Screwdriver bit

Abstract

The invention relates to a screwdriver bit with a shaft 1 at its first end region, which has a specific cross-sectional profile, and with a screw head 5 at its second end region opposite the first end region. The shaft 1 has at least one pair of diametrically opposed, radially outward openings in which compensating elements are arranged. These compensating elements are subjected to a spring force radially outward and can project radially outward from the openings to a specific extent, as well as be fully retractable radially inward into the openings.

Description

The invention relates to a screw bit with a shank at its first end region, which has a specific profile in cross section, and with a screw head at its second end region opposite the first end region.In the case of such helical bits for screwing screws around their longitudinal axis into a threaded bore of a workpiece, the helical bit is inserted axially into a coaxial receiving recess of a bit holder of the same cross section as the shank with its shank and can be driven in a machine-rotatable manner by a drive. The bit holder and its motor drive are arranged on a fixed machine frame. Due to manufacturing tolerances and the play between the shank of the working bit and the receiving recess of the bit holder and the screw to be screwed, deviations in the coaxiality of the screw bit and screws frequently occur. This can lead to incorrect placement of the screw head on the head of the screw to be screwed in.Usually, the shank is provided with a hexagonal cross section. However, other cross sections can also be used.It is therefore an object of the invention to provide a screw bit of the type mentioned at the beginning which eliminates these disadvantages and feeds the screw bit coaxially to the screw to be screwed in.This object is achieved according to the invention in that at least one pair of diametrically opposite openings opening radially outwards are formed on the shaft, in which openings compensating elements are arranged which act radially outwards by a spring force and can be projected radially out of the openings by a certain amount and can be inserted completely radially inwards into the openings.Due to the embodiment according to the invention, the screw bit can be displaced transversely to its longitudinal axis and can move into a position coaxial to the screw axis. Thus, the coaxial deviations of the screw bit and screw are eliminated.The shaft can consist of two shaft sections which are connected to one another by a radially encircling depression.The openings in the shaft can be blind openings, preferably bores with a circular cross section, for easy manufacture.The compensating elements can be balls at low cost as finished parts.The spring force can likewise be generated in a cost-effective manner by a prestressed compression spring which is supported at one end on a support in the opening and acts on the compensating element with the spring force at the other end.For easy and positionally accurate arrangement of the compensating elements in the openings, the compensating elements can be arranged in a cylindrical cage which is inserted into the opening and is open at its radially outwardly directed end and has a base at its inwardly projecting end.For precisely limiting the radial outward path of the compensating elements from the shaft, the cage can have at its outwardly directed end one or more radially inwardly projecting stop elements, by means of which the outward path of the compensating element is limited radially outwardly.The shank preferably has a uniform hexagonal profile in cross section.Two or more pairs of diametrically opposite openings opening radially outwards can be formed in the shaft with an axial distance from one another, in which openings compensating elements are arranged.Tilting transversely to the longitudinal axis of the display bit can be avoided by forming in the shaft, at an axial distance from one another, two or more pairs of diametrically opposite openings which open radially outwards and in which compensating elements are arranged.If the diametrically opposite openings for the compensating elements are aligned radially on the longitudinal axis of the helical bit, the compensating elements simultaneously perform a centering function for the helical bit.Exemplary embodiments of the invention are illustrated in the drawings and are described in more detail below. The following are shown: FIG. 1 shows a first exemplary embodiment of a helical bit in side view FIG. 2 is a cross-section through the screw bit according to FIG. 1 in the region of diametrically opposite radial openings FIG. 3 shows a second exemplary embodiment of a helical bit in side view FIG. 4 is a longitudinal sectional view of a cylindrical cage.The helical bits shown consist of a shank 1, which is divided in its first end section into a first shank section 2 and a second shank section 3 by a radially encircling depression 4.At its second end section, the screw bit has a screw head 5 for insertion into a cross slot of a screw, not shown.The shank 1 has a hexagonal cross section.In the exemplary embodiment of FIG. 1, both in the first shank portion 2 and in the second shank portion 3 there are respectively a pair of diametrically opposite radial bores 6 designed as base bores.In the exemplary embodiment of FIG. 2, two pairs of diametrically opposite bores 6, which are designed as base bores, are provided on the second shank portion 3 at an axial distance from one another.It is understood that such pairs of bores 6 can also be formed on further longitudinal sides of the shank 1.The center lines of the two bores 6 of each pair intersect at right angles the longitudinal axis of the shank 1.FIG. 4 shows a cylindrical cage 7 made of sheet metal which is of pot-like design. At its one end, the cage 7 has a bottom 8 with a through bore 9. Its other end has a mouth 12.Inserted into the cage 7 is a ball 11 having a diameter approximately equal to the inner diameter of the cage 7.A prestressed compression spring 10, which is designed as a helical compression spring and is supported at one end on the ground, and at its other end acts upon the ball 11 toward the orifice opening 12, is arranged in the cage 7.In order that the ball 11 can only emerge from the cage by a specific escape path 13, the mouth edge of the cage 7 is crimped radially inward and forms a stop element 14.Such an entire unit, which can be produced separately and is composed of the cage 7, the compression spring 10 and the ball 11, can be inserted into each of the bores 6 in such a way that only the ball 11 can project out of the bore by at most the outward-contact path 13.If the bit with its shank 1 is inserted axially into a receiving recess of the same cross section as the shank of a stationary and rotatably drivable bit holder, tolerance-related deviations of the longitudinal axis of the bit holder from the longitudinal axis 15 of the bit and of the screw to be screwed can thus be compensated for in the direction of coaxiality of these longitudinal axes. The balls 11 thereby enter the cages 7 to a greater or lesser depth.Reference numerals denote reference numerals1 Shank 2 First shank portion 3 Second shank portion 4 Depression 5 Screw head 6 Radial bores 7 Cage 8 Base 9 Through bore 10 Compression spring 11 Ball 12 Orifice opening 13 Outlet path 14 Stop element 15 Longitudinal axis

Claims

A threaded bit having a shank (1) at its first end region, which has a specific profile in cross section, and having a threaded head (5) at its second end region opposite the first end region, characterized in that at least one pair of diametrically opposite, radially outwardly opening openings are formed on the shank (1), compensating elements being arranged in said openings, which are acted upon radially outwardly by a spring force and can be radially extended from the openings by a specific amount and can be completely inserted radially inwardly into the openings.The screw bit according to claim 1, characterized in that the shank (1) consists of two shank sections (2, 3) which are connected to one another by a radially encircling depression (4).The bit according to any one of the preceding claims, characterized in that the openings are blind openings.The screw bit according to any one of the preceding claims, characterized in that the openings are bores (6) with a circular cross section.The screw bit according to claim 4, characterized in that the compensating elements are balls (11).The screw bit according to any one of the preceding claims, characterized in that the spring force is generated by a prestressed compression spring (10), which is supported with one end on a support in the opening and acts with the spring force on the compensating element with the other end.The bolt bit according to any one of the preceding claims, characterized in that the compensating elements are arranged in a cylindrical cage (7) which is inserted into the opening and is open at its radially outwardly directed end and has a base (8) at its inwardly projecting end.The screw bit according to claim 7, characterized in that the cage (7) has stop elements (14) which project radially inward at its outwardly directed end and by means of which the escape path (13) of the compensating element is bounded radially outward.The screw bit according to any one of the preceding claims, characterized in that the shank (1) has a uniform hexagonal profile in cross section.The bolt bit according to any one of the preceding claims, characterized in that two or more pairs of diametrically opposite openings opening radially outwards are formed in the shank (1) with axial spacing from one another, in which openings compensating elements are arranged.A helical bit according to any one of the preceding claims, characterised in that the diametrically opposite openings for the compensating elements are aligned radially with the longitudinal axis (15) of the helical bit.

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