Abstract:
A trigger mechanism has a hammer, a hammer spring, a trigger pull, a trigger spring, a pivotal linkage between the trigger pull and a sear which has a cam surface and a guide. The hammer has striking and bearing ends and a pivot point between the ends. The hammers&#39; bearing end rides up on the cam surface as it moves between different positions relative to the guide. The hammer pivots around the pivot point and the striking end is moved between the hammer&#39;s seated and cocked positions as the cam surface moves between its positions. The hammer spring has opposite ends connected to the firearm&#39;s frame and the hammer, respectively, which provides a hammer spring force. The hammer spring biases the striking end of the hammer to the seated, striking position and the movement of the hammer to its rearward position is performed against the hammer spring force.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 13/828,722 filed on Mar. 14, 2013 which is hereby incorporated by reference and which claims priority to U.S. patent application Ser. No. 13/333,513 filed on Dec. 21, 2011, now issued as U.S. Pat. No. 8,495,831 and which claims priority to U.S. Provisional Patent Application No. 61/426,458 filed on Dec. 22, 2010. This application also claims the benefit of priority from U.S. patent application Ser. No. 13/662,506 on Oct. 28, 2012 which claims priority from U.S. Provisional Patent Application Ser. No. 61/552,499 filed on Oct. 28, 2011, both of which are hereby incorporated by reference. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not Applicable. 
     APPENDIX 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the trigger mechanism for a firearm, and more particularly to a trigger mechanism that has a sear with a cam surface. 
     2. Related Art 
     There are a number of trigger mechanisms that have been used for firearms, including trigger mechanisms that are particularly designed for single-barrel pistols and multi-barrel pistols. In particular, there are double-action trigger mechanisms that have been designed for Derringer-type pistols. Additionally, there are existing trigger mechanisms which can maintain a constant pressure throughout a trigger pull and can allow for an adjustment of the pressure which is required for the trigger pull, i.e, the trigger pull weight. However, none of these known trigger mechanisms provide an operation that is as smooth and efficient as the trigger mechanism provided in the present invention. In particular, none of these known trigger mechanisms combine the mechanical advantage of a cam surface sear that works in combination with the trigger pull, linkage, hammer and hammer spring to control the trigger pull force as the hammer is forced to rotate from its striking position (i.e., seated position) to its rearward position (i.e., cocked position). 
     Small, light weight pistols, such as those made by Derringer, have been available for many years. While such pistols included double barrel pistols, they were not designed to provide a two shot capability (a so-called “double tap” shooting technique capability) without taking action other than by making successive trigger pulls. Thus, such pistols typically required some additional action by the shooter, such as the flipping of a lever, manually cocking the hammer, or the use of two triggers, in order to provide two shot capability. Even then, once the pistols of the prior art had been discharged they were not designed to be reloaded quickly, easily, or conveniently. 
     The prior art also included such single shot, small, light weight pistols as the “Liberator” which was quite inexpensive to manufacture and which included space within its butt where additional rounds of ammunition could be stored. Once again, however, the design of the Liberator pistol did not permit reloading to be quick, easy, or convenient. Further, the design of the Liberator pistol was such that it included numerous parts which were not “smoothly” integrated whereby that pistol could be quickly and reliably extricated from a pocket or other concealed location without a likelihood of some portion of the pistol (e.g., an external hammer) catching on the user&#39;s clothing, etc., which feature is especially important in a tactical situation. 
     SUMMARY OF THE INVENTION 
     The present invention is for a trigger mechanism that has a trigger pull, a trigger spring, a pivotal linkage between the trigger pull and a sear which has a cam surface and a guide, a hammer, and a hammer spring. The trigger spring preferably has one end positioned against the firearm frame and a second end extending away from the firearm frame to force the trigger pull out away from the frame. The hammer has a striking end, a bearing end and a pivot point between the striking and bearing ends. The bearing end of the hammer rides up on the cam surface as it moves between different positions relative to the guide. The hammer is pivoted around the pivot point and the striking end is moved from the hammer&#39;s seated position to its cocked position as the cam surface moves between its positions. The hammer spring has one end connected to the firearm&#39;s frame and another end connected to the hammer to provide a hammer spring force. The hammer spring biases the striking end of the hammer to the seated, striking position and the movement of said hammer from the seated position to its rearward position is performed against the hammer spring force. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings. The drawings constitute a part of this specification and include exemplary embodiments of the invention, which may be embodied in various forms. It is to be understood that in some instances, various aspects of the invention may be shown exaggerated or enlarged to facilitate an understanding of the invention; therefore the drawings are not necessarily to scale. In addition, in the embodiments depicted herein, like reference numerals in the various drawings refer to identical or near identical structural elements. 
         FIG. 1  is a side view of the pistol of the preferred embodiment of the present invention; 
         FIG. 2  is a front view (e.g., a muzzle view) of the preferred embodiment of the pistol of the preferred embodiment of the present invention looking into the barrels; 
         FIG. 3  is a top view of the pistol of the preferred embodiment of the present invention; 
         FIG. 4  is a perspective view of the barrel assembly of the pistol of the preferred embodiment of the present invention; 
         FIG. 5  is a side view cutaway view of the pistol of the preferred embodiment of the present invention; and 
         FIG. 6  is a side view cutaway view of the pistol of the preferred embodiment of the present invention with the barrel assembly in the raised position. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     In accordance with the present invention a small, lightweight, two shot pistol  10  is shown in  FIGS. 1-3  and  5 - 6 . With specific reference to  FIGS. 1 ,  5 , and  6 , the pistol  10  includes a removable barrel assembly or receiver  12  which can be pivoted about an axis defined by a retaining member  14  which is a pin held in place by a detent (not shown). The retaining member  14  extends through an opening  16  in the barrel assembly  12  (See,  FIG. 4 ). It can be pushed from one side, to release it from the detent, whereby the barrel assembly  12  can be removed and replaced. A feature of the present invention is that interchangeable barrel assemblies can be used for different caliber cartridges. 
     In accordance with the preferred embodiment of the invention, the pistol  10  includes a single trigger  18 , which is preferably a double action trigger. The receiver  12  (shown in  FIGS. 1-6 ) includes a pair of barrels which preferably have an over/under configuration, including an upper barrel  20  and a lower barrel  22 , as best illustrated in  FIG. 2 . The breech  24  of the pistol  10  preferably includes a spring loaded auto-ejector  26  for receiving two cartridges  28 ,  30  which can be inserted therein when the receiver  12  is in its “tilted forward/open” position, as shown in  FIG. 6 . 
     The pistol  10  further includes a butt, or pistol grip  32  which is designed to receive a pair of spare cartridges  34 ,  36 . In the preferred embodiment of the invention the pistol grip  32  is a machined integral grip, as it is machine processed to provide a pattern or design which emulates a texture, which may include designs or logos, as shown in  FIG. 1 , while being integral with the frame of the pistol  10  to minimize the thickness of the pistol  10 . As shown in  FIGS. 1-2  and  5 - 6 , a trap door  38  is formed at the bottom of the grip  32 . The trap door  38  pivots down from its normally closed position (shown) in order to allow the user to extract the spare cartridges  34 ,  36  from a cartridge trap  40  formed within the grip  32 . As illustrated in  FIGS. 5-6  the spare cartridges  34 ,  36  are press fit into a cartridge loading device  42  (the “Heizer loading device”) which holds the cartridges  34 ,  36  in proper juxtaposition whereby they can be pressed directly into the breech  24  when the barrel assembly is tilted up as in  FIG. 6 . With continued reference to  FIGS. 5 and 6  the cartridge loading device  42  includes a tab  44  which is bent over, as shown, when the cartridge loading device  42  is within the cartridge trap  40 . 
     In the preferred embodiment of the invention a lanyard mount  46  is preferably included on the rear portion of the grip  32 , whereby the pistol  10  may be retained by a lanyard or chain, as desired by the user. 
     Various features of the pistol  10  of the preferred embodiment of the invention are included in order to minimize any likelihood of catching or snagging as the user withdraws the pistol  10  from his pocket or other clothing. Thus, with continued reference to  FIGS. 1-6 , the pistol  10  includes an integrated, low profile sight  48 , which may be comprised of a tritium sight. Another feature which prevents the pistol  10  from catching on a user&#39;s clothing is that it uses an internal hammer  62 , which will be further described hereinafter, and which is fully enclosed within the frame of the pistol  10 . 
     In accordance with the preferred embodiment of the invention, ambidextrous thumb latches  50  (See,  FIGS. 1 ,  5 , and  6 ) are included on each side of the pistol  10 . While only the latch  50  on the left side of the pistol  10  is actually shown, the latch on the right side of the pistol  10  is identical. The design of the thumb latches  50 , along with their associated mechanisms, is such that if either of them is pushed forward (toward the muzzle of the pistol  10 ) it will cause a receiver disconnect push pin  52  to push a receiver lockup pin  54  forward against the force of a latch retainer spring  56 , thereby causing the lockup pin  54  to disengage from a barrel latch  58  formed on the underside of the barrel assembly  12  (See,  FIG. 6 ). When the receiver lockup pin  54  is disengaged from the barrel latch  58  a barrel tip up spring  60  causes the barrel assembly  12  to rapidly tip up, as shown in  FIG. 6 . 
     When the rear of the barrel assembly  12  tips up, the spring-loaded ejector  26  forces the cartridges  28 ,  30  out of the breech  24  as soon as the breech  24  clears the frame. The user can then open the trap door  38  (which is held closed by a detent) and remove the cartridge loading device  42 , which retains the spare cartridges  34 ,  36 , from the cartridge trap  40  within the grip  32 . While holding the tab  44 , the user can quickly reload the pistol  10 , tear the cartridge loading device  42  from the newly loaded cartridges  34 ,  36 , and snap the barrel assembly  12  into its down, locked, and ready position. 
     As set forth above, another feature of the pistol  10  of the preferred invention is that it is designed to have an internal hammer  62  along with a smoothly joined exterior configuration whereby the likelihood of something on the pistol  10  “catching” when the pistol  10  is removed from a concealed location, e.g., from a user&#39;s pocket, is greatly reduced. With reference to  FIGS. 5 and 6 , the operation of the trigger  18  and associated mechanism is that when the trigger  18  is “pulled” against the force of the trigger spring  64 , a trigger linkage  66  moves a sear  68  rearward along a sear guide  70  on which the sear  68  rides. The upper portion of the sear  68  presents a cam surface  72  to the pivoting hammer mechanism  62 , whereby a roller bearing  74  rides up the cam surface  72 , pivoting the hammer  62  rearward around a roller bearing  76  against the force of a hammer spring  78 . When the sear  68  reaches a disconnect  80 , the disconnect  80  is pushed rearward against the force of a disconnect spring  82  until it reaches a point where the disconnect  80  is pushed free of a disconnect block  84 , at which point the sear guide  70  pivots downward about a disconnect pivot  86 , clearing the roller bearing  76 , and allowing the hammer  62  to be driven against firing pin assemblies  88 ,  90 , each of which includes a firing pin which is spring loaded away from the breech until struck by the hammer  62 , at which time a struck firing pin will be driven forward into a cartridge in the breech  24 . In  FIG. 6  the tips of the firing pins are shown extending out of the firing spring assemblies  88 ,  90  for clarity. However, the springs (not shown) within the firing spring assemblies  88 ,  90  would normally prevent the firing pin tips from extending, as they are strong enough to hold the hammer  62  somewhat back from the firing spring assemblies  88 ,  90 . 
     While it is possible to have a single forward movement of the hammer  62  drive the firing pins in each of the firing pin assemblies  88 ,  90  into the cartridges  28 ,  30 , in the preferred embodiment of the invention the hammer  62  has a cylindrical bore formed therein and a firing pin selector, in the shape of a cylinder is positioned within the cylindrical bore. The firing pin selector of the preferred embodiment of the invention (not shown) includes four faces, two of which have a flat portion in juxtaposition with the upper firing pin assembly  88 , and two of which have a flat portion in juxtaposition with the lower firing pin assembly  90 . On each of the faces of the firing pin selector, there is also a convex portion which prevents the firing pin selector from contacting the firing pin assembly  88  or  90  which is not to be struck. Firing pin indexes  92  on the firing pin selector cause the firing pin selector to rotate a quarter of a turn when they engage a yoke (not shown) each time the hammer  62  is brought back to fire the pistol  10 . Thus, on each successive pull of the trigger  16 , the firing pin in either the top firing pin assembly  88  or the firing pin in the bottom firing pin assembly  90 , will be struck, but both will not be struck at the same time. 
     The use of the so-called roller bearing trigger system (so named because of the use of multiple roller bearings  74 ,  76 ) causes the trigger action to be extremely smooth. 
     Further features found in the preferred embodiment of the invention, which are designed to provide both strength and light weight to the pistol  10 , are that the grip  32  is preferably made of a lightweight material, such as aluminum or titanium, while the barrels  20 ,  22  are preferably made of 416 stainless steel, as are the hammer  62  and other internal components. Titanium or aluminum alloy are preferably used to make the frame, with aluminum alloy being lighter and titanium being stronger without adding undue weight to the pistol  10 . 
     A safety feature of the pistol  10  is that there is a space between the rear and the firing pin assemblies  88 ,  90  which provides a positive visual indication of whether the chamber is loaded as the rear of the cartridges are visually exposed. 
     As will be understood by those skilled in the art, many shooters consider the shape and size of the original and subsequent “1911” platform to be ergonomically preferred (so-called “1911 ergonomics”). Thus, the grip in the preferred embodiment of the invention angles back (from the vertical) by 17 degrees, the distance from the rear of the grip  32  (called the “back strap”) to the front of the trigger  18 , and the size and shape of the trigger  18  are in accordance with such  1911  ergonomics. 
     Yet, another feature of the preferred embodiment is that it uses progressively ported barrels which include a series of specifically designed gas venting holes  96 ,  98  in the barrels  20 ,  22 . The purpose of the venting holes  96 ,  98  is that when the pistol  10  is discharged pressurized gases are diverted in specific directions and angles to reduce both recoil and muzzle climb. 
     As set forth above, the pistol  10  of the preferred embodiment includes a pivoting retaining member  14  which is used to attach the receiver  12  to the pistol  10 . In the preferred embodiment of the invention, the pivoting retaining member  14 , which may be in the form of a movable pin, or other suitable form allows the pistol to utilize interchangeable receivers  12 , whereby the superposed double barrel receiver  12  is interchangeable to multiple calibers utilizing the same frame. By way of example, receivers including barrels for available calibers could include .22 caliber, 22 mag, 22hornet, 5.7.times.28 mm, 0.25 mm, .380, 9 mm, 10 mm, .40 S&amp;W, .38 Special, .357 Magnum, .410, 45 ACP, 45 Long Colt, 44 Magnum, 50 S&amp;W Magnum, or such other calibers as may be available or desired without departing from the present invention. 
     While the preferred embodiment of the invention has been described and illustrated, those skilled in the art will recognize that numerous variations of the present invention can be made without departing from the spirit of scope of the invention described and claimed. By way of one example, while the preferred embodiment has a sear assembly which uses a drop block and disconnect rest in combination with the cam surface and guide, alternative arrangements of the cam surface and guide are possible. Thus, it would be within the scope of the invention to have a cam surface and guide in other orientations with different drop block and disconnect rest designs or even a cam surface that moves relative to a guide without having any drop block or disconnect rest.