Patent Application
20130327188
This invention relates generally to tools and more particularly to slip-resistant screwdriver blades for slotted screws and methods for driving such screws.
Many well established types of screwdriver styles are on the market for securely positioning the driver's tip within the mating geometry in the screw head. Examples of such styles are Phillips, hex-head, and Torx®, to name only a few. The advantages of this positional stability cannot be overstated in assisting with the ease and efficiency of driving screws. Unfortunately slotted screws do not enjoy this stability and for many reasons remain quite popular, but historically continue in need of a viable solution to ending the frustrations that come with the difficulty of keeping the screw driver blade properly positioned and engaged with the slot. Previous attempts to mitigate this problem have all proven minimally effective in function and or burdened by excessive complexity and cost. For example, external guides are encumbered by fit limitations, complexity, and cost. Other more exotic methods to help reduce slippage by utilizing diamond or tungsten carbide coatings have offered minimal improvement and are anything but inexpensive to produce.
The advent and popularity of electrical means to drive screws has, before now, been of little to no help or benefit since the increase in inertia from rotational speed actually did exacerbate the usual difficulties associated with driving slotted screws.
The patent literature includes various examples of screwdrivers for slotted head screws, wherein the screwdriver includes features at its tip to prevent slippage of the tip in the screw head slot and, in some cases, the screw is non-conventional, i.e., includes features, e.g., keying features, which are specially designed to cooperate with the special feature(s) of the screwdriver blade. See for example, U.S. Pat. No. 1,899,489 Wickbergh); U.S. Pat. No. 4,339,971 (Zatorre); U.S. Pat. No. 5,259,279 (Strauch); U.S. Pat. No. 5,347,893 (Mikic et al.); U.S. Pat. No. 6,216,569 (Hu) and U.S. Pat. No. 6,378,406 (Totsu); and United States Published Applications: US2008/0022816 (Feldman); US 2009/0165604 (Macor); and 2010/0288086 (Huang).
Notwithstanding the above, a need exists for slotted head screwdriver which is effective to prevent slippage of the screwdriver's tip within a conventional slotted screw (i.e., a screw having a single transversely extending slot which is not undercut and which includes a planar bottom surface) that is simple in construction, low in cost and easy to use and does not mar the appearance of the screw. The subject invention addresses those needs.
In accordance with one aspect of this invention there is provided a driver blade for driving a conventional slotted screw. The slotted screw comprises a head having a single transversely extending slot with a planar bottom surface. The driver blade comprises an elongated body having a central longitudinal axis and a tip. The tip has a distal end in the form of a planar end face, which is arranged to engage the planar bottom surface of the screw slot. The tip also includes a sharply symmetrically tapered, e.g., a conical or pyramidal shaped, spike projecting outward from the planar end face along an axis parallel to the central longitudinal axis. The spike is arranged to dig into or penetrate the material of the screw at the planar bottom surface of the screw's slot while the screw is being driven to prevent slippage of the tip in the slot, whereupon after driving of the screw only a single small depression remains in the bottom of the screw's slot, thereby not marring the appearance of said slot.
In accordance with one exemplary embodiment of this invention the tip includes a single spike, which is located on the central longitudinal axis of the blade. In accordance with another exemplary embodiment of this invention the tip includes three spikes, one of which is located on the central longitudinal axis and the other two spikes equidistantly spaced from the spike on the central longitudinal axis. In the three-spike embodiment driving of the screw leaves only three small depressions in the bottom of the screw's slot, thereby not marring the appearance of the slot.
In accordance with still another exemplary embodiment of this invention the spike(s) can be formed of a material that is different and harder than the material making up the blade, depending upon the hardness of the head of the screw.
In accordance with another aspect of this invention, a method of driving a conventional slotted screw is provided. The slotted screw includes a head having a single transversely extending slot. The slot is not undercut and includes a bottom surface, which is planar. The method entails providing a screwdriver blade comprising an elongated body having a central longitudinal axis and a tip. The tip has a distal end in the form of a planar end face, which is arranged to engage the planar bottom surface of the screw slot. The tip also includes a sharply symmetrically tapered, e.g., a conical or pyramidal shaped, spike projecting outward from the planar end face along an axis parallel to the central longitudinal axis. To drive the screw the blade is inserted into the screw's slot and a force applied along the central longitudinal axis so that the spike engages and penetrates into the material of the screw at its bottom surface and the planar end face of the blade engages that bottom surface to drive the screw expeditiously to prevent slippage of the tip within the slot. Moreover, after driving of the screw only a single small depression remains in the bottom of the screw's slot, thereby not marring the appearance of the slot.
Referring now to the various figures of the drawing, wherein like reference characters refer to like parts, there is shown in
In the exemplary embodiment shown in
Before describing the tip and its non-slip spike feature of the blade of this invention a brief description of the type of conventional single slotted screws for which the blade of this invention has particular utility is in order. One such exemplary screw 12, i.e., a flat head wood screw, is shown in
Turning now to
It should be noted that the particular shape of the spike is not critical to the invention, so long as the spike is symmetrical and tapers to a sharp point. Thus, in lieu of a conical spike, such as shown in
The blades 20 shown in
As should be appreciated by those skilled in the art from the foregoing, by adding a small spike at the end of a driver blade the subject invention provides a heretofore unimagined simple, extremely effective, and very reliable resolution to the problem of driving slotted screws having a single slot with a planar bottom surface. In fact, it is believed that this invention provides a means for driving single slotted screws with equal ease and efficiency to that provided by specially designed screws and drivers like those of the prior art described above, particularly when driving screws electrically. However, the subject invention accomplishes that end without the need for screws having special features. Thus, by simply including as small symmetrically tapered sharp spike at the end of the drive blade to penetrate or embed in the material making up at the bottom of the screw slot even slightly, the screwdriver blade of this invention is prevented from sliding longitudinally along the slot, provided that a modicum of force is applied to drive the screw. All of this is accomplished without marring the appearance of the screw, e.g., only a single small depression is left in the screw when using the single spike embodiment or only three small depressions are left in the screw when using the three spike embodiment.
Moreover, the spike of this invention is such that it effectively secures the blade of the screwdriver to whatever material the screw is made of and does so without demanding any additional pressure than is typically applied to driving the screw. It will be recognized however that while advantage is gained with no additionally pressure, certain conditions may exist where still greater advantage and stability can be achieved with a greater pressure. In the case of harder materials, while penetration of the spike will generally be less with a given pressure, being naturally stronger they still achieve greater resistance to sliding even with the shallower interference. Softer, weaker materials on the other hand inversely will generally demand greater interference to prevent slippage but again due to naturally being easier to penetrate conveniently allow greater interference thus offsetting any reduction in stability caused by less strength of the material. Thus while the subject invention has an advantage in all materials, it will additionally offer further advantage in the case of more slippery materials such as plastic. It should also be noted the level of function is now so improved that awkward or difficult access situations are likely easier to manage even where the typically desired pressure isn't possible.
While it is of course preferred to keep the screwdriver blade somewhat centrally located longitudinally within the screw slot, the detrimental affect even with less than optimal centering is minimal since the position of the blade is so stable. This is true as well when driving the screws electrically, where previously a small misalignment would have most often lead to further degradation in position and the ability to drive the screw. Thus, this invention further saves time and improves ease of use by sparing the user from the demand for precision alignment.
Whether a single or multiple spikes are used, they should be relatively short in order to ensure that a high percentage of the driver's blade geometry may still engage the sides of the screw slot. Here a single centrally located spike or point will have an advantage over multiple spikes in allowing the opposing sides of the driver blade to easily rotate about the axis of the spike to bear against their respective sides of the screw's slot. Preferably the spike or spikes are extremely sharp to aid in penetration of the screw material and configured with a taper angle that balances ease of penetration with minimal force and yet still provides sufficient strength to reliably and repeatedly engage harder materials rendering the tool both effective and long lasting. The forming of the spikes should be done in a way that is most efficient or desirable from a manufacturing standpoint.
Since the subject invention makes use of the spike(s) penetrating somewhat into the material making up the screw, the spike(s) may be formed of a different and harder material than the material making up the blade itself to ensure that the spike will penetrate into the bottom of the screw's slot with the application of a normal applied force. Thus, for example if the screw to be driven is particularly hard, the spike(s) may be formed of a very hard material, such as tungsten carbide, titanium, and the like. In such a case the spike(s) or the entire blade can be formed of such very hard material.
In summary, the screw driver blade of this invention provides an improved means for driving slotted head screws by securing the position of blade's tip within the screw's slot, thus mitigating the common and annoying difficulty of keeping the blade properly positioned therein and from slipping out. This improved function is achieved by adding at least one single small spike or point at the end of the screwdriver blade to dig-in or embed into the material making up at the bottom of the screw slot, thereby preventing slippage. Moreover, the use of the spike or point to dig-in or embed into the material of the slot requires no more pressure than is typically applied to drive the screw. Thus, this invention provides a simple, highly functional, cost effective means to easily drive slotted screws heretofore unimagined for this type of screw both manually and electrically and does so without marring the screw.
Without further elaboration the foregoing will so fully illustrate my invention that others may, by applying current or future knowledge, adopt the same for use under various conditions of service.
