Synchronizing cylinder for extruder

Abstract

A double-rod ram (1), preferably for an extruder, comprising an outer cylinder (10), an inner cylinder (20) installed therein and arranged concentrically therewith, a double-acting work piston (41) provided in the inner cylinder to be displaceable and a bypass device (50) with at least one bypass valve (52), wherein the work piston (41) divides the inner cylinder (20) into two compartments (42) and can be loaded with a hydraulic fluid from both compartments (42), wherein the bypass device (50) is so arranged that in a bypass position of the bypass valve (52) a fluid connection between the two compartments (42) is formed by a direct connection, preferably at least one bypass line, and in a work position of the bypass valve (52) no such fluid connection is present.

Claims

1. A double-rod ram for an extruder, the ram comprising: an outer cylinder extending along an axis; an inner cylinder installed therein and coaxial therewith; a double-acting work piston axially displaceable in the inner cylinder and subdividing same into a pair of compartments pressurizable with a hydraulic fluid; and two bypass valves axially flanking the work piston and movable between respective bypass positions forming a direct fluid connection between the two compartments and respective work positions in which no such fluid connection is present.

2. The double-rod ram according to claim 1, wherein the direct connection is a bypass line formed between the outer cylinder and the inner cylinder of the double-rod ram.

3. The double-rod ram according to claim 1, further comprising: a return spring biasing the bypass valve into the bypass position or the work position.

4. The double-rod ram according to claim 3, wherein the return spring is provided partly or completely inside the outer cylinder.

5. The double-rod ram according to claim 1 wherein the bypass valve is hydraulically actuatable.

6. The double-rod ram according to claim 1, wherein the outer cylinder is closed at each of its ends by a respective cylinder closure, the inner cylinder is fixed at each of its ends relative to the outer cylinder by a respective cylinder head support, and a respective hydraulic fluid connection and hydraulic fluid line that are formed in the cylinder closure and/or cylinder head support of the corresponding side, are provided at each of the two ends.

7. The double-rod ram according to claim 6, wherein the two cylinder head supports each have one or more bypass ducts forming a fluid connection between the compartments and an annular gap between the inner and outer cylinders.

8. The double-rod ram according to claim 7, wherein the bypass valves are in contact not only with the piston rod, but also with the corresponding cylinder head support and in the work position close and in the bypass position open the fluid connection between the corresponding compartment and the corresponding bypass duct.

9. A double-rod ram for an extruder, the ram comprising: an outer cylinder extending along an axis; an inner cylinder inside the outer cylinder, coaxial with the outer cylinder, and forming a with the outer cylinder; a double-acting work piston axially displaceable in the inner cylinder and subdividing same into a pair of compartments pressurizable with a hydraulic fluid; a bypass line extending between the compartments and outside the housing; and a bypass valve movable between a bypass position forming a direct fluid connection through the bypass line between the two compartments and a work position in which no such fluid connection is present.

10. A shaping apparatus having a double-rod ram comprising: an outer cylinder extending along an axis; an inner cylinder installed therein and coaxial therewith; a double-acting work piston axially displaceable in the inner cylinder and subdividing same into a pair of compartments pressurizable with a hydraulic fluid; and a bypass valve movable between a bypass position forming a direct fluid connection between the two compartments and a work position in which no such fluid connection is present.

11. The shaping apparatus according to claim 10, further comprising: one or more electric motors for actuating the double-rod ram.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 is a longitudinal section of a double-rod ram in a first form of embodiment of the invention.

(2) FIG. 2 shows a detail of a longitudinal section through a double-rod ram with a modified construction.

(3) FIG. 3 shows an installation position of a double-rod ram in the extruder.

(4) FIG. 4 shows a further form of embodiment of the invention with an outer bypass line.

(5) FIG. 5 shows a further form of embodiment of the invention with a plurality of bypass lines integrated in the double-rod ram.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(6) Preferred embodiments are described in the following on the basis of FIG. 1. In that case identical, similar or equivalent elements are provided with identical reference numerals and repeated description of these elements is partly dispensed with so as to avoid redundancies.

(7) FIG. 1 shows a double-rod ram 1. More precisely, the two ends of the cylinder 1 are shown in longitudinal section that in the present embodiment are constructed substantially in mirror symmetry.

(8) The hydraulic cylinder 1 has a hollow outer cylinder 10, a hollow inner cylinder 20, and on each of the left and the right a head section 30 and a piston rod 40 with a work piston 41 integrated therein or connected therewith. The head section 30 has a cylinder head support 31 and a cylinder closure 33, whereby the hydraulic cylinder 1 is closed at both ends and the inner cylinder 20 is fixed relative to the outer cylinder 10. The inner cylinder 20 is inserted into the outer cylinder 10 and the two lie concentrically relative to one another, so that an annular gap 51 that is a component of a circumventing or bypass device 50 described later in detail, is formed between the inner cylinder 20 and the outer cylinder 10. The work piston 41 is displaceably mounted in the inner cylinder 20. The piston rod 40 extends on either side of the work piston 41, penetrates the respective head sections 30 and is guided by these. Seals and parts for mounting the piston rod 40 and the work piston 41 that ensure problem-free operation of the hydraulic cylinder 1, can be provided at suitable points, these being partly illustrated in FIG. 1, but not described in more detail.

(9) Disposed on the left and right of the work piston 41 are compartments 42 that are surrounded and thereby defined by the work piston 41, the inner cylinder 20 and components at the head side, such as, for example, the cylinder head support 31 and a bypass valve 52 which is described later. The work piston 41 is acted on from both sides by a pressure medium or hydraulic fluid, for example a hydraulic oil, present in the compartments 42. The hydraulic fluid is supplied to the compartments 42 by bores of lines, here termed hydraulic fluid lines 32. The hydraulic fluid lines 32 extend through the two head sections 30. The hydraulic fluid lines 32 can have a hydraulic fluid connection 32, a hydraulic fluid ring line 32 and other components suitable for reliably feeding hydraulic fluid under pressure to the compartments 42, distributing it and discharging it, or can be connected therewith in terms of fluid flow.

(10) A pressure difference of the hydraulic fluid between the two compartments 42 produces a force on the work piston 41 which can lead to displacement of the work piston 41 in axial direction and thus of the piston rod 40. For that purpose, an inflow of hydraulic fluid into one of the two compartments 42 by the relevant hydraulic fluid line 32 and a displacement of the hydraulic fluid into the other compartment 42 take place, hydraulic fluid being discharged by the other hydraulic fluid line 32. Because the effective area of the work piston 41 on both sides is of the same size, the hydraulic cylinder 1 acts as a double-rod ram, also termed synchronizing cylinder. This mode of operation is termed work mode for distinction from a towed mode of operation which is described in the following and which enables a pressure-free or low-pressure displacement of the work piston 41.

(11) For rapid, pressure-free movement of the work piston 41, for example for position or adjusting a receiver in an extruder, the hydraulic cylinder 1 has a bypass device 50. In the present example this comprises the annular gap 51, the two bypass valves 52, bypass ducts 53 that are in fluid connection with the annular gap 51, and actuators 54. The two bypass valves 52 are guided on the piston rod 40 in the region of the two head sections 30 and open and close the bypass lines 53 in that they are actuated, i.e. displaced, by the actuator 54 in axial direction. When the bypass valve 52 is open, the hydraulic fluid can pass from the hydraulic chamber 42 concerned into the adjacent bypass duct 53 and from there the hydraulic fluid passes into the annular gap 51. If both bypass valves 52 are open, the work piston 41 can in this way displace without force or with low force, since the fluid connection between the two compartments 42 exists by the bypass ducts 53 and the annular gap 51. In that case, the annular gap 51 through its external arrangement and annular shape enables, in particular, optimum behavior in terms of flow.

(12) Actuation of the bypass valves 52 takes place by the actuators 54. In the present example these each comprise an actuating rod 54 that is biased by a spring and extends through the respective head section 30 and which is connected with the bypass valve 52, and an actuating hydraulic section 54 with an actuating connection 54, a bore and a chamber (without reference numerals). Due to the fact that the bypass valve 52 is biased, here, by example, by the spring, the bypass valve 52 is automatically brought into a preferential position. The actuating valve 52 is actuated by a fluid being introduced into or let off from the actuating hydraulic section 54 by the actuating connection 54.

(13) The bypass device 50 for pressure-free or low-pressure movement of the work piston 41 is realized by the above-described annular gap 51 that runs through the concentric hollow cylinders 10 and 20 externally around the work piston 41. This technical solution is space-saving and highly satisfactory with respect to flow relationships, because the annular gap 51 has the lowest flow losses by comparison with other solutions. The annular bypass valves 52 that are here illustrated by example and which are guided on the piston rod 40 concentrically therewith, allow rapid and reliable switching over of the modes of operation of the hydraulic cylinder 1. A selective control of the transfer flow of hydraulic fluid between the two compartments 42 or from the annular gap 41 to the compartments 42 is thus realized in a technically simple manner which is non-susceptible to fault and is durable. Moreover, the technical solution illustrated here has a small number of hydraulic connections, whereby operation of the hydraulic cylinder 1 is further simplified.

(14) FIG. 2 shows a construction modified with respect to the actuator 54. For the purpose of illustration, there is shown merely a detail of the longitudinal section through the double-rod ram 1, but this can be of substantially mirror-symmetrical construction as in FIG. 1.

(15) By contrast with the double-rod ram of FIG. 1, the actuator 54 for actuation of the bypass valves 52 does not have an actuating rod 54 with an externally disposed restoring spring, but restoration or biasing of the bypass valve 52 takes place by an internally disposed spring 55. The actuating hydraulic section 54 with the actuating connection 54 is substantially unchanged. At that end of the actuating hydraulic section 54 which is opposite the actuating connection 54 there is provided an annular chamber (without reference numeral, but readily recognizable in FIG. 2) which at one side adjoins the bypass valve 52. The actuation of the bypass valve 52 takes place like in the embodiment of FIG. 1; i.e. since the bypass valve 52 is biased, here according to FIG. 2 by the internally disposed spring 55, the bypass valve 52 is automatically brought into a default position. The actuating valve 52 is actuated by a fluid being introduced into or let out from the actuating hydraulic section 54 by the actuating connection 54.

(16) By virtue of the slender construction, the double-rod ram 1 can be led through a cylinder beam of an extruder. For this reason, the hydraulic cylinder 1 is usable, with particular preference, in the field of extruders, particularly for realization of receiver kinematics, inclusive of the force function. It has the great advantage that it can be converted by pressure-free adjustment over the entire stroke from towed operation to work operation. The double-rod ram 1 is thus capable of assisting, in all positions, any electric motors for rapid movement over the complete stroke with the full cylinder force.

(17) The installation position of the double-rod ram 1 in an extruder 100 is shown in FIG. 3. The double-rod ram 1, the construction of which in FIG. 3 is shown in less detail than in the preceding figures, is guided by a cylinder beam 101. One end of the piston rod 40 is connected with a receiver 102 that is movable by the double-rod ram 1, for example, between a position for ingot change and a front end position, the work position, at which pressing against, releasing and stripping take place.

(18) Alternatively, the receiver 102 can be moved by one or more electric motors (not illustrated) which displace the receiver 102 between the ingot change position and the work position. The double-rod ram 1 is in that case moved externally. For such an external movement, i.e. for rapid, pressure-free actuation of the double-rod ram 1, this is switched over in the above-described manner to the towed mode of operation.

(19) FIG. 4 shows an alternative form of embodiment of the double-rod ram 1 according to the invention in which in departure from the first form of embodiment according to FIGS. 1 to 3 a bypass device 50 in the form of a bypass line 103 is outside the housing and the compartments 42 are connected together by respective bypass valves 52. The bypass line 103 replaces the annular gap between the outer cylinder 10 and inner cylinder 20 according to the forms of embodiment of FIGS. 1 to 3. However, the bypass line 103 achieves the same technical results as the annular gap 51 according to the forms of embodiment of FIGS. 1 to 3.

(20) FIG. 5 shows a further form of embodiment of the double-rod ram 1 according to the invention in a side view as well as an end view sectioned along the line A-A of FIG. 5a. It can be seen from the end view according to FIG. 5b that four bypass lines 103a-d are arranged within the housing of the double-rod ram 1 outside the outer cylinder 10. These bypass lines 103a-d entirely replace, just like the bypass line 103 according to FIG. 4, the annular gap 51 according to the forms of embodiment of FIGS. 1 to 3. The bypass lines 103a-d connect, just like the bypass line 103 according to FIG. 4, the compartments 42 of the double-rod ram 1.

(21) Insofar as feasible, all individual features illustrated in the embodiments can be combined with one another and/or interchanged without departing from the scope of the invention. Not all technical features illustrated in the scope of the exemplifying forms of embodiment need to be essential to the invention. Thus, for example, the inflow and outflow between the annular gap 51 and the compartments 42 can be realized in a different way than by the bypass ducts 53 illustrated here. In addition, the bypass valves 52 can be differently constructed and/or positioned, although the described technical solution is preferred.