JPS6347926B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to sheet metal screws, and more specifically,
This invention relates to screws for attaching two thin panels together. This screw exhibits better stripping torque than other known sheet metal screws. The strip torque here refers to the value of the holding force of a screw, and refers to the torque that, if more torque is applied to the screw, will cause the screw to lose its holding force, possibly damaging the panel or the like.

With currently available sheet metal screws, the difference between drive torque and strip torque is very small. Since there are dimensional differences and variations in materials, it is virtually impossible to screw in a screw that is difficult to screw in with a single torque set by a power screwdriver without causing the least amount of wear on the threads. This means that a relatively large number of the threads on the screw are worn down, resulting in a reduction in the tightening load, and an increase in the effort required to remove a screw that has been screwed in and then screw in another screw.

The screw of the present invention aims to reduce the above-mentioned problems by increasing the difference between drive torque and strip torque. The sheet metal screw of the invention may be provided with a recess on the underside of the head surrounding the upper area of the shank, and at a certain distance inside this recess the shank may be formed with a helical ramp, In this case, the ramp may be an extension of the thread in the shank. This ramp can be easily formed during the head forming process. The ramp is preferably toothed so that depending on the orientation of the teeth, the stripping torque can be increased or the withdrawal resistance (force resisting rotation in the opposite direction) can be increased.

The present invention will be explained below with reference to the drawings.

10 indicates a rotary fastener or sheet metal screw of the present invention. The head 12 has a collar 14 projecting laterally from a generally cylindrical shank 15. Head 1
A concave portion 18 recessed upward is formed in the lower surface 16 of 2. On the upper side of the head 12 is a driving force introduction surface 1.
There are 9. A ramp 20 extends upward from outside (below) the recess 18 into the recess. A thread 22, shown in broken lines in FIG. 1, extends circumferentially from around the shank 15, with the helical ramp 20 forming an extension thereof. The thread 22 is partially formed from the lowest end of the ramp because the ramp exceeds the diameter of the shank material and additional material is provided to prevent thread formation in this area. This is because it makes sure that it is perfect. With conventional sheet metal screws, this top thread tends to be only partially formed because the thread rolling die cannot reach into the recess and therefore can only collect material from one side of the top thread. It was hot.

The helical ramp 20 is preferably formed during head formation and can be provided in any desired shape. For example, the ramp 20 may be serrated with teeth 24 oriented either in the same direction as the direction of rotation of the screw (FIG. 4) or in the direction opposite to the direction of rotation (FIG. 5). Then tooth 24
increases the stripping torque or withdrawal drag, respectively. The helical ramps may be provided as two 20, 30 as shown in FIG. 6, with the teeth 24 of the ramp 30 oriented in the opposite direction from the teeth of the ramp 20 to increase both the stripping torque and the withdrawal drag. .

In use, screws 10 are threaded through the upper support panel 26 and into the lower tapping panel 28, as seen in FIG. The hole drilled in the support panel 26 for passing the screw may be a clearance hole 31 larger than the threaded thread 22. Once the screw 10 is fully screwed in, further turning would conventionally cause the material to wear out, but in the present invention this does not occur, and the edge 32 of the hole in the tapping panel 28 now engages the helical ramp 20. As it slides up the ramp 20, the diameter of the ramp and therefore the magnitude of the strip torque increases. As shown in FIG. 4, the ramp 20 may be dimensioned to engage the inner edge of the clearance hole 31 and, in the case of a toothed ramp, to sink into the inner edge of the clearance hole 31. This increases the evaluation of strip torque.

For example, the helical ramp preferably has a length equal to 1 1/4 times the thread pitch. 1
0.375 of the pitch is preferably within the area of the recess 18, and the remaining 0.875 pitch is outside the recess and forms the connection with the thread 22. The minimum height of the helical ramp 20 is the diameter of the material close to the root diameter of the thread, and the maximum height is at least the height of the thread ridge measured from the root diameter of the thread (the difference between the crest diameter and the root diameter of the thread). Preferably, it is approximately twice the height of the threads, thus forming a spiral.

The screw of this invention has been shown to have a much higher stripping torque value than conventional sheet metal screws or screws that have a recess on the underside of the head but no ramp and only have an unthreaded cylindrical portion. Numerous tests have shown. A screw with a recess on the underside of the head but without a ramp will not produce a greater strip torque value than a conventional sheet metal screw. Of course, this is because the purpose of the recessed screw is not to increase the stripping torque, but rather to intentionally crush the thread within the tut pin panel to prevent it from being pulled out. However, this effect is only achieved when the thickness of the panels is predetermined; if the thickness of the two panels is not predetermined, the pull-out prevention effect is not achieved, and the tightening load is also significantly reduced. In contrast, the screw of the present invention can be used effectively for panels of various thicknesses.

In the embodiment described above, the helical ramp had a spiral shape whose diameter increases constantly from its beginning to its end. Thus, the end of the ramp contacts the clearance hole in the support panel, essentially a point contact.

FIG. 7 shows still another embodiment of the present invention,
Here, the ramp is formed in a certain circular arc area, followed by a continuation of constant radius, which makes surface contact with the clearance hole. In other words, this screw 1
The ramp 20a at 0a (teeth omitted for ease of illustration) extends from a starting end 34 at 0° to a terminal end 32 at approximately 270°, reaching its maximum radial dimension at point 32, and remaining 90° forms the maximum radius continuation 36 of the ramp, and since the diameter of this continuation is constant, it contacts the clearance hole at approximately 90°. This means that
It is quite effective in applying a stall torque to the screw, in resisting pullout, and in preventing relative lateral movement of the two plates from the screw.

Another embodiment of the invention is shown in FIG. In this case the rising part of the ramp 20b extends from 0° to 180°, i.e. from 34b to 32b, so that the continuous section 36b is 180° and has a greater area of contact with the edge of the clearance hole than that of FIG. big.

The embodiment of the invention shown and described herein is particularly advantageous for securing together pieces of sheet metal.
However, it is sometimes desirable to bond adjacent sheets of sheet metal and heavier gauge sheet plastic to each other. A screw particularly suitable for this purpose is shown in FIGS. 9-12. The main difference between this embodiment and the previous ones is that the lower surface 16 of the head
c is flat except for the shank 15c and the ramp 20c. This screw is the sheet metal support plate 26
The second plastic plate, that is, the tapping plate 28, passes through the clearance hole 31c of c.
c, a considerable amount of plastic is forced into or out of the clearance hole 31c by the ramp 20c and impinges on the flat underside 16c of the head. If the head had a recess as shown in Figures 1 and 3, the plastic part would protrude too much and would likely tear off and fall off the plastic plate, but this example prevents this from happening. Since there is no screwdriver, the stalling torque that holds the screw in place is even better when screwed in deeply with an air screwdriver.

As shown in FIG. 12, when screwing in with the plastic plate 26d on top and the sheet metal plate 28d on the bottom, the clearance hole 31d is larger than the thread diameter, and the plastic material is easily compressed by the ramp 20c. . However, some of the metal surrounding the tapping hole in the sheet metal tapping plate 28d is deflected upwardly as shown at 32c at the thread 22c, and a portion thereof engages the ramp 20c, causing the screw and the pneumatic screwdriver to It will help you put on the .

The actual test result under the condition shown in Fig. 12 shows that the stalling torque is about 6 times the driving torque, and the sheet metal screw and screwdriver can be easily stopped. Conventional AB without road
This is approximately twice the stall torque of a screw.

Although the present invention has been described above using specific embodiments, it can be implemented with various designs other than the illustrated embodiments. For example, although the shank of the screw of the present invention has been described as being cylindrical, the concept of cylindrical shape also includes cases where the cross-sectional shape of the shank is lobe-shaped. Furthermore, although this screw has been described as a winding screw, the concept of the invention may also be used for drill screws with specific thread configurations, or for attaching plastic panels to sheet metal or secondary plastic panels. It will be understood that it can also be used.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional side view of the head area of a blank sheet metal screw according to the present invention, and FIG.
- A cross-sectional view taken along line 2; Figure 3 is a partial cross-sectional view showing two sheet metal panels being fastened together using the same screws as above;
FIGS. 4 to 8 are cross-sectional views illustrating ramps that can be provided on the screw according to the present invention, and FIG. 9 is a partial portion similar to FIG. 1 of another embodiment of the present invention. Cross-sectional side view, Figure 10 is approximately 10 of Figure 9.
-10 line, Figure 11 is a cross-sectional view with the metal panel on top and the plastic panel on the bottom, tightened with the screws shown in Figure 9. Figure 12 is a cross-sectional view with the plastic panel on top and the metal panel on the bottom. This is a sectional view of the screw shown in FIG. 9 in a state where the screws are tightened.
10b, 10c are sheet metal screws, 12, 12c are heads, 16, 16c are the bottom surfaces of the heads, 15, 15c
is a shank, 20, 20a, 20b, 20c are spiral ramps, 22, 22c are threads, 26 and 2
8, 26c and 28c are the panels to be tightened, 3
1, 31a, 31b, 31c, and 31d indicate clearance holes.

Claims (1)

[Scope of Claims] 1. A sheet metal screw used to attach a first panel having a clearance hole to a second panel, the screw having a generally cylindrical shank and an enlarged head having a driving force introduction surface. at one end of the shank, the head having a lower surface, the cylindrical shank having at least one helical thread, the thread having a predetermined height from the root diameter of the thread to the thread diameter. projecting outwardly, a helical ramp begins at substantially one end point of said helical thread to form a continuation of the helical thread, said ramp extending along the shank to the underside of the head and extending from said helical ramp sheet metal screw deflecting outwardly some of the material of at least one of a plurality of panels to significantly increase the stripping torque of the screw relative to the panel. 2. The helical ramp has an initial height that is substantially the same as the initial height of the root diameter of the thread, and the height increases to a maximum height that is at least equal to the thread diameter. The sheet metal screw described in item 1. 3 The maximum height of the spiral ramp is 2 times the thread diameter.
The sheet metal screw according to claim 2, which is substantially equal to twice. 4. The sheet metal screw according to claim 1, wherein the spiral ramp has a large number of serrations. 5. A sheet metal screw according to claim 4, wherein the serrations consist of a plurality of teeth oriented generally in the same direction as the direction of rotation of the screw, said teeth further increasing the stripping torque. 6. A sheet metal screw according to claim 4, wherein the serrations consist of a plurality of teeth oriented generally in a direction opposite to the direction of rotation of the screw, said teeth increasing the retraction force. 7. A sheet metal screw according to claim 1, wherein the ramp comprises two ramps, a first and a second ramp starting at substantially opposite points. 8. The sheet metal screw according to claim 1, wherein the thread diameter of the predetermined thread is insufficient to contact the edge of the clearance hole in the first panel. 9. The sheet metal screw of claim 1, wherein the helical ramp has a height sufficient to engage the edge of the clearance hole in the first panel. 10. The sheet metal screw of claim 1, wherein the lower surface of the head has a recess, and the helical ramp deflects material of the second panel upwardly through the clearance hole and into the recess. 11. The sheet metal screw of claim 1, wherein the lower surface of the head is substantially flat and the helical ramp deflects material of at least one of the panels laterally away from the shank. 12. The sheet metal screw according to claim 1, wherein the ramp has a continuous arc of 360 degrees or less with a substantially constant radius. 13 The ramp having a continuous portion with a constant radius,
13. A sheet metal screw according to claim 12, which extends approximately 360 degrees. 14. The sheet metal screw according to claim 13, wherein the inclined portion of the ramp is approximately 270 degrees, and the continuous portion of the constant radius is approximately 90 degrees. 15. The sheet metal screw according to claim 13, wherein the slope of the ramp is approximately 180 degrees, and the continuous portion of the constant radius is approximately 180 degrees.