The invention relates to devices for swimming under the surface of water, that is, snorkeling and performing short-term immersions to the depth, and it can be used to observe underwater life in its natural environment.

As a rule, the current level of development of means for snorkeling and performing short-term immersion to the depth is limited to masks equipped with snorkeling tubes which do not involve connection structures to join outside air sources for breathing. There are many variations of full-face masks which in various ways obtain fresh air from surface of water and deduce exhaust air to surface of water. There are many variants of separate half-masks and separate tubes to obtain fresh air from surface of water and to deduce exhaust air to surface of water. In this case, instead of a snorkeling tube, a swimmer can use a mouthpiece of a cylinder with a breathing mixture and obtain the fresh air from the cylinder instead of the surface of water. That is, the source of air will be either exclusively from the surface of water through the tube, or, if instead of the air from the surface of water, it is possible to use the air from the cylinder, then the source of air will be exclusively a cylinder.

There is known a full-face mask for snorkeling which consists of a mask on entire face. The mask upper poption is transparent and its lower portion is opaque. The mask lower poption separates the swimmer’s nose and mouth from the upper portion and forms the breathing chamber. To the lower portion, there is attached a breathing tube, which is output on the side above the user's head [US D335, 322 1993]

There is known an apparatus for breathing under water which consists of a full-face mask The mask upper poption is transparent and its lower portion is opaque. The mask lower poption separates a user’s nose and mouth from the upper portion and forms a breathing chamber. To the lower portion, there is attached a breathing tube, which is output on the side above the user's head. [US 20010013346 Al, B63C11 / 16, 2001]. There is known a snorkeling device consisting of a half-mask rimmed with a built-in breathing tube, which, at its top portion, has an outlet branch directed upward to take in air and deliver it to the space above the water surface, and at its bottom portion the tube has an outlet with a mouthpiece to be put into the user's mouth [US 20130074835 Al, B63C11 / 16, 2013]

There is known a diving device comprising a mask, a breathing tube and a valve with a locking element. The mask size is enlarged, and it completely covers the face of a swimmer. The breathing tube of a curved shape is inserted into the mask. The valve body made in the form of a cylindrical container with three vertical openings is attached to the breathing tube input end. The locking element made in the form of a ball is located in the valve body [RU 2000 109 694, B63C 11/00, 2002].

There is known a mask for swimming equipped with a breathing tube. The mask consists of a half-mask rimmed with a built-in breathing tube which, at its top portion, has an outlet directed upward to take in air and deliver it to the space above the water surface, and at its bottom portion, the tube has an outlet with a mouthpiece to be put into the user's mouth [US 5199421 A, B63C11 / 16, 1993]

The common disadvantage of the above described breathing devices and apparatuses is the impossibility, when in water, to automatically go over from feeding a swimmer with the air of a cylinder to feeding with the air from the surface of water and vice versa from feeding with the air from the surface of water to feeding with the air from a cylinder. A swimmer has to:

- either exclusively use the air from the surface of water (as in all means with the built-in tubes, which are output onto the surface of water, such as the above mentioned full-face masks for snorkeling),

- or exclusively use the air from the cylinder (as in all means with the built-in air tubes connected to the cylinders, that is, in the full-face masks for diving),

- or manually replace one air source by the other under the water on condition of the diver breathing delay, that is, the diver should pull out the mouthpiece of a separate snorkeling tube from his/her mouth and thereafter insert the other mouthpiece, namely, the one of the cylinder air duct into his/her mouth, and vice versa, pull out the mouthpiece of the cylinder air duct from his/her mouth and thereafter insert the other mouthpiece, namely, the one of the snorkeling tube into his/her mouth, which method is usually practiced by the divers applying the half-face types of masks, which are considered the most popular in the world for diving and snorkeling,

- or manually alternate one air source to the other (as in snorkeling tubes and EasyDive adapters named Snorkelator https://easydive.us/valve/ and Nomad https://easvdive.us/nomad/)

The closest to the claimed invention is a full-face snorkeling mask with a breathing tube comprising a full-face transparent mask, the upper portion of which is connected to the breathing tube provided with a float plug to prevent water ingress, and in the lower portion of which there is a valve for ejecting water penetrated into the mask [US D775, 722, 2017].

This mask has the following disadvantages:

- the mask contains a single air source, namely, the one from the outside, when the upper inlet of the breathing tube air duct being at the overwater position,

- under condition of immersing or when the upper inlet of the air duct being covered with the water, the possibility of supplying air into the mask disappears,

- the absence of the possibility for increasing the pressure inside the mask when immersed, including due to an autonomous air source, results in pressing the mask onto the face of the swimmer with increasing depth of immersion. Since the external pressure onto the mask increases, and the internal pressure in the mask remains at a constant level, respectively, the difference pressure is not distributed throughout the face of the swimmer, but presses thereon around the perimeter of the contact area of the mask sealers with the swimmer face, which fact can even lead to appearing hematoma in those areas.

The object of the invention is to create a device for fast automatic transition of a breathing air source from the outside air to the air from a cylinder in the event of limiting the availability of the outside air, as well as from the air from a cylinder to the outside air when the outside air becomes available, which device would provide increasing the period of time for swimmer immersion, leveling pressure inside the mask while immersing, reducing consumption of breathing mixture from autonomous sources.

The problem is solved by the fact that in a device for automatically alternating an air source in a snorkeling masks, which device comprises a full-face mask with a breathing tube attached thereto and provided with a built-in float plug to ensure the possibility of blocking a breathing channel· in the case of raising water level above an upper outlet of the breathing cannel, according to the invention, in a lower portion of the mask, there is located a pressure regulator with an air mixture cylinder attached thereto and an adapter installed thereon.

In the claimed device, there is no need for any swimmer action to go over from the outside air to the air from the cylinder while immersing, being covered by waves and in other cases when the access to the swimmer input air duct, namely, to the swimmer mask tube, is blocked with water, provided that such a locking leads to mechanical blockage of the air duct with the float plug. That is, in any event, when the raising water level lifts the float to the inlet of the air duct, the internal air pressure at the moment of inhaling in the mask decreases so that the valve for air intake from the cylinder would be automatically open. In the claimed device there is no need for any swimmer action to go over from the cylinder air to the outside air when the outside air becomes available at the input air duct and the float plug releases the air duct inlet. That is, in any case, when the water level becomes lower, than the position of the float plug lifted to the inlet, and the float plug opens the inlet, the internal air pressure at the moment of inhaling in the mask increases so that the pressure difference would not become sufficient for allowing the air to flow from the cylinder, and such a feed cannot occur, and the air comes to the mask from outside.

The claimed device for automatically alternating the source of air in masks allows:

- automatically go over from the outside air source to the cylinder air at conscious immersion, provided that the inlet opening of the air duct is plugged with a float built into the tube when the water level becomes higher than the position of the float plug built into the tube, as well as such an inlet opening;

- automatically go over from the outside air source to the cylinder air in the event of an unexpected immersion, for example, when a swimmer is covered by waves, provided that the inlet opening of the air duct is plugged with a float built into the tube when the water level becomes higher than the position of the float plug built into the tube, as well as such an inlet opening;

- automatically go over from the outside air source to the cylinder air in the event of a forced immersion, for example, to avoid collisions or at decreasing buoyancy, provided that the inlet opening of the air duct is plugged with a float built into the tube when the water level becomes higher than the position of the float plug built into the tube, as well as such an inlet opening;

- automatically go over from the cylinder air source to the outside air, provided that the air duct inlet opening is released by the float, when the water level falls below the level of locating the float plug built into the tube, as well as such an inlet opening;

- use the device as a lifesaver on difficult weather conditions when there is a risk for swimmers to be covered with waves;

- apply the device for leisure and recreation by diving in the course of snorkeling without a swimmer delay of breathing, that is, using the air from the cylinder attached to the mask.

The invention is explained by the following drawings:

FIG. 1 is a front view of a device for automatically alternating air source in snorkeling mask; FIG. 2 is a rear view of a device for automatically alternating air source in snorkeling mask;

FIG. 3 is a section view of a device for automatically alternating air source in snorkeling mask.

The device for automatically alternating air source in snorkeling mask comprises full-face mask 1, on the top portion of which there is attached snorkeling tube 2 with built-in float plug 3, adapter 4 positioned on and designed for connecting pressure regulator 5 mounted on cylinder 6 filled with a compressed breathing mixture, a breathing channel with an upper breathing inlet opening 7 formed with lid 8 of the tube.

The device operates as follows.

The beginning of the process of inhaling air in mask 1 results in reducing pressure in mask 1, adapter 4, tube 2and the air chamber formed by lid 8 of the tube. If float plug 3 is not lifted up by the water to the level of the upper breathing opening of breathing channel 7, the air enters through upper breathing channel 7, passes the air chamber formed by lid 8 of the tube and enters mask 1 through tube 2. When the water level lifts float plug 3 to the level of the upper breathing opening of breathing channel 7 and blocks it, the continuation of the process of inhalation even leads to further reducing the pressure in mask 1 , adapter 4, tube 2 and the air chamber formed by lid 8 of the tube. Further reducing the pressure results in opening pressure regulator 5 and introducing the breathing mixture (the air or other kind of breathing mixture) from cylinder 6 where it is stored in a compressed state. On completing the process of inhaling air, the value of the pressure in mask 1, adapter 4, tube 2 and the air chamber formed by lid 8 of the tube, due to the outside air coming through the upper breathing opening of breathing channel 7 or the air mixture of cylinder 6 coming from pressure regulator 5 through adapter 4, is aligned in accordance with the conditions of the environment, and the process of entering either the air from outside through the upper breathing opening of breathing channel 7 or the air mixture from cylinder 6 stops. The process of exhaling into mask 1 leads to increasing the value of pressure in mask 1, adapter 4, tube 2 and the air chamber formed by lid 8 of the tube. The alignment of the pressure in accordance with the conditions of the environment is performed due to outflowing the air outside through the upper breathing opening of breathing channel 7 and / or through pressure regulator 5. Moreover, the air outflow through the upper breathing opening of breathing channel 7 is possible as in the case when the water level is below float-plug 3 and the last does not close the upper breathing opening of breathing channel 7, as in the event when the water level lifts float plug 3 to the level of the upper breathing opening of breathing channel 7 and blocks it from inletting water inside the mask. In the latter case, the excess air, which requires its outflow to equalize the pressure, pushes float plug 3 away from the upper breathing opening of breathing channel 7 and forms a slit through which the excess air is released. The slit will be closed as soon as the excess air has been exhausted, and the external pressure on float-plug 3 has returned it to the function of blocking the upper breathing opening of breathing channel 7.