 to each other. This design allows for a minimum piston thickness 23. The piston head 24 is provided with piston rings 45a on which it rotates and slides along the cylindrical wall 22. A hydraulic fluid, for example, such as hydraulic fluid, is supplied to the cavities 32 and 33 through channel 25 for hydraulic fluid, made in the rear part 26 of the housing, while pushing the piston 23 and the screw 1 forward, due to which the material is injected into the mold.

The piston 23 and the screw 1 extend back under the influence of material accumulating in the head of the screw 1, and this fact is well known to specialists in this field of technology. In order to avoid the formation of voids in the molten material, it is proposed in the cavity 32 to create a relatively low pressure acting on the piston 23 from the side where the cylinder bore is located. In addition, it is also envisaged the presence of grooves 38 (see FIG. 2C) made in the spline insert 15 and designed to provide hydraulic communication between the cavities 34 and 35.

The cylindrical wall 18 is based on the rings 13 and 14 of the roller bearings, which facilitates the rotational movement of this node and ensures minimal friction loss. The roller bearing ring 13 rests on the end piece 41, and the roller bearing ring 14 rests on the ring 89.

Using the pins 27, the motor housing 11 is connected to the end part 41 of the cylinder ring 36. The pins 27 exclude any possibility for the end part 41 and the cylinder ring 36 to make any rotational movement relative to the stator 12, which could occur under the influence of rotational pressures arising from the rotation of the rotor 16 and the piston 23.

Using the pins 28, the rear part 26 of the housing is connected to the cylindrical wall 22, excluding any possibility for the cylindrical wall 22 to make any rotational movement when the piston head 24 is rotated.

The joints of the cylindrical wall 22 with the ring 36 of the cylinder and with the rear part 26 of the housing are sealed with appropriate seals. Since these seals are only exposed to radial stress, leakage through them or their rupture becomes less likely for them compared to seals that are exposed to both radial and axial stresses.

It is envisaged the presence of connecting rods 19 extending from the rear part 26 of the housing to the retaining plate 5 holding the cylindrical part, and to the injection housing 3, which fasten the drive unit in a single unit.

In addition, it also provides for the Temposonic rod 20 (trademark), which is attached to the rear portion 26 of the housing and passes through the corresponding hole made in the piston head 24. The magnetic assembly 21 mounted on the piston head 24 accordingly responds to the translational movement of the piston head 24, sending a signal passing through the Tempo sonic rod 20, and thereby indicating the location of the piston head 24 and, therefore, the screw 1 in a manner that will be understood specialists in the field of injection molding.

The speed of rotation and the position of the screw 1 are determined using a toothed belt 39 and an encoder 40 in a way that will be understood by experts in the field of providing control of various mechanisms using a servomotor.

During operation, an increased pressure is created in the cavity 32 due to the injection of fluid into the cavity through the hole 25. Under the influence of this pressure, the piston 23 and the screw 1 are forced to move forward. When this is the injection of plastic in front of the screw 1, into the cavity of the mold. Upon completion of the injection, a reduced pressure is briefly maintained in the cavity 32. As a result, there is a decrease in pressure in the cavity 32 and an increase in pressure in the cavity 33, as a result of which the piston 23 is retracted back a small distance. At the same time, the hollow electric motor continues to rotate all the time, thereby communicating rotational motion to the piston 23 and the screw 1, as a result of which the plastic granules supplied to the screw through the opening 4 melt. Throughout this time interval, it may be necessary to maintain a relatively low pressure in cavity 32 in order to avoid voids and the formation of bubbles inside the molten plastic. The hollow motor 30 stops its rotation only when the screw 1 moves back to its predetermined position. The screw 1 can be additionally retracted a little further so that the pressure exerted by it on the molten plastic is reduced. As soon as the screw 1 is completely retracted, the next injection cycle begins immediately, while the entire injection process is repeated again, and the molten plastic is again fed into the cavity of the mold.

Figure 5 illustrates schematically another embodiment of the present invention. In this embodiment, the rotor 54 is rigidly attached to the piston 55 and has a width equal to the sum of the stroke length of the piston 55 and the width of the stator 56. The piston head 57 reciprocates within the cylinder 58.

Cylinder 58 is shown with a single fluid inlet port 159. A second inlet may also be provided; however, in some cases, the practical use of such a second inlet pipe may not be required. For example, in the case of a plasticizing screw intended for use in an injection molding machine, with a corresponding accumulation of injection plastic material in the area of the end part of the screw, quite significant pressure can be created, which acts on the screw and tends to move the piston back to its position in which it is made injection.

This embodiment of the present invention has corresponding advantages in that the entire motor as a whole is always outside the hydraulic part of the drive, and also that there is no need for a spline shaft connection, since the piston 55 provides freedom of rotational movement and translational motion in bearings 59 and 60.

The embodiment of the present invention shown in FIG. 5 can be further modified so that the stator 56 becomes longer and the rotor 54 is shorter. In this case, such a drive unit would work in exactly the same way as the version of its design considered above, but due to the decrease in the size of the rotor 54, the weight of the piston 55 would decrease and the prime cost of the electric motor would decrease.

In the embodiment of the present invention shown in FIGS. 6A and 6B, the cylinder of the drive unit of the invention encompasses a hollow electric motor. The fixed housing 70 of this cylinder is supported by a non-rotating piston 71 and mounted on it by bearings 72 and 73. These bearings 72 and 73 allow the non-rotating piston 71 to be moved in the longitudinal direction. The fixed housing 70 and the non-rotating piston 71 together form a piston chamber 74. The toroidal end surface 75 extends from the non-rotating piston 71 and is a guide surface that allows the entire assembly to move in the longitudinal direction. On the toroidal surface 75 of the piston are the piston rings 88.

The stator 76 of the hollow motor is attached to the inner surface of the non-rotating piston 71, providing during operation a corresponding relationship of this piston with the rotor 77 of the electric motor. In this case, the rotor 77 itself is attached to the shaft 78.

In this embodiment of the present invention, the rotor of the hollow electric motor is rotated, thereby imparting rotational motion to the shaft 78 as well. The shaft 78 is supported by bearings 79 and rotated therein.

Under the influence of fluid pressure on either side of the toroidal surface 75 of the piston, this entire assembly moves, consisting of a non-rotating piston 71, a stator 76, a rotor 77 and a shaft 78 in the longitudinal direction.

6A, the shaft 78 is shown in its retracted position. 6B, this shaft 78 is shown in its extended position.

An advantage of the design, which is shown in FIGS. 6A and 6B, is that the proposed assembly will in this case have a shorter length, but it will be necessary to provide the possibility of moving in the longitudinal direction for the correspondingly larger part of this assembly. In addition, in this embodiment, the invention also eliminates the need for a splined shaft or some other similar device.

FIGS. 7 and 7A show such a modification of the considered embodiment shown in FIG. 6A and 6B, in which instead of a single toroidal piston, two separate pistons are provided. In such an embodiment of the present invention, the pistons are fixedly mounted, and the cylinder itself performs translational movement.

As shown in Fig.7, the shaft 80 is supported by bearings 81 and 82 and rotates in them. The stator 83 is rigidly attached to the housing 84. Inside the housing 84 there are also pistons 85 and 86 located respectively in the cylinders 187 and 188. In this case, the corresponding hydraulic connections (not shown) with the cylinders 187 and 188 are provided, under the influence of which the corresponding movement of the pistons is ensured 85 and 86 in a manner that is well understood by those skilled in the art. The rotor 87 of the hollow motor is rigidly attached to the shaft 80.

During operation, when current is supplied to the stator 83, the rotor 87 rotates, resulting in the rotational movement of the shaft 80. When the working fluid under pressure is supplied to the pistons 85 and 86, the housing 85 is forced to move in the longitudinal direction. With this movement of the housing 84 occurring in the longitudinal direction, there is also a forced movement of the stator 83, the rotor 87 and the shaft 80 in the longitudinal direction.

The embodiment of the present invention, shown in Fig. 7, is compact enough and does not require the use of a single, but relatively large toroidal cylinder or a corresponding spindle drive. However, in this embodiment of this design, it will also be necessary to ensure the possibility of moving in the longitudinal direction as a whole for the entire assembly of the housing assembly, which also includes a hollow electric motor and cylinders.

The choice of an appropriate embodiment of the present invention will in each case be determined on the basis of those requirements to be met in this particular application. For example, if there are any restrictions on the length, then it will be possible to opt for such an embodiment of the present invention, which is shown in FIGS. 6A and 6B, or in FIG. 7, whereas in those cases when the basic requirement is providing the smallest possible weight of the shaft, the best results can be obtained by using completely different embodiments of the present invention.

Specialists in the art should understand that the present invention is not limited solely to those examples of its practical implementation, which are discussed in the above description of the invention in order to illustrate the best embodiments of the present invention, which may be made various changes and additions regarding shape, dimensional characteristics and relative positioning of individual parts of the structure, as well as various details determining un action of the device. It is assumed that the present invention covers all such changes and additions, provided that they do not go beyond the essence and scope of the invention defined by the attached claims.

Claims (12)

1. A drive unit for use in an injection molding machine having a shaft, said unit comprising a cylinder (48) having an inner surface and an outer surface, for receiving a pressurized fluid, the cylinder (48) being installed with the possibility rotation and is located along the axis,
a piston (50) mounted on the shaft of the injection molding machine, the piston (50) having a head, is in contact with sliding with the inner surface of the cylinder (48) and mounted rotatably and is located along the axis, and the shaft is made to move longitudinally under the influence of fluid pressure through the cylinder (48) to the piston head (50), and
an electric motor (45) with a hollow shaft having a housing (61) with a wall,
a stator (46) mounted on the wall of the housing (61), and
a rotor (47) connected to the outer surface of the cylinder (48), and the rotor (47), which is mounted rotatably and is located along the axis, is designed to rotate the piston (50) and rotate the shaft of the injection molding machine. 2. The drive unit according to claim 1, characterized in that the cylinder (48) has a spline section (49) made on the inner surface of the cylinder (48), and the piston (50) has splines (62) engaged with the spline section (49) cylinder (48). 3. The drive unit according to claim 2, characterized in that said cylinder (48) surrounds said electric motor (45) with a hollow shaft. 4. The drive unit according to claim 1, characterized in that said rotor (47) has a length that is greater than said stator (46). 5. The drive unit according to claim 2, characterized in that said rotor (47) has a length that is greater than said stator (46). 6. The drive unit according to claim 4, characterized in that said rotor (47) has a length equal to the sum of the width of said stator and piston stroke (50) in said cylinder (48). 7. The drive unit according to claim 5, characterized in that said rotor (47) has a length equal to the sum of the width of said stator and piston stroke (50) in said cylinder (48). 8. The drive unit of claim 1, characterized in that the said stator (46) has a width that is greater than the specified rotor (47). 9. The drive unit according to claim 2, characterized in that said stator (46) has a width that is larger than said rotor (47). 10. The drive unit according to any one of claims 1 and 2, 4-9, characterized in that said cylinder (48) rotates in bearings mounted in the motor housing (61). 11. The drive unit according to claim 10, characterized in that said cylinder (48), said piston (50) and said rotor (47) rotate as a single unit. 12. A drive unit according to any one of claims 1 and 2, 4-7, characterized in that said cylinder (48) is at least partially located within the limits of said hollow shaft electric motor (45).

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