Abstract:
Slides and methods for finishing a lock surface of a slide in a firearm are disclosed. A disclosed method of finishing a lock surface comprising a rearward facing wall adjacent an ejection window of a slide of an automatic firearm includes: (a) pointing a laser at at least one of the lock surface and a material surface bordering the lock surface; and (b) heating the at least one of the lock surface and the material surface bordering the lock surface with a laser beam to harden the lock surface.

Description:
RELATED APPLICATION  
       [0001]     This patent issues from a continuation of International Patent Application Serial No. PCT/EP02/03954, which was filed on Apr. 9, 2002, and which is hereby incorporated by reference in its entirety. 
     
    
     FIELD OF THE DISCLOSURE  
       [0002]     This disclosure relates generally to firearms, and, more particularly, to slides and methods for finishing a lock surface of a slide in a firearm.  
       BACKGROUND  
       [0003]     Throughout this document, positional references refer to a firearm held in a normal firing position, that is, a firearm held in a generally horizontal direction pointing away from the shooter.  
         [0004]     The lateral surface defining the ejection window of an automatic handgun is a substantially flat surface that extends almost vertical to the horizontal firing direction. When referring to this “lateral surface” in this document, we do not refer to a geometrical surface alone, but rather we also refer to a narrow area under this surface. This “surface” must be hard and/or strong enough to resist surface pressure.  
         [0005]     Modem automatic handguns constructed according to the modified Colt-Browning system have a projecting part, (i.e., the so-called lock button), on the top surface of the barrel. When the lock of the slide is closed, the ejection window of the slide is blocked by the barrel from below. When a shot is fired, the recoil pushes the slide backwards, while the barrel is pulled forward due to the friction of the bullet accelerated in it. As a result, the lock (and, thus, the slide) can only open after the bullet has left the barrel, the gas pressure has decreased, and the barrel has moved backwards a bit. This sequence of events occurs, for example, with the newer automatic pistols of Heckler &amp; Koch GmbH, the assignee of this patent.  
         [0006]     During the lock process, considerable force is transferred from the front lateral surface of the ejection window, (i.e. the lock surface), to the lock button of the barrel. The surface pressure experienced by the front lateral surface is even larger when very strong ammunition is employed. This surface pressure can increase even more as the weapon unlocks, since the force-transferring material strips become more and more narrow.  
         [0007]     This force is not a problem for the lock button, since the barrel is coated. (Incidentally, the barrel of standard issue weapons is usually a wear-out part.)  
         [0008]     The slide could also be hardened and then, if necessary, polished around the front lateral surface of the ejection window, (i.e. its lock surface) to increase its tolerance of this force. However, the rust protection coating of the slide would be damaged by such a hardening/polishing process. The slide will only be bronzed after the hardening process, since the weapon would otherwise have an open, irregular, shiny spot on its top side that would not only be unsightly, but could also rust.  
         [0009]     Modern standard issue weapons are usually nitrocarburized and then oxidized, whereby a black, extraordinarily hard, rust resistant protection coating is achieved. This coating is considerably more resistant to abrasion and chemicals than bronzing. However, this process takes place at such a high temperature that, if the lock surface was previously hardened, the material structure of the lock surface would be damaged by the thermal blackening treatment. An additional hardening, (i.e., a hardening after this blackening treatment), is also not appropriate, since this would discolor the blackening layer in the hardening area. A portion of the blackening layer would also be removed through the polishing process which is usually needed after the hardening. For example, if the material is warped, the polishing process should recreate the exact geometry of the lock surface, because even a slight warping could lead to the hardened lock surface no longer having a close fit with the lock button. This polishing process could, thus, reduce the supporting surface and thereby increase the surface pressure experienced by the remaining material when a shot is fired. Such a result would negate the effect sought by the hardening.  
         [0010]     In fact, one part of the slide is already hardened and then polished, but this part is located inside the weapon and is, therefore, not visible from the outside. Thus, its discoloration does not matter. The heat treatment of the area to be hardened does not damage the outer rust protection coating, since the area to be hardened and the areas coated with rust protection on the outer surface are located too far apart.  
         [0011]     In the past, it has been possible to successfully avoid damage to the unhardened lock surface by using high-quality polishing material, widening the slide and, thus, the lock surface, and/or increasing the wall strength of the slide on the lock surface. However, if unusually strong ammunition is used, visible deformations could still appear after a very high number of shots. Further widening of the slide to address this issue could make the weapon heavy and bulky. Further increasing the slide wall strength also causes construction problems. Also, using a higher quality material than what is already currently used would hardly be possible and would be, in any case, too costly.  
         [0012]     It would be possible to use a stop made of hardened spring steel as the lock surface. But this solution would be difficult and costly. It would also be possible to perform induction hardening of the slide edge from below with simultaneous cooling of the already finished topside of the slide and later polishing and deburring of the lock surface. However, slightly visible discolorations on the topside of the slide might occur in this process. This process would also be rather expensive. Nonetheless, the aforementioned discoloration problem could be solved with a state-of-the-art procedure, and the high costs and other disadvantages could perhaps be minimized.  
         [0013]     Using laser hardening in weapons technology is already known from DE 199 18 794 A1 (Rheinmetall). However, the known case concerns the hardening of a layer of the inner surface of the barrel with the help of a revolving mirror inserted into the barrel. The layer hardened in this manner is then coated with a hard metal layer and is, thus, invisible. Warping will not occur, because the surface to be hardened is axially symmetrical.  
         [0014]     A process for chromium-plating the outer surface of the barrel of an M 1911, M 1911 A1 or similar US military pistol is described in U.S. Pat. No. 3,110,223. The lock buttons of the barrel are also chromium-plated.  
         [0015]     As in DE 199 18 194 A2, a process for laser-hardening the inner surface of a barrel is also described in U.S. Pat. No. 5,664,359. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]      FIG. 1  is a partially cut-away, side view of a partially opened slide of an automatic pistol.  
         [0017]      FIG. 2  is an enlarged illustration of area II of  FIG. 1 . 
     
    
     DETAILED DESCRIPTION  
       [0018]      FIG. 1  illustrates an example slide  1  of an automatic pistol. (The direction of firing points to the left in  FIG. 1 .) The slide  1  consists mainly of a high-alloy steel such as 42 CrMoS4 and has, due to heat treatment, a blackened outer surface  3 . Its upper slide wall  9  defines an upward-pointing ejection opening  4 . The ejection opening  4  is bordered toward the front by a vertical lock surface  5 . The lock surface  5  of the illustrated example extends perpendicularly to the direction of fire. The lock surface  5  engages a complementary lock button of a barrel (not shown) when the pistol is ready to be fired. The height of the lock surface  5  is preferred regardless of the thickness of upper slide wall  9 .  
         [0019]     As shown in  FIG. 2 , the lock surface  5  is located forward of the ejection opening  4  of the slide  1 .  
         [0020]     After final completion of the slide  1 , (including the final blackening of its outer surface  3 ), the slide  1  is clamped and a known type of laser is arranged so that its laser beam is directed toward the slide  1  in the direction of arrow  15  in  FIG. 2 . The laser is then shifted perpendicularly to the focal plane; preferably at a rate of 100 mm per minute. The average power of the laser is preferably a few hundred Watts (W), the impulse duration of the laser is preferably a few milliseconds (ms), and the frequency of the laser is preferably approximately 100-150 Hertz (Hz).  
         [0021]     This finishing process leaves no detectable marks on the outside surface  3  of the slide  1 . It also results in a gusset-shaped hardened area  11  in the material of the upper slide wall  9 . The hardened area  11  is bordered in the front by the slanted, clearly outlined, flat transition area  13 . The hardened area  11  is bordered toward the back by the lock surface  5 . The hardened area  11  is bordered toward the bottom by the lower surface  7  of the upper slide wall  9 . The slide material  4  in the laser-hardened, gusset-shaped area  11  is a fine-structured, martensitic structure.  
         [0022]     Although the above description referred in particular to an automatic pistol, the teachings of this disclosure may be applied to any automatic weapon for which an overstrained surface needs to be subsequently hardened.  
         [0023]     From the foregoing, persons of ordinary skill in the art will appreciate that the above disclosed methods provide a process for finishing a lock surface  5  of an automatic handgun, wherein the lock surface  5  already has its final form. In particular, the example methods disclosed above are applicable to finishing the lock surface  5  that is formed by the front lateral surface of the ejection window  4  of the slide  1  of an automatic handgun (i.e., the surface bordering the ejection window  4  and facing toward the back of the firearm). The lock surface  5  and/or the adjoining material surface is finished by coating it with a hardening laser beam.  
         [0024]     This laser beam can be set to emit relatively low energy. Because of its high concentration, it causes sufficient heating in a narrow area. The laser beam, thus, creates a high temperature at its point of impact that is sufficient for hardening, but that decreases extremely quickly outside of this area. The material surrounding the point of impact quickly dissipates the heat. This happens so quickly that tempering is not required. Unexpectedly, no warping of the lock surface  5  occurs.  
         [0025]     In the disclosed example, the laser beam is pointed directly at the lock surface  5  to be hardened. If the laser beam only touches one line running within the lock surface  5 , then the thereby created hardening decreases quickly on both sides. On the other hand, if it touches the entire lock surface  5  to be hardened, then the lock surface  5  can overheat and cool too slowly. The result would be an undefined crystal mixture in the material.  
         [0026]     However, it has been determined that a laser beam causes very good hardening of the lock surface  5  if the point of impact of the laser runs along the bottom edge of the lock surface (i.e., the corner formed by the generally vertical surface  5  and the bottom surface  7 ). This area of impact is heated considerably so that, as a result of this heating, hardening can occur. Due to the sharp edge, significant heating occurs rapidly. As soon as the laser beam is no longer present, the corner immediately cools and hardens.  
         [0027]     The area  11  hardened in this manner can be very narrow. Despite the uneven heating, the material does not warp. Rather, the lock surface  5  retains its shape and, thus, requires no additional finishing.  
         [0028]     The laser beam is preferably aimed at an angle sloping toward the lock surface  5 . For example, it is preferred that the laser beam be aimed at an angle of approximately 45° relative to a line extending downward and parallel to the lock surface  5  (see  FIG. 2 ). It is particularly advantageous if the laser beam hits the lower edge of the lock surface  5  from behind and below (wherein the slide  1  lies horizontal as when closing and the direction of firing is forward).  
         [0029]     At most, the laser beam leaves behind an unobtrusive slash-like marking on the material surface that it hits. However, if this material surface was previously treated with a rust protectant, then the rust protection layer will be damaged or destroyed by the laser beam. It is, thus, preferred that the laser beam be pointed at a material surface that is not visible from the outside of the weapon. The outer surface  3  of the slide  1 , which is located opposite from the material surface engaged by the laser beam, can be treated with almost any type of rust protectant, because the beam intensity and the discharge frequency of the laser can be set so that the rust-protected outer surface  3  is not heated to a temperature that would harm the rust protection coating. The edge hardened by the laser beam is the most affected area.  
         [0030]     From the foregoing, persons of ordinary skill in the art will further appreciate that firearms have been disclosed with include a lock surface  5  on the front side of the ejection window  4  of the slide I wherein the lock surface  5  has an area which has been hardened by a laser based heating process.  
         [0031]     It is preferred that the slide  1  be provided with a nitrocarburized, oxidized outer surface  3 . This is particularly advantageous for standard issue models for which markings or other types of scratches should be avoided on the visible surface so that the troops using this weapon do not try and “wipe off” the marking.  
         [0032]     The hardened portion of the lock surface  5  preferably includes a wedge-shaped portion  11  of the slide material. The wedge-shaped portion  11  has the same structure as the remainder of the slide material. The wedge-shaped portion  11  may be termed a gusset.  
         [0033]     This gusset  11  has two open surfaces leading from the lower edge of the lock surface  5 . A first one of these open surfaces extends from the lower edge of the lock surface  5  upwards approximately to the upper edge of the lock surface  5 . The other one of these open surfaces extends from the lower edge of the lock surface  5  forward along the bottom  7  of the slide  1 . Both of these surfaces are connected through the material of the slide along a structure transition area  13 . Thus, a hardened area  11  is formed that is bordered on the outside by the lock surface  5  and the thickness of which increases towards the outside. Unexpectedly, this is highly advantageous.  
         [0034]     Namely, if the barrel of the weapon sinks downward when it is unlocked, then the slide  1  over the lock surface  5  supports itself on a narrowing strip of the lock button of the barrel. Thus, the surface pressure on the bottom of this lock surface can increase. But, the durability of this underside is also increased because of the thicker hardness layer  11 .  
         [0035]     In the upper part of the lock surface  5 , the structure transition area  13  tapers off between the hardened layer  11  and the non-hardened layer in the upper edge. Thus, the surface-treated outer surface  3  of the weapon remains protected from all types of changes, because the transition area  11  does not meet this outer surface  3 .  
         [0036]     It is preferred that each of the two open surfaces of the hardened material gusset  11  extend approximately 1 to 1.5 mm away from the lower edge of the lock surface  5 . Thus, the widths of these surfaces never exceed the height of the lock surface  5  and, thus, these surfaces never meet the upper, blackened outer surface  3  of the weapon. An average preferred value of the thickness of the hardness layer in the lock surface  5  is 0.5 mm in the direction of fire and 1.0 mm perpendicular to the direction of fire.  
         [0037]     The slide  1  itself mainly consists of strong high-alloy steel that, even unhardened, possesses the required tenacity. For example, 42 CrMoS 4  is particularly suitable as the material for the slide  1 . As a second treatment, the finished slide  1  is nitrocarburized and black-oxidized within the framework of a heat treatment. After this second treatment, the lock surface  5  is laser-hardened as explained above.  
         [0038]     Although certain example methods and apparatus have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.