DE3921874A1 - Screw with a countersunk recess in the head, a right-handed and a left-handed thread being located on the inner wall of said recess. Screwdriver with complementary threads on the outer border of the part which is screwed into the countersunk recess in order to screw in, and unscrew, the screw - Google Patents

Abstract

The screw head or the shank end of the screw connection has a countersunk recess (2), two internal threads which run one above the other, a right-handed and a left-handed thread, being provided (3) on the inner border of said recess. On the outer border of the part which is screwed into the countersunk recess, the screwdriver likewise has right-handed and left-handed threads running one above the other (Figure 2). They are complementary to the internal threads of the countersunk recess. In order to screw in the screw or the screw connection, this part of the screwdriver is screwed into the countersunk recess corresponding to the direction of the external thread of the screw or of the screw connection. If the end of the countersunk recess is reached, the screw or the screw connection can be screwed into the workpiece. If the screwing procedure has been completed, the screwdriver can be unscrewed in the opposite direction. Unscrewing the screw or the screw connection takes place in a similar manner, but in opposite directions of rotation in each case. <IMAGE>

Description

A screw or a screw connection essentially serves to be releasable or make non-detachable connections. When connecting is the screw or the screw connection using a Screwing tool turned in and when loosening with the help of a turning tool turned out. Screwing and unscrewing tools are mostly identical.

Both when screwing in and out, are the screw and that Turning tool usually not tight with the usual screws and tools connected with each other. Thus, it is not possible to remove the screw without one additional auxiliary instrument, in the simplest case the fingers of the human Hand to the point where it should be screwed in. In addition comes that screw and turning tool when screwing in not for difficult Applications ensure accurate axial connection necessary. For example, a self-tapping screw leave the desired screwing angle: the Screw will be crooked. Due to the lack of axial connection of The screw and screwing tool cannot do the force necessary for screwing in more fully transferred to the screw and that for screwing in and out necessary radial pressure can not be implemented. In addition, a not firm connection between screw and turning tool cause the latter with strong rotational pressure from the usually in the screw head existing longitudinal or cross slot pops out. That usually leads to damaged screw heads and damaged turning tools. Will be at Screwing the hand used to the axial connection of screw and To bring the turning tool, the turning tool can jump out Hurt hand.

With self-tapping screws, e.g. a wood screw, the missing one firm connection cause the screw through the material structure or is distracted due to insufficient pre-drilling. By the when screwing in  used pressure can then bend the screw and the surface of the Damage the workpiece.

It is often without a fixed connection between screw and turning tool difficult to insert a screw in the place where it to be screwed in. This is e.g. then the case when the position in Workpiece is recessed or the screw is not from top to bottom, but must be inclined or even brought up to the point from bottom to top. Likewise, it is often difficult to get a loosened screw without a tight connection pull it out of a recess between it and the turning tool.

The invention is based, screw and on and the task Boring tool or two or more to be connected screw connections firmly, but still releasably together connect.

This object is achieved in that the screw in the head or the screw connection in the shaft end on the inner edge of a countersink recess two overlapping internal threads, one right and one Left-hand thread, and the screwing and unscrewing tool (e.g. a screwdriver) on Outer edge of the part that fits into the countersunk recess of the screw or Screw connection should be screwed in, two the internal threads of the screw or the screw connection has corresponding external threads.

The advantages achieved by the invention are in particular that

• - screw and turning tool or two or more Screw connections with each other during the screwing process are connected, exactly axially;
• - Neither screw, nor turning tool, nor screw connection during the screwing process can break out of the axial connection and there is no damage;
• - Screw or screw connection slightly in the place where it to be screwed in, brought in and fixed there can;  
• - Screw or screw connection easily from recesses removed and easily from each screw hole with the help of Turning tool can be removed without the risk exists that it falls out and is lost or thereby damaged wreaks;
• - Screw in and unscrew the screw using the same turning tool can be carried out.

In the following the invention using an exemplary embodiment in Connection explained in more detail with the accompanying drawing.

Fig. 1 shows a section through the head of a cap screw.

In accordance with the claim, the head ( 1 ) has a countersink recess ( 2 ). There is a right-hand and a left-hand thread ( 3 ) on the inner wall of the countersink recess.

Fig. 2 shows the side view of the part of a turning tool which relates to the invention. On the outer wall of the part that is to be screwed into the countersunk recess of the screw or screw connection, there are right-hand and left-hand threads complementary to the internal threads of the countersunk recess.

In a screw designed in this way, the turning tool for screwing the screw in according to the direction of the external thread of the screw - right or left - is screwed into the internal thread of the screw. As soon as the end of the internal thread is reached, the axial connection is established. The screw can now be brought to the point on the workpiece intended for screwing in and screwed in. After the screw has been screwed in, the turning tool can be unscrewed again in the opposite direction; the screw remains firmly in the workpiece.

To unscrew the screw, the lathe tool is screwed into the external thread Screw in the opposite direction into the counterbore. As soon as the end of the internal thread is reached, the screw can be loosened and removed  with every point in the workpiece where the screw is located be removed from the turning tool.

Claims (2)

1. screw or screw connection provided in the head or in the shaft end recess for receiving a screwing and unscrewing tool, characterized in that the countersink on the inner edge has two overlapping internal threads, namely a right-hand and a left-hand thread. 2. Screwing and unscrewing tool according to claim 1, characterized in that the Part that rotated into the countersunk recess of the screw or screw connection is, on the outer edge two that of the internal thread of the counterbore corresponding external threads, namely a right-hand and a left-hand thread, having.