GB1593279A

GB1593279A - Pneumatically operated drill removing cutting debris by suction

Info

Publication number: GB1593279A
Application number: GB616/77A
Authority: GB
Original assignee: Compair Industrial Ltd
Current assignee: Compair Industrial Ltd
Priority date: 1978-01-27
Filing date: 1978-01-27
Publication date: 1981-07-15

Description

(54) PNEUMATICALLY OPERATED DRILL REMOVING CUTTING DEBRIS BY SUCTION (71) We, COMPAIR INDUSTRIAL LIMITED, a British Company, of P.O. Box 7, Broomwade Works, High Wycombe, Buckinghamshire, HP13 5SF, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to pneumatically operated drills and more particularly to pneumatically operated drills of the kind comprising a pneumatically operated motor having an air inlet and an air outlet, an output shaft drivably connected to the motor, a drill bit and means for co-axially securing the drill bit to the output shaft.

Such pneumatically operated drills will hereafter be referred to as "of the kind described".

The invention provides a pneumatically operated drill of the kind described in which a restriction is provided in the air outlet and a passage connect an area adjacent to and downstream of the restriction to an area adjacent the drill bit, the arrangement being such that, in use, suction is created in the passage and around the drill bit.

Preferably the drill includes a first casing for the motor and the passage comprises an annular passage formed between the first casing and a second outer casing.

Preferably the air outlet comprises an annular passage and preferably the restriction is a narrowing in the annular passage.

The air inlet may be a cylindrical passage concentric with and housed within the air outlet passage.

A preferred embodiment of a pneumatically operated drill according to the invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is an outside elevation of a pneumatically operated drill according to the invention, connected to a filter; Figure 2 is a longitudinal section through the left-hand end of the drill as viewed in Figure 1; Figure 3 is a transverse section along the line 3-3 of Figure 2; Figure 4 is a longitudinal section through the right-hand end of the drill as viewed in Figure 1; and Figure 5 is a section along the line 5-5 of Figure 4.

Referring first to Figure 1, a pneumatically operated drill 10 has an air inlet connection 11 and an air outlet connection 12. A pipe 13 connects the air outlet connection 12 to a collector 14 which includes a filter which may be of any suitable type.

The drill 10 is generally cylindrical in overall configuration and a drill bit 16 extends from an end of the drill opposite to the air inlet and outlet connections 11 and 12. An operating button 17 protrudes from one side of the drill.

Turning now to Figure 2, the drill bit 16 is firmly clamped in a chuck 18 of conventional design which is carried by a shaft 19. The shaft 19 is driven, in use, by a pneumatically operated motor (not shown) of known type.

The motor is located at 20 (see Figure 4) and may be directly connected to the shaft 19 or via a gearbox or other similar device. The motor is housed in a tubular casing 21, end portions of which are shown in Figures 2 and 4.

Pressurised air from operating the motor is fed into the motor through a central aperture 23 and exhaust air from the motor leaves via peripheral apertures 24. The operating button 17 normally closes off the inlet aperture 23 and is operable to open the aperture to allow pressurised air to enter the motor.

An orifice member 26 of hollow stepped cylindrical configuration is inserted into the right-hand end of the casing 21 as viewed in Figure 4. The smallest diameter portion 27 of member 26 is a sealing fit in a reduced diameter portion of the casing 21 adjacent the inlet orifice 23 and the member 26 is maintained in coaxial relationship with the casing 21 by the central part 28 of the member 26 which is a close or screwed fit within the casing 21 and includes cutaway portions 29 (see Figure 5) which allow fluid flow therethrough . Immediately adjacent the right-hand end of the casing 21, the member 26 is flared in frusto-conical manner to provide a narrow annular passage 31 between the member 26 and the casing 21.

The hollow interior of the member 26 provides an inlet passage 33 which is connected by a pipe 34 to the air inlet connection 11.

An outer casing, generally indicated by 36 and formed in three sections 37, 38 and 39 fits around the casing 21 and is coaxial therewith. The centre portion 38 of casing 36 is connected to casing 21 by grub screws 41 which pass through spacers 42 interposed between section 38 and casing 21 to maintain the two casings in spaced relationship.

Fluid may flow through gaps 43 between the spaces (see Figure 3). The left-hand section 37 of the casing 36 is rigidly attached to the centre section 38 and includes, at its lefthand end, an inwardly directed annular flange 45. A drill guard 46 is a sliding fit within the section 37 and is prevented from falling out by inwardly directed flange 45.

The guard 46 is urged by a spring 47 into the position shown in Figure 2 and is pushed back, towards the right as viewed in Figure 2, when the drill is in use by contact of the guard on the workpiece being drilled. The right-hand section 39 of casing 36 is generally frusto-conical and is connected at its wider end to section 38 by grub screws 49.

The three sections of the casing 36 together provide an annular passage 50 connecting the area around the drill bit 16 to the area immediately downstream of the narrow annular passage 31.

As will be seen from the arrows in Figure 4, air enters the motor via tube 34 and passage 33 and leaves via the apertures 24 and the annular passage formed between member 26 and casing 31 and between the section 39 of casing 36 and the inlet pipe 34.

An end cap 51 fits over the narrow end of section 39 and diverts the exhaust air into the air outlet connection 12.

It will be appreciated that the exhaust air passing through the narrow annular passage 31 creates a Venturi flow which creates a suction at the outlet end of passage 31. This suction is applied to the annular passage 50 between the casing 36 and the casing 21, and causes the swarf created by the operation of the drill bit 16 to be sucked into the annular passage 50 between the two casings and thus to be taken away via the outlet connection 12. The air carrying the swarf then passes via pipe 13 to the collector 14 and the swarf is removed from the air by the filter.

WHAT WE CLAIM IS: 1. A pneumatically operated drill of the kind described in which a restriction is provided in the air outlet and a passage connects an area adjacent to and downstream of the restriction to an area adjacent the drill bit, the arrangement being such that, in use, suction is created in the passage and around the drill bit.

2. A drill as claimed in claim 1 including a first casing for the pneumatically operated motor and in which the passage comprises an annular passage formed between the first casing and a second outer casing of the drill.

3. A drill as claimed in claim 1 or claim 2 in which the air outlet comprises an annular passage and the restriction comprises a narrowing in the annular passage.

4. A drill as claimed in claim 3 in which the air inlet comprises a cylindrical passage concentric with the air outlet passage.

5. A drill as claimed in claim 2 in which the air outlet is an annular passage defined by a cylindrical extension of the first casing and an orifice member concentrically housed within said extension, said member including a frusto-conical portion which provides said restriction.

6. A drill as claimed in claim 5 in which the air inlet comprises a bore formed in said orifice member, the bore being adapted means for connecting a source of compressed air thereto.

7. A drill as claimed in any one of claims 2 to 6 further comprising a drill guard which extends around the drill bit, the guard comprising a tubular member slidably mounted within an end of the second casing adjacent the drill bit and resiliently urged into a position surrounding the drill bit.

8. A pneumatically operated drill substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Figure 4. The smallest diameter portion 27 of member 26 is a sealing fit in a reduced diameter portion of the casing 21 adjacent the inlet orifice 23 and the member 26 is maintained in coaxial relationship with the casing 21 by the central part 28 of the member 26 which is a close or screwed fit within the casing 21 and includes cutaway portions 29 (see Figure 5) which allow fluid flow therethrough . Immediately adjacent the right-hand end of the casing 21, the member 26 is flared in frusto-conical manner to provide a narrow annular passage 31 between the member 26 and the casing 21. The hollow interior of the member 26 provides an inlet passage 33 which is connected by a pipe 34 to the air inlet connection 11. An outer casing, generally indicated by 36 and formed in three sections 37, 38 and 39 fits around the casing 21 and is coaxial therewith. The centre portion 38 of casing 36 is connected to casing 21 by grub screws 41 which pass through spacers 42 interposed between section 38 and casing 21 to maintain the two casings in spaced relationship. Fluid may flow through gaps 43 between the spaces (see Figure 3). The left-hand section 37 of the casing 36 is rigidly attached to the centre section 38 and includes, at its lefthand end, an inwardly directed annular flange 45. A drill guard 46 is a sliding fit within the section 37 and is prevented from falling out by inwardly directed flange 45. The guard 46 is urged by a spring 47 into the position shown in Figure 2 and is pushed back, towards the right as viewed in Figure 2, when the drill is in use by contact of the guard on the workpiece being drilled. The right-hand section 39 of casing 36 is generally frusto-conical and is connected at its wider end to section 38 by grub screws 49. The three sections of the casing 36 together provide an annular passage 50 connecting the area around the drill bit 16 to the area immediately downstream of the narrow annular passage 31. As will be seen from the arrows in Figure 4, air enters the motor via tube 34 and passage 33 and leaves via the apertures 24 and the annular passage formed between member 26 and casing 31 and between the section 39 of casing 36 and the inlet pipe 34. An end cap 51 fits over the narrow end of section 39 and diverts the exhaust air into the air outlet connection 12. It will be appreciated that the exhaust air passing through the narrow annular passage 31 creates a Venturi flow which creates a suction at the outlet end of passage 31. This suction is applied to the annular passage 50 between the casing 36 and the casing 21, and causes the swarf created by the operation of the drill bit 16 to be sucked into the annular passage 50 between the two casings and thus to be taken away via the outlet connection 12. The air carrying the swarf then passes via pipe 13 to the collector 14 and the swarf is removed from the air by the filter. WHAT WE CLAIM IS:

1. A pneumatically operated drill of the kind described in which a restriction is provided in the air outlet and a passage connects an area adjacent to and downstream of the restriction to an area adjacent the drill bit, the arrangement being such that, in use, suction is created in the passage and around the drill bit.