CN112049852A - Plastic self-tapping screw - Google Patents
Plastic self-tapping screw Download PDFInfo
- Publication number
- CN112049852A CN112049852A CN202010950047.XA CN202010950047A CN112049852A CN 112049852 A CN112049852 A CN 112049852A CN 202010950047 A CN202010950047 A CN 202010950047A CN 112049852 A CN112049852 A CN 112049852A
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- Prior art keywords
- screw
- thread
- threaded rod
- teeth
- tapping screw
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- Pending
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- 238000010079 rubber tapping Methods 0.000 title claims abstract description 31
- 229920003023 plastic Polymers 0.000 title claims abstract description 29
- 239000004033 plastic Substances 0.000 title claims abstract description 29
- 230000007704 transition Effects 0.000 claims abstract description 6
- 230000004323 axial length Effects 0.000 claims description 3
- 238000000034 method Methods 0.000 claims 1
- 230000003247 decreasing effect Effects 0.000 abstract description 4
- 230000013011 mating Effects 0.000 description 6
- 230000009286 beneficial effect Effects 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 230000002079 cooperative effect Effects 0.000 description 2
- 230000001627 detrimental effect Effects 0.000 description 2
- 230000010006 flight Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 230000003796 beauty Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 230000005389 magnetism Effects 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Images
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
- F16B25/00—Screws that cut thread in the body into which they are screwed, e.g. wood screws
- F16B25/0036—Screws that cut thread in the body into which they are screwed, e.g. wood screws characterised by geometric details of the screw
- F16B25/0078—Screws that cut thread in the body into which they are screwed, e.g. wood screws characterised by geometric details of the screw with a shaft of non-circular cross-section or other special geometric features of the shaft
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
- F16B25/00—Screws that cut thread in the body into which they are screwed, e.g. wood screws
- F16B25/0036—Screws that cut thread in the body into which they are screwed, e.g. wood screws characterised by geometric details of the screw
- F16B25/0042—Screws that cut thread in the body into which they are screwed, e.g. wood screws characterised by geometric details of the screw characterised by the geometry of the thread, the thread being a ridge wrapped around the shaft of the screw
- F16B25/0047—Screws that cut thread in the body into which they are screwed, e.g. wood screws characterised by geometric details of the screw characterised by the geometry of the thread, the thread being a ridge wrapped around the shaft of the screw the ridge being characterised by its cross-section in the plane of the shaft axis
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
- F16B25/00—Screws that cut thread in the body into which they are screwed, e.g. wood screws
- F16B25/10—Screws performing an additional function to thread-forming, e.g. drill screws or self-piercing screws
- F16B25/103—Screws performing an additional function to thread-forming, e.g. drill screws or self-piercing screws by means of a drilling screw-point, i.e. with a cutting and material removing action
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- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Geometry (AREA)
- Mechanical Engineering (AREA)
- Connection Of Plates (AREA)
Abstract
The invention discloses a plastic self-tapping screw, comprising: the threaded rod core is formed by splitting a cylinder into two halves through an axis, and then respectively forming the threaded rod core by radial deviation combination in opposite directions around the axis, when the threaded rod core extends downwards from the head of the threaded part, the threaded rod core initially consists of two half semi-cylinders with constant diameters, and after the threaded rod core extends to a region without screw teeth, the threaded rod core is formed into a complete cylinder through cone angle transition; a first screw tooth of a plurality of circular tooth crests formed at a portion of the threaded rod extending directly below the screw head; a second plurality of spiral teeth having a circular crest, the height of which is gradually decreased toward the end surface of the rod tail end portion and which is formed continuously with the first spiral teeth; the tail end of the screw thread piece is provided with a cutting groove which extends longitudinally and has a certain length; the tail end of the threaded rod is provided with a cylindrical guide rod. The screw of the present invention obtains an optimum screwing performance while ensuring the integrity of the formed internal thread profile, mechanical strength, load capacity, deformation resistance, and safety against accidental disengagement in the mounting hole.
Description
Technical Field
The invention relates to a plastic self-tapping screw which cuts an internal thread into a mounting hole of a plastic mating member when screwed into the mounting hole.
Background
Since the 70 s of the last century, plastic products are applied in industry and life in large scale, and plastic screws have high-quality characteristics of insulation, no magnetism, corrosion resistance, beauty, no rust and the like, so the plastic screws can be used in many fields.
The self-tapping quality of the self-tapping screw part formed by plastic is poor, the screw used in cooperation with the plastic part is generally a steel self-tapping screw, and the self-tapping screw is distinguished from an extrusion type self-tapping screw and a cutting type self-tapping screw according to the type of internal threads of an inner hole of a forming counterpart. Common plastics are with cutting self-tapping screw for steel self-tapping screw, and the screw afterbody has a cutting flutes for the whorl of cutting flutes position possesses the cutting action, when the screw thread selects into the counterpart hole, in order to play the cutting hole and form the effect that the internal thread accomplishes the assembly fastening, and these screw threads are not formed by plastics.
For example, CN101216062B discloses a self-tapping screw having a uniquely formed thread profile that is specifically designed to perform the self-tapping function. But because the whole threaded rod is in the profile shape, the thread bearing area is correspondingly reduced, and the thread bearing capacity is reduced.
Further improvements are desirable when in practice self-tapping screws formed of plastic are used. During the formation of the thread, the strength and load capacity of the threaded element and the counterpart are adversely affected by the grooving or clamping action. Furthermore, the resistance to deformation and the stability of the screw are not always satisfactory. Finally, even if the thread torque is small, maximum safety should be ensured to prevent the screw from being accidentally disengaged from the mounting hole of the counterpart.
Disclosure of Invention
The purpose of the invention is as follows: an object of the present invention is to solve the drawbacks of the prior art and to provide a plastic self-tapping screw which obtains an optimum screwing performance while ensuring the integrity of the profile of the formed female screw, mechanical strength, load capacity, deformation resistance and safety against accidental disengagement when the female screw is cut into a mounting hole of a counterpart by screwing the female screw into the mounting hole of a plastic counterpart.
The technical scheme is as follows: the invention relates to a plastic self-tapping screw, comprising:
the threaded rod core is formed by splitting a cylinder into two halves through an axis, and then respectively forming the threaded rod core by radial deviation combination in opposite directions around the axis, when the threaded rod core extends downwards from the head of the threaded part, the threaded rod core initially consists of two half semi-cylinders with constant diameters, and after the threaded rod core extends to a region without screw teeth, the threaded rod core is formed into a complete cylinder through cone angle transition;
a first screw tooth of a plurality of circular tooth crests formed at a portion of the threaded rod extending directly below the screw head;
a second plurality of spiral teeth having a circular crest, the height of which is gradually decreased toward the end surface of the rod tail end portion and which is formed continuously with the first spiral teeth;
the tail end of the screw thread piece is provided with a cutting groove which extends longitudinally and has a certain length;
the tail end of the threaded rod is provided with a cylindrical guide rod.
Further, a plurality of the first screw teeth each have the same height Z.
Further, the height of the second screw is smaller than the height of the first screw.
Further, the axial length of the second screw tooth is 1 to 3 times the length of the pitch P of the adjacent screw teeth in the cross section.
Further, the first thread has a cross section of a bilaterally symmetrical shape, and the thread angle β is between 26 ° and 30 °.
Further, the screw thread and the screw tooth form a helical gap, and the volume of the gap is larger than that of the screw thread.
Further, the thread bottoms of the first and second threads are transitionally joined with the thread flanks by an arc R2.
Further, P, Z, R1 and R2 take the following values:
P=1.0 mm /1.25 mm /1.5 mm /1.75 mm /2.0 mm /2.5mm
Z=0.33P
R1=0.5Z
R2=0.3Z
where P is the pitch of adjacent teeth in the cross-section, Z is the height of the first tooth, R1 is the radius of curvature of the rounded crest, and R2 is the radius of the transition arc between the bottom of the tooth and the flank of the tooth.
Furthermore, the bottom surface of the cutting groove forms an included angle with the axis, the included angle ranges from 10 degrees to 20 degrees, and the length L of the cutting groove is 3 times to 5 times of tooth pitch.
Furthermore, the diameter D of the cylindrical guide rod is the diameter of the inscribed circle of the threaded rod core, and the length l of the cylindrical guide rod is 0.2 to 0.5 times of the nominal diameter D of the thread.
Has the advantages that: the invention has the following beneficial effects:
(1) the invention uses a relatively small profile angle, and when the thread is screwed into the mounting hole of the mating part, the thread exerts a relatively large axial force and a small radial force; the relatively low radial force and the relatively large radius R1 ensure that the plastic screw is screwed into the mounting hole of the fitting with minimal grooving without exerting any pressure required for detrimental screwing;
(2) according to the thread and the profile shape of the screw, the screw is formed by radially connecting two semicylinders around the axis of the screw in an offset manner, when the screw rotates around the axis, a cutting edge and a clearance angle are formed, the surface of the screw is connected with the thread with constant height, so that the integral thread profile enables the screw to have the characteristic, and the generation of the clearance angle can greatly reduce the friction resistance of the thread piece after tapping into the inner hole of the mating piece, thereby being beneficial to the thread piece penetrating into the material of the mating piece;
(3) according to the present invention, due to the cooperative action between the reduced height external thread formed with the height gradually reduced and the arc-shaped faces formed at the reduced height external thread and the constant height external thread flights, the stress acting on the counterpart at the initial stage of screwing can be released and the internal thread can be smoothly formed; therefore, the screwing torque at the initial stage can be reduced.
Drawings
FIG. 1 is a front view of the structure of one embodiment of the present invention;
FIG. 2 is a cross-sectional view of an embodiment of the invention at a first thread;
FIG. 3 is a cross-sectional view at a second thread of an embodiment of the present invention;
FIG. 4 is a bottom view of the structure of an embodiment of the present invention;
FIG. 5 is a schematic diagram of an exemplary embodiment of a terminal structure;
fig. 6 is a schematic perspective view of an embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
As shown in fig. 1 to 6, an embodiment of the present invention provides a plastic self-tapping screw, including:
the screw rod core 1 is formed by splitting a cylinder into two halves through an axis 9 and then respectively forming the two halves of the cylinder in an opposite radial offset combination around the axis 9, and when the screw rod core extends downwards from the head of a screw piece, the screw rod core initially consists of two halves of semi-cylinders with constant diameters, and after the two halves of semi-cylinders extend to a region without screw teeth, the two halves of semi-cylinders are transited by a cone angle to form a complete cylindrical guide rod 8;
a first thread 4 having a plurality of circular crests of constant-height external threads, the plurality of first threads 4 each having the same thread height Z and being formed at a portion of the threaded rod extending directly below the screw head;
and a second thread 3 having a plurality of rounded crests of a reduced-height external thread, the thread height gradually decreasing toward the end face of the rod tail end portion and being formed continuously with the first thread 4 of the rounded crests of the constant-height external thread;
the end of the screw member is provided with a length of longitudinally extending cutting grooves 7, the number of cutting grooves 7 preferably being four. The cutting groove 7 is cut to provide a cutting edge for the screw thread at the position thereof, the screw member cuts the internal thread into the mounting hole when being screwed into the mounting hole, and the screw thread provides a special cross-sectional profile shape to reduce the tapping torque for tapping the internal thread.
The tail end of the threaded rod is provided with a cylindrical guide rod 8.
As a further optimization of the above embodiment:
preferably, in the present embodiment, each of the first screw teeth 4 has the same height Z; further, the height of the second screw teeth 3 is smaller than the height of the first screw teeth 4.
In the present embodiment, the axial length of the second thread 3 is preferably 1 to 3 times the length of the pitch P of the adjacent cross-sectional threads.
Preferably, in this embodiment, as shown in fig. 2, said first thread 4 has a section with a double line symmetry shape, with a thread angle β between 26 ° and 30 °, preferably 28 °.
Preferably, in this embodiment, the screw thread and the screw thread form a helical gap, the volume of which is greater than the volume of the thread.
Preferably, in the present exemplary embodiment, the thread bottoms 6 of the first and second threads 4, 3 merge with the thread flanks 5 via a circular arc R2.
Preferably, P, Z, R1 and R2 take the following values in this embodiment:
P=1.0 mm /1.25 mm /1.5 mm /1.75 mm /2.0 mm /2.5mm
Z=0.33P
R1=0.5Z
R2=0.3Z
where P is the pitch of adjacent teeth in the cross-section, Z is the height of the first tooth 4, R1 is the radius of curvature of the rounded crest, and R2 is the radius of the transition arc between the tooth bottom 6 and the tooth flank 5.
With a relatively small profile angle, the thread exerts a relatively large axial force, and a small radial force, when screwed into the mounting hole of the counterpart. The relatively low radial force and the relatively large radius R1 ensure that the plastic screw is screwed into the mounting hole of the fitting with minimal grooving without exerting any pressure required for detrimental screwing.
In the present embodiment, preferably, as shown in fig. 1, the bottom surface of the cutting groove 7 forms an included angle with the axis, which is in the range of 10 ° to 20 °, and the length L of the cutting groove 7 is 3 times to 5 times of the pitch.
In the present embodiment, preferably, as shown in fig. 4, the diameter D of the cylindrical guide rod 8 is the diameter of the inscribed circle of the threaded rod core, and the length l thereof is 0.2 to 0.5 times the nominal diameter D of the thread.
According to the thread and the profile shape of the screw, the screw is formed by radially connecting two semicylinders around the axis of the screw in an offset manner, when the screw rotates around the axis, a cutting edge and a clearance angle are formed, the surface of the screw is connected with the thread with constant height, so that the integral thread profile enables the screw to have the characteristic, and the clearance angle can be generated to greatly reduce the friction resistance of the thread piece after the thread piece is tapped into the inner hole of the mating piece, thereby being beneficial to the thread piece to penetrate into the material of the mating piece. The cutting geometry of the thread profile is shown in the figures.
According to the present invention, stress acting on the counterpart at the initial stage of screwing can be released and the internal thread can be smoothly formed due to the cooperative action between the reduced-height external thread formed with a gradually decreasing height and the arc-shaped surfaces formed at the reduced-height external thread and the constant-height external thread flights. Therefore, the screwing torque at the initial stage can be reduced.
Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A plastic self-tapping screw characterized in that: the method comprises the following steps:
the threaded rod core (1) is formed by splitting a cylinder into two halves through an axis (9) and then respectively forming a combination by offsetting in opposite radial directions around the axis (9), and when the threaded rod core extends downwards from the head of a threaded part, the threaded rod core initially consists of two half semi-cylinders with constant diameters, and after the threaded rod core extends to a region without threads, the threaded rod core is formed into a complete cylinder through cone angle transition;
a first plurality of screw teeth (4) having a circular tooth top formed at a portion of the threaded rod extending directly below the screw head;
a plurality of second screw teeth (3) having a circular crest, the height of which is gradually reduced toward the end surface of the rod tail end portion and which are formed continuously with the first screw teeth (4);
the tail end of the screw thread piece is provided with a cutting groove (7) which extends longitudinally and has a certain length;
the tail end of the threaded rod is provided with a cylindrical guide rod (8).
2. A plastic self-tapping screw as in claim 1, wherein: the first helical teeth (4) each have the same height Z.
3. A plastic self-tapping screw as in claim 1, wherein: the height of the second screw teeth (3) is smaller than the height of the first screw teeth (4).
4. A plastic self-tapping screw as in claim 1, wherein: the axial length of the second spiral tooth (3) is 1 to 3 times the length of the pitch P between adjacent spiral teeth on the cross section.
5. A plastic self-tapping screw as in claim 1, wherein: the first thread (4) has a section with a double-line symmetrical shape, the thread angle beta being between 26 DEG and 30 deg.
6. A plastic self-tapping screw as in claim 1, wherein: the screw thread and the screw teeth form a helical gap, the volume of which is greater than the volume of the screw thread.
7. A plastic self-tapping screw as in claim 1, wherein: the thread bottoms (6) of the first threads (4) and the second threads (3) are in transitional joint with the thread sides (5) through an arc R2.
8. A plastic self-tapping screw as in claim 1, wherein: p, Z, R1 and R2 take the following values:
P=1.0 mm /1.25 mm /1.5 mm /1.75 mm /2.0 mm /2.5mm
Z=0.33P
R1=0.5Z
R2=0.3Z
wherein P is the pitch of adjacent threads in cross section, Z is the height of the first thread (4), R1 is the radius of curvature of the rounded crest, R2 is the radius of the transition arc between the thread bottom (6) and the thread flank (5).
9. A plastic self-tapping screw as in claim 1, wherein: the bottom surface of the cutting groove (7) forms an included angle with the axis, the included angle ranges from 10 degrees to 20 degrees, and the length L of the cutting groove (7) is 3 times to 5 times of tooth pitch.
10. A plastic self-tapping screw as in claim 1, wherein: the diameter D of the cylindrical guide rod (8) is the diameter of an inscribed circle of the threaded rod core, and the length l of the cylindrical guide rod is 0.2 to 0.5 times of the nominal diameter D of the thread.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010950047.XA CN112049852A (en) | 2020-09-11 | 2020-09-11 | Plastic self-tapping screw |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010950047.XA CN112049852A (en) | 2020-09-11 | 2020-09-11 | Plastic self-tapping screw |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN112049852A true CN112049852A (en) | 2020-12-08 |
Family
ID=73610668
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202010950047.XA Pending CN112049852A (en) | 2020-09-11 | 2020-09-11 | Plastic self-tapping screw |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN112049852A (en) |
-
2020
- 2020-09-11 CN CN202010950047.XA patent/CN112049852A/en active Pending
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