Drill bit equipped with a non-return valve

Abstract

A drill bit 1 has an elongated core 3 which is provided with a cylindrical part as well as a number elongated bits 5 which are connected to the cylindrical part of the core and extend in the longitudinal direction of the core. The core of the drill bit is hollow and is provided with a through hole which forms a channel 21 for drilling fluid to the bits 5. The drill bit 1 also has a non-return valve 23 which is present in the channel 21 and prevents used drilling fluid from flowing back. By building the non-return valve into the drill bit, it does not have to be separately installed. After the drilling operations have been completed, when using the known drill bit, the pipe together with the pipe section in which the non-return valve is present is removed from the borehole and the non-return valve is removed. By integrating the non-return valve into the drill bit, it does not have to be installed and removed separately.

Description

Technical field of the invention

[0001] The invention relates to a drill bit comprising an elongated core provided with a cylindrical portion and a number of elongated bits connected to the cylindrical portion of the core and extending in the longitudinal direction of the core, the core of the drill bit being hollow and provided with a through hole forming a channel for drilling fluid to the bits.Background of the invention

[0002] A drill bit according to the preamble of claim 1 is generally known. It is common practice to provide a non-return valve in a pipe section on which the drill bit is mounted to prevent used drilling fluid from flowing back into the supply line.Summary of the invention

[0003] An object of the invention is to provide a drill bit with which drilling can be carried out more economically than with the known drill bit. To this end, the drill bit according to the invention is characterised in that the drill bit comprises a non-return valve that is present in the channel and makes liquid flow through the channel in one direction impossible. By incorporating the non-return valve in the drill bit, no additional space is required for this and it does not have to be installed separately. After the drilling work has been completed, when using the known drill bit, the pipe together with the pipe section in which the non-return valve is present is removed from the borehole and the non-return valve is removed. By integrating the non-return valve in the drill bit, it does not have to be installed and removed separately. In addition, the non-return valve together with the drill bit can remain at the bottom of the borehole after the drilling work so that it does not have to be removed afterwards. This saves work.

[0004] An embodiment of the drill bit according to the invention is characterised in that the non-return valve is provided with a valve member and a coil spring that presses the valve member against a valve seat.

[0005] A further embodiment of the drill bit according to the invention is characterised in that the core is provided with a number of elongated bit holders and the bits are detachably connected to the bit holders, the bit holders being formed by elongated mounting surfaces extending in the longitudinal direction of the core and being present on the outside of the cylindrical portion of the elongated core and the mounting surfaces each comprising at least one flat portion being present on the outside of the cylindrical portion of the core, each of the flat portions of the mounting surfaces, viewed in cross-section of the cylindrical portion of the core, being at an angle not equal to 90 degrees to an imaginary line perpendicular to and through the centre line of the core and through the centre of the flat portion of the mounting surface in question.

[0006] The orientation of the cutting edges of the bits is determined by the position of the mounting surfaces, the shape of the bits being straight forward. The mounting surfaces are milled into the core at a certain angle so that the bits are correctly oriented with respect to the centre line of the core after mounting on the core. The bits that need to be replaced regularly can therefore be made geometrically simpler and therefore cheaper than those of the known drill bit.

[0007] It should be noted that the above-described embodiment of the drill bit in which the bits are detachably connected to the core can also be used advantageously with a drill bit that is not equipped with a non-return valve.

[0008] From CN218376338U a drill bit is known that is provided with mounting surfaces that -seen in cross-section- extend perpendicular to a line through the centre line of the core, with the cutting edges of the bits at an angle to this line. In order to obtain a correct position of the cutting edges of the bits in relation to the core, the bits should not be formed straight forward but in a specific way, whereby high demands must be made on the shape accuracy of the bits.Brief description of the drawings

[0009] The invention will be explained in more detail below using an exemplary embodiment of the drill bit according to the invention shown in the drawings. In the drawings: Figure 1 shows an embodiment of the drill bit according to the invention in perspective; Figure 2 shows the drill bit shown in figure 1 in longitudinal section; Figure 3 shows one of the bits of the drill bit shown in figure 1 provided with cutting blocks and bolts; Figure 4 shows the drill bit shown in figure 3 without cutting blocks and bolts; Figure 5 shows the core of the drill bit shown in figure 1; Figure 6 shows the core shown in figure 5 without non-return valve in longitudinal section; and Figure 7 shows the drill bit shown in Figure 1 in cross-section. Detailed description of the drawings

[0010] Figures 1 and 2 show an embodiment of the drill bit according to the invention in perspective and longitudinal section respectively. The drill bit 1 has an elongated core 3 and a number of elongated bits 5 which extend in the longitudinal direction of the core 3 and are detachably attached to the core 3. To this end, the core 3 is provided with a number of elongated bit holders 7 which are formed by elongated mounting surfaces 9 which extend in the longitudinal direction of the core 3 and which are present on the outside 3a of the core 3, as well as a number of internally threaded holes 11 which are present in the core 3 at the location of the mounting surfaces 9.

[0011] The core 3 of the drill bit 21 is hollow and is provided with a through hole which forms a channel 21 for drilling fluid to the bits 5. In the channel 21 there is a non-return valve 23 to prevent used drilling fluid from flowing back into the drilling fluid supply line. This non-return valve 23 is provided with a valve member 25 which is pressed against a valve seat 29 by a coil spring 27.

[0012] In figures 5 and 6 these mounting surfaces 9 and holes 11 in the core 3 are clearly visible. The mounting surfaces 9 are at an angle not equal to 90 degrees with respect to an imaginary line which is perpendicular to the centre line 21 of the core and passes through the core 3.

[0013] The bits 5 are provided with holes 13 through which bolts 15 are inserted which are turned into the holes 11. In figure 3 a bit is shown provided with bolts which are inserted through the holes. Each bit 5 is provided with a number of cutting blocks 19, see figure 3, which are accommodated in cutting block holders 17 which are formed by recesses in the bit 5. The cutting blocks 19 in this embodiment are designed as cylinders with a round cross-section but can also have another shape such as cylinders with a quadrangular cross-section, for example a diamond shape. In figure 4 the bit 5 is shown without cutting blocks 19 and without bolts through the holes 11.

[0014] To clarify the orientation of the mounting surfaces 9 of the bit holders the drill bit 1 is shown in cross-section in figure 7. The mounting surfaces 9 each have a flat section (i.e. not curved) that is present on the outside 3a of the cylindrical section of the core 3. Each of these flat sections, viewed in cross-section of the cylindrical section of the core 3, is at an angle 10 not equal to 90 degrees relative to an imaginary line 12 perpendicular to the centre line 18 of the core and through the centre line of the core 3 and through the centre of the flat section of the mounting surface 9 in question.

[0015] Although the invention has been explained above with reference to the drawings, it should be noted that the invention is by no means limited to the embodiment shown in the drawings. The invention also extends to all embodiments deviating from the embodiment shown in the drawings within the framework defined by the claims.

Claims

1. Drill bit (1) comprising an elongated core (3) provided with a cylindrical portion and a number of elongated bits (5) connected to the cylindrical portion of the core (3) and extending in the longitudinal direction of the core (3), the core (3) of the drill bit (1) being hollow and provided with a through hole forming a channel (21) for drilling fluid to the bits (5), characterised in that the drill bit (1) comprises a non-return valve (23) present in the channel (21) and making fluid flow through the channel (21) in one direction impossible.

2. Drill bit according to claim 1, characterised in that the non-return valve (23) is provided with a valve member (25) and a coil spring (27) pressing the valve member (25) against a valve seat (29).

3. Drill bit according to claim 1 or 2, characterised in that the core (3) is provided with a number of elongated bit holders (7) and the bits (5) are detachably connected to the bit holders (7), the bit holders (7) being formed by elongated mounting surfaces (9) extending in the longitudinal direction of the core (3) and being present on the outside (3a) of the cylindrical portion of the elongated core (3) and the mounting surfaces (9) each comprising at least one flat portion being present on the outside (3a) of the cylindrical portion of the core (3), each of the flat portions of the mounting surfaces (9) being at an angle (10) not equal to 90 degrees, viewed in cross-section of the cylindrical portion of the core (3), to an imaginary line (12) perpendicular to and through the centre line (18) of the core (3) and through the centre of the flat part of the mounting surface in question (9).

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