Injection unit and method for measuring the displacement of a piston in a cylinder

Abstract

Injection unit, comprising a) a cylinder housing (120) comprising an inner cylindrical surface (124) and extending along a cylinder axis (121); b) a piston (122) arranged in the cylinder housing (120) and movable along the cylinder axis (121) between an extended and a retracted position, and having a piston radial surface (141) opposite the inner cylindrical surface (124), the piston radial surface (141) having a measurement detection device (178); c) a probe (180) fixed relative to the cylinder housing (120) and communicating with the measurement sensing device (178) when the piston (122) moves between the extended and retracted positions to detect the displacement of the piston (122); and d) wherein the measurement detection device (178) has a plurality of annular piston teeth (182) which are concentric with the cylinder axis (121) and axially spaced along the piston radial surface (141); e) the probe (180) comprises a gear (184) having teeth (188) extending radially inward of the inner cylindrical surface (124) and meshing with the annular piston teeth (182), wherein displacement of the piston (122) results in rotation of the gear (184).

Description

AREA

[0001] The application relates to injection units, such as for injection molding machines, as well as devices and methods for measuring the position of a piston of the injection unit. INTRODUCTION

[0002] The following is no agreement that anything discussed below represents prior art or common knowledge among those skilled in the art.

[0003] US 6,484,420 B1 describes a hydraulic actuator comprising a cylinder with a piston moved by a hydraulic fluid. A light guide at one end of the cylinder directs a laser beam into and out of the cylinder, where the beam is reflected. This beam then exits the cylinder through a second light guide. A control unit measures the propagation time of the light beam and calculates the piston position.

[0004] US 7 291 297 B2 describes and deals with the fact that in the environment of a reciprocating injection unit (RS), as in Fig. 1, a regulator of the injection unit is arranged to continuously circulate the screw during the conventional plasticizing operation as well as shot injection. In this way, the RS unit is more efficient, consumes less energy, and produces a higher resin output. The injection unit includes a check valve near a nozzle; the check valve is either designed to rotate with the screw to reduce wear or is a spherical check valve. In the field of injection molding, the orbiting screw includes flights that allow resin granules to melt and mix in spaces between adjacent flights. However, the flights are substantially arranged to prevent excessive displacement of resin around the flights.A screw position transducer or similar, typically of the Temposonic type, is preferably mounted on a housing to measure the longitudinal position of the feed screw relative to the cylinder. Since the feed screw is connected to the end of the injection piston, the position sensor also measures the position of the injection piston relative to the housing.

[0005] DE 42 37 360 C1 describes a cylinder-piston unit for a plastic injection molding machine. For melting plastic granules, the plastic injection molding machine has a conveyor screw partially surrounded by a plasticizing cylinder, which can be moved axially to press the molten plastic into a mold. The conveyor screw is connected to a piston rod, which, at its end facing away from the conveyor screw, has a piston arranged in a pressure chamber formed by a cylinder. The piston can be pressurized at both its ends to move the piston rod axially. The cylinder or pressure chamber is closed by a cover into which a sensor for generating and measuring magnetic fields is embedded.To detect the axial position of the piston rod, the piston rod has several annular grooves between the conveyor screw and the piston, which are alternately filled with a magnetic and a non-magnetic material. An axial movement of the piston rod leads to a translational displacement of the annular grooves relative to the sensor, which allows the sensor to determine piston rod movement by measuring magnetic field fluctuations.

[0006] DE 21 48 917 A describes a control system for plasticizing in injection molding machines. The injection molding machine comprises a screw, partially surrounded by a cylinder sleeve, for melting and injecting plastic into a mold. At its end facing away from the mold, the screw has a piston head arranged in a cylinder. The piston head can be subjected to pressure on both of its end faces within the cylinder in order to move the piston head, and thus the screw, axially translationally to inject the plastic into the mold. Between the cylinder and its end facing the mold, the screw has grooves and edges running circumferentially around the screw, which mesh with a gear, causing the gear to rotate upon axial movement of the screw. By evaluating the rotation of the gear, the axial position of the screw can be measured.

[0007] An injection unit according to the invention and a method for measuring the displacement of a piston in a cylinder are specified in the independent claims. Advantageous embodiments and further developments emerge from the dependent claims.

[0008] The following summary is intended to enable the reader to understand the detailed discussion. The summary is not intended to limit or define the claims.

[0009] According to one aspect of the invention, an injection unit comprises: a cylinder housing comprising an inner cylindrical surface extending along a cylinder axis; a piston arranged in the cylinder housing and displaceable along the cylinder axis between an extended and a retracted position, and comprising a radial piston surface facing the inner cylindrical surface; the radial surface of the piston comprising a direction; a probe fixed relative to the cylinder housing and communicating with the measurement sensing device when the piston moves between the extended and retracted positions to measure the displacement of the piston. The measurement sensing device has a plurality of annular piston teeth concentric with the cylinder axis and axially spaced along the piston radial surface.The probe comprises a gear having teeth extending radially inward of the inner cylindrical surface and meshing with the annular piston teeth, wherein displacement of the piston results in rotation of the gear.

[0010] In some examples, the injection unit may include a pressure chamber extending radially between the inner surface. The pressure chamber may contain a fluid to displace the piston into the extended or retracted position when pressurized. The teeth of the gear may extend into the pressure chamber. In some examples, the probe may extend through the cylinder housing. In other examples, the cylinder housing may have an outer surface radially outward of the inner cylindrical surface and a cavity between the two having opposite open ends at the inner cylindrical surface and the outer cylindrical surface, and at least a portion of the probe may be received by the cavity.

[0011] The probe may comprise a shaft which is driven radially by the gear and which is connected to a sensor for detecting the rotation of the shaft.

[0012] In some examples, the injection unit may further include a rotary drive connected to the piston for selectively rotating the piston about the cylinder axis as the piston translates within the cylinder housing. The piston may be driven relative to the cylinder housing by the rotary drive.

[0013] According to some aspects, an injection unit comprises: a cylinder housing including an inner cylindrical surface extending along a cylinder axis; a piston received in the cylinder housing and displaceable along the cylinder axis between an extended and a retracted position; the piston radial surface includes a measurement sensing device; a pressure chamber extends radially between the inner cylindrical surface and the piston radial surface; the pressure chamber communicates with a source of pressurized fluid for urging the piston to one of the extended and retracted positions; and a probe extends through the cylinder housing and is in conductive communication with the measurement sensing device for measuring displacement of the piston as it moves between the extended and retracted positions.The measurement sensing device further comprises a plurality of annular piston teeth concentric with the cylinder axis and extending axially at intervals along the piston's radial surface. The probe further comprises a gear comprising teeth extending into the pressure chamber and meshing with cylindrical piston teeth, with displacement of the piston causing the gear to rotate.

[0014] In some embodiments, the injection unit further comprises a shot cavity for holding an injection compound. Moving the piston to the retracted position may be accompanied by filling the shot cavity with the injection compound, and moving it to the extended position may be accompanied by injecting the injection compound from the shot cavity into the mold. The pressure chamber, when pressurized, may push the piston into the retracted position.

[0015] In some embodiments, the cylinder housing may have an outer surface radially spaced from the inner cylindrical surface with a cavity therebetween having opposite open ends at the inner cylindrical surface and the outer surface, at least a portion of the probe being received in the cavity.

[0016] The probe may comprise a shaft rotated by the gear, the shaft being coupled to a sensor for detecting the rotation of the shaft.

[0017] According to some aspects, an injection unit comprises: a cylinder housing having an inner cylindrical surface and extending along a cylinder axis; a piston disposed within the cylinder housing and displaceable along the cylinder axis between an extended and a retracted position, the piston having a piston radial surface opposite the inner cylindrical surface; the piston radial surface comprising a measurement sensing device; a pressure chamber extending radially between the inner cylindrical surface and the piston radial surface and communicating with a pressurized fluid source for displacing the piston to one of the extended and retracted positions; and a probe extending through the cylinder housing and communicating with the measurement sensing device for detecting displacement of the piston as it moves between the extended and retracted positions.The measurement detection device comprises an axially tapered portion of the piston's radial surface, wherein the radial distance between the inner cylindrical surface and the piston's radial surface advantageously changes at a specific location along the cylinder axis of the cylinder housing as the piston is displaced. The probe has a distance sensor that detects the distance between the piston's radial surface and the distance sensor. The piston can be rotatable about the cylinder axis while moving axially within the cylindrical housing.

[0018] According to some aspects, an injection unit comprises: a cylinder housing comprising an inner cylindrical surface extending along a cylinder axis; a piston received by the cylinder housing and displaceable along the cylinder axis between an extended and a retracted position, the piston having a piston radial surface opposing the inner cylindrical surface of the piston radial surface, comprising a measurement sensing device, the measurement sensing device comprising a plurality of annular piston teeth concentric with the cylinder axis and axially spaced along the piston radial surface; a pressure chamber extending radially between the inner cylindrical surface and the piston radial surface; the pressure chamber contains a fluid for displacing the piston when pressurized;a probe is fixed relative to the cylinder housing and extends through the pressure chamber, the probe comprising a gear having teeth extending into the pressure chamber and meshing with the annular piston teeth, whereby displacement of the piston causes rotation of the gear to continuously detect the axial position of the piston relative to the cylinder housing as the piston moves between the extended and retracted positions;

[0019] According to some concepts, a method for measuring the position of a piston in a cylinder and / or for detecting the direction of a piston in a cylinder comprises the steps of providing a measurement sensing device on the outer piston radial surface of a piston and positioning a probe along an inner surface of the cylinder traversed by the piston as it moves between the extended and retracted positions, the probe cooperating with the measurement sensing device in a known and predictable manner. The method includes engaging the outer surface of the piston with a gear such that displacement of the piston causes rotation of the gear. The gear includes teeth extending into a pressure chamber. The rotation of the gear can be translated into an axial position of the piston using, for example, an encoder. DRAWINGS

[0020] Reference is made to the detailed description of the attached drawings: Fig. 1 is a perspective view of an injection molding machine. Fig. 2 is a sectional view along the line 2 - 2 in Fig. 1. Fig. 3 is a sectional view along the line 3 - 3 in Fig. 1. Fig. 4 is a perspective view of a probe part of the structure according to Fig. 2. Fig. 4A is a sectional view taken along line 4A - 4A in Fig. 4; and Fig. 5 is a sectional view of a portion of another embodiment of an injection molding machine; the sectional view corresponds generally to that of the embodiment of Fig. 2. Fig. 6 is a sectional view of a portion of another embodiment of an injection molding machine; the view corresponds generally to the view according to Fig. 3; and Fig. Figure 7 is a perspective view of a probe part of the structure according to Fig. 6. INDIVIDUAL DESCRIPTION

[0021] Various devices or methods are described below to provide an example of an embodiment of each claim.

[0022] With reference to Fig. 1, one embodiment of an injection molding machine 100 includes a base 102 with a moving platen 104 and a stationary platen 106 mounted to the base 102 and connected to tie rods 108. A mold is formed between the platens 104 and 106. It is at least partially defined by a first mold half mounted to the moving platen 104 and a second mold half mounted to the stationary platen 106. In the illustrated embodiment, the injection molding machine 100 is of the two-platen variety. In other embodiments, the injection molding machine 100 may include more than two platens.

[0023] An injection unit 110 is mounted on the base 102 to inject resin or other injection material into the mold to form a molded part. The injection unit 110 includes a housing 112, a drum 114 extending from the housing 112 to the plates 104, 106. An injection screw 116 ( Fig. 2) is received by the drum 114, and a nozzle 117 is disposed at a front end of the drum 114. Housing 112 may be mounted on a movable carriage 118 to move the drum 114 toward or away from the plates 104, 106.

[0024] It will be Fig. 2. The injection unit 110 includes a cylinder housing 120 for slidably guiding a piston 122. The cylinder housing 120 extends along a cylinder axis 121. The housing 112 in the illustrated embodiment has a first (front) portion 112a near the barrel 114, and a second (rear) portion 112b remote from the barrel 114. The cylinder housing 120 may include an inner cylindrical surface 124 generally disposed between the front portion 112a and the rear portion 112b. The cylinder housing 120 may be integral with the housing 112. In the illustrated embodiment, the inner cylindrical surface 124 of the cylinder housing 120 comprises an inner surface of the housing 112. The cylindrical surface 124 has a first partial surface 124a with a first bore diameter and a second partial surface 124b with a second bore diameter.In the illustrated embodiment, the first bore diameter is larger than the second bore diameter.

[0025] Piston 122, in the illustrated embodiment, is connected to the injection screw 116 at a first (front) end. Moving and rotating the piston 122, in the illustrated embodiment, results in a corresponding moving and rotating the injection screw 116. Piston 122, in the illustrated embodiment, includes a piston head 128 having axial and second surfaces 130, 132, with the first surface 130 being located rearward of the second surface 132. At least a portion of a radially outer surface extends between the first and second surfaces 130, 132 and defines a first seal bearing 134. The first seal bearing 134 generally divides an interior volume of the cylinder housing 120 into a first pressure chamber 136 (on the rear side of the first surface of the piston head 128) and a second pressure chamber 138 (on the second front surface of the piston head 128).

[0026] Piston 122 further includes a substantially cylindrical piston body 140 (having a radially outer surface 141) extending axially from the second surface 132 of the piston head 128 away from the first surface 130. The cylindrical piston body 140 is coaxial with and has a smaller diameter of the first seal bearing 134 such that the second (front) surface 132 of the piston head 128 has an annular surface extending radially between the outer radial surface 141 of the piston body 140 and the outer diameter of the first seal bearing 134. A second seal bearing 142 is proximate a front end of the piston body 140 from the first seal bearing 134.

[0027] The first pressure chamber 136 extends axially between the first (rear) surface 130 of the seal bearing 134 and an end cap 150 mounted near the rear portion 112b of the housing 112. In the illustrated embodiment, the end cap 150 rotatably supports a splined shaft 152 that projects toward the front portion 112a of the housing 112. The splined shaft 152 is driven by a rotary drive 154, which in the illustrated embodiment comprises a hydraulic motor. The splined shaft 152 has an outer surface with splines 156 that extend parallel to the cylinder axis 121. The first pressure chamber 136 extends radially generally between the outer surface of the splined shaft 152 and the first partial surface 124a of the first portion of the cylinder housing 120.

[0028] In the illustrated embodiment, the second pressure chamber 138 extends axially between the second surface 132 of the first seal bearing 134 and a front wall 158 near the second seal bearing 142. The second pressure chamber 138 extends radially between the radial surface 141 of the piston body 140 and the second partial surface 124b of the cylinder housing 120. This second partial surface 124b cooperates with the second seal bearing 142 when the piston 122 moves between the extended and retracted positions.

[0029] The annular second surface 132 and the front wall 158 of the second pressure chamber 138, which are axially opposed in the illustrated embodiment, are each fixed relative to the piston body 140. The effective surface area of ​​the second surface 132 is larger than the effective area of ​​the front wall 158, so that when the second pressure chamber 138 is pressurized with fluid, a net force is applied toward the retracted position (against the cylinder cap 150). In the illustrated embodiment, the second surface 132 and the front wall 158 have a common radially inner extent, defined by the outer surface 141 of the piston body 140.The second surface 132 has a radially outward extent substantially equal to the first bore diameter, and the front wall 158 has a radially outward extent substantially equal to the second bore diameter, and the first bore diameter is greater than the second bore diameter.

[0030] Piston body 140 is further provided with an internal cavity 160 having an axial opening 162 at the rearward end of the piston body for receiving the splined shaft. The cavity 160 has an axial extent substantially long enough to accommodate the length of the splined shaft 152 when the piston moves from the extended to the retracted position. A groove 164 may be provided on the inner radial surface of the opening at the rearward end of the piston cavity. Groove 164 may be provided separately on the piston body 140 or form an integral one-piece construction with the piston body 140. Groove 164 may have a female spline profile that cooperates with the grooves 156 of the splined shaft 152 in an axially sliding but non-rotatable engagement. The groove need not prevent axial fluid flow through the groove.For example, fluid can flow axially from one side of the groove 156 to the other, working its way between the inner and outer spline profiles. Additionally, or in addition, axial flow channels can be provided in the groove 164 to facilitate fluid flow through the groove. Operating in a fluid-filled environment can facilitate smooth and sustained operation of the groove and splined shaft 152.

[0031] Fluid communication with the first and second pressure chambers 136, 138 can be provided with suitable fluid inlets and channels. In the illustrated embodiment, a first fluid port 170 extends through the housing 112 and provides fluid communication with the first pressure chamber 136 via a radial channel 172a near the rear end of the splined shaft 152; an axial channel 172b extends between radial channel 172a and the cavity 160 in the piston body and through the groove 164 separating the cavity 160 from the first pressure chamber 136. In the illustrated embodiment, a second fluid port 176 extends through the housing 112 at a position near the first port 170 (to facilitate closure) and communicates with the second pressure chamber via an axial channel 176a and a radial channel 176b.

[0032] The injection unit 110 may further be equipped with a piston position measuring system for measuring the axial position of the piston relative to the cylinder housing 120 as the piston moves between the extended and retracted positions. For example, accurately guiding the movement of the piston can facilitate reliably and reproducibly delivering the desired volume of mass into the mold during each machine cycle.

[0033] In the illustrated embodiment, the outer piston radial surface 141 includes a measurement sensing device 178. A probe 180 is carried by the cylinder housing 120 and communicates with the measurement sensing device 170 to continuously sense the axial position of the piston 122 as it moves between the extended and retracted positions.

[0034] In the illustrated embodiment, the measurement sensing device 178 includes a plurality of annular piston teeth 182 arranged concentrically with the cylinder axis 121 and axially spaced along the piston radial surface 141. Probe 180 includes a gear 184 rotatable about a gear axis 186 oriented generally perpendicular to the cylinder axis 121. Gear 184 is provided with teeth 188 that mesh with the annular piston teeth 182, such that movement of the piston 122 causes rotation of the gear 184. The teeth 188 remain engaged with the annular piston teeth 182 regardless of the axial position of the piston 122 along its cylinder axis 121. The engagement of the teeth 188 with the annular piston teeth 182 also enables the rotation of the piston 122 about the cylinder axis 121, regardless of whether the piston 122 is moving axially or is stationary.

[0035] It should be on the Fig. 3 and Fig. 4A. Probe 180 may further include a shaft 190 that is fixed to gear 184 and rotated by gear 184. In the illustrated embodiment, shaft 190 is housed within a probe housing 192 and rotatably supported within probe housing 192 by a plurality of bearings 194. Shaft 190 may be connected to a sensor 196 for detecting rotation of shaft 190. Sensor 196 may, for example, comprise an encoder. Process signals from sensor 196 can convert the rotation of gear 184 into an accurate determination of the corresponding displacement of piston 122.

[0036] In the illustrated embodiment, probe 180 is carried by the cylinder housing 120. Further referring to Fig. 3, in the illustrated embodiment, the probe 180 extends through the cylinder housing 120. The cylinder housing 120 has an outer surface 200 that is radially outwardly spaced from the inner cylindrical surface 124; between these two is a cavity 202. The cavity 202 has an inner and an outer end 204; a cavity sidewall 208 extends between the ends 204, 206. At least a portion of the probe 180 is received within the cavity 202. In the illustrated embodiment, a seal 210 surrounds the outer surface of the probe housing 192 and is press-fitted against the cavity sidewall 208 near the outer open end 206.

[0037] In the illustrated embodiment, the probe 180 extends into the second pressure chamber 138, which, when pressurized, forces the piston 122 from the extended to the retracted position. During operation, the maximum pressure in the second pressure chamber 138 is substantially less than the maximum pressure reached in the first pressure chamber 136. Placing the probe 180 in the second pressure chamber 138 can help reduce the risk of oil leakage and / or simplify the sealing arrangement of the probe 180. Meshing the piston teeth 182 with the teeth 188 of the gear 184 in an oil-filled chamber can improve the operation of the probe 180 and reduce wear.

[0038] It should Fig. 5. Parts of another embodiment of an injection unit 510 of an injection molding machine 100 are shown there. The injection unit 510 is similar in some respects to the injection unit 110. Like features are provided with the same reference numerals, numbered up to 400. The injection unit 510 includes a first front portion 512a, a rear portion 512b, a cylinder axis 521, a first partial surface 524a, a second partial surface 524b, a piston head 528, a first pressure chamber 536, a second pressure chamber 538, a piston body 540, a rotary drive 554, and a cavity 560. The injection molding machine 100 further includes a measurement detection device 578 with an axially tapered portion 633 of the piston radial surface 541.In the illustrated embodiment, the piston radial surface 541 tapers (radially inward) from a larger diameter near the second (rear) end of the piston 522 to a smaller diameter near the first (front) end of the piston 522. As the piston 522 moves, the radial distance between the piston radial surface 541 and the inner cylindrical surface 524 changes at a specific location along the axial length of the inner cylindrical surface 524 (portion 524b in the illustrated embodiment). The probe 580 includes a distance sensor 635 supported by the cylinder housing 520. Distance sensor 635 detects the change in distance between the fixed part of distance sensor 635 and the tapered part 633 of piston radial surface 541. Distance sensor 635 can be non-contact (contactless sensor) or a contact device (i.e., a motion transducer).The probe may include wiring that connects the distance sensor 635 to a processing unit. The processing unit may be configured to detect the axial position of the piston 522 within the cylinder housing 520 based on the distance measured by the distance sensor 635. In the illustrated embodiment, the probe 580 is received in and sealed within a cavity of the cylinder housing 520 and extends through the cylinder housing 520.

[0039] In the embodiment according to Fig. 5, the distance sensor 635 of the probe 580 extends through the cylinder housing 520. The wiring of the probe 580 may be located outside the cylinder housing 520. In alternative embodiments, a distance sensor of a probe may be disposed on the inner cylindrical surface of the cylinder housing 520, and the wiring of the probe may extend through the cylinder housing 520.

[0040] It should Fig. 6. Parts of an injection unit 710 of an injection molding machine are shown. The injection machine is similar in some respects to the injection molding machine 100; like components are designated by like reference numerals, numbered incrementally by 600. The injection unit 710 includes a cylinder housing 720 having a piston 722 slidably mounted therein. The injection unit includes a piston position measuring system having a sensor 778 and a probe 780 communicating with the sensor 778 for continuously measuring the axial position of the piston 722 as it moves between the extended and retracted positions.

[0041] In the illustrated embodiment, the measurement sensing device 778 includes a plurality of annular piston teeth 782 concentric with the cylinder axis 721 and axially spaced along the piston radial surface 741. Probe 780 includes a gear 784 rotatable about a gear axis 786 substantially perpendicular to the cylinder axis 721. In the illustrated embodiment, the gear axis 786 is generally vertical (rather than the generally horizontal gear axis 186). Gear 784 has teeth that mesh with the annular piston teeth 782 such that translation of piston 722 results in rotation of gear 784. The teeth of gear 784 remain engaged with the annular piston teeth 782 regardless of the axial position of piston 722 along its cylinder axis 721.The engagement of the teeth with the annular piston teeth 782 also results in a rotation of the piston 722 about the cylinder axis 721, regardless of whether the piston 722 is moving axially or is stationary.

[0042] It should Fig. 7. Probe 780 may further include a shaft 790 fixedly connected to and driven by gear 784. In the illustrated embodiment, shaft 790 is disposed within probe housing 792 and rotatably supported within probe housing 792 by a plurality of bearings 794. Shaft 790 may be connected to a sensor 796 for detecting the rotation of shaft 790. Sensor 796 may, for example, comprise an encoder. The rotation of gear 784 may be converted by process signals from sensor 796 into an accurate determination of the corresponding displacement of piston 722. LIST OF REFERENCE SYMBOLS 100 injection molding machines 102 Foundation 104 moving plate 106 stationary plate 110 Injection unit 112 housings 112a front part 112b rear part 114 Drum 116 Injection screw 117 Nozzle 118 mobile sled 120 cylinder housing 121 Cylinder axis 122 pistons 124 cylindrical surface 124a first partial area 124b second partial area 128 piston head 130 first area 132 second area 134 first seal bearing 136 first pressure chamber 138 second pressure chamber 140 piston body 141 Piston radial area 142 second seal bearing 150 end cap 152 grooved shaft 154 rotary drive 156 groove 158 front wall 160 cavity 162 axial opening 164 groove 170 first fluid opening 172a Radial canal 172b axial channel 176 second fluid opening 176a axial channel 176b Radial canal 178 Measurement recording device 180 probe 182 piston teeth 184 gear 186 Gear axle 188 teeth 190 Wave 192 probe housing 194 warehouses 196 Sensor 200 outer surface 202 Cavity 204 End 206 End 210 Seal 510 injection unit 512a front part 512b rear part 520 cylinder housing 521 cylinder axis 522 pistons 524 cylindrical surface 524a first partial area 524b second partial area 541 Piston radial area 578 Measurement recording device 580 probe 633 tapered part 635 distance sensor 710 injection unit 720 cylinder housing 721 cylinder axis 722 pistons 778 Measurement recording device 780 probe 782 piston teeth 784 gear 786 Gear axle 788 teeth 790 Wave 792 probe housing 794 warehouses 796 Sensor

Claims

[1] Injection unit, comprising a) a cylinder housing (120) comprising an inner cylindrical surface (124) and extending along a cylinder axis (121); b) a piston (122) arranged in the cylinder housing (120) and movable along the cylinder axis (121) between an extended and a retracted position, and having a piston radial surface (141) opposite the inner cylindrical surface (124), the piston radial surface (141) having a measurement detection device (178); c) a probe (180) fixed relative to the cylinder housing (120) and communicating with the measurement sensing device (178) when the piston (122) moves between the extended and retracted positions to detect the displacement of the piston (122); and d) wherein the measurement detection device (178) has a plurality of annular piston teeth (182) which are concentric with the cylinder axis (121) and axially spaced along the piston radial surface (141); e) the probe (180) comprises a gear (184) having teeth (188) extending radially inward of the inner cylindrical surface (124) and meshing with the annular piston teeth (182), wherein displacement of the piston (122) results in rotation of the gear (184). [2] The injection unit of claim 1, further comprising a pressure chamber (136, 138) extending radially between the inner cylindrical surface (124) and the piston radial surface (141). [3] Injection unit according to claim 2, characterized by that the pressure chamber (136, 138) comprises a fluid to displace the piston (122) to the extended or retracted position when pressurized. [4] Injection unit according to claim 2 or 3, wherein the teeth (188) of the gear (184) extend into the pressure chamber (136, 138). [5] Injection unit according to one of claims 1 to 4, wherein the probe (180) extends through the cylinder housing (120). [6] Injection unit according to one of claims 1 to 5, wherein the cylinder housing (120) has an outer surface which is spaced radially outwardly from the inner cylindrical surface (124) and wherein a cavity (202) exists between them, the cavity (202) having opposite open ends (204, 206) on the inner cylindrical surface (124) and the outer surface, respectively, and wherein at least a part of the probe (180) is received within the cavity (202). [7] Injection unit according to one of claims 1 to 6, wherein the probe (180) further comprises a shaft (190) driven by the gear (184) and coupled to a sensor (196) for detecting the rotation of the shaft (190). [8] Injection unit according to one of claims 1 to 7, further comprising a rotary drive (154) connected to the piston (122) for selectively rotating the piston (122) about the cylinder axis (121) as it translates within the cylinder housing (120). [9] Injection unit according to claim 8, wherein the piston (122) is rotated relative to the cylinder housing (120) by the rotary drive (154). [10] Injection unit comprising a) a cylinder housing (120) having an inner cylindrical surface (124) and extending along a cylinder axis (121); b) a piston (122) disposed in the cylinder housing (120) and displaceable along the cylinder axis (121) between an extended and a retracted position, the piston (122) having a piston radial surface (141) opposite the inner cylindrical surface (124); the piston radial surface (141) includes a measurement detection device (178); c) a pressure chamber (136, 138) extending radially between the inner cylindrical surface (124) and the piston radial surface (141) and communicating with a source of pressurized fluid to displace the piston (122) into the extended or retracted position; and d) a probe (180) extending through the cylinder housing (120) and communicating with the measurement sensing means (178) for sensing displacement of the piston (122) as it moves between the extended and retracted positions; and e) wherein the measurement detection device (178) comprises a plurality of annular piston teeth (182) which are concentric with the cylinder axis (121) and extend axially at intervals along the piston radial surface (141); f) the probe (180) has a gear (184) comprising teeth (188) extending into the pressure chamber (136, 138) and meshing with cylindrical piston teeth (182), wherein displacement of the piston (122) results in rotation of the gear (184). [11] Injection unit according to claim 10, further comprising a shot cavity for holding an injection mass, wherein the displacement of the piston (122) to the retracted position is accompanied by the filling of the shot cavity with injection mass, and the displacement to the extended position is accompanied by the injection of the injection mass from the shot cavity into the mold, and wherein the pressure chamber (136, 138) presses the piston (122) into the retracted position when pressurized. [12] Injection unit according to claim 10 or 11, wherein the cylinder housing (120) has an outer surface arranged radially outwardly at a distance from the inner cylindrical surface (124) with a cavity (202) located therebetween, the cavity (202) having opposite open ends (204, 206) of the inner cylindrical surface (124) and the outer surface, respectively, and wherein at least a part of the probe (180) is located in the cavity (202). [13] Injection unit according to one of claims 10 to 12, wherein the probe (180) further comprises a shaft (190) rotated by the gear (184) and connected to a sensor (196) for detecting the rotation of the shaft (190). [14] Injection unit comprising a) a cylinder housing (120) having an inner cylindrical surface (124) and extending along a cylinder axis (121); b) a piston (122) disposed in the cylinder housing (120) and displaceable along the cylinder axis (121) between an extended and a retracted position, the piston (122) having a piston radial surface (141) opposite the inner cylindrical surface (124); the piston radial surface (141) includes a measurement detection device (178); c) a pressure chamber (136 138) extending radially between the inner cylindrical surface (124) and the piston radial surface (141) and communicating with a source of pressurized fluid to displace the piston (122) into the extended or retracted position; and d) a probe (180) extending through the cylinder housing (120) and communicating with the measurement sensing means (178) for sensing displacement of the piston (122) as it moves between the extended and retracted positions; and e) wherein the measurement detection device (178) comprises an axially tapered part of the piston radial surface (141), and wherein the probe (180) has a distance sensor (635) for detecting the distance of the piston radial surface (141) from the distance sensor (635). [15] Injection unit according to claim 8, wherein the piston (122) is rotatable about the cylinder axis (121) while moving axially within the cylinder housing (120). [16] Injection unit comprising: a) a cylinder housing (120) comprising an inner cylindrical surface (124) and extending along a cylinder axis (121); b) a piston (122) received by the cylinder housing (120) and movable along the cylinder axis (121) between an extended and a retracted position, and having a piston radial surface (141) opposite the inner cylindrical surface (124), and wherein the piston radial surface (141) includes a measurement detection device (178), wherein the measurement detection device (178) has a plurality of annular piston teeth (182) which are concentric with the cylinder axis (121) and axially spaced along the piston radial surface (141); c) a pressure chamber (136, 138) extending radially between the inner cylindrical surface (124) and the piston radial surface (141) and containing a fluid for displacing the piston (122) when pressurized; and d) a probe (180) fixed relative to the cylinder housing (120) and extending through the pressure chamber (136, 138), the probe (180) including a gear (184) having teeth (188) extending into the pressure chamber (136, 138) and meshing with the annular piston teeth (182), whereby displacement of the piston (122) causes rotation of the gear (184) to continuously sense the axial position of the piston (122) relative to the cylinder housing (120) as the piston (122) moves between the extended and retracted positions. [17] A method for measuring the displacement of a piston (122) in a cylinder, comprising: a) a measurement detection device (178) is provided along an outer piston radial surface (141) of a piston (122), the measurement detection device (178) being fixed relative to the piston (122), the measurement detection device (178) having a plurality of annular piston teeth (182) which extend concentrically to a cylinder axis (121) and axially at intervals along the piston radial surface (141) between the first (134) and second seal bearings (142); b) continuously engaging the measurement sensing device (178) with a probe (180) as the piston (122) moves between the extended and retracted positions, the probe (180) comprising a gear (184) having teeth (188) extending into a pressure chamber (136, 138) and meshing with the annular piston teeth (182), whereby displacement of the piston (122) results in rotation of the gear (184), and the probe (180) is axially fixed relative to the cylinder housing (120), and the probe (180) provides an output signal accessible from outside the cylinder housing (120).

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