Turning – Lathe – Headstock
Patent
1989-09-19
1991-08-06
Bilinsky, Z. R.
Turning
Lathe
Headstock
279 1DC, 408240, 409232, B23B 3120
Patent
active
050367358
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to metal working and, more particularly, to a bar-clamping device.
DESCRIPTION OF THE PRIOR ART
Broaching of deep holes in long bars involves a problem of their accurate positioning and centering in length.
Known in the prior art (SU, A, 1,219,268) is a collet chuck comprising a body which accommodates a collet linked with a rod. Installed inside the chuck is a bushing linked with the rod and provided with flexible tabs whose ends have, both on the inner and outher sides, lugs with tapered surfaces facing the rod. The body and collet extension have grooves meant to accommodate the lugs of the bushing tabs. However, when this desing of the collet chuck is used to clamp the long-measure blank, it becomes necessary to machine the best part of its length with the aid of special devices, i.e. rests, which have no common base with the collet chuck (thus, the collet chuck of the machine tool is installed in the spindle whereas the rest is mounted on the frame) which affects adversely the machining accuracy. It also should be noted that the impossibility of tensioning the long-measure blank of the bar type likewises impairs the accuracy of machining. In addition, this calls for the use of special collets which brings about certain difficulties into the employment of the device as a whole.
Another known bar-clamping device (SU, A, 474402) comprises a spindle accommodating two collets with a single common collet-closing drive. The collets are rigidly coupled to each other.
However, this device fails to clamp the long bar with its simultaneous tensioning between the two collets since the latter are rigidly coupled to each other; as a result, accuracy and surface finish of the hole walls are impaired.
SUMMARY OF THE INVENTION
An object of the present invention resides in providing a design of a bar-clamping device which would allow making deep holes in bars, increase output, and improve the accuracy and surface finish of deep holes in the bars.
This object is achieved by providing a bar-clamping device comprising a hollow spindle accommodating coaxially-arranged first and second collets. According to the invention, each collet has a closing drive of its own ensuring independent axial motion of each collect with relation to the other one. The closing drives of each collet are installed in the spindle and designed so that the axial forces arising during the clamping of the bar are directed oppositely to each other.
It is practicable that the closing drive of the first collet would have the form of a sleeve with a nut installed on one end, said nut being locked against axial motion, the other end of the sleeve would fit around the extension of the first collet and be connected therewith by a screw joint; it is also practicable that the closing drive of the second collet would be made of two bushings. One of these bushings fits around the second collet and is secured rigidly on the internal surface of the spindle. One end of the second bushing would fit around the extension of the second collet and be connected with said extension by a screw join, and the second end of the second bushing should be provided with a nut ensuring axial motion of the second collet relative to the first collet and clamping of the bar with a certain tension.
The provision in the bar-clamping device of the closing drives for each collet and their construction ensure clamping of the bar and application thereto of tensile stresses which permits making deep and extra-deep holes in the bars at a high output, accuracy and surface finish of the hole walls.
Now the hereinproposed invention will be explained by way of example with reference to the appended sectional drawing of the bar-clamping device.
DETAILED DESCRIPTION OF THE INVENTION
The bar-clamping device according to the invention comprises a hollow spindle 1 accommodating two collets 2 and 3 coaxially-installed with a provision for independent motion and intended for clamping the bar 4, the first collet 2 being installed in the spind
REFERENCES:
patent: 3926447 (1975-12-01), Cox, Jr.
patent: 4736957 (1988-04-01), Bischopink
Tsangovye zazhimnye mekhanizmy, A. M. Dalsky, 1966.
Abdukarimov Erkin T.
Ismailov Lipilla
Vakhidov Khaidar A.
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