Abstract:
A nail extractor advances a spinning drill tube into wood closely around the head of a nail to be extracted. As the drill tube advances into the wood around the nail, it compresses a drilled core of wood between the nail and the inside of the drilling tube. As this compressed core of drilled wood deepens or lengthens, it engages and rotates the nail, spinning the nail free from the wood in which it has been embedded. The spinning drill tube can then be removed with the nail and the compressed core of drilled wood, without touching the nail with the extractor tool. The nail is then preferably ejected from the drill tube by advancing an ejector pin into the drill tube.

Description:
TECHNICAL FIELD 
     The art of pulling or removing nails from wood. 
     BACKGROUND 
     Restoration and reconstruction work in buildings often requires removal of trim wood around doors, windows, cabinets and baseboards. In many cases, the trim wood is later replaced, and since such trim wood is usually held in place with nails, much time can be spent removing the nailed trim without splitting it and otherwise pulling or removing the nails from the trim so that the trim can be reused. 
     Such nail removal is made more difficult by the fact that trim wood is usually held in place with finishing nails that have small heads only slightly larger in diameter than the nail shank. Also, finishing nails are often counter-sunk into the wood, so that a tool used to remove the nail must be dug into the wood to get a grip on the nail. This, and any prying force used, can damage the wood around the nail. 
     Trim wood can be pried loose from its mounted position by carefully exerting prying pressure to pull the nails loose from the wood under the trim in which they are embedded, but this can be difficult to accomplish without splitting or otherwise damaging the trim wood. Nails can then be driven back out of the trim wood from the backside of the trim for easy removal, but this also can split the trim wood around the edge of a countersunk nail head. 
     Often, the best place to locate nails for refastening removed trim wood in place is the same place that its original fastening nails were located. Thus, replacement nails often re-secure trim wood in place by being driven back into the original holes. 
     Altogether, dealing with nail problems in removing and replacing wood trim in buildings can consume much of a worker&#39;s time. The invention of this application aims to reduce the labor involved and make nail extraction fast and convenient, with minimal damage to the trim wood being removed. Once the invention presents an effective way of extracting finishing nails, it becomes clear that the invention can be used anywhere that finishing nails have been deployed. This can include nail removal from furniture and other constructions that do not involve trim wood in buildings. Although the problem of finishing nails in trim wood motivated the inventive nail extractor, its operation makes it clear that it can also be used for extracting the bodies of screws whose heads have broken off. 
     SUMMARY 
     The nail extractor and extraction method of this application involves a smooth walled tube having an inside diameter slightly larger than the diameter of the heads of nails to be removed. The tube is spun and pressed into the wood around the nail head so that the tube drills into the wood and compresses a core of drilled wood against the embedded nail. When the tube has been spun and pressed into the wood to a sufficient depth, the compressed wood inside the tube grips and spins the nail loose so that the nail is quickly and easily extracted or withdrawn from the wood. 
     The inventive extractor preferably includes an ejector that can be advanced into the tube to eject the extracted nail from the tube. The necessary elements to accomplish the withdrawal of the nail and its ejection from the drilling tube are preferably combined in a sleeve that holds the drilling tube at its forward end and has an internal thread engaging an external thread of an ejector rod that is chucked into an electric drill. These elements are preferably arranged so that when the drill operates in a forward direction, the ejector rod retracts and the tube spins clock-wise into the wood to extract the nail. Then when the outer sleeve of the extractor is held against rotation and the drill rotates in a reverse direction, the ejector rod advances an ejector pin into the drilling tube to eject the nail and the drilled wood core from the drilling tube. 
     The extraction and ejection of a nail is accomplished without any contact between the extractor and the nail itself. This avoids all jaws or grippers that must physically engage the nail to accomplish its extraction, and instead, the drilled core of wood compressed within the drilling tube accomplishes the necessary nail gripping and also spins the nail loose from its anchorage so that it is easily withdrawn from the wood. 
    
    
     DRAWINGS 
     FIGS. 1-4 are schematic views of the operation of the inventive nail extractor shown beginning the nail extraction process in FIG. 1, drilling into wood around the nail in FIG. 2, extracting the gripped nail in FIG. 3, and ejecting the extracted nail from the drilling tube in FIG.  4 . 
     FIG. 5 is an exploded and partially cut away view of a preferred embodiment of the inventive nail extractor. 
     FIG. 6 is a partially sectioned view of a preferred embodiment of the drilling tube for use with the extractor of FIG.  5 . 
     FIG. 7 is a partially sectioned, fragmentary view of an ejector rod for the extractor of FIG.  5 . 
    
    
     DETAILED DESCRIPTION 
     The way the inventive nail extractor works is best shown in the schematic views of FIGS. 1-4. Extractor  10  is preferably powered by an electric drill  15  so as to spin or rotate tube  20 . A finishing nail  11  with a head  12  is slightly countersunk into a trim board  13  that is fastened to a substrate  14  by nail  11 . Board  13  need not be a trim board, and can be a furniture part or other construction secured with nail  11 . 
     To remove nail  11 , drill or extractor tube  20  is positioned to surround nail head  12  and is pressed against trim wood  13  as drill  15  is actuated to spin tube  20 . As this occurs, a worker pushes on drill  15  to press spinning tube  20  into wood  13 , as shown in FIG.  2 . 
     As drill tube  20  is spun and pressed into wood  13 , it drills into wood  13  around nail head  12  and the shank of nail  11 , as illustrated. As spinning tube  20  penetrates wood  13 , it drills out and compresses a core  21  of wood surrounding nail  11 . At some depth of penetration, the compressed wood core  21  drilled of wood  13  inside of tube  20  grips nail  11  sufficiently to spin nail  11  loose from its anchorage in substrate  14 . The penetration depth of extractor tube  20  that sufficiently grips nail  11  to begin spinning it varies with circumstances that include the size and length of nail  11  and the kind of wood involved. This point can be reached within board  13 , or within substrate wood  14 . Tube  20  must be long enough so that it can penetrate to a sufficient depth to grip nail  11  with compressed wood core  21 , but this usually occurs before tube  20  reaches the pointed end of nail  11 . Once nail  11  is gripped and spun by the rotation of tube  20  and drilled wood core  21 , nail  11  is loosened from substrate  14  and is readily withdrawn, as shown in FIG.  3 . 
     When extracted from wood  13  and  14 , nail  11  usually extends beyond a cutting end  22  of tube  20 , as illustrated. This can vary with the tool operator, however, who may sense the loosening of nail  11  and quickly withdraw it, or who may push drill tube  20  deeper than necessary into wood  13  and  14 . 
     The hole remaining in the wood upon extraction of nail  11  includes a drilled socket  23  extending into wood  13 , and possibly into substrate wood  14 , where drill tube  20  drilled in around nail head  12 . A nail hole  24  may also extend beyond bored socket  23 , representing the extent of nail  11  beyond tube  20 , which is spun loose from wood  14  once nail  11  is gripped and rotated by compressed wood core  21 . If trim wood  13  is remounted, socket hole  23  is preferably filled with wood putty or the like. Also, a nail larger than nail  11  can be driven into socket  23  to hold a remounted board  13  in place. 
     FIG. 4 schematically shows the ejection of nail  11  and drilled wood core  21  from extraction tube  20  after nail  11  is extracted from the wood in which it was embedded. This is preferably accomplished by holding extractor  10  from rotating while reversing drill  15  to advance ejector rod  30  into drill tube  20 . This pushes nail  11  and drilled wood core  21  out of the open end  22  of drill tube  20 , as illustrated. 
     A preferred arrangement of elements combined in extractor  10  is shown in the exploded view of FIG.  5 . These elements include a sleeve-like body  40 , drive rod  50 , ejector rod  30 , and drill tube  20 . The assembly of these elements preferably allows relative axial motion between drive rod  50  and body sleeve  40 . 
     Drill tube  20  is preferably formed of tubing having a smooth interior and exterior wall. Stainless steel is available for drill tube  20  and is preferred for being strong and having a thin wall. The open, cutting end  22  of drill tube  20  can be sharpened to improved its cutting ability as it is pressed into wood while spinning. An internal bevel sharpened on cutting end  22  is preferred so that drilled wood is compressed inward around a nail surrounded by tube  20  as it advances into wood. A serrated or saw tooth cutting edge at tube end  22  is possible but not necessary. An external bevel sharpened on cutting end  22  can also work, as can no sharpening at all. Hardening the cutting end of the tube can prolong its cutting ability, whether the tube is sharpened or not. 
     Tube  20  preferably has a wall thickness as thin as possible to accomplish the necessary drilling task. One reason for this is to make the drill hole around a nail head as small as possible, and another is that a thin walled tube is easier to press into wood than a thicker walled tube. The tube wall cannot be so thin that the tube is in danger of collapsing or breaking when the spinning tube is pressed into wood, though. 
     The inside diameter of tube  20  is preferably slightly larger than the diameter of a head  12  of a nail to be extracted. Since finishing nails come in different sizes, drill tubes  20  having different inside diameters are also preferably available. Each size of drill tube is preferably press fit into a mounting collar  25  having a screw thread  26  mating within an internal thread  41  formed inside sleeve  40 . This allows a suitable size of drill tube  20  to be screwed to a forward end of extractor body  40  and allows convenient interchange between sizes of drill tubes. 
     Mounting collar  25  holding drill tube  20  preferably has a conical entrance cavity  26  to guide ejector rod  30  into the inside of drill tube  20 . A rear end  19  of drill tube  20  can seat against a step  28  formed at the intersection of conical bore  26  and a drill tube receiving bore  27  formed in mounting collar  25 . Drill tube  20  preferably has a press fit into bore  27 . 
     Internal thread  41  preferably extends from a forward end  43  of sleeve  40  to a stop  42  arranged toward a rear end  44  of sleeve  40 . This provides not only threads necessary to receive threads  26  of tube mounting collar  25 , but also to receive threads  51  of drive rod  50 . Drive rod  50  can then be inserted rearwardly into forward end  43  of sleeve  40  before tube mounting collar  25  is threaded onto sleeve  40 . Drive rod  50  is long enough so that its hex-shaped drive end  16  emerges from rear region  44  of sleeve  40  so that hex end  16  can be manipulated to engage drive rod threads  51  with sleeve threads  41  and move drive rod  50  rearwardly of sleeve  40 . The inner engagement of drive rod threads  51  with internal threads  41  of sleeve  40  allows axial relative movement to occur in response to relative rotation between drive rod  50  and sleeve  40 . 
     The hex-shaped drive end  16  of drive rod  50  conveniently serves for chucking drive rod  50  into electric drill  15 . Ejector rod  30  is mounted in a forward end  52  of drive rod  50  and can be formed of drill rod or of a conventional twist drill bit, as best shown in FIG.  6 . Forward end region  52  of drive rod  50  preferably has a larger diameter socket  53  intersected by a set screw  54 , and a smaller diameter socket  55  intersected by another set screw  56  that can be threaded into tapped hole  57 . This allows two different sizes of drill bits or rods  30  to serve as ejector rods. A smaller diameter rod can be inserted into bore  55  and held by set screw  57 , and a larger diameter rod can be inserted into bore  53  and held by set screw  54 . 
     For ergonomically suiting extractor  10  to the habits of users of electric drills, threads  51  and  41  are preferably left handed. This causes drive rod  50  to retract within sleeve  40  and retract ejector pin  30  rearwardly as drill  15  is rotated in a forward direction. Frictional resistance of tube  20  drilling into wood around a nail can cause sleeve  40  to advance relative to drive rod  50  and insure that ejector pin  30  is retracted from tube  20 . Retraction of ejector pin  30  is necessary, of course, for tube  20  to drill into wood around nail  11  without any interference from an ejector pin. 
     Once a nail is extracted, it is held tightly within drill tube  11  by compressed wood core  21 . At this point, the worker holds sleeve  40  against rotation while reversing drill  15 , which then drives shaft  50  forward within sleeve  40  to advance ejector pin  30  into drill tube  20 . This forces the extracted nail  11  and its surrounding drilled wood core  21  out of drill tube  20 , as shown in FIG.  4 . 
     The operation of nail extraction can work just as well with right handed threads  41  and  51  so that drill  15  is driven in reverse to advance drill tube  20  into wood around a nail, and then is driven in a forward direction to advance ejector pin  30  into drill tube  20 . This may seem backward to the customary uses of electric drills, but this may work better if the extractor tool is also used for extracting the bodies of screws with heads broken off. 
     When a different size extractor tube  20  is chosen for removal of a different size finishing nail, it may be necessary to also change the size of ejector rod  30 . Preferably ejector rod  30  is chosen to be only slightly smaller in outside diameter than the inside diameter of a matching drill tube  20 . Using a smaller than necessary ejector rod  30  can risk rod breakage in ejecting larger nails from drill tube  20 .