Tools – Wrench – screwdriver – or driver therefor – Having work engaging and force exerting portion inserted...
Reexamination Certificate
2002-06-20
2004-09-21
Wilson, Lee D. (Department: 3723)
Tools
Wrench, screwdriver, or driver therefor
Having work engaging and force exerting portion inserted...
C081S440000
Reexamination Certificate
active
06792838
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to fasteners in particular screws and bolts having a head provided with a recess to receive a driving tool for turning the screw or bolt.
GB-A-1150382 appears to be the first disclosure of a screw provided with a multi-tiered recess and a corresponding multi-tiered driver. GB-A-2285940 discloses essentially the same idea. Both these publications describe the advantages provided by the arrangements disclosed. The first is that the recesses are essentially parallel-sided and consequently eliminate cam-out problems that are associated with cross-head recesses. Secondly, they give the possibility of a single driving tool being suitable for driving a wide range of screw sizes.
The single driving tool typically has three (for example) tiers of driving surfaces which are employed to drive large screws having three tiers of recess. However, the same tool can be employed with smaller screws having only two tiers of recess, the largest tier being omitted. Indeed, even smaller screws may have only one, the smallest tier, in their recess and be driven by the smallest tier only of the tool.
GB-A-2329947 discloses a similar arrangement, and WO-A-0177538 discloses tiers that have such a small extent in the recesses of screws and bolts that, at the torques at which the screws are intended to be operated, they cannot be turned unless at least two tiers are both engaged by the tool. Otherwise, the screw is arranged to round out of engagement with the driving tool. This provides a security feature in that only the appropriate tool will undo the screw.
However, until co-pending application GB0124122.3 was filed by the present applicant on 8 Oct. 2001, these ideas were not a practical reality, because the recesses could not competitively be formed in screws and bolts.
Now, interest is developing in such fastening systems. However, the system so far has primarily been applied only to the smaller wood and machine screws, that is to say, No.6- to No.10-size wood screws (ie about 2 mm to 5 mm diameter—lengths about 15 mm to 100 mm) and M2 to M10 machine screws (ie 2 mm diameter threads to 10 mm). However, there is a need, particularly in the machine screw and bolt field, for larger sizes.
In principle, there is no limit to the number of tiers that can be included or added to a recess or driver. But there comes a point when the driver, if it is big enough and strong enough to drive the largest screws and bolts, it will be far too awkward, bulky and heavy to sensitively drive the smaller screws. Moreover, in larger screws, the torque transmission capability of the smaller tiers becomes insignificant.
Consequently it is desirable to divide the system between ranges of sizes of screw/bolt, but, in so doing, some of the benefit of the system is lost, because at least two tools then become necessary to cover the entire range of sizes.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a system that mitigates this loss of universality.
In accordance with the present invention there is provided a fastener system comprising a plurality of ranges of size of threaded fastener, each fastener having a head provided with a recess to receive a tool to rotatingly drive the fastener, and wherein:
in each range of sizes, the largest size of fastener has a recess comprising a plurality of driving tiers of reducing size superimposed on one another, each tier having sides which are substantially parallel a long axis of the fastener and define a polygon in section;
between two adjacent size ranges, there is a common tier, being the largest tier of the recess of the smaller size range and the smallest tier of the recess of the larger size range, which common tier is the same section in each range; and
the depth from the base of the largest recess to the base of the smallest recess in the smaller size range is less than the depth of the smallest recess in the larger size range.
Preferably, there are two size ranges of fasteners comprising screws of diameters from about 2 mm to about 10 mm and from about 10 mm to about 30 mm. The screws may be size M2 machine screws to size M10 in the small range and size M12 to M30 in the large size range.
The common tier is preferably hexagonal in section, but it equally could be pentagonal or some other straight-sided polygon.
The common tier preferably has a diameter of about 6 mm, preferably 5.9 mm.
The smaller size range of fasteners may have three tiers in larger fasteners, two tiers in middle size fasteners, and one in the smallest fasteners. The larger size range may have four tiers in the larger fasteners, and three tiers in smaller fasteners. Of course, smaller fasteners in the larger size range are going to be bigger than larger size fasteners in the smaller size range, unless it is desired that there might be screws of the same dimension, some having recesses in common with the larger size range of fasteners, and some having recesses in common with the smaller size range of fasteners
By this simple expedient, then, of a common tier between the two size ranges, a driver adapted for the smaller size range can be employed to drive the larger size of fasteners, and vice versa. This is a very useful feature because it is frequently the case that either of the following events occurs:
a) A user spends some time aligning objects to be joined by a fastener and, when aligned, holds them in place while a fastener is inserted. Then, he/she reaches for the tool to drive the fastener, only to find that the wrong driving bit is fitted in the tool! As a result, often the entire workpiece has to be dismantled while the user fits the right bit to the tool (or finds the right tool) before starting again.
b) One of the benefits of the fastening system to which the present invention relates is that, because the recess is parallel-sided, there is no cam-out. Consequently, it is possible to fit a fastener onto the end of the tool without the fastener immediately falling off. This is useful because, often, access to the location where the fastener is to be applied is restricted or confined. Being able to manoeuvre a fastener into position with the aid of the driving tool frequently facilitates this task.
With the present invention both situations can be accommodated conveniently. In the first case, either a small driver can initiate the connection of the fastener (from the larger size range), or, indeed, a large driver can initiate connection of a fastener from the smaller size range, (as long as that fastener has the largest size recess provided for that range). Clearly, with the wrong driver it is not advisable to attempt final tightening, but that is not the issue. Once the fastener has been sufficiently engaged, the right driver can be found and applied for final tightening of the fastener.
As for event b) above, employing the driver to position fasteners in a workpiece does, indeed, frequently facilitate connection. However, the problem is not assisted as much as it might be when the proper driver is used. With larger sizes, the driver is often no slimmer than a user's own fingers, for example. However, by using the driver appropriate for a smaller range of fasteners to locate and begin driving of a fastener from the larger range, easier and quicker engagement of the workpiece is likely.
In the machine screw field, it is found that a single driver is capable of driving all screws in the range M2 to M10. M2 screws typically require no more than about 0.3 Nm of torque to be applied, and a single 2.5 mm diameter, 1.5 mm depth, driving tier is found adequate. M10 screws typically require about 70 Nm, and three tiers, or at least two larger tiers, are necessary to transmit this torque. The largest tier typically might have the dimensions mentioned above for the smallest tier; 4 mm diameter, 1 mm depth for a middle tier; and 6 mm diameter, 1.5 mm depth for the largest tier.
However, for bolts in the range M12 to M30, a driver tool of 6 mm diameter is not adequate to transmit the torques expected,
Brooks Lawrence Antony
Sidwell Steven
Uni-Screw Worldwide, Inc.
Wilson Lee D.
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