Chucks or sockets – Socket type – Obliquely guided reciprocating jaws
Patent
1996-03-13
1998-10-13
Bishop, Steven C.
Chucks or sockets
Socket type
Obliquely guided reciprocating jaws
279 60, 279902, B23B 31173
Patent
active
058201343
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention refers to a drill chuck for machine tools or to be more precise, to a system for opening, closing and attaching tools, such as twist drills, and which enables the tool to turn in both directions and which can be equipped with an internal refrigeration system.
STATE OF THE ART
The drill chucks are devices attached to both portable and automatic machine tools to clamp tools, such as twist drills of several diameters, and which must be able to transmit the cutting force and show the accuracy required in each application. The drill chucks can be used with portable machines, such as Do-It-Yourself (DIY) or industrial machines, and stationary machines which can be individual work stations or multi-tool machines, such as machining centres.
In the portable machines, the drill chucks closing mechanism can be activated manually or by using an auxiliary key. These drill chucks for portable machines are less accurate, with run-outs exceeding 0.2 mm. The drill chucks closing mechanism for stationary machines can be operated with a self-locking device or an auxiliary key. The accuracy of the self-locking drill chucks ranges from a run-out exceeding 0.1 mm, which is equivalent to low accuracy, up to 0.04 mm which is high. The drill chucks closed with an auxiliary key are used for medium and high quality work.
The systems currently known and used as high accuracy drill chucks, particularly for machining centres are the self-locking system auxiliary key clamping systems.
In the self-locking system, once the tool has been placed in its housing, it is manually attached by turning the outside of the drill chuck. As the direction in which the screw threads making up the attachment system are cut in a direction opposite to the drill chuck drive axis rotation, due to the drill chuck's actual resistance to rotate with regard to the tool, this means that, in operation, the drill chuck tightly closes the jaws that firmly support the tool while the task is carried out.
The disadvantage of this system is that, in operation, it can only be driven to rotate in one single direction, because if it were rotated in the opposite direction, the jaws would loosen and therefore not support nor clamp the tool firmly enough. Another disadvantage is the difficulty in loosening the tool when it has to be changed, because owing to the said induced clamping the drill chuck holds the tool very tightly, as a result of the self-locking system's actual design.
Furthermore, the design of the conventional self-locking drill chucks has an additional disadvantage which is the difficulty to attach them to a tool cooling system during operation.
A further disadvantage of conventional self-locking drill chucks is that when using high operating speeds, if the machine stops suddenly, for any reason, it may cause the drill chuck to loosen, thus running the risk that the tool may be dropped.
The other known system is the auxiliary key clamping device. Two recognised technologies are currently used in this system:
In the first, the auxiliary key acts upon a worm screw, which in turn rotates a toothed crown gear which, as it is internally threaded, advances or withdraws the drill chuck's internal screw. This advancing and withdrawing of the drill chuck's internal screw draws together or separates the jaws that clamp the tool, respectively.
In a system such as this, the clamping force is exercised on one or two of the worm gear teeth, which increases the risk of a worm breakage as a consequence of a high gear ratio between the worm and the number of teeth in the crown gear. Consequently, the auxiliary key has to be turned 60 and 90 times to achieve the maximum drill chuck jaw opening which is approximately 13 mm. In addition, as the worm screw has to be positioned externally tangent to the drill chuck, the latter remains dynamically unbalanced.
In the second case, instead of acting on the worm screw, the auxiliary key acts on a bevel gear which in turn transfers its rotary movement to a crown gear, which works as described in the pre
REFERENCES:
patent: 1750023 (1930-03-01), Prigan
patent: 1789601 (1931-01-01), Sjorgren
patent: 4260169 (1981-04-01), Hall
patent: 4902025 (1990-02-01), Zimdras
Bishop Steven C.
Llambrich Precision, S.A.
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