TANGED SCREW THREAD INSERT WITH IMPROVED REMOVABILITY
A helical-shaped insert to engage a threaded fastener to a receiving member includes a helical coil having a plurality of coil sections having inner and outer surfaces forming a thread shape, and opposing first and second coil end sections. A removable tang extends radially inward from the first coil end section. A continuously curved surface at a finished end of the second coil end section forms a tangent point where the continuously curved surface tangentially meets the second coil end section outer surface.
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This application is a divisional application of U.S. patent application Ser. No. 11/095,713 filed on Mar. 31, 2005, now U.S. Pat. No. 7,862,283, issued on Jan. 4, 2011. The entire disclosure of the above application is incorporated herein by reference.
FIELD OF THE INVENTIONThe present invention relates in general to thread insert members and more specifically to helical coil shaped thread inserts insertable into an aperture of a relatively soft material to provide a female thread for subsequent insertion of a screw or bolt.
BACKGROUND OF THE INVENTIONThread inserts having a generally helical shape are commonly used to create a receiving thread for subsequent insertion of a screw or bolt into a relatively soft receiving material such as polymeric material or soft metals such as aluminum or magnesium, etc. An aperture is pre-tapped in the receiving material to receive the helical insert. The helical insert or “coil” includes a plurality of both outside and inside surface areas acting as screw threads. A tang which is an extension of the coil extends radially inwardly from a coil section at a leading end of the coil and is provided for grasping by an insertion tool. Using the insertion tool and tang, the coil is threaded into the aperture, the coil outer surfaces engaging the tapped threads of the aperture. The tang can then be broken off by material failure at a notch pre-formed at a junction of the tang and the helical coil. The coil inner surfaces then provide engagement surfaces for receiving the threads of a screw, bolt or other fastener.
Known helical coil designs provide retention strength or resistance to removal by sheared ends provided at both ends of the coil which bite into the softer receiving material when removal of the coil is attempted or a fastener is rotated into the coil. To further improve coil retention, “insert ends” having no chamfers together with the sheared ends are used. Removal of coils is often required, for example to remove and/or replace the fastener during maintenance, or if the coil is damaged or is installed improperly. During coil removal, the softer receiving material is susceptible to damage. When the receiving material is a casting or complex part, the cost to replace the damaged part can be excessive.
Coil designs are known which assist in removal of the coil, for example U.S. Pat. No. 6,171,040 to Sato. Sato discloses a pair of notches 10 which are formed at a back end portion of the coil and include contact surfaces 10b for engagement by a tool such as a bladed screw driver. At the back end of the coil, Sato also discloses a center flat surface 20 having chamfered surfaces 15, 16, 17 and 18. The disadvantage of the Sato and other known designs is that damage to the internal threads of the receiving material aperture can still occur when the coil is backed out, due to the corners of the chamfer geometry at the back end of the coil.
SUMMARY OF THE INVENTIONAccording to one preferred embodiment, a tanged screw thread insert with improved removability of the present invention includes a helical-shaped insert having a plurality of coil sections, including opposing first and second coil end sections. A continuously curved surface is created at a rounded distal end of the second coil end section. A tangent point is created where the curved surface tangentially meets an outer surface of the second coil end section.
According to another preferred embodiment, a thread insert includes a helical-shaped insert defining a plurality of coil sections including opposing first and second coil end sections. The coil sections each have an inner surface and an outer surface, the inner and outer surfaces each having a thread shape. The outer surface of each of the coil sections are aligned to create a substantially constant diameter coil body. A removable tang extends radially inward from the first coil end section. A continuously curved surface is created at a rounded distal end of the second coil end section. A tangent point is created where the curved surface tangentially meets the outer surface of the second coil end section. A first notch is disposed in the first coil end section proximate to a tang connection and positioned between the inner and outer surfaces. The first notch is operable to create a failure point in the first coil end section for removal of the tang. A second notch is created in the second coil end section proximate to the continuously curved surface, the second notch having a contact surface operable to assist in removal of the insert from an installed position.
According to yet another preferred embodiment, a method for creating a thread insert, the thread insert including a helical-shaped coil defining a plurality of coil sections including opposing first and second coil end sections and an outer coil diameter, includes creating a continuously curved surface at a rounded distal end of the second coil end section. The method further includes blending the continuously curved surface tangentially into an outer surface of the second coil end section to operably create a tangent point.
A tanged screw thread insert with improved removability of the present invention provides several advantages. By retaining a substantially constant outside diameter of the individual coil segments, removal of the coil presents a substantially constant contact diameter against the threads of the receiving member, which reduces the possibility of an out-of-round coil segment causing frictional damage to the threads. By providing a continuously curving end surface at a distal end of the coil second end segment, a smooth surface is presented during removal of the insert which reduces the chance of frictional damage to the threads of the receiving member.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
According to a preferred embodiment of a tanged screw thread insert of the present invention and referring to
Insert 12 is generally completely received within a thickness “A” of receiving member 14 in a general direction “B”. Insert 12 includes a continuous, helical-shaped coil, herein described for simplicity as a plurality of coil sections 18. Coil sections 18 each include an outer surface 20 having a thread-shape which engage a plurality of receiving threads 22 pre-tapped or formed in receiving member 14. Coil sections 18 each also include an inner surface 24 which are thread-shaped and sized to engage a plurality of threads 26 of fastener 16. Insert 12, fastener 16 and receiving threads 22 are coaxially aligned on a longitudinal axis 28. Longitudinal axis 28 is preferably aligned substantially perpendicular to at least a receiving face 29 of receiving member 14, but can be angled with respect to receiving face 29 or a central axis through receiving member 14 if receiving member 14 is formed in a curved shape. A tang 30 connects to and extends radially inward from a first coil end section 32 of coil sections 18.
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A tanged screw thread insert with improved removability of the present invention provides several advantages. By retaining a substantially constant outside diameter of the individual coil segments, removal of the coil presents a substantially constant contact diameter against the threads of the receiving member, which reduces the possibility of an out-of-round coil segment causing frictional damage to the threads. By providing a continuously curving distal end surface at a second end of the last coil segment, a smooth surface is presented during removal of the insert which reduces the chance of frictional damage to the threads of the receiving member.
The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.
Claims
1. A thread insert, comprising:
- a helical-shaped insert defining a plurality of coil sections including opposing first and second coil end sections, each coil section having an inner surface and an outer surface defining a thread shape;
- a notch defined between the inner and outer surfaces in the first coil end section, the first notch proximate to a tang extending inwardly from the first coil end section;
- a continuously curved convex surface at a second coil terminal end section that tangentially meets the outer surface of the second coil end section, wherein the intersection between the continuously curved convex surface and the outer surface intersects at an obtuse angle; and
- a recess defined in the second coil section proximate to the continuously curved surface, the recess having a contact surface operable to assist in removal of the insert from an installed position upon the application of force on the contact surface in a clockwise direction.
2. The thread insert of claim 1, wherein each of the coil sections include a predetermined outer diameter, and each of the coil sections is disposed about a common coil centerline.
3. The thread insert of claim 1, wherein the recess further includes an inner wall positioned at the common coil centerline.
4. The thread insert of claim 3, where the recess further comprises:
- a contact surface; and
- a radial corner joining the inner wall to the contact surface.
5. A method for creating a thread insert, the thread insert including a helical-shaped coil defining a plurality of coil sections including opposing first and second coil end sections, each coil section having an inner and an outer surface, the method comprising:
- creating a continuously curved convex surface at a second coil terminal end section;
- joining the continuously curved surface to the outer surface of the second coil end section to create a tangent point where the continuously curved surface meets the outer surface of the second coil end section at an obtuse angle;
- creating a recess in the second coil end section proximate to the continuously curved surface, said recess including an inner wall proximate positioned substantially at a coil centerline; and
- positioning a contact surface of the recess to assist in removing the insert from an installed position.
6. The method of claim 5, further comprising forming a contact surface with said recess, said contact surface intersecting said inner wall.
7. The method of claim 6, further comprising creating a notch proximate to a bend joining the tang to the first coil end section.
8. The method of claim 5, further comprising tangentially joining the continuously curved surface to the inner surface of the second coil end section to operably create a second tangent point.
9. The method of claim 5, further comprising creating a thread shape at each of the outer and inner surfaces of the coil sections.
10. The method of claim 5, wherein tangentially joining the continuously curved surface to the outer surface of the second coil end section forms a non-sharp tangent point.
11. A thread insert, comprising:
- a helical-shaped insert defining a plurality of coil sections including opposing first and second coil end sections, each coil section having an inner surface and an outer surface defining a thread shape;
- a notch disposed between the inner and outer surfaces in the first coil end section, the first notch proximate to a tang extending inwardly from the first coil end section;
- a continuously curved convex surface at a second coil terminal end section that tangentially meets the outer surface of the second coil end section, wherein the intersection between the continuously curved convex surface and the outer surface intersects at an obtuse angle;
- a recess defined by the second coil section proximate to the continuously curved surface, the recess having a contact surface configured to accept a force to rotate the insert in a clockwise direction and operable to assist in removal of the insert from an installed position; and
- wherein the tang is removable from the insert by mechanical failure at one of the first or second notch.
12. The thread insert of claim 11, wherein each of the coil sections include a predetermined outer diameter, and each of the coil sections is disposed about a common coil centerline.
13. The thread insert of claim 11, wherein the recess further includes an inner wall positioned substantially at the common coil centerline.
14. The thread insert of claim 13, where the recess further comprises a radial corner joining the inner wall to the contact surface.
15. The thread insert of claim 1, wherein the tang extends from the first coil end section, said tang being removable upon the fracture of the insert at the notch.
16. The thread insert of claim 1, wherein the notch is disposed in the first coil end section proximate to the tang and positioned between the inner and outer surfaces.
17. The thread insert of claim 1, wherein each of the inner and outer surfaces define a thread-shape.
18. The thread insert of claim 1, further comprising a second tangent point operably created where the continuously curved surface tangentially meets the inner surface of the second coil end section.
19. A thread insert, comprising:
- a helical-shaped insert defining a plurality of coil sections including opposing first and second coil end sections, each coil section having an inner surface and an outer surface defining a thread shape, said inner surface defining a recess therein, said recess having a contact surface which is substantially perpendicular to a coil section centerline;
- a removable tang radially extending inwardly from the first coil end section;
- a rounded finished terminal end of the second coil end section, the finished terminal end having a continuously curved transverse convex surface at the rounded finished terminal end to ease removal of said insert that blends the inner surface and the outer surface of the second coil end section;
- a tangent point located where the continuously transverse curved convex surface tangentially meets the outer surface of the second coil end section at an obtuse angle; and
- a notch disposed in the first coil end section proximate to the tang and positioned between the inner and outer surfaces, wherein the tang is removable from the insert by mechanical failure at the notch.
20. The thread insert of claim 19, further comprising a second tangent point operably created where the continuously curved surface tangentially meets the inner surface of the second coil end section.
21. The thread insert of claim 19, wherein each of the coil sections include a predetermined outer diameter, and each of the coil sections is disposed about a common coil centerline.
Type: Application
Filed: Jan 3, 2011
Publication Date: Jun 30, 2011
Applicant: NEWFREY LLC (Newark, DE)
Inventors: William Giannakakos (Danbury, CT), William J. Lutkus (Watertown, CT), John F. Carvalho (Danbury, CT)
Application Number: 12/983,364
International Classification: F16B 37/12 (20060101); B21F 3/04 (20060101);