Patent Application
20140112732
The present disclosure relates generally to a method and apparatus for coaxially aligning at least 2 separate workpieces having circular apertures therein and/or securely attaching a boss in a circular aperture in a workpiece.
Sometimes it is desired to align two structures (or more), such as workpieces, having circular apertures therein, coaxially, with a high degree of precision. Additionally, sometimes it is desired to be able to place a boss or protrusion, for various reasons, in a work piece securely and simply, using a device that is relatively cheap to produce.
One attempt to resolve these issues in the past has included use of standard slotted pins. However, in some applications the shear force on the resulting dowel is too large for such an apparatus and method to be effective. More specifically, since standard slotted pins are generally hollow, they do not contain an inner core and thus are susceptible to shearing at relatively low loads.
Another apparatus and method disclosed in the prior art is disclosed in U.S. Pat. No. 6,056,489 issued on May 2, 2000 to Keller (the “'489 patent”). The '489 patent discloses an expansion dowel for use in attaching members using a circular bore. Specifically, the '489 patent discloses an expansion dowel including: a cylindrical, expandable dowel body having a plurality of axial slots opening at a front, in a setting direction, of the dowel body, and a bore which tapers in the setting direction in a region of the axial slots; an expansion sleeve arranged inside of the dowel body and tapering in the setting direction, the expansion sleeve having a conical tapering, in the setting direction; the bore having a plurality of slots extending in an axial direction; a plurality of projections projecting from an outer surface of the sleeve and adapted to displace in the axial slots of the dowel body; and an expansion member axially displaceable in the bore of the dowel body.
While the expansion dowel of the '489 patent may be useful for some applications, it does not serve a general utility for all applications. Specifically, the machined parts necessary to utilize the expansion dowel of the '489 patent are very intricate in design and use, requiring significant machining to achieve. Furthermore, the expansion of the dowel sleeve disclosed in the '489 patent is accomplished by the pounding of an expansion member by a worker. This expansion may be considered undesirable in many applications because the pounding of a hammer is generally not as precise a work movement as may be desired and may create undesirable and imprecise loads being placed on the workpieces in which the expansion dowel disclosed in the '489 patent may be used. Additionally, the use of a hammer can sometimes result in damage to the workpieces themselves. For this reason, it may be desired to have an expanding dowel rod structure that is formed from relatively simple, easy to machine and/or obtain pieces for, which may be simply, easily and precisely used by a worker, which provides the desired force or load on the workpiece it is being used in, and which are not susceptible to shearing at relatively low loads.
In one aspect, the disclosure involves the use of an expanding dowel rod structure comprised of a dowel sleeve, an inner thrust retainer, and a bolt. More specifically, in an aspect of the disclosure, the thrust retainer is tapered to deform the expanding dowel sleeve in order that the deformation will interfere with and bear force on the bore of the workpieces that are being doweled. In an aspect disclosed herein, both the expanding dowel sleeve and the thrust retainer have tapered inner/outer faces, respectively, that mate, thus causing the desired expansion. As discussed above, the expanding dowel rod structure disclosed herein may be used in connection with workpieces having circular bores that need to be coaxially aligned and secured. In an aspect of the disclosure, in some applications, it may be desirable to be able to vary the force exerted on the bores of the dowel holes without varying the bore size itself, an aspect which may be accomplished by embodiments of the disclosure set forth herein.
In yet another aspect of the disclosure, an expanding dowel rod structure is disclosed that can be used to securely add a boss to a workpiece having a circular bore therein, thus saving considerably in cost and simplicity over prior art methods of casting a relatively thick workpiece and machining it down to the desired boss height. More specifically, in such an aspect, the dowel sleeve disclosed herein may be placed in a circular bore with a desired portion sticking out of the bore. The bolt may then be tightened in the thrust retainer disclosed herein to a desired torque such that the force acts on the bore of the workpiece allowing the assembly to be rigid in the workpiece and act as a boss.
As shown best in
Consistent with an aspect of the disclosure, the thrust retainer 18 includes a tapered outer face 24, an axial inner bore 25 having inner threads 30 therein, and a nub 22 on an outer portion thereof. In an aspect of the disclosure, the thrust retainer 18 may include a band portion 21 located on a bottom portion thereof, the band portion 21 being defined by a face having a constant radius. Also in an aspect of the disclosure, the nub 22 may be wedge-shaped in order to facilitate the engagement of the nub 22 within the slot 20 while preventing the nub 22 from sticking out of the slot 20 and thus interfering with the placement of the dowel rod structure 10 in a bore 34 of workpieces 32 in which the dowel rod structure 10 is being utilized. Consistent with this aspect of the disclosure, the nub 22 may be located on or above said band 21 on the tapered outer face 24 on the thrust retainer 18. Also consistent with the disclosure, the tapered outer face 24 of the thrust retainer 18 may be provided with a taper angle similar or identical to the taper of the tapered inner face 26 of dowel sleeve 16. Consistent with an aspect of the disclosure the shape of the tapered outer face 24 of the thrust retainer 18 and the tapered inner face 26 of the dowel sleeve 16 may be conical or pyramidal.
Consistent with an aspect of the disclosure, the bolt 12 may be comprised of a head 13 and shank 15, and may preferably include a washer 14 positioned under the head 13 and outer threads 28 positioned on the shank 15 of bolt 12. The washer 14 may be a separate element or may be machined integrally with the head 13 as is known to those of ordinary skill in the art. Conversely, the head 13 may be large enough to preclude the need for a washer 14. The important aspect of the size of the head 13 and/or washer 14 being that the head 13 or washer 14 should be large enough that an underside thereof may sufficiently engage the shoulder 19 of the dowel sleeve 16 when the expanding dowel rod structure 10 disclosed herein is in use.
In an aspect consistent with the disclosure, the thrust retainer 18 inner threads 30 are preferably shaped to mate with the outer threads 28 of bolt 12. Further, in an aspect of the disclosed embodiment, the nub 22 is shaped to be received in slot 20 of dowel sleeve 16 to prevent relative rotational movement between the thrust retainer 18 and the dowel sleeve 16 when the dowel rod structure 10 is being tightened.
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Next, consistent with the use of the dowel rod structure 10 as disclosed herein, the bolt 12 head 13 may be tightened to provide the desired expansion of the dowel sleeve 16 and thus be anchored into the work piece(s) 32. Specifically, the head 13 of the bolt 12 (shown herein as a hex head, but which could be of practically any configuration as is known by those of ordinary skill in the art), could begin being torqued by an operator. Caused thereby, the thrust retainer 18 tapered outer face 24 is driven up and into the similarly-shaped dowel sleeve 16 tapered inner face 26 causing dowel sleeve 16 to expand radially, and generally evenly, across the entire outer face 11 of dowel sleeve 16. More specifically, upon application of a load by torqueing of bolt 12, the underside of head 13 or washer 14 engages shoulder 19 of dowel sleeve 16 causing axial relative displacement of the thrust retainer 18 into the dowel sleeve 16. The interaction of tapered outer face 24 of thrust retainer 18 and tapered inner face 26 of dowel sleeve 16 as thrust retainer 18 is pulled upwardly by bolt 12 results in generally uniform expansion of the dowel sleeve 16 outer face 11. Upon expansion of the sleeve 16 radially, as shown best in
It should be noted that the taper of the inner face 26 of the dowel sleeve 16 need not exactly match the taper of the outer face 24 of the thrust retainer 18 and may be determined in order to provide the desired amount of pressure and displacement of the dowel sleeve 16 depending on the desired application. It should also be noted that the disclosure of the present invention is useful in that the force exerted by the dowel sleeve 16 outer face 11 on the bore(s) 34 may be relatively precisely controlled, compared with some prior art “hammer” methods, by specifying an exact torque to be applied to bolt 12 head 13 by an operator. Further, as discussed above, and as shown best in
Consistent with an aspect of the disclosure as disclosed herein, the angle of the outer face 24 of the thrust retainer 18 (and thus the corresponding angles of the inner face 26 of the dowel sleeve 16) may vary greatly depending on the geometries and engineering requirements, limitations, tolerances, etc. that are faced for the application in which the expanding dowel rod structure 10 disclosed herein is used. Similarly, the shape, size, length, threading, etc., of the bolt 12 may vary as well. And, in accordance therewith, the exact width, composition, etc., of the dowel sleeve 16, thrust retainer 18, and bolt 12 may vary greatly based upon the same variables discussed above as would be recognizable to a person of ordinary skill in the art.
Accordingly, it should be understood that the disclosure does not require any specific size, tolerance, material of manufacture, etc., for the dowel sleeve 16, thrust retainer 18, or any other piece, part, component disclosed herein. However, consistent with the embodiment disclosed herein, the angle of the outer face 24 of the thrust retainer 18 may be about 10 degrees and the angle of the inner face 26 of the dowel sleeve 16 may be similar thereto. A ¾ inch bolt would be operable in accordance with the disclosure and the components disclosed herein could be made of any operable material including carbon steel, such as 0.48-0.66% Carbon, heat treated, 45-55 HRC.
The disclosed expanding dowel rod structure 10 is useful for coaxially aligning and securing at least 2 separate workpieces 32 having circular apertures or bores 34 therein and/or for securely attaching a boss in a circular aperture in a workpiece 32. Additionally, the disclosed dowel rod structure 10 may be used in almost any application where, for example, add-on parts must be added to and/or secured to workpieces 32 using a through-assembly, and which require, or could utilize, anchorable attachment devices. Non-limiting examples of uses and/or applications in which the dowel rod structure 10 disclosed herein could be used include almost any application where traditional slotted pins and/or coiled spring pins may have been used in the past. Such applications include, but are not limited to: automotive; manufacturing; locomotive; aeronautical; industrial; building; et al. applications. More specifically, the apparatus disclosed herein may be used in applications wherein it is needed to secure two (or more) workpieces 32 together utilizing circular bores 34 in the workpieces 32, and particularly, wherein it is desired to use an attachment device that is resistant to shear forces in such applications.
More specifically, it is noted that the use of the dowel rod structure 10 in accordance with the disclosure containing the thrust retainer 18 element as disclosed herein provides significant mass and a core to the dowel sleeve 16 that makes the dowel rod structure 10 of the present disclosure resistant to shearing at relatively low loads. This is particularly useful when the dowel rod structure 10 disclosed herein is used to coaxially secure two or more workpieces 32 through bores 34 as the shear forces against the dowel rod structure 10 in such applications can be relatively high, particularly depending on the applications in which the workpieces 32 are being used.
Further, consistent with aspects of the disclosure, the dowel rod structure 10 disclosed herein may be used in applications wherein it is desired to use a securing structure that may be formed relatively easily and simply from readily available and relatively inexpensive materials. Additionally, the dowel rod structure 10 disclosed herein is particularly useful in securing two or more workpieces 32, or providing a boss to a single workpiece 32, when it is desired to control the force being exerted against the bores 34 of the workpiece(s) 32 with some degree of precision.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed dowel rod structure 10 disclosed herein without departing from the scope of the disclosure. Other embodiments of the dowel rod structure 10 may be apparent to those skilled in the art from consideration of the specification disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.
