GB2126515A

GB2126515A - Mode changer mechanism in power driven vibratory drills

Info

Publication number: GB2126515A
Application number: GB08322596A
Authority: GB
Inventors: Fumio Tashimo; Genji Hirata
Original assignee: Hitachi Koki Co Ltd
Current assignee: Koki Holdings Co Ltd
Priority date: 1982-08-27
Filing date: 1983-08-23
Publication date: 1984-03-28
Also published as: JPS5934906U; GB8322596D0; DE3330888C2; DE3330888A1; GB2126515B

Abstract

A power-driven vibratory drill operates selectively in a drill mode in which a drill chuck drive shaft 9 rotates without axial movement and a vibratory-drill mode in which the drive shaft 9 rotates and moves axially back and forth. For the drill mode, a changeover plate 11 slidably received in a holder 16 in a drill housing 2 is pushed in one direction to keep teeth 15 on a gear 8 fixed to the drive shaft 9 out of engagement with teeth 17 on the holder 16. For operating the drill in the vibratory-drill mode, the changeover plate is pushed in the opposite direction to bring the teeth 15 on the gear 8 into engagement with the teeth 17 on the holder 16. When the drill shaft rotates with a drill bit pressed against a work-piece, the drill shaft is forced to reciprocate axially through alternate engagement and disengagement between the teeth 15, 17. <IMAGE>

Description

SPECIFICATION Mode changer mechanism in power-driven vibratory drills The present invention relates to a mode changer mechanism for enabling a power-driven vibratory drill to switch between a "drill" mode and a "vibratory-drill" mode.

One conventional mode changer mechanism for use in power-driven vibratory drill comprises a change ring threaded in drill housing and manually turnable to bring teeth on a drive shaft and teeth on a housing into engagement with and disengagement from each other. When the teeth on the drive shaft and the housing kept is disengaged, the drive shaft as it rotates remains axially immovable to thereby operate the vibratory drill in a "drill" mode. When the change ring is angularly moved to shift the teeth on the drive shaft into engagement with the teeth on the housing, the drive shaft with a drill bit held against a workpiece is forced to move back and forth to vibrate the drill bit as it is rotated by the drive shaft. The drill now operates in a "vibratory-drill" mode.The change ring however is disadvantageous in that since it is located near a drill chuck holding the drill bit, operator's fingers are likely to touch the rotating drill chuck when the change ring is to be turned for changing the modes. As a precaution, therefore, it is necessary to stop the drive shaft when changing the modes, resulting in a time-consuming mode changeover process. Another problem is that the change ring can only be turned with a relatively large manual force to prevent an accidental mode change during operation of the drill, and thus the modes cannot be changed quickly in a single operation.

It is an object of the present invention to provide a mode changer mechanism capable of changing modes of operation of a powerdriven vibratory mode safely, quickly, and reliably.

According to the present invention, there is provided a power-driven drill operable selectively in a drill mode and a vibratory-drill mode, comprising: a housing; a motor shaft rotatably mounted in said housing and having gear teeth; a drill chuck drive shaft rotatably supported on said housing and having an end projecting into said housing; a gear fixed to said drive shaft and meshing with said gear teeth, said gear having first teeth; a holder fixedly mounted in said housing and supporting second teeth confronting said first teeth, said end of said drive shaft being rotatably and axially movably disposed in said holder; a ball partly received in said end of said drive shaft; and a mode changeover plate slidably extending through said holder and having a cavity in a surface thereof facing toward said end of said drive shaft, said mode changeover plate being movable between a drill-mode position in which said ball rides on said surface of the mode changeover plate to keep said first teeth out of engagement with said second teeth thereby allowing said drive shaft to rotate, without axial movement, on rotation of said motor shaft and a vibratory-drill-mode position in which said ball is fitted in said cavity to permit said first teeth to engage said second teeth thereby allowing said drive shaft to rotate and axially move on rotation of said motor shaft.

The present invention will be described in detail by way of illustrative example with reference to the accompanying drawings, in which: Figure 1 is a fragmentary longitudinal crosssectional view of power-driven vibratory drill incorporating therein a mode changeover mechanism according to the present invention; and Figure 2 is an enlarged fragmentary transverse cross-sectional view taken along line ll-il of Fig. 1.

As shown in Figs. 1 and 2, a mode changer mechanism according to the present invention is shown incorporated in a power-driven vibratory drill, generally designated at 1. The power-driven vibratory drill 1 has a housing 2 accommodating therein a motor shaft 7 extending from a motor (not shown) and rotated bly supported by a bearing 3, the motor shaft 7 having gear teeth 4 on one end thereof.

The gear teeth 4 are held in driving mesh with the teeth on a gear 8 fixedly mounted on a drive shaft 9 rotatably and axially movably supported by a bearing 5 in the housing 2.

The drive shaft 9 is coupled to a chuck (not shown) which holds a drill bit (not shown).

A holder 1 6 is fixedly mounted in the housing 2 and has a transverse groove 6 (Fig.

2) in which a rear end of the drive shaft 9 is disposed. The bearing 3 is supported in the holder 16. An annular teeth support 21 is disposed in the holder 1 6 in concentric relation to the drive shaft 9 and supports thereon a first row of circularly arranged teeth 1 7 projecting toward the gear 8. The gear 8 has a second row of circularly arranged teeth 1 5 projecting toward the first teeth 1 7 for engagement therewith.

As illustrated in Fig. 2, an elongate changeover plate 11 extends through the groove 6 transversely across the holder 1 6. The rear end of the drive shaft 9 is disposed in confronting relation to the changeover plate 11 with a steel ball 10 interposed therebetween, the steel ball 10 being partly received in a recess defined in the rear end of the drive shaft 9. The changeover plate 11 has a cavity 1 2 opening toward the rear end of the drive shaft 9 and a pair of semicircular recesses 1 3 spaced from each other and defined in a lower edge of the changeover plate 11. The changeover plate 11 is longitudinally movable through the groove 6 and supports on ends thereof a pair of pusher knobs 22, 23 which can project through opposite side walls of the housing.The pusher knobs 22, 23 have inner flanges 24, 25, respectively, disposed in the housing 2 and engageable with opposite side surfaces of the holder 1 6.

A positioning member in the form of a leaf spring 1 8 is positioned in the groove 6 and has a central U-shaped projection 21 receivable in one of the recesses 1 3 at a time for preventing the changeover plate 11 from being accidentally displaced. The leaf spring 1 8 is firmly fixed by a lateral projection 1 9 to the holder 1 6 against any unwanted wobbling movement. The holder 1 6 has a clearance space 20 defined below the groove 6. The Ushaped projection 21 is resiliently movable into the clearance space 20 to allow the changeover plate 11 to be shifted in the groove 6. Thus, the U-shaped projection 21 is prevented from being permanently deformed at the time the changeover plate 21 is moved in the groove 6.

Operation of the power-driven vibratory drill 1 will now be described. In a "drill" mode of operation, the changeover plate 11 is shifted in the groove 6 by pushing the pusher knob 23 to bring the cavity 1 2 out of alignment with the steel ball 10, whereupon the latter rides on a flat surface 14 of the changeover plate 11. At this time, the U-shaped projection 21 is fitted in one of the recesses 13, and the teeth 1 5 on the gear 8 are held out of engagement with the teeth 1 7 as shown in Fig. 1. When the motor shaft 7 is rotated, the drive shaft 9 is rotated through the gear 8, but fails to move axially due to contact between the steel ball 10 and the flat surface 14 of the changeover plate 11 even if the drill bit is pressed against a workpiece being drilled.

For a "vibratory-drill" mode of operation, the pusher knob 22 is pushed to slide the changeover plate 11 until the cavity 1 2 is positioned aligned with the steel ball 10. At this time, the U-shaped projection 21 is fitted in the other recess 1 3 as shown in Fig. 2. The drive shaft 9 is now allowed to move back as far as the steel ball 10 is received in the cavity 12, for thereby bringing the teeth 1 5 into engagement with teeth 1 7. In use, the drill bit on the drive shaft 9 is pressed against the workpiece, and, as the gear 8 is rotated by the motor shaft 7, the drive shaft 9 is caused to move axially back and forth due to alternate engagement and disengagement between the teeth 15, 1 7. Accordingly, the power-driven vibratory drill 1 now operates in the "vibratory-drill" mode.

Although a certain preferred embodiment of the present invention has been shown and described in detail, it should be understood that various changes and modifications may be made therein without departing from the scope of the appended claims.

Claims

1. A power-driven drill operable selectively in a drill mode and a vibratory-drill mode, comprising: a housing; a motor shaft rotatably mounted in said housing and having gear teeth; a drill chuck drive shaft rotatably supported on said housing and having an end projecting into said housing; a gear fixed to said drive shaft and meshing with said gear teeth, said gear having first teeth; a holder fixedly mounted in said housing and supporting second teeth confronting said first teeth, said end of said drive shaft being rotatably and axially movably disposed in said holder; a ball partly received in said end of said drive shaft; and a mode changeover plate slidably extending through said holder and having a cavity in a surface thereof facing toward said end of said drive shaft, said mode changeover plate beng movable between a drill-mode position in which said ball rides on said surface of the mode changeover plate to keep said first teeth out of engagement with said second teeth thereby allowing said drive shaft to rotate, without axial movement, on rotation of said motor shaft and a vibratory-drill-mode position in which said ball is fitted in said cavity to permit said first teeth to engage said second teeth thereby allowing said drive shaft to rotate and axially move on rotation of said motor shaft.

2. A power-driven drill according to claim 1, wherein said holder has a groove receiving said mode changeover plate, said end of said drive shaft being disposed in said groove.

3. A power-driven drill according to claim 1, wherein said changeover plate has a pair of pusher knobs attached to ends thereof and selectively depressable to move said changeover plate between said drill-mode position and said vibratory-drill-mode position.

4. A power-driven drill according to claim 1, including a member acting between said holder and said changeover plate for positioning said changeover plate in one of said drillmode and vibratory-drill-mode positions at a time.

5. A power-driven drill according to claim 4, wherein said changeover plate has a pair of recesses in an edge thereof which correspond respectively to said drill-mode and vibratorydrill-mode positions, said member comprising a leaf spring attached to said holder and having a projection resiliently receivable in one of said recesses at a time.

6. A power-driven drill according to claim 4, wherein said holder has a clearance space for receiving said projection as the latter resiliently flexes out of one of said recesses or the other when said changeover plate moves between said drill-mode and vibratory-drill-mode positions.