CN113877179A - Ball serving equipment for sports tennis training - Google Patents

Abstract

The invention relates to the technical field of tennis auxiliary equipment, and discloses a serving device for sports tennis training, which comprises: the tennis ball launching device comprises a plurality of bearing plates, rails, a ball launching mechanism, a microprocessor and a power supply, wherein the bearing plates are sequentially spliced into a whole and cover the ground of a tennis ball field, the ground below the bearing plates is provided with a groove, a first ball outlet is formed in each bearing plate, a cover plate for sealing the first ball outlet is hinged to the hole wall of the first ball outlet, each bearing plate is provided with a sensing element, the rails are arranged in the grooves in a direction parallel to the tennis ball field, the rails pass through the positions under the first ball outlet and are connected with sliders through driving mechanisms, the ball launching mechanism is fixedly connected onto the sliders, and the microprocessor is respectively in signal connection with the sensing elements, the driving mechanisms and the ball launching mechanism. The tennis ball throwing device can simulate the serve of a hand of a person at the position of a trainer under the condition of not occupying a ground field, so that tennis balls are vertically and upwards thrown.

Description

Ball serving equipment for sports tennis training

Technical Field

The invention relates to the technical field of tennis auxiliary equipment, in particular to service equipment for sports tennis training.

Background

The first step of single person training in tennis training is pitching, which means that the tennis ball is thrown out first, and then the trainer swings to beat and hit the ball, so that the throwing is the first element for the trainer to hit the ball accurately.

Many tennis service robots have been developed to assist in personal training by moving the service robot to the proper position to throw a tennis ball from the service robot to allow the trainer to complete the ball hitting action.

Because the pitching machine has a certain volume and cannot be placed at a position which is particularly close to the trainer, the pitching machine generally needs to be at least about 2 meters away from the trainer, the trainer can not hit the pitching machine when swinging, therefore, the ball sent by the pitching machine has to have a larger inclination angle so as to ensure that the ball can reach the position above the position of the trainer to enable the trainer to successfully complete the ball receiving, and in most cases, the trainer needs to timely move to the position of the ball according to the pitching position of the pitching machine to complete the ball hitting action, the standard ball serving posture is that after a trainer stands, the trainer throws the ball upwards, generally the ball is vertically upwards or only slightly deflected, and then the ball is hit, the ball sent by the existing service robot is often inclined to a greater degree, and cannot form a real ball throwing track, further resulting in the discrepancy between the follow-up bat hitting and the real match, which affects the training quality and efficiency.

Disclosure of Invention

The invention provides a ball serving device for sports tennis training, which can simulate the serving of a hand of a trainer at the position of the trainer under the condition of not influencing the training space of the trainer so as to enable tennis to be thrown upwards vertically.

The invention provides a service device for sports tennis training, which comprises:

the tennis ball bearing comprises a plurality of bearing plates, a plurality of bearing plates and a plurality of clamping pieces, wherein the bearing plates are sequentially spliced into a whole and cover the ground of a tennis court, the ground below the bearing plates is provided with a groove, the bearing plates are provided with a first ball outlet, the hole wall of the first ball outlet is hinged with a cover plate for closing the first ball outlet, the cover plate is opened in a single direction, each bearing plate is provided with an induction element, and the induction elements are used for inducing whether a person is positioned on the current bearing plate;

the tracks are arranged in the grooves along the direction parallel to the tennis court, pass through the positions right below the first ball outlet holes, and are connected with sliding blocks through driving mechanisms so as to drive the sliding blocks to move along the tracks;

the ball serving mechanism is fixedly connected to the sliding block and is used for throwing the tennis balls in the vertical direction;

the microprocessor is respectively in signal connection with the sensing element, the driving mechanism and the ball serving mechanism, when the sensing element senses a person, the microprocessor controls the driving mechanism to drive the sliding block to move along the track to be right below the first ball outlet on the bearing plate where the sensing element is located, and then controls the ball serving mechanism to throw out tennis balls in the vertical direction;

and the power supply is electrically connected with the driving mechanism, the ball serving mechanism and the microprocessor respectively.

Optionally, the cover plate is hinged to the hole wall of the first ball outlet hole through a hinged shaft, the hinged shaft drives the first ball outlet hole to rotate through a steering engine, and the microprocessor is in signal connection with the steering engine to control the steering engine to drive the cover plate to open upwards or close the first ball outlet hole downwards.

Optionally, the upper surface of each bearing plate is further provided with two foot treading areas.

Optionally, the sensing element includes:

the first pressure sensor is arranged on the cover plate and used for detecting a first pressure value born by the cover plate;

the second pressure sensor is arranged in any foot treading area on each bearing plate and used for detecting a second pressure value born by the foot treading area, the first pressure sensor and the second pressure sensor are respectively in signal connection with the microprocessor, when a first pressure value detected by the first pressure sensor and a second pressure value detected by the second pressure sensor are both greater than a preset value, the microprocessor controls the driving mechanism to drive the sliding block to move along the track to be right below the first ball outlet hole in the bearing plate where the first pressure sensor and the second pressure sensor are located, and then the ball serving mechanism is controlled to throw out the tennis balls in the vertical direction.

Optionally, the service mechanism comprises:

the mounting box is fixed on the sliding block, a cavity is formed in the mounting box, and a second ball outlet hole is formed in the upper end face of the mounting box;

the tennis ball storage barrel is obliquely fixed in the mounting box, a plurality of tennis balls are placed in the tennis ball storage barrel side by side, a ball inlet is formed in one side end of the tennis ball storage barrel, a ball outlet is formed in the upper end face of the tennis ball storage barrel, the ball outlet is communicated with the second ball outlet through a vertically arranged pipeline, a through hole is formed in the lower end face of the tennis ball storage barrel, the through hole is located right below the ball outlet, and the aperture of the through hole is smaller than the diameter of each tennis ball;

the pushing assembly is arranged in the installation box and located right below the through hole, the microprocessor is in signal connection with the pushing assembly to control the pushing assembly to vertically push the tennis balls at the through hole upwards for a fixed distance, and the pushing assembly is electrically connected with the power supply.

Optionally, the pushing assembly includes:

the air pump is fixed in the installation box and is in signal connection with the microprocessor, and the air pump is electrically connected with the power supply;

and the vent pipe is fixedly connected with the air outlet of the air pump, is vertically arranged and is fixedly connected with the ball outlet.

Optionally, be provided with the separation subassembly that changes its flow area on the breather pipe, the ventilation volume of breather pipe is changed through the flow area who changes the breather pipe to the separation subassembly.

Optionally, the barrier assembly comprises:

the plugging plate is in sliding fit with a notch horizontally formed in the vent pipe;

electric telescopic handle is fixed in on the lateral wall of install bin, and the electric telescopic handle level sets up, and electric telescopic handle's flexible head links firmly with the shutoff board, microprocessor and electric telescopic handle signal connection to control electric telescopic handle's flexible, electric telescopic handle is connected with the power electricity.

Optionally, the lower end of the first ball outlet is fixedly connected with a ball inlet cylinder.

Optionally, the ball inlet cylinder is a horn-shaped cylinder with a large upper part and a small lower part.

Compared with the prior art, the invention has the beneficial effects that: the tennis court is divided into a plurality of plates by covering a layer of bearing plate on the tennis court, when a trainer stands on one of the bearing plates, the induction element is triggered to induce the trainer to sense a person, the microprocessor controls the sliding block to move along the track to be under the position of the current bearing plate, then the ball serving mechanism is controlled to vertically and upwards throw tennis balls to finish ball throwing action, and then the trainer swings and hits the balls to finish the ball throwing action. The ball can not be affected by the trainers on the field during the service.

Drawings

Fig. 1 is a front view of a service apparatus for training sports tennis according to an embodiment of the present invention;

FIG. 2 is a top view of a serving apparatus for sports tennis training in accordance with an embodiment of the present invention;

FIG. 3 is a schematic structural diagram of a ball serving mechanism according to an embodiment of the present invention;

fig. 4 is a schematic diagram illustrating a service state of a service apparatus for training sports tennis according to an embodiment of the present invention.

Description of reference numerals:

10-bearing plate, 11-tennis court, 12-groove, 13-first ball outlet, 14-cover plate, 15-sensing element, 150-first pressure sensor, 151-second pressure sensor, 16-hinge shaft, 17-foot treading area, 18-ball inlet cylinder, 20-track, 21-slide block, 30-ball serving mechanism, 300-installation box, 301-cavity, 302-second ball outlet, 303-ball storage cylinder, 304-ball outlet, 305-pipeline, 306-through hole, 307-tennis ball, 31-pushing component, 310-air pump, 311-air pipe, 32-blocking component, 320-blocking plate and 321-electric telescopic rod.

Detailed Description

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings, but it should be understood that the scope of the present invention is not limited to the embodiment.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of describing technical solutions of the present invention and simplifying the description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.

As shown in fig. 1-2, a service device for training sports tennis according to an embodiment of the present invention includes: the tennis ball launching device comprises a plurality of bearing plates 10, a track 20, a ball serving mechanism 30, a microprocessor and a power supply, wherein the bearing plates 10 are sequentially spliced and connected into a whole and cover the ground of a tennis court 11, the ground below the bearing plates 10 is provided with a groove 12, the bearing plates 10 are provided with a first ball outlet 13, the wall of the first ball outlet 13 is hinged with a cover plate 14 for closing the first ball outlet 13, the cover plate 14 is opened in a single direction, each bearing plate 10 is provided with a sensing element 15, the sensing element 15 is used for sensing whether a person is positioned on the current bearing plate 10, the track 20 is distributed in the groove 12 along the direction parallel to the tennis court 11, the track 20 passes through the position under each first ball outlet 13, the track 20 is connected with a slide block 21 through a driving mechanism so as to drive the slide block 21 to move along the track 20, the ball serving mechanism 30 is fixedly connected to the slide block 21, the ball serving mechanism 30 is used for throwing a tennis ball 307 along the vertical direction, the microprocessor is respectively connected with the sensing element 15, the driving mechanism and the ball serving mechanism 30 through signals, when the sensing element 15 senses a person, the microprocessor controls the driving mechanism to drive the sliding block 21 to move along the track 20 to be right below the first ball outlet 13 on the bearing plate 10 where the sensing element 15 is located, then the ball serving mechanism 30 is controlled to throw the tennis ball 307 along the vertical direction, the power supply is respectively electrically connected with the driving mechanism, the ball serving mechanism 30 and the microprocessor, in the embodiment, the cover plate 14 is ejected after the tennis ball 307 is thrown upwards, and the cover plate 14 automatically closes the first ball outlet 13 after the tennis ball 307 is thrown from the first ball outlet 13.

The tennis court is divided into a plurality of plates by covering a layer of bearing plate on the tennis court, when a trainer stands on one of the bearing plates, the induction element is triggered to induce the trainer to sense a person, the microprocessor controls the sliding block to move along the track to be under the position of the current bearing plate, then the ball serving mechanism is controlled to vertically and upwards throw tennis balls to finish ball throwing action, and then the trainer swings and hits the balls to finish the ball throwing action. The ball can not be affected by the trainers on the field during the service.

In order to avoid that the cover plate 14 is required to be jacked up when the tennis ball 307 is thrown upwards to avoid the blockage of the cover plate 14, so that the upward movement speed of the tennis ball 307 is reduced, and the throwing height of the tennis ball is influenced, in the embodiment, the cover plate 14 is hinged to the hole wall of the first ball outlet hole 13 through the hinge shaft 16, the hinge shaft 16 is driven to rotate through the steering engine, the microprocessor is in signal connection with the steering engine to control the steering engine to drive the cover plate 14 to open upwards or close downwards the first ball outlet hole 13, when the ball serving mechanism 30 moves to the position below the bearing plate 10, the microprocessor controls the steering engine to drive the hinge shaft 16 to rotate so as to turn the cover plate 14 upwards, and after the ball serving mechanism 30 finishes a ball serving action, the microprocessor controls the steering engine again to drive the hinge shaft 16 to rotate reversely so as to enable the cover plate 14 to close downwards the first ball outlet hole 13.

In this embodiment, the upper surface of each bearing plate 10 further has two foot stepping areas 17, and when a trainer needs to assist in serving a tennis, the trainer stands on the foot stepping areas 17 of a certain bearing plate 10 with both feet respectively, so that the position of throwing the tennis is more accurate to the position of the trainer, and the position of throwing the tennis 307 by the trainer is further ensured to be consistent with the actual manual throwing.

Specifically, the inductive element 15 includes: the tennis ball launching device comprises a first pressure sensor 150 and a second pressure sensor 151, wherein the first pressure sensor 150 is arranged on a cover plate 14 and used for detecting a first pressure value borne by the cover plate 14, the second pressure sensor 151 is arranged on any one foot treading area 17 on each bearing plate 10 and used for detecting a second pressure value borne by the foot treading area 17, the first pressure sensor 150 and the second pressure sensor 151 are respectively in signal connection with a microprocessor, when the first pressure value detected by the first pressure sensor 150 and the second pressure value detected by the second pressure sensor 151 are both greater than a preset value, the microprocessor controls a driving mechanism to drive a sliding block 21 to move along a track 20 to be positioned right below a first ball outlet 13 on the bearing plate 10 where the first pressure sensor 150 and the second pressure sensor 151 are positioned, and then controls a ball launching mechanism 30 to throw a tennis ball 307 in the vertical direction.

Because the trainer may trigger the sensing element 15 to cause unnecessary serve during the training process, in the embodiment, the first pressure sensor 150 and the second pressure sensor 151 are arranged on the foot stepping area 17 on the cover plate 14, and only when the trainer steps on the first pressure sensor 150 with one foot and steps on the second pressure sensor 151 with the other foot, the microprocessor can trigger the serving mechanism 30 to serve after receiving two pressure values at the same time, thereby avoiding the condition of mistaken serving during the training process.

Referring to fig. 3, the service mechanism 30 includes: the tennis ball pushing device comprises a mounting box 300, a tennis ball storage barrel 303 and a pushing assembly 31, wherein the mounting box 300 is fixed on a sliding block 21, a cavity 301 is arranged in the mounting box 300, a second tennis ball outlet 302 is arranged on the upper end surface of the mounting box 300, the tennis ball storage barrel 303 is obliquely fixed in the mounting box 300, a plurality of tennis balls 307 are placed in the tennis ball storage barrel 303 side by side, a tennis ball inlet is arranged at one side end of the tennis ball storage barrel 303, a tennis ball outlet 304 is arranged on the upper end surface of the tennis ball storage barrel 303, the tennis ball outlet 304 is communicated with the second tennis ball outlet 302 through a vertically arranged pipeline 305, a through hole 306 is arranged on the lower end surface of the tennis ball storage barrel 303, the through hole 306 is positioned right below the tennis ball outlet 304, the diameter of the through hole 306 is smaller than the diameter of the tennis ball 307, the pushing assembly 31 is arranged in the mounting box 300, the pushing assembly 31 is positioned right below the through hole 306, the microprocessor is in signal connection with the pushing assembly 31 to control the pushing assembly 31 to vertically push the tennis balls 307 at the through hole 306 upwards for a fixed distance, the pushing assembly 31 is electrically connected with a power supply, and the pushing assembly 31 comprises: air pump 310 and breather pipe 311, air pump 310 are fixed in install bin 300, with microprocessor signal connection, air pump 310 and power electrical connection, breather pipe 311 links firmly with the gas outlet of air pump 310, breather pipe 311 vertical setting and with go out the ball mouth 304 and link firmly.

The working principle is as follows: after the mounting box 300 slides to a target position, the microprocessor controls the air pump 310 to open, and then the air with impact force is ejected upwards along the vent pipe 311, so that the tennis ball 307 at the through hole 306 sequentially passes through the ball outlet 304, the second ball outlet 302 and the first ball outlet 13, and in this embodiment, the ejection height of the tennis ball 307 can be controlled by presetting the air output of the air pump 310, and because the tennis ball 307 is inclined, the tennis ball 307 automatically slides along the length direction of the tennis ball storage tube 303 under the action of gravity, after one tennis ball 307 is ejected, another tennis ball 307 automatically moves to the through hole 306, so that the next serving is not affected, and no additional auxiliary device is needed to move the tennis ball.

In order to meet the requirement of the tennis ball serving height in different training stages, in the embodiment, the ventilation pipe 311 is provided with the blocking assembly 32 for changing the flow area thereof, and the blocking assembly 32 changes the ventilation amount of the ventilation pipe 311 by changing the flow area of the ventilation pipe 311, so that the impact force on the tennis ball 307 can be changed by changing the ventilation amount of the ventilation pipe 311, and further, the throwing height of the tennis ball 307 can be changed.

Optionally, the barrier assembly 32 comprises: plugging plate 320 and electric telescopic handle 321, the notch sliding fit that the level was seted up on plugging plate 320 and the breather pipe 311, electric telescopic handle 321 is fixed in on the lateral wall of install bin 300, electric telescopic handle 321 level sets up, electric telescopic handle 321's the flexible head links firmly with plugging plate 320, microprocessor and electric telescopic handle 321 signal connection to control electric telescopic handle 321's flexible, electric telescopic handle 321 is connected with the power electricity.

The microprocessor controls the telescopic length of the electric telescopic rod 321 to change the area of the blocking plate 320 entering the vent pipe 311, so that the impact force on the tennis ball 307 can be changed by changing the ventilation volume of the vent pipe 311, and the throwing height of the tennis ball 307 can be further changed.

Optionally, the lower end of the first ball outlet hole 13 is fixedly connected to the ball inlet tube 18, so that the tennis ball 307 can be smoothly thrown out of the first ball outlet hole 13 without deviation.

Optionally, the goal barrel 18 is a trumpet-shaped barrel with a large top and a small bottom, so as to facilitate the entry of tennis balls 307.

The use method and the working principle are as follows:

referring to fig. 4, when a user steps on the cover plate 14 and steps on the foot stepping area 17 of the same carrier plate 10, which is provided with the second pressure sensor 151, with one foot of the user, the microprocessor controls the driving mechanism to drive the slider 21 to move along the track 20 to a position right below the first ball outlet 13 on the carrier plate 10 where the first pressure sensor 150 and the second pressure sensor 151 are located, the microprocessor controls the steering engine to drive the hinge shaft 16 to rotate so as to turn the cover plate 14 upwards, then controls the air pump 310 to open, and then the air with impact force is ejected upwards along the vent pipe 311, so that the tennis ball 307 at the through hole 306 is ejected upwards through the ball outlet 304, the second ball outlet 302 and the first ball outlet 13 in sequence, after the ball serving mechanism 30 finishes the ball serving action, the microprocessor controls the steering engine again to drive the hinge shaft 16 to rotate reversely, so that the cover plate 14 closes the first ball outlet hole 13 downwards.

The above disclosure is only for a few specific embodiments of the present invention, however, the present invention is not limited to the above embodiments, and any variations that can be made by those skilled in the art are intended to fall within the scope of the present invention.

Claims (10)

1. A service apparatus for sports tennis training, comprising:

the tennis court comprises a plurality of bearing plates (10), wherein the bearing plates (10) are sequentially spliced into a whole and cover the ground of the tennis court (11), the ground below the bearing plates (10) is provided with a groove (12), the bearing plates (10) are provided with a first ball outlet (13), the wall of the first ball outlet (13) is hinged with a cover plate (14) for closing the first ball outlet (13), the cover plate (14) is opened in a single direction, each bearing plate (10) is provided with an induction element (15), and the induction elements (15) are used for inducing whether a person is positioned on the current bearing plate (10);

the tracks (20) are arranged in the grooves (12) along a direction parallel to the tennis court (11), the tracks (20) pass through the positions right below the first ball outlet holes (13), and the tracks (20) are connected with sliding blocks (21) through driving mechanisms so as to drive the sliding blocks (21) to move along the tracks (20);

the ball serving mechanism (30) is fixedly connected to the sliding block (21), and the ball serving mechanism (30) is used for throwing the tennis ball (307) in the vertical direction;

the microprocessor is respectively in signal connection with the sensing element (15), the driving mechanism and the ball serving mechanism (30), when the sensing element (15) senses a person, the microprocessor controls the driving mechanism to drive the sliding block (21) to move along the track (20) to be right below a first ball outlet (13) on the bearing plate (10) where the sensing element (15) is located, and then controls the ball serving mechanism (30) to throw the tennis ball (307) in the vertical direction;

and the power supply is electrically connected with the driving mechanism, the ball serving mechanism (30) and the microprocessor respectively.

2. The serving device for sports tennis training according to claim 1, wherein the cover plate (14) is hinged to the wall of the first ball outlet (13) through a hinge shaft (16), the hinge shaft (16) is driven to rotate by a steering engine, and the microprocessor is in signal connection with the steering engine to control the steering engine to drive the cover plate (14) to open the first ball outlet (13) upwards or close the first ball outlet (13) downwards.

3. A sports tennis training serving apparatus as claimed in claim 1, wherein each of said carrying plates (10) further has two foot stepping areas (17) on its upper surface.

4. A serving device for sports tennis training according to claim 3, wherein said sensing element (15) comprises:

the first pressure sensor (150) is arranged on the cover plate (14) and used for detecting a first pressure value born by the cover plate (14);

a second pressure sensor (151) provided on any one of the foot stepping areas (17) on each of the carrier plates (10), is used for detecting a second pressure value born by the foot treading area (17), the first pressure sensor (150) and the second pressure sensor (151) are respectively connected with the microprocessor through signals, when a first pressure value detected by the first pressure sensor (150) and a second pressure value detected by the second pressure sensor (151) are both larger than a preset value, the microprocessor controls the driving mechanism to drive the sliding block (21) to move along the track (20) to a position right below a first ball outlet hole (13) on the bearing plate (10) where the first pressure sensor (150) and the second pressure sensor (151) are located, and then controls the ball serving mechanism (30) to throw the tennis ball (307) in the vertical direction.

5. A serving apparatus for sports tennis training according to claim 1, wherein said serving mechanism (30) comprises:

the mounting box (300) is fixed on the sliding block (21), a cavity (301) is formed in the mounting box (300), and a second ball outlet hole (302) is formed in the upper end face of the mounting box (300);

the tennis ball storage barrel (303) is obliquely fixed in the mounting box (300), a plurality of tennis balls (307) are placed in the tennis ball storage barrel (303) side by side, a ball inlet is formed in one side end of the tennis ball storage barrel (303), a ball outlet (304) is formed in the upper end face of the tennis ball storage barrel (303), the ball outlet (304) is communicated with the second ball outlet (302) through a vertically arranged pipeline (305), a through hole (306) is formed in the lower end face of the tennis ball storage barrel (303), the through hole (306) is located right below the ball outlet (304), and the aperture of the through hole (306) is smaller than the diameter of the tennis ball (307);

the pushing assembly (31) is arranged in the installation box (300), the pushing assembly (31) is located right below the through hole (306), the microprocessor is in signal connection with the pushing assembly (31) to control the pushing assembly (31) to vertically push the tennis ball (307) at the through hole (306) upwards for a fixed distance, and the pushing assembly (31) is electrically connected with the power supply.

6. Serving apparatus for sports tennis training according to claim 5, wherein said pushing assembly (31) comprises:

the air pump (310) is fixed in the installation box (300) and is in signal connection with the microprocessor, and the air pump (310) is electrically connected with the power supply;

the air pipe (311) is fixedly connected with an air outlet of the air pump (310), and the air pipe (311) is vertically arranged and fixedly connected with the ball outlet (304).

7. Serving apparatus for sports tennis training according to claim 6, wherein said ventilation tube (311) is provided with a blocking member (32) for varying its flow area, said blocking member (32) varying the ventilation volume of said ventilation tube (311) by varying the flow area of said ventilation tube (311).

8. A serving apparatus for sports tennis training according to claim 7, wherein said blocking member (32) comprises:

the plugging plate (320) is in sliding fit with a groove opening horizontally formed in the vent pipe (311);

electric telescopic handle (321), be fixed in on the lateral wall of install bin (300), electric telescopic handle (321) level sets up, the flexible head of electric telescopic handle (321) with shutoff board (320) link firmly, microprocessor with electric telescopic handle (321) signal connection, in order to control electric telescopic handle (321) flexible, electric telescopic handle (321) with the power electricity is connected.

9. A service apparatus for sports tennis training according to claim 1, wherein the lower end of said first ball outlet hole (13) is attached with a ball inlet tube (18).

10. A service apparatus for sports tennis training according to claim 9, wherein said inlet tube (18) is a trumpet having a large top and a small bottom.

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