Toolholder Matched with the Internal Jet Cooling Spindle for Cryogenic Coolant

Abstract

The invention provides a toolholder matched with the internal jet cooling spindle for cryogenic coolant. The toolholder is mainly composed of a hollow toolholder body, a high-performance thermal insulation structure and a bidirectional sealing structure. They can guide the cryogenic coolant from the spindle to the internal cooling channel of tool and realize the cryogenic thermal insulation and dynamic sealing. The high-performance thermal insulation structure inside the toolholder employs the material with a low thermal conductivity and a low linear expansion coefficient to restrain the low temperature impact of cryogenic coolant on the toolholder and spindle, to ensure the dimensional accuracy and assembly accuracy of the toolholder. The bidirectional sealing structure in the toolholder uses the ultra-low temperature resistant seal rings to prevent the cryogenic coolant from leaking towards the spindle and the tool, to ensure the stability of the coolant transport.

Claims

1. A toolholder matched with the internal jet cooling spindle for cryogenic coolant, wherein mainly composing of a hollow toolholder body, a high-performance thermal insulation structure and a bidirectional sealing structure; the hollow toolholder body is of a hollow structure to provide a channel for cryogenic coolant transport; the high-performance thermal insulation structure is arranged inside the hollow structure of the hollow toolholder body to suppress the diffusion of the cryogenic temperature field to the toolholder and spindle; the bidirectional sealing structure is designed in the hollow toolholder body to prevent the leakage of cryogenic medium towards the spindle and the cutting tool; the hollow toolholder body is the toolholder body; outer cone surface of toolholder body is the positioning surface connected with spindle; external thread on the front outer circle is used to install locking nut for clamping the cutting tool; inner cone surface on the front end is used to install spring collet; the above three surfaces are the main working surfaces of the toolholder; the hollow toolholder body provides the cryogenic coolant transport channel as well as the installation space and positioning surface required by the high-performance thermal insulation and bidirectional sealing structures; inner cavity bottom surface), inner cavity surface, inner hole, tool escape and internal thread are processed in the toolholder body; the internal thread is connected with the inner cone surface; the tool escape is located between the internal thread and the inner cavity surface; the inner cavity surface is a cylindrical surface which is located inside the outer cone surface; the inner cavity bottom surface is the vertical bottom surface of the inner cavity surface which is located in the end direction of the toolholder body; the inner hole is located in the thinnest end of the outer cone surface, and shaft inside spindle extends into the toolholder body through the inner hole to transmit cryogenic coolant; there are four flange-via holes on the horizontal flange surface of the toolholder body, which are used to connect and fastening the spindle; the horizontal flange surface is located between the outer cone surface and the external thread; the high-performance thermal insulation structure orderly includes the thermal insulation sleeve, the compression sleeve and the locking sleeve; the thermal insulation sleeve is located inside the inner cavity surface, which is the main structure to isolate the cryogenic coolant from the toolholder body; the compression sleeve is installed in the inner thread to provide a compression force for the thermal insulation sleeve and an installation groove for the outer seal ring; the locking sleeve is also installed in the inner thread, which is used to press out the outer seal ring and fasten the compression sleeve; the bidirectional sealing structure includes inner seal ring and outer seal ring which are ultra-low temperature resistant; the inner seal ring and the outer seal ring are located inside the toolholder body to prevent cryogenic coolant from leaking towards the spindle and the tool; while assembling the toolholder, first the inner seal ring is pushed into the toolholder body along the inner cavity surface while the sealing surface is outward, meanwhile the opposite side of the inner seal ring is ensured in contact with the inner cavity bottom surface; the thermal insulation sleeve is installed into the toolholder body along the inner cavity surface in the form of interference until it is pressed against the inner seal ring, meanwhile the tool positioning plane on the thermal insulation sleeve is kept outward; then two auxiliary holes on the compression sleeve are clamped with a tooling to screw the compression sleeve along the internal thread until it is pressed against the thermal insulation sleeve; finally, the outer seal ring is installed into the groove of the compression sleeve while its sealing surface is inward, and the two auxiliary holes II are clamped with the tooling so that the locking sleeve is screwed along the internal thread to press out the outer seal ring; finally, the inner seal ring, the thermal insulation sleeve, the compression sleeve and the outer seal ring are orderly pressed out; meanwhile, the locking function is realized by the compression sleeve and the locking sleeve, the toolholder assembly is ultimately accomplished; while installing the cutting tool, first the spring collet is installed into the locking nut, and the end face is superposed; the locking nut along with the spring collet is screwed on the toolholder body along the external thread; then, the internal cooling tool is inserted into the spring collet until its end face is pressed against the tool positioning plane of the thermal insulation sleeve, meanwhile the outer surface of the internal cooling tool and the inner surface of the outer seal ring have an interference fit; finally, the locking nut is tightened using a wrench, the cutting tool installation is ultimately accomplished; during processing, the outer cone surface of the toolholder body which has been assembled and installed with the tool is installed into the cone hole of the spindle; the shaft is inserted into the toolholder body through the inner hole and formed an interference fit with the inner seal ring; a certain gap is retained between the shaft end face and the thermal insulation sleeve inner end face; the four bolts are screwed into the four spindle threaded holes through the four flange-via holes, and a torque wrench is used to tighten with a value; thus, the outer cone surface of the toolholder body and the cone surface of spindle are closely matched to realize the installation and position of the toolholder; while the cryogenic coolant delivery system is started, liquid nitrogen is jetted to the nose of blade through the shaft inner channel, the toolholder inner channel and the tool inner channel orderly.

2. The toolholder matched with the internal jet cooling spindle for cryogenic coolant according to claim 1, wherein the materials of the thermal insulation sleeve, the compression sleeve and the locking sleeve have a low thermal conductivity and a low linear expansion coefficient.

3. The toolholder matched with the internal jet cooling spindle for cryogenic coolant according to claim 1, wherein the inner seal ring and the outer seal ring are made of materials which are ultra-low temperature resistant.

4. The toolholder matched with the internal jet cooling spindle for cryogenic coolant according to claim 1, wherein the toolholder body and the spindle are connected and fastened by the flange; the operation is easy, safe, and reliable.

5. The toolholder matched with the internal jet cooling spindle for cryogenic coolant according to claim 3, wherein the toolholder body and the spindle are connected and fastened by the flange; the operation is easy, safe, and reliable.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0015] FIG. 1 is the schematic diagram of the toolholder body 1.1.

[0016] FIG. 2 is the schematic diagram of the toolholder assembly.

[0017] FIG. 3 is the schematic diagram of the installation of toolholder and spindle.

[0018] FIG. 4 is the schematic diagram of the temperature measurement of cone surface of the toolholder.

[0019] FIG. 5 is the temperature curve of the cone surface of toolholder.

[0020] In Figure: 1.1—toolholder body; 1.2—inner seal ring; 1.3—thermal insulation sleeve; 1.4—compression sleeve; 1.5—outer seal ring; 1.6—locking sleeve; 1.7—flange-via hole; 1.8—spring collet; 1.9—locking nut; 1.10—bolt; 1.a—inner cavity bottom surface; 1.b-—internal thread; 1.c-external thread; 1.d—auxiliary hole I; 1.e—auxiliary hole II; 1.f-—thermal insulation sleeve inner end face; 1.g—tool positioning plane; 1.h—inner cone surface; 1.i—outer cone surface; 1.j—inner cavity surface; 1.k—end face; 1.m—tool escape; 1.n—inner hole; 2.1—spindle; 2.2—spindle threaded holes; 2.3—shaft; 2.4—internal cooling tool; 2.5 —blade; 2.a—shaft end face; 3.1—shaft inner channel; 3.2—toolholder inner channel; 3.3—tool inner channel; 4.1—temperature sensor.

DETAILED DESCRIPTION

[0021] The specific embodiments of the present invention will be described in detail below with reference to the drawings and technical solutions:

[0022] In the embodiment, the cryogenic coolant is liquid nitrogen, and the material of thermal insulation sleeve 1.3, compression sleeve 1.4 and locking sleeve 1.6 are all modified polyimide with thermal conductivity less than 0.15 W/(m.Math.K). The wall thickness of thermal insulation sleeve 1.3 is 8 mm. The inner seal ring 1.2 and outer seal ring 1.5 are lip seals, and their materials are carburized polytetrafluoroethylene. The working temperature for seals ranges from −200 to 260° C., the maximum pressure is 3 MPa. The type of toolholder body 1.1 is BT40, the accuracy of cone is AT3 and its hardness is more than HRC55. The type of spring collet 1.8 is ER32, and its inner diameter is Φ13-14. The shaft 2.3 is of vacuum insulation structure. The outer diameter of the internal cooling tool 2.4 is 14 mm. The measurement range of temperature sensor 4.1 is −200-100° C.

[0023] The assembly and installation process of the toolholder is as follows. As shown in FIGS. 1, 2 and 3, step one, the sealing surface of the inner seal ring 1.2 and the tool positioning plane 1.g of the thermal insulation sleeve 1.3 are kept outward. And then the inner seal ring 1.2 and the thermal insulation sleeve 1.3 are orderly pushed into the toolholder body 1.1 along the inner cavity surface 1.j in the way of interference fit, until the inner seal ring 1.2 is pressed against the inner cavity bottom surface 1.a meanwhile the thermal insulation sleeve 1.3 is pressed against the inner seal ring 1.2. The two auxiliary holes I 1.d on the compression sleeve 1.4 are clamped with a tooling to screw the compression sleeve 1.4 along the internal thread 1.b until it is pressed against the thermal insulation sleeve 1.3. The outer seal ring 1.5 is installed into the groove of the compression sleeve 1.4 while its sealing surface is inward. The two auxiliary holes II 1.e are clamped with the tooling to screw the locking sleeve 1.6 along the internal thread 1.b and press out the outer seal ring 1.5.

[0024] Step two, the spring collet 1.8 is installed into the locking nut 1.9 meanwhile the end face 1.k is ensured coincident. Then, the locking nut 1.9 with the spring collet 1.8 is screwed on the toolholder body 1.1 along the external thread 1.c. The internal cooling tool 2.4 is inserted into the spring collet 1.8 until its end face is pressed against the tool positioning plane 1.g of the thermal insulation sleeve 1.3, also, the outer surface of the internal cooling tool 2.4 and the inner surface of the outer seal ring 1.5 have an interference fit. Finally, the locking nut 1.9 is tightened using a wrench.

[0025] Step three, the outer cone surface 1.i of the toolholder body 1.1 is installed into the cone hole of the spindle 2.1. The shaft 2.3 is inserted into the toolholder body 1.1 through the inner hole 1.n to form an interference fit with the inner seal ring 1.2. The shaft end face 2.a and the thermal insulation sleeve inner end face 1.f keep a gap of 1 mm. The four bolts 1.10 are screwed into the four spindle threaded holes 2.2 through the four flange-via holes 1.7. A torque wrench is used to tighten the four bolts 1.10 with a torque of 10 N.Math.m, so that the outer cone surface 1.i of the toolholder body 1.1 is fitted closely with the cone surface of the spindle 2.1.

[0026] Step four, the liquid nitrogen convey system is started, and then liquid nitrogen is jetted to the nose of blade 2.5 through the shaft inner channel 3.1, the toolholder inner channel 3.2 and the tool inner channel 3.3 in turn. At the moment, the machining can be started. The machining is stopped every 5 minutes and the toolholder is removed, and then the temperature of the outer cone surface 1.i is measured by the temperature sensor 4.1. The measurement process and results are shown in FIG. 4 and FIG. 5, respectively. The results show that the surface temperature of the toolholder is about 8° C. and no frost is found.

[0027] The invention effectively eliminates the ultra-low temperature impact of cryogenic coolant on the toolholder through the thermal insulation and sealing structure, to ensure the accuracy of the toolholder and the stability of liquid nitrogen transport. The toolholder accomplishes the connection between the internal jet cooling spindle and the internal cooling tool, to assist the special cryogenic cooling machine tool to implement cryogenic machining under the internal jet cooling mode of cryogenic coolant. For the toolholder, the integral structure is simple, the integration is good, as well as the operation is safe and reliable.