Fluid transfer coupling

Abstract

A coupling for conveying a fluid between a stationary part and a rotatable part having confronting ports centered on a rotation axis of the rotatable part has an axially extending tube fixed in the port of one of the parts and extending toward the port of the other of the parts and a control element axially slidable on the tube. The one part, the tube, and the control element form an annular chamber around the tube pressurizable for axially shifting the control element. A first slide ring is connected to the control element and carries a seal ring turned toward the port of the other part, and a second ring on the other part at the port thereof axially bears on the first slide ring so that pressurization of chamber presses the slide rings axially against each other.

Claims

1. A coupling for conveying a fluid from a source and thence between a stationary part and a rotatable part having confronting ports centered on a rotation axis of the rotatable part, the coupling comprising: an axially extending tube fixed in the port of the stationary part and extending toward the port of the rotatable part; a control sleeve axially slidable on and coaxially surrounding the tube; a first slide ring fixed to the control sleeve and carrying a seal ring turned toward the port of the rotatable part; a second slide ring on the rotatable part at the port thereof and axially engageable with the first slide ring, the tube, control sleeve, first ring, and second ring together forming an axially throughgoing passage for the fluid; seals engaged between the stationary part, the tube, and the control sleeve and forming an annular and pressurizable chamber around the tube, separate from the passage, and in which an axially directed and annular end face of the axially slidable control sleeve is exposed, whereby pressurization of the chamber presses the slide rings axially against each other; and means for applying fluid pressure to the chamber and thereby varying the axial pressure with which the first slide ring bears axially on the second slide ring.

2. The fluid-transfer coupling defined in claim 1, further comprising: a temperature sensor juxtaposed with the first slide ring for detecting the temperature thereof; and a controller connected to the sensor for operating the pressure-applying means in accordance with an output of the sensor.

3. The fluid-transfer coupling defined in claim 1, further comprising: a conduit connected to the stationary part for feeding the fluid thereto, the means for applying pressure including a valve connected to the conduit for diverting the fluid therefrom to the chamber.

4. The fluid-transfer coupling defined in claim 1, further comprising: a spring braced between the one part and the control sleeve for axially biasing the first slide ring against the second slide ring.

5. The fluid-transfer coupling defined in claim 1, further comprising: a pressure-control and reducing valve connected to the source of the fluid; a conduit opening into the chamber; and a reversing valve between the pressure valve and the conduit and connected to a sump for connecting the conduit either to the pressure valve and thereby pressurizing the chamber or to the sump to depressurize the chamber.

6. The fluid-transfer coupling defined in claim 1 wherein the tube and control sleeve are coaxial.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

(2) FIG. 1 is an axial section through the coupling according to the invention for installation in a machine tool;

(3) FIG. 2 is an axial section through the coupling of FIG. 1 for a detached tool;

(4) FIG. 3 is an end view of the slide ring of the coupling;

(5) FIG. 4 shows the invention as in FIG. 1 with a schematically shown arrangement for actuation;

(6) FIG. 5 shows an alternative embodiment to FIG. 4; and

(7) FIG. 6 shows a conventional axial slide-ring seal combined with the solution according to the invention with adjustable contact pressure between the slide and counter rings in the system of FIG. 2.

SPECIFIC DESCRIPTION OF THE INVENTION

(8) As seen in FIG. 1, a fluid-transfer coupling serves to convey fluid between a stationary part 3 and a rotating part 10. This can be in particular a coupling for conveying fluid under pressure and elevated temperatures to supply a gaseous or liquid cooling and/or lubricating medium 4 from the stationary part 3 to a rotating spindle forming the rotating part 10.

(9) To do so, at least one slide-ring seal is provided that is formed of a nonrotating slide ring 7 and a rotating counter ring 9 sealing it and between the respective stationary and rotating parts 3 and 10. An axially effective control element is provided that, depending on ambient and operating conditions or parameters of the coupling, adjusts the axial position of the slide ring 7 and/or counter ring 9, and thus the axial contact pressure acting between them. The control element is thereby arranged on a tube 12 through which the medium passes.

(10) In detail, a housing 1 of the coupling is centered in a seat 2 of the machine tool spindle/stationary part 3 and secured therein by screws 6 as also shown in FIG. 3. A cooling and lubricating medium is supplied via a conduit 4 to an inlet port of the part 3. The sealing of the part 3 and housing 1 to each other is achieved by a seal 5 integrated in the coupling.

(11) The axially moveable slide ring 7 has a hole for fluid throughflow. The slide ring 7 projects axially outward and surrounds an axial seal ring 7a (an end view of the slide ring 7 is shown in FIG. 3). The seal ring 7a can be made of various suitable sealing materials, such as silicone, carbon, or coated materials, and is either shrunken or adhered into the slide ring 7.

(12) As shown in FIG. 2, two studs 8 screwed into the slide ring 7 engage with play in respective cylindrical guides 8b and angularly lock the ring 7 to the housing 1 fixed in the housing 3. A collar 8a of each stud 8 limits the axial travel of the respective stud 8 in the respective guide 8b. It serves to prevent the slide ring 7 from disengaging, so that it cannot move in an uncontrolled manner out of the guides 8b and seals. The slide ring 7 has in the region of the seal ring 7a a radially open hole 7d (see also FIGS. 1 and 3). A temperature sensor 7b in it is set in a heat-conducting cast-resin body 7c. The slide ring 7 bears axially on another seal ring 9c set in the counter ring 9. Here, the counter ring 9 is screwed into the rotating motor spindle 10 and is coaxial with the slide ring housing 1.

(13) The counter ring 9 is adjacent to the slide ring 7. It has an axially centered passage for the medium to pass through. A seal 9b prevents the lubricant from leaking out between the spindle 10 and the counter ring 9. The actual seal surface is formed by the tightly embedded seal ring 9c that bears with its end face in surface contact with the seal ring 7a.

(14) The center of the slide ring 7 is extended by a cylindrical sleeve 7e extending through a passage 13 of the slide ring housing 1 in the flow direction and sealed by a gland seal 11 relative to the housing 1. This sleeve 7e fits around and slides on the tube 12 that is axially fixed, here by a collar 14 and a retaining ring 15, in the housing 1.

(15) Sealing between the tube 12 and the housing 1 is effected a ring seal 16, and between the tube 12 and the sleeve 7e by another ring seal 17. By this structural measure, a sealed, annular chamber 18 is created. In it is formed the hydraulically acting piston face of the sleeve 7e of the slide ring 7, closing the seal gap, and specifically via diameters A and B according to FIG. 1, without any influence resulting from the actual medium pressure 4. This pressure chamber 18 is connected via radial and axial holes 19 to a control conduit 24 of the arrangement. Alternatively, there is also the possibility of creating the connection to the control conduit 24 via a radial system connection on the housing 1.

(16) This control line 24 can be fed from various sources:

(17) In the embodiment according to FIG. 4, a pressure line 21 of the existing hydraulic system of a machine tool is connected via a proportional pressure adjustment valve 22 to the conduit 24 of the coupling. Normally, the control pressure corresponds to the pressure of the cooling medium, thus at 80 bar of lubricant pressure, the controller sets 80 bar of control pressure at the proportional valve 22. If the temperature at the sealing surface of slide ring 7 exceeds a specified value, e.g. because the cooling and lubricating effect of the medium used in the seal gap is no longer sufficient, the pressure is reduced in steps. The contact pressure of the slide ring 7 is reduced, more lubricant can enter into the seal gap, and the temperature drops. The load and wear on the slide-ring seal decrease.

(18) For seal kits that are equipped with a quantitative leakage detection means (which can be integrated in the hose line or in housing 1), the actual value of the leakage can also be used to establish the contact pressure. If the leakage is excessive, the closing pressure is corrected upward. The slide ring temperature can also be used as a correction value. If the slide ring temperature is too low, the contact force is increased, depending on the type and pressure of the medium, like when the leakage is too high. The slide-ring seal is controlled either directly in the machine controller or by an external control unit. Since the design details of the electronic controller are not part of this invention, they will not be described extensively.

(19) The embodiment according to FIG. 5 assumes that no external hydraulic supply is available for controlling the contact pressure. Then, the cooling medium 4 to be delivered is used for supply purposes. To do so, liquid cooling lubricants are passed through a filter 26 via a proportional pressure adjustment valve 27 to the control line. The electronic control function functions as in the example described above with an external hydraulic fluid supply. The control oil pressure is delivered, separated or decreased via directional valves 28 and 29.

(20) For compressed air or gaseous fluid, a directional valve 30 directs this energy source 32 as a control fluid via a pressure regulating valve 31 to the conduit 24.

(21) FIG. 2 shows the state of the tool change coupling for a detached tool. In doing so, the counter ring 9 moves in an axial direction so that the collet chuck can be loosened and the tool holder can be removed. To prevent dirt particles from entering between the seal surfaces, the seal rings 7a and 9c should always remain in surface contact.

(22) In the invention, this can take place by two different couplings:

(23) A conical spiral spring 20 (shown in FIGS. 1 and 2) is installed in the annular chamber 18. This spring 20 permanently presses the slide ring against the counter ring. This solution is currently used in conventional slide-ring seals. However, it shall be noted that the contact force changes with the spring travel.

(24) Instead of the spring, this invention allows one to supply a certain air pressure to the annular chamber 18 via the control line. This has the advantage that the pressure then corresponds to a constant contact force.

(25) A possible variant of the new solutions shown in FIGS. 1 and 2 is illustrated in FIG. 6. In addition to the already described possibility for generating a variable contact force between the slide and counter rings, there results an additional partial load resulting from the fluid pressure to be sealed off, similar to a conventional axial slide-ring seal. As emerges from FIG. 6, this is structurally realized in that diameter B at seal ring 7a and slide ring 7 is no longer identical, but have various diameters B or B*.