WO2021240024A1

WO2021240024A1 - Method for manufacturing a firearm stock in a mould

Info

Publication number: WO2021240024A1
Application number: PCT/ES2020/070342
Authority: WO
Inventors: Ion RACIONERO ZABALO; Santiago Jorge NEIRA HERNANDEZ
Original assignee: Dikar, S.Coop.
Priority date: 2020-05-25
Filing date: 2020-05-25
Publication date: 2021-12-02

Abstract

Disclosed is a method for manufacturing a stock for a firearm in a mould (1), which method comprises a step of depositing a carbon fibre skin (2), in which at least one layer of resin-impregnated carbon fibre is deposited over an inner surface (4) of a cavity (5) of the mould (1) and a step of closing the mould (1). The method further comprises, subsequent to the step of closing the mould (1), at least one insertion step in which an exothermic foam material (6) is fed into the cavity (5) of the mould (1) and, subsequent to the step of inserting the exothermic foam material (6), a foaming step in which said exothermic foam material (6) forms a foam that fills the cavity (5) and remains bonded to the carbon fibre skin (2).

Description

DESCRIPTION

Manufacturing method of a stock for a firearm in a mold '

TECHNICAL SECTOR

The present invention relates to methods of manufacturing a stock for a firearm in a mold.

PRIOR STATE OF THE ART

The less a stock weighs for a firearm, the longer it can be carried or held before the shooter experiences fatigue that affects their aim. In addition, the less a stock weighs for a firearm, the less force is required for the shooter to adjust the position of the weapon, which is an important aiming factor when small adjustments to the position of the weapon are required.

In addition, the stock for a firearm must have a high rigidity so that the efforts transmitted to the stock by functional elements such as the set of mechanisms, the trigger and / or the barrel do not deform or damage the stock throughout its length. useful life. This rigidity is also essential for the weapon to be accurate.

For all these reasons, butts for a firearm are known that comprise a carbon fiber skin. Thanks to the good combination of stiffness and reduced weight of the carbon fiber skin, these stocks are an attractive replacement to traditional aluminum, wood or synthetic plastic stocks.

Despite the desirable characteristics of a stock made of carbon fiber, the high price of carbon fiber and the high cost of manufacture mean that the stock for a firearm that comprises a carbon fiber skin can often be excessively expensive. Known manufacturing methods are time consuming and specialized artisan work, or require complex industrial process equipment for the carbon fiber skin to take on the irregular and complex shape of the cylinder head.

US9926219B2 describes a method of manufacturing in a mold of a butt for a firearm comprising a skin of carbon fiber. The method comprises a step of deposition of a carbon fiber skin. Carbon fiber skin is made up of an outer wall and an inner wall. In the deposition stage, multiple sheets of carbon fibers impregnated in a resin are deposited on an interior surface of a mold cavity, the interior surface defining the external shape of one of the walls. The deposition stage is repeated for the other wall. Once the mold is closed, each wall is formed separately by compression molding, where the multiple sheets of carbon fibers impregnated in a resin are compressed against a core or a counter-mold. After forming the walls, they are flush and joined together, thus obtaining a cylinder head with a carbon fiber skin.

EXHIBITION OF THE INVENTION

The object of the invention is to provide a method of manufacturing a stock for a firearm in a mold, as defined in the claims.

The method of the invention is a method of manufacturing a stock for a firearm in a mold, the stock comprising a carbon fiber skin, and the method comprising at least one step of deposition of the carbon fiber skin and a stage of closing the mold.

In the stage of deposition of the carbon fiber skin, at least one sheet of carbon fiber impregnated in a resin is deposited on an interior surface of a mold cavity, said interior surface of the mold defining the external shape of the cylinder head.

The method of the invention further comprises an insertion stage after the mold closing stage in which an exothermic foamable material is inserted into the mold cavity, and a foaming stage after the material insertion stage. foamable exothermic material, wherein said foamable exothermic material foams. This foaming process creates a foam that fills the cavity and adheres to the carbon fiber skin.

In the methods of manufacturing a stock for a firearm of the state of the art, the manufacturing cost is high. Either it takes a lot of time and specialized craftsmanship for the carbon fiber skin to take on the irregular and complex shape of the cylinder head, or complex process equipment is often used that shortens manufacturing time, but requires high external energy sources. . For example, methods that form carbon fiber skin by compression molding require presses, and those that do so by resin transfer molding require injectors and vacuum pumps.

In the method of the invention, the foaming of the exothermic foamable material forms the carbon fiber skin, generating a pressure and a temperature that shorten the manufacturing time without requiring complex process equipment that requires high external energy sources. In this way, a cylinder head is obtained with a low manufacturing cost, while presenting the advantages associated with carbon fiber skin, that is to say, an inexpensive, light and rigid cylinder head.

On the other hand, with the foam adhered to the carbon fiber skin, a solid stock is achieved. In this way, the cylinder head obtained from the proposed method provides a general impression of quality associated with both the carbon fiber and the solid cylinder head.

These and other advantages and characteristics of the invention will become apparent in view of the figures and the detailed description of the invention.

DESCRIPTION OF THE DRAWINGS

Figure 1 schematically represents a perspective view of a mold used in a preferred embodiment of the manufacturing method according to the invention. Figure 2 schematically represents a sectional view of the mold of Figure 1 after the insert placement step.

Figure 3 schematically represents a perspective view of a detail of the mold of Figure 1 after the stage of deposition of the carbon fiber skin.

Figure 4 is a sectional view of a detail of Figure 3.

Figure 5 schematically represents a perspective view of the mold of Figure 1 after the stage of closing the mold.

Figure 6 is a sectional view of Figure 5 during the insertion stage.

Figure 7 is a sectional view of Figure 5 after the foaming step.

Figure 8 schematically represents a perspective view of the mold of Figure 1 during the demoulding stage.

Figure 9 schematically represents a perspective view of a stock for a firearm removed from the mold of Figure 1, and the stock for a firearm after coupling functional elements and accessories.

DETAILED EXHIBITION OF THE INVENTION

Figures 1 to 9 represent, by way of example and schematically, the steps of a preferred embodiment of the method of the invention.

The method of the invention is a method of manufacturing a stock 100 for a firearm in a mold 1, the stock 100 comprising a carbon fiber skin 2.

The stock for a firearm is the chassis of the firearm to which the functional elements and accessories are attached, such as, for example, the set of mechanisms, the butt plate and belt holders. Stocks that comprise a carbon fiber skin are an attractive replacement to traditional aluminum, wood or synthetic plastic stocks thanks to the good combination of stiffness and reduced weight.

The method of the invention comprises at least: a step of deposition of a carbon fiber skin 2, in which at least one carbon fiber sheet 3 impregnated in a resin is deposited on an interior surface 4 of a cavity 5 of the mold 1, said inner surface 4 of mold 1 defining the external shape of the cylinder head 100, a stage of closing the mold 1, an insertion stage after the stage of closing the mold 1 in which it is inserted into the cavity 5 of the mold 1 an exothermic foamable material 6, and a foaming stage after the insertion stage of the exothermic foamable material 6 in which said exothermic foamable material 6 foams giving rise to a foam that fills the cavity 5 and remains adhered to the skin of carbon fiber 2.

The carbon fiber skin 2 gives the stock 100 good rigidity and a good aesthetic appearance, and the foam adhered to the carbon fiber skin 2 gives the stock 100 solidity and lightness. Thus, the stock 100 obtained from the method of the invention is a light, rigid stock and provides an overall impression of quality associated with both carbon fiber and solid stock.

In the method of the invention, the foaming of the exothermic foamable material 6 forms the carbon fiber skin 2 generating a pressure and a temperature that shorten the manufacturing time without requiring complex process equipment that requires high external energy sources. In this way, the stock 100 obtained from the method of the invention is a stock with a low manufacturing cost, while presenting the advantages associated with carbon fiber skin, that is, an inexpensive, light and rigid stock. .

On the one hand, in the foaming stage, the foam that fills the cavity 5 generates a pressure to conform the carbon fiber skin 2 with the external shape of the cylinder head 100, pressing the carbon fiber skin 2 against the inner surface 4 of the mold 1. On the other hand, when the exothermic foamable material 6 foams, an exothermic reaction occurs which generates a temperature in the mold 1 during the foaming step. This heat source of the exothermic foamable material 6 reduces the viscosity of the resin allowing, together with the pressure generated by the foam, to form the carbon fiber skin 2.

Finally, towards the end of the foaming stage, the polymerization reaction of the resin that makes up the carbon fiber skin begins. 2. The polymerization or curing process is a process in which the number of cross-links of the resin increases, reducing the mobility of the molecular segments and increasing the rigidity of the material. The temperature increase is progressive as the exothermic foamable material 6 reacts and the foaming stage proceeds. Therefore, until the foaming process is mostly completed, that is, until the end of the foaming stage, the resin does not reach a sufficient temperature to start polymerizing during the foaming stage.

Once all of the foamable exothermic material 6 foam ends, the foaming step is completed. Foaming of the exothermic foamable material 6 is a relatively quick process compared to artisan manufacturing methods, thereby shortening the manufacturing time of the cylinder head 100.

In the preferred embodiment, the mold 1 shown by way of example and schematically in Figure 1 is composed of two pieces and once the mold 1 is closed, the two pieces form the cavity 5 inside, so that each piece of the mold 1 comprises a part of the inner surface 4. Preferably the inner surface 4 is an impermeable surface. In this way, the cylinder head 100 can be easily removed from the mold 1.

However, this configuration of the mold 1 is not intended to be a limitation of the present invention and in other possible embodiments the mold 1 could be composed of more pieces such as, for example, an upper, a lower and two sides, or by other possible configurations known to those skilled in the art so that the cylinder head 100 can be easily removed from the mold. In the carbon fiber skin deposition step 2 of the preferred embodiment of the method, at least one carbon fiber sheet 3 impregnated in a resin is deposited on the inner surface 4 of the mold 1.

The term resin refers to a polymeric system based on a resin to which other components can be added in the formulation base, such as, for example, additives such as catalytic and thickening agents, low-shrinkage agents, polymerization inhibitors and agents. demoulding.

The carbon fiber sheet 3 provides rigidity, resistance to bending, traction and compression to the carbon fiber skin 2, while the resin that impregnates the carbon fiber sheet 3 gives plasticity to the carbon fiber skin 2 during the foaming step so that the carbon fiber skin 2 takes the shape of the inner surface 4 of the mold 1 without breaking the carbon fibers.

In the preferred embodiment, the carbon fiber sheet 3 is pre-impregnated with resin. In this way, the stage of deposition of the carbon fiber skin 2 is simplified, because when the carbon fiber sheet 3 is deposited, it is already impregnated and does not require impregnation after its deposition.

The carbon fiber sheet 3 of the preferred embodiment is a non-woven carbon fiber sheet. The non-woven carbon fiber sheet is more malleable than the woven carbon fiber sheet, so that it allows the carbon fiber skin 2 to be formed with less energy while reducing the manufacturing cost.

In the preferred embodiment, the carbon fiber sheet 3 is a polymeric molding composite supplied in a ready-to-mold short carbon fiber reinforced sheet format, mainly used in compression molding. Hereinafter, the polymeric molding composite supplied in sheet format reinforced with short carbon fibers is referred to as a CF-SMC ("Carbon Fiber Sheet Molding Compound").

CF-SMC is manufactured from chopped carbon fibers dispersed in a matrix of resin in a "B" state of maturation, a state that favors the handling and conservation / transport of the material. In this "B" state, its polymerization has not started, for this the external contribution of a heat source is required. The CF-SMC is covered on both sides with a plastic polyethylene or nylon film to prevent self-adhesion during storage / transport. A resin paste is spread on the bottom film, and pieces of carbon fiber are randomly deposited on the paste up to the desired percentage of reinforcement. The resin paste may comprise other components such as, for example, additives such as catalysts and thickeners, low shrinkage agents, polymerization inhibitors and mold release agents. The top film is placed and the assembly is continuously laminated to the desired grammage. The resulting composite is a pre-impregnated, non-woven carbon fiber sheet with good malleability ready to mold into the desired final shape. Before the carbon fiber skin deposition stage 2, the plastic films covering both sides of the CF-SMC are removed.

The main advantage of CF-SMC is its excellent plasticity compared to woven carbon fiber sheet, where staple carbon fibers further reduce manufacturing cost. Furthermore, it has an excellent compromise between high plasticity, low cost of raw material and sufficient rigidity for the application of a stock of a firearm.

Another advantage of CF-SMC is that, as the resin is in a maturing “B” state, the resin loses its stickiness and cannot spill thanks to its viscous texture in the carbon fiber skin deposition stage 2 , while the resin confers sufficient plasticity to the carbon fiber skin 2 during the foaming stage.

In the preferred embodiment of the invention, the CF-SMC comprises carbon fibers from recycling processes. This makes the cylinder head 100 more sustainable and even more economical, as it gives carbon fiber a second life.

The CF-SMC of the preferred embodiment comprises a percentage by weight of carbon fiber between 40% and 60% with respect to the percentage by total weight, and a length of carbon fibers between 25 and 75 mm, thus obtaining a compromise optimum between the stiffness of the carbon fiber and the plasticity of the resin. More specifically, the weight percentage of fiber of carbon is 45% and the length of carbon fibers is 50mm. In addition, the 50mm length is a standard length on commercial CF-SMCs, making it easy to find supplies for this material.

In the method of the invention the resin is preferably a vinyl ester resin or an epoxy resin. Said resins have a low viscosity and high flowability even at room temperature, thus favoring the impregnation of the carbon fibers and the correct matrix / reinforcement interaction for a correct transmission of stresses to external loads during the foaming stage. In addition, these resins have relatively short polymerization cycles, taking into account the type of catalytic agent used in the base of the resin formulation and the temperature of the external heat source. In the preferred embodiment of the method of the invention the resin is a vinyl ester resin.

In the preferred embodiment of the method, prior to the deposition of-at least one carbon fiber sheet 3, an aesthetic sheet 7 is deposited in the stage of deposition of the carbon fiber skin 2, the aesthetic sheet 7 being the one that provides the final aesthetics to the cylinder head100. The aesthetic sheet 7 is preferably a woven carbon fiber sheet. The woven carbon fiber sheet adds rigidity to the structure, but is also very expensive. In this way, the aesthetic sheet 7 gives the cylinder head 100 a more rigid butt look without raising the cost of raw material of the entire carbon fiber skin 2. To guarantee the interaction between the different layers, the aesthetic sheet 7 is impregnated with the same resin as the carbon fiber sheet 3.

In other embodiments, the aesthetic sheet 7 deposited can be a sheet with a stamping or with a personalized design for each user to achieve a specific aesthetic appearance, or the aesthetic sheet 7 can be deposited on only some specific area of the interior surface 4 to give it that aesthetic appearance only in that specific area. However, in other embodiments in which it is desired to obtain the finish provided by the carbon sheet 3, it is feasible not to use said aesthetic sheet 7.

In the preferred embodiment of the method of the invention, in the carbon fiber skin deposition step 2, more than one carbon fiber sheet 3 is deposited in at least one cylinder head area 100 giving rise to a reinforcement area 8. Thus, increasing the thickness of the carbon fiber skin 2 in the reinforcement area 8 increases the stiffness in that reinforcement area 8. Therefore, the reinforcement zone 8 supports greater forces than the rest of the cylinder head 100.

In the preferred embodiment shown in Figures 3 and 4, a single reinforcement zone 8 corresponding to the housing for a retraction tongue is represented by way of non-limiting example. The recoil tab of the set of mechanisms 15 rests on this housing of the stock 100 when the firearm is fired, transmitting the recoil forces of the set of mechanisms 15 to the stock. Generally, this reinforcement zone 8 is the one that supports the greatest efforts in the cylinder head 100. As shown in detail in Figure 4, in the reinforcement zone 8 the carbon fiber skin 2 comprises an aesthetic sheet 7 and two Carbon fiber sheets 3, while in the rest of the cylinder head 100 the carbon fiber skin 2 comprises an aesthetic sheet 7 and only one carbon fiber sheet 3.

In other embodiments, the stock 100 can comprise several reinforcement areas 8. The reinforcement area 8 can be any area of the stock 100 that must withstand greater stresses than the rest of the stock 100, such as, for example, the grip and / or the mooring area of the set of mechanisms 15.

In the preferred embodiment of the method, the cavity 5 of the mold 1 is communicated with the exterior by means of an insertion conduit 9 and at least one outlet conduit 10 configured to communicate the cavity 5 of the mold 1 with the exterior once the skin of the carbon fiber 2 and closed the mold 1, as shown in Figures 3 and 4.

The insertion conduit 9 is configured so that the exothermic foamable material 6 is inserted into the cavity 5 from the outside through said insertion conduit 9. In this way, the stage of closing the mold 1 can be advanced to the stage of insertion, without jeopardizing the foaming stage with the delay of an intermediate stage of closing of the mold 1 between the insertion stage and the foaming stage.

In the preferred embodiment of the method, the stage of closing the mold 1 is subsequent to the stage deposition of the carbon fiber skin 2. Figure 5 shows the mold 1 of the preferred embodiment of the method after the stage of closing the mold 1, in which the two pieces of the mold 1 are arranged with the parts of the inner surface 4 on which the carbon fiber skin 2 has been previously deposited facing each other, leaving the cavity 4 inside. As the parts of the inner surface 4 face each other, the carbon fiber skin 2 is joined at the intersection of the parts, the carbon fiber skin 2 being a substantially closed skin after the mold closure step 1. Thus, in the foaming stage the foam does not rise to the outer surface of the cylinder head 100.

The outlet conduit 10 is configured to extract to the outside gases produced during the foaming stage. In this way, the existence of air bubbles trapped in the carbon fiber skin 2 that weaken or worsen the appearance of the carbon fiber skin 2 is minimized.

In the preferred embodiment of the method, as shown in Figure 3, the insertion conduit 9 and the outlet conduits 10 are tubular elements that are arranged substantially orthogonal to the inner surface 4 at the intersection of the parts that make up the mold 1 after depositing the carbon fiber skin 2 on the inner surface 4. Thus, when the mold 1 is closed, the carbon fiber skin 2 remains closed except for the insertion conduit 9 and the outlet 10 going through the carbon fiber skin 2.

The insertion conduit 9 preferably has a minimum diameter configured to be able to quickly carry out the insertion stage before the foaming stage begins and the outlet conduit 9 preferably has a maximum diameter configured so that the gases escape without there being losses of significant pressure in cavity 5 of mold 1 closed.

However, in other embodiments of the method the insertion conduit 9 and the outlet conduit 10 can be integral parts to the mold 1 or separate pieces that are arranged before depositing the carbon fiber skin 2. In these cases, to facilitate the carbon fiber skin deposition 2 without covering the insertion duct 9 and the outlet ducts 10, cuts can be made in the carbon fiber sheet 3 before depositing it, said cuts coinciding with the insertion conduit 9 and the outlet conduits 10 in the deposition stage.

In another embodiment of the method the outlet conduit 10 may be arranged in an existing hole. An existing hole may be, for example, a side-to-side through hole in the stock 100 (not shown in the Figures) configured to receive a set screw for the mechanism assembly 15 of the firearm. In this way, the outlet conduit 10 does not leave new holes in the carbon fiber skin 2.

Like the inner surface 4, the insertion conduit 9 and the outlet conduit 10 are preferably waterproof so that they can be easily removed from the mold.

In the preferred embodiment, the method further comprises a stage of inserting the inserts, prior to the stage of deposition of the carbon fiber skin 2, where at least one insert 11 is placed on the inner surface 4 of the mold 1 abutting with at least one stopper element 12 of the mold 1 configured to position the insert 11, leaving the carbon fiber skin 2 deposited on the insert 11 in the deposition stage, so that the insert 11 remains attached to the fiber fiber skin Carbon 2 in a specific position on the cylinder head 100.

As shown in Figure 6, in the carbon fiber skin 2 deposition stage, the resin impregnated carbon fiber sheet 3 is deposited on the inner surface 4 of the cavity 5 of the mold 1, and also on the inserts 11. In this way, in the foaming stage the foam presses the carbon fiber skin 2 against the inserts 11 until they abut the stop element 12. At the same time as the carbon fiber skin 2 presses the insert 11, the resin of the carbon fiber skin 2 flows, and towards the end of the foaming stage the resin polymerizes around the inserts 11, leaving the inserts 11 attached to the carbon fiber skin 2 in a specific position of the cylinder head 100. Therefore, integral inserts are obtained with the carbon fiber skin, as opposed to inserts simply inserted into the carbon fiber skin.

The inserts 11 preferably comprise a ridged, grooved or grooved outer surface. a high roughness configured to improve the adhesion of the insert 11 to the carbon fiber skin 2.

By way of non-limiting example, Figure 2 represents the insert placement stage in which two inserts 11 are placed abutting two stop elements 12, although more than two inserts 11 and two stop elements could be placed. stop 12.

The inserts 11 allow functional elements or accessories to be attached to the stock 100 once the stock 100 has been removed from the mold. For example, the inserts 11 shown in Figure 2 comprise an internal thread configured to receive and fix threaded ends of a strap of a firearm once the stock 100 has been demolished. Other inserts 11 not shown in the figures may be inserts with internal thread intended to receive fixing screws of a butt plate 14 or of a set of mechanisms 15 of a firearm.

Figures 1 and 2 show the abutment elements 12 of the preferred embodiment configured to position the insert 11. The abutment element 12 is a stem attached to the mold 1 and comprises a projection 121 that projects from the inner surface 4 of the mold 1 into cavity 5. In the insert placement stage the internal thread of insert 11 is inserted into projection 121 of stopper element 12 until it abuts against projection 121, thereby positioning insert 11.

The projection 121 preferably comprises an external thread which in the insert placement stage is screwed into the internal thread of the insert 11. This ensures that the insert 11 cannot accidentally come out of the projection 121 during the subsequent steps of the method.

Furthermore, with the external thread of the projection 121, the insertion depth of the insert 11 in the stop element 12 can be adjusted to leave a small gap between the stop element 12 and the insert 11, said gap being filled with the fiber skin of carbon 2 in the foaming stage. In this way, a more continuous appearance of the carbon fiber skin 2 is achieved and the adhesion of the insert 11 to the carbon fiber skin 2 is improved. However, in other possible embodiments, the stop element 12 can be an integral part of the mold 1 or it can be made in any other way known to those skilled in the art.

In a preferred embodiment of the method of the invention the insert 11 is a metallic insert.

In a preferred embodiment of the method, the outlet conduit 10 is arranged in one of the inserts 11. In this way, the arrangement of the outlet conduit 10 is facilitated.

Figure 6 represents an example of a sectional view of the mold 1 during the insertion stage of the preferred embodiment of the method, after the stage of deposition of the carbon fiber skin 2 shown in Figure 3 and at the step of closing the mold 1 shown in Figure 5, in which an exothermic foamable material 6 is inserted into the cavity 5 of the mold 1 through the insertion conduit 9.

In the preferred embodiment of the method, the exothermic foamable material 6 is a polyurethane system. The polyurethane system comprises two liquid components, polyol and isocyanate. As the exothermic foamable material 6 is in a liquid state, its insertion is facilitated. Furthermore, the reactivity of the mixture can be controlled so that the insertion stage can be completed before the foaming stage begins. For example, so that the foaming reaction begins about 15-30 seconds after mixing the components of the exothermic foamable material 6, so as to allow time to insert it into the cavity 5 of the mold 1. In the foaming stage of the embodiment preferably, the exothermic foamable material 6 gives rise to a polyurethane foam that fills the cavity 5 and adheres to the carbon fiber skin 2. The polyurethane foam takes place through an exothermic foaming chemical reaction by mixing polyol and isocyanate, and it forms the carbon fiber skin 2 generating a pressure and a temperature that shorten the manufacturing time.

However, in other embodiments another foamable exothermic material 6 could be employed which involves the use of foaming agents integrated into thermoset polymeric systems, eg, phenolic, polyester or epoxy.

As mentioned, in the preferred embodiment, the carbon fiber skin 2 is a substantially closed skin after the mold closure step 1, so that in the foaming step the foam does not rise to the outer surface of the cylinder head 100, and therefore the cylinder head 100 obtained according to the method of the invention is a solid cylinder head with a carbon fiber skin 2 and a foam core.

The carbon fiber skin 2 gives the stock 100 good rigidity and a good aesthetic appearance, and the foam core adhered to the carbon fiber skin 2 gives the stock 100 solidity and lightness. Thus, the stock 100 obtained from the method of the invention is a light, rigid stock and provides an overall impression of quality associated with both carbon fiber and solid stock.

As previously mentioned and shown in Figure 7, in the foaming stage the foam that fills the cavity 5 generates a pressure to conform the carbon fiber skin 2 with the external shape of the cylinder head 100, pressing the carbon fiber skin 2 against inner surface 4 of mold 1.

In order for the pressure generated by the foam in the foaming stage to be adequate so that it forms the carbon fiber skin 2 without entailing a risk of opening the mold 1, in the insertion stage the amount of foamable exothermic material is controlled 6 to be inserted.

The appropriate pressure depends in turn on the thickness of the carbon fiber skin 2. The thicker the greater the stiffness, but also requires greater pressure to form the carbon fiber skin 2 and a higher cost of raw material. For this reason, it is convenient to limit the maximum thickness of the carbon fiber skin 2. In a preferred embodiment, the carbon fiber skin has a maximum thickness of 2 mm. More specifically, in order to find a compromise between a sufficient stiffness and a necessary energy to form the carbon fiber skin 2, in a preferred embodiment the carbon fiber skin has a thickness between 1 and 2 mm.

In a preferred embodiment, the foam generates a pressure on the carbon fiber skin 2 of between 1 and 3 bars in the foaming stage, preferably a pressure of 2 bars. Thus, the carbon fiber skin 2 having a maximum thickness of 2 mm is suitably shaped. As previously mentioned, the exothermic reaction of the exothermic foamable material 6 generates a temperature in the mold 1 that increases the fluidity of the resin, allowing the carbon fiber skin 2 to be formed together with the pressure generated by the foam and towards the At the end of the foaming stage, the polymerization reaction of the carbon fiber skin resin 2 begins, increasing the rigidity of the material. When the exothermic foamable material 6 is a polyurethane system this temperature is about 60-90 ° C.

However, taking into account the catalytic system used in the base of the resin formulation that integrates the carbon fiber skin 2, the temperature generated in the foaming stage may not complete the polymerization cycle of the resin. producing an insufficient degree of conversion in the polymerization reaction to proceed with the demoulding of the part just after the foaming stage, since the carbon fiber skin 2 does not reach sufficient rigidity to guarantee the integrity of the cylinder head after its demoulding .

A preferred embodiment of the method of the invention comprises a curing stage subsequent to the foaming stage, in which for a predetermined period of time there is an external input of temperature above a threshold temperature in the mold 1. In this way, in the predetermined time, the carbon fiber skin 2 reaches sufficient rigidity to guarantee the integrity of the cylinder head after the curing stage, shortening the polymerization time of the resin with which the cylinder head can be demoulded and, consequently, the time total manufacturing.

The preferred embodiment of the method shown in the Figures comprises the curing step. Vinyl ester resin itself has a high polymerization rate and high productivity. Increasing the temperature of the curing stage further shortens the polymerization time of this resin.

Preferably the threshold temperature and the predetermined time of the curing step are between 120 and 135 ° C, and 10 minutes respectively. By subjecting the vinyl ester or epoxy resin to a temperature of between 120 and 135 ° C for 10 minutes, the carbon fiber skin 2 is polymerized with sufficient rigidity to guarantee the integrity of the cylinder head after demoulding. A preferred embodiment of the method of the invention comprises a cooling stage after the curing stage in which the mold 1 is cooled below a temperature, preferably below 40 ° C, and a demoulding stage after the stage in which the mold 1 is opened to extract the cylinder head 100. The cooling step facilitates the demoulding of the cylinder head 100 and allows the mold 1 to be reused in the method of the invention to manufacture another cylinder head without the risk of premature polymerization of the resin in the other cylinder head.

The preferred embodiment of the method comprises the cooling and demoulding stages. In Figure 8 the mold 1 is schematically represented during the demoulding stage of the preferred embodiment of the method. During the demoulding stage of the preferred embodiment, the mold 1 is opened, leaving the cylinder head 100 obtained with the method of the invention on one of the parts that make up the mold 1. Before removing the cylinder head 100, the stops 12 are removed, the insertion conduit 9 and outlet conduits 10.

The cylinder head 100 may comprise at least one area 13 configured to be covered with another part after the demoulding stage, the insertion conduit 9 or the outlet conduit 10 being arranged in said area 13. The area 13 may correspond to an area of the cylinder head. 100 which is covered by an accessory or a functional element after demoulding the cylinder head 100. In this way the hole left in the carbon fiber skin 2 by the insertion duct 9 or the outlet duct 10 is covered.

As shown in Figure 9, in the preferred embodiment the cylinder head 100 comprises two zones 13 configured to be covered with the butt plate 14 and the set of mechanisms 15 after the demoulding stage, in a zone 13 the duct is arranged 9 and in the other area 13 the outlet ducts 10 are arranged after depositing the carbon fiber skin 2. In this way, the hole left by the insertion duct 9 is covered by the butt plate 14 and the holes left They are covered by the outlet conduits 10 by the set of mechanisms 15. Likewise, after removing the stock 100, the ends of the strap of the firearm are screwed into the inserts 11 integral to the stock 100.

Claims

1. Method of manufacturing a stock for a firearm in a mold (1), the stock (100) comprising a carbon fiber skin (2), and the method comprising at least the steps of: deposition of the skin carbon fiber (2) in which at least one carbon fiber sheet (3) impregnated in a resin is deposited on an interior surface (4) of a cavity (5) of the mold (1), defining said interior surface (4) of the mold (1) the external shape of the cylinder head (100), and closure of the mold (1), characterized in that it comprises an insertion stage after the stage of closing the mold (1) in which it is inserted into the cavity (5) of the mold (1) an exothermic foamable material (6), and a foaming stage after the insertion stage of the exothermic foamable material (6) in which said exothermic foamable material (6) foams giving rise to a foam that fills the cavity (5) and adheres to the carbon fiber skin (2).

Manufacturing method according to claim 1, wherein the carbon fiber sheet (3) is a carbon fiber sheet pre-impregnated with resin.

Manufacturing method according to claim 1 or 2, wherein the carbon fiber sheet (3) is a non-woven carbon fiber sheet.

Manufacturing method according to claim 3, wherein the carbon fiber sheet (3) is a polymeric molding compound supplied in a sheet format reinforced with short carbon fibers.

Manufacturing method according to claim 4, wherein the carbon fiber sheet (3) comprises carbon fibers from recycling processes.

6. Manufacturing method according to claim 4 or 5, wherein the carbon fiber sheet (3) comprises a percentage by weight of carbon fiber between 40% and 60% with respect to the percentage by total weight, and a length of carbon fibers between 25 and 95 mm, preferably a percentage by weight of carbon fiber of 45% and a length of carbon fibers of 50 mm.

Manufacturing method according to any one of the preceding claims, wherein the resin is a vinyl ester or epoxy resin.

Manufacturing method according to any of the preceding claims, wherein in the deposition stage an aesthetic sheet (7) is deposited prior to the deposition of the at least one carbon fiber sheet (3), said aesthetic sheet ( 7) preferably a woven carbon fiber sheet.

9. Manufacturing method according to any of the preceding claims, wherein in the deposition step more than one carbon fiber sheet (3) is deposited in at least one area of the cylinder head (100), giving rise to an area of reinforcement (8).

Manufacturing method according to any of the preceding claims, wherein the cavity (5) of the mold (1) is communicated with the outside through at least one insertion conduit (9) and at least one outlet conduit (10) configured to communicate the cavity (5) of the mold (1) with the exterior after the stage of deposition of the carbon fiber skin (2) and the stage of closing the mold (1).

Manufacturing method according to claim 10, wherein the insertion conduit (9) is configured so that the exothermic foamable material (6) is inserted into the cavity (5) from the outside through said insertion conduit ( 9).

Manufacturing method according to claim 10 or 11, wherein the outlet conduit (10) is configured to extract to the outside gases produced during the foaming stage.

Manufacturing method according to any of the preceding claims, comprising a step of placing the inserts before the deposition step, wherein at least one insert (11) is placed on the inner surface (4) of the mold (1) making butt with at least one stop element (12) of the mold (1) configured to position the insert (11), leaving the carbon fiber skin (2) deposited on the insert (11) in the deposition stage, so that the insert (11) remains attached to the carbon fiber skin (2) in a specific position of the cylinder head (100).

Manufacturing method according to claim 13, wherein the insert (11) is a metal insert.

Manufacturing method according to claim 13 or 14, wherein the outlet conduit (10) is arranged in one of the inserts (11).

Manufacturing method according to any of the preceding claims, wherein the exothermic foamable material (6) is a polyurethane system.

17. Manufacturing method according to any of the preceding claims, wherein the carbon fiber skin (2) has a maximum thickness of 2 mm.

Manufacturing method according to claim 17, wherein in the foaming stage the foam generates a pressure on the carbon fiber skin (2) of between 1 and 3 bars, preferably a pressure of 2 bars.

Manufacturing method according to any of the preceding claims, comprising a curing stage subsequent to the foaming stage in which for a predetermined period of time there is an external temperature input above a threshold temperature in the mold (1 ).

20. Manufacturing method according to claim 19, wherein the threshold temperature and the predetermined time of the curing step are between 120 and 135 ° C and 10 minutes respectively.

Manufacturing method according to claim 19 or 20, comprising a cooling stage subsequent to the curing stage in which the mold (1) is cooled below a temperature, preferably below 40 ° C and a stage post demoulding to the cooling stage, where the mold (1) is opened to extract the cylinder head (100).

Manufacturing method according to claim 21, wherein the cylinder head (100) comprises at least one area (13) configured to be covered with another part after the demoulding step, the insertion conduit (13) being arranged in said area (13). 9) or the outlet duct (10).