Patent Description:
The force that pushes the pin head back into the detent is resultant from lateral forces between parts and thus between the pin head and the detent. The pin head and/or the detent can have surfaces that are angled relative to the axis of the bore and that effectively function as an inclined plane, such that lateral forces result in an axial force on the pin head. The amount of lateral forces required to cause the pin head to retract into the bore can be controlled by either changing the outward bias of the pin head or by changing the angle of the inclined plane. A lower outward bias results in a lower lateral force required to depress the pin head. Similarly, a lower angle of the inclined plane results in a lower lateral force required to depress the pin head. Because the pin head is spherical, the angled surface that interacts with the detent varies depending on the relative depth of the detent. Near the axial end of the pin head the surface is shallow, whereas towards the lateral side of the pin head the angle is steep. Thus, a shallow detent will result in a higher axial force compared to a deeper detent for a given lateral force.

The amount of force required to depress the pin head is limited in practice. If the bias is too high, friction between the pin head and the second part may prevent the parts from moving relative to one another even when the pin head is not in the detent. If the angle is too steep, then the lateral force required to depress the pin head might exceed the shear strength of the parts. Thus, a detent pin is limited in how securely it can hold one part relative to another part. In some instances, a separate mechanism may be required to restrain or position a part in addition to the detent pin.

<CIT> discloses that a boss of one end of a wing is supported to a wing support shaft by the boss of the body of a shell. The other end of the wing is clamped at the body by a shear pin type constraint bolt. A command signal is sent to a flying shell while constraint rotating to explode its explosive to break the threaded part of the bolt, thereby releasing the constraint of the wing.

In a first aspect, the present disclosure provides a frangible detent pin according to independent claim <NUM>.

In a second aspect, the present disclosure provides a system according to independent claim <NUM>.

In a third aspect, the present disclosure provides a method according to independent claim <NUM>.

Features and advantages of the invention will be apparent from the detailed description which follows, taken in conjunction with the accompanying drawings, which together illustrate, by way of example, features of the invention; and, wherein,.

Reference will now be made to the examples illustrated, and specific language will be used herein to describe the same.

An initial overview of the inventive concepts is provided below, and then specific examples are described in further detail later. This initial summary is intended to aid readers in understanding the examples more quickly but is not intended to identify key features or essential features of the examples, nor is it intended to limit the scope of the claimed subject matter.

In one example, disclosed is a frangible detent pin. The frangible detent pin comprises a base, a pin head, and an elastic member. The base is configured to be secured within a bore. The pin head and the base are interconnected through a frangible connection. The elastic member is configured to bias the pin head away from the base. The frangible detent pin has a rigid stage in which the pin head is rigidly positioned relative to the base and a spring-loaded stage in which the pin head is moveable relative to the base under a compression load between pin head and the base. The frangible detent pin is configured to transition from the rigid stage to the spring-loaded stage in response to the compression load exceeding a predetermined threshold sufficient to cause the frangible connection to fail.

In accordance with a more detailed aspect, the base can comprise an outer portion and an inner portion and the frangible connection can be defined by a connection between the outer portion and the inner portion configured to fail upon the compression load exceeding the predetermined threshold.

In accordance with a more detailed aspect, the outer portion can comprise a socket and the inner portion cam comprises a shaft. The shaft can be configured to displace into the socket upon the failure of the frangible connection (e.g., in one example, the breaking or fracture of the frangible connection). In accordance with a more detailed aspect, the shaft can comprise a radial ridge having an external diameter greater than an internal diameter of the socket.

In accordance with a more detailed aspect, the pin head can have a first portion and a second portion with an annular shoulder between the first portion and the second portion, and the first portion can comprise a hemispherical shape and the second portion can comprise a cylindrical shape.

Also disclosed is a system for securing a movable member. The system comprises a first member, a second member, and a frangible detent pin. The first member has a bore. The second member is moveably secured to the first member and has a first detent for securing the second member in a first configuration and a second detent for securing the second member in a second configuration. The frangible detent pin comprises a base secured within the bore, a pin head positioned at least partially within the bore and interconnected with the base through a frangible connection, and an elastic member configured to bias the pin head away from the base. The frangible detent pin has a rigid stage in which the pin head is rigidly positioned relative to the base and a spring-loaded stage in which the pin head is moveable relative to the base under a compression load, and the frangible detent pin changes or transitions from the rigid stage to the spring-loaded stage in response to a compression load exceeding a predetermined threshold sufficient to cause the frangible connection to fail.

In accordance with a more detailed aspect, the first member and the second member can be configured to position the bore adjacent the first detent with the system in a first configuration with the frangible detent pin in the rigid stage, such that the pin head extends into the first detent to secure the second member relative to the first member, and a second configuration with the frangible detent pin in the spring-loaded stage, such that the pin head extends into the second detent to secure the second member relative to the first member.

In accordance with a more detailed aspect, the pin head can comprise a hemispherical shaped end and the first detent can comprise a semi-hemispherical surface, and the second detent can comprise a semi-hemispherical surface. However, this is not intended to be limiting in any way as the pin head, and the detents in which these are inserted, can comprise other shapes and configurations other than hemispherical, such as flat, cone-shaped, dog point configuration, cup shaped and other shapes/configurations.

In accordance with a more detailed aspect, the first detent can comprise a shallow detent and the second detent can comprise a deep detent.

In accordance with a more detailed aspect, the shallow detent can be configured to apply a compressive load to the frangible detent pin to cause the frangible connection to fail.

In accordance with a more detailed aspect, the first and second members can be configured to rotate relative to one another.

In accordance with a more detailed aspect, the first and second members can be configured to translate relative to one another.

In accordance with a more detailed aspect, the system can further comprise a shear pin extending into the bore adjacent the pin head. The shear pin can be configured to define the frangible connection and to shear when the compressive load exceeds the predetermined threshold.

In accordance with another aspect, the first member can comprise a missile and the second member can comprise a missile fin.

In accordance with another aspect, the second member can rotate about a first axis relative to the first member and the bore can have a second axis perpendicular to the first axis.

Also disclosed is a method for configuring a frangible detent pin. forming a frangible detent pin to comprise a base configured to be secured within a bore, a pin head, wherein the pin head and the base are interconnected through a frangible connection, and an elastic member configured to bias the pin head away from the base. The frangible detent pin has a rigid stage in which the pin head is rigidly positioned relative to the base and a spring-loaded stage in which the pin head is moveable relative to the base under a compression load between pin head and the base, and the frangible detent pin is configured to transition from the rigid stage to the spring-loaded stage in response to the compression load exceeding a predetermined threshold sufficient to cause the frangible connection to fail.

In accordance with a more detailed aspect, the base can be formed to comprise an outer portion and an inner portion, and the frangible connection can be defined by a connection between the outer portion and the inner portion configured to break upon the compression load exceeding the predetermined threshold.

In accordance with a more detailed aspect, the outer portion can be formed to comprise a socket and the inner portion can be formed to comprise a shaft, and the shaft can be configured to displace into the socket upon the failure of the frangible connection.

In accordance with a more detailed aspect, the shaft can be formed to comprise a radial ridge having an external diameter greater than an internal diameter of the socket.

In accordance with a more detailed aspect, the pin head can be formed to have a first portion and a second portion with an annular shoulder between the first portion and the second portion, wherein the first portion comprises a hemispherical shape and the second portion comprises a cylindrical shape.

To further describe the present technology, examples are now provided with reference to the figures. <FIG> describe an example system in the form of a missile or missile system <NUM> having a detent system <NUM> for securing a moveable member, in this example a deployable fin of the missile system <NUM>. Although the system shown comprises a missile system, this is not intended to be limiting in any way. Indeed, the system can comprise any type of vehicle, object, structure, mechanism, or a combination of these where it is desired to secure a moveable member in one or more positions.

The missile <NUM> is shown as comprising a plurality of deployable fin (e.g., see deployable fin <NUM>) that extend laterally from the body of the missile <NUM> and that function to stabilize and/or guide the missile <NUM> in flight. With the detent system <NUM>, the fins can be positioned in a first configuration in which the fins are stowed (i.e., are not deployed) and do not extend outward from the missile body in order to facilitate packaging and transportation of the missile <NUM>. The fins can be rotatably coupled to the missile body, and designed to rotate from the first configuration to a second configuration where the fins are extended and positioned in a deployed position for flight. The fins can be configured to remain in the first configuration until the missile <NUM> is fired, at which time the fins are deployed and positioned in the second configuration. The fins can transition from the first configuration to the second configuration as a result of a one-time, large external force. For example, an explosive charge may be used to force the fins from the first configuration when the missile <NUM> is fired. As will be shown in <FIG>, a frangible detent pin, as part of the detent system <NUM>, can be used to position and secure a respective one of the fins in each of the first and second configurations while enabling the fins to transition between the first and second configurations. The frangible detent pin can hold the fins securely without the use of any secondary mechanisms, such as a clip or other retainer, while still allowing the fins to rotate between the first configuration and the second configuration. Additionally, the frangible detent pin can have the same overall dimensions as a conventional detent pin enabling the frangible detent pin to easily be substituted for a conventional detent pin.

<FIG> illustrates an example of a missile or missile system <NUM> that uses a detent system <NUM> for securing a moveable member, in this case a fin <NUM>, which comprises one of the fins of the missile system <NUM>, using a frangible detent pin. The missile system <NUM> includes a missile body <NUM>, the missile fin <NUM>, and the detent system <NUM> for securing the moveable member. Although a single missile fin <NUM> is shown in <FIG>, one of ordinary skill in the art will recognize that additional missile fins can be used and that each missile fin can have a detent system for securing the respective one of the missile fins similar to the detent system <NUM> disclosed for the missile fin <NUM>. The configuration shown in <FIG> with the fin <NUM> in the stowed configuration can be used to store and transport the missile <NUM>.

<FIG> illustrates the missile <NUM> with the detent system <NUM> facilitating the missile fin <NUM> to be in a partially deployed position, such that the missile fin <NUM> is not in a fixed position but is free to move relative to the missile body <NUM> between the first and second available configurations or positions.

<FIG> illustrates the missile <NUM> with the detent system <NUM> securing the missile fin <NUM> in the second position, in this case the fully deployed configuration. As will be shown in <FIG> and discussed below, the detent system <NUM> comprises a frangible detent pin configured to maintain the missile fin <NUM> in the first configuration shown in <FIG> and the second configuration shown in <FIG>, and to facilitate the transition between these configurations.

With reference to <FIG>, the example detent system <NUM> can be configured to secure the moveable member (e.g., the fin <NUM>) relative to another structural component (e.g., a structural component of or coupled to the missile body <NUM> in the example missile system <NUM>), and to facilitate the transition of the moveable member between one or more positions or configurations. The detent system <NUM> can comprise a first member <NUM>, a second member <NUM>, these being moveable relative to one another, and a frangible detent pin <NUM>. The first member <NUM> can comprise a structural member part of or rigidly coupled to the system. In the example shown, the first member <NUM> can comprise a fin mount coupled to and supported by the missile body <NUM> using conventional techniques. The second member <NUM> can comprise the moveable member, in this example the missile fin <NUM>, which rotatably couples to the fin mount. However, in other examples the structures may be reversed, with the first member corresponding to the missile fin <NUM> and the second member corresponding to the (e.g., the fin mount) being rigidly coupled to or part of the missile body <NUM>.

As discussed, the detent system <NUM> can position the second member <NUM> in the first configuration, such as the position or configuration as shown in <FIG>. The second member <NUM> can be rotatably secured to the first member <NUM> by a rotary coupling <NUM>. For example, the second member <NUM> can have a bore <NUM> and the first member <NUM> can comprise a cross shaft <NUM> located in the bore <NUM>. Thus, the second member <NUM> can rotate about the cross shaft <NUM> of the first member <NUM>. The first member <NUM> can have a bore <NUM> housing the frangible detent pin <NUM>. The bore <NUM> can have an axis that is perpendicular to a direction of travel of the second member <NUM> and be located at an interface between the first member <NUM> and the second member <NUM>. For example, in rotating systems the axis of the bore <NUM> can be perpendicular to the axis of rotation (the axis into the page as shown) defined by the cross shaft <NUM> about which the second member <NUM> rotates. Or, in translating systems the bore can be perpendicular to an axis of translation.

The detent system <NUM> can further comprise one or more detents or discrete positioning features or members formed in or supported on at least one of the first or second members <NUM>, <NUM>. In the example shown, the second member <NUM> can comprise a first detent <NUM> for securing the second member <NUM> in a first configuration relative to the first member <NUM> (i.e., the configuration shown in <FIG>) and a second detent <NUM> for securing the second member <NUM> in a second configuration relative to the first member <NUM> (i.e., the configuration shown in <FIG>). Each of the detents <NUM>, <NUM> can be defined by and formed in or supported on a surface or portion of structure of one or both of the first or second members <NUM> and <NUM> that is configured to receive and retain a pin head of the frangible detent pin <NUM> of the detent system <NUM> in a fixed location. The detents can comprise any configuration capable of receiving and retaining the pin head of the frangible detent pin <NUM> in a discrete position. For example, a detent can comprise a protruding ring of material extending above a surface of the structure of the second member <NUM>, or a recess formed in a surface of the structure of the second member <NUM>. In some examples, the detent can comprise a hemispherical shape or a partial hemispherical shape.

The frangible detent pin <NUM> can comprise a base <NUM>, a pin head <NUM>, and an elastic member <NUM> configured to bias the pin head <NUM> away from the base <NUM>. The base <NUM> can be configured to secure the frangible detent pin <NUM> within the bore <NUM> of the first member <NUM> when the frangible detent pin <NUM> is assembled. In some examples, the base <NUM> can have external threads <NUM> and the bore <NUM> can have complementary internal threads to secure the frangible detent pin <NUM> to the first member <NUM> within the bore <NUM> using a threaded connection. The base <NUM> can further include features for receiving a torqueing tool such as a wrench. For example, the base <NUM> can have a socket <NUM> configured to receive a tool (e.g., a hex fastener driver) configured to tighten or loosen the base <NUM> of the frangible detent pin <NUM> within the bore <NUM> of the first member <NUM>.

The pin head <NUM> and the base <NUM> can be directly or indirectly interconnected through a frangible connection or interface, such that the pin head is moveable relative to the base upon the failure of the frangible connection. A frangible connection can be referred to herein as a connection that is designed to fail at a predetermined load, which can be any load based on a particular application or need, or one that is desired. For example, a component may have a thinned section of material between two portions of the component and that is designed to fail when a load exceeds a predetermined threshold. In the example shown, the base <NUM> comprises an outer portion <NUM>, and an inner portion <NUM>, the inner portion <NUM> comprising a smaller diameter than the outer portion <NUM>. The structural interface between the outer portion <NUM> and the inner portion <NUM> can be referred to as an overlapping portion <NUM>, which can define the frangible connection and can be sized and shaped to fail upon an axial compression load between the outer portion <NUM> and the inner portion <NUM> exceeding a predetermined threshold. The predetermined threshold can be adjusted or tuned by varying the configuration of the structural interface or overlapping portion <NUM> between the outer portion <NUM> and the inner portion <NUM>, such as the amount or distance of overlap, the overlap distance DO (see <FIG>), between the inner portion <NUM> and the outer portion <NUM>. For example, an overlap portion <NUM> having a smaller overlap distance DO between the inner and outer portions <NUM>, <NUM> will result in fracture of the frangible detent pin <NUM> at a lower predetermined threshold compared with a higher predetermined threshold that would exist given the overlap portion <NUM> having a larger overlap distance DO (assuming all other parameters are the same). It is noted that the frangible connection can be configured and formed in a variety of ways other than as shown and described herein. For example the frangible connection can be formed and tuned using different materials or material segments, and others as will be recognized by those skilled in the art.

The outer portion <NUM> of the base <NUM> of the frangible detent pin <NUM> can comprise a socket <NUM> and the inner portion <NUM> of the base <NUM> can comprise a shaft <NUM> extending from the outer portion <NUM>. The outer diameter of the shaft <NUM> can be undersized relative to a minimum inner diameter of the socket <NUM> such that the shaft <NUM> of the inner portion <NUM> can be received at least in part within the socket <NUM>, thus forming the overlapping portion <NUM> of the base <NUM>. Thus, after the frangible connection fails, the overall length of the base <NUM> shortens as the shaft <NUM> displaces further into the socket <NUM>. This is described in more detail below, and shown more clearly in <FIG> and <FIG>.

The shaft <NUM> can have a radial ridge <NUM> at its end that has an outer diameter that is greater than the minimum inner diameter of the socket <NUM>, and greater than the diameter of the remaining portion of the shaft <NUM>. Thus, when the frangible connection fails and the shaft <NUM> displaces into the socket <NUM>, the radial ridge <NUM> prevents the shaft <NUM> from escaping the socket <NUM> by interference (i.e., physical contact) between the outer portion <NUM> and the radial ridge <NUM>. This prevents the shaft <NUM> from becoming loose within the missile <NUM> where the loose shaft <NUM> could potentially cause damage to other parts.

The frangible detent pin <NUM> can further comprise a pin head <NUM>. The pin head <NUM> can comprise a first portion <NUM> and a second portion <NUM>. The first portion <NUM> can comprise a cylindrically shaped shaft having a hemispherical shaped end for interacting with (i.e., being received within, contacting or otherwise engaging) a detent. The second portion <NUM> can comprise a cylindrically shaped shaft having a diameter less than that of the shaft of the first portion <NUM>, such that an annular shoulder <NUM> is formed between the first portion <NUM> and the second portion <NUM>.

It is noted herein that the pin head <NUM> frangible detent pin <NUM>, namely the first portion <NUM> of the pin head <NUM>, can comprise any shape or configuration other than hemispherical. Indeed, it is noted that although the present disclosure describes a pin head and associated detents as having a hemispherical shape, such is not intended to be limiting in any way as it is contemplated that the pin head <NUM> of the frangible detent pin <NUM>, and any associated detents into which the pin head is intended to be inserted, can comprise any shape or configuration, such as flat with various angled surfaces, cup shaped, cone shaped, round, dog point configuration, and other shapes/configurations as will be recognized and appreciated by those skilled in the art.

The frangible detent pin <NUM> can further comprise an elastic member <NUM> situated between the annular shoulder <NUM> of the pin head <NUM> and the base <NUM>. The elastic member <NUM> can be configured to bias (i.e., apply a directional force to) the pin head <NUM> away from the base <NUM>. The elastic member <NUM> can comprise any type capable of applying a biasing force within the frangible detent pin <NUM>. In the example shown, the elastic member <NUM> comprises a coil spring, but this is not intended to be limiting in any way.

The second portion <NUM> of the pin head <NUM> can contact the shaft <NUM> of the base <NUM> to interconnect the base <NUM> and the pin head <NUM>. Thus, an axial compressive force applied to the pin head <NUM> is transmitted to the base <NUM> though the contact of the second portion <NUM> and the shaft <NUM>. When a compressive load acting on the pin head <NUM> is less than the predetermined threshold compression load the interconnection between the pin head <NUM> and the base <NUM> acts as a rigid interconnection with the frangible detent pin <NUM> being in a rigid stage. Stated differently, the frangible connection is maintained. Conversely, when the compressive load exceeds the threshold compression load, the frangible connection fails and the frangible detent pin <NUM> enters a spring-loaded stage. In the spring-loaded stage the shaft <NUM> no longer resists movement of the pin head <NUM> since the shaft <NUM> is no longer coupled to the outer portion <NUM> of the base <NUM>. Instead, the pin head <NUM> is moveable relative to the base <NUM> and the elastic member <NUM> biases the pin head <NUM> away from the base <NUM>. This will be shown more clearly with respect to <FIG> and <FIG>,.

The first detent <NUM> can be sized and configured as needed or desired. In one example, the first detent can comprise a shallow detent as compared with other detents. A shallow detent can be defined as a detent having a depth less than half of the radius of the hemispherical shape of the first portion <NUM> of the pin head <NUM>. Thus, the angle at which the hemispherical shape interacts with a wall of the detent can be less than thirty degrees. Because the angled surfaces act as an inclined plane, the axial force acting on the frangible detent pin <NUM> can be double the lateral force between the first member <NUM> and the second member <NUM>. Thus, the second member <NUM> can move relative to the first member <NUM> if a lateral force is sufficient to act on the frangible detent pin <NUM> to depress the frangible detent pin <NUM>.

With the frangible detent pin <NUM> in the rigid stage (as shown in <FIG>), it is able hold the second member <NUM> in place within the first detent <NUM> even when subjected to a relatively large lateral force. However, when a lateral force is present that is sufficient to cause the axial compressive force acting on the frangible detent pin <NUM> to exceed the threshold compression load, the frangible connection fails, the frangible detent pin <NUM> transitions to the spring-loaded stage, and the second member <NUM> is able to rotate relative to the first member (as shown in <FIG>).

With the frangible connection of the frangible detent pin <NUM> fractured, the shaft <NUM> is caused to displace into the socket <NUM> of the outer portion <NUM>. Under the applied compression load, the elastic member <NUM>, in this example a spring, compresses causing the pin head <NUM> to retract into the bore <NUM> of the first member <NUM> and out of the first detent <NUM> where the second member <NUM> is able to rotate relative to the first member <NUM> as intended. The elastic member <NUM> provides the frangible detent pin <NUM> with a spring constant in the spring-loaded stage, where the pin head <NUM> and the base <NUM> are able to move relative to one another under a spring load compared to the rigid behavior of the frangible detent pin <NUM> in the rigid stage where the pin head <NUM> and the base <NUM> model a rigid rod (i.e., behave rigidly) due to the frangible connection between them. Without the spring-loaded stage, the second member <NUM> would not rotate relative to the first member <NUM> without damaging one or both of the first and/or second members <NUM> and <NUM> or the frangible detent pin <NUM> due to high frictional forces between the pin head <NUM> and the second member <NUM>.

Once the threshold compression load is reached causing the frangible connection to fracture or fail, and once the frangible detent pin <NUM> transitions to the spring-loaded stage, rotation of the second member <NUM> can be initiated, wherein the frangible detent pin <NUM> is caused to move out of the first detent <NUM>. Further rotation of the second member <NUM> can cause the frangible detent pin <NUM> to ride along a surface of the second member <NUM> as the elastic member <NUM> applies a biasing force to the shaft <NUM> of the frangible detent pin <NUM> causing the shaft <NUM> to remain in the socket <NUM> of the base <NUM> of the frangible detent pin <NUM>. Upon further rotation of the second member <NUM>, and upon the frangible detent pin <NUM> reaching a second detent (e.g., the second detent <NUM> in the example shown), the elastic member <NUM> functions to bias the pin head <NUM> of the frangible detent pin <NUM> into the second detent <NUM>, or in other words, the pin head <NUM> is caused to be inserted into the second detent <NUM>, thus securing the second member <NUM> in a discrete position relative to the first member <NUM>. The second detent <NUM> can be any size and configuration suitable for the intended purpose. In one example, the second detent <NUM> can comprise a deeper configuration than the first detent <NUM> that secures the second member <NUM> in a discrete position relative to the first member <NUM>. In contrast to a shallow detent, a deeper detent, comparatively speaking, is a detent having a depth or radius that is the same (or substantially the same as) or greater than the radius of the hemispherical shape of the first portion <NUM>. Thus, the angle at which the hemispherical shape interacts with a wall of the detent is a substantially right angle. Therefore, any lateral forces between the first member <NUM> and the second member <NUM> do not translate into compressive axial forces that would displace the pin head <NUM> of the frangible detent pin <NUM>, and thus the frangible detent pin <NUM> secures the second member <NUM> laterally relative to the first member <NUM>.

It is noted that the detent system can comprise any number of detents, and also that the detents can comprise any needed or desired depth. Indeed, the detents in a particular detent system can comprise constant or the same depths, differing depths, and these can be present in any number. As such, the number, configuration and depth of the specific detents discussed herein is not intended to be limiting in any way.

<FIG> illustrate a system <NUM> for securing a moveable member in accordance with another example of the present invention. In this example, the system <NUM> comprises a first member <NUM> moveably secured to a second member <NUM> in a sliding configuration, and a detent system <NUM> operable with the first and second members <NUM>. The detent system <NUM> is similar in some respects to the detent system <NUM> described above, but comprises some differences as discussed below. The first member <NUM> translates relative to the second member <NUM> along a channel <NUM>. The detent system <NUM> can comprise, and the first member <NUM> can be secured in a first configuration by, a frangible detent pin <NUM> (as shown in <FIG>). The first member <NUM> can translate to, and can be secured within, a second configuration (as shown in <FIG>) when a sufficient lateral force is applied between the first member <NUM> and the second member <NUM> to force the frangible detent pin <NUM> to fracture its frangible connection (discussed below) and to enter a spring-loaded stage, similar to the spring-loaded stage described above.

The first member <NUM> can comprise a bore <NUM> for supporting and securing the frangible detent pin <NUM>. The detent system <NUM> can comprise a first detent <NUM> formed in the second member <NUM> for securing the first member <NUM> in the first configuration (shown in <FIG>), and a second detent <NUM> for securing the first member <NUM> in a second configuration (shown in <FIG>). The first detent <NUM> can be a shallow detent and the second detent <NUM> can be a deeper detent, similar to the first and second detents described above. The frangible detent pin <NUM> can comprise a base <NUM>, a pin head <NUM> interconnected with the base <NUM>, and an elastic member <NUM> biasing the pin head <NUM> away from the base <NUM>. The detent system <NUM> can further comprise a shear pin <NUM> supported within the first member <NUM>, which can extend into the bore <NUM> so as to be positioned adjacent the pin head <NUM>. Interference between the pin head <NUM> and the shear pin <NUM> causes the frangible detent pin <NUM> to be rigidly positioned relative to the first member <NUM>, and consequently the base <NUM> is secured in the bore <NUM> of the first member <NUM>. The shear pin <NUM> forms a frangible connection between the base <NUM> and the pin head <NUM> such that the pin head <NUM> is rigidly located relative to the base <NUM> until the shear pin <NUM> fails. The shear pin <NUM> is configured to shear (fail) when the axial compressive force exerted on the pin head <NUM> exceeds a predetermined threshold. The predetermined threshold can be varied by changing the diameter of the shear pin <NUM> and/or the material of the shear pin <NUM>.

As long as the shear pin <NUM> has not been sheared, the frangible detent pin <NUM> is in a rigid stage and lateral forces between the first and second members <NUM>, <NUM> will not result in relative lateral movement between the first and second members <NUM>, <NUM> due to interference between the sides of the first detent <NUM> and the pin head <NUM>. Because the first detent <NUM> can be a shallow detent, lateral forces can exert a corresponding compressive force on the pin head <NUM>. If the corresponding compressive force exceeds the axial compressive threshold, the shear pin <NUM> fails and the frangible detent pin <NUM> enters a spring-loaded stage, wherein the first and second members <NUM>, <NUM> can move relative to one another. Indeed, upon shearing of the shear pin <NUM>, the shear pin <NUM> no longer interferes with the pin head <NUM> and the pin head <NUM> can be retracted into the bore <NUM>. Once the shear pin <NUM> fails, lateral forces acting on the first member <NUM> can cause the first member <NUM> to move relative to the second member <NUM>, facilitated by the pin head <NUM> of the frangible detent pin <NUM> being displaced and able to move out of the first detent <NUM>. Further sliding movement of the first member <NUM> relative to the second member <NUM> can cause the pin head <NUM> of the frangible detent pin <NUM> to slide about the surface of the second member <NUM> between the first detent <NUM> and a second detent <NUM> (as shown in <FIG> and <FIG>).

Still further sliding of the first member <NUM> into a position about the second detent <NUM> can cause the pin head <NUM> to be received within the second detent <NUM> as a result of the biasing force acting on the pin head <NUM> by the elastic member <NUM> (a coil spring in this case), thus securing the first member <NUM> in the second configuration. Because the second detent <NUM> can be a deeper detent than the first detent <NUM>, lateral forces between the first and second members <NUM>, <NUM> do not translate into substantial axial compression loads that would cause the pin head <NUM> to displace out of the second detent <NUM> as compared to those acting on the pin head <NUM> when received within the first detent <NUM>. Thus, the frangible detent pin <NUM> secures the first member <NUM> relative to the second member <NUM> in the second configuration.

The various detent systems described herein utilize a frangible detent pin to secure a moveable member in various positions relative to another member, such as a stationary member. In the examples described herein, the frangible detent pin provides for two different spring constants based on the status of the frangible connection, and whether or not this has been fractured or has failed. The first spring constant where the frangible detent pin models or behaves as a rigid rod (referred to as the rigid stage herein) can be used with a shallow detent to rigidly position the moveable member in a first configuration or position. The second spring constant can be achieved upon the failure of the frangible connection where the frangible detent pin transitions to a spring-loaded stage, wherein the frangible detent pin can be used to allow the moveable member to transition from the first configuration to a second configuration, the frangible detent pin being received within a deep detent to fixedly position the moveable member in the second configuration.

It is to be understood that the examples set forth herein are not limited to the particular structures, process steps, or materials disclosed, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular examples only and is not intended to be limiting.

Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more examples. In the description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of the technology being described.

Claim 1:
A frangible detent pin (<NUM>, <NUM>) comprising:
a base (<NUM>, <NUM>) configured to be secured within a bore (<NUM>, <NUM>);
a pin head (<NUM>, <NUM>), wherein the pin head and the base are interconnected through a frangible connection; and
an elastic member (<NUM>, <NUM>) configured to bias the pin head away from the base,
wherein the frangible detent pin has a rigid stage in which the pin head is rigidly positioned relative to the base and a spring-loaded stage in which the pin head is moveable relative to the base under a compression load between the pin head and the base, and
wherein the frangible detent pin is configured to transition from the rigid stage to the spring-loaded stage in response to the compression load exceeding a predetermined threshold sufficient to cause the frangible connection to fail.