Method and means for operating a drill for eliminating axial scratches during retraction

Claim 5

In a drill of the type having a housing which supports a rotatable spindle carrying a drill bit; a workpiece engaging member, two air motors for rotating said spindle at a given minimum rpm, pneumatic cylinder means and piston means for linearly moving said housing, spindle, and drill bit relative to said workpiece engaging member during feed and retract strokes, said housing, spindle and drill bit being moved forward relative to said workpiece engaging member during the feed stroke for drilling a hole in the workpiece, said housing, spindle and drill bit being moved rearward relative to the said workpiece engaging member during the retract stroke for withdrawing said drill bit from the hole drilled in the workpiece, input air means, means for controlling the flow of air from said input air means to said pneumatic cylinder means for producing the feed and retract strokes, means for controlling the flow of air from said input air means to said two air motors for operating said two air motors during the feed stroke for rotating said spindle and drill bit, and hydraulic means for controlling the rate of forward and rearward movement of said housing and hence of said spindle and drill bit during the feed stroke and retract stroke respectively, the improvement comprising: an auxiliary air conduit extending from said input air means to one of said air motors for operating only said one air motor during the retract stroke for rotating said spindle and hence the drill bit at a rpm less than said given minimum rpm, said hydraulic means restricting the rate of rearward movement of said housing, spindle, and drill bit during the retract stroke, whereby: the drill bit is caused to be rotated while being retracted from the hole such that the ratio V L /V R during retraction is less than 0.22, wherein V L is the linear velocity of the drill bit at its axis during retraction and V R is equal to the product of the radius of the drill bit and its angular velocity during retraction.

Claim 6

In a drill of the type having a housing which supports a rotatable spindle carrying a drill bit; a workpiece engaging member, two air motors for rotating said spindle at a given minimum rpm, pneumatic cylinder means and piston means for linearly moving said housing, spindle, and drill bit relative to said workpiece engaging member during feed and retract strokes, said housing, spindle and drill bit being moved forward relative to said workpiece engaging member during the feed stroke for drilling a hole in the workpiece, said housing, spindle and drill bit being moved rearward relative to the said workpiece engaging member during the retract stroke for withdrawing said drill bit from the hole drilled in the workpiece, input air means, means for controlling the flow of air from said input air means to said pneumatic cylinder means for producing the feed and retract strokes, means for controlling the flow of air from said input air means to said two air motors for operating said two air motors during the feed stroke for rotating said spindle and drill bit, and hydraulic means for controlling the rate of forward and rearward movement of said housing and hence of said spindle and drill bit during the feed stroke and retract stroke respectively, the improvement comprising: an auxiliary air conduit extending from said input air means to one of said air motors for operating only said one air motor during the retract stroke for rotating said spindle and hence the drill bit at a rpm less than said given minimum rpm, said hydraulic means restricting the rate of rearward movement of said housing, spindle, and drill bit during the retract stroke, whereby: the drill bit is caused to be rotated while being retracted from the hole such that the ratio V L /V R during retraction is less than 0.22, wherein V L is the linear velocity of the drill bit at its axis during retraction and V R is equal to the product of the radius of the drill bit and its angular velocity during retraction.

Claim 7

In a drill of the type having a housing which supports a rotatable spindle carrying a drill bit; a workpiece engaging member, two air motors for rotating said spindle at a given minimum rpm, pneumatic cylinder means and piston means for linearly moving said housing, spindle, and drill bit relative to said workpiece engaging member during feed and retract strokes, said housing, spindle and drill bit being moved forward relative to said workpiece engaging member during the feed stroke for drilling a hole in the workpiece, said housing, spindle and drill bit being moved rearward relative to the said workpiece engaging member during the retract stroke for withdrawing said drill bit from the hole drilled in the workpiece, input air means, means for controlling the flow of air from said input air means to said pneumatic cylinder means for producing the feed and retract strokes, means for controlling the flow of air from said input air means to both of said air motors for operating both of said air motors during the feed stroke, and hydraulic means for controlling the rate of forward and rearward movement of said housing and hence of said spindle and drill bit during the feed stroke and retract stroke respectively, the improvement comprising: an auxiliary air conduit extending from said input air means to one of said air motors for operating only said one air motor during the retract stroke for rotating said spindle at an rpm less than said given minimum rpm, said hydraulic means restricting the rate of rearward movement of said housing, spindle, and drill bit during the retract stroke.

Claim 8

In a drill of the type having a housing which supports a rotatable spindle carrying a drill bit; a workpiece engaging member, two air motors for rotating said spindle at a given minimum rpm, pneumatic cylinder means and piston means for linearly moving said housing, spindle, and drill bit relative to said workpiece engaging member during feed and retract strokes, said housing, spindle and drill bit being moved forward relative to said workpiece engaging member during the feed stroke for drilling a hole in the workpiece, said housing, spindle and drill bit being moved rearward relative to the said workpiece engaging member during the retract stroke for withdrawing said drill bit from the hole drilled in the workpiece, input air means, means for controlling the flow of air from said input air means to said pneumatic cylinder means for producing the feed and retract strokes, means for controlling the flow of air from said input air means to both of said air motors for operating both of said air motors during the feed stroke, and hydraulic means for controlling the rate of forward and rearward movement of said housing and hence of said spindle and drill bit during the feed stroke and retract stroke respectively, the improvement comprising: an auxiliary air conduit extending from said input air means to one of said air motors for operating only said one air motor during the retract stroke for rotating said spindle at an rpm less than said given minimum rpm, said hydraulic means restricting the rate of rearward movement of said housing, spindle, and drill bit during the retract stroke.

Claim 9

In a drill of the type having a housing which supports a rotatable spindle carrying a drill bit; a workpiece engaging member, two air motors for rotating said spindle at a given minimum rpm, pneumatic cylinder and piston means for linearly moving said housing, spindle, and drill bit relative to said workpiece engaging member during feed and retract strokes, said housing, spindle and drill bit being moved forward relative to said workpiece engaging member during the feed stroke for drilling a hole in the workpiece, said housing, spindle and drill bit being moved rearward relative to the said workpiece engaging member during the retract stroke for withdrawing said drill bit from the hole drilled in the workpiece, input air means, means for controlling the flow of air from said input air means to said pneumatic cylinder means for producing the feed and retract strokes, means for controlling the flow of air from said input air means to both of said air motors for operating both of said air motors during the feed stroke, and hydraulic means for controlling the rate of forward movement of said housing and hence of said spindle and drill bit during the feed stroke, the improvement comprising: an auxiliary air conduit extending from said input air means to one of said air motors for operating only said one air motor during the retract stroke for rotating said spindle at a rpm less than said given minimum rpm, and means comprising said hydraulic means for restricting the rate of rearward movement of said housing, spindle, and drill bit during the retract stroke.

Claim 10

In a drill of the type having a housing which supports a rotatable spindle carrying a drill bit; a workpiece engaging member, two air motors for rotating said spindle at a given minimum rpm, pneumatic cylinder and piston means for linearly moving said housing, spindle, and drill bit relative to said workpiece engaging member during feed and retract strokes, said housing, spindle and drill bit being moved forward relative to said workpiece engaging member during the feed stroke for drilling a hole in the workpiece, said housing, spindle and drill bit being moved rearward relative to the said workpiece engaging member during the retract stroke for withdrawing said drill bit from the hole drilled in the workpiece, input air means, means for controlling the flow of air from said input air means to said pneumatic cylinder means for producing the feed and retract strokes, means for controlling the flow of air from said input air means to both of said air motors for operating both of said air motors during the feed stroke, and hydraulic means for controlling the rate of forward movement of said housing and hence of said spindle and drill bit during the feed stroke, the improvement comprising: an auxiliary air conduit extending from said input air means to one of said air motors for operating only said one air motor during the retract stroke for rotating said spindle at a rpm less than said given minimum rpm, and means comprising said hydraulic means for restricting the rate of rearward movement of said housing, spindle, and drill bit during the retract stroke.

Claim 11

A drill, comprising: a rotatable spindle for carrying a drill bit, power means comprising two motors for rotating said spindle and drill bit, means for feeding said spindle and drill bit forward during a feed stroke while said two motors are operated for drilling a hole in a work piece, means for moving said spindle and drill bit rearward for retracting the drill bit from the hole, retract power control means for causing only one of said motors to be operated during retraction for rotating said spindle and drill bit while the drill bit is being retracted from the hole, and retract rate restriction means for controlling the rate at which said spindle and drill bit are moved rearward during retraction, said retract power control means and said retract rate restriction means being employed for causing said spindle and drill bit to be rotated while the drill bit is being retracted from the hole such that the ratio V L /V R during retraction is less than 0.22, wherein V L is the linear velocity of the drill bit at its axis during retraction and V R is equal to the product of the radius of the drill bit and its angular velocity during retraction.

Claim 12

A drill, comprising: a rotatable spindle for carrying a drill bit, power means comprising two motors for rotating said spindle and drill bit, means for feeding said spindle and drill bit forward during a feed stroke while said two motors are operated for drilling a hole in a work piece, means for moving said spindle and drill bit rearward for retracting the drill bit from the hole, retract power control means for causing only one of said motors to be operated during retraction for rotating said spindle and drill bit while the drill bit is being retracted from the hole, and retract rate restriction means for controlling the rate at which said spindle and drill bit are moved rearward during retraction, said retract power control means and said retract rate restriction means being employed for causing said spindle and drill bit to be rotated while the drill bit is being retracted from the hole such that the ratio V L /V R during retraction is less than 0.22, wherein V L is the linear velocity of the drill bit at its axis during retraction and V R is equal to the product of the radius of the drill bit and its angular velocity during retraction.

Claim 13

The drill of claim 6, wherein: said two motors rotate said spindle and drill bit during the feed stroke at a given minimum rpm, said retract power control means causes said one motor to rotate said spindle and drill bit while the drill bit is being retracted from the hole at a rpm less than said given minimum rpm.

Claim 14

A drill, comprising: a rotatable spindle for carrying a drill bit, power means comprising two motors for rotating said spindle and drill bit, means for feeding said spindle and drill bit forward during a feed stroke while said two motors are operated for drilling a hole in a work piece, means for moving said spindle and drill bit rearward for retracting the drill bit from the hole, retract power control means for causing only one of said motors to be operated during retraction for rotating said spindle and drill bit while the drill bit is being retracted from the hole, and retract rate restriction means for controlling the rate at which said spindle and drill bit are moved rearward during retraction, said retract power control means and said retract rate restriction means being employed for causing the drill bit to be rotated while being retracted from the hole drilled in the workpiece such that the wall of the hole in the workpiece is free from axially aligned scratches and circumferential scratches in the wall of the hole caused by the drill bit upon retraction define an angle relative to a plane perpendicular to the axis of the hole less than about 13°.

Claim 15

A drill, comprising: a rotatable spindle for carrying a drill bit, power means comprising two motors for rotating said spindle and drill bit, means for feeding said spindle and drill bit forward during a feed stroke while said two motors are operated for drilling a hole in a work piece, means for moving said spindle and drill bit rearward for retracting the drill bit from the hole, retract power control means for causing only one of said motors to be operated during retraction for rotating said spindle and drill bit while the drill bit is being retracted from the hole, and retract rate restriction means for controlling the rate at which said spindle and drill bit are moved rearward during retraction, said retract power control means and said retract rate restriction means being employed for causing the drill bit to be rotated while being retracted from the hole drilled in the workpiece such that the wall of the hole in the workpiece is free from axially aligned scratches and circumferential scratches in the wall of the hole caused by the drill bit upon retraction define an angle relative to a plane perpendicular to the axis of the hole less than about 13°.

Claim 16

The drill of claim 8, wherein: said two motors rotate said spindle and drill bit during the feed stroke at a given minimum rpm, said retract power control means causes said one motor to rotate said spindle and drill bit while the drill bit is being retracted from the hole at a rpm less than said given minimum rpm.