US3662804A

US3662804A - Self-locking fasteners

Info

Publication number: US3662804A
Application number: US6752A
Authority: US
Inventors: Leo L Krywitsky; Robert S Morrow
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-06-17
Filing date: 1970-01-29
Publication date: 1972-05-16
Anticipated expiration: 1989-05-16
Also published as: CA922550A

Abstract

A self-locking screw having an elongated beam extending transversely of the screw at one end of the screw. The beam is formed from the material of the screw and has a length less than the diameter of the screw. A distal end of the beam is adapted to engage the axial wall of a generally cylindrical opening to lock the screw in place. A removal tool is also provided to remove the screw. The tool engages in a tool-engaging well in the screw and deflects the beam radially inwards to disengage the beam from the wall of the opening.

Description

United States Patent Krywitsky et al.

[4 1 May 16, 1972 [54] SELF-LOCKING FASTENERS [72] Inventors: Leo L. Krywitsky, Toronto; Robert S. Morrow, Weston, Ontario, both of Canada abandoned.

[52] U.S.C1 ..15l/14,151/9,151/11, 151/21,151/48,151/50,l45/50.1 [51] Int. Cl ..F16b 39/30, F16b 39/02, F16b 39/00 [58] FleldoiSearch ..151/6,9,10,11,l2,13,l4, 151/21 B, 22, 24, 25, 26, 39, 40, 48, 49, 50; 145/501, 52

[56] References Cited UNITED STATES PATENTS 413,580 10/1889 Talbot ..151/21 B 783,088 2/1905 Vaughan... ....l51/1l 1,764,168 6/1930 Hosking ....151/14 1,849,240 3/1932 McCrudden ..l51/22 1,874,389 8/1932 Trotter ..151/14 1,874,657 8/1932 Trotter 151/14 1,887,616 11/1932 Berge... ..l51/l4 2,019,387 10/1935 Blair 151/21 B 2,372,888 4/1945 Duggan ..151/24 FOREIGN PATENTS OR APPLlCATlONS 2,645 2/1903 Great Britain ..151/48 4,391 2/1912 Great Britain.... ...15l/11 204,180 9/1923 Great Britain.... ....151/6 353,581 5/1961 Switzerland ..151/44 Primary Examiner-Marion Parsons, Jr. Attorney-Rogers, Bereskin & Parr 57 ABSTRACT A self-1ocking screw having an elongated beam extending transversely of the screw at one end of the screw. The beam is formed from the material of the screw and has a length less than the diameter of the screw. A distal end of the beam is adapted to engage the axial wall of a generally cylindrical opening to lock the screw in place. A removal tool is also provided to remove the screw. The tool engages in a tool-engaging well in the screw and deflects the beam radially inwards to disengage the beam from the wall of the opening.

2 Claims, 9 Drawing Figures PATENTEDMM 16 I972 SHEET 1 [IF 2 INVENTORS LEO L. R TSKY ROBE S. ORROW PATENTEDMAY 16 I912 3, 662 804 SHEET 2 0F 2 INVENTORS LEO L. KRYWITSKY ROBERT S. MORROW BY SELF-LOCKING FASTENERS This application is a Continuation of application Ser. No. 737,685 filed on June 17, 1968, now abandoned.

This invention relates to self-locking screws and to a tool for removing the screws.

Grub screws, locking screws and the like are commonly used to lock a machine part in place. In many cases a locking screw is simply tightened so that it is unlikely to work loose. In other cases where the screw may be subjected to relatively large temperature variations or mechanical vibration the locking screw is manufactured with a peripheral deformation such that when the screw is fed into a threaded opening in a workpiece,there is a frictional resistance to turning which tends to prevent release of the screw. However the force required to enter the screw is not significantly different from the force required to remove it from the opening and the screw can be removed without excessive damage to the openlng.

It is is one of the, objects of the present invention to provide a self-locking screw which when fed into a threaded opening, requires a relatively large force to remove the screw. It is also an object to provide a tool for removing the screw such that the screw can be removed without damaging the threaded opening Accordingly the invention in one of its aspects provides a screw having an elongated beam extending transversely of the screw at one end of the screw. The beam is formed from the material of the screw and has a length less than the diameter of the screw. A root end of the beam is connected to the screw and a distal end is adapted to engage the wall of a threaded opening to lock the screw in place. If an attempt is made to remove the screw without a special tool the beam acts as a strut and the distal end cuts into the material of the opening thereby locking the screw in the opening.

In another of its aspects the invention provides a tool for removing the screw. The tool is adapted to engage in a toolengaging recess or well in the screw and to deflect the beam out of locking contact with the opening.

The invention will be better understood with reference to the drawings wherein:

FIG. I is a side view of a set-screw according to the invention;

FIG. 2 is a top view of the set-screw;

FIG. 3 is a view similar to FIG. 2 showing the screw in a threaded opening;

FIG. 4 is an enlarged view of the portion of the screw;

FIG. 5 is a perspective view of another embodiment of the invention;

FIG. 6 is a perspective view of a tool for use with the invention;

FIG. 7 is a side view of the tool;

FIG. 8 is a view of the tool taken from the bottom of FIG. 7; and

FIG. 9 is a part sectional view of the tool taken from the side of FIG. 7 showing the tool in use to remove a screw.

Reference is first made to FIGS. 1 and 2 with particular reference to FIG. 2. A set-screw 10 having a leading end 12 and a tool-engaging end 14 has a helical thread 16 extending between the tool-engaging end 14 and the leading end 12. The tool-engaging end 14 has a hexagonal recess or well 18 for receiving an Allen key to position the screw 10 in a threaded opening. A transverse elongated beam 20 is formed in the tool-engaging end 14 from the material of the screw 10 for locking the screw in the threaded opening.

The beam 20 includes a relatively large root end 22 and a smaller distal end 24. An outer face 26 of the beam is substantially chordal with respect to the circular periphery of the screw 10, and an inner face 28 forms a portion of the wall of the well 18. The outer face 26 tapers outwardly axially from the tool engaging end 14 for co-operating with a removal tool as will be described. The upper face of the beam 20 is in the plane of the tool-engaging end 14, and a lower face 30 is separated from a shoulder 32 on the set-screw 10 to allow the beam 20 to flex from the root end 22. Because the beam 20 is formed from the material of the screw 10, the distal end 24 is threaded so that when the screw end enters the threaded opening, the distal end follows the threads as the screw is turned in the opening. If required, the beam can be made with more resilience by changing its shape to conform with the chain dotted outline of FIG. 2.

Reference is now made to FIG. 3 which shows the screw 10 in a threaded opening 34 of a workpiece 36. In manufacture the beam is machined from the parent metal of the screw 10 and then deformed slightly by bending the beam such that the distal end 24 moves radially outwards into the position shown in FIG. 2. When the screw enters the opening 34, the beam deflects such that the distal end 24 moves radially inwards so that the screw can be entered into the opening with relatively little frictional resistance. However when an attempt is made to remove the screw 10 from the opening 34, the beam 20 locks the screw and prevents removal. The locking action is caused by a leading edge 38 of the distal end 24. Because of the bending of the beam 20, the leading edge, which is longitudinally oriented in relation to the set-screw 10, digs into the metal around the opening 34. This action is better shown in FIG. 4 which shows the leading edge 38 in contact with the opening 34 in the workpiece 36. As seen in this figure, the leading edge 38 has both a clearance angle a and a rake angle b. Consequently when an attempt is made to remove the screw, the edge 38 tends to remove metal from the workpiece 36 resulting in a relatively large locking force. As further force is applied to remove the screw, the beam 20 acts a strut and consequently can resist very large turning forces applied to the screw. If the force is sufficiently large, and the material of the workpiece 36 is of a material such as steel, the screw 10 will normally only be removed after sufficient force is applied to break the beam 20.

The action of the locking beam 20 differs from that of prior devices used to lock screws in that the beam 20 does not rely on a frictional force, but relies on a cutting action to lock the beam and hence the screw in place.

If required, the locking beam 20 can be incorporated in the leading end of the screw 10 in which case the beam 20 would be a mirror image of that shown in FIG. 2. to allow entry of the screw 10 in the opening 34. Removal of the screw would only be possible from the tool engaging end by applying sufiicient force to break the beam 20. However if the opening 34 is accessible from both ends, the leading end can be made in a similar form to the present tool-engaging end 14 so that a removal tool can be engaged in the screw for removal of the screw. In this case removal will take place from an opposite end of the screw to the end used for insertion of the screw and the screw would in effect have two tool engaging ends. For the purpose of the present description however, the term toolengaging end is used to describe an end of the screw having a locking beam and tool engaging well such as shown in FIG. 1.

Reference is now made to FIG. 5 which shows a bolt 40 having a head 42 in which is formed a locking beam 44. The beam is similar in all respects to the beam 20 (FIG. 2) but for the fact that the beam 44 is formed in the head 42 of the bolt 40. The bolt 40 is of a type which is to be recessed in a workpiece such that head 42 does not protrude from the workpiece. A cylindrical recess in the workpiece houses the head 42 with a minimum of clearance such that the beam 44 locks the bolt 40 by engaging with the wall of the recess.

Reference is now made to FIG. 6 which illustrates a tool 46 and driver 48 for removing the screw 10 from an opening such as 34 (FIG. 3). The driver 48 is a simple hand tool having a hexagonal recess 50 at its leading end and a handle 52 at its outer end. Tool 46 includes an outer hexagonal bar 54 adapted to engage in the recess 50 for turning the tool 46 by hand. An outer hexagonal bar 55 which may be a continuation of bar 54,if required,is of a size for engaging in the well 18 (FIG. 2) of the screw 10. The

bars

54, 55 extend from respective outer and inner ends of a cylindrical member 56 which is rigidly attached concentrically to the bar 54. The cylindrical member has a tapered extension 58 extending from its outer end in generally parallel relationship with the bar 55. The extension 58 however does not extend to the outer end 59 of the bar 55 for reasons which will be explained. A longitudinally extending recess 60 in the bar 55 extends from the cylindrical member 56 outwards for a distance slightly greater than the axial extent of the tapered extension 58.

Reference is next made to FIGS. 7 and 8 which illustrate the orientation of the outer hexagonal bar 54 in relation to the tapered extention 58. As best seen in FIG. 8 an adjacent flat surface 62 on the hexagonal bar 54 defines an acute angle with an inner face 63 of the extension 58, and the bottom 57 of the recess 60 is planer as shown by the dotted line in FIG. 8, the bottom 57 of recess 60 also forms the same acute angle with the flat surface 62 of bar 55. This angle is necessary to accommodate the beam 20 (F162) between the bar 55 and tapered extension 58. The angle is therefore determined by the shape of the beam 20. However, because the beam is preferably tapered from its root end 22 to its distal end 24, there will be an angle (measured in a transverse plane) between the flat surface 62 of bar 55 and the surface 63 of extension 58. To facilitate engagement of the extension 58 and the beam 20 the face 63 of extension 58 is tapered longitudinally as is the outer face 26 of beam 20 to provide a wedge action to deflect the beam 20 inwardly as the tool is engaged with the screw. This is best seen in FIG. 9 where the beam 20 is shown in engagement with the extension 58. The recess 60 in bar 55 permits the beam 20 to deflect radially without interfering with the bar 55.

What we claim as our invention is:

1. In a generally cylindrical self-locking set-screw having a longitudinal axis, a leading end and a tool engaging end, the

improvement comprising: an elongated beam extending transversely of said longitudinal axis, said beam being formed from the material of said screw and said beam having a length less than the diameter of the screw, said beam being adapted to engage the wall of a threaded hole such that said set-screw can be tightened relatively easily into said hole, and such that said set-screw resists removal from said hole, said beam comprising: an upper face lying generally in the plane of said tool engaging end; a relatively large root end by which said beam is attached to said tool-engaging end of said screw; a relatively small distal end which is normally slightly outside the cylindrical boundary of the set-screw, said distal end comprising a portion of the threads of said set-screw and said beam being tapered from said root end to said distal end; a leading edge on said distal and extending longitudinally of said set screw, said leading edge having clearance and rake angles so that when said set-screw is in said threaded hole said leading edge interferes with said threaded hole to resist removal of said setscrew from said hole; and a generally planar outer face extending transversely of said screw in a plane generally parallel to said longitudinal axis for receiving a tapered extension on a removal tool whereby longitudinal force on said tool deflects said distal end inwardly out of contact with said hole to allow removal of said set-screw.

2. The invention as claimed in claim 1 which further comprises: a lower face similar to said upper face and parallel thereto; a tool-engaging well formed in said tool-engaging end; and an inner face of said beam opposite to said outer face, said inner face forming a portion of said tool-engaging well.

Claims

1. In a generally cylindrical self-locking set-screw having a longitudinal axis, a leading end and a tool engaging end, the improvement comprising: an elongated beam extending transversely of said longitudinal axis, said beam being formed from the material of said screw and said beam having a length less than the diameter of the screw, said beam being adapted to engage the wall of a threaded hole such that said set-screw can be tightened relatively easily intO said hole, and such that said set-screw resists removal from said hole, said beam comprising: an upper face lying generally in the plane of said tool engaging end; a relatively large root end by which said beam is attached to said tool-engaging end of said screw; a relatively small distal end which is normally slightly outside the cylindrical boundary of the set-screw, said distal end comprising a portion of the threads of said set-screw and said beam being tapered from said root end to said distal end; a leading edge on said distal end extending longitudinally of said set screw, said leading edge having clearance and rake angles so that when said set-screw is in said threaded hole said leading edge interferes with said threaded hole to resist removal of said set-screw from said hole; and a generally planar outer face extending transversely of said screw in a plane generally parallel to said longitudinal axis for receiving a tapered extension on a removal tool whereby longitudinal force on said tool deflects said distal end inwardly out of contact with said hole to allow removal of said set-screw.