HK1007291B - Tool chuck for equipment of a rotating machine like a drilling machine - Google Patents

Description

The present invention concerns a tool-holding chuck for the equipment of a rotary machine such as a drill, or a screwdriver, including the characteristics of the preamble to claim 1 (see EP-A-0 300 375).

The first possibility to fix the cylindrical tail of a tool to the chuck is to equip it with a rack system, ensuring with a key the tightening of the strings on the tool, before using the machine. The rack ensures the drive in rotation relative to the body of a board surrounding it, on the inner side of which a thread is fixed, the internal threading of which cooperates with the external threading of the strings.Although this solution is practical, it has the disadvantage of requiring the use of a key which is often lost by the user. This use of a key is all the more restrictive in so-called wireless drills, i.e. which are powered by batteries which are an integral part of the machine body, giving them very high mobility. These machines or wireless drills are usually equipped with keyed mandrels for holding tools.There are no key-operated cylinders that can tighten the tool satisfactorily.

A first known solution is to have several teeth, a ring mounted concentrically on the body, at the back end of the training shirt in rotation of the nut actuating the bit, held axially apart from the shirt by a spring with at least one tooth in relation to the shirt. This ring is mounted freely in rotation around the body. In practice to achieve tool tightening or loosening, the user should grab the ring and move it forward, so that the teeth of the ring come into contact with the teeth of the shirt body, while commanding the same series of rotation of the chuck, from the bit breaker, in one direction or another.

In another known mandrel, the shirt has a radial collar shape at its front end, with several backward-facing crests protruding from it, and a ring with forward-facing crests is forcibly attached to the nut that drives the strings.

A spring that rests on the body of the chuck holds the ends of the ring and the shirt together until a certain amount of force is achieved.

In practice, the user simply manually locks the belt in a rotating position and operates the drive shaft in one direction or another to tighten or loosen the strings, resulting in a series of shocks by the ring heads against the belt heads, which facilitate tightening or loosening, as appropriate.

However, these two well-known cylinders have a complex structure which leads to a high cost and a very large volume.

Another solution is provided in EP-A-0 300 375 which concerns a chuck using a very thin step for the strings, and a series of balls arranged between the nut and the body, the latter characteristic being the interposition of balls between the nut and the body being already known in industrial chucks.

The disadvantages of cylinders with an inner ball-stop are that they cannot be used in left-hand rotation, that a central screw for locking the cylinder on the spindle of the machine cannot pass through, and that they loosen during heavy vibration during percussion work.

The present invention is intended to remedy these disadvantages by means of a mandrel of the type concerned, comprising a body fixed on the drive shaft of the machine, in which several forward-converging, sliding, wedges are mounted, and a hood encircling the body and swiveling around it, these wedges having an outer threaded part in contact with a nut encircling the wedges and in conjunction with the shirt encircling the body, a series of balls being interposed between the face of the screw facing backwards and the mandrel, the balls being in support, on the opposite side of the body to the screw, a ring made of a hard material, such as steel, which is characterized by the fact that the ring serves as a support against the balls and is itself blocked against the balls, and has a synthetic ring against the body, which is characterized by a ring against the balls.

The balls make it easier to tighten the chuck to a locking state satisfactory for the tool's biting, without any outside assistance, while the synthetic ring prevents accidental loosening of the tool during drilling or percussion operations.

In accordance with a feature of an embodiment of the invention, the ring against which the balls are supported is made of steel.

In accordance with another form of execution, the ring between the hard ring and the body is made of a polyamide 6-6 known as ZYTEL ST.

The body has a peripheral cover which is used as a housing for the series of balls, the ring made of a hard material and the ring made of synthetic material, respectively. This cover is open to the outside and the various elements housed in it are held in place by a shirt which surrounds and is solid with the body.

In addition to the simplicity of the construction of this chuck, this solution allows the user to move the chuck more easily by moulding or grooving the chuck and the nut's solid coat.

In addition, the chuck has an axially oriented sheath, which is placed in contact with the balls, on the side of the balls, radially towards the inside of the body, to prevent the balls from entering the housing.

In accordance with an advantageous characteristic, the thread rate of the nut and the bolts is on the order of 1 to 1.50. This is a rate which is not too fine, i.e. which does not require a number of turns too large to perform the functions of tightening and loosening a tool, but which is sufficiently small to allow easy manual tightening.

Another way of making the chuck is to place a ring made of a hard material, such as steel, between the balls and the nut, which holds the balls in place during assembly operations and helps the chuck to function properly because its surface condition is better than that of the nut.

In any case, one embodiment of the invention will be clearly understood by the following description in reference to the accompanying schematic drawing, the unique figure of which is a longitudinal cut-out view of this chuck.

The chuck shown in the figure consists of a body 2 with an axial bore 3 at one end of which a tail 4 is spared to allow the attachment to the threaded drive shaft of a machine not shown in the figure. As shown, the axial bore 3 has a narrowed central part, allowing the engagement of an unrepresented screw, to ensure the lock of the chuck on the machine shaft, to prevent its loosening when the drive shaft is driven in a direction resulting in an automatic loosening of the chuck.

The body has three 5 wedges, angularly offset by 120° from each other, inclined from the outside inwards and from the end of the chuck containing the tailed part 4 towards the other end of the chuck. The 5 wedges also open to this other end to allow for possible displacement of the strands 6. Each 6 wedge has, in its rear part, an outer 7 threaded area which is in contact with a nut 8 itself surrounded externally by a 9 threaded on this nut.

In accordance with the essential feature of the invention, three types of elements are stacked between nut 8 and body 2. These are first steel balls 10 resting on the nut 8 on one side and on a steel ring 12 parallel to the nut on the other side, the ring being itself supported by a synthetic ring plated against the body 2. This ring 13 is advantageously made of polyamide 6-6, type ZYTEL ST. This is a material which has excellent damping characteristics, while maintaining sufficient durability, the notion of hardness being important to allow good external handling characteristics during the maneuver. For example, in the case of the 12 and 13 series, the three elements are mounted on an open surface, which facilitates the handling of the same body.

As shown in the figure, a steel ring 16 is placed between nut 8 and balls 10 and a sheath 17 is placed between balls 10 and body 2 on the side of the balls facing radially inwards.

The operation of this chuck is as follows: To tighten a tool such as a drill, the user immobilizes the hammer 15 with one hand while turning the hammer 9 which is in solidarity with the nut 8 with the other hand. When the hammers 6 are in contact with the tool, the lock of the chuck is achieved by the force applied by the user to turn the hammer 8.

To loosen the chuck and to de-solidify the tool, the user rotates the shirt 9 in the opposite direction.

As shown above, the invention greatly improves the existing technique by providing a simple-designed chuck which has excellent tool-tightness without the use of a key and which does not loosen in use.

The invention is not limited to the only embodiment of this chuck described above as an example, for example, the nature of the materials of rings 12 and 13 may be different, or the structure of the gap 14 receiving elements 10, 12 and 13 may be different.

Claims (6)

1. Tool holding chuck for fitting to a revolving machine such as a drill, of a type consisting of a body (2) fixed on the drive shaft of the machine on which are mounted several clamping jaws (6) sliding in the bores and converging towards the front and a jacket (9) surrounding the body and pivoting around the latter, these clamping jaws including an external part with a screw thread engaging with a nut (8) surrounding the clamping jaws and solidly joined to the jacket (9) surrounding the body, a series of ball bearings (10) which are interposed between the face of the nut which is turned towards the rear and the body of the chuck with the ball-bearings (10) being supported, on the side opposite to the nut, against a collar (12) made out of a hard material such as steel, characterised in that the collar (12) which serves to support the ball-bearings is itself supported against a collar (13) made of a synthetic material with damping characteristics and locked tight against the body.
2. Chuck according to Claim 1, characterised in that the collar (13) interposed between the collar (12) made of a hard material and the body (2) is made out of a 6-6 polyamide.
3. Chuck according to one of the Claims 1 and 2, characterised in that the body (2) includes a peripheral groove (14) serving for housing respectively the series of ball-bearings (10), the collar (12) made out of a hard material and the collar (13) made out of a synthetic material, this groove opening outwards and the different elements which are housed there being held there by a jacket (15) which surrounds the body and is firmly joined to it.
4. Chuck according to one of the Claims 1 to 3, characterised in that the pitch of the thread on the nut (8) and the clamping jaws (6) is of the order of 1 to 1.50.
5. Chuck according to one of the Claims 1 to 4, characterised in that a collar (16) made out of a hard material such as steel is interposed between the ball-bearings (10) and the nut (8).
6. Chuck according to one of the Claims 1 to 5, characterised in that it includes a sleeve (17) positioned axially and arranged in contact with the ball-bearings (10) on that side of the latter which is situated radially towards the interior of the body.