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Patent Searching and Data

Document Type and Number:
WIPO Patent Application WO/1990/007653
Kind Code:
There is provided a flanged drive-head lock washer (24) for use in combination with a wedge-action-type fastener, wherein the fastener includes a bolt or screw member (17) having a cam nut (16) or cam head. The flanged drive-head washer is formed having a nut-like body and a plurality of wrench-engaging sides (30) to match the sides of the particular nut (16) or head (14) of a bolt. The upper face of the washer comprises a plurality of cam members (34) arranged to lockingly engage the corresponding cam surface formed on the contacting surface of the cam nut (16) or cam head. The lower surface of the washer is formed having a frictional surface (44) defined by an enlarged annular flange (28). The matching cam surfaces are arranged to align the corresponding wrench-engaging side walls, whereby the cam nut or cam head can be simultaneously rotated during removal of the fastener without affecting the integrity of the fastener.

Application Number:
Publication Date:
July 12, 1990
Filing Date:
December 27, 1988
Export Citation:
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International Classes:
F16B39/24; F16B39/282; F16B23/00; F16B43/00; (IPC1-7): F16B39/24
Foreign References:
Other References:
See also references of EP 0451140A1
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1. A wedgeaction lock washer in combina¬ tion with a threaded fastener, comprising: a fastener means having a threaded stud member, a fastener head ormed at one end thereof, and a nut adapted to be threaded to said stud member, said fastener head (member) and said nut being formed having a plurality of wrench engageable vertical side surfaces, wherein one surface of said head or said nut includes a plurality of contiguous cam members : a onepiece wedgeaction lock washer having a first body portion and an integrally formed second body portion, each of said body portions having a center bore disposed therethrough; said first body portion being formed to define a drive head having a plurality of contiguous cam members adapted to engage said cam members of said fastener head or nut in a locking arrangement under force, and a plurality of wrench engageable vertical side surfaces being formed to match and be aligned with said vertical side surfaces of said fastener head or nut thereof; and said second body portion being defined by an enlarged radially extending flange member, said flange member having a frictional engaging surface adapted to engage the surface of a workpiece to which is secured said threaded fastener.
2. The combination as recited in claim 1, wherein said flange member includes a frictionalen gagingring member defined by a central recess formed in the undersurface of said second body portion.
3. The combination as recited in claim 2, wherein said cam members of said fastener head, or said nut and said cam members of said drive head, are re¬ spectively disposed so as to engage each other, thereby establishing a juxtaposed alignment of said vertical side surfaces thereof.
4. The combination as recited in claim 3, wherein the engaging surface of said friction ring of said flange member is selectively determined by the diameter of said recess. SUBSTITUTESHEET .
5. The combination as recited in claim 4 , wherein said recess is formed having a diameter greater than the width of said drive head.
6. The combination as recited in claim 4, wherein said recess is formed having a diameter equal to the width of said drive head.
7. The combination as recited in claim 4, /■/herein said recess is formed having a diameter less than the width of said drive head.
8. The combination as recited in claim 4, wherein said frictional engaging surface of said frictional ring is formed having a plurality of radially extending teeth formed thereon.
9. The combination as recited in claim 3, including a socket wrench having a vertical engaging inner side surface adapted to be received over both said fastener head or nut, and said drive head of said lock washer, whereby said lock washer can be rotated simultaneously with, said fastener head or nut of said fastener.
10. A wedgeaction lock washer adapted for use with a wedgeaction fastener, said lock washer com¬ prising: a first body member and a lower second body member having a central bore disposed therein; said first body member defined by a drivehead member formed having a plurality of contiguous cam members and a plurality of wrenchengageable vertical, side surfaces; said second body member being defined by an annular extended flange member formed having a frictionalring member adapted to frictionally engage the surface of a workpiece.
11. A wedge^action lock washer as recited in claim 10, wherein said lower body member includes an annular recess whereby said annular frictional ring is. defined. SUBSTITUTESHEET .
12. A lock washer as recited in claim 11, wherein said annular recess has a diameter greater than the width of said first body member.
13. A lock washer as recited'in claim 11, wherein said annular recess has a diameter equal to the width of said first body member.
14. A lock washer as recited in claim 11, wherein said annular recess has a diameter less than the width of said first body member. SUBSTITUTESHEET.


Field of The Invention

The present invention relates generally to nut-and-bolt-type fasteners, and more particularly to a lock washer having an engaging cam surface disposed on a drive head, and an opposite frictional surface de¬ fined by an enlarged annular flange.

Description of The Prior Art

Various problems and difficulties are encountered in providing suitable lock washers of the cam-action type that will allow for simple means to unfasten associated fastening devices. When a known lock washer is installed and tightened with the cam face of the washer engaging under the head of a cam screw, the friction between the frictional surface of the washer and the joint material will prevent the washer from turning, if the cam screw is forced to turn in the loosening direction by vibrational forces or intentionally by the use of a wrench. Accordingly, the rise of the washer cams together with the cam screw is greater than the rise of the threads on the screw shaft. Thus, the cam is liable to turn in the loosening direction by vibrational forces, causing it to slide up the cam sur¬ faces of the interacting washer, of the cam head of the screw or bolt. This cam movement induces a wedging


action that jams the nut of the screw or bolt tightly between the threads on one side and the joint via the washer on the other side. Hence, when the cam screw is loosened by a wrench, the cams will override the tops of one another, which causes the bolt to become elon¬ gated. Such stretching of the bolt can also permanently damage it, if it is stretched beyond its elastic limit into the plastic region. If the fastener is repeatedly , disassembled and reassembled under the cam-overriding effect, it will eventually reach its breaking point and result in a fastener failure. The risk of fastener failures caused by repeated loosening by cam-overriding severely limits the employment of wedge-action lock washers, particularly for cap-screw applications,, which often involves the use of short clamp lengths.

As an example of the known art, there is dis¬ closed in United States Patent No. 3,417,802 to Oldenkott a captive lock-washer assembly which comprises a lock washer having a plurality of flat sides, and a cam sur- face formed on one side and a teeth-engaging surface on the opposite side. The body is designed so that the washer is extremely thin which entails the use of a minimum amount of metal in the fabrication process.


The present invention has for an important object to provide a flanged drive-head lock washer with a central drive head having a cross-sectional configura¬ tion to match, that of various commercially available nut- and-screw-head configurations, such as hex, six-point r eight-point, ten-point, twelve-point and torx heads.

Another object of the invention is to provide a flanged drive ■■■■■ -head washer having an enlarged flange so as to establish a greater frictional area when en¬ gaging the associated workpiece. Still another object of the invention is to


provide a, drive-head lock washer having an annular, en¬ larged-diameter, flange member that defines an extended moment arm of friction long enough to prevent the washer from turning in the loosening direction when sub- jected to vibrational forces. ■

A further object of the present invention is to provide a washer of this character wherein the washer includes two integral body members — one being the enlarged friction flange and the other being the drive head having a suitable configuration to match a drive socket — so that the washer is forced to turn together with the nut or cap screw as it is loosened, instead of being subject to cam-overriding which may cause damage to tha fastener. A still further object of the invention is to provide a washer of this type that is simple and relatively inexpensive to manufacture, so that it can be formed having a drive head that will match any given socket or con iguration, and the configuration of tha associated bolt head, screw head, or nut with which, it is to be used.

The characteristics and advantages of the invention are further sufficiently referred to in connec¬ tion with, the accompanying drawings, which represent one embodiment. After considering this example, skilled persons, will understand that variations may be made without departing from the principles disclosed; and I contemplate the employment • of any structures, arrange- ments. or modes of operation that are properly within the scope of the appended claims.


Referring more particularly to the accompany¬ ing drawings, which are for illustrative purposes only:


FIGURE 1 is an enlarged side-elevational view of the flanged drive-head lock washer in a locked arrangement with a fastening means wherein the nut thereof is formed having an engaging cam surface, and further showing a drive socket in a partial section and the fastener assembly being secured to a workpiece; FIGURE 2 is a cross-sectional view taken substantially along line 2-2 of FIGURE 1;

FIGURE 3 is a- top-plan view of the flanged- head lock washer;

FIGURE 4 is a cross-sectional view of the present invention taken substantially along line 4-4 of FIGURE 3;

FIGURE 5 is a bottom-plan view of the lock washer wherein the frictional surface of the annular flange is shown having radial teeth formed therein;

FIGURE 6 is a bottom-plan view of the lock washer wherein the frictional surface of the annular flange is substantially flat; FIGURE 7 is an enlarged cross-sectional view taken across one section of the washer wherein the an¬ nular flange has a small radial surface for greater flexibility between the drive head and the workpiece.; FIGURE 8 is a cross-sectional view similar to FIGURE 7> showing another form of the annular flange; FIGURE 9 is still another cross-sectional view similar to FIGURES 7 and 8, showing still another flange arrangement;

FIGURES 10, 11 and 12 illustrates three al- ternative drlive-head configurations;

FIGURE 13 is an elevational view of a twelve- point screw and a matching drive-head flanged washer; and,

FIGURE 14 is a partial cross-sectional view showing the present invention accommodating a second


washer member engaging the nut of a fastener.


Referring more particularly to FIGURE 1, there is shown a fastener means, generally indicated at 10 , which comprises a typical threaded bolt or screw 12 having a hexagonal head 14 and a matching hexagonal nut member 16 threaded to the bolt stud 17, the fastener 10 being secured to a workpiece 18 defined by members 20 and 22. However, according to the following detailed description of the invention, it will be readily under¬ stood that the configuration of the present invention, a flanged drive-head lock washer (designated at 24), can be suitably altered.to accommodate the various, fasteners having other head and nut shapes, such. as. found in six, eight and twelve-point screws.

The flanged drive-head lock washer 24 com¬ prises two integrally formed body members, one being defined by a drive-head member 26 and the other being defined by an annular, enlarged, washer flange 28. Drive head 26 is shown in FIGURES 1 through 6 as having the. general configuration of the typical hexagonal bolt or screw, wherein the drive head is formed having six contiguous wrench-engaging sides or surfaces 30. The drive head is. further provided having a central bore 32 through, which, the bolt or screw stud 17 is re¬ ceived.

The upper engaging surface of drive head 26 is formed having a plurality of contiguous cam members 34 (.illustrated as having at least three cam members) , each cam member being defined by an inclined cam surface 36 and a substantially vertical or slightly inclined front face member 38.


Washer flange 28 extends radially outward from the lower portion of drive head 26, so as to pro¬ ject the moment arm of the downward locking force as the fastener is secured to the workpiece. The upper 5. surface 40 of flange 28 is formed in an inclined manner, so that it is tapered downwardly and outwardly from drive head 26 as illustrated in FIGURES 4, 7, 8 and 9.

The undersurface of flange 28 defines a friction ring 42 which can vary in size and arrangement, 0 depending upon the diameter of the inner recess 43, which will hereinafter be described. Thus , the undersurface of friction ring 42 comes in direct engagement with the opposing surface of the workpiece, as seen in FIGURE 1. In FIGURE 4 flange 28 is shown provided with 5 a ring 42 having an inclined frictional surface 44 which allows various degrees of contact between frictional surface 44 and the surface of the workpiece 18. The degree of contact depends upon the degree of the securing force of the fastener * For example, the greater the 0 downward securing force, the larger the area of the

surface 44 that contacts the workpiece as the frictional ring flexes to a flat configuration.

Other frictional-ring variations are used under specific conditions, such as when the washer is 5 used with a soft material versus its use with a very- hard-surface material. Accordingly, in FIGURE 7, the friction ring 44a is formed along the outer edge of flange 28 wherein recess 43 has a diameter greater than the width of the drive head. That is, the radius "R" 0 of recess 43 extends outwardly from the side wall in¬ dicated by line "W". The width of the frictional ring 44a is less than the width, "d" of flange 28. FIGURE 9 illustrates, recess "R" as being located inwardly of wall "W" . Hence, frictional ring 44c has. a greater frictional 5 surface than width, "d" of flange 28.


With further reference to frictional ring 42, it is contemplated that a plurality of equally spaced radial teeth 45 can be incorporated to provide additional frictional means between the washers and the workpiece .

FIGURES 10 and 11 illustrate two types of common eight-point drive heads 26a and 26b having cam surfaces 36a and 36b, respectively. FIGURE 12 illustrates a flanged lock washer having a twelve-point drive head 26c and cam surfaces 36c. FIGURE 13 further shows a fastener 10 having a twelve-point match with a twelve-point flanged lock washer.

Referring again to FIGURE 1, it can be readily seen that nut 16 is locked in aligned wall-to-wall relationship to lock washer 24, whereby socket wrench 50 is mounted over nut 16 and drive head 26. This then allows both the nut and the washer to be rotated together and removed from the threaded stud 17, without causing damage to the fastener. A alternative arrangement or use is also contemplated, such as illustrated in FIGURE 14 wherein a typical nut 52 is employed and includes a suitable cam- ^ lock washer 54 having a cam surface 56 and a fric¬ tion surface 58 to engage the undersurface 60 of nut 52, rather than a single cam nut as shown in FIGURE 1.

The invention and its attendant advantages will be understood from the foregoing description; and it will be apparent that various changes may be made in the form, construction and arrangement of the parts of the invention without departing from the spirit and scope thereof or sacrificing its material advantages, the arrangement hereinbefore described being merely by way of example; and I do not wish to be restricted to the specific form shown or uses mentioned, except as defined in the accompanying claims.