Anti-tampering device that envelopes the head of a fastener

An anti-tampering device includes a housing with a bolt channel and a lock channel. The lock channel is aligned with, intersects and is perpendicular to the bolt channel. A head of a bolt and a portion of a shank of a bolt is received in the bolt channel. A lock received in the lock channel extends into the bolt channel, in proximity to the shank of the bolt, when the lock is in a locked position. The portion of the lock extending into the bolt channel prevents removal of the head of the bolt from the bolt channel.

FIELD OF THE INVENTION

This invention relates generally to anti-tampering devices that envelope a head of a fastener, and, more particularly, to a locking apparatus that envelopes, conceals and prevents access to the head of a bolt.

BACKGROUND

Various security and tamper-resistant bolts have been devised to reduce risk of disassembly of objects bolted together. Many of these bolts require special tools for installation. Some of these bolts cannot be removed without cutting. Often, the head of the bolt is exposed, which invites tampering.

Other tamper resistant devices include tubes for containing bolt heads or nuts and caps for covering the open end of the tubes. Yet other tamper resistant devices include bolt shanks with through-holes engaged by locks.

By way of example, U.S. Pat. No. 4,444,031 describes a security device for tackle boxes and the like. The device is a hollow cylinder with an open end and an opposite end with a screw hole. A screw extends through the screw hole and secures the cylinder to a wall or floor. A tool box, safe or tackle box has a hole in the bottom. The hole is sized and shaped to receive the cylinder. Aligned holes extend through the wall of the cylinder near the open end. A U-shaped shackle of a pad lock extends through the aligned holes. The shackle impedes access to the screw head contained in the cylinder.

As another example, U.S. Pat. No. 4,751,831 describes a lock for a meter housing. The lock includes a bolt threaded into an anchor (i.e., an angle bracket) inside the housing. The head of the bolt extends through the housing and through an opening in a latch on a door. A puck lock engages the head of the bolt. In the preferred embodiment, the head of the bolt is specially shaped (e.g., hourglass shaped) with a curvature that mates with (i.e., abuts) a portion of the periphery of a locking element in the puck lock. This lock relies upon the abutting interplay of the hourglass head and locking element to resist withdrawal. As the locking element and head are not aligned, slight skewing of the bolt would be enough to release the bolt.

As another example, U.S. Pat. No. 5,078,437 illustrates a pivoting handle in a locked position. A shackle of a padlock extends through a hole in the handle and through an adjacent hole in a cylinder bolted to a door. The shackle impedes access to the head of a bolt in the cylinder.

As another example, U.S. Pat. No. 6,684,548 describes a security device for a firearm. The device is a hollow cylinder with an open end and an opposite end with a screw hole. A screw extends through the screw hole and secures the cylinder to a wall or other surface. The cylinder is sized and shaped to extend through a trigger guard between the trigger and trigger guard. Aligned holes extend through the wall of the cylinder near the open end. A U-shaped shackle of a padlock extends through the aligned holes. The shackle prevents access to the screw head contained in the cylinder. The padlock prevents removal of the firearm from the cylinder.

An anti-tampering device that conceals and prevents access to the head of a conventional bolt or screw, or to another conventional engageable element on a bolt or screw, such as a nut, is needed. The device should be easy to use and capable of achieving good locking performance with conventional bolts, screws, and nuts.

The invention is directed to overcoming one or more of the problems and solving one or more of the needs as set forth above.

SUMMARY OF THE INVENTION

To solve one or more of the problems set forth above, in a non-limiting exemplary implementation of the invention, an anti-tampering device includes a housing with a front side and a back side. The back side is opposite the front side. A bolt channel extends into the housing from the back side of the housing. The bolt channel has a central longitudinal axis, an open end and a closed end. The open end of the bolt channel is at the back side of the housing. The closed end of the bolt channel is within the housing.

A lock channel extends into the housing. The lock channel has a central longitudinal axis. The central longitudinal axis of the lock channel is perpendicular to the central longitudinal axis of the bolt channel. The central longitudinal axis of the lock channel and the central longitudinal axis of the bolt channel are in planar alignment. Thus, the axes lie in an imaginary plane. The lock channel has an open end and a distal end. The inner end of the lock channel is opposite the open end of the lock channel and is within the housing. The inner end of the lock channel intersects the bolt channel between the open end of the bolt channel and the closed end of the bolt channel.

A lock is slidably received in the lock channel. For clarification, the lock may move linearly within the lock channel, in both directions (i.e., inwardly and outwardly), when movement is not restrained by a locking element. The lock includes an outer end and an inner end opposite the outer end. The lock is movable from a locked position to an unlocked position. In the locked position, the inner end of the lock extends through the inner end of the lock channel into the bolt channel. In the unlocked position the inner end of the lock does not extend through the inner end of the lock channel into the bolt channel.

The lock includes an outer sleeve with a locking aperture. The lock also includes a locking element that is movable between a retracted position and an extended position. In the extended position, the locking element extends through the locking aperture. In the retracted position, the locking element does not extend through the locking aperture.

The housing includes a cavity aligned with the locking aperture. The locking element extends through the locking aperture into the cavity when the locking element is in the extended position, in the locked position. By way of example, the locking element may comprise a sphere, a cylinder, a wedge, or an element having another shape. The cavity may be an annular compartment undercut in the locking channel, a section of such an annular compartment, or another channel that intersects the locking channel.

The lock includes a guide defining a range of linear motion of the lock. The range of linear motion is between a locked position and an unlocked position. The guide may be an elongated keyseat (e.g., an elongated recess or slot). A key may extend from the housing into the elongated keyseat. The keyseat has a longitudinal axis that is parallel to the central longitudinal axis of the lock channel. A set screw (i.e., key) has a shank threaded into the housing. A tip of the set screw extends from the shank into the keyseat, limiting linear movement of lock, but not preventing linear motion within the range of motion defined by the keyseat.

The housing includes a threaded channel in which the shank of the set screw is threadedly received. The threaded channel extends from the back side of the housing to the lock channel.

The bolt includes a shank and an engageable element on the shank. The engageable element and a portion of the shank are received in the bolt channel. The received engageable element is adjacent to (i.e., in proximity to or abutting) the closed end of the bolt channel. The engageable element is an object that is permanently or removably on the shank, fits within the bolt channel and is blocked from removal by the lock when the lock is in the locked position. By way of example, the engageable element may be a head of the bolt or a nut threaded on the shank of the bolt. The engageable element has a width or diameter that exceeds the width or diameter of the shank of the bolt. Where the engageable element meets the shank, the engageable element and shank are concentric.

A nut may also be threaded on the shank, with the back side of the nut adjacent to the open end of the bolt channel and adjacent to the back side of the housing. In this embodiment the nut is at or near the open end of the bolt channel while the engageable element is at or near the closed end of the bolt channel. When the lock is in the locked position and the engageable element is in the bolt channel at or near the closed end of the bolt channel, the lock prevents withdrawal of the engageable element. The nut at the back side of the housing prevents skewing the bolt relative to the housing.

A head of a bolt or an end of a bolt with a nut may extend from an object. By way of example and not limitation, the object may be an article of manufacture, an apparatus, or a machine. An anti-tampering device according to principles of the invention may contain and lock the bolt head or nut in the housing. The back side of the housing may be flush (or about flush) against the article of manufacture, apparatus, or machine, while the bolt head or nut is locked in the anti-tampering device.

The invention may be applied to any bolt that has sufficient length for fastening and for being engaged in an anti-tampering device according to principles of the invention. A user may readily determine the length of a bolt required for fastening, and the additional length required to engage an anti-tampering device according to principles of the invention.

DETAILED DESCRIPTION

With reference to the drawings, an exemplary anti-tampering device100according to principles of the invention protects, from tampering, a head140of a bolt130and/or a nut threaded on a threaded shank131of a bolt130. Tampering may entail unauthorized removal and disassembly. Protection is achieved by retaining the bolt head140or a nut in a housing105. A lock200prevents withdrawal of the bolt head140or nut from the housing105. The housing105does not impede rotation of the bolt130, bolt head140or nut relative to the housing. Rotation of the housing105will not cause rotation of the bolt130, bolt head140or nut.

For convenience of reference, the term bolt is used herein to broadly encompass any threaded fastener. Nonlimiting examples include conventional bolts, screws and threaded studs, regardless of whether the threaded fastener is used for assembly of two or more unthreaded components with the aid of a nut, or is used to attach an object to another object that includes a threaded opening for threaded mating with the threaded fastener.

With reference toFIGS.1-3and7-9, the exemplary anti-tampering device100includes a housing105with a front side107and a back side108. The back side108is opposite the front side107. The front side107faces outwardly from a received portion of a bolt130. In use, the back side108of the housing105abuts or is positioned immediately adjacent to an object from which the bolt130extends. This arrangement, relative to the object from which the bolt130extends, renders the back side108of the housing105substantially inaccessible, when the anti-tampering device100is locked to a bolt130.

A bolt channel110extends into the housing105from the back side108of the housing105. The bolt channel110has a central longitudinal axis, l1, as shown inFIG.4, an open end111and a closed end112. The exemplary bolt channel110has a length, d7, and a circular cross section shape with a diameter, d8. The open end111of the bolt channel110is at the back side108of the housing105. The closed end112of the bolt channel110is within the housing105. The closed end112of the bolt channel110is a distance, d6, away from the intersection of the lock channel150, described below. The distance, d6, as shown inFIG.7, is at least as great as the thickness, d2, of the engageable element (e.g., head)140of the bolt130, as shown inFIG.4. The length of the bolt130exceeds the length, d7, of the bolt channel110. The diameter, d8, of the bolt channel110is at least as great as the maximum width, d3, of the engageable element (e.g., head)140of the bolt130, as shown inFIG.4. The distance, d1, as shown inFIG.4, from the end of the engageable element (e.g., head)140of the bolt130to the outer end of the jam nut135is about equal (±10%) to the length of the bolt channel110, d7. A bolt channel110with these dimensions receives the engageable element (e.g., head)140of the bolt130, and a portion of the shank131of the bolt130. A housing105with a bolt channel110with these dimensions does not cause rotation of the engageable element (e.g., head)140of the bolt130when the housing105is rotated.

As shown inFIGS.3,7and8, a lock channel150extends into the housing105. The lock channel150has a central longitudinal axis, l2, as shown inFIG.4. The central longitudinal axis, l2, of the lock channel150is perpendicular to the central longitudinal axis, l1, of the bolt channel110. The central longitudinal axis, l2, of the lock channel150and the central longitudinal axis, l1, of the bolt channel110are in planar alignment. Thus, both axes, l1and l2, lie in an imaginary plane. The lock channel150has an open end151and an inner end152. The inner end152of the lock channel150is opposite the open end151of the lock channel150and is within the housing105. The inner end152of the lock channel150intersects the bolt channel110between the open end111of the bolt channel110and the closed end112of the bolt channel110. The closed end112of the bolt channel110is a distance, d6, away from the intersection of the lock channel150.

In the exemplary embodiment, the lock channel150has a circular cross-section shape, with a diameter, d9. The diameter, d9, is at least as great as the diameter, d5, of the tubular cylindrical outer sleeve155of the lock200, as shown inFIGS.4-9. In the exemplary embodiment, the length, d4, of the outer sleeve155of the lock200is greater than the length, d10, of the lock channel150, measured from the open end to the intersection. The difference between the length, d4, of the outer sleeve155of the lock200and the length, d10, of the lock channel150, is the distance by which the outer sleeve155of the lock200extends into the bolt channel110. This difference is less than the distance between the shank131of the bolt130and the intersection at the inner end152of the lock channel150. Thus, the end208of the outer sleeve155of the lock200is in proximity to, but does not reach the shank131of the bolt130, when the lock200is fully inserted in the lock channel150. Concomitantly, the end208of the outer sleeve155of the lock200, which protrudes into the space between the shank131and the intersection at the inner end152of the lock channel150, prevents withdrawal of the engageable element (e.g., head)140of the bolt130in the bolt channel110.

In the illustrated exemplary embodiment, the diameter, d9, is about the same, only slightly greater than the diameter, d5, of the tubular cylindrical outer sleeve155of the lock200, as shown inFIGS.4-9. The distance, d6, as shown inFIG.7, is at least as great as, but only slightly greater than, the thickness, d2, of the engageable element (e.g., head)140of the bolt130, as shown inFIG.4. In this configuration, the outer sleeve155of the lock200restrains the engageable element (e.g., head)140of the bolt130from any appreciable linear movement in the bolt channel110. A portion of the engageable element (e.g., head)140of the bolt130is sandwiched (i.e., disposed) between the end208of the outer sleeve155of the lock200, and the closed end112of the bolt channel110. The engageable element (e.g., head)140of the bolt130may be removed from the lock channel110, only when the end208of the outer sleeve155of the lock200is withdrawn to at least the intersecting end152, towards the open end151of the lock channel150.

The lock200is a locking assembly that is slidably received in the lock channel150. For clarification, the lock200may move linearly within the lock channel150, in both directions (i.e., inwardly and outwardly), when movement is not restrained by a locking element210. The lock200includes an outer end205and an inner end208opposite the outer end205. The lock200is movable from a locked position to an unlocked position. In the locked position, the inner end208of the lock extends through the inner end152of the lock channel150into the bolt channel110. In the unlocked position, the inner end208of the lock200does not extend through the inner end152of the lock channel150into the bolt channel110.

The lock200includes an outer sleeve155with a locking aperture160. The lock200also includes a locking element210that is movable between a retracted position and an extended position. In the extended position, the locking element210extends through the locking aperture160. In the retracted position, the locking element210does not extend through the locking aperture160.

The housing105includes a channel or cavity162aligned with the locking aperture160. The locking element210extends through the locking aperture160into the cavity162when the locking element210is in the extended position. While a cylindrical locking element is depicted, the locking element210may comprise elements having other shapes. In one embodiment, the locking element210is spring biased within the lock200into an extended position and retracted by unlocking the lock200. In another embodiment, the locking element210may be spring biased within the lock200into a retracted position and extended by locking the lock200. In yet another embodiment, the locking element210is moved between an extended position and a retracted position by one or more linkages within the lock200that are actuated upon locking and unlocking.

The lock200includes a guide170defining a range of linear motion of the lock. The range of linear motion is between a locked position and an unlocked position. In the illustrated embodiment, the guide170is an elongated keyseat (e.g., an elongated recess or slot). A key165may extend from the housing105into the elongated keyseat comprising the guide170. keyseat has a longitudinal axis, l3, that is parallel to the central longitudinal axis, l2, of the lock. In the exemplary embodiment, the key165is a set screw. The set screw has a shank threaded into a threaded channel115of the housing105. The housing105includes a threaded channel115in which the shank of the set screw is threadedly received. The threaded channel115extends from the back side108of the housing105to the lock channel150. A tip of the set screw extends from the shank into the keyseat170, limiting linear movement of lock200, but not preventing linear motion within the range of motion defined by the keyseat170.

The bolt130includes a shank131and an engageable element140on the shank. The engageable element140and a portion of the shank131are received in the bolt channel110. The received engageable element140is adjacent to (i.e., in proximity to or abutting) the closed end112of the bolt channel110. The engageable element140is an object that is permanently or removably on the shank131, fits within the bolt channel110and is blocked from removal by the lock200when the lock200is in the locked position. By way of example, the engageable element140may be a head of the bolt130, or a nut threaded on the end of the shank of a stud. Such a head or nut is typically hexagonal in cross section shape, and has a maximum width that is not greater than the diameter, d8, of the bolt channel110. Such width of the engageable element140exceeds the diameter of the shank131of the bolt130. Where the engageable element140meets the shank131, the engageable element140and shank131are concentric.

In the illustrated exemplary embodiment, the entire shank131is threaded. However, the invention is not limited to such a fastener. Fasteners with shanks having threads extending only partially along the shank, such as from the free end of the shank to a point between the free end and the engageable element (e.g., head) of the shank, may be used within the scope of the invention.

A nut135(e.g., a jam nut) may also be threaded on the shank131, with the back side of the nut adjacent to the open end111of the bolt channel110and adjacent to the back side108of the housing105. In this embodiment the nut135is at or near the open end111of the bolt channel110while the engageable element140is at or near the closed end112of the bolt channel110. When the lock200is in the locked position and the engageable element140is in the bolt channel110at or near the closed end112of the bolt channel110, the lock200prevents withdrawal of the engageable element140.

A bolt130may extend from an assembled object. By way of example and not limitation, the object may be an article of manufacture, an apparatus, or a machine. An anti-tampering device100according to principles of the invention may contain and lock the bolt head or nut in the housing105. The back side108of the housing105may be flush (or about flush) against the article of manufacture, apparatus, or machine, while the bolt head or nut is locked in the anti-tampering device100. In this configuration, the device100prevents access to the head of the bolt130and prevents removal of the bolt130.

Referring toFIG.1, a profile view of an exemplary anti-tampering device100according to principles of the invention is provided. The housing105, including the front107and back108sides, are shown. A portion of the shank132of a bolt130extends from the open end111of the bolt channel110. The section line B-B corresponds to the section view ofFIG.12.

FIG.2provides a first perspective view of the exemplary anti-tampering device100. The housing105, including the front107side, is shown. A portion of the shank132of a bolt130extends from the open end111of the bolt channel110at the back side108of the housing. The section line A-A corresponds to the section view ofFIG.7.

FIG.3provides a second perspective view of the exemplary anti-tampering device100. The housing105, including the front107and back108sides, are shown. A portion of the shank132of a bolt130extends from the open end111of the bolt channel110at the back side108of the housing105. A threaded channel115is provided for a set screw that serves as a key165. The threaded channel115extends from the back side108of the housing105to the lock channel150. A portion of the shank132of the bolt130may be threaded into another object. A jam nut135is shown in the bolt channel110at the back side108of the housing105. The lock channel150with the outer sleeve155of the lock200inserted into the lock channel150are also visible inFIG.3.

FIG.4illustrates the locking mechanism with a profile view of an exemplary fastener and locking ferrule (i.e., outer sleeve155of lock200) for an exemplary anti-tampering device100. The longitudinal axis, l1, of the bolt channel110is shown. This imaginary axis extends longitudinally through the center of the bolt channel110. Likewise, the longitudinal axis, l2, of the lock channel150is shown. This imaginary axis extends longitudinally through the center of the lock channel150. The longitudinal axis, l1, of the bolt channel110is perpendicular to the longitudinal axis, l2, of the lock channel150. Additionally, the longitudinal axis, l1, of the bolt channel110is in planar alignment with the longitudinal axis, l2, of the lock channel150. Thus, the longitudinal axis, l1, of the bolt channel110and the perpendicular longitudinal axis, l2, of the lock channel150lie in an imaginary plane. The end208of the outer sleeve155is positioned in the bolt channel110adjacent to the shank131of the bolt130, without contacting the shank131. The perpendicular arrangement and planar alignment ensure positive locking. The outer sleeve155of the lock200provides a barrier to removal of the head140of the bolt130.

The exemplary bolt channel110has a length, d7, and a circular cross section shape with a diameter, d8. The closed end112of the bolt channel110is a distance, d6, away from the intersection of the lock channel150. The distance, d6, as shown inFIG.7, is at least as great as the thickness, d2, of the engageable element (e.g., head)140of the bolt130, as shown inFIG.4. The length of the bolt130exceeds the length, d7, of the bolt channel110. The diameter, d8, of the bolt channel110is at least as great as the maximum width, d3, of the engageable element (e.g., head)140of the bolt130, as shown inFIG.4. The distance, d1, as shown inFIG.4, from the end of the engageable element (e.g., head)140of the bolt130to the outer end of the jam nut135is about equal (±10%) to the length of the bolt channel110, d7.

FIGS.5and6provide perspective views of an exemplary fastener and locking ferrule, i.e., outer sleeve155of the lock200, for the exemplary anti-tampering device100according to principles of the invention. When fully assembled, the outer sleeve155contains a locking mechanism and constitutes part of the lock assembly200, an exemplary embodiment of which is illustrated inFIGS.10and11. The exemplary lock (i.e., lock assembly)200includes outer sleeve155with locking aperture160. The sleeve is a hollow cylindrical tubular structure with a closed upper end208and an opened end opposite the upper end208. A lock mechanism is received in the opened end. The lock mechanism includes a locking element210. The locking element210is movable between a retracted position and an extended position. In the extended position, the locking element210extends through the locking aperture160. In the retracted position, the locking element210does not extend through the locking aperture160. The locking element210extends through the locking aperture160into the cavity162in the housing105when the locking element210is in the extended position. While a cylindrical locking element210is depicted, the locking element210may comprise elements having other shapes. The invention is not limited to any particular shape of locking element210, sleeve155, locking aperture160or corresponding cavity162. Shapes other than those illustrated may be implemented within the scope of the invention.

Also apparent inFIGS.5and6, the sleeve155includes a guide170defining a range of linear motion of the lock200. The range of linear motion is between a locked position and an unlocked position. In the illustrated embodiment, the guide170is an elongated keyseat (e.g., an elongated recess or slot). A key165may extend from the housing105into the elongated keyseat comprising the guide170. keyseat has a longitudinal axis, l3, that is parallel to the central longitudinal axis, l2, of the lock. In the exemplary embodiment, the key165is a set screw. The set screw has a shank threaded into a threaded channel115of the housing105. The housing105includes a threaded channel115in which the shank of the set screw is threadedly received. The threaded channel115extends from the back side108of the housing105to the lock channel150. A tip of the set screw extends from the shank into the keyseat170, limiting linear movement of lock200, but not preventing linear motion within the range of motion defined by the keyseat170.

InFIGS.5and6, the sleeve155is shown in the locked position. In the locked position, the upper end208of the sleeve155is in proximity to, without contacting, the shank131of the bolt130. The end208of the sleeve155is disposed between nut135and bolt head140. In the locked position, the end208of the sleeve155blocks withdrawal of the head140of the bolt130from the bolt channel110. In the unlocked position, the end208of the sleeve155is away from the shank131of the bolt130a sufficient distance, so as to not block withdrawal of the head140of the bolt130from the bolt channel110. The outer sleeve155of the lock200thus provides a barrier to removal of the head140of the bolt130, when the lock200is in a locked position, and not when the lock200is in an unlocked position.

FIG.7provides a section view (Sect. A-A) of the exemplary anti-tampering device100with the sleeve155in a locked position, according to principles of the invention. The exemplary bolt channel110, which extends into the housing105from the back side108of the housing105, has a length, d7, and a circular cross section shape with a diameter, d8. The open end111of the bolt channel110is at the back side108of the housing105. The closed end112of the bolt channel110is within the housing105, a distance, d6, away from the intersection of the lock channel150. The distance, d6, as shown inFIG.7, is at least as great as the thickness, d2, of the engageable element (e.g., head)140of the bolt130. The length of the bolt130exceeds the length, d7, of the bolt channel110. The diameter, d8, of the bolt channel110is at least as great as the maximum width, d3, of the engageable element (e.g., head)140of the bolt130, as shown inFIG.4. The distance, d1, as shown inFIG.4, from the end of the engageable element (e.g., head)140of the bolt130to the outer end of the jam nut135is about equal (±10%) to the length of the bolt channel110, d7. The bolt channel110with these dimensions receives the engageable element (e.g., head)140of the bolt130, and a portion of the shank131of the bolt130. The housing105with a bolt channel110with these dimensions does not cause rotation of the engageable element (e.g., head)140of the bolt130when the housing105is rotated.

The lock channel150extends into the housing105. The central longitudinal axis, l2, of the lock channel150and the central longitudinal axis, l1, of the bolt channel110are in planar alignment. The lock channel150has an open end151and an inner end152, which is opposite the open end151of the lock channel150, is within the housing105and intersects the bolt channel110between the open end111of the bolt channel110and the closed end112of the bolt channel110.

In the exemplary embodiment, the lock channel150has a circular cross-section shape, with a diameter, d9, that is at least as great as the diameter, d5, of the tubular cylindrical outer sleeve155of the lock200. In the exemplary embodiment, the length, d4, of the outer sleeve155of the lock200is greater than the length, d10, of the lock channel150, measured from the open end151to the intersection. The difference between the length, d4, of the outer sleeve155of the lock200and the length, d10, of the lock channel150, is the distance by which the outer sleeve155of the lock200extends into the bolt channel110. This difference is less than the distance between the shank131of the bolt130and the intersection at the inner end152of the lock channel150. Thus, the end208of the outer sleeve155of the lock200is in proximity to, but does not reach the shank131of the bolt130, when the lock200is fully inserted in the lock channel150. The end208of the outer sleeve155of the lock200, which protrudes into the space between the shank131and the intersection at the inner end152of the lock channel150, prevents withdrawal of the engageable element (e.g., head)140of the bolt130in the bolt channel110.

The housing105includes a channel or cavity162aligned with the locking aperture160. The locking element210extends through the locking aperture160in the sleeve155into the cavity162when the locking element210is in the extended position. The cavity162may be an annular cavity undercut or otherwise formed in the lock channel150during manufacturing. The annular cavity may extend for 360° (i.e., entirely around the lock channel150), or for less than 360°, such as 180° (i.e., half way around the lock channel150) or 90° (¼ way around the lock channel150). In the illustrated embodiment, the cavity extends for less than 360°, and thus does not form a complete annulus or ring around the lock channel150. The cavity162receives the locking element210when the locking element210is in an extended position, and the lock200is in the locked position.

FIG.12is a perspective section view (section B-B) of an exemplary anti-tampering device100according to principles of the invention. In this view, the cavity162is apparent. The cavity162is below the intersection of the lock channel150and the bolt channel110, and above the threaded channel115for the key (set screw)165.

FIG.8is substantially similar toFIG.7, except that the embodiment ofFIG.8omits the annular cavity162. Instead, the embodiment ofFIG.8includes a cylindrical cavity163bored from the back side108of the housing105to the lock channel150, at a point at which the locking element210may be received when the locking element is in an extended position, and the lock200is in the locked position.

The exploded perspective view ofFIG.9shows the bolt130and jam nut135removed from the bolt channel110. The key (set screw)165is removed from the threaded channel115. The outer sleeve155is removed from the lock channel150. The outer sleeve155can be removed from the lock channel150when the key (set screw)165is backed off from the keyseat (guide)170. Backing off and removal of the key165requires access to the back side108of the housing105.

FIGS.10and11provide perspective views of the exemplary lock assembly200in unlocked and locked configurations. In the locked configuration, the locking element210is in an extended position, extending through the aperture160of the sleeve155. In the unlocked configuration, the locking element210is in a retracted position and does not extend through the aperture160of the sleeve155. The lock200includes an outer end205and an inner end208opposite the outer end205. Locking and unlocking are achieved in a conventional manner by inserting a lock key215in a slot in the outer end205of the lock200and turning the lock key215clockwise or counterclockwise.

While an exemplary embodiment of the invention has been described, it should be apparent that modifications and variations thereto are possible, all of which fall within the true spirit and scope of the invention. With respect to the above description then, it is to be realized that the optimum relationships for the components and steps of the invention, including variations in order, form, content, function and manner of operation, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention. The above description and drawings are illustrative of modifications that can be made without departing from the present invention, the scope of which is to be limited only by the following claims. Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents are intended to fall within the scope of the invention as claimed.