US 3730281 A
A drill:hammer-drill arrangement is provided for a portable power tool wherein the hammering teeth are located immediately adjacent the chuck portion of the tool and wherein one set of hammering teeth are carried by the shaft which drives the chuck. A spring is provided which biases the chuck and the rotational hammer teeth forwardly relative to the tool during hammering while another spring biasses the stationary teeth toward the tool. In the hammer position, operator bias overcomes the spring force to engage the teeth and relative rotation causes hammering. In shifting into the drill position, a cam surface forces the chuck and the shaft on which the hammer teeth are mounted toward the tool until the shaft engages the forward bearing on the output spindle of the tool. Thus the forward bearing takes the thrust applied against the tool by the operator during drilling and eliminates the need for an independent thrust bearing.
Description (OCR text may contain errors)
United States Patent 91 Wood 1 [s 1 DRILL HAMMER-DRILL MECHANISM FOR POWER TOOL John W. Wood, Baltimore, Md.
Assignee: The Black and Decker Manufacturing Company, Towson, Md.
Filedz' June 7, 1971 Appl. No.: 150,339
U.S. Cl. ..173/48, 74/22 Int. Cl. ..B25d 11/10, E2lc l/l2 Field of Search l 73/48, 109; 74/22 References Cited UNITED STATES PATENTS 3/1969 Bitter et a] ..74/22 M1964 Short ..173/4sx Primary EXaminerErnest R. Purser Attorney-Leonard Bloom, Joseph R. Slotnik and Edward D. Murphy I [451! May 1, 1973 [5 7] ABSTRACT A drillzhammer-drill arrangement is provided for a portable power tool wherein the hammering teeth are located immediately adjacent the: chuck portion of the tool and wherein one set of hammering teeth are carried by the shaft which drives the chuck. A spring is provided which biases the chuck and the rotational hammer teeth forwardly relative to the tool during hammering while another spring biasses the stationary teeth toward the tool. in the hammer position, operator bias overcomes the spring force to engage the teeth and relative rotation causes hammering. In shiftagainst the tool by the operator during drilling and eliminates the need for an independent thrust bearing.
13 Claims, 3 Drawing Figures Patented May 1, 1973 3,730,281
DRILL HAMMER-DRILL MECHANISM FOR POWER TOOL The present invention is directed to an improved power tool and specifically relates to an improved power drill which is capable of performing both drilling and hammer-drilling.
In the class of power tools such as drills which are commonly sold'to homeowners and other light-duty users of such tools, there is a need for a tool which has a wide variety of capabilities so that the user does not need to purchase a separate tool for each of the various jobs he may wish to do. For example, while drilling operations are most commonly performed in wood or metal, the homeowner may occasionally wish to drill in more difficult materials such as concrete, brick, ceram ic tile, etc. Accordingly, it is desirable to provide a power drill which can be converted easily from straight drilling to hammer-drilling on these occasions. However, since the need for this is relatively infrequent, it is also desirableto minimize the cost premium which the purchaser must pay to obtain the hammer-drilling-option. It is therefore the purpose of this invention to provide a drill head for a power tool which is quickly and easily convertible between drilling and hammerdrilling, which is improved and simplified in construction and which is of less cost than previous units of this type.
Accordingly, it is an object of the present invention to provide a new, and improved construction for a drill:hammer-drill tool.
A further object of this invention is the provision of an inexpensive drillzhammer-dril] device.
Another object of this invention is the provision of an improved hammer-drill mechanism whichpermits increased impacting force at the output.
A further object of this invention is the provision of an improved drilling thrust takeup in a drill:hammerdrill construction.
Further objects and advantages of this invention will become apparent as the description and illustration thereof proceed.
Briefly, in accord with one embodiment of this invention, a drillzhamm er-drill arrangement is provided for a portable power tool wherein the hammering teeth are located immediately adjacent the chuck portion of the tool and wherein one set of hammering teeth are carried by the shaft which drives the chuck. A spring is provided which biases the chuck and the rotational hammer .teeth forwardly relative to the tool during hammering while another spring biasses the stationary teeth toward the tool. In the hammer position, operator bias overcomes the spring force to engage the teeth and relative rotation causes hammering. In shifting into the drill position, a cam surface forces the chuck and the shaft on which the hammer teeth are mounted toward the tool until the shaft engages the forward bearing on the output spindle of the tool. Thus the forward bearing takes the thrust applied against the tool by the operator during drilling and eliminates the need for an independent thrust bearing. In the drawings:
FIG. I is a side elevation view of a power tool embodying the present invention;
FIG. 2 is a detailed view partially in cross section of the tool of FIG. I in a first operative position; and
FIG. 3 is a view similar to that: of FIG. 2 but showing the tool in a second operative position.
In FIG. 1, a power tool 10 is illustrated which includes a housing 11 covering, for example, an electric motor and a handle portion 12 which includes a cord set 13 for application of electric power to the motor and a trigger switch 14 for switching the tool on and off. A gear case 15 is provided at the front end of the motor for converting the rotation of the electric motor to an appropriate speed to drive the chuck l6 and an output tool such as drill bit 17. Preferably, the chuck is attached to the main bodyof thetool by an attachment coupling assembly such as that described in my copending application Ser. No. 150,344, filed June 7, 1971 which is assigned to the assignee of this invention. As described in that application, the attachment is engaged with the tool by inserting a bayonet member 18 on the attachment into a corresponding coupling member 19 on the tool.
The specific subject matter of' the present invention is shown more clearly in FIGS. 2 and 3. This mechanism is referred to hereinafter as an attachment, although it may be used either in the form of an attachment or in the form of a permanently mounted part of a tool. In FIG. 2, the drillzhammer-drill attachment 20 is illustrated in a first position wherein it is adapted for drilling only. In the context of the attachment coupling referred. toabove, this position may be defined by providing a step 21 in the bayonet teeth 22 which are inserted into the coupling member 19. Thus, upon inserting the attachment and rotating it, the step 21 engages with corresponding lugs 23 on the coupling member and a lock button 24, carried by the coupling member 19, engages with a slot in the attachment, as is more completely described in my aforementioned application. l
The teeth 22 are carried on a coupling member 25 which is engaged with a carrier 26 of one set of hammer teeth 27 via spring 28. The coupling member 25 extends radially inward to retain the carrier 29 of the other set of hammer teeth 30. A stationary gripping ring 31 is also engaged with the coupling member 25 so that the operator can grasp it to insert and rotate the teeth 22.
In my aforementioned application, the concept of spring biasing the attachment to the power unit is described. It is noted that the spring 28 represents an alternative embodiment of this biasing. Specifically, when the teeth 22 or step portions 2l engage with the lugs 23 on coupling member 19, the coupling member 25 is drawn toward the tool. Since this member is coupled to the attachment via spring .28, the spring force is exerted to draw the tool and the attachment into tighter engagement, in the manner described and claimed in that application.
Thus, the stationary part of the attachment includes gripping ring 31, coupling member 25 and carrier 26. These parts are engaged with the stationary outer members of the tool. The rotational portion of the attachment includes chuck 16 which is threaded on to a shaft 35. In turn, the shaft 35 is adapted to be engaged with the output shaft 36 extending from gear case 15.
- For example, the output shaft may include a cylindrical portion 37 for piloting the chuck and a hexagonal por- 5 tion 38 for providing a positive drive coupling. The stationary and rotational parts of the tool are coupled via bearing 39 and, due to the improved piloting provided in this arrangement, as described in my aforementioned application, no further bearing surface is required in the attachment portion.
The carrier 29 is press fitted on to the shaft 35 and rests against a shoulder 40 formed on the shaft. Thus, this carrier and the hammer teeth 30 thereon are carried by and move with the shaft 35. In accord with the present invention, the drilling mode of operation is provided by moving the entire attachment assembly inwardly into the coupling member 19 until the leading end 41 of shaft 35 engages with inner race 42 of bearing 39. In order to accomplish this movement, the step 21 in the coupling teeth 22 is axially positionedso that engagement thereof with the lugs 23 necessarily draws the shaft 35 into engagement with the bearing 39. Thus, in theposition illustrated in FIG. 2, operator thrust on the tool is absorbed by the bearing 39. Since the shaft 35 cannot move further into the tool, the hammer teeth 30 and 27 can never come into engagement and no hammering action will occur. The rotary motion of the output shaft 36 is transmitted to the chuck 16 and to any implement therein such as bit 17 and the unit will function as a simple drill.
To produce hammering action, it is necessary to permit the teeth 27 and 30 to come into engagement. In accordance with conventional hammer-drill construction, one set of teeth, 27, is stationary while the other set, 30, rotates with the chuck. The leading edges of the sets of teeth are cammed so that, as the chuckand set 30 rotate, the main body of the tool is lifted a distance corresponding to the axial depth of the two sets of teeth. As the set 30 continues to rotate, it moves out of engagement with set 27, thus permitting the force of the operator pressure against the back of the tool to bang the tool forwardly, thus producing a hammering action on the work as the chuck rotates. Spring 43 is placed within the chuck to bias the chuck forwardly while spring 28 biases the stationary part into piloting engagement with the tool.
FIG. 3 illustrates the tool of this invention in a position where hammering can occur. Specifically, the teeth 22 have been rotated so that the step 21 has passed out of engagement with the lugs 23. As soon as the step moves beyond the lugs, the force of spring 43 moves the entire attachment forwardly with respect to the rest of the drill. Thus, shaft 35 moves away from bearing 39 and the hammer teeth set 30 is now free to move, either outwardly under the influence of spring 43 or inwardly when the operator overcomes this bias by pressing the tool against the work. To accommodate the relative movement of the hammer teeth 30, the hammer teeth 27 must also move outwardly so that they can be engaged by hammer teeth 30 in the position of FIG. 3 and inwardly so that they cannot be engaged thereby in the position of FIG. 2. To accomplish this movement, a set of stationary teeth 44 are provided at the forward end of the tool and a corresponding set 45 is provided onthe rearwardly facing surface of the carrier 26. Thus, as the drillzhammer-drill device is rotated so that the step 21 moves out of engagement with the coupling member- 19, the teeth 45 are also being rotated to ride up on to teeth 44.
To summarize the operation of converting the tool from drilling to hammer-drilling, the lock button 24 is depressed to disengage it from the hammer-drill mechanism and then the gripping ring 31 is twisted relative to the coupling member 19. The step 21 moves out of engagement with the coupling member 19 and the spring 43 therefore draws the mechanism away from the body of the tool by means of its pressure against the forward end of shaft 36. The shaft 35, carrier 29 and teeth 30 are simply pulled forwardly by the spring 43 for a distance corresponding to the height of step 21. At the same time, the stationary teeth 44 and 45 ride on interacting cam surfaces so that the carrier 26 is moved outwardly a distance corresponding to the movement of the rotationary teeth 30 and carrier 29. When these motions have been completed, the lock button 24 engages another slot in the gripping ring 31. Reverse rotation converts the tool back to the drilling mode.
Due to the movement of the hammer teeth sets as described, the end 41 of shaft 35 is now spaced from the inner race 42 of bearing 39. Thus, when the operator presses the tool against an object to be drilled such as a concrete block, etc., the chuck 16, the shaft 35, the carrier 29 and the teeth 30 can all be moved rearwardly against the force of spring 43 to engage the stationary teeth 27 and thus produce hammering action in the manner described above. At the same time, accurate piloting of the stationary portion of the attachment is maintained by the engagement between flat surfaces on teeth 44 and 45 and piloting of the rotational portion of the attachment is maintained by the engagement of shaft 35 with shaft 36.
The construction of a drillzhammer-drill mechanism as described above, embodies several advantages which are of particular importance. For example, the location of the hammer jaws at an extreme forward position immediately adjacent the chuck enables the full mass of the tool to be applied to generate the hammering action. In addition, since the hammer jaws are located immediately adjacent the chuck rather than in the main body of the tool, the number of interfaces and other energy absorbers between the hammer. jaws and the work reduced, a larger quantity of the energy contained in the shockwave generated at the hammer jaws is actually transmitted to the work. Another advantage of this construction is that of taking up the thrust in the drilling mode on a bearing which is required for rotational-to-stationary coupling, thus eliminating the need for an independent thrust-take up member which would add to the cost and complexity of the unit. In the specific case of a power driver with a variety of attachments, it is of particular advantage to provide the hammer mechanism in the attachment since this reduces the cost of the basic driver unit to those who have no need for the hammering action while at the same time enabling this function to be readily available to those who have need for it.
Accordingly, while a specific embodiment of this invention has been described and illustrated, it will be clear to those skilled in the art that many changes and modifications may be made from this embodiment without departing from the broader aspects of this invention. Accordingly, it is intended that the appended claims cover all such changes and modifications as fall within the true spirit and scope of this invention.
1. In a power drill having a motor, an output shaft driven by said motor, at least a forward bearing supporting said output shaft, and a stationary bearing mount for said bearing; a mechanism arranged for conversion between the operations of drilling and hammermember engages a rotating portion of said bearing and a second position wherein said drive member is spaced from said bearing, whereby in said first position, thrust applied between said tool and a workpiece is taken up by said bearing and in said second position, thrust applied between said tool and a workpiece is effective to cause engagement of said sets of hammer teeth.
2. Apparatus as claimed in claim 1 wherein said bearing comprises an anti-friction bearing having an inner race mounted on said output shaft and wherein said drive member in said first position engages said inner race.
3. Apparatus as claimed in claim 2 wherein said bearing comprises a ball bearing, said ball bearing having an inner race mounted on said output shaft.
4. Apparatus as claimed in claim 3 wherein said drive I member comprises a sleeve mounted in torque-transmitting engagement with said output shaft.
5. Apparatus as claimed in claim 1 wherein said means for moving said drive member comprises means biasing said mechanism away from said output shaft.
6. Apparatus as claimed in claim 5 wherein said rotary hammer teeth are affixed to and rotate with said drive member.
7. Apparatus as claimed in claim 6 wherein said means for moving said drive member further comprises second position, said stationary hammer teeth being moved axially forward along said output shaft; the movement of said drive member from said bearing mount to said second position being sufficient to permit engagement of said rotary teeth with said stationary teeth when thrust is applied between said tool and a workpiece.
8. In a power drill having a motor, an output shaft driven by said motor, at least a forward bearing supporting said output shaft and a stationary bearing output shaft between a first position wherein said drive mount for said bearing; a mechanism arranged for conversion between the operations of drilling and hammerdrilling comprising a drive member for said drive mechanism, said drive member being slideably engaged with said output shaft, a rotary set of hammer teeth mounted on said drive member; a stationary set of member enga es a rotating portion of said bearing and a second post ion wherein said drive member is spaced from said bearing, whereby in said first position, thrust applied between said tool and a workpiece is taken up by said bearing and in said second position, thrust applied between said tool and a workpiece is effective to cause engagement of said sets of hammer teeth; said means for moving said drive member comprising means biasing said mechanism away from said output shaft, at least one axially stepped tooth, each of said stepped surfaces being engageable with an opposed surface to define a relative axial location therebetween, said opposed surface being mounted on a stationary member retaining said bearing; said stepped tooth being positioned to cooperate with said means for moving said drive member so that engagement of one of said stepped surfaces with said opposed surface permits movement of said drive member to said first position and engagement of said other stepped surface with said opposed surface permits movement of said drive member to said second position.
9. Apparatus as claimed in claim 8 wherein at least one of said hammer teeth sets :moves with said drive member.
10. Apparatus as claimed in claim 9 wherein said biasing means produces a force moving said drive member and said rotary hammer teeth away from said motor and wherein further means are provided to move said stationary hammer teeth away from said motor.
11. Apparatus as claimed in claim 10 wherein said bearing comprises an anti-friction bearing.
12. Apparatus as claimed in claim 11 wherein said mechanism further includes locking means for retaining said mechanism in either of said positions.
13. An attachment for use with a power unit including a housing, a motor contained within said housing, an output shaft extending from said motor and supported in a bearing, said bearing being mounted in said housing, said attachment being adapted for alternative- 1y performing drilling and hammer-drilling, said attachment comprising a plurality of stepped teeth arranged for engagement with said housing; a drive member for driving engagement with said output shaft; a first set of rotary hammer teeth engaged with said drive member; a second set of stationary hammer teeth coupled to said stepped teeth; means for biasing said attachment away from said output shaft; one surface of said stepped teeth being effective, upon engagement with said housing, to overcome said biasing means to position said attachment in a first position close to said tool, said drive member engaging a portion of said bearing in said first position to prevent engagement of said rotary and said stationary hammer teeth; and a second surface on said stepped teeth effective, upon engagement with said housing, to permit movement of said attachment away from said tool to a second posi-