EP4224108A1

EP4224108A1 - Trigger mechanism of a firearm and a method of triggering a firearm

Info

Publication number: EP4224108A1
Application number: EP23151658.4A
Authority: EP
Inventors: Christoph Schrödl
Original assignee: Sako Oy
Current assignee: Sako Oy
Priority date: 2022-02-04
Filing date: 2023-01-16
Publication date: 2023-08-09
Anticipated expiration: 2043-01-16
Also published as: EP4224108B1; FI20225094A1; FI130229B

Abstract

The invention relates to a trigger mechanism of a firearm, which trigger mechanism (10) comprises a hammer (11), a trigger (12), a disconnector (13), a sear (14), two pivot pins: a front pivot pin (15F) and a central, back pivot pin (15B) , a main spring (16) and two helical springs: a front helical spring (17F) and a back helical spring (17B), and a safety lever (17), which firearm comprises a bolt carrier (20) and a lower receiver (19), and in which the trigger mechanism (10) is located below the bolt carrier (20) and within the lower receiver (19) and the trigger mechanism (10), the bolt carrier (20) and the lower receiver (19) are functionally connected to operate the firearm. The hammer (11) has a back hook (111)with a front part (111F) and a back part (111B), the disconnector (13) comprises a back hook (132), the sear has a retaining hook (142). The front part (111F) of the back hook (111) of the hammer (11) is engageable with a retaining hook (142) of the sear (14). The back part (111B) of the back hook (111) of the hammer (11) is engageable with the back hook (132) of the disconnector (13). The front helical spring (17F) is positioned against the lower receiver (19) and configured to provide first stage force as well as trigger reset and manual cocking functionality in safe mode and the back helical spring (17B) is located between the trigger (12) and the disconnector (13) and is configured to act on the trigger (12) and the disconnector (13).

Description

Technical field

The present invention relates generally to firearms, in particular to trigger mechanisms for firearms, especially for automatic and semi-automatic firearms. More precisely the present invention relates to a trigger mechanism of a firearm according to the preamble part of the independent trigger mechanism claim and to a method of triggering a firearm according to the preamble part of the independent method claim

Background

In firearms is a trigger mechanism for actuating function of the firearm.
In patent publication US10837728B2 is disclosed an assembly for a firearm which includes a safety selector, the firearm having a forward and rearward direction, the assembly comprising a spring loaded hammer that comprises a first hammer sear surface and a hammer edge, a spring loaded trigger rotatable about a pivot axis, the trigger comprising a pulling surface for an operator to pull the trigger in a triggering direction, a front hook rotatable relative to the trigger, wherein the front hook comprises a front hook sear surface, wherein the engagement of the front hook and first hammer sear surfaces with each other maintains the hammer in a cocked condition and wherein the front hook selectively abuts the trigger so that the front hook selectively rotates with the trigger, a rear hook rotatable relative to the trigger, wherein the rear hook comprises a rear hook surface, wherein the rear hook is adapted to selectively abut the trigger so that the rear hook selectively rotates with the trigger and wherein the rear hook surface is adapted to selectively abut the hammer edge to increase the force required to pull the trigger in the triggering direction to release the front hook and first hammer sear surfaces and a hook spring positioned between said front hook and said rear hook which biases the front hook and the rear hook apart. Thus, in this US patent disclosed trigger assembly for a firearm wherein the firearm includes a receiver, a safety selector and a hammer. The trigger assembly includes a trigger having a pivot axis, a front hook which is constructed and arranged to move with trigger rotation, a rear hook which is cooperatively arranged with the front hook and a spring which is positioned between the front hook and the rear hook. The front hook and the trigger are constructed and arranged relative to the safety selector and relative to the hammer in order to allow the hammer to be re-cocked from an upright position with the safety selector in a safe position and in this position the bolt carrier is allowed to fully retract thereby cocking the hammer. A disadvantage of this known assembly is that possible dirt under the seat of the rear hook may cause malfunctioning. Additionally there is a small space for the return spring, which may cause spring set.
In patent application publication US2017089655A1 is disclosed a mode selector element for a trigger mechanism comprising: a selector block defining a first detent recess, a second detent recess, and a ramped surface proximate the second detent recess on a side opposite from the first detent recess; a handle portion extending from the selector block; and a spring biased detent pin; wherein the selector block is rotatable by the handle portion between a first position in which the spring biased detent pin is received into the first detent recess, a second position in which the spring biased detent pin is received into the second detent recess, and a third position in which the spring biased detent pin is engaged with the ramped surface such that the selector block is biased to automatically rotate from the third position to the second position.
In patent publication US9310150B1 is disclosed a trigger mechanism for a firearm comprising: a hammer element operable between a cocked position and a released position, the hammer element including a hammer sear; a trigger element including a trigger sear, the trigger element being moveable between a starting position and a pulled position, wherein when the trigger element is in the starting position the trigger sear is engaged with the hammer sear and holds the hammer element in the cocked position, and wherein when the trigger element is in the pulled position the hammer sear is released from the trigger sear; a plurality of disconnector elements, each configured to interact with the trigger element to provide different pull characteristics, the pull characteristics including at least one of a takeup and a break; and a mode selector element adjustable between a plurality of positions to select between the plurality of disconnector elements and the different pull characteristics, wherein the trigger element includes a trigger body, and the trigger sear includes an extension portion and a hook portion, the extension portion extending from the trigger body, and the hook portion extending from the extension portion.
In patent application publication US2019257606A1 is disclosed a trigger assembly for a firearm which includes a receiver, a safety selector and a hammer, the trigger assembly comprising: a trigger having a pivot axis; a front hook constructed and arranged to move with trigger rotation, wherein the front hook includes a sear surface and the hammer includes a sear surface wherein the engagement of the sear surfaces with each other maintains the hammer in a cocked condition; a rear hook cooperatively arranged with the front hook; a spring positioned between the front hook and the rear hook; and wherein the front hook and the trigger are constructed and arranged relative to the safety selector and to the hammer to allow the hammer to be recocked from an upright position with the safety selector in a "SAFE" position.
In patent publication US9970723B1 is disclosed a trigger mechanism for a firearm, said trigger mechanism comprising: a sear mounted on said firearm for pivoting motion about a sear pivot point, said sear having an action surface and a sear locking surface thereon; a trigger pivotably mounted on said firearm, said trigger having a contact surface movable into and out of engagement with said action surface of said sear upon pivoting motion of said trigger; a sear block mounted on said trigger for pivoting motion about a sear block pivot point, said sear block comprising a finger engaging surface positioned on a first side of said sear block pivot point and a sear dog positioned on a second side of said sear block pivot point, said sear dog being movable into and out of engagement with said sear locking surface upon pivoting motion of said sear block, said sear pivot point and said sear block pivot point being aligned co-linearly with a point of contact between said sear dog and said sear locking surface when said sear dog engages said sear locking surface; wherein engagement between said sear dog and said sear locking surface prevents pivoting motion of said trigger.
An object of the present invention is to create a trigger mechanism of a firearm by which the above described problems and disadvantages of trigger mechanism of a firearm known from prior art are eliminated or at least minimized.
An object of the present invention is to create a trigger mechanism of a firearm, which fulfills the requirements of safety in Europe.
Another object of the present invention is to create an improved trigger mechanism of a firearm and a method of triggering a firearm, in which trigger movement during manual hammer cocking in safe mode is prevented.
Another object of the present invention is to create an improved trigger mechanism of a firearm and a method of triggering a firearm, which are suitable for the two-stage trigger functionality in the semi-automatic firing mode as well as for the single-stage trigger functionality in the fully automatic mode.
Another object of the present invention is to create an improved trigger mechanism of a firearm and a method of triggering a firearm, which provide firearm manipulation with engaged safety during the whole triggering sequence.
Another object of the present invention is to create an improved trigger mechanism of a firearm and a method of triggering a firearm, which are suitable for all AR (automatic rifle) -type and for SAR (semiautomatic rifle) - type firearms.
Another object of the present invention is to create an improved trigger mechanism of a firearm and a method of triggering a firearm, which provide increased drop-safety in case of accidental fall.

Summary

In order to achieve the above objects and those that will come apparent later the trigger mechanism of a firearm is mainly characterized by the features of the characterizing part of the independent trigger mechanism claim. The method of triggering a firearm, in turn, is mainly characterized by the features of the characterizing part of the independent method claim
Dependent claims present advantageous features and embodiments of the invention.
According to the invention the trigger mechanism of a firearm comprises a hammer, a trigger, a disconnector, a sear, two pivot pins: a front pivot pin and a central, back pivot pin, a main spring and two helical springs: a front helical spring and a back helical spring, and a safety lever, which firearm comprises a bolt carrier and a lower receiver, and in which the trigger mechanism is located below the bolt carrier and within the lower receiver and the trigger mechanism, the bolt carrier and the lower receiver are functionally connected to operate the firearm, wherein the hammer has a back hook with a front part and a back part, the disconnector comprises a back hook, the sear has a retaining hook, the front part of the back hook of the hammer is engageable with a retaining hook of the sear, the back part of the back hook of the hammer is engageable with the back hook of the disconnector, the front helical spring is positioned against the lower receiver and configured to provide first stage force and trigger reset and manual cocking functionality in safe mode, and the back helical spring is located between the trigger and the disconnector and is configured to act on the trigger and the disconnector.
According to an advantageous feature of the invention the disconnector has a recess for the upper end of the back helical spring, the back helical spring is located in a through-hole of the sear.
According to an advantageous feature of the invention the back helical spring is supported by an additional cylindrical spring guide surface of the sear.
According to an advantageous feature of the invention the lower end of the back helical spring is supported on the inner bottom surface of the trigger and retained by a recess in the sear concentrically arranged to the through-hole.
According to an advantageous feature of the invention the front helical spring is located in a recess, which is closed at its upper end of the sear and the lower end of the front helical spring is supported on the lower receiver.
According to an advantageous feature of the invention the sear comprises a retaining hook with a widened rest.
According to an advantageous feature of the invention the sear comprises a retaining hook with a widened rest provided with a nose with round geometry.
According to the invention the sear comprises balancing mass parts and the trigger comprises a recess on upper surface of the trigger configured to complement form of the balancing mass parts.
According to an advantageous feature of the invention the sear comprises an inclined extension configured to prevent spring setting and damage to the back helical spring induced by excessive disconnector rotation.
According to an advantageous feature of the invention the trigger has a front support surface and an inner bottom surface of the trigger, the front end of the disconnector is engageable with the front support surface of the trigger and the back support surface is engageable with the safety lever.
According to an advantageous feature of the invention the main spring has two lower arms, a U-shaped part and a helical part, the helical part of the main spring is located around the front pivot pin, the U-shaped part of the main spring rests against the hammer, and the lower arms of the main spring rest on the back pivot pin of the trigger.
According to an advantageous feature of the invention the trigger mechanism is suitable for a firearm with a semi-automatic firing mode and for a firearm with a fully automatic firing mode.
According to the invention the method of triggering a firearm by a trigger mechanism, which method comprises stages: the firearm is safe and ready to fire, the firearm is discharged and in cycling operation stage, the firearm is manually cocked, whereby in the stage of method of triggering by the trigger mechanism in which the firearm is safe and ready to fire the safety lever is engaged to a back support surface of the trigger and a hammer of the trigger mechanism is fully cocked as the hammer and a sear of the trigger mechanism are fully engaged and as a retaining hook of the sear for front part of the back hook of the hammer are engaged and a front helical spring of the trigger mechanism and the back helical spring of the trigger mechanism are in the rest position and a front end of a disconnector of the trigger mechanism rests on a front support surface of the trigger, whereby in the stage of the method of triggering by the trigger mechanism, in which the firearm is discharged and in cycling operation stage, the safety lever is disengaged and the hammer is being cocked by return moment of a bolt carrier of the firearm in the cycling operation, the back support surface of the trigger stops against recess in safety lever and the trigger is in a stop position, the front helical spring is maximally compressed and the back part of the back hook of the hammer contacts with the back hook of the disconnector, the back helical spring is compressed by downwards movement of the hammer and the disconnector retains the hammer during remainder of the cycling operation, after the trigger has been released to its initial position, the hammer returns to retaining hook of the sear and the trigger is reset and the trigger mechanism has reached its initial setting and the method comprises a stage for manual cocking by the trigger mechanism in a safe mode, in which stage the safety lever is engaged and the hammer and the sear are disengaged, the hammer is being cocked by returning movement of the bolt carrier in manual charging, the trigger is in its resting position on the lower receiver, the back helical spring is in the rest position and the disconnector rests on the trigger, the front part of the back hook of the hammer contacts the retaining hook of the sear, the front helical spring is compressed in proportion to the turning movement of the sear, the sear sets into the position, in which the sear is positioned against the trigger and retains the hammer.
According to an advantageous aspect in the trigger mechanism standard type trigger spring assembly is used and thus logistics and maintenance are simplified.
According to an advantageous aspect in the trigger mechanism standard type of hammer and pivot pins are used, which also improves logistics and maintenance.
According to an advantageous aspect in the trigger mechanism extremely light sear achieved by its design is used and the sear is additionally balanced around the center (back) pivot pin. Thus, increased drop-safety in case of an accidental fall of the firearm is achieved. The trigger mechanism is preferably made of preferably steel but also for example titanium can be used.,
According to an advantageous aspect in the trigger mechanism by the mainspring torque additional secondary drop-safety is achieved in case of accidental fall. As in order to discharge the hammer, the sear needs to further increase spring torque above the amount of fully cocked condition - for example 1 Nm - which is highly unlikely without destroying the entire firearm.
In this description the terms, back, front, upper, lower etc. are used as reference to the normal position of a firearm, when used for firing. They are not to have any as such limiting effect.
By the trigger mechanism according to the invention and its advantageous features several advantages are achieved:
The firearm is safe and secured but it can be manually cocked as it is secured that the firearm cannot be accidentally fired. Firearm manipulation with engaged safety during the whole triggering sequence (loading, cocking etc.) is provided. The trigger mechanism provides semiautomatic as well as fully automatic firing characteristics for AR-style firearms due to the advantageous drop-in type of the trigger mechanism according to the invention.. Additionally, the trigger mechanism provides the two-stage trigger functionality in the semi-automatic firing mode and the single-stage trigger functionality in the fully automatic firing mode. The trigger mechanism also provides for increased drop-safety in case of accidental fall. Further safety is improved as there is no trigger movement during the manual hammer cocking in the safe mode. Also, easy and fine adjustment of the trigger reset and the pretravel are provided due to the helical spring. Additionally, the sear surface is enhanced (wider), which provides for increased part endurance

Brief description of the drawings

In the following the invention and its advantages are explained in greater detail below in the sense of example and with reference to accompanying drawing, where

In figure 1 is schematically shown an advantageous example of a trigger mechanism according to the invention for semi-automatic firing.
In figure 2A-2C is schematically shown an advantageous example of a main spring, a hammer, a trigger and pivot pins of an advantageous example of a trigger mechanism according to the invention for semi-automatic firing.
In figures 3A-3C is schematically shown an advantageous example of a disconnector and of a sear of an advantageous example of a trigger mechanism according to the invention for semi-automatic firing.
In figures 4A-4E is schematically shown function stages of an advantageous example of a trigger mechanism according to the invention for semi-automatic firing.
In figure 5 is schematically shown another advantageous example of a trigger mechanism according to the invention for fully automatic firing.
In figure 6A and 6B is schematically shown a sear assembly and a trigger for an advantageous example of a trigger mechanism according to the invention for fully automatic firing.
In figures 7A and 7B is schematically shown function stages of an advantageous example of a trigger mechanism according to the invention for fully-automatic firing.

Detailed description

During the course of the following description like numbers and signs will be used to identify like elements according to the different views which illustrate the invention and its advantageous examples. In the figures some repetitive reference signs may have been omitted for clarity reasons.
In the figure 1 is shown schematically an advantageous example of a trigger mechanism 10 for semi-automatic firing mode with two-stage trigger functionality. The trigger mechanism 10 comprises a hammer 11, a trigger 12, a disconnector 13, a sear 14, two pivot pins: a front pivot pin 15F and a central, back pivot pin 15B , a main spring 16 and two helical springs: a front helical spring 17F and a back helical spring 17B. The hammer 11 has a back hook 111 with a front part 111F and with a back part 111B. The front part 111F of the back hook 111 of the hammer 11 is engageable with a retaining hook 142 of the sear 14 and the back part 111B of the back hook 111 of the hammer 11 is engageable with a back hook 132 of the disconnector 13. The disconnector 13 has a front end 131 of the disconnector 13, which front end 131 is engageable with a front support surface 121 of the trigger 12. The trigger 12 has a back support surface 122, which is engageable with the safety lever 18. The trigger mechanism 10 has the front pivot pin 15F, which is turnable. Around and in connection with the front pivot pin 15F the main helical spring 16 is positioned. The main spring 16 comprises two lower arms 16L and a U-shaped part 16U. The lower arms 16L extend substantially backwards from the front pivot pin 16F around which a helical part 16H of the main spring 16 is positioned. The U-shaped part 16U of the main spring 16 rests against the hammer 11 and thereby transmits moment to it. The lower arms 16L of the main spring 16 rest on the pivot pin 15B of the trigger 12. The hammer 11 is engageable to the sear 14 and to the disconnector 13. The disconnector 13 is engageable to the hammer 11, to the sear 14 and to the trigger 12 via the back helical spring 17B. The disconnector 13 has a recess 133 for the upper end of the back helical spring 17B. The disconnector 13 is turnable around the back (center) pivot pin 15B such, that its turning movement either compresses or releases the compression of the back helical spring 17B. The lower end of the back helical spring 17B rests inside the trigger 12 and is supported on the inner bottom surface 123 of the trigger 12. The back helical spring 17B is located in a through-hole 141 of the sear 14 and supported by an additional cylindrical spring guide surface 145. The front helical spring 17F is located in a recess, which is closed at its upper end, of the sear 14. The lower end of the front helical spring 17F is supported on the lower receiver 19.
In figure 2A-2C is schematically shown an example of the main spring 16, the hammer 11, the trigger 12 and the pivot pins 15F, 15B. The hammer 11 comprises the back hook 111 comprising the front part 111F and the back part 111B. The main spring 16 comprises the two lower arms 16L and the U-shaped part16U and the helical part 16H. The trigger 12 comprises the front support surface 121 and the back support surface 121. The trigger 12 comprises a recess 125 on upper surface of the trigger 12.
In figures 3A-3C is schematically shown an example of the disconnector 13 and the sear 14 of the trigger mechanism 10. The sear 14 has a through-hole 141 for the back helical spring 17B. The sear 14 also has a widened rest 142W in the retaining hook 142 for the hammer 11, which decreases component stress. The widened rest 142W for the hammer 11 also is provided with a nose 142R with round geometry. The sear 14 also comprises a recess 143 for the front helical spring 17F and a recess 144 concentrically arranged to the through-hole 141 for retaining the front helical spring 17F. The sear 14 has as cocking surfaces the surface of the widened rest 142W and the spring support surface 145, which functions as a cylindrical concentric surface to the trough-hole 141 of the sear 14 and guides the back helical spring 17B. The sear 14 also comprises balancing mass parts 146 of the sear 14, which are located under a pivot pin hole 147. The balancing mass parts 146 of the sear 14 provide for the center mass balancing of the sear 14 onto axis of the back pivot pin 15B. The trigger 12 comprises a recess 125 (fig. 2C) on upper surface of the trigger 12 configured to complement form of the balancing mass parts 146. The sear 14 further comprises an inclined extension 148 configured to act as a spring setting for the back helical spring 17B to prevent over-compressing of back helical spring 17B.The disconnector 13 comprises the front end 131 and the back hook 132.
In the trigger mechanism 10 is no trigger movement during manual hammer 11 cocking in the safe mode, as explained in more detail in connection with figure 4.
The main spring 16 and the helical springs 17F, 17B can be of standard/typical trigger spring assembly as the main spring 16 can be used independent of trigger mechanism type (e.g. it can also be used in standard direct trigger or standard two-stage trigger) and the helical springs 17F, 17B can be standard disconnector springs, which can be ordered as standard AR spare parts if needed and thus, logistics of the trigger mechanism 10 manufacturing and maintenance of the trigger mechanism 10 is simplified.
The torque of the main spring 16 provides improved drop-safety in case of an accidental fall. As in order to discharge the hammer, the sear needs to further increase spring torque above the amount of fully cocked condition - for example 1Nm - which is highly unlikely without destroying the entire firearm.
The sear 14 is advantageously extremely light primarily through its special design: there is almost no massive material parts but mostly hollow cavities e.g. the recess 143 for the front helical spring 17F, the through-hole 141 and the center section and it is balanced around the back, center pivot pin 15B and thus increased drop-safety is achieved in case of an accidental fall. The front helical spring 17F is responsible for the "first stage" force, for the trigger reset after shot has been fired and for the manual cocking in safe mode (Fig. 4E). The back helical spring 17B is responsible for the additional second stage force and the disconnector functionality. The back helical spring 17B thus corresponds in its function to known two-stage trigger mechanisms.
The trigger mechanism 10 provides firearm manipulation with engaged safety in its function stages: loading, cocking etc. The trigger mechanism is usable as a drop-in part for all AR style weapons with semiautomatic and fully automatic firing modes.
In figures 4A-4E is schematically shown function stages of the example of a trigger mechanism 10 shown in the figures for two-stage trigger functionality for a semi-automatic firing mode. In this example of figures 4A-4B a 60° setting is used for the safety lever 18. Alternatively, a 90° setting can be used.
In figure 4A is shown the stage for the trigger mechanism 10, in which the firearm is safe and ready to fire. In figure 4B is shown the stage for the trigger mechanism 10, in which the safety lever 18 blocks the trigger 12. In figure 4C is shown the stage for the trigger mechanism 10, in which the firearm is ready-to-fire and the trigger mechanism is in the first stage of the two-stage trigger functionality. In figure 4D is shown the stage for the trigger mechanism 10, in which the firearm is discharged and in cycling operation stage. In figure 4E is shown the stage for the trigger mechanism 10 for manual cocking in the safe mode.
In figure 4A is shown the stage for the trigger mechanism 10 in which the firearm is safe and ready to fire. In this stage the safety lever 18 is engaged to the back support surface 122 of the trigger 12 and the hammer 11 is fully cocked. The hammer 11 and the sear 14 are fully engaged as the retaining hook 142 of the sear 14 for front part 111F of the back hook 111 of the hammer 11 are engaged. In this stage the front helical spring 17F and the back helical spring 17B are in the rest position and pre-compressed and consequently resting forces are acting on the parts at all times. The front end 131 of the disconnector 13 rests on the front support surface 121 of the trigger 12. Thus, the trigger 12 cannot directly operate the hammer 11.
In figure 4B is shown the stage for the trigger mechanism 10, in which the safety lever 18 blocks the trigger 12 and the safety lever 18 is engaged. At this stage the hammer 11 is fully cocked and the trigger 12 is blocked and it cannot disengage the hammer 11 by means of the sear 14. The back helical spring 17B is at this stage in the rest position and the front helical spring 17F is compressed in proportion to movement of the trigger 12. The front end 131 of the disconnector 13 rests on the front support surface 121 of the trigger 12. The hammer 11 and the sear 14 are partially engaged as the retaining hook 142 of the sear 14 for the back hook 111 of the hammer 11 are only partially engaged.
In figure 4C is shown the stage for the trigger mechanism 10, in which the firearm is ready-to-fire and the trigger mechanism 10 is in the first stage of the two-stage trigger functionality for the semi-automatic firing mode. At this stage the safety lever 18 is disengaged and the hammer 11 is fully cocked. In this first stage of the two-stage trigger function pretravel of the trigger 12 is removed and any incremental force on the trigger 12 will discharge the hammer 11. The back helical spring 17B is still in the rest position at this stage and any further travel of the trigger 12 compresses the back helical spring and initiates a second stage of the two-stage trigger function. The second stage is principally the additional force required in excess of the first-stage force in order to disengage the hammer 11. The front helical spring 17F is compressed in proportion to movement of the trigger 12 by means of the sear 14. The front end 131 of the disconnector 13 rests on the front support surface 121 of the trigger 12 and on the back hook 111 of the hammer 11. The hammer 11 and the sear 14 are partially engaged as the retaining hook 142 of the sear 14 for the back hook 111 of the hammer 11 are only partially engaged.
In figure 4D is shown the stage for the trigger mechanism 10, in which the firearm is discharged and in cycling operation stage. The safety lever 18 is disengaged and the hammer 11 is being cocked by return moment of the bolt carrier 20 in the cycling operation. Thus, the back support surface 122 of the trigger 12 stops against recess in safety lever 18 and thus the trigger 12 is in a stop position. The front helical spring 17F is maximally compressed and the back part 111B of the back hook 111 of the hammer 11 is contacting the front part 132F of the back hook 132 of the disconnector 13. The back helical spring 17B is being compressed by downwards movement of the hammer 11 and the disconnector 13. At this stage the disconnector 13 retains the hammer 11 during remainder of the cycling operation. Releasing the trigger 12 forward towards its initial position, returns the hammer 11 to retaining hook 142 of the sear 14 and thus the trigger 12 is reset and the trigger mechanism 10 has again reached its initial setting.
In figure 4E is shown the stage for the trigger mechanism 10 for manual cocking in the safe mode. At this stage the safety lever 18 is engaged and the hammer 11 and the sear 14 are disengaged. The hammer 11 is being cocked by returning movement of the bolt carrier 20 in manual charging. The trigger 12 is in its resting position on the lower receiver 19. The back helical spring 17B is in the rest position and the disconnector 13 rests on the trigger 12. The front part 111F of the back hook 111 of the hammer 11 contacts the preferably round geometry on top of the retaining hook 142 of the sear 14. The front helical spring 17F is compressed in proportion to the turning movement of the sear 14. At the end of this stage the sear 14 sets into the position, in which it 14 is positioned against the trigger 12 and retains the hammer 11.
In figure 5 is shown schematically an advantageous example of a trigger mechanism 10 for fully automatic firing mode with single-stage trigger functionality. The trigger mechanism 10 comprises substantially the same components, parts and functions as the trigger mechanism for the semi-automatic firing mode as described above in connection with description of the figures 1-4E and as shown in figures 1-4E. Additionally, the trigger mechanism 10 for the fully automatic firing mode comprises a rear notch 112 in the hammer 11 and a back notch 124 of the trigger 12. The disconnector 13 comprises an extension 134 inside the back notch 124 of trigger 12. The lower end of the back helical spring rests inside the trigger 12 on the inner bottom surface 123 of the trigger 12. This embodiment of the trigger 10 also comprises an additional sear assembly 24 to function with the sear 14. The sear assembly 24 comprises a torsion spring 241 with a spring arm 241A and a helical part 241H. The helical part 241H of the torsion spring 241 is located around a pivot pin 242. The sear assembly 24 also comprises a sear plate 243.
In figure 6A is schematically shown a sear assembly 224 of the trigger mechanism 10 for fully automatic firing mode. The sear assembly 24 comprises a torsion spring 241 with a spring arm 241A and a helical part 241H. The helical part 241H of the torsion spring 241 is located around a pivot pin 242. The sear assembly 24 also comprises a sear plate 243.
In figure 6B is schematically shown a trigger for fully automatic firing mode. The trigger 12 comprises the front support surface 121, the back support surface 121 and the back notch 124 extends through the center of the trigger 12.
In figures 7A and 7B is schematically shown function stages of an advantageous example of a trigger mechanism 10 for fully-automatic firing mode. In figure 7A the trigger mechanism 10 is with the safety on and in figure 7B in firing mode. A 90° setting is used for the safety lever 18. Also 60° can be used.
In figure 7A the trigger mechanism 10 is with the safety on. In this stage the safety lever 18 is engaged to the back support surface 122 of the trigger 12 and the hammer 11 is fully cocked. The hammer 11 and the sear 14 are fully engaged as the retaining hook 142 of the sear 14 for front part 111F of the back hook 111 of the hammer 11 are engaged. In this stage the front helical spring 17F and the back helical spring 17B are in the rest position and pre-compressed and consequently resting forces are acting on the parts at all times. The front end 131 of the disconnector 13 rests on the front support surface 121 of the trigger 12. The sear assembly 24 is disengaged and rests against the safety lever 18. The bolt carrier 20 is in its foremost position (and the bolt is locked). The hammer 11 is fully cocked and the hammer 11 and the sear 14 are fully engaged. The trigger mechanism 10 can be safely cocked as explained in the description of figure 4E and shown in the figure 4E.
In figure 7B the trigger mechanism 10 is in the firing mode. The safety lever 18 is turned to fully automatic firing mode i.e. 180° from the safe position shown in figure 7A. Disconnector 13 is disengaged by safety lever 18 and thus, it cannot retain the hammer 11 as in the semi-automatic firing mode (figure 4D). Instead the sear assembly 24 is enabled by a recess in the safety lever 18 and it engages with the rear notch 112 of the hammer 11 after a shot has been released. The sear 14 and the hammer 11 cannot engage due to pressing of the trigger 12. The hammer 11 is fully cocked and ready for discharge by the bolt carrier 20 on its movement forward during the cycling operation. The front helical spring 17F and the back helical spring 17B are maximally compressed.
The fully automatic firing operation will continue as long as the trigger 12 is kept in the back position and cartridges are available from the magazine. The resetting of the trigger 12 into its front position will again engage the hammer 11 and the sear 14 and thus, the fully automatic firing is instantly stopped.
In the description in the foregoing, although some functions and elements have been described with reference to certain features and examples, those functions and elements may be performable by other features and examples whether described or not. Although features have been described with reference to certain embodiments or examples, those features may also be present in other embodiments or examples whether described or not.
Above only some advantageous examples of the inventions have been described to which examples the invention is not to be narrowly limited and many modifications and alterations are possible within the invention.

Reference signs used in the drawing:

10 trigger mechanism
11 hammer
111 back hook of the hammer
111F front part of the back hook of the hammer
111B back part of the back hook of the hammer
112 rear notch of the hammer
12 trigger
121 front support surface of the trigger
122 back support surface of the trigger
123 inner bottom surface of the trigger
124 back notch of the trigger
125 recess on upper surface of the trigger
13 disconnector
131 front end of the disconnector
132 back hook of the disconnector
133 recess of the disconnector
134 extension of the disconnector
14 sear
141 through-hole of the sear
142 retaining hook of the sear
142W widened rest of the retaining hook
142R nose of the retaining hook
143 recess of the sear
144 recess of through-hole of the sear
145 spring support surface of the sear
146 balancing mass parts of the sear
147 pivot pin hole of the sear
148 inclined extension of the sear
15F pivot pin, front
15B pivot pin, back
16 main spring
16U upper arm of the main spring
16L lower arm of the main spring
16H helical part of the main spring
17F helical spring, front
17B helical spring, back
18 safety lever
19 lower receiver
20 bolt carrier
24 sear assembly
241 torsion spring
241A spring arm of the torsion spring
241H helical part of the torsion spring
242 pivot pin
243 sear plate

Claims

Trigger mechanism of a firearm, which trigger mechanism (10) comprises a hammer (11), a trigger (12), a disconnector (13), a sear (14), two pivot pins: a front pivot pin (15F) and a central, back pivot pin (15B), a main spring (16) and two springs: a front spring (17F) and a back helical spring (17B), and a safety lever (18), which firearm comprises a bolt carrier (20) and a lower receiver (19), and in which the trigger mechanism (10) is located below the bolt carrier (20) and within the lower receiver (19) and the trigger mechanism (10), the bolt carrier (20) and the lower receiver (19) are functionally connected to operate the firearm, in which
- the hammer (11) has a back hook (111) with a front part (111F) and a back part (111B),

- the disconnector (13) comprises a back hook (132),

- the sear has a retaining hook (142),

which front part (111F) of the back hook (111) of the hammer (11) is engageable with a retaining hook (142) of the sear (14),

which back part (111B) of the back hook (111) of the hammer (11) is engageable with the back hook (132) of the disconnector (13),

which front spring (17F) is positioned against the lower receiver (19) and configured to provide first stage force and trigger reset and manual cocking functionality in safe mode and

which the back helical spring (17B) is located between the trigger (12) and the disconnector (13) and is configured to act on the trigger (12) and the disconnector (13), characterized in that the front spring (17F) is a helical spring and that the sear (14) comprises balancing mass parts (146) and that the trigger (12) comprises a recess (125) on upper surface of the trigger (12) configured to complement form of the balancing mass parts (146).
Trigger mechanism according to claim 1, characterized in that the disconnector (13) has a recess (133) for the upper end of the back helical spring (17B), that the back helical spring (17B) is located in a through-hole (141) of the sear (14).
Trigger mechanism according to claim 1 or 2, characterized in that the back helical spring (17B) is supported by an additional cylindrical spring guide surface (145) of the sear (14).
Trigger mechanism according to any of claims 1 - 3, characterized in that the lower end of the back helical spring (17B) is supported on the inner bottom surface (123) of the trigger (12) and retained by a recess (144) in the sear (14) concentrically arranged to the through-hole (141).
Trigger mechanism according to any of claims 1 - 4, characterized in that the front helical spring (17F) is located in a recess, which is closed at its upper end of the sear (14) and that the lower end of the front helical spring (17F) is supported on the lower receiver (19).
Trigger mechanism according to any of previous claims, characterized in that the sear (14) comprises a retaining hook (142) with a widened rest (142W).
Trigger mechanism according to any of previous claims, characterized in that the sear (14) comprises a retaining hook (142) with a widened rest (142W) provided with a nose (142R) with round geometry.
Trigger mechanism according to any of previous claims, characterized in that the sear comprises an inclined extension (148) configured to prevent spring setting and damage to the back helical spring (17B) induced by excessive disconnector (13) rotation.
Trigger mechanism according to any of previous claims, characterized in that the trigger (12) has a front support surface (121) and an inner bottom surface (123) of the trigger (12), that the front end (131) of the disconnector (13) is engageable with the front support surface (121) of the trigger (12), and that the back support surface (122) is engageable with the safety lever (18).
Trigger mechanism according to any of previous claims, characterized in that the main spring (16) has two lower arms (16L), a U-shaped part (16U) and a helical part (16H), that the helical part (16H) of the main spring is located around the front pivot pin (15F), that the U-shaped part (16U) of the main spring (16) rests against the hammer (11), and that the lower arms (16L) of the main spring (16) rest on the back pivot pin (15B) of the trigger (12).
Trigger mechanism according to any of previous claims, characterized in that the trigger mechanism (10) is suitable for a firearm with a semi-automatic firing mode and for a firearm with a fully automatic firing mode.
Method of triggering a firearm by a trigger mechanism (10), which method comprises stages:
- the firearm is safe and ready to fire,

- the firearm is discharged and in cycling operation stage,

- the firearm is manually cocked,

- in the stage of method of triggering by the trigger mechanism (10) in which the firearm is safe and ready to fire the safety lever (18) is engaged to a back support surface (122) of the trigger (12) and a hammer (11) of the trigger mechanism (10) is fully cocked as the hammer (11) and a sear (14) of the trigger mechanism (10) are fully engaged and as a retaining hook (142) of the sear (14) for front part (111F) of the back hook (111) of the hammer (11) are engaged and a front spring (17F) of the trigger mechanism (10) and the back helical spring (17B) of the trigger mechanism (10) are in the rest position and a front end (131) of a disconnector (13) of the trigger mechanism (10) rests on a front support surface (121) of the trigger (12),

- in the stage of the method of triggering by the trigger mechanism (10), in which the firearm is discharged and in cycling operation stage, the safety lever (18) is disengaged and the hammer (11) is being cocked by return moment of a bolt carrier (20) of the firearm in the cycling operation, the back support surface (122) of the trigger (12) stops against recess in safety lever (18) and the trigger (12) is in a stop position, the front spring (17F) is maximally compressed and the back part (111B) of the back hook (111) of the hammer (11) contacts with the back hook (132) of the disconnector (13), the back helical spring (17B) is compressed by downwards movement of the hammer (11) and the disconnector (13) retains the hammer (11) during remainder of the cycling operation, after the trigger (12) has been released to its initial position, the hammer (11) returns to retaining hook (142) of the sear (14) and the trigger (12) is reset and the trigger mechanism (10) has reached its initial setting and
which method comprises a stage for manual cocking by the trigger mechanism (10) in a safe mode, in which stage the safety lever (18) is engaged and the hammer (11) and the sear (14) are disengaged, the hammer (11) is being cocked by returning movement of the bolt carrier (20) in manual charging, the trigger (12) is in its resting position on the lower receiver (19), the back helical spring (17B) is in the rest position and the disconnector (13) rests on the trigger (12), the front part (111F) of the back hook (111) of the hammer (11) contacts the retaining hook (142) of the sear (14), the front spring (17F) is compressed in proportion to the turning movement of the sear (14), the sear (14) sets into the position, in which the sear (14) is positioned against the trigger (12) and retains the hammer (11), wherein the front spring (17F) is a helical spring and the sear (14) comprises balancing mass parts (146) and the trigger (12) comprises a recess (125) on upper surface of the trigger (12) complementing form of the balancing mass parts (146).