Hammer Drill With Slidable Rotation Gear And Lock

Abstract

An electric hammer drill is constructed to provide both striking and rotating motions for a tool mounted in the drill. Further, the rotational motion is provided by a gear wheel which, in turn, is driven by a pinion. If only striking motion is to be transmitted to the tool, the gear wheel can be disengaged from the pinion and, if required, the gear wheel in its disengaged position can be locked against rotational movement. The gear wheel is normally biased into engagement with the pinion. An operating lever is positioned on the hammer drill for selecting the desired arrangement of the gear wheel.

Description

SUMMARY OF THE INVENTION

The invention is directed to an electric hammer drill in which the driving force has two components, one for effecting a striking or impact movement of a tool mounted in the drill and the other for imparting a rotational movement to the tool and, more particularly, it concerns the arrangement of a gear wheel engageably with a pinion for effecting the rotational movement and disengageable from the pinion when the driving force is transmitted only in the form of a striking movement.

Hammer drills of the type mentioned above, are practically unlimited in their uses. Frequently such hammer drills are used for inserting rapid core drill anchors and for chipping. When the drills are used for chipping as well as for setting rapid core drill anchors, particularly during the initial part of the drilling action and when driving in the expansion body, only a striking or impact movement is provided on the tool. Therefore, it is necessary that the rotational movement of the hammer drill be discontinued so that only the striking movement can be performed.

Though it is known to shut off the rotational movement in the above-mentioned operations, certain shortcomings have been experienced.

For example, for setting rapid core drill anchors it has been necessary to use a special attachment which can be inserted into the tool holder of the hammer drill. Naturally, when such an additional element is attached to the hammer drill it is hindering in many respects, in particular, it is susceptible of difficulties, because it is subject to extensive contamination. Moreover, when an additional element is positioned between the tool carrier and the tool itself, a certain reduction in the performance or efficiency of the drill is experienced. When a chisel has been used with a hammer drill, the discontinuance of the rotational movement was solved in a cumbersome manner in the past. As presently known, when no rotational movement is desired when using a chisel, the chisels are provided with round instead of rectangular or hexagonal shanks. When a round shank is used, it has the result of preventing a form-closed connection between the tool and the tool holder and, as a result, there is no transmission of rotary motion to the tool. Such an arrangement for shutting off rotational movement has an adverse effect, because it is necessary to use tools with differently shaped shanks in various operations. Further, when a chisel with a round shank is used, it causes considerable wear of the tool holder normally provided with a rectangular or hexagonal opening.

Therefore, it is the primary object of the present invention to provide a hammer drill in which rotational movement can be discontinued within the drill itself without the use of auxiliary means for the connection of the tool within the tool holder.

In accordance with the present invention, for effecting rotational movement of the drill, a gear wheel is arranged to be driven by a pinion so that it can be displaced axially of the drill relative to the pinion for shutting off the rotational movement of the drill.

This feature of the axial displacement of the gear wheel has the advantage that it can be effected by a simple manipulation of the hammer drill itself. The ability to switch between the combination of striking and rotational movement and pure striking movement is of particular advantage in setting rapid core drill anchors, since an accurate insertion is frequently only possible when the anchor is driven into the target material under a pure impacting action before the actual insertion process is effected which is performed by a combination of rotational and striking movements. By incorporating all of the switching elements within the casing of the hammer drill, the engagement and disengagement of the gear wheel and the pinion can be performed completely independently of external influences.

To assure the meshed engagement of the gear wheel with the pinion, a compression spring is arranged in contact with the gear wheel for biasing it toward the driving pinion.

Preferably, the engagement and disengagement of the gear wheel with the driving pinion is effected by means of a slide positioned within the hammer drill casing which can be displaced in the direction of the tool axis of the drill.

For locking the gear wheel against rotational movement when it is uncoupled or disengaged from the driving pinion, a locking element is associated with the slide, movable in the direction of the tool axis, for holding the gear wheel against rotational movement. With this arrangement it is possible to prevent the tool from rotating when it is desired to provide only a striking or impact action by the tool. For example, when using chisels, the tool can be guided directly with the lateral handle of the hammer drill, so that a chisel handle, which frequently causes pain to the hands because of vibrations, can be eliminated. By providing separate members for effecting the disengagement of the gear wheel from its driving pinion an then for locking the gear wheel against rotational movement, it is possible when using a chisel to turn it into the desired position after the gear wheel disengagement is effected and then to lock it into the desired position by means of the locking member.

For locking the gear wheel when it is disengaged from the driving pinion, the locking member is arranged so that it engages the teeth of the gear wheel. Accordingly, the locking element can be provided with cams or with an arrangement of teeth which correspond to the teeth on the gear wheel.

To ensure a rapid and reliable changeover between rotational and nonrotational movement, as well as in locking the tool against rotational movement, an operating lever is provided on the exterior of the drill casing for axially displacing the members within the casing which effect the displacement of the gear wheel from engagement with the driving pinion. When usch an operating lever is used, it is also possible to provide markings on the drill casing so that the position of the gear wheel can be easily determined.

Preferably, the operating lever has a cam which extends into the casing and engages within slots in the members which effect the displacement and locking of the gear wheel. The slots are arranged so that in movement of the operating lever from the position where the gear wheel and driving pinion are engaged, initially the gear wheel is uncoupled and the tool can still be rotated and in the subsequent movement of the lever the gear wheel is locked so that the tool cannot be rotated. When the operating lever is moved in the opposite direction, initially the cam releases the locking action and then permits the spring to bias the gear wheel into engagement with the driving pinion. Due to these automatic operations, disengagement-locking, unlocking-engagement, faulty control of the hammer drill is impossible, that is, it is not possible to lock the gear wheel as long as it remains in meshed engagement with the driving pinion.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a side view, partly in section, of a hammer drill embodying the present invention;

FIG. 2 is a top view of a portion of the hammer drill shown in FIG. 1;

FIG. 3 is a partial sectional view, similar to FIG. 1, showing certain of the parts within the drill displaced into a second position, as compared to that shown in FIG. 1;

FIG. 4 is a view, similar to FIG. 2, showing the corresponding arrangement of certain of the displaced parts in FIG. 3;

FIG. 5 is a partial view, similar to FIG. 3, but with certain of the parts within the hammer drill displaced into a third position;

FIG. 6 is a view similar to FIGS. 2 and 4 indicating the displaced arrangement of the parts shown in FIG. 5;

FIG. 7 is a view taken along the line VII--VII in FIG. 1; and

FIG. 8 is a partial top view of the hammer drill as viewed in the direction of the arrow A in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, a hammer drill consists of a motor casing 1 attached to a gear casing 2 with a handle 3 extending from the two casings and containing a pushbutton switch 4. The motor within the casing is arranged to provide a driving force to the drill having a striking or impact component and a rotational component. The driving force of the motor is tranmitted from the driving pinion 1a to a gear wheel 5 fixed on a crank shaft 7. The crank shaft is rotationally supported within the gear casing 2 within a bearing 6 and gear teeth 7a on the crank shaft mesh with the teeth on a gear wheel 8 positioned laterally of the crank shaft. The gear wheel 8 is secured on a bevel pinion shaft 10 supported in a bearing 9 in the gear casing 2. One end of the shaft 10 is mounted in the end face 1b of the motor casing 1 while its other end forms a bevel pinion 11 shown in meshed engagement with a gear wheel 12 in FIG. 1.

As the crank shaft 7 is rotated, it provides a reciprocating motion by means of crank pin 7b to a connecting rod 13 extending into one end of a cylinder 14 located within the gear casing 2. Within the cylinder 14, a piston 15 is mounted on the opposite end of the connecting rod from the crank pin 7 and is spaced in the axial direction of the cylinder from a piston 16 by a chamber 17 extending between the two pistons. The chamber 17 contains an air cushion so that the reciprocating action of the piston 15 is transmitted to the piston 16. The kinetic energy of the piston 16 is transmitted by way of its piston shaft 16b to the shank of a tool 19 positioned within the tool holder 18. The tool 19 is secured in the tool holder 18 in a known manner, for example, by means of locking elements for effecting longitudinal displacement while holding the tool against rotation.

The transmission of rotational movement to the tool 19 is provided by means of the cylinder 14 secured to the tool holder 18 and extending rearwardly into the gear casing 2 of the hammer drill. Within the gear casing 2, the cylinder 14 is rotatably mounted in bearings 20, 21 for performing the rotational movement transmitted to the cylinder 14 from the gear wheel 12 concentrically mounted on the cylinder. A key 22 affords then nonrotatable connection of the gear wheel 12 of the cylinder 14. However, the gear wheel is mounted on the cylinder 14 so that it can be displaced in the axial direction of the cylinder and a spring 23 encircling the cylinder normally biases the gear wheel into meshed engagement with the pinion 11.

On the rearward end of the cylinder 14 is a slidably displaceable ring 24 which is in contact with the rearward end of the gear wheel 12. In contact with the rearward end of the ring 24, that is the opposite end from the one in contact with the gear wheel 12, is a slide 25 displaceable in the axial direction of the cylinder 14. Located above the slide 25 is a locking member or element 26. As can be seen in FIGS. 2, 4 and 6, each of the slide 25 and the locking element 26 contain an oval-shaped slot 25a, 26a, respectively. Positioned on the exterior of the gear casing 2 is a operating lever 28 having an eccentrically arranged cam 27 which extends downwardly into the slots 25a, 26a. The operating lever 28 is pivotally mounted on the casing so that as it pivots or rotates the eccentrically arranged cam 27 effects an axial displacement of the slide 25 and the locking element 26. At its forward end, that is the end adjacent the gear wheel 12, the locking element 26 is rounded and has teeth 26b arranged to mesh with the teeth on the gear wheel, note FIG. 7. In FIG. 1 a locking element 30, loaded by a spring 29, is arranged in the operating lever 28. By providing corresponding recesses in the gear casing 2 for the locking element 30, it is possible to lock the operating lever in different lever positions, note FIG. 8. Based on the different arrangements shown in the drawing, the four different operations of the hammer drill will be described.

In FIG. 1, the hammer drill is shown corresponding to the operating lever position I illustrated in FIG. 8. In position I, the gear wheel 12 is in meshed engagement with the pinion 11, accordingly, striking or impact movements are transmitted over the crank shaft 7 and the connecting rod 13 and rotational movement is transmitted over pinion shaft 10 from pinion 11 to gear wheel 12 which rotates the cylinder 14.

In the arrangement of the hammer drill as shown in FIG. 1, the locking element 26 is shown with its rearward end aligned above the rearward end of the slide and its forward end displaced rearwardly from the gear wheel 12. The forward end of the slide 25 contacts the ring 24 which in turn is in contact with the rearward end of the gear wheel 12, that is the end which is in meshed engagement, in FIG. 1, with the pinion 11. As shown in FIG. 2, the cam 27 is positioned at one end of the slots 25a, 26a which extend obliquely to one another and to the axial direction of the cylinder 14 in the hammer drill.

In FIG. 3 the operating lever is in position II, as shown in FIG. 8, and the slide has been moved axially toward the tool holder so that the ring 24 sliding on the cylinder 14 has displaced the gear wheel 12 forwardly out of meshed engagement with the pinion 11. Accordingly, it is not possible for the motor to transmit rotational movement to the cylinder 14 and in this arrangement only a striking or impact action is transmitted by the piston 16 and its shaft 16b to the tool 19. In this position the cylinder 14 and gear wheel 12 can be turned at random along with the tool 19, so that the tool can be located in a desired position by manually rotating the tool holder 18.

In FIG. 4 the position of the slide 25 and locking element 26 are shown corresponding to the lever position II as shown in FIG. 3. As can be seen in FIG. 4, the cam 25 has moved from the ends of the slots 25a, 26a to an intermediate position, thereby displacing the slide and locking element relative to one another

In FIG. 5 the hammer drill is arranged in correspondence with lever position III illustrated in FIG. 8. As can be seen in FIG. 5, the gear wheel 12 is displaced axially from the pinion 11 so that, as in FIG. 3, only a striking action on the tool 19 can be effected. However, in FIG. 5, as compared to FIG. 3, the locking element has been displaced forwardly by the cam 27 on the operating lever so that its teeth 26b are in meshed engagement with the teeth on the gear wheel and the gear wheel 12, the cylinder 14 and the tool 19 are secured against rotational movement. This particular position is especially suitable for using the hammer drill with chisels, since the chisel within the tool holder 18 can be guided by the hammer drill without the use of a chisel handle, because the tool is prevented from rotating.

In FIG. 6 the cam 27 corresponding to operating lever position III has moved to the opposite ends of the slots 25a, 26a as compared to that shown in FIG. 5. Accordingly, the relative positions of the slide 25 and the locking element 26 have been changed.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

Claims

What is claimed is:

1. Electric hammer drill for imparting rotating and striking motion to a tool positioned in the drill comprises a casing, a cylinder positioned within the casing and extending in the axial direction of the rotating and striking motion, piston means within said cylinder for imparting the striking motion to the tool, a gear wheel disposed concentrically of and fitted on said cylinder, a pinion arranged to be disposed in meshed engagement with said gear wheel for rotating said gear wheel, drive means operatively associated with said piston means and said pinion for transmitting the striking and rotating motion thereto, wherein the improvement comprises that said gear wheel is slidably mounted on said cylinder for movement in the axial direction thereof, first means for biasing said gear wheel into meshed engagement with said pinion and second means for displacing said gear wheel from meshed engagement with said pinion.

2. Hammer drill, as set forth in claim 1, wherein said first means comprises an axially extending spring located within said casing encircling said cylinder, said spring disposed in contact with said gear wheel on the side thereof spaced from said pinion for biasing said gear wheel toward said pinion.

3. Electric drill hammer, as set forth in claim 2, wherein said second means for displacing said gear wheel from meshed engagement includes a slide member located within said casing and displaceable in the axial direction of the rotating and striking motion for displacing said gear wheel from engagement with said pinion, and said slide located on the opposite side of said gear wheel from said spring.

4. Electric hammer drill, as set forth in claim 3, wherein said second means for displacing said gear wheel from meshed engagement includes a locking element displaceable in the same direction as said slide for locking said gear wheel against rotational movement when it is displaced from meshed engagement with said pinion.

5. Electric hammer drill, as set forth in claim 4, wherein said locking element has teeth thereon in the end directed toward said gear wheel and said teeth are arranged to engage the teeth in said gear wheel for preventing it from rotating.

6. Electric hammer drill, as set forth in claim 5, wherein an operating lever is pivotally mounted on said casing and is in operative engagement with said slide and locking element for selectively positioning them in accordance with the desired movement to be imparted to the tool.

7. Electric drill hammer, as set forth in claim 6, wherein each of said slide member and locking element has a slot extending obliquely of the axial direction of said cylinder and of one another, and a cam eccentrically arranged on said operating lever and extending through each of said slots for axially displacing said slide member and said locking element as said operating lever is pivoted on said casing.

8. Electric hammer drill, as set forth in claim 7, wherein said locking element is superposed on said slide member and said slide member and locking element are axially displaceable relative to one another.

9. Electric drill hammer, as set forth in claim 8, wherein a key is arranged for securing said gear wheel to said cylinder for preventing rotational movement of said gear wheel relative to said cylinder and for affording axial movement of said gear wheel relative to said cylinder.

10. Electric hammer drill, as set forth in claim 9, wherein a ring is slidably mounted on said cylinder between said gear wheel and said slide member for transmitting the axial movement of said slide member toward said gear wheel to said gear wheel.