Patent Description:
As shown in <FIG>, a conventional screw <NUM> includes a head <NUM>, a shank <NUM> axially extending from the screw head <NUM>, a leading end <NUM> connecting the shank <NUM> oppositely to the screw head <NUM>. A thread <NUM> extends helically around the shank <NUM>. Two flutes <NUM> are indented inwardly and inclinedly into the shank <NUM> and the leading end <NUM>. One of the flutes <NUM> criss-crosses with an upper part of the thread <NUM> around the shank <NUM>. The other one of the flutes <NUM> criss-crosses with a part of the thread <NUM> in proximity to the leading end <NUM>.

When the leading end <NUM> is advanced into a workpiece, a thread hole of the workpiece is formed, and the scraps of the workpiece are discharged through the flutes <NUM>. As such, the scraps are prevented from adversely affecting the drilling operation of the conventional screw <NUM>.

However, when the conventional screw <NUM> is advanced into a composite workpiece, the scraps may be accumulated in the flutes <NUM> to reduce the cutting efficiency of the leading end <NUM>. Therefore, torsional force required for continued advancing operation of the the conventional screw <NUM> is increased. Overly large torsional forces may cause cracks to the composite workpiece. The document <CIT> discloses a further example of a prior art screw.

Therefore, an object of the disclosure is to provide a screw that can efficiently collect and discharge scraps so that it can be driven into a workpiece with less torsional forces.

According to the disclosure, a screw includes a head, a shank, and at least one collecting groove.

The shank extends axially and downwardly from the head, and includes a leading end opposite to the head, and a thread unit extending helically around an axis of the shank.

The at least one collecting groove is disposed on the shank between the leading end and the head for collecting scraps and does not criss-crosses with crests of the thread unit.

Other features and advantages of the disclosure will become apparent in the following detailed description of the embodiments with reference to the accompanying drawings, of which:.

Only <FIG> and <FIG>, <FIG>, <FIG> and <FIG> show embodiments of the invention.

<FIG> illustrates a screw according to a first embodiment of the disclosure. The screw includes a head <NUM>, a shank <NUM> extending axially from the head <NUM> and including a leading end <NUM>, and a thread unit <NUM> extending helically around an axis (L) of the shank <NUM>.

The shank <NUM> includes a grooved section <NUM>, an upper section <NUM>, and a lower section <NUM>. The grooved section <NUM> extends circumferentially above the leading end <NUM> and has a collecting groove <NUM> indented inwardly and radially of the shank <NUM>. The collecting groove <NUM> is disposed around the axis (L) of the shank <NUM> in a non-helical fashion above the lower section <NUM> for collecting scraps, and does not criss-cross with crests of the thread unit <NUM>. In this embodiment, the collecting groove <NUM> extends continuously around the axis (L) of the shank <NUM> by an angle of <NUM> degrees.

The upper section <NUM> is disposed between the grooved section <NUM> and the head <NUM>. The lower section <NUM> is disposed below the grooved section <NUM> and has the leading end <NUM> and a flute <NUM>. The collecting groove <NUM> extends non-helically above the flute <NUM>, and has a groove open end <NUM> that faces in a radially outwards direction, a groove bottom wall <NUM> opposite to the groove open end <NUM>, and an upper groove boundary wall <NUM> that extends from an upper end of the groove bottom wall <NUM> to the groove open end <NUM> and that extends around the axis (L) of the shank <NUM> in a non-helical manner. A lower groove boundary wall <NUM> extends from a lower end of the groove bottom wall <NUM> to the groove open end <NUM> and also extends around the axis (L) of the shank <NUM> in a non-helical manner.

The thread unit <NUM> includes an upper thread <NUM> formed in the upper section <NUM>, and a lower thread <NUM> formed in the lower section <NUM>. The shank <NUM> has a portion with a circumferential surface 3a having the largest diameter of the shank <NUM> except the crest diameter of the thread unit <NUM>. The groove bottom wall <NUM> of the collecting groove <NUM> is deeper in a radial direction than the circumferential surface 3a when measured from crests of the thread unit <NUM>. In this embodiment, the upper thread <NUM> is a straight thread, and the lower thread <NUM> is a tapered thread. The root diameter of the upper thread <NUM> is the largest diameter of the shank <NUM> except the crest diameter of the upper thread <NUM>, and the circumferential surface 3a is the surface where the root of the upper thread <NUM> is situated. The maximum root diameter of the tapered lower thread <NUM> is also the largest diameter of the shank <NUM> except the crest diameter of the upper thread <NUM> or the maximum crest diameter of the tapered lower thread <NUM>. Thus, the circumferential surface 3a can also be the surface where the maximum root diameter of the tapered lower thread <NUM> is situated. The groove bottom wall <NUM> is deeper than the circumferential surface 3a. Note that the grooved section <NUM> is more proximate to the leading end <NUM> than the head <NUM>.

Based on a thickness of a working piece <NUM> (see <FIG>), the axial length of the collecting groove <NUM> can be varied to achieve an optimum result. However, the axial length of the collecting groove <NUM> should be limited not to exceed the thickness of the workpiece <NUM>.

The flute <NUM> of the lower section <NUM> extends in parallel with the axis (L) of the shank <NUM> and communicates with the collecting groove <NUM>. To be more effective for collection of the scraps, an indented depth of the collecting groove <NUM> from the circumferential surface 3a can be enlarged as desired as long as the depth will not harm the torsional strength of the shank <NUM>. In addition, the bottom of the flute <NUM> may be a curved recess, or a recess with right angled or non-right angled corners.

As shown in <FIG>, the workpiece <NUM> is composed of a wood plate <NUM> and a metal plate <NUM> stacked on each other. When the leading end <NUM> is advanced to the metal plate <NUM> through the wood plate <NUM>, because the flute <NUM> communicates with the collecting groove <NUM>, a large amount of the scraps from the wood plate <NUM> are collected in the collecting groove <NUM>, so that the scraps are not seriously accumulated in the flute and/or helical groove. As such, the cutting edge of the leading end <NUM> or the thread unit <NUM> will not get stuck or buried in scraps. This effect is advantageous to advance further the leading end <NUM> into the metal plate <NUM>, which is harder than the wood plate <NUM>. During drilling operation, the leading end <NUM> of the lower section <NUM> and the thread unit <NUM> form a drilled hole <NUM> in the workpiece <NUM>. The drilled hole <NUM> has a hole diameter greater than a diametrical width of the grooved section <NUM>. Therefore, the collecting groove <NUM> is sufficient to collect the scraps. Moreover, because the hole diameter of the drilled hole <NUM> is greater than the diametrical width of the grooved section <NUM>, the groove bottom wall <NUM> of the collecting groove <NUM> is not in contact with a hole boundary of the drilled hole <NUM>. Therefore, during the drilling operation, frictional resistance can be lowered and torsional forces required for driving the screw of the disclosure can be reduced.

<FIG> illustrates a variant of the first embodiment, which differs from that shown in <FIG> in that the flute <NUM> of the lower section <NUM> extends inclinedly relative to the axis (L) of the shank <NUM>. This variant facilitates effective discharge of the scraps from the flute <NUM> into the collecting groove <NUM>.

<FIG> illustrate other variants of the first embodiment.

As shown in <FIG> and <FIG>, the lower section <NUM> includes two flutes <NUM> that are symmetrically disposed in a spaced apart manner on two opposite sides of the axis (L) of the shank <NUM> and that communicate with the collecting groove <NUM>.

As shown in <FIG>, the lower section <NUM> includes two flutes <NUM> axially extending in a spaced-apart manner on a side of the axis (L) of the shank <NUM>. The flutes <NUM> both communicate with the collecting groove <NUM>.

As shown in <FIG>, the lower section <NUM> includes two flutes <NUM> axially extending in a spaced apart manner on a side of the axis (L) of the shank <NUM>, but only one of the flutes <NUM> communicates with the collecting groove <NUM>.

As shown in <FIG>, the lower section <NUM> includes two flutes <NUM> angularly spaced apart from each other, disposed symmetrically at two opposite sides of the axis (L) of the shank, and communicating with the collecting groove (<NUM>).

As shown in <FIG>, the lower section <NUM> includes a single one flute <NUM> that extends helically relative to the axis (L) of the shank <NUM> and that communicates with the collecting groove <NUM>.

As shown in <FIG>, the lower section <NUM> includes two flutes <NUM>. One of the flutes <NUM> extends in parallel with the axis (L) of the shank <NUM> and communicates with the collecting groove <NUM>. The other one of the flutes <NUM> extends helically relative to the axis (L) of the shank <NUM> and does not communicate with the collecting groove <NUM>.

As shown in <FIG>, the shank <NUM> further includes two fins <NUM> that are disposed between the collecting groove <NUM> and the thread unit <NUM> formed in the upper section <NUM> above the collecting groove <NUM>. The fins <NUM> extend from the circumferential surface 3a in opposite directions. A diametral distance (d') between the extremities of the fins <NUM> is smaller than a major diameter (D) of the thread unit <NUM>.

As shown in <FIG>, the shank <NUM> further includes two fins <NUM> that are disposed between the leading end <NUM> and the collecting groove <NUM>. The fins <NUM> extend in opposite directions with respect to the axis (L) of the shank <NUM>.

As shown in <FIG> and <FIG>, the shank <NUM> further includes two fins <NUM> disposed between the collecting groove <NUM> and the thread unit <NUM> formed above the collecting groove <NUM>. The fins <NUM> extend from the circumferential surface 3a in opposite directions.

As shown in <FIG>, the shank <NUM> further includes two fins <NUM> disposed between two consecutive crests of the thread unit <NUM> and extending from the circumferential surface 3a in opposite directions.

Noticeably, the leading end <NUM> of the lower section <NUM> may have any one of tapping or drilling end configurations and is not limited to the tapping or drilling configurations in the disclosure. The number of the flutes <NUM> formed in the lower section <NUM> and the number of the flutes <NUM> in communication with the collecting groove <NUM> are not limited to those disclosed herein. In use, the fins <NUM> facilitate hole enlargement operation.

<FIG> illustrates another variant of the first embodiment. While the collecting groove <NUM> as shown in <FIG> is indented inwardly in a stepped manner by lathing, milling, cutting, grinding and rolling, the collecting groove <NUM> in this variant is indented gradually and inwardly by forging, rolling, twisting, stamping, and lathe trimming.

<FIG> and <FIG> illustrate two other additional variants of the first embodiment. To save processing and manufacturing cost, the flute <NUM> and the collecting groove <NUM> are formed so as to be in direct communication with each other by forging, grinding, rolling twisting, stamping, lathe trimming, and cutting. Particularly, the flute <NUM> of the lower section <NUM> extends inclinedly or helically relative to an axis (L) of the shank <NUM> and communicates directly with the collecting groove <NUM>. In <FIG>, the groove bottom wall <NUM> of the collecting groove <NUM> is flush with the outer surface of the leading end <NUM>. Thus, the collecting groove <NUM> has only the upper groove boundary wall <NUM>, and no lower groove boundary wall is formed for the collecting groove <NUM>.

<FIG> and <FIG> illustrate a screw according to a second embodiment of the disclosure. The differences between the first and second embodiments resides in that the screw includes two collecting grooves <NUM> (only one shown in <FIG>). The collecting grooves <NUM> are spaced apart circumferentially and non-helically around the axis (L) of the shank <NUM> by an equiangular distance. An angular length (θ) of each collecting groove <NUM> ranges between <NUM> and <NUM> degrees. In this embodiment, the angular length (θ) of each collecting groove <NUM> is larger than <NUM>, but smaller than <NUM> degrees. Each collecting groove <NUM> has a cross sectional shape that resembles a shape of a circular segment and that is formed on a cross sectional plane perpendicular to the axis (L) of the shank <NUM>. The non-hollow part of the grooved section <NUM> of the shank <NUM> thus has a four-sided cross section defined by two opposite arcs and two opposite chords. In other variants of this embodiment, three or more collecting grooves <NUM> are formed circumferentially around the axis (L) of the shank <NUM> at equiangular interval. Each collecting groove <NUM> of this embodiment has a receiving space with a volume smaller that that of the collecting groove <NUM> of the first embodiment. However, the entire structural strength can be enhanced to meet other requirements.

<FIG> illustrates a screw according to a third embodiment of the disclosure. The difference between the first and third embodiments resides in that the thread unit <NUM> has only the lower thread <NUM> disposed at the lower section <NUM>. The groove bottom wall <NUM> is deeper than the circumferential surface 3a with a diameter which is the largest except the maximum crest diameter of the tapered lower thread <NUM>. In use, the torsional force required for driving the screw can be effectively reduced through the collecting groove <NUM>, and the lower thread <NUM> is mainly used for screwing into the workpiece. Under condition that only a low pulling force is required, the lower thread <NUM> at the lower section <NUM> is sufficient to secure the workpiece. In this embodiment, the axial length (Z) of the collecting groove <NUM> is greater than or equal to a root diameter (Y) of the upper section <NUM>, so that the volume of collecting groove <NUM> is assuredly sufficient for collection of the scraps.

<FIG> and <FIG> illustrate a screw according to a fourth embodiment of the disclosure, which has a structure generally similar to that of the third embodiment. However, in this embodiment, the thread unit <NUM> further has an auxiliary thread <NUM> disposed at the grooved section <NUM>. The auxiliary thread <NUM> has a major diameter (d) smaller than a maximum major diameter (D) of the lower thread <NUM> which is tapered. In use, not only the scraps can be accumulated in the collecting groove <NUM>, the auxiliary thread <NUM> can provide an additional capturing force to secure the workpiece and to increase a pulling strength of the screw of the embodiment. While the auxiliary thread <NUM> as shown in <FIG> is distributed in full length of the grooved section <NUM>, it is not limited thereto. For example, the auxiliary thread <NUM> as shown in <FIG> is distributed in one half the axial length of the grooved section <NUM>.

<FIG> illustrates a screw according to a fifth embodiment of the disclosure, which has a structure generally similar to that of the fourth embodiment. However, in this embodiment, the thread unit <NUM> further has the upper thread <NUM> formed at the upper section <NUM>. The major diameter (d) of the auxiliary thread <NUM> smaller than a major diameter (D') of the upper thread <NUM>. In addition, the auxiliary thread <NUM> has a root diameter smaller than that of the upper thread <NUM>. As the screw of the disclosure is driven more deeply into a workpiece, the upper thread <NUM> can enhance the pulling force of the screw and optimize the locking force thereof.

<FIG> illustrates a screw according to a sixth embodiment of the disclosure. The difference between the sixth and first embodiments resides in that the sixth embodiment further includes ribs <NUM> protruding outwardly from the lower section <NUM> and extending transversely between two consecutive crests of the lower thread <NUM> formed in the lower section <NUM>. As the lower thread <NUM> is screwed in, it provides a hole-enlarging effect along with its hole-forming action, thereby reducing resistance against advancement of the shank <NUM>, as well as a subsequent cutting range. Therefore, less effort is required for the screwing movement. Specifically, because the rib <NUM> are disposed in the lower section <NUM> and produces the hole enlargement effect, a clearance can be formed between the upper section <NUM> and the workipiece to provide an extra space for collecting scraps. In this embodiment, the flute <NUM> of the lower section <NUM> extends across the consecutive crests of the lower thread <NUM> and directly adjoins the collecting groove <NUM>. Thus, an axial length of the flute <NUM> is greater than that of the ribs <NUM>. Noteworthy, to produce the hole enlargement effect, the ribs <NUM> are not limited to be disposed only on the lower section <NUM>.

<FIG> illustrates a screw according to a seventh embodiment of the disclosure. The difference from the first embodiment resides in that the seven embodiment includes a reverse thread <NUM> formed on the lower section <NUM> and extending spirally in a reverse direction that is opposite to the direction of the lower thread <NUM> of the thread unit <NUM>. The reverse thread <NUM> functions to produce a hole enlargement effect. In this embodiment, the flute <NUM> of the lower section <NUM> extends through the reverse thread <NUM> and connects the collecting groove <NUM>. While the reverse thread <NUM> of this embodiment is disposed on the lower section <NUM>, it is not limited hereto and the number of the reverse thread <NUM> may be varied.

<FIG> illustrates a screw according to an eighth embodiment of the disclosure. The difference of the eighth embodiment from the first embodiment resides in that the eighth embodiment includes multi-start short turn threads <NUM> formed in the lower section <NUM> and arranged spirally around the axis (L) of the shrank <NUM>. The multi-start short turn threads <NUM> are disposed between the flute <NUM> of the lower section <NUM> and the collecting groove <NUM> to produce the hole enlargement effect. In some variants of this embodiment, the flute <NUM> may extend across the multi-start threads <NUM> to be in communication with the collecting groove <NUM>.

<FIG> illustrates a screw according to a ninth embodiment of the disclosure. The difference of the ninth embodiment from the first embodiment resides in that the grooved section <NUM> is more proximate to the head <NUM> than the leading end <NUM>. The lower thread <NUM> formed in the lower section <NUM> includes a tapered thread portion <NUM> formed in the leading end <NUM> and a straight thread portion <NUM> formed above the tapered thread portion <NUM>. The groove bottom wall <NUM> is deeper than the circumferential surface 3a having the root diameter of the straight thread portion <NUM> of the lower thread <NUM>, which is the largest except the crest diameter of the straight thread portion <NUM>. The flute <NUM> extends across the tapered thread portion <NUM> of the lower thread <NUM>. Note that the collecting groove <NUM> is more proximate to the head <NUM> than the leading end <NUM>.

<FIG> illustrates a screw according to a tenth embodiment of the disclosure. The difference of the tenth embodiment from the first embodiment resides in that the thread unit <NUM> has only the lower thread <NUM> formed at the lower section <NUM>; the grooved section <NUM> has a top end proximate to the head <NUM> and a bottom end proximate to the leading end <NUM> of the lower section <NUM>. The top end has the upper groove boundary wall <NUM>, and the bottom end has the lower groove boundary wall <NUM>. The collecting groove <NUM> therefore has an increased axial length and provides an increased receiving space to collect a larger amount of scraps. This embodiment is suitable for advancing into a larger depth. The groove bottom wall <NUM> of the collecting groove <NUM> is deeper than the circumferential surface 3a having the maximum root diameter of the tapered lower thread <NUM>, which is the largest except the the maximum crest diameter of the lower thread <NUM>.

<FIG> illustrates a screw according to an eleventh embodiment of the disclosure. The difference of the eleventh embodiment from the tenth embodiment resides in that the thread unit <NUM> additionally has an auxiliary thread <NUM>, which is a straight thread and is formed at the grooved section <NUM>. The auxiliary thread <NUM> has a root diameter smaller than the maximum root diameter of the lower thread <NUM>. The auxiliary thread <NUM> can enhance the effect of grasping and securing the workpiece.

<FIG> illustrates a variant of the eleventh embodiment. In this variant, the lower thread <NUM> is omitted from the lower section <NUM>. The groove bottom wall <NUM> of the collecting groove <NUM> is deeper than the circumferential surface 3a with the largest diameter of the shank <NUM>, which is the largest except the crest diameter of the auxiliary thread <NUM>.

<FIG> illustrates a screw according to a twelfth embodiment of the disclosure. The difference of the twelfth embodiment from the first embodiment resides in that the twelfth embodiment includes a plurality of grooved sections <NUM> and a plurality of the upper sections <NUM> each formed with the upper thread <NUM> of the thread unit <NUM>, and a plurality of trenches <NUM>. In this embodiment, the grooved sections <NUM> are axially spaced apart from each other, and each upper section <NUM> is disposed between two of the grooved sections <NUM>. Each trench <NUM> extends across the upper thread <NUM> formed on one of the upper section <NUM> to communicate with two of the grooved section <NUM>. By virtue of the tranches <NUM>, the collecting grooves <NUM> can communicate with each other.

<FIG> illustrates a screw according to a thirteenth embodiment of the disclosure. The difference of the thirteenth embodiment from the twelfth embodiment resides in that the tranches <NUM> are omitted. As such, the collecting grooves <NUM> are disconnected from each other.

Claim 1:
A screw with
a head(<NUM>);
a shank (<NUM>) extending axially and downwardly from said head (<NUM>), and including a leading end (<NUM>) opposite to said head (<NUM>), and a thread unit (<NUM>) extending helically around an axis (L) of said shank (<NUM>); and
at least one collecting groove (<NUM>) that is disposed on said shank (<NUM>) between said leading end (<NUM>) and said head (<NUM>) for collecting scraps and that does not criss-cross with crests of said thread unit (<NUM>);
wherein said leading end (<NUM>) has at least one flute (<NUM>) to communicate with said at least one collecting groove (<NUM>);
wherein said at least one collecting groove (<NUM>) extends non-helically above said at least one flute (<NUM>), said at least one collecting groove (<NUM>) defining a groove open end (<NUM>) that faces in a radially outwards direction, a groove bottom wall (<NUM>) opposite to said groove open end (<NUM>), and an upper groove boundary wall (<NUM>) that extends from an upper end of said groove bottom wall (<NUM>) to said groove open end (<NUM>) and that extends around the axis (L) of said shank (<NUM>) in a non-helical manner;
wherein said shank (<NUM>) includes a portion with a circumferential surface (3a) which has a largest diameter of said shank (<NUM>) except a crest diameter of said thread unit (<NUM>), said groove bottom wall (<NUM>) of said least one collecting groove (<NUM>) being deeper in a radial direction than said circumferential surface (3a) when measured from crests of said thread unit (<NUM>); wherein said shank (<NUM>) further includes at least one grooved section (<NUM>) extending circumferentially and having said at least one collecting groove (<NUM>), at least one upper section (<NUM>) disposed between said at least one grooved section (<NUM>) and said head (<NUM>), and a lower section (<NUM>) disposed below said at least one grooved section (<NUM>) and having said leading end (<NUM>);
characterized in that
said thread unit (<NUM>) has a lower thread (<NUM>) disposed at said lower section (<NUM>); and wherein said leading end (<NUM>) is tapered and has a pointed tip, said lower thread (<NUM>) extending helically toward said pointed tip of said leading end (<NUM>), said at least one flute (<NUM>) extending across said lower thread (<NUM>) and having a flute upper end that meets and communicates said at least one collecting groove (<NUM>) and a flute lower end that meets said pointed tip, said flute upper end being larger than said flute lower end.