Dresser feeding device

This is a U.S. national phase application under 35 U.S.C. § 371 of International Patent Application No. PCT/JP2006/303309 filed Feb. 23, 2006 which is incorporated by reference herein. The International application was published in Japanese on Aug. 30, 2007 as WO 2007/096973 A1 under PCT Article 21(2).

The present invention relates to a dresser supply device which supplies dresser to a grinding tool such as a core drill which has an abrasive grain layer as a cutting blade tips.

A grinding tool, such as a core drill which has an abrasive grain layer as a cutting blade tips on the tip of a cylindrical drill body is used for drilling a wall or the like of an existing concrete structure. The abrasive grain layer is constructed of combined diamond abrasive grains by a binder. In the drilling by this core drill, the drill body is advanced while being rotated around its cylindrical central axis and is made to cut into a concrete structure. Thereby, a rebar or the like in the structure is cut while digging up the concrete by the grinding action by the abrasive grains of the cutting blade tips. After that, the hole is opened to concrete or the like.

In the drilling by such a core drill, conventionally, drilling is performed while cooling water is supplied to the cutting blade tips for the purpose of removing chips generated by grinding or cooling the cutting blade tips. However, the supplied cooling water is discharged as muddy water including the chips. Consequently, there is a possibility of polluting the surrounding environments. For this reason, in recent years, the drilling by a dry construction method, which supplies compressed air to perform chip removal and cooling, and collects dust of the discharged chips by a dust collector instead of a wet construction method using such cooling water is being performed. On the other hand, however, in such a dry construction method, the abrasive grain layer which constitutes the cutting blade tips causes clogging immediately due to the dust of the chips, thereby impairing the grinding action. Thus, a problem occurs that efficient drilling becomes impossible.

Thus, a drilling apparatus and a dresser supply device are suggested in, for example, unexamined JP Publication No. H08-18326, unexamined JP Publication No. H08-18327, and JP Publication No. 2549787. In the afore-mentioned Patent Documents, the drilling apparatus and the dresser supply device with improved drilling efficiency are disclosed. Namely, a proper quantity of dresser (grinding material) along with compressed air is intermittently supplied to the cutting blade tips of a core drill, thereby the self-growing action of abrasive grains which become the cutting blades is promoted while the grain layer is dressed even during the drilling. Consequently, the sharpness of the cutting tips is maintained. Moreover, the inventors of the present invention have also suggested a drilling apparatus equipped with such a dresser supply device, and using ultrafine anhydrous silica with a particle size of 5 to 50 nm which has a silanol group as the dresser, in unexamined JP Publication No. 2002-370167

Meanwhile, in the dresser supply devices described in unexamined JP Publication No. H08-18327, JP Publication No. 2549787, and unexamined JP Publication No. 2002-370167, a tank holding the dresser is only connected to a supply pipe which supplies compressed air toward a core drill via a valve. For this reason, the valve should be frequently opened and closed in intermittently supplying the dresser. The dresser to be supplied is a hard dresser having the same property as the abrasive grains. Thus, there is a possibility in that the valve body which engulfs the dresser cannot be reliably opened and closed. Moreover, there is a possibility in that the dresser cannot be supplied early due to severe damage of the valve.

On the other hand, a supply device in which the tank of the dresser is connected to the compressed air supply pipe via the valve as described above is described in unexamined JP Publication No. H08-18326. In addition, the supply pipe is branched by a solenoid valve of a three-way valve type into an air supply line which goes to core drill side from this valve, and a dresser supply line arranged between the air supply line and the valve, a dresser tank is connected to the dresser supply line via a T-shaped discharge nozzle, and a branch pipe branches from between a discharge nozzle of the dresser supply line and the valve is connected to an upper end of the dresser tank is also described in unexamined JP Publication No. H08-18326. In this dresser supply device, when compressed air passes through the air supply line, the dresser is not supplied, and when compressed air flows into the dresser supply line by the switching of the solenoid valve, a portion of the dresser flows into the dresser tank from the branch pipe, and thus the pressure within the tank becomes equal to the pressure of the discharge nozzle. Thereby, the dresser is discharged to a main pipe of the dresser supply line and is supplied to the core drill side by the remaining compressed air that flows through the main pipe.

However, in this dresser supply device, the connection between the dresser tank and the main pipe of the dresser supply line is made by a mere T-shaped discharge nozzle. Therefore, it is difficult to exactly control the discharge amount of the dresser to be discharged from the dresser tank to the main pipe of the dresser supply line, i.e., the supply amount per once of the dresser to be intermittently supplied to the core drill at every switching of the solenoid valve so as to always become a certain quantity For this reason, if the amount of supply of the dresser is little, the abrasive grain layer is not sufficiently dressed, and the sharpness of the cutting blade tips cannot be maintained. On the contrary, if the supply amount is excessive, the abrasive grain layer may be dressed more than needed. Thus, there is a possibility of significantly shortening the product life of the core drill.

Further, in this dresser supply device, the control of the discharge amount of the dresser is difficult. Thus, there is also a possibility of discharging a larger amount of dresser at a time from the dresser tank. The dresser discharged in large quantity in this way may form a bridge to block the main pipe. Accordingly, in this case, the subsequent dresser supply becomes impossible. Therefore, once drilling operation is interrupted, the dresser with which a bridge is formed has to be removed. As a result, operating efficiency may be lowered significantly.

The prevent invention is achieved in view of the above circumstances, and has an object of providing a dresser supply device which can more accurately and more reliably supply a specific amount of dresser in intermittently supplying the dresser to an abrasive grain layer during grinding by a grinding tool, such as the drilling by the aforementioned core drill.

In order to solve the above problems to achieve such an object, the present invention provides a dresser supply device of a grinding tool which supplies powdery dresser to a grinding tool having an abrasive grain layer on cutting blade tips. The dresser supply device includes: an air supply source which supplies air; a dresser supply air pipe including a base end which is connected to the air supply source; a dresser tank which holds the dresser; a dresser supply pipe which connects the dresser tank and the dresser supply air pipe to each other, is smaller in diameter than the dresser supply air pipe at a connecting portion with the dresser supply air pipe, has a first tip inserted and projecting into the dresser supply air pipe, and is located at a space from an inner peripheral surface of the dresser supply air pipe; and an opening-and-closing valve which is provided in the dresser supply air pipe between the connecting portion and the air supply source side.

The supply device of the invention may further include a control unit which allows the opening-and-closing valve to be opened and closed intermittently. When the opening-and-closing valve is opened, the air from the air supply source is introduced into the dresser supply air pipe, and the dresser supplied into the dresser supply air pipe via the dresser supply pipe from the dresser tank is supplied to the grinding tool side along with air. At this time, since the opening-and-closing valve is disposed closer to the air supply source, i.e., the more upstream side than the connecting portion with the dresser supply pipe to which the dresser is supplied in the dresser supply air pipe, the dresser does not pass the opening-and-closing valve, and the opening-and-closing valve is not damaged by engulfing, etc. of the dresser.

Next, when the opening-and-closing valve is closed, powdery dresser is supplied via the dresser supply pipe from the dresser tank and is held within the dresser supply air pipe at the connecting portion with the dresser supply pipe. At this time, in the present invention, the dresser supply pipe is smaller in diameter than the dresser supply air and has a first tip protruding and inserted into the dresser supply air pipe at a space from the inner peripheral surface of the dresser supply air pipe, the dresser forms a cone at a tapered angle according to an angle of repose between the first tip of the dresser supply pipe and the inner peripheral surface of the dresser supply air pipe.

Since the cone formed in this way is stabilized so as to form a bridge between the first tip of the dresser supply pipe and the inner peripheral surface of the dresser supply air pipe, a lot of dresser exceeding the volume of the cone is not supplied at a stretch. Accordingly, the gap between the first tip of the dresser supply pipe and the inner peripheral surface of the dresser supply air pipe is set such that the amount of dresser of a cone to be formed between them becomes an amount according to the supply amount per once of the dresser to be supplied to the grinding tool side, so that a specific amount of dresser can always be exactly supplied to the inside of the dresser supply air pipe.

On the other hand, the dresser supply pipe of a small diameter projects and is inserted into the dresser supply air pipe. As a result, at the connecting portion between the dresser supply pipe and the dresser supply air pipe, dresser is supplied into the dresser supply air pipe and even though the cone is formed, a gap portion is formed between the inner peripheral surface of the dresser supply air pipe and the outer peripheral surface of the dresser supply pipe. Moreover, the area of the gap portion is smaller than the cross-sectional area in the dresser supply air pipe. For this reason, the air introduced into the dresser supply air pipe when the opening-and-closing valve is opened next pushes and collapses the dresser formed in a conical shape when passing through the connecting portion, or increases in flow rate so as to engulf the dresser when passing through the gap portion with small area and is thereby supplied to the grinding tool side along with the dresser.

As such, according to the dresser supply device of the invention, it is possible to exactly supply a specific amount of dresser to the dresser supply air pipe by intermittent opening-and-closing of the opening-and-closing valve, and it is possible to reliably supply the dresser to the grinding tool side by air. Accordingly, it is possible to reliably dress the abrasive grain layer which forms the cutting blade tips of the grinding tool, such as a core drill without causing excessive wear, thereby performing grinding while the sharpness thereof is maintained. Thereby, a grinding operation, such as stable and efficient drilling, can be performed while the extension of tool life is achieved.

Here, the gap between the first tip of the dresser supply pipe and the inner peripheral surface of the dresser supply air pipe may is adjustable. In this case, even if changes occurs in various conditions during the grinding operation, such as drilling by a core drill, according to the changes, by the gap is adjusted it is possible to intermittently supply dresser in a supply amount per once which is always optimal.