Drill chuck with position indicator

A drill chuck has a chuck body centered on and rotatable about an axis and formed with a plurality of guides angularly equispaced about the axis, respective jaw displaceable axially in the guides, an adjustment body rotatable about the axis on the body, and screwthreads coupling the adjustment body with the jaws for axial forward movement of the jaws on the body on rotation of the adjustment body on the chuck body in one direction and opposite axial backward movement on opposite relative rotation of the bodies. An indicator element is provided between the chuck and adjustment bodies. A screwthread coupling centered on the axis is provided between the element and one of the bodies and a translatory coupling is provided between the element and the other of the bodies. Thus the indicator element moves in a straight line relative to the other body on relative rotation of the bodies.

FIELD OF THE INVENTION 
The present invention relates to a drill chuck. More particularly this 
invention concerns such a chuck provided with an indicator that shows what 
position the chuck is in. 
BACKGROUND OF THE INVENTION 
A standard drill chuck that is rotated about an axis of a drill spindle to 
rotate a drill bit about the axis has a chuck body secured to the spindle 
and formed centered on the axis with a screwthread. An adjustment sleeve 
rotatable but axially nondisplaceable on the chuck body is formed 
angularly equispaced about the axis with a plurality of angled jaw guides. 
Alternatively it is possible to form the guides on the chuck body and the 
screwthread on the sleeve for the same effect. Respective jaws in the 
guides have racks that mesh with the screwthread so that rotation of the 
sleeve body on the chuck body about the axis in a tightening direction 
moves the jaws radially together and opposite rotation in a loosening 
direction moves the jaws radially apart. 
It is known from German patent document 3,809,316 to form a window in the 
sleeve and to provide one of the jaws with an indicator or pointer that is 
visible through this window so that the user can see the position the 
chuck is in. The pointer can move relative to a scale indicating the 
diameter of the drill bit held in the chuck. 
Such an arrangement can only be used in a particularly constructed chuck, 
that is the chuck must be of nonstandard construction to carry the 
necessary indicator which may be formed as a spreadable ring engaged 
around the rear ends of all the jaws. In addition this type of arrangement 
is not readily adaptable to a remote position reader or detector. 
OBJECTS OF THE INVENTION 
It is therefore an object of the present invention to provide an improved 
drill chuck with a jaw-position indicator. 
Another object is the provision of such an improved drill chuck with a 
jaw-position indicator which overcomes the above-given disadvantages, that 
is which can be used on a chuck which is otherwise of standard 
construction and that can be interfaced readily with a remote position 
reader or detector. 
SUMMARY OF THE INVENTION 
A drill chuck according to the invention has a chuck body centered on and 
rotatable about an axis and formed with a plurality of guides angularly 
equispaced about the axis, an adjustment body rotatable about the axis on 
the body, respective jaw displaceable axially between the bodies in guides 
formed in one of the bodies, and screwthreads coupling the adjustment body 
with the jaws for axial forward movement of the jaws on rotation of the 
adjustment body on the chuck body in one direction and opposite axial 
backward movement on opposite relative rotation of the bodies. An 
indicator element is provided between the chuck and adjustment bodies. A 
screwthread coupling centered on the axis is provided between the element 
and one of the bodies and a translatory coupling is provided between the 
element and the other of the bodies for movement transverse of the 
screwthreads of the screwthread coupling. Thus the indicator element moves 
in a straight line relative to the other body on relative rotation of the 
bodies. 
With this system as the chuck body and adjustment body are rotated relative 
to each other to adjust the positions of the jaws, the indicator element 
moves along its translatory coupling. The position of the indicator 
element will therefore be directly related to that of the chuck jaws. 
Since the indicator is not carried on the jaws it is relatively easy to 
connect it with some sort of remote reading device to provide remote 
detection of the jaw position. 
According to the invention the screwthread formations include teeth on the 
jaws and a screwthread on the adjustment body and the indicator includes a 
sensible part on the indicator element. A sensing element fixed adjacent 
the chuck and juxtaposed with the sensible part for detecting the position 
of same. The part can be a ferrite or magnetic plug and the sensing 
element can be a coil. 
Furthermore according to the invention the screwthread coupling is an 
internal screwthread on the adjustment body and an external screwthread on 
the indicator element meshing with the screwthread of the adjustment body. 
The translatory coupling is an axially effective slide joint between the 
chuck body and the indicator element. In this case the element is a ring 
engaged around the chuck body within the adjustment body, the adjustment 
body being a sleeve. 
It is also possible in accordance with the invention for the screwthread 
coupling to be a screwthread on the chuck body and a screwthread on the 
indicator element meshing with the screwthread of the chuck body. Here the 
adjustment body is a sleeve coaxially surrounding the chuck body and the 
indicator element and the translatory coupling is formed by an axially 
extending slot formed in the sleeve and a radial projection of the 
indicator element engaged in the slot. 
In yet another system of this invention the chuck body has an axially 
directed rear end face and the screwthread coupling is a spiral 
screwthread formed on the rear face and engaging the indicator element. 
The translatory coupling is a radially extending slot formed in the 
adjustment body and slidably receiving the indicator element.

SPECIFIC DESCRIPTION 
As seen in FIGS. 1A and 1B a chuck A according to this invention is carried 
on a drill B having a drive shaft B1 carried in a bearing B2 in a nose B3 
of the drill B. The chuck A has a chuck body 1 threaded on the front end 
of the shaft B1 for rotation about an axis 4 of the shaft B1. In addition 
this chuck A is formed with three angularly equispaced guide holes 5 
extending along respective axes inclined to the axis 4 and receiving 
respective jaws 3 (the section of FIG. 1A being taken along a plane that 
is inflected at the axis 4 to run centrally through two jaws 3) that are 
mainly of circular section but that have outer edges formed with rows of 
teeth 8. 
A tightening sleeve 2 can rotate on the chuck body 1 but not move axially 
thereon. It is formed as a sheet-metal tube 2.1 that has a front end 
provided with a split ring 2.2 that is internally formed with a 
frustoconical screwthread 6 that meshes with the teeth 8 of the jaws 3 to 
moved them axially forward and radially together when rotated in one 
direction and axially backward and radially apart when oppositely rotated. 
The jaws 5 can be exposed at their rear ends at a space 10 into which the 
rear ends of the guide holes 5 open. This construction is all standard. 
According to this invention the rear part of the sleeve 2 carries a ring 13 
that rotates with it. The chuck body 1 carries a position-indicating 
element 7 formed as a ring having at its front edge a seal lip 14 that 
rides on the inside surface of the sleeve 2.1. This element 7 is connected 
to the body 1 via a coupling 12 that is formed as an axially extending and 
radially outwardly open groove in the body 1 and a radially inwardly 
projecting pin on the ring 7 that serves to rotationally couple the body 1 
to the element 7 while permitting these parts to move axially relative to 
each other. In addition a screwthread coupling 11 constituted as an 
external thread on the element 7 and an internal thread on the ring 13 is 
provided between the parts 7 and 13. Thus as the sleeve 2 is rotated on 
the body 1 the element 7 will move axially in one direction or the other. 
The indicating ring 7 carries a ferrite ring 16 and the nose B3 of the 
drill B carries a sensing coil 17 connected to a control and display 
indicated schematically at D in FIG. B. The coil 17 can therefore detect 
the axial position of the element 16 and thereby provide at D a readout of 
the position of the jaws 3. 
FIGS. 2A and 2B shows an arrangement where a ring 7a is formed with holes 
15 aligned with the guide holes 5 for the jaws 3 so that same can poke 
back through this ring 7a when fully retracted as shown in FIG. 2B. This 
arrangement is characterized by being particularly short axially. 
In FIGS. 3A and 3B a ring 7b is secured by the screwthread coupling 11 to 
the chuck body 1 and the sleeve is formed with a slot 18 forming with 
radial extensions of the ring 7b the translatory coupling 12. Thus as the 
chuck body 1 and sleeve 2 are relatively rotated about the axis 4 the ring 
7 will be screwed axially along in the chuck. 
FIGS. 4A, 4B, and 5 show yet another arrangement where a 
position-indicating ring element 9 taking the place of the ring 7, 7a, or 
7b can move radially in a slot 22 formed in a rear wall 20 of the sleeve 2 
and forming therefore the rotational coupling 12. The rear end of the 
chuck body 1 is formed with a spiral screwthread 21 meshing with teeth on 
the front face of the element 9 and forming therewith the screwthread 
coupling 12. Thus as the sleeve 2 and body 1 rotate relative to each other 
the element 9 will move radially in the slot 22 and its radial position 
will indicate the positions of the jaws 3.