Abstract:
Secondary safety for firearm and method for automatic locking firearm&#39;s trigger even with disengaged primary safety. The mechanism includes a rigid bar and a spring unit biasing the rigid bar against the firearm&#39;s body to transfer vectored force to the back of the trigger against the trigger&#39;s movement, and is cooperated with firearms using existing firearm&#39;s components. Secondary safety blocks trigger immediately each time the user&#39;s finger is taken off the trigger and can be disengaged only with user&#39;s input directed against the vectored force and increasing it.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims benefit of and priority from the U.S. provisional patent application No. 62/101,667, filed on Jan. 9, 2015. The disclosure of this provisional application is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a system and method for improving gun safety and, in particular, to a secondary safety feature preventing accidental or negligent discharge of a firearm. 
     BACKGROUND 
     Accidental discharge is the event of a firearm firing (discharging) at a time not intended by the user. Perhaps most commonly, accidental discharges (sometimes called ADs by military and police personnel and sometimes referred to as negligent discharges) occur when the trigger of the firearm is deliberately pulled for a purpose other than shooting (such as demonstration, function testing, or dry-fire practice, for example) while ammunition is present in the chamber. Another, second common cause of accidental discharges occurs when the gun-handler places his finger on the trigger before he has decided to shoot. With the finger being so positioned, many events may cause the finger to compress the trigger unintentionally. For example, if one attempts to holster the firearm with his finger on trigger, the holster edge will drive the finger onto the trigger, causing a likely discharge. If one stumbles or struggles (with an adversary) with his finger on the trigger, the grasping motion of both hands will likely cause the trigger finger to press the trigger. 
     On occasion, an accidental discharge can occur for a reason other than the finger pulling the trigger, such as dropping a loaded weapon (whether or not secured around the torso of the user with a sling). Because of this possibility, most of the recently produced pistols are designed with a “drop-safety” or firing pin block, a mechanism inhibiting or isolating the firing pin, preventing accidental discharge if the firearm is dropped. However, most long guns do not have drop-safety features. Another common incidence of accidental discharge of the firearm (in particular, assault rifles) occurs when the user lets the rifle go and, before the rifle hangs on a sling over the user&#39;s torso, the rifle rubs against the torso and the items of user&#39;s clothing on its way to the hanging position. Any item protruding from the clothing of the user can and often does depress the trigger upon interaction with the dropped firearm. While gun safety rules recognize these possibilities and aim to prevent them, it is the tangible safety features—such as, for example, a trigger lock (an example  110  of which is shown in  FIG. 1A , depicting a firearm  112 ) and a mechanism often called a “safety” (such as an external safety lever or latch on the side of the firearm or a grip safety mechanism of a handgun, an example  120  of which is shown in  FIG. 1B , depicting a portion  122  of a firearm)—that are relied on to prevent an accidental discharge. 
     However, in the heat of the moment or just because of the mundane inattention, the user often simply forgets to activate the firearm&#39;s external, manual safety such as the safety  120  (interchangeably referred to herein as an external safety latch, manual safety latch, primary safety, or a primary safety mechanism), thereby negating the very purpose of the primary safety. 
     As far as a trigger lock mechanism is concerned, generally, two pieces come together from either side behind the trigger and are locked in place to form a lock that is substantially immovable and not repositionable unless unlocked with a key or combination. This physically prevents the trigger from being pulled to discharge the weapon. Other types of trigger locks do not go behind the trigger, but encompass the full area behind the trigger guard making the trigger inaccessible. It is well recognized in the art, however, that trigger locks are not designed to be used on loaded guns (see, for example, discussion in “Hype Over Trigger Locks Provokes Fear of Firearm Accidents”, E. Slater, Los Angeles Times, Feb. 16, 1999), which makes them basically useless for preventing negligent discharges. It is also well understood that the existing safety measures, while effective in majority of situations, occasionally may fall short of being “fool-proof” and providing a peace of mind to a responsible armed citizen. 
     There remains an unmet need, therefore, for a firearm safety feature that compensates for the discharge accidents that are not prevented by the primary safety mechanism 
     SUMMARY 
     Embodiments of the invention provide an article of manufacture that includes a rigid bar having first and second ends, the rigid bar having first and second portions that form a spatial bend in the rigid bar, the first end corresponding to the first portion, the second end corresponding to the second portion, the spatial bend defined in a plane. The article also includes a spring mechanism affixed to the second portion in a spatial coordination that defines, in operation of the spring mechanism, a vector of spring force in said plane. The article is configured for use as a secondary safety mechanism with a firearm. 
     Embodiments also provide a method for locking a trigger of a firearm with a secondary safety mechanism. The method includes a step of positioning the secondary safety mechanism between a back side of the trigger and a grip of the firearm. The secondary safety mechanism contains (i) a rigid bar having first and second ends, the rigid bar having first and second portions forming a spatial bend in the rigid bar, the first end corresponding to the first portion, the second end corresponding to the second portion, the spatial bend defined in a first plane, and (ii) a spring mechanism affixed to the second portion, between the second portion and the body, in a spatial coordination that defines a vector of spring force in said first plane. The positioning of the secondary safety mechanism is carried out such that the first plane is parallel to a second plane, the second plane defined by a plane in which the trigger moves during operation of the firearm. The method additionally includes a step of attaching the secondary safety mechanism to a body of the firearm through a hinge to form, with said secondary safety mechanism, a lever pivoting about the hinge in the first plane between first and second angular positions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be more fully understood by referring to the following Detailed Description in conjunction with the generally not-to-scale Drawings, of which: 
         FIGS. 1A, 1B  illustrate schematically a trigger lock and a manual (primary) safety latch, respectively, conventionally used with firearms; 
         FIGS. 2A, 2B, 2C, and 2D  illustrate schematically an embodiment of the secondary safety mechanism in different side views; 
         FIG. 2E  illustrates, in top view, a related embodiment of the secondary safety mechanism; 
         FIG. 3  illustrates, in side view, another related embodiment of the secondary safety mechanism; 
         FIG. 4  illustrates, in side view, yet another related embodiment of the secondary safety mechanism; 
         FIGS. 5A, 5B  are schematic illustrations of the assembled embodiment of  FIGS. 6A, 6B, 6C ; 
         FIGS. 6A, 6B, 6C  provide different views of the alternative embodiment that is assembled from the constituent components of  FIGS. 7A, 7B, 7C, 7D, and 7E ; 
         FIGS. 7A, 7B, 7C, 7D, 7E  provide different views of constituent components of an alternative embodiment of the secondary safety mechanism; 
         FIG. 8A  illustrates operable cooperation between the embodiment of the secondary safety of  FIG. 2A  and the firearm in the first angular position of the embodiment, in which the spring mechanism is in contact with the body of the firearm and exerts a first vectored force on the secondary safety, the first end of the secondary safety abuts against a back side of the trigger, and a position of the trigger is locked by such abutting due to the first vectored spring force transferred to the back side of the trigger through the secondary safety; 
         FIG. 8B  illustrates operable cooperation between the embodiment of the secondary safety of  FIG. 2A  and the firearm in the second angular position of the embodiment, in which the spring mechanism is in contact with the body of the firearm and exerts a second vectored spring force on the secondary safety, the first end of the secondary safety is separated from the trigger to define a spatial gap between a tip of the trigger and the secondary safety, and the trigger is released to move from the position in which it was locked as shown in  FIG. 8A ; 
         FIG. 9A  is a top view of a related embodiment of the secondary safety configured to be attached to and detached from the firearm without a need to remove a trigger-guard pin. 
         FIG. 9B  is a schematic diagram showing, in side view, the cooperation of the embodiment of  FIG. 9A  with a firearm; 
         FIG. 9C  is a schematic top-view diagram of another related embodiment of the secondary safety. 
     
    
    
     DETAILED DESCRIPTION 
     A problem of accidental discharge of a firearm, occurring when the primary safety mechanism is left disengaged (“off”, leaving the trigger unlocked) or becomes disengaged due to external circumstances, is solved by providing a secondary safety (interchangeably referred to herein as a secondary safety mechanism). The activation (and re-activation) of the secondary safety mechanism (causing the locking of the trigger by the secondary safety mechanism) is automatic, occurs independently of volition of and does not require the input from the user of the firearm. An embodiment of the invention re-activates upon release of pressure of the natural hand grip on rifle, at which time the spring system of the embodiment reengages a trigger block portion of the secondary safety mechanism to go automatically behind the trigger. At the same time, the de-activation of the secondary safety mechanism (as a result of which the secondary safety mechanism does not lock the trigger anymore) requires a conscious mechanical input from the user. Accordingly, the trigger of the firearm requires two different inputs provided by the user. 
     Example 1 
       FIGS. 2A, 2B, 2C, and 2D  illustrate schematically an example  200  of an article of manufacture embodying a secondary safety mechanism according to the idea of the invention. The article  200  includes a rigid bar  202  (made, for example, of metal or material the mechanical properties of which are comparable to or exceeding that of metal, such as specific ceramics or graphite, for example) having first and second ends  204 ,  208 . The rigid bar includes first and second portions I, II that are united, abutted to one another such as to spatially extend one another and to form a spatial bend defined in a first plane (as shown—in the xz-plane). The internal curvature of the so-bent bar defines an inner surface  210 , while the outer surface of the bar is marked  214 . As shown, the portions I, II are made integrally with one another (for example, in one mold and from the same material); alternatively, these portions can be fabricated separately (optionally—from different materials) and then adjoined or integrated. 
     In reference to  FIGS. 2B and 2C , the first portion I of the embodiment  200  includes two walls  218 ,  222  separated from one another along an axis (as shown—along the y-axis) that is perpendicular to the first plane. These two walls, together with the remaining sections of the portion I, form a framed opening  226  in and through the rigid bar. The purpose of such configuration, as will be discussed below, is to accommodate the trigger guard of a firearm. In the article  200 , each of the walls  218 ,  222  (forming part of the frame around the opening) contains a corresponding aperture. These apertures  218 A,  22 A are coaxial with one another and configured to accommodate a pin with the use of which in one implementation, the article  200  is cooperated with the firearm. In reference to  FIGS. 2C and 2D , it is appreciated that the width W 1  of the frame of the opening  226  can be substantially equal to or larger than the width of the first end or prong  204 . In practice it may be preferred to make the first end or prong of the article  200  approximately as wide as the trigger of the firearm with which the article is used, and the width W 1  slightly wider than the trigger guard (for example, 10 to 50 percent wider). The width of the second end  208  (not marked) can be generally arbitrary, but for practical convenience it may be dimensioned somewhere between or about the values of W 1  and W 2 . In a specific case, the rigid bar  202  can be made symmetrical with respect to the first plane (xz-plane). 
     The article  200  is additionally equipped with a spring mechanism configured to generate, in operation and after the article  200  is cooperated with the firearm, a vectored force pushing the second portion II away from the body of the firearm, as discussed below. As shown in the example of  FIGS. 2A through 2D , the spring mechanism includes a coil spring  230  attached to the second portion II at only one end of the spring. Provided that, in operation, the spring mechanism is configured to be abutting the body of the firearm, it may be advantageous to shape the coil spring  230  as a cone (as shown in  FIG. 2D ). In this case, a diameter of a coil at the second (free) end of the spring  230  is bigger than that of a coil at the end that is affixed to the second portion II, and a surface tangential to the loops of the soil spring  230  is a conical surface. Such configuration is beneficial in that it increases the area of contact between the spring mechanism of the article  200  and the body of the firearm, in operation. Generally, a spring mechanism used in an embodiment of the present invention includes a combination of multiple and, optionally, different type springs, or a combination of at least one spring and a component biased against and moveable by such spring. In related embodiments, for example, the spring mechanism may include different contraptions such as, for example, a leaf spring configured as a cantilever spring (that is fixed to the second portion II at only one end), or a combination of a torsion spring with the spring base (as discussed below). 
     Example 2 
     It is appreciated that a particularly shaped perimeter of the article  200 , illustrated in  FIGS. 2A, 2B, 2C, and 2D  is not required for proper operation of the article  200 . For example, in a related asymmetric embodiment  250  (which is the modified embodiment  200 ), schematically shown in top view in  FIG. 2E , the wall  222  (of the frame defining the opening  226  of embodiment  200 ) is not present. As a result, the opening  256 , which accommodates in operation the trigger guard of the firearm, is walled at only three sides. Such configuration may be of interest in some circumstances as it may simplify the installation of the secondary safety element onto the firearm. 
     Example 3 
     In another related embodiment  300  (shown schematically in side view in  FIG. 3 ) that has the first and second ends  304 ,  308 , the rigid bar  302  of the article  300  may be formed from the first and second portions joined such as to define inner and outer surfaces  310 ,  314  the radii of curvatures of which are monotonically changing. The side view of  FIG. 3  corresponds to the side view of  FIG. 2A  (the remaining views of the embodiment  300  being similar to those of  FIGS. 2B, 2C , and  2 D). As shown, the embodiment  300  is equipped with a spring mechanism including a leaf cantilever spring  330 . 
     Example 4 
     In another related embodiment, shown as  400  in  FIG. 4 , the portions I, II are configured to contain straight regions such as to form, when the portions I, II are united, not only the bent of the rigid bar  402  in the xz-plane, but also a dihedral angle A in the same plane in which the bent of the bar  402  is defined. The embodiment  400  is shown for simplicity of illustration without a spring mechanism. 
     In operation, embodiments of the secondary safety that were discussed above and similar embodiments are cooperated with a particular firearm such as to form a lever (i) that is configured to be pivoted about a point or an axis by a force applied by a finger of the user of the firearm to portion II of the embodiment of the secondary safety and (ii) that, as a result of such pivoting, locks a trigger of the firearm in an off position. While details of the installation of an embodiment of the secondary safety mechanism on the firearm can differ, the principle of the spatial cooperation between the embodiment and the firearm will be readily understood in reference to  FIGS. 8A and 8B .  FIGS. 8A, 8B  illustrate the installation of the embodiment of  FIG. 2A  on a pin  804  of the guard  806  of the trigger  808  of the firearm  810 . In one case, the pin  804  is temporarily removed from the trigger guard  806 , and a plank of the guard  806  is tilted to open the guard  806  and to set the embodiment  200  onto the plank such that the plank passes through the opening  226 . Afterwards, the plank of the guard  806  is closed, and the pin  804  is re-installed in its original position—this time, both through the openings  218 A (and  222 A, if present) of the embodiment  200  and the pin-openings of the guard  806 . Such installation structurally results in a lever, formed by the embodiment  200 , that is biased with the spring mechanism (in this case—the coil spring  230 ) against the body of the firearm  850  and that is configured to operate by pivoting the embodiment  200  about the pin  804 . In operation, the pivoting of the secondary safety occurs between two different angular position, which are illustrated respectively in  FIGS. 8A and 8B . 
     As shown in  FIG. 8A , in the first angular position of the secondary safety mechanism (denoted by an angle A 1  formed between a line  850 , which is tangential to the outer surface of the first portion of the embodiment  200  at a chosen point of its first end  204 , and the z-axis in the xz-plane), the end of the spring mechanism  230  that is not affixed to the embodiment  200  is in contact with the body of the firearm  850 . At the same time, the first end  204  of the embodiment  200  is abutted (touches at the surface) against the back side of the trigger  808  at a point that is sufficiently distanced from the tip  852  of the trigger. The embodiment  200  and its spring mechanism are judiciously dimensioned, depending on the specific geometry of the firearm  810 , to ensure that in the configuration of  FIG. 8A  the spring mechanism is biased to exert a first vectored force onto the embodiment  200  such as to press the first end  204  against the back side of the trigger  806  to fix and lock the trigger  806  in the “off”, not depressed position. 
     Changing the mutual positioning of the elements shown in  FIG. 8A —that is, unlocking the trigger  806 —requires the use to take a complex action that includes pivoting the embodiment  200  about the pin  804 . Specifically, the user has to press the second portion II of the embodiment at the inner surface  210  towards the body  850  (as shown—towards the grip of the firearm  810 ) such as to compress (or, in a different implementation, create a torsion in) the spring mechanism while the first end  204  slides along and under the trigger  808  towards the trigger guard  806 , such as create, at the second angular position of the embodiment  200 , a gap G between the trigger  808  and the embodiment  200 . The spatial cooperation between the firearm  810  and the embodiment  200  in the second angular position is shown in  FIG. 8B , where the angle A 2  formed by the z-axis and the line  850  is different from A 1  and where the kinetic energy, stored in the spring mechanism as a result of the pressure on the second portion II by the user&#39;s finger, is illustrated by a shortened length of the coil spring  230  as compared to that of  FIG. 8A . Once the secondary safety mechanism is in such second angular position, the trigger  808  is free to move from its locked-by-the-secondary-safety-mechanism position (of  FIG. 8A ) and can be depressed by the user to discharge the firearm  810 . 
     Example 5 
     Another related embodiment  500  of the secondary safety mechanism is illustrated in  FIGS. 5A and 5B  and, in different views in  FIGS. 6A, 6B, 6C .  FIGS. 7A, 7B, 7C, 7D, and 7E  illustrate some of the individual components of the mechanism  500  with examples of dimensions. 
     The embodiment  500  includes a rigid bar  502  and a spring mechanism  530  moveably cooperated with the rigid bar  502 . The bar  502  is structured by analogy with the rigid bar  202  of the embodiment  200 , in that it includes the first end or prong  504 , the second end  508 , the opening  526  framed in part by the walls  518 ,  522 , and the co-axial apertures  518 A,  522 A in the walls  518 ,  522 . The apertures  518 A,  522 A are dimensioned to accommodate a pin of the trigger guard of a particular firearm with which the embodiment  500  is intended to be used. 
     The spring mechanism  530  of this related embodiment, however, contains two portions: a spring base  530 A (which has a shape reciprocal to the shape of the second end  508  to facilitate the mechanical mating between the two), and the torsion spring element  530 B. The torsion spring element  530 B includes, in turn, a torsion spring (not shown) set on a pin that simultaneously connects the spring base  530 A and the second end  508  through the co-axially aligned cylindrical openings  540 ,  542 . The openings  540 ,  542  are made in the spring base  530 A and the second end  508 , respectively. As shown, the spring base  530 A includes two protrusions (each having a throughout opening  540 ) configured to “sandwich” the second end  508  therebetween when attached to the second end with the use of the torsion spring element  530 A. It is appreciated that in a related implementation, the situation may be reversed: the spring base  530 A can have only one protrusion that is fitted between the portions of the second end  508 , shaped like a dove-tail. 
     When assembled and cooperated with a firearm, the embodiment  500  is hingedly set on a pin of a trigger guard through the openings  518 A,  522 A (as discussed for the embodiment  200  in reference to  FIGS. 8A and 8B ), while the spring base  530 B is constantly kept in contact with a grip of the firearm due to the force-bias created by the torsion spring. When the embodiment  500  is in a first angular position (similar to that shown in  FIG. 8A ), the torsion force formed by the torsion spring is larger than that corresponding to the second angular position. 
     It is understood, therefore, that the (re-)activation of the secondary safety mechanism such as the mechanisms  200 ,  500 , for example, causes locking of the trigger of the firearm and occurs automatically, due to the spring bias, each time when the finger of the user is removed from the trigger of the firearm, without any additional action from the user. An embodiment of the invention is configured to re-activate upon release of pressure of the natural hand grip on rifle, at which time the spring system or mechanism of the embodiment reengages a trigger block portion of the secondary safety to go automatically behind the trigger. In other words, even when the primary safety of the firearm is de-activated, the trigger will be locked (as shown in the example of  FIG. 8A ) with the embodiment of the invention positioned in the first angular position. On the contrary, the de-activation of the secondary safety mechanism (as a result of which the trigger is no longer locked with the secondary safety mechanism) does not happen by occurrence as it requires a conscious effort and input on the part of the user to bring the mechanism from the first angular position to the second angular position (as shown in the example of  FIG. 8B ). The secondary safety mechanism can be kept de-activated as long as required by simply keeping it depressed (in the second angular position) with a finger. Notably, the use of the secondary safety according to the invention does not require any additional training on the part of the user. 
     Example 6 
     Yet another related implementation  900  of the invention is illustrated in the views of  FIGS. 9A, 9B . The cooperation of this embodiment with a firearm does not require a removal of the guard pin of the firearm, while its configuration facilitates the addition and removal of the embodiment to and from the firearm in real time, on the order of seconds. As will be appreciated by a person of ordinary skill in the art, the implementation  900  is structured around the contraption of  FIGS. 6A, 6B, 6C , and  FIGS. 7A and 7C through 7E , which is judiciously modified to facilitate the attachment of the implementation to and detachment of it from the firearm without requiring a removal of the guard pin. 
     Specifically,  FIG. 9A  shows in top view a portion of the embodiment  900 , in which the rigid bar  902  (shown partially, with the prong  904 ) is affixed to a clip portion  910 . The clip portion  910  is configured, in operation, to be snapped onto a firearm  810  and, in one case, onto a portion  912  of the trigger guard. By analogy with the embodiment  250  of  FIG. 2E , portion I of the  902  includes an opening  902 A formed by three walls. One of the three walls—the side wall  918 —has an aperture  918 A dimensioned to accommodate a pin of the trigger guard of a particular firearm therethrough. 
     The clip  910  is formed by merging together first and second parts of the clip to form a “U”-shaped portion  912 . As shown in  FIG. 9A , the first part of the clip is a plate member  910 A having a straight portion and a bent portion defining a hook at the end of the straight portion. The second part of the clip is a plate member  910 B,  910 C, which plate member is extended beyond the bent portion defining a hook of the plate member  910 A (such extension is indicated as  910 C). 
     The clip is preferably but not necessarily dimensioned to provide for a spring bias between the opposing sides  910 A,  910 B that form the “U” of the clip. So structured, the portions  910 A,  910 B apply a force to the portion of the firearm onto which the clip is attached, squeezing the portion of the firearm therebetween. In the simplest case, clip  910  is made of a metal plate, a ceramic plate, or a plate made of appropriate resilient plastic material. The portion  910 C of the plate member  910 B,  910 C contains a through hole  914  dimensioned to fit over the pin of the trigger guard (and, therefore, is dimensioned the same way as the aperture  918 A is dimensioned). In one embodiment, each of the through holes or apertures  914 ,  918 A is cylindrical (defined by a corresponding cylindrical wall). In one embodiment, the affixation of the rigid bar to the clip portion  910  is permanent, by molding or soldering. However, regardless of whether the clip portion  910  and the rigid bar  902  are attached permanently or whether the embodiment  900  can be taken apart by separating the elements  902  and  910 , the cooperation between the elements  902  and  910  is such that the apertures  918 A and  914  are mutually aligned to be co-axial. In a schematic diagram of  FIG. 9B , the clip  910  is indicated with a dashed line and is shown not-to-scale, with the width of the plate member indicates as W. 
     In order to attach the secondary safety  900  to the firearm, the article  900  in positioned such that one end of the pin of the trigger guard is passed through the openings  914 ,  918 A to position the prong  904  behind and in contact with the trigger (in a fashion discussed above) while the clip  910  grasps a portion of the firearm to ensure that the arms  910 A,  910 B of the “U”  912  of the clip  910  fit over and onto the opposite sides of the firearm. The detachment of the secondary safety from the firearm is done in reverse order, and also without the removal of the trigger guard pin. 
     While constructing the clip  910  from the first and second portions each of which is structured as a plate may be preferred because it may provide a more reliable attachment of the embodiment  900  to the firearm, it is understood that in a related embodiment (not shown) the clip portion  910  can be formatted from a cylindrical rod of diameter W (and, in a specific case, from a wire) made of judiciously chosen material. In another related embodiment, the clip portion  910 ′ for use with the rigid bar  902  can be formed from first and second parts as shown in  FIG. 9C . Here, the first part shown as  910 A′ defines the “U”  912 ′, while the second part is denoted as  910 B,  910 C. The corresponding wide surfaces (defined in the xz-plane) of the first and second parts are affixed to one another along the length L. The extension of the second part beyond the “U”  912 ′ is labeled  910 C. This extension  910 C has a through hole  914  (the axis of which is parallel to the y-axis) and is attached to the rigid bar  902  (schematically indicated with a dashed line), by analogy with the case shown in  FIG. 9A . 
     In accordance with embodiments of the present invention, method and apparatus are disclosed for configuring a secondary safety for use with a firearm, which is necessitated by the first-hand experience of the inventor and the military. Embodiments of the secondary safety are configured and intended as a back-up mechanism, an addition to the primary safety latch the activation of which may be forgotten by the user of the firearm or which becomes inadvertently disengaged. The proposed secondary safety is structured to be compatible with most of common grips of the firearms such as HOGUE or Ergo grips, for example, and provides a field-ready firearm with a passive trigger-locking mechanism operating in addition to—and independently from—the primary safety mechanism. 
     Therefore, embodiments of the invention provide an article of manufacture that contains a rigid bar having first and second ends (the rigid bar including first and second portions forming a spatial bend in the rigid bar, the first end corresponding to the first portion, the second end corresponding to the second portion, the spatial bend defined in a plane) and a spring mechanism affixed to the second portion in such a spatial coordination as to define, in operation of the spring mechanism, a vector of spring force in the plane. The first and second portions may be configured to form a dihedral angle in the plane. The rigid bar has inner and outer surfaces, the inner surface corresponding to an inside curvature of the bend, the outer surface being opposite to the inner surface, and the spring mechanism may include a leaf spring attached to the outer surface at only one end of the spring and disposed in the plane. In a related implementation, the rigid bar has inner and outer surfaces, the inner surface corresponding to an inside curvature of the bend, the outer surface being opposite to the inner surface, while the spring mechanism may include a coil spring attached to the outer surface at only one end of the spring. Alternatively, the spring mechanism includes a rigid plate hingedly connected to the second end and a torsion spring one end of which abuts against the second portion and another end of which abuts against the rigid plate. An article of manufacture may additionally include a firearm connected to the rigid bar with a hinge such that to position the rigid bar to define a lever pivoting about the hinge in the plane between first and second angular positions. In the first angular position i) the spring mechanism is in contact with a body of the firearm to exert a first spring force on the rigid bar; ii) the first end abuts against a back side of a trigger of the firearm at a contact point, and iii) a position of the trigger is locked by the first end due to the first spring force applied to the back side at the contact point. In the second angular position a) the spring mechanism is in contact with the body of the firearm to exert a second spring force on the rigid bar, the second spring force being larger than the first spring force; b) the first end is separated from the trigger to define a spatial gap between a tip of the trigger and an outer surface; c) the trigger is released to move from the position. In the first angular position, the contact point may be spatially separated from the tip of the trigger and the first portion may be located between the back side of the trigger and a trigger guard. A first distance defined between the second portion and the body in the first angular position may be larger than a second distance defined between the second portion and the body in the second angular position. 
     The present invention also encompasses a method for locking a trigger of a firearm. The steps of the method include positioning a secondary safety mechanism between a back side of the trigger and a grip of the firearm (the secondary safety mechanism including (i) a rigid bar having first and second ends, the rigid bar having first and second portions forming a spatial bend in the rigid bar, the first end corresponding to the first portion, the second end corresponding to the second portion, the spatial bend defined in a first plane, and (ii) a spring mechanism affixed to the second portion between the second portion and the body, in a spatial coordination that defines a vector of spring force in the first plane) such that the first plane is parallel to a second plane, where the second plane is defined as a plane in which the trigger moves during operation of the firearm. The steps of the method additionally include attaching the secondary safety mechanism to a body of the firearm through a hinge to form, with said secondary safety mechanism, a lever that pivots about the hinge in the first plane between first and second angular positions. The process of attaching of the secondary safety mechanism to the body may include attaching the secondary safety mechanism to the trigger guard and, in a specific case, using a removable pin of the trigger guard as the hinge. 
     A method may further include a step of attaching a clip portion of the secondary safety to a body of the firearm such as to grasp a portion of the body with the clip and, optionally, compress such body portion with the clip. In a specific case, the clip is fixed about a trigger guard and/or a grip of the firearm. 
     A method may additionally include a step of pivoting the secondary safety mechanism to the first angular position to verify that in the first angular position a) the spring mechanism is in contact with the body and exerts a first spring force on the rigid bar; b) the first end abuts against a back side of the trigger at a contact point, and c) a position of the trigger is fixed by the first end due to the first spring force applied to the back side at the contact point. Here, pivoting may include pivoting the secondary safety mechanism to the first angular position to verify that, when the secondary safety mechanism is in the first angular position and a manual safety latch of the firearm is in off position (disengaged), the trigger cannot move. Alternatively or in addition, the method may include a step of pivoting the secondary safety mechanism to the second angular position to verify that in the second angular position a) the spring mechanism is in contact with the body and exerts a second spring force on the rigid bar, the second spring force being larger than the first spring force; b) the first end is separated from the trigger to define a spatial gap between a tip of the trigger and an outer surface; and c) the trigger is released to move from the position. 
     References made throughout this specification to “one embodiment,” “an embodiment,” “a related embodiment,” or similar language mean that a particular feature, structure, or characteristic described in connection with the referred to “embodiment” is included in at least one embodiment of the present invention. Thus, appearances of these phrases and terms may, but do not necessarily, refer to the same implementation. It is to be understood that no portion of disclosure, taken on its own and in possible connection with a figure, is intended to provide a complete description of all features of the invention. 
     It is also to be understood that no single drawing is intended to support a complete description of all features of the invention. In other words, a given drawing is generally descriptive of only some, and generally not all, features of the invention. A given drawing and an associated portion of the disclosure containing a description referencing such drawing do not, generally, contain all elements of a particular view or all features that can be presented is this view, for purposes of simplifying the given drawing and discussion, and to direct the discussion to particular elements that are featured in this drawing. A skilled artisan will recognize that the invention may possibly be practiced without one or more of the specific features, elements, components, structures, details, or characteristics, or with the use of other methods, components, materials, and so forth. Therefore, although a particular detail of an embodiment of the invention may not be necessarily shown in each and every drawing describing such embodiment, the presence of this detail in the drawing may be implied unless the context of the description requires otherwise. In other instances, well known structures, details, materials, or operations may be not shown in a given drawing or described in detail to avoid obscuring aspects of an embodiment of the invention that are being discussed. 
     The invention as recited in claims appended to this disclosure is intended to be assessed in light of the disclosure as a whole, including features disclosed in prior art to which reference is made.