Abstract: A locking mechanism on a container (1) or a holding device (28), having two interlockable parts (33, 21, 26), wherein one part (2, 21) forms an interlocking recess (9) and the mating part (3, 26) an interlocking tongue (6). In the opening path of the interlocking tongue, a blocking element (8) is provided, as a result of which the interlocking tongue (6) can only be set to the opening position after removing the blocking element by means of a suitable tool.

Abstract: A mechanical fuse is used with ergonomic devices for seats such as automobile seats to allow the ergonomic devices to tolerate abusive loads without breaking a linkage, such as a traction cable, used to move the ergonomic supports. The traction cable is comprised of a sleeve with a wire disposed to slide axially through the sleeve. The mechanical fuse is installed with the sleeve divided into two sections, with an end of each section seated into a male component or a female component of the mechanical fuse. The male and female components of the mechanical fuse slide axially relative to one another but are restrained from sliding by insertion of a boss on one component into a detent on the other component. The boss and detent hold the male and female components together in a friction fit that resists axial movement. When an abusive force is applied to the fuse, the friction fit of the boss and detent is overcome so that the boss slides out of the detent in a radial direction.

Abstract: The invention involves a seat system with a movable and immovable portions that may be maintained and still operate during transients as required under the federal regulations. There is a quick release serviceability latch for a school bus passenger seat with integrated restraints. The inner and outer seat backs must be quickly detached from one another to facilitate repair or replacement of damaged seat components. A movable plunger is rigidly attached to the inner seat back frame. Another bracket with hole to accept the plunger is rigidly attached to the back pan of the outer back. The attachment of inner to outer seat backs must be strong enough so that they can't be pulled apart by hand but at the same time be detachable in the event of a crash. A tab that engages the plunger separates upon a rapid deceleration event.

Abstract: A collision safety device having a breakaway coupling. The collision safety device comprises first and second post segments. A first shear plate is attached to the first post segment and a second shear plate is attached to the second post segment. The first shear plate has a first contact surface and the second shear plate has a second contact surface opposite the first contact surface. The first and second shear plates are releasably attached by a breakaway coupling including a band. Friction between the shear plates and strength of the band are adjustable such that the upper post is released from the lower post when subjected to a pre-selected collision force.

Abstract: A frangible coupling for interconnecting parts comprising a first ring and a second ring coaxially arranged relative to each other and axially joined via an annular array of fuse ligaments equidistantly spaced apart from each other. The ligaments are configured to fail when an abnormal radial load of a predetermined value causes the first and second ring to move out of their coaxial relationship. When all of the fuse ligaments are severed, the communication between the first and second rings is severed. This allows the first ring to move independently of the second ring, preventing the out of balance load on the first ring being communicated to the second ring.

Abstract: This invention relates to windshield wiper system and method which utilizes a flexible member to account for compression loads in excess of a predetermined load, such as 30 percent, greater than a maximum load for the flexible member. The system utilizes a flexible pultruded composite material having a relatively low modulus of elasticity, yet relatively high elongation characteristics. The flexible arm bends to facilitate preventing damage to components in the wiper system when a compressive load applied to the flexible member is in excess of the predetermined load.

Abstract: An apparatus for use in a wellbore, the apparatus comprises a top body, a bottom body, and a sleeve mechanically connected to the top and bottom bodies. The sleeve movable between a first position to a second position, whereby in the first position, the top and bottom bodies rotate as one unit and in the second position, the top body rotates independent of the bottom body in a first direction and with the bottom body in a second direction. A method for completing a wellbore, wherein the method comprises running an assembly and a liner disposed on a drill string into the wellbore. The assembly includes an expander tool, a hydraulically actuated swivel, and a running tool mechanically connected to the liner. The method includes rotating the assembly and the liner as one rotationally locked unit. The method further includes activating the expander tool, expanding the liner into the existing casing, deactivating the expander, and then removing the drill string and running assembly from the wellbore.

Abstract: A mounting plate (16) pivotally supports a finger (14) for pivotal movement about a pivot axis A as a shear pin (34) breaks between a post (30) and the finger (14) in response to a predetermined force urging the finger (14) to pivot about the pivot axis A. A first fastener (24) is disposed under an opening (46) in the finger (14) for removing the mounting plate (16) and the finger (14) together as a unit from the transfer bar (12) while remaining connected by a bolt (36) at the pivot axis A.

Abstract: Tubulation tubing of a display panel includes a flange at one end and a ring-shape adhesive member placed on a display panel to align a vent hole of the display with an opening of the tubulation tubing and the flange of the tubulation tubing is bonded to the display panel via the adhesive member.

Abstract: A breakaway signpost connector for attaching a sign support member to an anchor member. The connector includes a shear member having a first end, a second end, and a necked-down section between the first and second ends. A spring surrounds the shear member and supports the necked-down section.

Abstract: An energy absorbing wiper system for a vehicle, including: a pivot shaft to which a wiper arm is fixed; a pivot shaft holder into which the pivot shaft is rotatably inserted; an impact absorbing portion provided between the pivot shaft and the pivot shaft holder, the impact absorbing portion being adapted to be broken or deformed when a certain load is applied thereto to thereby permit the movement of the pivot shaft in a sinking direction relative to the pivot shaft holder; and, an energy absorbing member interposed between the wiper arm and the pivot shaft holder, the energy absorbing member adapted to be broken or deformed while permitting the sink of the pivot shaft when the pivot shaft moves in the sinking direction after the impact absorbing portion has been broken or deformed, to thereby absorb the moving energy of the pivot shaft.

Abstract: In the aerospace field spacecraft components are held together by separation systems until a specific time when they must be separated or deployed. Customarily a threaded joining bolt engages one of the components to be joined, and a threaded nut is placed on that bolt against the other component so they can be drawn together by a releasable locking assembly. The releasable locking assembly herein includes a plunger having one end coupled to one end of a plunger bolt. The other end is flanged to abut and compress a coil spring when the plunger is advanced toward the interface plane between the two components. When the plunger is so advanced toward the interface plane, the end of the plunger bolt can be connected to the joining bolt. Thus during retraction the joining bolt is drawn to one side of the interface plane by the force of the expanding spring.

Abstract: A breakaway coupling for a light pole or the like is disclosed and is utilized on each of the anchor bolts of the foundation for the pole. Each of the couplings comprises a metal coupling nut which has a plurality of radially spaced-apart and vertically disposed slits formed therein which extend thereinto to create weakened areas or zones in the coupling nut. The coupling nut is embedded in a fiber-reinforced material which provides the necessary hoop strength to the coupling nut. The base plate of the pole is positioned on the upper ends of the coupling nuts and is secured thereto by bolts extending downwardly through the base plate of the pole. If the pole is struck by a vehicle, the fiber-reinforced body members, as well as the coupling nuts, fracture to permit the pole to break away from the foundation. The fiber-reinforced body member of the coupling not only adds hoop strength to the coupling nut, but prevents the metal coupling nut from being exposed to corrosive elements such as salt or the like.

Abstract: A wiper pivot for a wiper apparatus of motor vehicles, which is provided with a pivot holder 3 having a shaft-holding portion 3b to rotatably support a pivot shaft 2, and a body-fixing portion 3d to be fixed to the vehicle body and formed in one body of resin together with the shaft-holding portion 3b through a connecting portion 3c, and the connecting portion 3c is further provided with a thin-walled destructible portion 4 to be destroyed at the time when impulsive force exceeding the predetermined value is applied on the pivot shaft 2.

Abstract: An axially collapsible propeller shaft assembly, wherein the axial collapse feature resides in an axially collapsible drive connection between a stud shaft and a hollow propeller shaft, wherein under everyday drivingly conditions the drive connection provides torque transfer between the stud shaft and the propeller shaft, but under crash conditions the axial force telescopically receives the stud shaft into the hollow space of the propeller shaft. In a first embodiment, an end of the stud shaft is splinably engaged with an end cap affixed to the propeller shaft. In a second embodiment, a stud shaft is affixed to an end cap, which is, in turn, affixed to a propeller shaft. An annular score of the end cap has a bottom which is broken in a crash, which allows a central portion of the end cap to move with the stud shaft into the propeller shaft.

Abstract: A rail (100, 100?) is formed with ends (102, 104) configured so that they can be placed together and mounted to the post (P) of a fencing system. A breakaway feature (122, 124, 126) permits the rail to break free of the post (P) when a threshold level of force is applied to the rail. Two adapters (200) can be attached to a stock rail (R) to form a breakaway rail.

Abstract: A motor bracket is attached at one end of a vehicle body so as to be able to slide, and is fixed at the other end to the vehicle body. And weak points are provided in the vicinity of a motor bracket fixing section. Weak points are also provided in the vicinity of a first fixing section of a first pivot holder. On the other hand, weak points are also provided in the vicinity of a second fixing section of a second pivot holder. Since the motor bracket slides and becomes detachable if the weak points are ruptured, it is possible to absorb an impact at the wiper motor. Since the first and second pivot holders are also detached if the weak points and weak points are ruptured, it is possible to improve the overall impact absorbing performance of the vehicle wiper assembly.

Abstract: Connecting device for masts, poles and similar carrying structures which are mounted on a base at a roadway, wherein the upper end of the base and the lower end of the pole structure each carries or is integrated with a mounting plate and provide an angle with the axis of the pole structure, which have holes for at least one connecting member maintaining the two mounting plates together in an operating relationship. The connecting member is adapted to lose integrity or fracture upon a sideways impact over a certain level, such as at the impact of a motor vehicle. The connecting devices includes at least one pressure member for providing pressure load between the mounting plates and for keeping them apart at a predetermined distance. Further, the connecting member includes at least one shear member primarily for taking shear load, and at least one tension member to provide a tension load between the mounting plates. The load on the pressure member is provided by the tension member and/or the pressure member.

Abstract: A coating head assembly incorporating a replaceable breakaway link. The breakaway link connects two portions of the coating head assembly and has a sharp bend defining a weakened portion. In the event of a collision, the breakaway link will break to reduce the likelihood of breakage of any other part of the coating head assembly. Repair then only requires that the link be replaced, rather than the coating head assembly to be rebuilt. This invention reduces the coating head repair time from a fifteen-hour job of rebuilding the coating head assembly to a three-hour job of tooling a new link.

Abstract: Disclosed is a computer-aided product designing assistant apparatus and method for assisting designing of an environmentally conscious product by presenting at least one design guideline to be adopted in designing the environmental conscious product.

Abstract: A wiper pivot for a wiper apparatus of motor vehicles, which is provided with a pivot holder 3 having a shaft-holding portion 3b to rotatably support a pivot shaft 2, and a body-fixing portion 3d to be fixed to the vehicle body and formed in one body of resin together with the shaft-holding portion 3b through a connecting portion 3c, and the connecting portion 3c is further provided with a thin-walled destructible portion 4 to be destroyed at the time when impulsive force exceeding the predetermined value is applied on the pivot shaft 2.

Abstract: A cutting disc core for a circular shaped saw blade which has a circular shaped body which has a center hole and a circular peripheral edge upon which is to be mounted a plurality of spaced apart cutting segments that is to perform the cutting of the saw blade. Surrounding the center hole and formed within the body are a plurality of slits with there being a solid tab that is integrally connected to the body located between each directly adjacent pair of slits. The tab constitutes a frangible seal with the circular ring or bushing which is formed about the center hole to be removable by being forcibly physically separated from the body.

Abstract: The retaining device (110) designed to retain a portion (59) of a part connection device (52), said portion (59) of the connection device (52) being released during failure of said connection device (52), comprises:

Abstract: An improved spool assembly for non-explosive actuators used in electro-mechanical structural separation devices. The spool assembly includes two spool halves each having external surfaces and a generally flat internal surface, a unitary and integral internal member made of an electrically conductive material and having a link-wire portion and two electrical terminal portions, and an external wrap-wire wound around the two spool halves and having a connecting end connected to the link-wire portion of the unitary and integral internal member such that the wrap-wire tightly binds the two spool halves together to form a spool for retaining an external structural member.

Abstract: A cable release anchor having an improved breakaway post design with a cable release feature. The cable release anchor includes upper and lower anchor portions that are readily separable from one another during an impact. A bearing plate is retained within the end of each of the upper and lower anchor portions, and each bearing plate has a bearing surface that is oriented at an acute angle with the vertical when installed in the ground. Each of these bearing plates contains a U-shaped cutout. When the upper and lower anchor portions are joined, the cutouts form an opening through which an end of the tension cable is disposed. An impact to the upper anchor portion readily releases the upper post section from the lower post section and frees the cable. The cable release anchor provides positive anchorage to react to tensile loads on a rail member to redirect a vehicle impacting along the length of the terminal or guardrail.

Abstract: A sliding fastening for a plastics material part having at least one thin wall that is to be slidably fastened to a support via its thin wall, the part including in said thin wall an elongate opening having two longitudinal edges that are substantially parallel at least over a portion of their length, the fastening comprising a spacer that is separate from the part, that is thicker than the thickness of the thin wall, and that is suitable for sliding in the opening between the two longitudinal edges thereof, a cover completely covering the spacer, being larger than the opening so as to be incapable of passing through it in order to hold the thin wall in register with the thickness of the spacer, and a base for securing to the support. In the fastening the spacer and the base are united by frangible links.

Abstract: A wiper pivot for a wiper apparatus of motor vehicles, which is provided with a pivot holder 3 having a shaft-holding portion 3b to rotatably support a pivot shaft 2, and a body-fixing portion 3d to be fixed to the vehicle body and formed in one body of resin together with the shaft-holding portion 3b through a connecting portion 3c, and the connecting portion 3c is further provided with a thin-walled destructible portion 4 to be destroyed at the time when impulsive force exceeding the predetermined value is applied on the pivot shaft 2.

Abstract: A disc cutterbar having a mounting hub supporting a knife for severing standing crop material, with a reversible shearable spline area engaged with a drive shaft to form a shear device therebetween.

Abstract: A wiper apparatus for a vehicle windshield is fixedly connected by at least one mount to vehicle structure. A portion of the wiper apparatus extends exteriorly of an impact line defined by the vehicle structure. A frangible portion is formed in a mount. An energy focus member is carried on vehicle structure subject to movement during a collision and has position relative to the fracture portion of the mount so as separate the mount from the vehicle structure to allow an exterior portion of the wiper apparatus to drop below a vehicle impact line before substantial contact with a pedestrian.

Abstract: This invention relates to windshield wiper system and method which utilizes a flexible member to account for compression loads in excess of a predetermined load, such as 30 percent, greater than a maximum load for the flexible member. The system utilizes a flexible pultruded composite material having a relatively low modulus of elasticity, yet relatively high elongation characteristics. The flexible arm bends to facilitate preventing damage to components in the wiper system when a compressive load applied to the flexible member is in excess of the predetermined load.

Abstract: This invention relates to windshield wiper system and method which utilizes a flexible member to account for compression loads in excess of a predetermined load, such as 30 percent, greater than a maximum load for the flexible member. The system utilizes a flexible pultruded composite material having a relatively low modulus of elasticity, yet relatively high elongation characteristics. The flexible arm bends to facilitate preventing damage to components in the wiper system when a compressive load applied to the flexible member is in excess of the predetermined load.

Abstract: A drive assembly, especially for agricultural implements with rotatingly driven masses, has a shear pin coupling (1) with a coupling hub (3) and a coupling sleeve (12) rotatable relative to the coupling hub (3). A ratchet gear (20) supported on the coupling hub (3) and rotatable relative to the coupling hub (3) and the coupling sleeve (12). All three components (3, 12, 20) are connected to one another by the head screw (26) constituting the shear pin. A ratchet (not illustrated) may engage a holding face of the ratchet gear (20). This results in the head screw (26) being sheared. As a result, the coupling sleeve (12) is disconnected from the coupling hub (3) in respect of drive.

Abstract: A ball socket for connection with a wall or plate type structure resists accidental pull-out therefrom. The ball socket includes a socket cup for retaining a ball stud. Snap locks extend from the ball socket to provide a mechanical connection with the structure. A sleeve located initially in the socket cup is driven between the snap locks as the ball stud is placed in the socket cup. This prevents the snap locks from moving in a manner that allows the ball socket to be accidentally pulled from the structure. The structure may be a wall in a headlamp assembly.

Abstract: An anchorage for a post-tension system including an anchor body having an interior cavity and a generally flat end surface, a tendon extending through the interior cavity of the anchor body, a plurality of wedges in interference-fit relationship between a wall of the interior cavity and a surface of the tendon, a cap member positioned outwardly of the flat end surface, and a ring juxtaposed against the inner surface of the cap member. The ring is physically deformed so as to provide a visual indication of a desired amount of tension applied to the tendon. The ring is received within an annular slot formed in the flat end surface of the anchor body.

Abstract: This invention relates to windshield wiper system and method which utilizes a flexible member to account for compression loads in excess of a predetermined load, such as 30 percent, greater than a maximum load for the flexible member. The system utilizes a flexible pultruded composite material having a relatively low modulus of elasticity, yet relatively high elongation characteristics. The flexible arm bends to facilitate preventing damage to components in the wiper system when a compressive load applied to the flexible member Is in excess of the predetermined load.

Abstract: A re-attachable breakaway safety connector is disclosed which is adapted for use with a rope or other objects arranged in at least a substantially linear manner such that when force is provided to the objects, a tensile force is transferred to the connector. The breakaway connector is designed to fail, i.e., the components separate, when the tensile force transferred to the connector exceeds a predetermined level, and may be selectively adjusted to reduce the amount of force required to separate a male and female component of the safety connector.

Abstract: A connector assembly for mounting turbomachinery including a link connector to be coupled to a clevis. The clevis includes a pair of arms and an opening that extends therethrough. The link connector includes a first end that includes an elastomer portion that defines an opening. The connector assembly further includes a support washer having an opening extending therethrough adjacent the link connector elastomer portion, and a fastener inserted through the clevis opening, the support washer opening, and the link connector elastomer opening to couple the link connector and the support washer to the clevis such that the link connector is coupled between the clevis arms by the fastener, and such that the support washer thermally insulates at least a portion of the link connector elastomer portion.

Abstract: A gate opening device for shifting a gate from a closed position to an open position on loss of power to a motive device includes a housing, the motive device carried by the housing, and a drive shaft coupled to and rotatable by the motive device. A drive member is coupled to the drive shaft and capable of being connected to a gate for causing shifting movement thereof. A base plate is coupled to the drive shaft and a drive plate is coupled to the drive member and pivotally coupled to the base plate. A shear pin engages the drive plate and the base plate, preventing relative pivoting thereof. The shear pin is formed of a material which allows a shearing effect on a specified torque or force, causing the shear pin to break or shear and allow relative pivotal movement of the drive plate and the base plate.

Abstract: A breakaway post base includes a pair of adjacent slip plates to allow separation of the upper portion of a traffic sign or the like from its permanently mounted base. The two plates are triangular with notches at their apices, with the plates and related structure secured together by bolts through the apex notches. An impact on the upper post dislodges the bolts, allowing the upper post to move freely and preventing significant damage to the sign structure. At least one of the slip base plates includes a sleeve extending therefrom, into which one end of the post is installed. The post is prevented from rotating relative to the slip base by a series of set screws installed through the slip base sleeve and locking the post immovably therein. Thus, a sign supported by the present assembly cannot rotate relative to the slip base plate.

Abstract: A handle is provided for an operator that provides overtorque protection for the operator. The handle includes a hand grip connected to a connecting shaft, which is mateably received in the operator. The connecting shaft includes at least one weakened section which breaks or fractures in the event an excessive amount of torque or force is applied to the handle. As a result, the handle breaks when the user applies an excessive amount of torque to the handle in an effort to open or close the structure connected to the operator. The broken handle may be easily replaced by removing the broken section of the connecting shaft from the operator and replacing the handle by inserting the new handle with a new connecting shaft into the operator. The gear mechanism disposed within the escutcheon of the operator is protected from the excessive amount of torque or force and, accordingly, the handle is intended to break before the operator which avoids the need for replacing the entire operator.

Abstract: A coupling device has a pulley that receives rotational torque from an engine. The torque is transmitted to a shaft through a hub and a one-way clutch. A torque limiter is screwed on the shaft to fasten the inner ring of the one-way clutch onto the shaft. The torque limiter has a breakable portion. The torque is directly transmitted from the inner ring to the shaft when the torque is normal. If the torque exceeds the tightening torque of the torque limiter, the inner ring begins to slide and rotate, and drives the torque limiter in a tightening direction. As the torque limiter is tightened additionally, the tensile stress on the breakable portion is increased. Then, the breakable portion breaks and is separated in axial direction so that the coupling device disconnects torque transmission.

Abstract: A coating head assembly incorporates a replaceable breakaway link into the coating head assembly. In the event of a collision, this link will break to reduce the likelihood of breakage of any other part of the coating head assembly. Repair then only requires that the link be replaced, rather than the coating head assembly be rebuilt. This invention reduces the coating head repair time from a fifteen-hour job of rebuilding the coating head assembly to a three-hour job of tooling a new link.

Abstract: An internally threaded (23) collet nut (22) is placed onto the first cable (12) and a first cable (12) is inserted into a collapsible collet (20) on a connector body (18). The collet nut (22) and a breakaway nut (30) are engaged with simple wrenches to establish a reactive torque between the collet nut (22) and the breakaway nut (34) to break away the breakaway nut (34) from the connector body. An enlarged end (16) of the second cable (14) is placed into the interior of a retainer nut (30), which is threaded onto the threaded section (19) of the connector body (18) to abut the collet nut (22), thereby connecting the two cables (12 and 14).

Abstract: A wiper apparatus for a motor vehicle comprising a sleeve secured to a vehicle body side and a pivot shaft which is supported rotatably in the sleeve. The proximal portion of the pivot shaft relative to the interior side of the vehicle is connected to a drive source. The tip portion of the pivot shaft holds a wiper arm on the exterior side of the vehicle. For the pivot shaft to depress toward the vehicle's interior side with respect to the sleeve, a load exceeding a predetermined value works axially on the pivot shaft from the vehicle's exterior side. A depression preventing member is interposed between the pivot shaft and the sleeve and is deformed when receiving the load that depresses the pivot shaft. A deformation space is secured between the pivot shaft and the sleeve enabling the depression preventing member to deform smoothly in response to the load.

Abstract: The invention concerns a device for the embrittlement of a motor vehicle pedal pivot pin, characterized in that the pin comprises at least a starting point of fracture and reinforcing means arranged at the starting point of fracture for increasing the pin resistance, the reinforcing means being capable of moving by action of motoring means to be positioned at some distance from the starting point of fracture thereby ensuring that the pin is embrittled.

Abstract: An energy absorbing wiper system for a vehicle, including: a pivot shaft to which a wiper arm is fixed; a pivot shaft holder into which the pivot shaft is rotatably inserted; an impact absorbing portion provided between the pivot shaft and the pivot shaft holder, the impact absorbing portion being adapted to be broken or deformed when a certain load is applied thereto to thereby permit the movement of the pivot shaft in a sinking direction relative to the pivot shaft holder; and, an energy absorbing member interposed between the wiper arm and the pivot shaft holder, the energy absorbing member adapted to be broken or deformed while permitting the sink of the pivot shaft when the pivot shaft moves in the sinking direction after the impact absorbing portion has been broken or deformed, to thereby absorb the moving energy of the pivot shaft.

Abstract: The invention is a wiper arm (20) for securement to a drive shaft (10,12). The wiper arm (20) has a securing part (18), which on one end has a bearing point (16) by way of which the wiper arm can be connected, in a manner fixed against relative rotation, to the drive shaft (10, 12) via a nut (14). The nut can be screwed onto the drive shaft (10,12). The nut is formed by a component integrally cast onto the securing part (18) and is connected to the securing part (18) via a binding (26) that can be released upon installation of the wiper arm (20).

Abstract: A breakaway joint for releasably connecting a first component to a second component, comprises a first member to which the first component is attached; a second member to which the second component is attached; a plurality of columnar members each having first and second ends, the first ends being coupled to the first member; and a mechanism engaged by both the second member and the second ends of the columnar members for latching the first member to the second member and for converting a tensile load acting between the first and second members into a compressive load acting on the columnar members; wherein when the tensile load reaches a predetermined level, the columnar members will buckle and the latching means will release the first member from the second member.

Abstract: A breakaway coupling for a support structure having a first post and a second post, where the breakaway coupling has a first plate coupled to the first post, a second plate coupled to the second post and breakably coupled to the first plate, and a bearing positioned between the first plate and the second plate having a bearing member located in an opening of the bearing housing and contacting at least one of the first and second plates.

Abstract: A lift truck attachment for handling loads comprises a main frame assembly for attachment to an elevator of a lift truck and a lower slide assembly. The lower slide assembly includes an elongated sliding element for performing a reciprocal motion relative to the main frame assembly. A bottom slide cross tube is furnished and has an elongated structure extending substantially perpendicular to the elongated sliding element. An elongated pusher plate is attached to the bottom slide cross tube and extends substantially parallel to the elongated sliding element. A first shear plate has a first hole and is attached to an end of the bottom side cross tube. A second shear plate has a second hole and is rotatably attached to the first shear plate with a rotation axis disposed substantially parallel to the elongated sliding element. The first hole and the second hole have the same distance from the rotation axis. A threaded safety bolt penetrates through the first hole and through the second hole.