US635297A - Screw. - Google Patents

Description

No. 635,297. Patented Oct., 2.4, |899. J. W. CALDWELL.

SCREW.

(Appumon ned Lug. 1s, 189s.)

(No Model.)

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UNTTED STATES PATENT JOHN WILLIAM CALDWELL, OF OOOLAMON, SOUTH WALES.

SCREW.

SPECIFICATION forming part of Letters Patent No. 635,297, dated October 24, 1899. Application filed August I3,1898 Serial No.688,485. (No model.)

To @ZZ whom, it may concern,.-

Be it known that I, JOHN WILLIAM CALD- WELL, a subject of the Queen of Great Britain, and a resident of Coolamon, New South Wales, and temporarily residing in the borough of Manhattan, in the city, county, and State of New York, have invented certain new and useful Improvements in Screws, of which the following is a specification.

This invention relates to the constructionl of threaded devices-such, for instance, as screws-and especially to that class of screws adapted for use in wood.

The object of the invention is to provide a threaded device or screw which not only has superior holding power to threaded devices or screws as ordinarily constructed, but is otherwise more efficient than such screws owing to the increased rate of speed and facility with which the same may be forced into or taken out of the wood, and this with less eX- ertion and without the choking or clogging of the threads thereof, as is the case with ordinary screw-threads, and is also more efficient than such screws, since it may be readily started in ordinary wood without the necessity, as heretofore, of tirstboring a hole therefor, thereby affecting the holding power of the wood, and may also be readily driven into place, thereby avoiding the slow and tedious operation of inserting it by means of a screwdriver.

In the drawings accompanying and forming part of this specification, Figure l is a view of one form of device, such as a wood-screw, having this improved construction of thread. Fig. 2 is a view of another form of such screw. Fig. 3 is a view, partly in vertical section, of a screw as ordinarily constructed. Fig. 4 is a vertical sectional view of the screw shown in Fig. l. Fig. 5 is a vertical sectional view of the screw shown in Fig. 3. Fig. 6 is an enlarged view of the threaded portion ofthis improved screw for illustrating the action of the wood iibers. Fig. 7 is a similar enlarged View of the threaded portion of a screw as ordinarily constructed. Figs. 8, 9, 10, and 11 illustrate some of the different forms of devices which may be provided with this improved construction of threads, and Fig. 12 is an end view of the thread.

Similar characters of reference designate like parts in all the figures of the drawings.

As a preface to a further description of this improved threaded device it is to be understood that while the same is shown and described herein as a screw the invention is, nevertheless, applicable to any. kind of device having threads, some forms of which are shown in Figs. 8 to ll of the drawings, and therefore it will be understood that by the term screw as used herein is to be understood any device having threads.

In the use of threaded devices-such, for instance, as wood-screws as ordinarily constrncted-it is found in practice that they not only require considerable exertion in order to force them into the wood, but that it takes a comparatively long time to accomplish this result owing to the necessity of first boring a hole and to theirslow speed, which latter is due, I apprehend, to the shape and construction of the threads and points of the screw, which afford great resistance to the penetration of such screw. In the screw as usually constructed since the under beveled sides 2, Figs. 3, 5,' and 7, of the threads project or extend below the peripheral edges 3 thereof they first engage the wood, and hence form resistantsurfaces, necessitating that the wood be forced out of the way, as at 4, Fig. 7, to permit the entrance of the screw. Moreover, owing tothe inclination of these beveled under sides 2 the wood is forced downwardly and outwardly and in a direction coinciding with the direction the screw is working, thereby tending constantly to impede the effective action of the screw by pressing the same outward and by choking and clogging the threads thereof. In other words, owing to the construction of the thread in order to force the screw into position the wood must be displaced by a jamming or wedging action, and as the tendency of the wood fibers is to return to their normal position the threads are constantly being pressed outward and are choked and clogged up, whereby the free action of the screw is retarded. In addition to this the screw as usually constructed is provided with a relatively flat or blunt conical or beveled point 5, which is ineffective to cut its way into the wood, so that to drive the IOO screw into position considerable force is required, since the wood must be forced out of the way by a wedging action in order to permit the penetration of the screw, during which the wood continues to impede the effective action of the screw by its resistant pressure after the screw is entered. Furthermore, the edge of the thread being located above the under surface thereof it has a tendency to strip the wood between the threads, so that its drawing and holding power is eliminated, and it therefore becomes necessary to bore a hole substantially all the way in hard wood and some distance in ordinary wood.

In the present improvement in order to avoid the defects above set forth I have provided a device in which the point and threads are so constructed that they will act as a cutting mediuln to permit the screw to cut its way into the wood without the necessity of forcing the fibers of such wood out of the way by a wedging or jamming action, and which threads will also operate to clear themselves of the fibers of the wood, thereby to avoid the resistant pressure thereof, and will assist in pulling the screw into position. In a general way this improved threaded device embodies a thread the peripheral edge of which is so located relatively to the under side of such thread that it will first engage the wood, whereby when such edge is formed sharp the thread may act with a cutting action on the wood, thereby to permit the device to cut its way thereinto, the upper side of such thread being so formed that it will act to clear the threads of the fibers of the wood and so permit the free action of the device. This improved device, furthermore, comprises a piurality of cutting points or lips, whereby the effective action of the device is increased. In practice the screw may have its core S conical throughout, Fig. 2, or it may have such core of the same or substantially the same diameter throughout, terminating in a short beveled or sharp cone-shaped end 9, as desired, Fig. l.

In the construction shown the screw-core is provided with a plurality of spiral threads shown as two in number, lO and l2, thereby forming a double-threaded screw, the threads being preferably of a wide or open pitch, although it will be understood that any desired pitch may be used. Each of these threads I0 and 12 is so formed that its outer or peripheral edge 13 will first engage and upwardly displace the wood, thereby to decrease the resistance to the entrance of the thread, this being accomplished by so forming the under side lei of the threads that they'do not project beyond or below the plane of such edge and which in practice may be secured by forming the under side of such threads relatively flat, whereby they may be in substantially the same plane as the peripheral edge of the threads. The peripheral edge 13 of the thread, which in practice first engages the wood, may be formed as a sharp cutting edge,

whereby it will cut its way into the wood, thel under side of the thread owing,r to its formation not impeding the action of the device, so that the screw can be forced into the work with superior facility and with comparatively little exertion. Since the peripheral or cutting edge of the screw first engages the wood or material, as hereinbefore set forth, it follows that the under surface of the thread while in the same relative plane with the' edge and while relatively fiat, as above set forth, nevertheless must in practice be slightly above the cutting edge of the screw, or otherwise the screw on entering the material would have the entire under surface of its thread in engagement with the material simultaneously with the engagement therewith of the edge, so that in practice the under side ofthe screw may be somewhat dipped to insure the prior engagement of the cutting edge with the wood, this also being the case in practice with the threads located on the beveled end of the screw of the form shown in Fig. l, since as the surfaces ot' the threads are relatively flat and as the threads will usually have in practice the same formation throughout the screw the under surfaces will therefore be substantially at right angles to the surface of the core on which the threads are carried, and as the threads on the beveled end of the screw are carried on a beveled surface and are substantially at right angles to such beveled surface they may have in practice their under surfaces so inclined or dipped as to positively insure the prior engagement of their cutting edges with the wood, and this throughout the length of the beveled surface of the core. The upper sides orsurfaces 15 of the threads are formed relatively steep, thereby forming with the relatively fiat under sides a relatively sharp cutting edge, and owing to these relatively steep upper sides of thev threads the tendency of such threads is to spring or lift the fibers of the wood upwardly and in a direction opposite to the direction in which the screw is working and so clear the threads and prevent the clogging thereof, whereby it follows that the screw may be forced into the work with greater facility and less exertion than would otherwise be the case, the tendency of the wood fibers to return to their normal position assisting in forcing the screw into position and to hold the same firmer.

To increase the working effect of the screw, I provide the same with a cutting lip or point, which may project beyond or below the apex of the core. In practice a plurality of these cutting-lips are provided and may correspond in number with the number of threads carried by the core 8. In the present instance a pair of such cutting lips or points are shown, each spiral thread l0 and 12 terminating in a cutting lip or point l0 and 12, respectively, adjacent to the apex of the screw. The outer ends of these spiral thrcads'lO and l2 are shown as coming together near of" just beyond IIO the apex of the core 8 and forming tw'o radial sharp cutting edges or points, somewhat in the nature of wings, disposed in opposition and in angular relation to the axis of the core and adapted to effectively and quickly cut their way into the wood, whereby the screw will enter the work with increased facility and with less exertion than would otherwise be the case. These cutting edges are in the nature of chisel cutting-points, with the cutting edges lower than the heel, and readily lift the wood upwardly and outwardly and quickly form a hole to admit the core of the screw. It will be understood thatin the formation of a single-threaded screw only one of these cutting edges or points may be provided. In practice it may be provided with a relatively sharp pitch, which is practicable in this construction of screw, whereby its speed may be increased. It is preferable in the formation of this device that the threads around the core should be of an open or wide pitch, though not necessarily the pitch shown in the drawings, so that the threads as they draw the device into the wood will bite the wood firmly without splitting and at the same time draw the device into the wood at an in'- creased rate of speed.

By constructing the screw in the manner set forth it has been found in practice that the screw will enter nearly all wood without boring, and in exceptionally hard wood by boring only a slight distance, so that the wood is left in position to hold the screw firmer than otherwise, whereas in the use of the ordinary screw it is necessary irst to bore a relatively deep hole, which displaces and removes the wood, so that when the screw is forced into position such wood will not hold the screw with the same efficiency. Hence its drawing and holding power is to a great extent destroyed. Moreover, by forming a screw with a pair or a plurality of cutting edges or points the device will cut across or through cracks, holes, knots, dac., without altering or changing its course.

It will be seen that since in this improved screw the threads are beveled at their upper sides in a somewhat similar mannervto that in which the ordinary threads are beveled at their under sides it follows that the action of the wood on this improved .device when a drawing or outward force is exerted thereon will be in a direction opposite to that in which it is worked-that is to say, the upper inclined or beveled surface of the screw-threads acts to jam or wedge the wood when an outward or drawing force is exerted on the screw in a similar manner to that in which the wood is jammed or wedged by the under faces of the ordinary screw when rotated into position, so that the holding power of this screw -is superior to the ordinary screw.

This improved screw is of course especially intended for use in wood and is applicable for use in woods of various kinds and degrees of hardness, and is in one form thereof especially adapted for being driven in place by i means of a hammer, thereby avoiding the slow and tedious operation of inserting the screw by means of the screw-driver. In driv ing a screw of this improved construction in this manner into the wood the extended spiral relatively flat under surface 14 of the thread forms a resistance-surface, against which the force of the blow is expended, and this force being distributed over such a relatively extensive area tends to prevent the driving of the screw downwardly, in view of the angle of the thread, with sufficient energy to sever the iibers of the wood immediately under said resistance-surface and in the line of the edge of the thread, while at the same time this action of the under surface in connection with the relatively steep pitch of the thread tends to rotate the screw during the driving action with greater speed than it otherwise might be rotated, and so furnishes the power for operating the cutting- points 10 and 12/ at the Aapex of the screw, whereby these points are made to coperate for boring a hole into which the threaded portion of the screw is forced. It will therefore be observed that the peculiar cooperation between a screw-thread having the particular construction described and the two cuttingpoints is such that this improved thread furnishes an effective means for operating said cutting-points forcutting away the wood to form the small bore, into which the somewhat larger core of the screw will be forced bythe blows to which the screw is subjected while it is being driven into place.

- In the operation of inserting the screw the fibers of the wood as these are separated by the relatively sharp thread lie, some of them, (those immediately under the thread, as (1,) relatively straight or perpendicmlar to the axis of the screw. Those fibers, as l), however, which naturally come just above the edge of the screw-thread are not cut otf or destroyed, as ordinarily happens with the old kinds of screws, but are turned upwardly, so that the fibers which pass just over the extreme edge are bent at said edge and lie inclined upwardly along the steep surface'of the thread, as at c. In other words, the lower fibers of the inclined mass of fibers push npwardly the other fibers immediately above them and also push the fibers outwardly, so as to form a compact mass adjacent to the inclined upper surface l5 of the screw-thread, thereby constituting a bracing member between said inclined surface and that region of the wood which lies just outside of the screw. Furthermore, this bracing action and the inclination of the upper surface of the thread coperate to prevent the retraction of the screw by the pressure applied thereto in an outward direction, since this inclination of the upper surfaces of the screw-thread, which form to a certain extent a double wedge, owing to its steep inclination both downward and sidewise, operates toward IOO IIO

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counteracting the effect which would otherwise be produced by the relatively steep pitch of the screw-thread, which would naturally tend to reduce the security of the fastening.

Owing to the features of construction which I have hereinbefore more fully pointed out the ber of the wood into which the screw isA driven is properly separated to form the space for the screw-thread, and this with a mini'- mum of destructive action on such fiber, thereby securing a superior holding power of the screw in the wood, while not retarding the introduction of the screw by driving instead of by the use of a screw-driver to turn the screw into place.

In the use of a screw constructed in the manner set forth it has been found by actual test that it will penetrate ordinary wood one inch thick in about sixteen (16) turns, while an ordinary screw for the same kind and thickness of wood requires from thirty-eight (38) to forty-two (42) turns underequal power.

I claim as my inventionl. A screw comprised of a core provided with one or more threads each having a sharp cutting edge located relatively to the under side of such thread to first engage and upwardly displace the material, thereby to decrease the resistance to the entrance of such thread.

2. A screw comprised of a core provided with one or more threads each having a sharp cutting edge located relatively to the under side of such thread to iirst engage and upwardly displace the material and thereby decrease the resistance to the entrance of the thread, and each thread terminating in a cutting-lip projecting beyond and at an angle to the axis of the core.

3. Adevice of the class specified comprised of a core provided with a plurality of threads disposed thereon, each thread having a beveled upper face, a relatively fiat under face, and a sharp c utting edge located relatively to the under side of such thread to first engage and upwardly displace the material and thereby decrease the resistance to the entrance of the thread, and each of said threads terminating in a cutting edge or lip projecting beyond and at an angle to the axis of said core;

4. A screw comprised of a core provided with one or more threads located thereon and extending beyond the entering end of said core, each forming a radial cutting lip or wing so disposed that its pitch-angle is less than the angle between the under surface of the thread and the core.

5. A screw comprised of a core cone-shaped from end to end and provided with one or more threads each having a sharp cutting edge located relatively to the under side of such thread to rst engage and upwardly displace the material and thereby decrease the resistance to the entrance of such thread, each of said threads terminating in a cutting lip or wing projecting beyond and at an angle to the axis of said core.

G. A screw having a core, cone-shaped from end to end, and a pair of spiral threads disposed thereon, each of said threads having a relatively flat under face and a beveled upper face and terminating in a cutting edge or point adjacent to the end of said core.

7. The herein-described device comprised of a core provided with a cone-shaped or beveled end and with a plurality of threads thereon, each of the threads of such cone-shaped end having a sharp cutting edge located relatively to the under side of such thread to first engage and upwardly displace the material and thereby decrease the resistance to the entrance of the thread, and each of said threads terminating in a radial cutting lip or wing projecting beyond said core.

S. A device having a core provided with a cone-shaped end and two wide or open pitch spiral threads of the same depth throughout and extending beyond the apex of the core and forming two radial cutting wings or points, each of said threads having a relatively fiat under face and a relatively-inclined

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