CA2323976A1 - Shaft extensions, adapters and shaft extension kits for hand-held power tools - Google Patents

Abstract

A shaft extension kit for a hand-held power tool having a threaded drive shaft includes a plurality of extension shafts and one or more adapter stubs. Any selected two of the extension shafts are interconnectable by any selected one of the adapter stubs, and any selected one of said extension shafts is threadingly engageable with a threaded shank of a tool accessory. If the drive shaft is externally threaded, any selected one of the extension shafts is threadingly engageable with the drive shaft. If the drive shaft is internally threaded, any selected one of the adapter stubs is threadingly engageable with the drive shaft. Such extension shafts and adapter stubs may be designed as a shaft extension kit for use, selectively, with a first hand-held power tool or a second hand held power tool, one of such tools having an externally threaded drive shaft, the other of such tools having an internally threaded drive shaft. In this case, any selected one of the adapter stubs is threadingly engageable with the internally threaded drive shaft.

Description

SHAIrT EXTENSIONS, ADAPTERS AND SHAFT
EXTENSION KITS FOR HAND-HELD POWER TOOLS
FIELD OF THE INVENTION
This invention relates to hand held power tools and, more particularly, to shaft extensions and shaft extension kits therefor to facilitate cutting operations using drill bits, countersink cutters, or other such tool accessories.
BACKGROUND TO THE INVENTION
The prior art reveals a variety of shaft extensions for power tools.
For example, U.S. Patent No. 4,076,444 (Siebrecht) granted on February 28, 1978, 1o discloses an extension kit comprising a single extension shaft, a chuck adapter fitting enabling one end of the shaft to be received by a conventional drill chuck, and a drill bit adapter fitting enabling a drill bit to be connected with the other end of the extension shaft.
However, the versatility of such a kit is limited. Further, the kit undesirably requires two different adapter fittings.
As another example, U.S. Patent No. 4,654,971 (Fettes et al.) granted on April 7, 1987 discloses a drive shaft and housing assembly that is particularly adapted for pruning trees and shrubs. The assembly includes three drive shaft housing sections which may be telescoped or extended to achieve an overall length ranging from about 5 feet to 15 feet in an example given. However, the assembly is a relatively complex construction.
Further, 2o the full weight of the assembly must be carned by the user despite what length of extension is desired.
As a further example, U.S. Patent No. 5,624,214 (Carroll) granted on April 29, 1997, discloses an adjustable drill bit extension, one end of which is adapted to fit within a conventional spindle or chuck of a power tool, the other end of which is adapted for attachment to the shank of a drill bit. It appears that the length of the extension is continuously adjustable over a range from a minimum length to a maximum length, however, the overall construction is again relatively complex, and the full weight of the extension must be carried by the user despite what length of extension is desired.
Typically, hand-held power tools will have either an externally threaded or an 3o internally threaded drive shaft. Extension arrangements of the type suggested above are generally not well adapted for compatibility with both types of drive shafts.

SU11~HARY OF THE INVENTION
It is an object of the present invention to provide a new and improved power tool extension shaft which is simple in construction and can serve to provide a connection between the drive shaft of a power tool and the shank of a drill bit or other tool accessory without the use of a chuck.
It is a further object of the present invention to provide means that enable two or more of such extension shafts to be easily and securely connected and disconnected to provide overall shaft extensions of varying lengths.
Yet another object of the present invention is to provide a shaft extension kit for a to power tool, the kit including a minimal number of differing parts which are minimally complex and enable a user to quickly assemble an extension shaft of desired length which has minimal weight.
Still another object of the present invention is to provide a shaft extension kit which may be made compatible with power tools of different types, one type having an externally threaded drive shaft, the other type having an internally threaded drive shaft.
In accordance with one aspect of the present invention, there is provided a shaft extension kit and components thereof for a hand-held power tool, the tool having a threaded drive shaft, the kit comprising a plurality of extension shafts and a plurality of adapter stubs. Any selected two of the extension shafts are interconnectable by any selected one of the adapter stubs. Any selected one of the extension shafts is threadingly engageable with a threaded shank of a tool accessory such as a drill bit, countersink cutter.
If the drive shaft is externally threaded, any selected one of the extension shafts is threadingly engageable with the drive shaft. If the drive shaft is internally threaded, any selected one of the adapter stubs is threadingly engageable with said drive shaft.
In accordance with another aspect of the present invention, there is provided a shaft extension kit and components thereof for use, selectively, with a first hand-held power tool or a second hand-held power tool. One of such tools has an externally threaded drive shaft; the other of such tools has an internally threaded drive shaft. The kit comprises a plurality of extension shafts and a plurality of adapter stubs.
Any selected 3o two of the extension shafts are interconnectable by any selected one of the adapter stubs.
In addition, any selected one of the extension shafts is threadingly engageable with a threaded shank of a tool accessory, and with the externally threaded drive shaft. Further, any selected one of the adapter stubs is threadingly engageable with the internally threaded drive shaft.

In a preferred embodiment, the kit includes at least three extension shafts of differing lengths and at least two substantially identical adapter stubs. More preferably, the combined length of a second one of the shafts and one of the adapter stubs when fully engaged therewith is approximately two times the length of a shortest one of the shafts.
Further, the combined length of a third one of the shafts and one of the adapter stubs when fully engaged therewith is approximately four times the length of a shortest one of the shafts.
In all cases, the extension shafts and the adapter stubs preferably include wrenching flats to facilitate tight threaded engagement with each other and with the to selected power tool.
The invention will now be described in more detail with reference to the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded view illustrating power tool extension shafts and adapter stubs in accordance with the present invention, together with a conventional pistol grip air drill and examples of conventional tool accessories.
FIG. 2 is a section elevation view of the minimally short extension shaft shown in FIG. 1.
FIG. 3 is a partially sectioned elevation view representative of all extension shafts shown in FIG. 1, except the minimally short extension shaft.
2o FIG. 4 is a top view representative of any one of the extension shafts shown in FIGS. 2 and 3.
FIG. 5 is an elevation view representative of any one the adapter stubs shown in FIG. 1.
FIG. 6 is a bottom view of the adapter stub shown in FIG. S.
FIG. 7 is an elevation view showing the minimally short extension shaft in FIG. 1, and any other one of the extension shafts in FIG. I, when interconnected by an adapter stub as shown in FIG. 1.
FIG. 8 is an elevation view showing any two of the extension shafts in FIG. 1, except the minimally short extension shaft, when interconnected by an adapter stub as shown in FIG. 1.

FIG. 9 is an exploded view illustrating power tool extension shafts and adapter stubs in accordance with the present invention, together with a conventional angle head air drill and examples of conventional tool accessories.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
The arrangement illustrated in FIG. 1 includes first, second, third and fourth extension shafts generally designated 10, 20, 30, 40 of differing lengths, three substantially identical adapter stubs generally designated 50, a first tool accessory or drill bit generally designated 100, a second tool accessory or countersink cutter generally designated 150, and a hand-held air operated power tool or pistol grip air drill generally to designated 200. The extension shafts and the adapter stub are shown in more detail in FIGS. 2 to 8.
Air drill 200 is a commercially available power tool. For example, see the Year 2000 - 2001, Volume 18, Catalog of U.S. Industrial Tool & Supply Company, Plymouth, MI, U.S.A., which offers such tools from a variety of sources, including Desoutter, Ingersoll Rand and Sioux. Such tools are used extensively in the aerospace industry.
As shown, air drill 200 includes a body or housing portion 201, and a drive shaft having an externally threaded distal end 202 which extends from the housing.
When trigger 203 is pulled, compressed air power from a source (not shown) is applied and the drive shaft rotates.
2o Drill bits like drill bit 100 are also commercially available: for example, the high speed threaded shank drill bits manufactured by Precision Twist Drill Co., Crystal Lake, IL, U.S.A., which are used in the aerospace industry. As shown in FIG. l, drill bit 100 has a shank including threaded end 101, hexagonal wrenching flats 102, and a drill body 103 with helical cutting grooves or flutes formed therein. It may be noted that the National Aerospace Standard (NAS) as published by the Aerospace Industries Association ~
America, Inc. contemplates either hexagonal or square wrenching flats. Under the standard, hexagonal wrenching flats are taken to be indicative of high speed performance.
Square wrenching flats are taken to be indicative of a cobalt composition.
Countersink cutters such as countersink cutter 150 are also commercially available:
3o for example, see those which are advertised in the catalog of U.S.
Industrial Tool &
Supply Company , supra. As shown in FIG. l, cutter 150 has a threaded shank 151 and a cutting body 153 with cutting surfaces formed therein. There are no wrenching flats, but the body includes a hole 152 which receives a conventional key (not shown) allowing the user to more easily tighten the accessory At any given time, a user will select and use either drill bit 100, countersink cutter 150, or some other tool accessory. The depiction of drill bit 100 and cutter 150 in FIG. 1 is merely by way of example and highlights the fact that a choice of prior art tool accessories exists.
In the prior art, a conventional drill chuck (not shown) is typically threaded on end 202 of drill 200. Then, a tool accessory such as drill bit 100, countersink cutter 150, or otherwise, is secured to the chuck with a suitable adapter (also not shown).
The chuck grips the adapter, and the adapter threadingly engages the tool accessory.
In more detail, and with reference to FIGS. 2, 3 and 4, it will be seen that extension to shafts 10, 20, 30, 40 each include an inner end with internal threads 61 and an axially aligned outer end with internal threads 63. Further, each includes an opposed pair of wrenching flats 64, 65. Apart from such flats, the transverse cross-section of each extension shaft is substantially circular.
Threads 61 of any one of shafts 10, 20, 30 or 40 are threadingly engageable with threaded end 202 of the drive shaft of tool 200. Threaded end 101 of drill bit 100, or threaded end 151 of countersink cutter 150, are threadingly engageable with threads 63 of any one of shafts 10, 20, 30 or 40.
The only substantial difference between the shafts is in their overall lengths. In a preferred embodiment, such lengths are as follows:
~ The length of shaft 20 is about two times the length of shaft 10.
~ The length of shaft 30 is about four times the length of shaft 10.
~ The length of shaft 40 is about eight times the length of shaft 10.
In the embodiment shown in FIG. 1, and with the exception of minimally short extension shaft 10, extension shafts 20, 30, 40 each include an associated elongated, narrow diameter, central portion 27, 37, 47 (as the case may be). The central portions are of varying lengths and necessarily contribute to the desired overall length of each given shaft. It is considered that actual shaft lengths of about 1 inch (2.5 cm) for shaft 10, about 2 inches (5 cm) for shaft 20, about 4 inches ( 10 cm) for shaft 30 and about 8 inches (20 cm) for shaft 40 will collectively serve many practical purposes.
Referring now to FIG. 5, each adapter stub 50 includes a first externally threaded end 51 and an axially aligned second externally threaded end 52. Threaded end 51 is threadingly engageable with threads 63 of any one of shafts 10, 20, 30 or 40.
Similarly, threaded end 52 is threadingly engageable with threads 61 of any one of shafts 10, 20, 30 _5_ or 40. As best seen in FIG. 6, adapter stub 50 also includes a pair of opposed wrenching flats 53, 54 which allow a user to tightly engage the stub with a desired shaft.
It will be understood that the threading which appears on end 51 of adapter stub 50 corresponds to that which appears on end 101 of accessory 100 (or end 151 of accessory 150). Similarly, the threading which appears on end 52 of adapter stub 50 corresponds to that which appears on end 202 of the drive shaft of tool 200.
Also, it may be noted that each extension shaft 10, 20, 30 and 40, and each adapter stub 50, includes only an opposed pair of wrenching flats because the manufacturing process is simplified, and because a pair of flats is considered to be quite adequate for 1o practical purposes.
In further detail, it will be observed that adapter stub 50 as best seen in FIG. 5 includes chamfered surfaces 56, 58 and flat annular surfaces 57, 59.
In the case of surfaces 56, 57, the size and shaping is set to match that which appears (but which is not shown in detail) at the top of threaded ends 101, 151 of tool accessories 100, 150. Also, as best seen in FIGS. 2 and 3, extension shafts 10, 20, 30, 40 include correspondingly shaped surfaces 66, 67. Surfaces 66, 67 will ultimately come into abutment with surfaces 56, 57 when an adapter stub 50 is fully threaded into one of the shafts. The same result necessarily will follow if tool accessory 100 or 150 is threaded with internal threads 63 of one of the shafts.
2o In the case of surfaces 58, 59, the shaping is set to match that which appears on correspondingly shaped surfaces 68, 69. Surfaces 68, 69 will ultimately come into abutment with surfaces 58, 59 when an adapter stub 50 is threaded with internal threads 61 of one of the shafts.
Generally, it may be noted that the primary purpose of the chamfered surfaces and related flat annular surfaces is to avoid sharp or pointed angles (viz. less than 90 degrees) at the ends of the extension shafts. The bluntness offered by flat annular surfaces reduces the risk of damage arising from careless handling.
Collectively, shafts 10, 20, 30 and 40, and adapter stubs 50, provide a shaft extension kit for power tool 200. When they are assembled from the exploded view 3o shown in FIG. l, the result is a maximally long shaft extension consisting of the series connection of shafts 10, 20, 30 and 40, and three adapter stubs 50 - all in axial alignment.
But, if a minimally short extension was desired, then the user would choose to employ only shaft 10. As well, there is a range of possible extensions between the foregoing extremes.

More particularly, in succession from minimally short to maximally long, possible extensions from end 202 of tool 200 are indicated by the following sequences where each number represents a correspondingly numbered extension shaft 10, 20, 30 or 40, or an interconnecting adapter stub 50:
s 10 (minimally short) 10+50+20 10+SO+30 l0 20+50+30 10+50+20+50+30 10+SO+40 20 + 50 + 40 15 10+50+20+50+40 30+SO+40 10+50+30+SO+40 20+50+30+50+40 10 + 50 + 20 + 50 + 30 + 50 + 40 (maximally long).
2o Where any two extension shafts are interconnected by an adapter stub S0, the order of the shafts is not critical. For example, the extension provided by 10 + 50 + 20 + 50 +
30 could equally be provided by 30 + 50 + 20 + 50 + 10, or by 20 + 50 + 10 +
50 + 30, etc.
In use, the versatility of the kit will be readily apparent. With the preferred shaft 25 lengths indicated above, the maximum possible extension will be about 15 times the minimum possible extension. Between these extremes, there are thirteen other extensions that are possible in equally spaced increments. A user merely needs to select an appropriate extension shaft to provide a desired extension, or to assemble the desired extension using an appropriate number of extension shafts and an appropriate number of 3o adapter stubs. Threads 61 of one shaft will be directly engaged with drive shaft 202.
Threads 63 of the same or another shaft will be directly engaged with the threaded shank of the desired tool accessory (viz. drill bit 100, countersink cutter 150, or otherwise). The connections between the various parts are preferably tightened by wrenching force applied to the wrenching flats that are provided.
35 Referring now to FIG. 9, the arrangement illustrated is very similar to that shown in FIG. 1, the difference being the inclusion of an additional adapter stub SO
and the substitution of a hand-held angle head air drill 300 (partially cut-away) for pistol grip air drill 200.
30 degrees or 45 degrees are commercially available.
As in the case of pistol grip air drills, angle head air drills such as drill 300 are commercially available from a variety of sources including, I1.S. Industrial Tool & Supply Company, supra, Dotco, Desoutter and Sioux: see catalog of U.S. Industrial Tool &
Supply Company, supra. Air drill 300 shows a 90 degree angle, but other angles such as As shown, air drill 300 includes a drive shaft 303 extending from a housing 301.
Drive shaft 303 has internal threads (not shown) and is shaped and sized to enable commercially available tool accessories such as drill bit 100 or countersink cutter 150 to be engaged directly with the shaft. As is also shown, an adapter stub SO
alternatively may be engaged directly with shaft 303. The remaining adapter stubs 50 and extension shafts 10, 20, 30, 40 shown in FIG. 9 are arranged in the manner as shown in FIG. 1.
But, it will be readily understood that they may be arranged and rearranged in various combinations in the manner described above to achieve shaft extensions of varying lengths from air drill 300.
Thus, it will be appreciated that extension shafts and adapter stubs in accordance with the present invention may be provided as a kit to enable a variable length extension from either an externally threaded power tool drive shaft (e.g. the drive shaft of power tool 200) or an internally threaded power tool drive shaft (e.g. the drive shaft of power tool 300).
Various modifications and changes to the embodiments that have been described can be made without departing from the scope of the present invention, and will undoubtedly occur to those skilled in the art. The invention is not to be construed as limited to the particular embodiments illustrated in the drawings, and should be understood as encompassing all those embodiments that are within the spirit and scope ~
the claims that follow.
_g_

Claims (19)

1. A shaft extension kit for a hand-held power tool, said tool having a threaded drive shaft, said kit comprising a plurality of extension shafts and a plurality of adapter stubs, any selected two of said extension shafts being interconnectable by any selected one of said adapter stubs, any selected one of said extension shafts being threadingly engageable with a threaded shank of a tool accessory, and wherein:
(a) if said threaded drive shaft is externally threaded, any selected one of said extension shafts is threadingly engageable with said drive shaft; and, (b) if said threaded drive shaft is internally threaded, any selected one of said adapter stubs is threadingly engageable with said drive shaft.

2. A shaft extension kit as defined in claim 1, wherein a second one of said shafts has a length longer than a first one of said shafts.

3. A shaft extension kit as defined in claim 1, comprising at least three extension shafts of differing lengths and at least two substantially identical adapter stubs.

4. A shaft extension kit as defined in claim 3, wherein the length of a second one of said shafts is substantially two times the length of a shortest one of said shafts.

5. A shaft extension kit as defined in claim 4, wherein the length of a third one of said shafts is substantially four times the length of a shortest one of said shafts.

6. A shaft extension kit as defined in claim 5, wherein the length of a fourth one of said shafts is substantially eight times the length of a shortest one of said shafts.

7. A shaft extension kit for use, selectively, with a first hand-held power tool or a second hand-held power tool, one of such tools having an externally threaded drive shaft, the other of such tools having an internally threaded drive shaft, said kit comprising a plurality of extension shafts and a plurality of adapter stubs, any selected two of said extension shafts being interconnectable by any selected one of said adapter stubs, and wherein:
(a) any selected one of said extension shafts is threadingly engageable with:
(i) a threaded shank of a tool accessory; and, (ii) said externally threaded drive shaft;

(b) any selected one of said adapter stubs is threadingly engageable with said internally threaded drive shaft.

8. A shaft extension kit as defined in claim 7, wherein a second one of said shafts has a length longer than a first one of said shafts.

9. A shaft extension kit as defined in claim 7, comprising at least three extension shafts of differing lengths and at least two substantially identical adapter stubs.

10. A shaft extension kit as defined in claim 9, wherein the length of a second one of said shafts is substantially two times the length of a shortest one of said shafts.

11. A shaft extension kit as defined in claim 10, wherein the length of a third one of said shafts is substantially four times the length of a shortest one of said shafts.

12. A shaft extension kit as defined in claim 11, wherein the length of a fourth one of said shafts is substantially eight times the length of a shortest one of said shafts.

13. A shaft extension kit as defined in any one of claims 1 to 12 wherein each of said extension shafts includes wrenching flats, and wherein each of said adapter stubs includes wrenching flats.

14. An extension shaft as defined in claim 1 for a shaft extension kit as defined in claim 1.

15. An extension shaft as defined in claim 7 for a shaft extension kit as defined in claim 1.

16. An extension shaft as defined in claim 14 or 15, said extension shaft including wrenching flats.

17. An adapter stub as defined in claim 1 for a shaft extension kit as defined in claim 1.

18. An adapter stub as defined in claim 7 for a shaft extension kit as defined in claim 1.

19. An adapter stub as defined in claim 17 or 18, said adapter stub including wrenching flats.