WO2000008408A1

WO2000008408A1 - Underwater spear-gun with free piston in the spear

Info

Publication number: WO2000008408A1
Application number: PCT/HR1999/000017
Authority: WO
Inventors: Neven Ninic
Original assignee: Neven Ninic
Priority date: 1998-08-01
Filing date: 1999-07-27
Publication date: 2000-02-17
Also published as: HRP980422A2; AU4923699A

Abstract

An underwater spear equipped with a cylindrical cavity (7) and a free piston (44) which, at the moment of launching the spear, divides the cavity to a smaller front part where the piston hermetically closes a certain volume of compressed air through a nozzle (42) in the rear end (41) of the spear, producing thereby a reactive force during and in the direction of the spear movement. The speargun has a mechanism for charging the spear with water through the nozzle while the spear is fixed in the gun consists of manual piston pump (9), pressure cylinder (1), hollow pressure piston (2) and hollow spear pusher (6) with non-return valve. In a second embodiment there is no spear pusher. The non-return valve is located at the pressure-cylinder water intake (27) and the pressure piston is replaced by the very rear end of the spear.

Description

UNDERWATER SPEAR-GUN WITH FREE PISTON IN THE SPEAR

INVENTION DESCRIPTION

1. FIELD OF APPLICATION

The invention relates to underwater guns for sport underwater fishing, launching spear by force of air compressed in the hollow body of the gun or of stretched elastic bands (IPC field A 01 K).

2. TECHNICAL PROBLEM

The problem is to increase the spear range, or to increase the spear energy at larger distances within the visibility limits. The problem can be solved by increasing the initial kinetic energy of the spear. However, such a solution results in uneconomicly high initial speed, resulting in fast loss of kinetic energy, destruction of target at lesser distances and damaging of the spear when it hits a close rock. The ideal solution would be such that would increase the range at a more or less constant speed - the minimum speed required to reach the target.

3. BACKGROUND ART

To the best of my knowledge, presently, larger spear ranges are being obtained by larger initial spear speed only. This is obtained by using guns with larger quantity of compressed air or by fitting several elastic bands stretched parallelly. However, in all such cases, besides the gun becoming larger and more difficult for charging - the spear larger initial speed also results in the above mentioned disadvantages. Therefore, the technical problem remains unsolved but only lessened or avoided by assessing at what distance the target is expected to be, in order to determine the spear initial speed in advance.

4. DISCLOSURE OF THE INVENTION

The primary goal of the invention is to increase the underwater gun efficiency without increasing the spear initial kinetic energy, this being possible only if the spear, following its launching at a moderate initial speed - required and sufficient for producing the required effect at the target, has its own propelling power. This requires the spear to have an adequate energy source, charged before launching - while it is still fixed in the gun.

The underwater spear-gun constructed according to this invention consists, like classical underwater spear-guns, of the spear and the very gun. The spear according to this invention has a longitudinal cavity and a free, sealing piston in it. Prior to launching the spear - which can be by means of elastic bands - the spear cavity is divided by the piston into two parts: the front, lesser one, containing compressed air and sealed by the free piston, and the rear, larger one, containing water compressed by the above mentioned compressed air, by means of the freely moving piston that separates them. The rear end of the spear is equipped with a nozzle, sealed till the moment of launching of the spear, and open after that. The water jet, running through the nozzle and driven by the compressed air and the free piston, creates reactive propelling force on the spear. This lasts as long as until the free piston, while pushing water out, reaches its rear end position, that is, until the air compressed in the front part of the spear reaches its maximum volume and minimum pressure. In the following several minutes, the air pressure will rise due to its temperature equalling with the environment; this pressure we shall refer to as "the initial pressure", because that will be the compression from which compressing will start at preparing the spear for the next launch. The underwater spear-gun according to this invention is equipped with a device that prepares the spear for launching. It consists of a pump that takes the surrounding water in and compresses it through the nozzle into the rear part of the spear, fixed in the gun during this operation. Pumping of water and moving of the free piston compresses the air closed in the spear, to the wanted high pressure, preparing it for the above described propelling action at the moment of launching of the spear.

5. BRIEF DESCRIPTION OF ILLUSTRATIONS

The accompanying illustrations, presented in Figures 1 to 9 make part of the Description of the Invention and illustrate the above discussed best invention embodiment and its two additional variants, helping in explaining the basic principles of the invention.

Figure 1 shows the entire underwater spear-gun according to this invention, with the spear in its position prior to launching.

Figure 2 shows a cross-section of the spear, with the free piston positioned in the rear end of the spear.

Figure 3 shows a cross-section of the gun grip.

Figure 4 shows a right-side view of the gun grip.

Figure 5 shows a top-side view of the gun grip.

Figure 6 shows the cross-section D-D of the gun grip as shown in Figure 3.

Figure 7 shows a cross-section of the gun body with fitted elements.

Figure 8 shows a cross-section of the spear extension.

Figure 9 shows a top-side view of the spear extension.

6. DETAILED DESCRIPTION OF AT LEAST ONE INVENTION EMBODIMENT

Details of the given invention embodiment are illustrated by the attached drawings 1 to 7. As shown in Fig. 1 the underwater spear-gun consists of the following sections: spear A, grip B, and gun body with fitted elements C. As shown in Fig. 2, the spear consists of the polished cavity 7 through which glides free piston 44, rear part 41 with nozzle 42, and plug with valve for charging with air 48 and cap - point 50 at the front end. At its outer side, the spear has a cavity 43 for the release-stopper prominence 14, Fig. 3, and element with backward open grove 55 for transverse fixing of the spear in the gun. When the spear is inserted in the gun, the corresponding fixing element, located on the gun grip (Fig. 3, element 3), enters the grove. The rear part of the spear with nozzle 42 is screwed into the pipe 7, same as the plug 48 and cap 50 with seal 51 at the front end.

Charging the spear with air is done out of water.and could be once a season, through the element 48 through the extension 49, with the cap 50 taken off. During charging, the free piston is in its end rear position next to the nozzle, and is charged with air to the pressure called the initial pressure which could be about 30 bars. After compressing air by pumping water through the nozzle, while the spear is fixed in the gun, and after its cooling to the environment temperature, the air pressure in the spear can be about 100 bars.

The free piston 44 consists, in this embodiment, of the piston body and two double-sealing L-seals and an O-ring between them, and of an elastic plate - hit absorber at the rear part of the piston. In the air part of the spear cavity, there is some oil that decreases the piston friction and improves sealing. The distribution of masses of the spear locates the centre of gravity closer to the front end, which improves the motion stability, especially during the propelling force action.

As shown in Figures 3, 4 and 5, according to the invention, the spear is fixed in the gun by being inserted, with the piston in the rear end position, through opening 31 of the front carrier 33, Fig. 7, and is locked with the spear element 55, Fig. 2, to the grip element 12, Fig. 3. This way, the spear is properly placed in the gun and fixed transversally; in the invention embodiment shown in the Fig. 3, the spear is fixed longitudinally by rotating the spear release-stopper 15 by button 13 so that the stopper protrusion 14 enters the corresponding spear recess and, at the same time, the release spring 17 pushes the release 16 in the position as shown in Fig. 3. In order to prevent loosing it, the spear can be tied with a rope to the gun grip or body.

By stretching elastic bands 26, Fig. 5, fixed to the front part of the gun to the element 32, Fig. 7, the spear pusher 6, Fig. 3 or 5 - connected with the free end of the bands 26, Fig. 5 - is placed to the rear end of the spear, in position shown in Fig. 3 and 5. This firstly requires, by using the pusher, moving the extension 5 of the compression piston 2, Fig. 3 and 5, to the left. It returns to the position shown in Fig. 3 forced by the pressure piston spring 3. The piston 2, Fig. 3, with double-sealing L-seal and O-ring has diameter much larger than the opening of the valve in the spear pusher 6 and the spear nozzle, so that simultaneously with rising of water pressure in the pressure cylinder 1 , while water is pumped, the pressure piston 2 also produces significant axial force against the spear pusher 6, required for side sealing at the valve and nozzle openings. To easy this sealing, ring-shaped seals made of hard rubber or Teflon can be fitted on right ends of the pressure piston extension 5 and the seal pusher 6, Fig. 3.

The very grip is a combination of the above mentioned parts - pressure cylinder, spear release-stopper and gun grip 11 , connected in this embodiment with a U-shaped sheet metal 21 , welded to the pressure cylinder and with a U-shaped sheet metal 22, fixed with bolts 20 and welded to the gun grip 1 (Fig. 3 and 4).

After inserting and fixing the spear, and positioning the spear pusher onto the rear end of the spear, the rear part of the spear is filled with water. Water is pumped by moving the long piston 18, Fig. 3, with the grip 34, Fig. 7. With every move to the right in Fig. 3 and 7, pressure of water in canal 9 falls, as well as in all connected cavities (pressure tube 8, pressure cylinder 1... ) At point 19, Fig. 3, of the cavity, in the left side of the gun as embodied here, there is fit the intake valve 27, Fig. 6, with intake sieve 28. This enables filling of the piston pump 9 cylinder with the surrounding water. The cylinder space is sealed on piston 18 with seal 35, Fig. 7; the entire pump is fit into the tube 25, Fig. 7, which makes the gun body and has a longitudinal grove 56 that enables longitudinal movements of the pump grip 34 connected to the piston 18. Both the tubular part of the gun 25 and the hand pump cylinder 10 are fixed to the gun grip over the block 24. In order to enable such connections, the rear part of the block 24 is flat and connected with bolts to the U-element of the grip 22. The front part of the block is cylindrical and connected to the pump cylinder concentric tubes 18 and the gun body 25 by means of threads or hard weld.

When the piston moves in the opposite direction, the intake valve closes, the liquid pressure in the entire mentioned cavity rises, and the spear pusher valve 6 opens. Further movement of the pump piston pumps liquid from the cylinder 10, Fig. 3, through the spear nozzle into its cavity. Repeated pumping fills the spear with water, the free piston moves forward, and air in the spear is compressed to the required pressure, which can be measured with manometer 29, Fig. 6. This way, the gun is made ready for launching the spear by pushing the trigger, and the very spear is charged with propelling energy.

The following variant of the same invention is somewhat simpler than the one described above by not having the spear pusher with valve, which closes the nozzle until the pusher is disconnected from the spear, i.e. until the spear is under the force that accelerates it at the moment of launching. If this force is produced, for example, by stretched elastic bands, then, with guns of this embodiment, as with classical underwater guns, stretched bands are fastened to the incision in the side of the spear, and there is no spear pusher of the first embodiment. The nozzle end of the spear, in position when being filled with water, is designed so that it can be inserted into the pressure cylinder 1 , Fig. 3, instead of the pressure piston 2, and sealing between the pressure cylinder and the inserted cylindrical end of the spear can be obtained with two rubber O-rings inserted in adequate canals in the cylinder side. Non-return valve, required at pumping liquid into the spear and located in the spear pusher in the first variant, now can be located at the water intake opening of the pressure cylinder, fit along the pressure tube connection to the pressure cylinder 4, Fig. 3.

Besides the advantage of being simpler, this invention embodiment also has the disadvantage of somewhat early nozzle release: as soon as the spear leaves the pressure cylinder and while it is still being accelerated by elastic bands.

The third invention embodiment is somewhat more complex than the first one, differing from the first one by the spear rear end having an extension utilising the well-known hydrodynamic effect of ejector, decreasing resistance to the spear movement. In this embodiment, the spear does not end with a bottom with nozzle, but has a cylindrical extension shown in the longitudinal cross-section in Fig. 8 and the top-view in Fig. 9. In Fig. 8, element 36 is cavity with nozzle in the rear part of the spear, and 37 is the cylindrical - ejector extension with the entry part "a", where the pressure during outflow is somewhat lower than in the surrounding water, with part "b" where the flow from the nozzle mixes with water coming from the environment, and with the diffuser part "c" at whose exit the pressure is as in the surrounding water. Element 38 are wings that connect the rear end of the spear with the ejector extension, enabling entering of surrounding water into the zone "a" from sides. The wings entering edges 39 are therefore rounded, and exiting edges 40 sharpened in order to decrease resistance to side intake of the fluid.

Decrease of resistance to the spear movement is achieved with this extension, by utilising the lowered pressure, created in the zone "a" by the nozzle jet, for suction of a part of the thick marginal layer, formed in the rear cylindrical part of the spear during motion. This decreases the zone of separation of the flow and the big eddy behind the spear and, therefore, increases pressure on the very spear rear surface and decreases the total resistance to its motion.

The above described cylindrical extension at the spear rear end requires some minor modification of the spear pusher, which is now to be made with longer extension 5 of the pressure piston 2, Fig. 3, adapted to the length of the space a-b-c in Fig. 8, so that its end could press the nozzle while the spear is fixed in the gun.

7. APPLICATION OF THE INVENTION

As described above, the invention is an underwater fishing device utilising manually produced power in a more efficient way than the present underwater spear-guns: power losses are lesser, range is greater - to the visibility limits, effect at the target is greater, damage at hitting a rock is lesser. When the spear trajectory does not need to be extended, it is enough not to charge the spear with energy and the invention functions as a classical underwater gun of moderate spear initial speed. Dosing the length of the trajectory is simple, too - by dosing the quantity of water pumped into the spear.

Improvement of underwater breathing devices may result in underwater fishing becoming the sport of the future in lesser or larger sea areas, and in sport underwater spear-guns of enhanced range, made in accordance with this invention, becoming an inevitable part of the equipment.

Numerous modification possibilities at the underwater spear-guns with free piston made in accordance with this invention, without leaving the scope and nature of the invention, will be obvious to experts.

Claims

PATENT CLAIMS

1. Underwater gun launching spear by means of compressed air or stretched elastic bands, wherein in the hollow cylindrical part of the spear there is mounted a freely moving sealing piston which divides the cavity in a launched spear to the front part, hermetically closed by piston, containing compressed air, and the rear part filled with water, where, at the very end of the spear, there is a nozzle, resulting in, after launching of the spear, in water being pushed through the nozzle backward, driven by the compressed air and movement of the free piston, creating thereby a reactive force against the spear in the direction of the movement.

2. Underwater spear-gun of Claim 1 , equipped with a mechanism for fixing the spear in the gun and for fastening the launching elastic bands, wherein at the outer rear part of the spear there is an element with a longitudinal and backward open grove which, when the spear is longitudinally inserted into the gun, fits around the corresponding prominence at the gun grip fixing thereby the spear in the backward longitudinal direction and transversal ly, and wherein at the under side of the middle part of the spear there is a recess into which turning of the spear-release stopper brings its prominence, blocked in that position by the release, which enters into the corresponding release stopper cavity moved by the spring, fixing thereby the spear also in the forward axial direction, in which direction it is pressed by the spear pusher located between the pressure-piston extension and the spear bottom and loaded with the stretched elastic bands force, so that the pusher, which contains grove and non-return valve, enables passage of compressed water through its body in the spear nozzle direction.

3. Underwater spear-gun of Claim 1 , equipped with mechanism for fixing the spear in the gun and for fastening the launching elastic bands, wherein the rear smooth cylindrical part of the spear is inserted into the pressure cylinder and fixed thereby in the transversal direction, and wherein at the under side of the middle part of the spear there is a recess into which turning of the spear-release stopper brings its prominence, blocked in that position by the spear release, which enters into the corresponding spear-release stopper cavity moved by the spring, fixing thereby the spear also in the forward axial direction, in which direction it is also pushed by force of the elastic bands hooked to the notch at the outer lateral side of the spear.

4. Underwater spear-gun of Claims 1 and 2, wherein it is equipped with mechanism for charging the spear which is fixed in the gun, which mechanism is made so that the water driven from the piston pump enters the nozzle through the pressure cylinder with pressure piston and spring, through cavity of the pressure piston and its extension and through the spear pusher cavity and non-return valve, whereby rising of pressure in the pressure cylinder and the pressure piston cavity opens valve in the spear pusher and lets water into the spear, producing at the same time axial forces large enough for good sealing at the points of contact between the spear pusher and the pressure piston extension and the nozzle, and whereby, after pulling of the trigger and accelerating of the spear at its launching, the nozzle separates from the spear pusher and starts letting the water jet out.

5. Underwater spear-gun of Claims 1 and 3, wherein it is equipped with mechanism for charging the spear which is fixed in the gun, which mechanism is made so that the water driven from the piston pump passes through a non-return valve positioned at the pressure cylinder intake and through the very pressure cylinder into the spear nozzle.

6. Underwater spear-gun of Claim 1 , wherein the spear, at its rear end, has ejector extension with sidewise fluid intake, zone of its mixing with the nozzle jet and output of the entire flow backward.