Patent GB-1438571-A (GB)
Title: Hammer drill
IPC: B23B45/16
Filed: 1973-08-29
Abstract: 1438571 Rotary/percussive drills SKIL (NEDERLAND) NV 29 Aug 1973 [30 Aug 1972 23 April 1973] 40719/73 Heading B3C [Also in Divisions B4 and F2] A power tool Figs. 1, 4 and 5 comprises a coupling between first and second rotary members 32, 20 and hammering elements 22, 23 which are urged apart as by a spring 28 and engaged when the tool is pressed against a workpiece, the arrangement being such that combined hammering and drilling is achieved when the rotary members are coupled and the hammering elements are engaged, drilling only is achieved when the rotary members are coupled and the hammering elements are disengaged, and hammering only is achieved when the rotary members are uncoupled and the hammering elements are engaged. The second rotary member 20 consists of a hollow shaft driven from an electric or pneumatic motor through gears 11, 18, the end of the shaft having a hexagonal portion 38. The first rotary member 32 carries a drill chuck 37 at one end and a bearing sleeve 30 at the other, the middle portion being formed with three hexagonal formations 32c, 32d and 32e separated by annular grooves 32f and 32g. The coupling sleeve 40 has a hexagonal inner surface for co-operating with the hexagonal formations 32c, 32d and 32e on the first rotary member and the hexagonal portion 38 on the second rotary member. The coupling sleeve 40 can be adjusted axially to any one of three positions by locating a locking collar 44 in any one of grooves 32f, 32g or 32h; the locking collar 44 has an end wall 44c, Fig. 4, which can be adjusted between ball catch positions 44a, 44b to align its six flats 44e with those of the inner surface of the coupling sleeve when the sleeve is to be axially adjusted. In the end position shown, the locking collar 44 is located in the groove 32h so that when the tool is pressed against a workpiece the first and second rotary members 32, 20 move back against the action of the spring 28 to cause ratcheting teeth 22, 23 to engage and cause the hammering only action of the tool. In the intermediate position, the locking collar 44 is located in the groove 32g so that the coupling sleeve is coupled with the hexagonal portion 38; with the rotary members now coupled, axial movement of the members 32, 20 due to the pressure of the tool on a workpiece causes the ratcheting teeth 22, 23 to engage. When the rotary drilling action is desired without hammering, the locking collar 44 is located in the groove 32f and the ratcheting teeth are kept apart by the stop 42a on the housing preventing rearward movement of the rotary members when the tool is pressed against a workpiece. To prevent relative rotation due to frictional drag when a hammering action only is required a pin 50 on the housing may be pushed into a notch 40f in the coupling sleeve. In a second embodiment, Fig. 7, the second rotary member 16<SP>1</SP> has a gearwheel 13<SP>1</SP> mounted on one end and keyways 35<SP>1</SP> provided on its other. The first rotary member 28<SP>1</SP> carries a drill chuck 40<SP>1</SP> and includes an enlarged cylindrical portion 361 provided with keyways 37<SP>1</SP>. The coupling sleeve 48<SP>1</SP> is provided internally at one end with keys 50<SP>1</SP> which engage in the keyways 37<SP>1</SP> and at the other end with keys 49<SP>1</SP> which can engage in the keyways 35<SP>1</SP> when the coupling sleeve is adjusted forwardly against the action of a spring 56<SP>1</SP>. Three positions of axial adjustment is possible by arranging a stepped cam formation 66<SP>1</SP> on the housing collar 651 for co-operation with a cam surface on a rotatably-adjustable collar 581 journalled on the coupling sleeve by means of a bearing sleeve 53<SP>1</SP>. In the position shown, the bottom step of the cam formation has been engaged by rotatably adjusting the collar 58<SP>1</SP> so that the coupling sleeve 48<SP>1</SP> is pressed into its rearmost position where the keys 49<SP>1</SP> are uncoupled from the keyways 37<SP>1</SP> to permit hammer action only when the ratcheting teeth 21<SP>1</SP>, 22<SP>1</SP> are engaged upon the tool being pressed against a workpiece. Relative rotation due to frictional drag may be prevented by teeth 70<SP>1</SP> on the coupling sleeve engaging teeth 71<SP>1</SP> on the housing. In the middle position of axial adjustment of the coupling sleeve 48<SP>1</SP> (Fig. 8, not shown) the keys 49<SP>1</SP> are engaged with the keyways 35<SP>1</SP> of the driven second rotary member 16<SP>1</SP>; with the rotary members now coupled, axial movement of the members 28<SP>1</SP>, 161 due to the pressure of the tool on a workpiece causes the ratcheting teeth 21<SP>1</SP>, 22<SP>1</SP> to engage. When the rotary drilling action is desired without hammering, the coupling sleeve 48<SP>1</SP> is moved to its forwardmost position so that rearward movement of the members 28<SP>1</SP>, 16<SP>1</SP> is prevented when the tool is pressed against a workpiece due to the abutment of a washer 421 against the now closelyspaced end face 48b, 63<SP>1</SP> of the coupling sleeve.