阅读说明：本技术 用于咖啡机的奶泡发生装置 (Milk foam generating device for coffee machine ) 是由 俞操 于 2021-08-18 设计创作，主要内容包括：本发明公开了一种用于咖啡机的奶泡发生装置,其特征在于：包括有奶泡机(1),具有负压腔(101)、蒸汽插口(102)、空气插口(103)、进奶通道(104)和出奶通道(105),所述蒸汽插口(102)、空气插口(103)、进奶通道(104)的出口以及出奶通道(105)的入口连通所述的负压腔(101)；进汽装置(2),安装在所述的咖啡机上,具有能够插设到所述蒸汽插口(102)中的蒸汽接头(21)；以及进气装置(3),安装在所述的咖啡机上,具有能够插设到所述空气插口(103)中的空气接头(31)。与现有技术相比,本发明的奶泡发生装置便于装卸和清洗奶泡机。(The invention discloses a milk foam generating device for a coffee machine, which is characterized in that: the milk frother comprises a milk frother (1) which is provided with a negative pressure cavity (101), a steam socket (102), an air socket (103), a milk inlet channel (104) and a milk outlet channel (105), wherein the steam socket (102), the air socket (103), an outlet of the milk inlet channel (104) and an inlet of the milk outlet channel (105) are communicated with the negative pressure cavity (101); a steam inlet device (2) which is arranged on the coffee machine and is provided with a steam joint (21) which can be inserted into the steam socket (102); and an air inlet device (3) which is arranged on the coffee machine and is provided with an air connector (31) capable of being inserted into the air insertion opening (103). Compared with the prior art, the milk foam generating device is convenient to assemble, disassemble and clean the milk foam machine.)

1. A milk foam generating device for a coffee machine, characterized in that: comprises that

The milk frother (1) is provided with a negative pressure cavity (101), a steam socket (102), an air socket (103), a milk inlet channel (104) and a milk outlet channel (105), wherein the steam socket (102), the air socket (103), an outlet of the milk inlet channel (104) and an inlet of the milk outlet channel (105) are communicated with the negative pressure cavity (101);

a steam inlet device (2) which is arranged on the coffee machine and is provided with a steam joint (21) which can be inserted into the steam socket (102); and

an air inlet device (3) is arranged on the coffee machine and is provided with an air connector (31) which can be inserted into the air insertion opening (103).

2. The foamed milk generating apparatus according to claim 1, wherein: the air inlet device (3) comprises a fixed support (33), an air inlet channel (332) is arranged in the air inlet device, and an outlet of the air inlet channel (332) is communicated with the air connector (31) through an air conveying pipe (32);

the first air inlet piece (34) is fixed relative to the fixed bracket (33), covers the inlet of the air inlet channel (332), and is provided with a first flow through hole (341) at an eccentric position;

a rotating bracket (35) rotatably mounted on the fixed bracket (33);

the second air inlet piece (36) is fixed relative to the rotating bracket (35), a second flow hole (361) corresponding to the first flow hole (341) is formed in the eccentric position, and the second flow hole (361) is communicated with the outside atmosphere; and

and the knob (37) is arranged on the rotating bracket (35) and used for driving the rotating bracket (35) to rotate relative to the fixed bracket (33) so as to enable the second through hole (361) and the first through hole (341) to be in a communication or blocking state.

3. The milk foam generating apparatus according to claim 2, wherein: one end of the fixed support (33) facing the rotating support (35) is provided with a gear part (333), and the gear part (333) is provided with a first gear groove (3331), a second gear groove (3332) and a third gear groove (3333) at intervals along the circumferential direction;

the air inlet device (3) also comprises an elastic gear part (38), the gear part (38) is fixed relative to the rotating bracket (35), a convex part (381) is arranged on the gear part (38), and the convex part (381) always tends to be abutted against the gear part (333);

when the projection (381) is moved to a position of the shift position groove, the projection (381) can be inserted into the corresponding shift position groove by an elastic force.

4. The milk foam generating apparatus according to claim 3, wherein: a first conducting strip (3334), a second conducting strip (3335) and a third conducting strip (3336) are mounted on the fixed support (33), and at least part of the first conducting strip (3334), part of the second conducting strip (3335) and part of the third conducting strip (3336) extend into the first gear groove (3331), the second gear groove (3332) and the third gear groove (3333) respectively;

the milk foam generating device has at least three working states:

in a first working state, the convex part (381) of the gear piece (38) is inserted into the first gear groove (3331) and is electrically connected with the first conducting strip (3334), the second flow through hole (361) is communicated with the first flow through hole (341), and the milk inlet channel (104) is communicated with milk raw materials;

in a second working state, the convex part (381) of the gear piece (38) is inserted into the second gear groove (3332) and is electrically connected with the second conducting strip (3335), the second flow through hole (361) and the first flow through hole (341) are in a blocking state, and the milk inlet channel (104) is communicated with milk raw materials;

in a third working state, the convex part (381) of the gear piece (38) is inserted into the third gear groove (3333) and is electrically connected with the third conducting strip (3336), the second flow through hole (361) and the first flow through hole (341) are in a blocking state, and the milk inlet channel (104) is not communicated with milk raw materials.

5. The milk foam generating apparatus according to claim 3, wherein: the wall surface of the gear part (333) between two adjacent gear grooves is a convex cambered surface.

6. The milk foam generating apparatus according to claim 3, wherein: an indication rod (371) corresponding to the following convex part (381) is convexly arranged on the peripheral wall of the knob (37) and used for indicating the rotating position of the convex part (381).

7. The milk foam generating apparatus according to claim 2, wherein: the fixed support (33) is provided with a containing groove (331) communicated with the air inlet channel (332), and the first air inlet piece (34) and the second air inlet piece (36) are both arranged in the containing groove (331).

8. The foamed milk generating apparatus according to claim 7, wherein: the peripheral wall of the containing groove (331) is provided with a limit groove (3311) along the axial direction, the first air inlet part (34) is sheet-shaped, the edge position of the first air inlet part (34) is convexly provided with a limit block (342), and the limit block (342) is inserted in the limit groove (3311) and can slide along the axial direction.

9. Milk foam generating device according to any of the claims 1 to 8, characterized in that: the coffee machine also comprises a reminding device (4) arranged on the coffee machine, wherein the reminding device (4) comprises a click pin (42) and an elastic piece (43) which can enable the head of the click pin (42) to always have the tendency of moving towards the direction of the steam joint (21) or the air joint (31);

the side part of the milk foaming machine (1) is provided with a convex inserting nozzle (131), the steam inserting opening (102) and the air inserting opening (103) are both arranged on the inserting nozzle (131), and the inserting nozzle (131) is provided with a positioning groove (1311) for inserting the head part of the tick pin (42);

the head of the click pin (42) is inserted into the positioning groove (1311) in a state where the nozzle (131) is inserted in place.

10. Milk foam generating device according to any of the claims 1 to 8, characterized in that: the coffee maker also comprises a microswitch (5) arranged on the coffee maker, wherein the microswitch (5) is provided with a contact (51) and an elastic sheet (52) capable of extruding the contact (51);

the side part of the milk foaming machine (1) is provided with a convex inserting nozzle (131), and the steam inserting opening (102) and the air inserting opening (103) are both arranged on the inserting nozzle (131);

when the plug (131) is separated from the steam connector (21) and the air connector (31), the elastic sheet (52) releases the contact (51) to disconnect the microswitch (5);

under the state that the plug nozzle (131) is inserted in place, the elastic sheet (52) pushes the contact (51) under the poking of the plug nozzle (131) so as to close the microswitch (5).

Technical Field

The invention relates to the technical field of coffee equipment, in particular to a milk foam generating device for a coffee machine.

Background

When coffee is drunk, the coffee is matched with smooth and exquisite milk foam, the taste and the texture of the coffee can be improved, a good decoration effect can be achieved, and the milk foam is a product formed by mixing milk and air compactly. The device for making the milk foam has various structural forms.

The first is to fill the cup directly with cold milk and prepare frothed milk using a steam wand nozzle attached directly to a steam tube. The fineness and the softness of the milk foam are very critical, the steam stick is inserted below the milk liquid level when the milk foam is used, air is not convenient to supplement, and in order to obtain proper air, an operator needs to shake the milk cup, incline the milk cup, increase the contact area of the milk and the air, adjust the contact depth of the nozzle and the milk and other experience and skills to prepare the milk foam with better quality, namely, the operator needs to obtain good foamed milk.

The second is to adopt a milk foam generating device which has a negative pressure chamber in the main body, then delivers cold milk and air into the negative pressure chamber, and at the same time sprays high temperature steam onto the surface of the milk mixed with air, thereby generating milk foam. Specifically, reference may be made to "a milk foam generator" of utility model patent No. CN201620991214.4 (publication No. CN206434194U) previously filed by the applicant.

However, in the milk foam generating device, the air inlet device and the milk outlet device are relatively fixed and form a whole, and on one hand, the size is large, so that the assembly and disassembly are troublesome; on the other hand, when the milk foam machine is cleaned, pollutants can enter the air inlet device to affect the air inlet function, so that the cleaning difficulty is high.

In addition, in the existing air inlet device, on one hand, the air inlet adjusting device is complex, the precision requirement is high, and the production reject ratio is high; on the other hand, the situation that signals cannot be monitored often occurs due to poor stability of the gear which is monitored by the cooperation of the magnet and the Hall sensor.

Disclosure of Invention

The invention aims to solve the first technical problem of providing a milk foam generating device for a coffee machine, which is convenient for loading, unloading and cleaning the milk foam machine, aiming at the current situation of the prior art.

A second technical problem to be solved by the present invention is to provide a milk foam generating device for a coffee machine with low manufacturing difficulty.

The third technical problem to be solved by the invention is to provide the milk foam generating device for the coffee machine, which is convenient for monitoring the gear.

The technical scheme adopted by the invention for solving the first technical problem is as follows: a milk foam generating device for a coffee machine, characterized in that: comprises that

The milk frother is provided with a negative pressure cavity, a steam socket, an air socket, a milk inlet channel and a milk outlet channel, and the steam socket, the air socket, an outlet of the milk inlet channel and an inlet of the milk outlet channel are communicated with the negative pressure cavity;

the steam inlet device is arranged on the coffee machine and is provided with a steam joint which can be inserted into the steam socket; and

and the air inlet device is arranged on the coffee machine and is provided with an air connector which can be inserted into the air insertion opening.

In order to further solve the second technical problem, the air inlet device comprises

The fixed support is internally provided with an air inlet channel, and the outlet of the air inlet channel is communicated with the air connector through an air conveying pipe;

the first air inlet piece is fixed relative to the fixed support, covers the inlet of the air inlet channel, and is provided with a first flow through hole at the eccentric position;

the rotating bracket can be rotatably arranged on the fixed bracket;

the second air inlet piece is fixed relative to the rotating support, a second flow through hole corresponding to the first flow through hole is formed in the eccentric position, and the second flow through hole is communicated with the external atmosphere; and

and the knob is arranged on the rotating bracket and used for driving the rotating bracket to rotate relative to the fixed bracket so as to enable the second through hole and the first through hole to be in a communicated or blocked state.

In order to prompt whether different states are adjusted in place or not, one end, facing the rotating support, of the fixed support is provided with a gear part, and the gear part is provided with a first gear groove, a second gear groove and a third gear groove at intervals along the circumferential direction;

the air inlet device also comprises an elastic gear part which is fixed relative to the rotating bracket, and a convex bulge part is arranged on the gear part and always has a tendency of abutting against the gear part;

when the convex part moves to the position of the gear position groove, the convex part can be inserted into the corresponding gear position groove under the action of elastic force.

In order to further solve the third technical problem, a first conducting strip, a second conducting strip and a third conducting strip are arranged on the fixed support, and at least part of the first conducting strip, part of the second conducting strip and part of the third conducting strip extend into the first gear groove, the second gear groove and the third gear groove respectively;

the milk foam generating device has at least three working states:

in a first working state, the convex part of the gear piece is inserted into the first gear groove and is electrically connected with the first conducting strip, the second through hole is communicated with the first through hole, and the milk inlet channel is communicated with milk raw materials;

in a second working state, the convex part of the gear piece is inserted into the second gear groove and is electrically connected with the second conducting strip, the second through hole and the first through hole are in a blocking state, and the milk inlet channel is communicated with milk raw materials;

in a third working state, the convex part of the gear piece is inserted in the third gear groove and is electrically connected with the third conducting strip, the second through hole and the first through hole are in a blocking state, and the milk inlet channel is not communicated with milk raw materials;

like this, circuit turn-on signal when can through different gears monitors the gear of locating, conveniently transmits the signal transmission of the gear of locating for coffee machine controller, realizes different mode automatically.

This gear monitoring is achieved on the premise that the air inlet device is integrated on the whole machine, because if the air inlet device is integrated on the milk maker, the air inlet device needs to be frequently separated from the coffee maker, which is inconvenient for electrical connection with the coffee maker.

In order to avoid the clamping of the convex parts in the gear grooves, the wall surface of each gear part between every two adjacent gear grooves is a convex cambered surface.

In order to prompt the user to adjust the gear, an indicating rod corresponding to the following convex part is convexly arranged on the peripheral wall of the knob and used for indicating the rotating position of the convex part.

In order to facilitate the installation of the first air inlet part and the second air inlet part, the fixed support is provided with a containing groove communicated with the air inlet channel, and the first air inlet part and the second air inlet part are both arranged in the containing groove.

In order to facilitate the assembly and disassembly of the first air inlet piece, a limiting groove is formed in the circumferential wall of the accommodating groove along the axial direction, the first air inlet piece is sheet-shaped, a limiting block is convexly arranged at the edge position of the first air inlet piece, and the limiting block is inserted into the limiting groove and can slide along the axial direction.

In order to prompt the user whether the milk foam machine is inserted in place, the coffee machine also comprises a reminding device arranged on the coffee machine, wherein the reminding device comprises a click pin and an elastic piece which can enable the head part of the click pin to always have the trend of moving towards the direction of a steam joint or an air joint;

the side part of the milk foam machine is provided with an outward-protruding inserting nozzle, the steam inserting opening and the air inserting opening are both arranged on the inserting nozzle, and the inserting nozzle is provided with a positioning groove for inserting the head part of the tick pin;

and under the condition that the inserting nozzle is inserted in place, the head part of the tick pin is inserted in the positioning groove.

In order to automatically control the on-off of the electric loop, the coffee maker also comprises a microswitch arranged on the coffee maker, and the microswitch is provided with a contact and an elastic sheet capable of extruding the contact;

the side part of the milk foaming machine is provided with a convex spigot, and the steam socket and the air socket are both arranged on the spigot;

when the plug-in nozzle is separated from the steam joint and the air joint, the elastic sheet releases the contact to disconnect the microswitch;

and when the plug nozzle is inserted in place, the elastic sheet pushes the contact under the stirring of the plug nozzle so as to close the microswitch.

Compared with the prior art, the invention has the advantages that: by integrating the steam inlet device and the air inlet device on the whole coffee machine, on one hand, the milk foam machine is reduced in size and convenient to assemble and disassemble; on the other hand, the milk foam machine is cleaned without polluting the steam inlet device and the air inlet device, so that the milk foam machine is convenient to clean.

Drawings

FIG. 1 is a schematic perspective view of a milk foam generator for a coffee maker according to an embodiment of the present invention in a state where the milk foam generator is inserted into place;

FIG. 2 is a schematic perspective view of the milk frother of FIG. 1 shown disengaged from the coffee maker;

FIG. 3 is a longitudinal cross-sectional view of FIG. 1;

FIG. 4 is an enlarged view of portion A of FIG. 3;

FIG. 5 is a schematic perspective exploded view in another direction of FIG. 1 (with parts of the milk frother omitted);

FIG. 6 is a longitudinal cross-sectional view of the intake air device of FIG. 1 in a first operating condition;

fig. 7 is a longitudinal sectional view of the intake apparatus of fig. 1 in a second operating state.

Detailed Description

The invention is described in further detail below with reference to the accompanying examples.

Fig. 1 to 7 show a preferred embodiment of a milk foam generating device for a coffee maker (not shown in the figures) according to the present invention. The milk foam generating device comprises a milk foam machine 1, an air inlet device 2, an air inlet device 3, a reminding device 4 and a microswitch 5.

Wherein, the milk frother 1 comprises a base 11, a top cover 12, a gas-liquid mixer 13, a milk inlet pipe 14 and a milk outlet pipe 15. Specifically, the base 11 has a milk containing chamber 110 with an open top inside; the top cover 12 covers the top opening of the base 11, and the interlayer 120 is arranged inside the top cover 12; the gas-liquid mixer 13 is arranged in the interlayer 120, the interior of the gas-liquid mixer is provided with a negative pressure cavity 101, a steam socket 102, an air socket 103, a milk inlet channel 104 and a milk outlet channel 105, the steam socket 102, the air socket 103, an outlet of the milk inlet channel 104 and an inlet of the milk outlet channel 105 are communicated with the negative pressure cavity 101, the gas-liquid mixer 13 is provided with a nozzle 131 exposed out of the side part of the top cover 12, and the steam socket 102 and the air socket 103 are both arranged on the nozzle 131; one end of the milk inlet pipe 14 is connected to the inlet of the milk inlet channel 104, and the other end of the milk inlet pipe passes through the bottom wall of the top cover 12 and extends into the milk containing cavity 110; one end of the milk outlet pipe 15 is connected to the outlet of the milk outlet passage 105, and the other end is exposed to the front side of the top cover 12. In this embodiment, the negative pressure cavity 101 and the steam inlet 102 form a complete chamber, and when the steam connector 21 is inserted into the chamber, the negative pressure cavity 101 is formed in the part of the chamber where the steam connector 21 is not inserted.

The steam inlet device 2 is installed on the coffee machine and comprises a steam connector 21, a steam transmission pipe 22 and a steam generator (not shown in the figure), wherein the steam connector 21 can be inserted into the steam insertion opening 102, the inlet end of the steam transmission pipe 22 is connected with the steam outlet of the steam generator, and the outlet end of the steam transmission pipe is connected with the steam connector 21.

The air inlet device 3 is arranged on the coffee machine and comprises an air connector 31, an air pipe 32, a fixed bracket 33, a first air inlet part 34, a rotating bracket 35, a second air inlet part 36, a knob 37, a gear part 38 and an annular sealing part 39.

Specifically, the air joint 31 can be inserted into the air insertion opening 103. In this embodiment, the steam connector 21 and the air connector 31 are a single piece.

The inlet end of the air pipe 32 is connected to the outlet of an air intake passage 332 described below, and the outlet end is connected to the air connector 31 described above.

The fixed bracket 33 is provided with a containing groove 331 and an air inlet passage 332 communicated with the containing groove 331, an inlet of the air inlet passage 332 is positioned on an end wall inside the containing groove 331, and a limit groove 3311 is axially arranged on a peripheral wall inside the containing groove 331; the end surface of the fixed bracket 33, which is provided with one end of the accommodating groove 331, is provided with a gear part 333, the gear part 333 is provided with a first gear groove 3331, a second gear groove 3332 and a third gear groove 3333 at intervals along the circumferential direction, the fixed bracket 33 is provided with a first conductive sheet 3334, a second conductive sheet 3335 and a third conductive sheet 3336, and at least part of the first conductive sheet 3334, the second conductive sheet 3335 and the third conductive sheet 3336 respectively extend into the first gear groove 3331, the second gear groove 3332 and the third gear groove 3333. In addition, the wall surface of the gear part 333 between two adjacent gear grooves is a convex arc surface.

The first air inlet member 34 is in the shape of a sheet, is disposed in the accommodating groove 331, and covers the inlet of the air inlet passage 332. A first flow through hole 341 is formed at the eccentric position of the first air inlet member 34; a limit block 342 is convexly arranged at the edge position of the first air inlet member 34, and the limit block 342 is inserted into the limit groove 3311 of the fixed bracket 33 and can slide along the axial direction, so that the first air inlet member 34 can be conveniently detached from the fixed bracket 33, and the relative fixation of the first air inlet member 34 and the fixed bracket 33 along the circumferential direction can be ensured.

The rotating bracket 35 is rotatably mounted on the fixed bracket 33 by a plurality of clamping feet 351 arranged along the circumferential direction, and the inserting part 352 is convexly arranged on the rotating bracket 35.

The second air inlet 36 is in a block shape, disposed in the accommodating groove 331, and abuts against the first air inlet 34. A second flow hole 361 corresponding to the first flow hole 341 axially penetrates through an eccentric position of the second air inlet member 36, and a slot 362 into which the insertion portion 352 is inserted is formed at one end of the second air inlet member 36 facing the rotating bracket 35, so as to realize relative fixation with the rotating bracket 35.

The knob 37 is mounted on the rotating bracket 35 for driving the rotating bracket 35 to rotate relative to the fixed bracket 33, so that the second through-hole 361 is in a communication state or a blocking state with the first through-hole 341. The knob 37 and the rotating bracket 35 are also fixed relatively by the matching of the inserting part and the slot, and the details are not described here. In this embodiment, an indication rod 371 corresponding to the protrusion 381 described below is protruded from the peripheral wall of the knob 37 to indicate the rotation position of the protrusion 381.

The gear part 38 has elasticity and is mounted on the rotating bracket 35, and the gear part 38 is provided with a convex part 381, and the convex part 381 always tends to be abutted against the gear part 333; in the gear shifting process, the arc surface of the gear part 333 extrudes the protruding part 381, and when the protruding part 381 moves to the position of the gear groove, the protruding part 381 can be inserted into the corresponding gear groove under the action of elastic force, and collides with the corresponding conducting strip to generate click sound to remind a user of the gear position to be adjusted in place.

The annular seal 39 is interposed between the end wall of the receiving groove 331 and the first air intake member 34, thereby preventing air from leaking through a gap between the end wall of the receiving groove 331 and the first air intake member 34.

The reminder device 4 includes a mounting base 41, a click pin 42 and an elastic member 43. Specifically, the mounting seat 41 is mounted on the coffee machine, at the side in front of the steam connector 21 and the air connector 31; the plug 131 is provided with a positioning groove 1311 for inserting the head of the click pin 42; the elastic member 43 is a spring, one end of which is connected to the mounting seat 41 and the other end of which is connected to the tail of the click pin 42, and enables the head of the click pin 42 to always have a tendency to move toward the steam connector 21 or the air connector 31.

The microswitch 5 is mounted on the coffee machine, is positioned at the lower part in front of the steam connector 21 and the air connector 31, and has a contact 51 and a spring piece 52 capable of pressing the contact 51.

In addition, the coffee machine is provided with a controller, a first detection circuit, a second detection circuit and a third detection circuit, and the controller is electrically connected with the micro switch 5, the first detection circuit, the second detection circuit and the third detection circuit. The gear piece 38 and the first conductive sheet 3334 are connected in series to the first detection circuit, the gear piece 38 and the second conductive sheet 3335 are connected in series to the second detection circuit, and the gear piece 38 and the third conductive sheet 3336 are connected in series to the third detection circuit.

When the nozzle 131 of the milk foaming machine 1 is separated from the steam connector 21 and the air connector 31, the elastic sheet 52 releases the contact 51, so that the microswitch 5 is switched off, and the electric circuit is switched off to ensure safety;

when the plug 131 of the milk foam machine 1 is inserted in place, the head of the click pin 42 is inserted in the positioning groove 1311, and the impact generates crisp click sound to prompt the plug to be in place; the elastic sheet 52 pushes the contact 51 under the shifting of the plug 131, so that the microswitch 5 is closed, the electric circuit is conducted, the milk foam generating device can normally work, and the milk foam generating device has at least three working states:

in the first working state, the protrusion 381 of the gear position member 38 is inserted into the first gear position groove 3331 and electrically connected to the first conductive sheet 3334, the second through hole 361 and the first through hole 341 are in a communication state, and the milk inlet passage 104 is communicated with the milk raw material;

in the second working state, the protrusion 381 of the gear component 38 is inserted into the second gear groove 3332 and electrically connected to the second conductive sheet 3335, the second flow hole 361 and the first flow hole 341 are in a blocking state, and the milk inlet passage 104 is communicated with the milk raw material;

in the third operating state, the protrusion 381 of the gear member 38 is inserted into the third gear groove 3333 and electrically connected to the third conductive sheet 3336, the second flow through hole 361 and the first flow through hole 341 are in a blocking state, and the milk inlet passage 104 is not communicated with the milk material.

The working principle of the embodiment is as follows:

(1) as shown in fig. 2, when the milk frother 1 is disconnected from the coffee machine, the steam connector 21 and the air connector 31 are disconnected, the spring piece 52 releases the contact 51 to disconnect the microswitch 5, and the electric circuit is disconnected to ensure safety;

(2) when the milk foam generating device needs to be started, only the steam socket 102 and the air socket 103 of the milk foam machine 1 need to be respectively inserted in alignment with the steam joint 21 and the air joint 31, in the process of inserting the nozzle 131, the head of the click pin 42 always abuts against the outer wall of the nozzle 131 until the positioning groove 1311 moves to the position of the click pin 42, the click pin 42 is inserted into the positioning groove 1311 under the elastic force of the elastic piece 43, and the impact generates a crisp click sound to prompt the milk foam to be inserted in place; meanwhile, the elastic sheet 52 pushes the contact 51 under the stirring of the plug 131, so that the microswitch 5 is closed, and the electric circuit is conducted, so that the milk foam generating device can work normally;

firstly, when coffee requiring milk foam such as cappuccino and the like needs to be made, the knob 37 is only required to be rotated to shift to the A position and milk is contained in the milk containing cavity 110, at the moment, the milk foam generating device is in a first working state, as shown in fig. 6, the convex part 381 of the shift piece 38 is inserted in the first shift groove 3331 and is electrically connected with the first conductive sheet 3334, so that the first detection loop is conducted and transmits signals to the controller of the coffee machine, and the second flow through hole 361 and the first flow through hole 341 are in a communicated state;

the coffee maker starts the steam generator to generate milk bubbles after coffee is led out, steam generated by the steam generator enters the negative pressure cavity 101 through the steam conveying pipe 22 and the steam connector 21 in sequence to form negative pressure, air can enter the air-liquid mixer 13 through the second flow hole 361, the first flow hole 341, the air inlet channel 332, the air conveying pipe 32 and the air connector 31 in sequence under the action of the negative pressure, is mixed with milk entering through the milk inlet channel 104 and then enters the negative pressure cavity 101, and is mixed with the steam to generate milk foam which is then discharged through the milk outlet channel 105 and the milk outlet pipe 15 in sequence;

when coffee without milk foam such as latte is required to be made, the knob 37 is only required to be rotated to shift to the B position and milk is contained in the milk containing cavity 110, at this time, the milk foam generating device is in the second working state, as shown in fig. 7, the protruding part 381 of the shift piece 38 is inserted in the second shift groove 3332 and is electrically connected with the second conductive sheet 3335, so that the second detection loop is conducted and transmits signals to the controller of the coffee machine, and the second flow hole 361 and the first flow hole 341 are in a blocking state;

the coffee maker starts the steam generator to lead out milk before coffee is led out, the steam generated by the steam generator enters the negative pressure cavity 101 through the steam conveying pipe 22 and the steam connector 21 to form negative pressure, under the action of the negative pressure, the milk can enter the negative pressure cavity 101 through the milk inlet pipe 14 and the milk inlet channel 104 in sequence, is mixed with the steam and then is discharged through the milk outlet channel 105 and the milk outlet pipe 15 in sequence;

thirdly, when the milk foam machine 1 needs to be cleaned, the knob 37 only needs to be rotated to shift to the C position and the milk is emptied at the milk containing cavity 110, at this time, the milk foam generating device is in the third working state, the convex part 381 of the shift piece 38 is inserted in the third shift groove 3333 and is electrically connected with the third conductive sheet 3336, so that the third detection loop is conducted and transmits a signal to the controller of the coffee machine, and the second flow through hole 361 and the first flow through hole 341 are in a blocking state;

the coffee maker directly starts the steam generator, water provided by the steam generator enters the negative pressure cavity 101 through the steam conveying pipe 22 and the steam joint 21 in sequence, and the inner cavity of the gas-liquid mixer 13 is fully cleaned.