GB2108020A - Feed control for hand-held drill - Google Patents

Abstract

The drill has a foot 6 which is pressed against the workpiece and which retracts at a controlled rate to control the drill feed rate. The foot 6 is attached to a piston 9 which is displaced along a cylinder 8 and thereby forces oil through orifices 11, 12. The oil returns to the other side of the piston via oil gallery 18. When the drill is withdrawn from the workpiece, a disc 16 falls away from the piston, thereby uncovering aperture 14, and the piston is returned to its starting position by a spring acting between abutment 17 and the right-hand end of the cylinder. <IMAGE>

Description

SPECIFICATION Hand-held drips This invention relates to hand-held drills, and especially to means for feeding the drill towards the workpiece.

The invention provides a hand-held drill having a foot to be pressed against the workpiece, in which fluid is in operation forced through an orifice as a result of pressure on the foot to control the rate of feed of the drill.

Advantageously, pressure on the foot moves a piston in a cylinder to force the fluid through the orifice. Preferably, the foot is connected by means of a leg to the piston.

Advantageously, a spring is provided for returning the piston to its initial position after it has moved through the cylinder.

A hand-held drill with controlled feed rate will now be described, by way of example, with reference to the accompanying drawing, which is a side view, partly in section, of the drill.

Referring to the drawing, a hand-held drill has a piston-grip handle 1 with a button 2 which is depressed by the operator to supply air to an air motor 3 having an exhaust 3a. The motor carries a chuck 4 in which a bit 5 is mounted. The feed rate of the drill is controlled by a hydromechanical system comprising a foot 6 which is pressed against the workpiece by the operator, and a piston and cylinder arrangement indicated generally by the reference numeral 7. The cylinder 8 is rigidly secured to the motor 3 and pistol grip 1 and the foot 6 is rigidly secured to the piston 9 by means of a leg 10. The feed rate of the drill is the rate at which oil is forced by the piston through orifices 1 1, 12. The operator holds the drill with the foot 6 against the workpiece. At this stage, the foot will be to the left of the bit.As drilling commences, the operator presses the drill against the workpiece via the foot, and this retracts into the cylinder at a controlled rate, and so the bit advances into the workpiece at a controlled rate.

Because of the shape of the foot, the drill is kept perpendicular to the workpiece and is thus less likely to break.

The piston 9 consists of a main part 13 having an axial aperture 14 in it, a plastics sealing part 15 having a flared periphery to engage the cylinder wall and an aperture registering with the aperture 14, and a disc 16 which covers the aperture. The leg 10 has a counterpart on the other side of the piston and this bears an abutment 17. A compression spring (not shown) acts between the abutment and the right hand end wall of the cylinder.

On the working stroke, the piston 9 is forced to the right. The disc 16 covers the aperture in the piston. Oil is forced through orifices 1 1, 12 and returns to the other side of the piston by means of an oil gallery 18. The size of orifice 12 is adjustable by means of an adjusting screw (not shown) to regulate the oil flow and hence the feed rate.

On the return stroke, that is, when drilling is complete and the drill is withdrawn from the workpiece, the spring pushes the piston 9 to the left as seen in the drawing. The disc 16 falls away from the main part of the piston (but is retained by the abutment 17), allowing oil to pass through the aperture 14 and around the outer periphery of the disc 16. The piston 9 and hence the foot 6 are turned to their initial positions ready for the next drilling operation.

The foot 6 is detachable to allow specially made feet to be used for particular operations e.g.

drilling contoured surfaces.

An adjustable collar could be provided on the leg 10 to prevent its retraction beyond a certain point, and a scale could be provided on the leg to enable it to be set to any desired depth.

1. A hand-held drill having a foot to be pressed against the workpiece, in which fluid is in operation forced through an orifice as a result of pressure on the foot to control the rate of feed of the drill.

2. A drill as claimed in claim 1 wherein a piston moves in a cylinder as the foot is pressed against the workpiece to force the fluid through the orifice.

3. A drill as claimed in claim 2, wherein the piston is connected to the foot by means of a leg.

4. A drill as claimed in claim 2, wherein a spring is provided for returning the piston to its initial position after it has been moved through the cylinder.

5. A drill as claimed in claim 4, wherein the piston incorporates a one-way valve which is blocked when the piston is moving on a working stroke and open when the piston is on a return stroke.

6. A drill as claimed in claim 5, wherein the piston comprises a main section having an aperture passing through it in an axial direction, and a disc which covers the aperture.

7. A drill substantially as hereinbefore described with reference to, and as shown in, the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Hand-held drips This invention relates to hand-held drills, and especially to means for feeding the drill towards the workpiece. The invention provides a hand-held drill having a foot to be pressed against the workpiece, in which fluid is in operation forced through an orifice as a result of pressure on the foot to control the rate of feed of the drill. Advantageously, pressure on the foot moves a piston in a cylinder to force the fluid through the orifice. Preferably, the foot is connected by means of a leg to the piston. Advantageously, a spring is provided for returning the piston to its initial position after it has moved through the cylinder. A hand-held drill with controlled feed rate will now be described, by way of example, with reference to the accompanying drawing, which is a side view, partly in section, of the drill. Referring to the drawing, a hand-held drill has a piston-grip handle 1 with a button 2 which is depressed by the operator to supply air to an air motor 3 having an exhaust 3a. The motor carries a chuck 4 in which a bit 5 is mounted. The feed rate of the drill is controlled by a hydromechanical system comprising a foot 6 which is pressed against the workpiece by the operator, and a piston and cylinder arrangement indicated generally by the reference numeral 7. The cylinder 8 is rigidly secured to the motor 3 and pistol grip 1 and the foot 6 is rigidly secured to the piston 9 by means of a leg 10. The feed rate of the drill is the rate at which oil is forced by the piston through orifices 1 1, 12. The operator holds the drill with the foot 6 against the workpiece. At this stage, the foot will be to the left of the bit.As drilling commences, the operator presses the drill against the workpiece via the foot, and this retracts into the cylinder at a controlled rate, and so the bit advances into the workpiece at a controlled rate. Because of the shape of the foot, the drill is kept perpendicular to the workpiece and is thus less likely to break. The piston 9 consists of a main part 13 having an axial aperture 14 in it, a plastics sealing part 15 having a flared periphery to engage the cylinder wall and an aperture registering with the aperture 14, and a disc 16 which covers the aperture. The leg 10 has a counterpart on the other side of the piston and this bears an abutment 17. A compression spring (not shown) acts between the abutment and the right hand end wall of the cylinder. On the working stroke, the piston 9 is forced to the right. The disc 16 covers the aperture in the piston. Oil is forced through orifices 1 1, 12 and returns to the other side of the piston by means of an oil gallery 18. The size of orifice 12 is adjustable by means of an adjusting screw (not shown) to regulate the oil flow and hence the feed rate. On the return stroke, that is, when drilling is complete and the drill is withdrawn from the workpiece, the spring pushes the piston 9 to the left as seen in the drawing. The disc 16 falls away from the main part of the piston (but is retained by the abutment 17), allowing oil to pass through the aperture 14 and around the outer periphery of the disc 16. The piston 9 and hence the foot 6 are turned to their initial positions ready for the next drilling operation. The foot 6 is detachable to allow specially made feet to be used for particular operations e.g. drilling contoured surfaces. An adjustable collar could be provided on the leg 10 to prevent its retraction beyond a certain point, and a scale could be provided on the leg to enable it to be set to any desired depth. CLAIMS

1. A hand-held drill having a foot to be pressed against the workpiece, in which fluid is in operation forced through an orifice as a result of pressure on the foot to control the rate of feed of the drill.

2. A drill as claimed in claim 1 wherein a piston moves in a cylinder as the foot is pressed against the workpiece to force the fluid through the orifice.

3. A drill as claimed in claim 2, wherein the piston is connected to the foot by means of a leg.

4. A drill as claimed in claim 2, wherein a spring is provided for returning the piston to its initial position after it has been moved through the cylinder.

5. A drill as claimed in claim 4, wherein the piston incorporates a one-way valve which is blocked when the piston is moving on a working stroke and open when the piston is on a return stroke.

6. A drill as claimed in claim 5, wherein the piston comprises a main section having an aperture passing through it in an axial direction, and a disc which covers the aperture.

7. A drill substantially as hereinbefore described with reference to, and as shown in, the accompanying drawing.