# US 5,704,748 A · Self-locking machine screw > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,704,748 A - Document ID: US5704748A - Status: Granted - Kind: A - Application number: 08/717,707 - Filed: 1996-09-23 - Granted: 1998-01-06 - Earliest claimed: 1996-09-23 - Inventors: Richard Criswell - Web page: https://patentgrep.com/patent/US5704748A ## CPC - F16B 39/34: Locking by deformable inserts or like parts - F16B: DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING (couplings for transmitting rotation F16D) ## Abstract A machine screw has a recess in its body extending from the threaded end into the body. The recess intersects the threads. A tang slot extends across the end of the machine screw body. A locking member is in the recess and the tang of the locking member is in the tang slot. The locking member includes a spring which extends into the thread space so that, when the machine screw is screwed into a threaded part, the spring is deflected by the threaded part to releasably lock the machine screw in place. ## Claims ### Claim 1 A self-locking machine screw comprising: a male substantially cylindrical body having a radius and having a first end and a second end defining the length of said body, said body having screw threads having a root diameter, said screw threads extending at least a portion of the length of said body from said first end toward said second end; a recess in said first end of said body, said recess having walls extending generally lengthwise with respect to the length of said body and intersecting said screw threads so that said recess is radially partially exposed, said recess being more narrow at said root diameter than at a smaller radius, a stop wall; a resilient metallic locking member in said recess, said metallic locking member having a plurality of thread engagement surfaces thereon sized and shaped to engage on thread surfaces in a threaded hole, said metallic locking member being positioned in said recess so that at least a portion of said engagement surfaces are exposed out of said recess so that when said machine screw is turned into a threaded hole, a portion of said thread engagement surfaces on said resilient metallic locking member which is exposed from said recess is resiliently deflected to provide a controlled frictional drag of prevailing torque that resists inadvertent turning of the screw; and said metallic locking member engaging on said stop wall to inhibit rotation of said metallic locking member in said recess. ### Claim 2 (depends on 1) The machine screw of claim 1 wherein said machine screw is metallic. ### Claim 3 (depends on 1) The machine screw of claim 1 wherein both said machine screw and said locking member are metallic. ### Claim 4 (depends on 3) The machine screw of claim 3 wherein said recess is deeper than the length of said locking member so that said locking member lies within said recess sufficiently far so that substantially two threads on said bolt extend in a direction away from said first end. ### Claim 5 (depends on 4) The machine screw of claim 4 wherein said locking member is a coil spring. ### Claim 6 (depends on 5) The machine screw of claim 5 wherein said walls of said recess define a substantially cylindrical recess and said locking member is a coil spring within said recess. ### Claim 7 (depends on 1) The machine screw of claim 1 wherein said locking member is a coil spring. ### Claim 8 (depends on 7) The machine screw of claim 7 wherein said walls of said recess define a substantially cylindrical recess and said locking member is a coil spring within said recess. ### Claim 9 A self-locking machine screw comprising: a male substantially cylindrical screw-threaded body having a first end and a second end with said screw threads extending from said first end toward said second end; a substantially cylindrical recess in said first end of said body, said recess having walls intersecting said screw threads so that said recess is partially exposed; a coil spring locking member within said recess, a tang on said locking member extending away from said coil portion of said locking member and a tang slot in said body to receive said tang to position and retain said coil spring in said recess so that when said machine screw is turned into a threaded hole, the portion of said locking member which is exposed from said recess is deflected to provide a controlled frictional drag of prevailing torque that resists inadvertent turning of the screw. ### Claim 10 (depends on 9) The machine screw of claim 9 wherein said recess and said tang slot are sufficiently deep so that said coil spring and said tang are substantially two threads away from said end. ### Claim 11 A self-locking machine screw comprising: a male substantially cylindrical screw-threaded body having a first end and a second end with said screw threads extending from said first end toward said second end; a substantially cylindrical recess in said first end of said body, said recess having walls intersecting said screw threads so that said recess is partially exposed; a coil spring locking member within said recess, said spring being wound of wire having two surfaces substantially 60 degrees with respect to each other and said surfaces face substantially the same way as said screw threads on said machine screw body so that when said machine screw is turned into a threaded hole, the portion of said locking member which is exposed from said recess is deflected to provide a controlled frictional drag of prevailing torque that resists inadvertent turning of the screw. ### Claim 12 A machine screw comprising: a body, said body being substantially cylindrical, said body having a first end, said body having a head opposite said first end, said body having screw threads on the exterior surface thereof extending from said first end toward said head; a recess in said body open to said first end of said body, said recess having an interior surface which intersects the surfaces of said screw threads, said recess being wider radially inward from the root diameter of said screw threads, a stop wall in said body at said recess; a resilient metallic locking member in said recess, said locking member having thread engaging surfaces thereon shaped to engage threads in a part into which said machine screw is threaded, said resilient metallic locking member being resiliently urged in a direction to be exposed at said screw threads so that when said machine screw is screwed into a threaded hole in a part, said locking member is deflected to resist removal of said machine screw from the threaded part, and said resilient metallic locking member engaging said stop wall to inhibit rotation of said locking member when said bolt is threaded into a part. ### Claim 13 A machine screw comprising: a body, said body being substantially cylindrical, said body having a first end, said body having a head opposite said first end, said body having screw threads on the exterior surface thereof extending from said first end toward said head; a substantially cylindrical recess in said body open to said first end of said body, said recess having an interior surface which intersects the surfaces of said screw threads; a metallic spring locking member in said recess, said spring being wound of metallic wire which has two surfaces positioned at substantially 60 degrees with respect to each other, said locking member being resiliently urged in a direction to be exposed at said screw threads so that when said machine screw is screwed into a threaded hole in a part, said locking member is deflected to resist removal of said machine screw from the threaded part. ### Claim 14 (depends on 13) The machine screw of claim 13 wherein said spring is wound of metallic wire which is substantially an equilateral triangle in cross section, with one of the corners of said triangle being directed toward the exterior of said coil spring. ### Claim 15 (depends on 13) The machine screw of claim 13 wherein said spring is wound of metallic wire with spaces between successive turns of wire. ### Claim 16 A machine screw comprising: a body, said body being substantially cylindrical, said body having a first end, said body having a head opposite said first end, said body having screw threads on the exterior surface thereof extending from said first end toward said head; a recess in said body open to said first end of said body, said recess having an interior surface which intersects the surfaces, a stop wall in said body at said recess of said screw threads; a metallic spring locking member in said recess, said spring being wound as a series of spaced partial toroidal coils with offsets between the toroidal coils, said locking member having thread engaging surfaces thereon shaped to engage threads in a part into which said machine screw is threaded, said resilient metallic locking member being resiliently urged in a direction to be exposed at said screw threads so that when said machine screw is screwed into a threaded hole in a part, said locking member is deflected to resist removal of said machine screw from the threaded part, and said resilient metallic locking member engaging said stop wall to inhibit rotation of said locking member when said bolt is threaded into a part. ### Claim 17 (depends on 16) The machine screw of claim 16 wherein successive partial toroidal turns of said spring are rotatably spaced with respect to each other. ### Claim 18 (depends on 16) The machine screw of claim 16 wherein said coil spring is shorter than the length of said recess so that two threads on said machine screw extend past said coil spring when said coil spring is in said recess. ### Claim 19 (depends on 16) The machine screw of claim 16 wherein there is a tang on said coil spring and there is a tang slot at least partway across said first end of said machine screw, said tang slot being sized to receive said tang to prevent rotation of said coil spring. ### Claim 20 A machine screw comprising: a body, said body being substantially cylindrical, said body having a first end, said body having a head opposite said first end, said body having screw threads on the exterior surface thereof extending from said first end toward said head; a recess in said body open to said first end of said body, said recess having an interior surface which intersects the surfaces, a stop wall in said body at said recess of said screw threads; a spring locking member in said recess, said spring being shorter than the length of said recess so that substantially two threads on said machine screw extend past said spring when said spring is in said recess, said locking member having thread engaging surfaces thereon shaped to engage threads in a part into which said machine screw is threaded, said resilient metallic locking member being resiliently urged in a direction to be exposed at said screw threads so that when said machine screw is screwed into a threaded hole in a part, said locking member is deflected to resist removal of said machine screw from the threaded part, and said resilient metallic locking member engaging said stop wall to inhibit rotation of said locking member when said bolt is threaded into a part. ### Claim 21 A machine screw comprising: a body, said body being substantially cylindrical, said body having a first end, said body having a head opposite said first end, said body having screw threads on the exterior surface thereof extending from said first end toward said head; a recess in said body open to said first end of said body, said recess having an interior surface which intersects the surfaces, a stop wall in said body at said recess of said screw threads; a spring locking member in said recess, a tang on said spring and a tang slot at least partway across said machine screw, said tang slot being sized to receive said tang to prevent rotation of said spring, said locking member having thread engaging surfaces thereon shaped to engage threads in a part into which said machine screw is threaded, said resilient metallic locking member being resiliently urged in a direction to be exposed at said screw threads so that when said machine screw is screwed into a threaded hole in a part, said locking member is deflected to resist removal of said machine screw from the threaded part, and said resilient metallic locking member engaging said stop wall to inhibit rotation of said locking member when said bolt is threaded into a part. ### Claim 22 (depends on 21) The machine screw of claim 21 wherein said tang slot and said recess are sufficiently deep and said spring is sufficiently short so that when said tang is in said recess, substantially two threads of said machine screw extend past said spring and past said tang so that said machine screw can be introduced into a threaded part substantially two threads before said spring engages. ### Claim 23 A machine screw comprising: a body, said body being substantially cylindrical, said body having a first end, said body having a head opposite said first end, said body having screw threads on the exterior surface thereof extending from said first end toward said head; two recesses in said body open to said first end of said body, said recesses being substantially diametrically oppositely spaced and each having an interior surface which intersects the surfaces of said screw threads; a resilient metallic spring locking member, said locking member having two springs thereon respectively positioned within said two recesses, both of said recesses intersecting said threaded surfaces so that both of said springs are positioned for locking said machine screw in a threaded part in said recess, said locking member so that when said machine screw is screwed into a threaded hole in a part, said locking member is deflected to resist removal of said machine screw from the threaded part. ### Claim 24 (depends on 23) The machine screw of claim 23 wherein said springs are connected by a tang and there is a slot across said bolt connecting said recesses, said slot being sized to receive said tang. ### Claim 25 A machine screw comprising: a body, said body being substantially cylindrical, said body having a first end, said body having a head opposite said first end, said body having screw threads on the exterior surface thereof extending from said first end toward said head; a recess in said body open to said first end of said body, said recess having an interior surface which intersects the surfaces of said screw threads; a locking member in said recess, said locking member being a spring configured to comprise a plurality of connected semi-toroidal turns, so that each turn can provide opposite radial forces at each semi-toroid, said locking member being resiliently urged in a direction to be exposed at said screw threads so that when said machine screw is screwed into a threaded hole in a part, said locking member is deflected to resist removal of said machine screw from the threaded part. ### Claim 26 (depends on 25) The machine screw of claim 25 wherein said spring is a metallic spring formed with the semi-toroidal portion having a non-circular crossection.