FIELD OF THE INVENTION

The present invention relates in general to locking washers. In more particular the present invention relates to locking washers and self locking threaded fasteners.

BACKGROUND OF THE INVENTION

Locking the rotational motion of threaded fasteners, such that they will not be unintentionally opened called for various solutions. Exemplary are bolts and matching nuts in accordance with DIN 935, in which a peg inserted through a bore in the bolt locks the rotational motion of the bolt when is engaged with respective cogs on a matching nut. A different approach in which a washer provides for such locking according to DIN 432 is shown in Figs 1A - 1B; Upwardly bent segment 11 of LW 10 locks the rotational motion of nut 12 relative to bolt 14. Peg 16 provides for preventing any rotational motion of LW 10 relative to surface 17. Recess 18 disposed at the rim of LW 10 prevents such rotational motion by any of its side walls when is respectively engaged with peg 16. Similarly, German patent application 3313540 discloses locking washers that are accommodated to automatically locking threaded fasteners. These washers are only accommodated to rotationally locking threaded fasteners having spanner faces, namely only ones with polygonally shaped heads. US patent 1333529 discloses a locking washer which is in accordance with DIN 432. This washer has a circumferential cutout whose shape conforms to the corner disposed between adjacent spanner faces of the threaded fastener. Additionally a locking lip, or tongue, that sticks out of the washer's body and is upwardly bowed, pressing its beveled end in between neighboring threads of the threaded fastener. Such locking lip enhances the frictional forces opposing any rotational motion of the threaded fastener when the locking lip is pressed down by the fastener's head while is rotated in the closing direction. Any locking washer that locks the rotational motion of threaded fasteners (nuts, screws and/or bolts), providing an automatically activated locking action while rotating the respective fastener in a closing direction; that can be arranged so that the magnitude of the force exerted by the locked fastener onto the surface to which it is attached, is of a desired level, and that the magnitude of the torque required for closing said fastener is confined by respective desired limits; is beneficial.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1A is a sectional view of a locking washer (LW) according to DIN 432 locking the rotational motion of a nut screwed onto a bolt;

Fig. 1B is an elevational view of the LW shown in Fig. 1 ;

Fig. 2 is an isometric view of a LW according to an embodiment of the present invention while is locking the rotational motion of a nut screwed onto a bolt; Fig 3A is an isometric view of a bolt adapted to be rotationally locked by means of a LW according to an embodiment of the present invention;

Fig. 3B is an isometric view of a LW according to a preferred embodiment of the present invention

Fig. 3C is a sectional view of the LW shown in Fig. 3B placed at a rim of an aperture of a threaded bore;

Fig. 3D is an isometric view of the bolt shown in Fig. 3A prior to its being rotationally locked by means of the LW shown in Fig. 3C;

Fig. 3E is an isometric view of the bolt and LW shown in Fig. 3D at a locked state; Fig. 4 is an isometric view of a LW according to an embodiment of the present invention; Figs 5A - 5B are isometric views of two exemplary bolts accommodated to be rotationally locked by means of a LW according to another preferred embodiment of the present invention;

Fig. 5C is an isometric view of a segment of the surface to which any of the bolts respectively shown in Figs 5A - 5B are to be attached;

Fig. 5D is an isometric view of the LW shown in Fig. 5B;

Figs 6A is a schematic presentation of a LW according to another preferred embodiment of the present invention;

Fig. 6B is an elevational view of a bolt having conical head accommodated to be rotationally locked by means of the LW dshown in Fig. 6A;

Figs 6C - 6D are sectional and elevational views of a segment of the body to which the boklt shown in Fig. 6B is to be attached.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

In accordance with the present invention a locking washer and method for locking the rotational motion of threaded fasteners (nuts, screws and/or bolts) is provided. Washers normally have a central bore through which the shank of a fastener is introduced. A Locking washer (LW) interleaves between the bottom face of the head of a threaded fastener (Head) and a surface of a body to which the threaded fastener is attached to (Body).

LWs of the invention comprise of at least one positioning means and at least one locking mechanism. The positioning means and the locking mechanism are directed towards opposite faces of the LW. Namely, either the positioning means is facing the Body and the locking mechanism is facing the Head or vice versa, the positioning means is facing the Head and the locking mechanism is facing the Body.

Both the Body and the Head comprise each at least one engaging member. A positioning means is adapted and arranged to engage its engaging member such that, once a positioning means and the respective engaging member are mutually engaged thereby any rotation of the LW relative to the element containing the respective engaging member is blocked. A locking mechanism is adapted and arranged to automatically interlock with its engaging member such that, once a locking mechanism and the respective engaging member are mutually engaged any rotation of the LW relative to the element containing the respective engaging member is blocked. A locking mechanism of a LW of the invention is adapted and arranged to automatically interlock with its respective engaging member at the instant the threaded fastener accomplishes a rotation about its axis at a magnitude that equals a predefined rotational angle in which the locking mechanism engages the engaging member.

The engagers of the locking mechanisms of LWs of the invention, which are accommodated to be engaged with a respective engaging member either of the Head or the Body are enclosed within a given volume. This volume is confined by the surface of the bore of the LW, a face of the threaded fastener and the projection of this face onto the surface to which the threaded fastener is attached. In a case in which the respective engaging member is placed at Head, the automatic interlocking provides for blocking any rotational motion of the threaded fastener relative to the LW. In a case in which the respective engaging member is placed on the Body, the automatic interlocking blocks the rotational motion of the LW relative to the Body. Once a positioning means is engaged with its respective engaging member and a locking mechanism is interlocked with its respective engaging member, the LW prevents any rotational motion between the Body and the Head relative to the axis of the threaded fastener.

Locking mechanisms employed according to the invention can be any of the type of snap locks as known, in which a resilient member is forced to open and released to close and/or vice versa released to open and forced to close.

As the spatial orientation of a LW is arbitrary namely it can be oriented in any direction in space. The directions specified hereinafter normally refer to the components which are positioned adjacent to the LW considered. For example a LW that interleaves between a threaded fastener and the surface to which it is attached, has one face that faces the threaded fastener whereas its other face touches the surface. Normally the body of a LW of the invention is circular. Therefore dimensions measured along the radii are referred hereinafter as widths; lateral or tangential dimensions (that are normally measured along circular arcs) are referred as lengths, whereas dimensions axially measured along lines that are perpendicular to the faces of a LW are referred hereinafter as thicknesses or depths.

Reference is now made to Fig. 2 in which nut 20 is shown while is at a closed state and is rotationally locked by means of LW 22 . LW 22 that is in accordance with a preferred embodiment of the present invention interleaves between nut 20 and surface 24 to which it is attached. Nut 20 has been continuously rotated about its axis, which is the same axis of bolt 26, in a closing direction (shown by curved arrow 27). When the rotational angle by which nut 20 is rotated exceeds a given threshold, engaging member 28 of nut 20 is released off tongue 29, thereby locking of the rotational motion of nut 20 is accomplished. The free end of tongue 29 as well as sidewall 30 and the volume of niche 31 , all are integral components of the engager of the locking mechanism that is embedded according to the invention in LW 22. When the engaging member placed on nut 20 gets into the volume of niche 31 , such that it engages with the end of tongue 29 and/or sidewall 30, the rotational motion of nut 20 is blocked. The threshold limiting the rotational angle by which the threaded fastener is rotated is the respective rotational angle in which the locking mechanism embedded in the LW is locked. This threshold is derived in consideration with the magnitude of the force to be exerted by the threaded fastener into the connection accomplished by means of the pair nut 20 and bolt 26, as well as by the maximal level of torque to be exerted on the threaded fastener for its closing. Embodiment variants in which a recess implements the engaging member whereas a matching protrusion disposed at the free end of the tongue substitute niche 31 are in accordance with the present invention.

For better describing the features ot the present invention another exemplary case in which the threaded fastener considered is a screw, is hereby described with reference to Figs 3A - 3E. In Fig. 3 A an isometric view of screw 36 is shown. Screw 36 includes engaging member 38 which is a protrusion over the screw head 39). In Fig. 3B an isometric view of LW 40 according to a preferred embodiment of the present invention is shown. Body 41 of LW 40 encloses central bore 43 that provides LW 40 to be placed around the circumference of the thread. Tongue 44 occupies most of the inner space enclosed by slot 45 that spans across central angle 46 (the vertex of which disposed on the axis of LW 42, not shown). Tongue 44 is elastic due to its relatively small thickness. Such elasticity provides for bending tongue 44 when is stressed parallel to the axis of LW 42 and for springing it back to its former planar form when is released off. Such stress is exerted by an engaging member of the respective Head (such as engaging member 38 shown in Fig. 3A) when is slidingly rotated along tongue 44. One sidewall of tongue 44 is spaced apart from the lateral wall of slot 45. One end of tongue 44 is attached, or preferably integrally connected, to one sidewall of slot 45. The locking mechanism of LW 42 consists of tongue 44 and niche 48 housed in slot 45. The engager of this locking mechanism is implemented by niche 48 that is disposed between the free end of tongue 44 and sidewall 50. Its geometrical shape conforms to the lateral dimensions of the engaging member of Head of the threaded fastener considered. The angle of introduction is the rotational angle in which the threaded fastener has to be rotated such that the respective engaging member starts touching tongue 44 as close as possible to the connected end of tongue 44. The magnitude of the angle of introduction is defined by the orientation of the LW relative to the threads associated with the threaded fastener considered. This angle can be increased or decreased by respectively rotating the LW about its axis in the closing direction. The magnitude of the angle of introduction, the level by which the engaging member extends off the face of the threaded fastener (the same face that faces LW 42) towards LW 42; the lateral dimensions of this engaging member; the length of tongue 44; the length of niche 48 which is the length of the engager of the locking mechanism considered; the pitch of the threads of the threaded fastener considered; the materials from which the LW as well as both the male and female threads are made, as well as the material from which the body a surface of which is the surface to which the LW is to be attached is made, All these parameters uniquely define the level of the force to be exerted by the threaded fastener on LW 42 as well as the magnitude of the torque required for rotating the fastener into a closed state. The rotational angle its magnitude equals the sum of the angle of introduction and the central angle spanned by the tongue is the respective threshold angle beyond which the threaded fastener has to be rotated to get into a closed state. The magnitude of this angle is uniquely related to the magnitude of the torque required for closing the threaded fastener and to the magnitude of the force exerted onto the LW. Depth 51 , which is the maximal distance along which the free end of tongue 44 can move when is pressed by the respective engaging member (positioned at the respective face of the threaded fastener) is selected in consideration with the length of tongue 44 and the pitch of the threaded fastener In Fig. 3C LW 54 which is similar to the LW described above is shown placed on top of surface 55 circumferential to the aperture of bore 56. The threads of bore 56 conform to the threads of the bolt or screw considered. Such threads that accommodate the threads of the threaded fastener considered are referred hereinafter as the receiving threads. Positioning means 57 which is prominent off the LW extends into the respective engaging member indented at the rim of the aperture of bore 56. Positioning means 57 is placed at a specified location positioned relative to the receiving threads. Both positioning means 57 and the external engager provide for avoiding any rotation of LW 54 about its axis when respective torques are exerted onto LW 54 while bringing the bolt into the closed state. The site in which the respective engaging member is axially located relative to the threads is selected in consideration with a specified point positioned relative to the threads in which the engaging member of the locking mechanism of LW 54 first touches the surface of LW 54 while is rotated at a closing direction, such that it touches the tongue as close as possible to its connected end. Embodiment variants in which a niche implements the positioning means of a LW whereas a matching protrusion placed either on a face of the threaded fastener, or on the surface to which the threaded fastener is attached, implements this engaging member are in accordance with the present invention. In Figs 3D - 3E two stages, such as by respective snapshots taken at two different points in time, of the process of the locking activity effected by the locking mechanism according to a preferred embodiment of the present invention are respectively shown. (The parts are designated by the same numbers in Figs 3D and 3E). The locking mechanism of LW 60 is first activated at the rotational angle that equals the angle of introduction. The LW can not rotate about its axis as it is fixed to the surface by a positioning means (not shown). Engaging member 62 starts pressing against tongue 64 while threaded fastener 65 is continuously rotated by the angle of introduction at the closing direction, shown by curved arrow 66. In Fig. 3D tongue 64 is shown bended almost to its maximal extent in the direction shown by arrow 67. At the point in time in which external engaging member 62 stops pressing against tongue 44 while is being continuously rotated at the same closing direction, tongue 44 is sprung back to the same non-stressed state and position in which it was prior to the stage that engaging member 62 started pressing it, and the locking mechanism is activated, as shown in Fig. 3E. Locking is accompanied by a "click" signaling the user accordingly. The rotational motion of engaging member 62 as well as of the threaded fastener in the direction of arrow 66 is blocked by sidewall 68 of the niche of the locking mechanism of LW 60. The free end of tongue 64 blocks any rotational motion of threaded fastener 65 in the opposite (the opening) direction, hence, any rotational motion of threaded fastener 65 is prevented, unless the level of the free end of tongue 64 is forced back to its extreme bended state which occurred immediately prior to the point in time in which the threaded fastener gets into the closed state, such that the threaded fastener can be unscrewd.

When the tongue of a locking mechanism of a LW of the invention does not extend beyond the rim of the threaded fastener, such LW and the complementary threaded fastener may provide for closing an enclosure such that a tamper evident means is provided. Reference is now made to Fig. 4 in which a sectional view of tamper evident screw 90 that is accommodated to be rotationally locked with LW 92, which is according to an embodiment of the present invention, are shown while being at a closed state. The outline of the missing portion of the face of screw 90 that faces LW 92 is presented by dashed line 94. Screw 90 and LW 92 are attached to the surface 95 of an enclosure, not shown. Engaging member 96 that protrudes off the face confined by dashed lines 94 is enclosed within the niche disposed between the free end of the tongue of LW 92 and the respective sidewall of the slot housing this locking mechanism. Circumferential sidewall 97 extends off the face of screw 90 skirts LW 92 such that the tongue of LW 92 cannot be accessed from the outside when screw 90 is at a closed state. Alternatively, the slot housing the locking mechanism can be structured circumferential to the bore of the LW, such that the body of the LW blocks any access towards the bendable tongue. A breakable or rupturable tongue and an optional window disposed at this sidewall at a site facing the tongue provide for visually inspecting whether an unauthorized opening of the threaded fastener, hence damaging the LW has occured. Furthermore, any segment of the body of a LW of the present invention can be such geometrically shaped and/or sized, or made of such material that makes the LW breakable or rupturable at a site disposed within this segment. Such LW provides for tamper evident connection as any opening of the respective threaded fastener involves breaking or tearing off the respective LW.

Optionally, a bore having two apertures, is structured through the screw head such that its inner aperture faces the tongue at a site adjacent to its free end; the other aperture is located at the external face of the head of the screw. This aperture is typically sealed off with a tamper evident seal as known. The seal does not interfere when rotating the screw such as by a screwdriver or hexagonal key. However for opening and releasing off screw 90 first the seal has to be removed such that the screw will be rotationally unlocked. Unlocking is accomplished by pressing the free end of the tongue to bend it until its end lies beyond the level of the extreme face of the respective engaging member. A slender shaft the cross section of which conforms to the cross section of the bore provides for unlocking the rotationally locked screw. Following pressing the tongue beyond the level of the free face of the engaging member the screw is rotated slightly in the opening direction. By such rotation the free end of the bended tongue is supported by the free face of the engaging member. From this stage on, the respective engaging member can be further slidingly rotated along the face of the tongue such that the screw can be continuously rotated in the opening direction.

Any common tool, that is normally used for rotating a threaded fastener such as a screw, bolt or nut; that is normally provided with a key adapted and arranged for rotating the threaded fastener considered; that is further provided with a lever laterally shifted off its main axis, such that it avoids the periphery of the threaded fastener and yet provides for pressing against the periphery of the tongue extending beyond the edge of the threaded fastener considered, can be employed for opening and releasing off such rotationally locked threaded fastener. Obviously, a lever that can be introduced through a bore structured in the body of the threaded fastener such that its apertures face the tongue of the LW is in accordance with the present invention.

A LW according to an embodiment of the present invention that provides a user with an extended tolerance in the level of the torque required for closing the threaded fastener is provided with two or three different locking mechanisms. Alternatively a number of locking members accommodated to automatically interlock with the same locking mechanism of a LW at different respective rotational angles may similarly provide for such desired tolerance. Reference is now made to Figs 5A - 5D. In Figs 5A - 5B two different bolts each of which has series 102 of locking members evenly placed across the side facing the LW. Trapezoidal grooves implement these locking members. Groove 108 structured on surface 110 shown in Fig. 5C implements the respective engaging member accommodated to positioning means of LW 112. This LW which is according to another preferred embodiment of the present invention that is shown in Fig. 5B and in more details in Fig. 5D. Two identical elongated and bendable tongues 114 are symmetrically disposed at opposing sides of LW 112. The free end of each tongue 114 is such bended that it points off the respective face of LW 112. Any of these tongues can serve as a positioning means as well as the locking mechanism of this LW as further described in the example below.

Reference is now made to Figs 6A - 6D. In Fig. 6A a conical LW according to a preferred embodiment of the present invention is schematically shown. The locking mechanism of conical LW 120 consists of prism 122 protruding off resilient tongue 124. Prism 126 that protrudes to the opposite side of LW 120 implements the positioning means of LW 120. LW 120 provides for rotationally locking bolts having conically shaped countersink screw heads such as bolt 130 shown in Fig. 6B. groove 132 implements the external locking member accommodated to enclose prism 122. In Figs 6C - 6D sectional and elevational views of the bore accommodated to receive bolt 130 are respectively shown. Recess 132 implements the external engager accommodated to receive prism 126 of the positioning means of LW 120.

EXAMPLE

The positioning means of a LW of the invention can be implemented by one of the locking mechanisms of the LW considered. Reference is again made to Fig. 5D in which LW 112 according to another embodiment of the present invention is shown. The free ends 116' and 116" of tongues 114 are respectively bended towards opposite directions, such that each can operate as a positioning means or a locking mechanism. When a tongue serves as a positioning means, the tongue whose end faces the opposite direction serves as a locking mechanism and vice versa. LWs such structured provide the operator with flexibility of use and prevents placement errors. The operator selects the specific rotational angle in which the fastener is finally locked by choosing the level of magnitude of the torque applied for closing the threaded fastener. For closing such fastener the operator first engages the positioning means of the LW which is one of the bended segments 116 with the suitable engaging member placed on the surface of the object in which the receiving bore is structured. Then the operator introduces the threaded fastener into the bore of the LW and further rotates the threaded fastener all along the angle of introduction. From this moment on, any slight rotation in the closing direction activates interlocking, as the locking member spontaneously springs into the current locking member that faces the respective bended segment of the locking mechanism of the LW. However the operator may enhance the level of the torque applied in the closing direction, thereby the inclined sidewall of the external engaging member forces the engager of the locking mechanism to be depressed towards the surface of the body to which the fastener is attached and be released off the current engaging member. By continuing rotating the threaded fastener further in the closing direction the adjacent engaging member that is successively located on the face of the threaded fastener is brought to be the new current engaging member that faces the engager of the locking mechanism. At this point the internal engager is sprung into the recess implementing the current engaging member.

LW such as LW 112 provides for blocking the rotational motion in the opening direction of the threaded fastener considered. However the operator may further rotate the threaded fastener considered by continuously increasing the level of the torque applied onto the threaded fastener for its closing. Such rotating in the closing direction can be continued as long as there is a room for depressing the internal engaging member towards the surface of the object to which it is attached, such that the engager is freed off the respective engaging member. In cases in which the thickness of the LW exceeds the depth of the free end of the bended tongue, such that it cannot get beyond the volume enclosed by the body of the LW ₁ the only limiting factor for further rotation in the closing direction is the magnitude of the resisting force applied by the body to which the threaded fastener is attached onto the threaded fastener. Therefore, in such cases the rotational angle in which the locking is effected is dependant only on the magnitude of the torque applied by the user. Namely, a number of rotational angles successively arranged provide for automatic interlocking the threaded fastener considered. All of these rotational angles except for the last angle provide for blocking the rotational motion of the threaded fastener in the opening direction. However, the last of these rotational angles provides for blocking the rotational motion of the threaded fastener in any of the closing and/or opening directions. The number of such rotational angles is dependent on the dimensions of the engaging members considered, the pitch of the threads of the threaded fastener and the height of the spacing located between the tongue of the locking member and the surface of the object to which the threaded fastener is attached.