A limit device for a beverage brewing unit

Abstract

The present invention relates to a limiting device for a beverage brewing unit, including a limiting member and a base for mounting the limiting member. The limiting member is a rigid cam, and the base for mounting the rigid cam is a cam base. The cam base is provided with a limiting post, and the rigid cam is coaxially mounted on the limiting post of the cam base. The rigid cam is used to cooperate with a blocking member on the lower piston of the beverage brewing unit to achieve blocking of the lower piston and / or relative movement between the lower piston and the brewing cylinder of the beverage brewing unit. The two ends of the rigid cam are provided with stop surfaces, namely an upper stop surface and a lower stop surface; and the rigid cam is rotatably and fixedly mounted on the cam base; when the rigid cam and the cam base are combined, some appropriate gaps are designed to ensure that the limiting member has a certain degree of freedom, so that during the operation of the limiting member and the blocking member, the position of each friction can be adaptively changed, which can significantly improve the service life of the limiting member without increasing costs and the number of parts.

Description

Technical Field

[0001] The present invention relates to the field of beverage preparation, and particularly to a limiting device for a beverage preparation unit Background Art

[0002] Modern beverage production equipment includes tea beverage extraction equipment, coffee extraction equipment, etc. Taking coffee extraction equipment as an example, in some existing coffee extraction devices, i.e., brewing devices, a limiting device installed on its frame and a blocking member installed in the inner cavity of the lower piston are matched to temporarily block the movement of the brewing lower piston, so that the lower piston and the brewing cylinder move relatively, and the lower piston ejects coffee residues from the brewing chamber, i.e., top slag, discharge slag, and reset the lower piston and the brewing cylinder to the position for adding coffee powder, i.e., reset, to complete the entire process of brewing coffee. The limiting device generally includes a limiting member and a limiting member base. The limiting member on the frame of the coffee brewing device and the blocking member in the inner cavity of the lower piston will generate friction during the movement process, and wear will invariably occur during the friction process. The wear resistance of the limiting member affects the use reliability. And because the limiting member is generally fixed on the limiting member base, this leads to wear at the same position of the limiting member every time (as shown in Figure 5 ), which will cause accelerated wear of the limiting member. These wears will undoubtedly greatly reduce the service life of the limiting member, unless these materials are highly wear-resistant materials, but the price of highly wear-resistant materials is often expensive.

[0003] Based on the above problems, it is necessary to develop a new combination method of the limiting device and the blocking member on the lower piston to greatly improve the service life of the limiting member without increasing the cost and the number of parts. Summary of the Invention

[0004] The purpose of the present invention is to provide an optimized combination method of a limiting device for the existing technology with the above problems, change the operating state of the limiting member in the limiting device and the blocking member in the inner cavity of the lower piston, and improve the service life of the limiting member.

[0005] To achieve the above purpose, the technical solution provided by the present invention is as follows:

[0006] A limiting device for a beverage brewing unit, including a limiting member and a base for installing the limiting member, characterized in that the limiting member is a rigid cam, the base for installing the rigid cam is a cam base, the cam base is provided with a limiting column, and the rigid cam is coaxially installed on the limiting column of the cam base. The rigid cam is used to cooperate with the blocking member on the lower piston of the beverage brewing unit to achieve lower piston blocking and / or relative movement between the lower piston and the brewing cylinder of the beverage brewing unit. Here, the limiting member is in the form of a rigid cam, and the rigid cam is an element that does not undergo elastic or flexible compression, with high wear resistance and working reliability; preferably, the rigid cam is made of stainless steel material.

[0007] The rigid cam includes an upper surface and a lower surface at both ends thereof, and a cam body located between the upper surface and the lower surface. The outer surface of the cam body is a cylindrical surface.

[0008] The described rigid cam has two forms according to different heights. The first form of the rigid cam is that the height of the rigid cam is high enough, that is, when the brewing cylinder and the lower piston carry the blocking member to move to the lowest point, they still do not reach the lower surface of the rigid cam. That is, the lower surface here does not play a blocking role, that is, it does not play the role of a stopping surface. The second form of the rigid cam is that the height of the rigid cam is small. The brewing cylinder and the lower piston carry the blocking member to first reach the lower surface of the rigid cam and then continue to move to reach the lowest point. That is, both the upper and lower surfaces of the rigid cam play the role of a stopping surface. At this time, the rigid cam can be considered to have two stopping surfaces, that is, the upper surface of the rigid cam is the upper stopping surface, and the lower surface is the lower stopping surface. The maximum outer diameter of the stopping surface is the maximum outer diameter of the rigid cam.

[0009] The working process will be specifically described below in combination with the slag reset process of the beverage machine top. When the beverage is extracted, during the first movement process in which the brewing cylinder carries the lower piston downward together, the lower piston carries the blocking member downward together. At this time, the moving speeds of the brewing cylinder, the lower piston, and the blocking member are equal. When the blocking member touches the limiting member, that is, the upper surface of the rigid cam, that is, the upper stopping surface, the second movement starts. At this time, the moving speeds of the lower piston and the blocking member decrease or completely stop due to being blocked by the rigid cam, but the brewing cylinder still continues to move downward, and relative movement occurs between the lower piston and the brewing cylinder. When the brewing cylinder moves relative to the lower piston to the upper limit position of their relative positions, that is, when the upper end surface of the lower piston is basically flush with the upper end surface of the brewing cylinder, under the continuous drive of the beverage brewing drive unit, the brewing cylinder and the lower piston push downward together so that the blocking member is compressed radially toward the end close to the inner wall of the lower piston, realizing that the brewing cylinder and the lower piston can break through the obstruction of the rigid cam and continue to move downward together in the third movement. Of course, since the blocking member will rub against the rigid cam during the third movement process, the resistance received at this time is greater than the resistance received during the first movement process. During the third movement process in which the brewing cylinder and the lower piston move together, the slag discharging component completes the discharge of the beverage residue located on the upper surface of the lower piston.

[0010] For the first type of rigid cam form, during the third movement of the brewing cylinder together with the lower piston until after reaching the lowest point, the blocking member is compressed radially towards the end close to the inner wall of the lower piston. At this time, the brewing cylinder, the lower piston, and the blocking member have reached the lowest point and are in a stationary state, and there is friction between the blocking member and the rigid cam. When the brewing cylinder starts to move upward under the drive of the drive unit, the fourth movement occurs. At this time, the movement speed of the lower piston increases slowly or remains completely stopped due to being blocked by the rigid cam, but the brewing cylinder still continues to move upward relatively quickly, resulting in relative movement between the lower piston and the brewing cylinder. For the second type of rigid cam form, the brewing cylinder and the lower piston undergo the third movement through the rigid cam until reaching the lower surface of the rigid cam, that is, below the lower stop surface. At this time, the blocking member returns to its original state due to being released from the blocking of the rigid cam, and the brewing cylinder, the lower piston, and the blocking member move to the lowest point in this state and are in a stationary state. When the brewing cylinder starts to move upward, the fourth movement occurs when the blocking member contacts the limiting member, that is, the lower surface of the rigid cam, that is, the lower stop surface. At this time, the movement speed of the lower piston decreases or stops completely due to being blocked by the rigid cam, but the brewing cylinder still continues to move upward, resulting in relative movement between the lower piston and the brewing cylinder. Regardless of which of the above rigid cam forms, when the brewing cylinder moves relative to the lower piston to the lower limit position of their relative position, that is, when the volume of the brewing cylinder is the largest, this is generally the position for filling the powder. For the first type of rigid cam form, after filling is completed, then under the drive of the beverage brewing drive unit, the brewing cylinder drives the lower piston and the blocking member to overcome the obstruction of the rigid cam and can continue to move upward together during the fifth movement. For the second type of rigid cam form, after filling is completed, then under the drive of the beverage brewing drive unit, the brewing cylinder and the lower piston are pushed upward together, causing the blocking member to be compressed radially towards the end close to the inner wall of the lower piston, enabling the brewing cylinder and the lower piston to break through the obstruction of the rigid cam and can continue to move upward together during the fifth movement. During the fifth movement of the brewing cylinder driving the lower piston and the blocking member, the three pass through the rigid cam until they are separated from the rigid cam. When the blocking member is separated from the rigid cam, the blocking member returns to its original position, and the brewing cylinder drives the lower piston and the blocking member to move upward together with the upper piston to form a brewing chamber to complete coffee extraction; after the extraction of the beverage is completed, the next cycle is carried out, and the brewing cylinder carries the lower piston and moves downward together during the first movement.

[0011] Preferably, the upper and lower surfaces of the rigid cam are the upper stop surface and the lower stop surface respectively. It enables the blocking member to switch back and forth at a set position when moving downward and upward with the lower piston. The structure is reliable and has strong controllability. When used on the brewer of a fully automatic beverage machine, it can realize the functions of slag pushing and resetting of the lower piston.

[0012] To improve the wear resistance of the rigid cam, further, the rigid cam is rotatably and fixedly mounted on the cam base. When the lower piston of the beverage brewing unit contacts the rigid cam, the rigid cam can rotate relative to the cam base. When the rigid cam is assembled with the cam base, it has a certain degree of freedom in the X-axis, Y-axis, and Z-axis directions, enabling the rigid cam to axially displace a certain distance and freely rotate with a slightly externally applied torque. In this way, when the rigid cam contacts the stopper on the lower piston, the rigid cam will rotate within a small range under the action of a certain tangential force. Although the rotation angle is very small, this will change the position of the friction, which is equivalent to the friction position being different each time, thereby significantly increasing the service life of the stopper without increasing costs or the number of parts.

[0013] Preferably, the rigid cam is the limiting cam in the above second form. Between the upper surface (i.e., the upper stop surface) and the lower surface (i.e., the lower stop surface) of the rigid cam is the cam body. The outer surface of the cam body is a cylindrical surface, and preferably, a part of the cylindrical surface is a concave smooth curved surface. The curved surface part of the cam body reduces the friction when the stopper passes through the cam body, reducing the energy consumption and component wear when the stopper passes through the cam body.

[0014] Preferably, the upper stop surface and the lower stop surface are conical surfaces; the advantage of this setting is that the conical surfaces are in transitional fit with the stopper, which can reduce wear, and the driving force for the lower piston to pass through the stop surface can be changed by changing the angle of the conical surface.

[0015] Further, it includes a fixing element, and the rigid cam is mounted on the cam base through the fixing element.

[0016] Preferably, the limiting post is provided with a stopper positioning step surface, a fixing element mounting hole, and a fixing element positioning surface; the lower end surface of the rigid cam coincides with the rigid cam positioning step surface on the limiting post. The fixing element is inserted and assembled into the cam base from the fixing element mounting hole, and the disk head end surface of the fixing element is assembled together with the fixing element positioning surface at the upper end of the limiting post in a coincident manner; there is a space between the disk head end surface of the fixing element and the rigid cam positioning step surface of the limiting post, and the rigid cam is installed in this space.

[0017] Preferably, a radial gap is provided between the inner hole surface of the rigid cam and the outer peripheral surface of the limiting post of the cam base, and an axial gap is provided between the upper end surface of the rigid cam and the disk head end surface of the fixing element; the radial gap and the axial gap enable the rigid cam to rotate when it contacts the stopper.

[0018] Preferably, the fixing element is a bolt and a nut. The fixing bolt is inserted and assembled into the limiting post from the fixing element mounting hole, and the fixing nut is fixed to the threaded end of the fixing bolt by means of threaded assembly. The fixing element can also be selected as a screw, and the screw is threadedly connected to the limiting post.

[0019] Beneficial effects

[0020] (1) When combining the rigid cam and the limit post of the cam base, design some appropriate clearances to ensure that the rigid cam has a certain degree of freedom. In this way, during the operation of the rigid cam and the stopper, the position of each friction can be adaptively changed. Since the same position is not frictionally contacted during each operation, wear marks 22e as shown in Figure 5 will not be left on the rigid cam, thereby significantly increasing the service life of the rigid cam without increasing costs or the number of parts.

[0021] (2) The limiting member is in the form of a rigid cam, and the cam body part is a concave smooth curved surface. The curved surface part reduces the friction when the stopper passes through the cam body, reducing the energy consumption and component wear when the stopper passes through the cam body. Description of the drawings

[0022] Figure 1 is an axonometric view of the limiting device of the present invention;

[0023] Figure 2 is a partial enlarged cross-sectional view of the limiting device;

[0024] Figure 3 is an assembled view and an exploded view of the stop elastic component used in conjunction with the limiting device;

[0025] Figure 4 is an assembly schematic diagram of the brewing cylinder and the lower piston;

[0026] Figure 5 is a schematic diagram of the problems existing in the existing products on the market;

[0027] Figure 6 is a schematic diagram of the radial displacement of the steel ball of the stop elastic component against the rigid cam;

[0028] Figure 7 is an assembled axonometric schematic diagram of the coffee machine brewing device;

[0029] Figure 8 is a sectional view of the filling position of the coffee machine brewing device;

[0030] Figure 9 is a sectional view of the brewing cylinder moving upward and the upper piston forming a coffee brewing chamber;

[0031] Figure 10 is a sectional view of the lower piston in the slag top position;

[0032] Figure 11 is a sectional view of the lower piston passing through the upper stop surface;

[0033] Figure 12It is a sectional view at the lowermost end where the brewing cylinder runs to the brewing device;

[0034] Figure 13 It is a schematic sectional view of a brewing device where multiple steel balls do not contact the rigid cam simultaneously;

[0035] Figure 14 It is Figure 13 an enlarged view of part A in Specific Embodiments

[0036] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be described in detail below through preferred embodiments in conjunction with the accompanying drawings.

[0037] In the following embodiments, the limiting device adopts the form of a rigid cam, and the rigid cam is the second form of the rigid cam mentioned in the invention content; the blocking member is described as a stop elastic component. However, the blocking member is not limited to the form of this embodiment and can also be a blocking member in the form of a compressible protrusion in existing beverage brewing equipment.

[0038] As can be seen from the drawings, as Figure 1 、 2As shown, the limiting device 2 includes a cam base 21, a rigid cam 22, a fixing bolt 23 and a fixing nut 24, and a limiting post 25. Among them, the rigid cam 22 is coaxially installed on the limiting post 25 of the cam base 21. In this embodiment, the limiting post 25 and the cam base 21 are of an integral structure, and the two can also be assembled. The rigid cam 22 is provided with a conical upper stop surface 22a and a lower stop surface 22b, and an inner hole AH. Between the upper stop surface 22a and the lower stop surface 22b is a cam body 22c. The outer surface of the cam body 22c is a cylindrical surface, and part of the cylindrical surface is a concave curved surface. The curved surface part reduces the friction when the blocking member passes through the cam body, reducing the energy consumption and component wear when the blocking member passes through the cam body. The cam base 21 is provided with a limiting post 25. The limiting post 25 is provided with a cylinder AC, a cam positioning surface DF, a bolt positioning surface CF, a nut positioning surface EF and a bolt mounting hole 21H; the rigid cam 22 is coaxially installed along the axis R on the cylinder AC of the limiting post 25. The lower end surface BF of the rigid cam 22 coincides with the upper end surface DF on the limiting post 25. The fixing bolt 23 is inserted and assembled into the limiting post 25 from the bolt mounting hole 21H. The disk head end surface FF of the fixing bolt 23 is assembled together with the bolt positioning surface CF on the limiting post 25. The fixing nut 24 is fixed to the threaded end of the fixing bolt 23 by means of threaded assembly. The fixing nut 24 is installed coincidentally with the nut positioning surface EF on the limiting post 25 to fix the fixing bolt 23 to the limiting post 25. There is a space between the disk head surface FF of the fixing bolt 23 and the cam positioning surface DF on the limiting post 25. The rigid cam 22 is installed in this space. There is a gap 61 between the disk head end surface FF of the fixing bolt 23 and the upper end surface AF of the rigid cam 22. There is a gap 62 between the inner hole of the rigid cam 22 and the cylinder AC of the limiting post 25. The rigid cam 22 is installed in the said space by virtue of its gravity. With these set gaps, the friction between the rigid cam 22 and the limiting post 25 and the fixing bolt 23 is minimized to the greatest extent, so that the rigid cam 22 can rotate around the axis R when subjected to a tangential force. Of course, here, in order to enable the rigid cam 22 to rotate around the axis R, a bearing can also be installed between the rigid cam 22 and the limiting post 25 to reduce the friction so that the rigid cam 22 can rotate around the axis R when subjected to a tangential force. And the present invention uses the gap between the components themselves to reduce the friction between the rigid cam and the limiting post, with a simple structure and reduced cost.

[0039] As Figures 7 to 12As shown, the brewing device 4 of the coffee machine includes an upper piston 44 held in a frame 45. A brewing cylinder 43 is coaxially mounted with the upper piston 44 and can reciprocate axially relative to the upper piston 44. A lower piston 41 is installed in a cylindrical hole of the brewing cylinder 43 and can also reciprocate axially with the brewing cylinder 43. The relative movement between the lower piston 41 and the brewing cylinder 43 is provided with upper and lower limit positions. A thread 43a is provided on the brewing cylinder 43. A driving screw 47 is rotatably fixed in the frame 45. A thread 47a is provided on the driving screw 47, and this thread 47a meshes with the thread 43a on the brewing cylinder 43. Bushings 46 are provided at both ends of the driving screw 47, and the bushings 46 are rigidly held in the frame 45. The driving screw 47 can be rotated clockwise and counterclockwise by an applied drive. During the clockwise or counterclockwise rotation of the driving screw 47, the brewing cylinder 43 is driven to move axially upward or downward. A limiting device 2 is rigidly held at the lower end of the frame 45. A rigid cam 22 is on the same axis as the brewing cylinder 43. A stop elastic component 1 is coaxially fixed to the lower piston 41 by a base 42, as Figure 3 shown, the stop elastic component 1 is composed of an elastic base 11, an elastic clamp 12, and steel balls 13. Among them, three steel balls 13 are radially movably installed in holes of the elastic base 11, and the elastic clamp 12 fixes the steel balls 13 in the holes from the outside. The elastic clamp has elasticity, and the steel balls 13 can elastically displace outward when subjected to a thrust force; the elastic clamp makes the 3 steel balls abut against the inner end of the radial hole accommodating them from the outside and partially protrude from the inner cylindrical hole of the elastic base; as Figure 8 shown, the brewing device 4 is in the loading position (details of loading coffee powder are not shown). At this time, the lower piston 41 is at the lower end of the brewing cylinder 43, and the stop elastic component 1 is at the lower end of the lower stop surface 22b of the rigid cam 22, and the steel balls 13 are in tangential contact with the lower stop surface 22b.

[0040] As Figure 9 shown, when the driving screw 47 rotates clockwise, it drives the brewing cylinder 43 to move upward. The lower piston 41 is at the lower end of the brewing cylinder 43 and is driven to move upward together with the brewing cylinder 43, that is, the fifth movement described in the invention content occurs. At this time, the stop elastic component 1 located at the lower end of the lower piston 41 will pass through the rigid cam 22. During this process, first, the steel balls 13 on the stop elastic component 1 will radially displace outward under the elastic action of the elastic clamp 12, and then move while rubbing against the outer surface of the rigid cam 22. The brewing cylinder drives the lower piston to continue to move axially upward. The stop elastic component 1 disengages from the rigid cam 22 and continues to move upward. The upper piston 44 is inserted into the brewing cylinder 43 to form a brewing chamber 48. At this time, the brewing cylinder stops moving, and the brewing device is in the position of brewing coffee (the process of making coffee is not shown).

[0041] As Figure 10As shown, the driving screw 47 rotates counterclockwise, driving the brewing cylinder 43 to move downward axially. At this time, the lower piston 41 moves downward together with the brewing cylinder 43. As described above, the lower piston 41 and the brewing cylinder 43 can move axially reciprocally and are provided with relative upper and lower limit positions. At this time, the lower piston 41 is exactly at the lower end of the brewing cylinder 43, that is, the lower piston is at the lower limit position of the relative movement position with the brewing cylinder. At this time, the first movement described in the invention content occurs. When the steel ball 13 on the stop elastic component 1 contacts the upper stop surface 22a of the rigid cam 22, due to the uneven force of the clamp on the three steel balls, the contact time of the steel balls with the upper stop surface of the rigid cam is out of sync (as Figure 13 , 14 shown), so that the center of the circle formed by the points where multiple steel balls contact or are about to contact the upper stop surface of the rigid cam is inconsistent with the vertical axis of the rigid cam, resulting in a tangential force of the steel balls on the rigid cam. Since a gap is set between the rigid cam and the limit post during assembly, the frictional force between the rigid cam and the limit post is small, and the rigid cam can rotate a small range along the axis R. Immediately afterwards, the lower piston 41 is blocked and stops moving downward, and the brewing cylinder 43 continues to move downward, that is, the second movement described in the invention content occurs. Combining Figure 4 shown, until the upper limit surface 41b of the lower piston 41 coincides with the bottom end surface 43c of the brewing cylinder 43. At this time, the lower piston 41 is at the uppermost limit position of the brewing cylinder 43, that is, the upper limit position, and the slag removal function is completed.

[0042] As Figure 11 , Figure 6 shown, the brewing cylinder continues to move downward. At this time, the lower piston 41 and the brewing cylinder 43 move simultaneously, that is, the third movement described in the invention content occurs. The steel ball 13 on the stop elastic component 1 radially pushes the elastic clamp 12 outward along the assembly hole and makes a tangential frictional movement with the rigid cam 22 until the steel ball 13 of the stop elastic component 1 moves to the lower end of the lower stop surface 22b of the rigid cam 22. As described above, because the rigid cam 22 rotates a small range when contacting the steel ball 13, this frictional movement is not at the same position as the previous operation.

[0043] As Figure 12As shown, the brewing cylinder 43 has run to the lowermost end of the brewing device 4. The steel ball 13 returns to its initial position under the elastic action of the elastic clamp 12. The driving screw 47 rotates clockwise again, driving the axial upward movement of the brewing cylinder 43. The steel ball 13 also moves upward together. At this time, the steel ball 13 contacts the lower stop surface 22b of the rigid cam 22 and gives a thrust F to the rigid cam 22. Under the action of this thrust F, the rigid cam 22 rotates along the axis R again, and once again changes the friction position when the rigid cam 22 makes a tangential friction movement with the blocking member. The lower stop surface 22b blocks the steel ball 13 and restricts the lower piston 41 from moving upward together with the brewing cylinder 43. The lower piston 41 is at the upper end of the brewing cylinder 43 and there is a displacement space with a certain distance from the brewing cylinder 43. When the brewing cylinder 43 moves upward axially, the lower piston 41 remains stationary. When the brewing cylinder 43 continues to move upward, the fourth movement described in the invention content occurs. Combined with Figure 4 、 Figure 8 As shown, until the lower limit surface 41a of the lower piston coincides with the step surface 43b inside the brewing cylinder, at this time, the lower piston 41 is located at the lowermost limit position of the brewing cylinder 43, that is, the lower limit position, and the brewing cylinder stops running. At this time, the brewing device completes a process of brewing coffee and returns to the loading position, that is, resets. Then, the above fifth movement, first, second, third, and fourth movements are cycled; because when the limiting column of the rigid cam and the cam base are combined, some appropriate gaps are designed to ensure that the rigid cam has a certain degree of freedom. In this way, during the operation of the rigid cam and the blocking member, the friction position can be adaptively changed each time, thereby significantly improving the service life of the rigid cam without increasing the cost or the number of parts.

[0044] The present invention is not limited to the above embodiments. Based on the technical solutions disclosed in the present invention, those skilled in the art can make some substitutions, deformations or combinations of some technical features without creative labor according to the disclosed technical content, and these substitutions, deformations or combinations are all within the protection scope of the present invention.

Claims

1. A limiting device for a beverage brewing unit, comprising a limiting member and a base for mounting the limiting member, characterized in that: The limiting member is a rigid cam, and the base for mounting the rigid cam is a cam base. The cam base is provided with a limiting post, and the rigid cam is coaxially and rotatably mounted on the limiting post of the cam base. The rigid cam is used to cooperate with a blocking member on the lower piston of the beverage brewing unit to achieve blocking of the lower piston and / or relative movement between the lower piston and the brewing cylinder of the beverage brewing unit; driven by the blocking member on the lower piston, the rigid cam can rotate relative to the limiting post of the cam base; the blocking member is composed of an elastic base, an elastic clamp and steel balls. Among them, three steel balls are radially movably mounted in the holes of the elastic base, and the elastic clamp fixes the steel balls in the holes from the outside.

2. The limit device according to claim 1, characterized in that: The two ends of the rigid cam are provided with stop surfaces, namely an upper stop surface and a lower stop surface respectively.

3. The limit device according to claim 2, characterized in that: Between the upper stop surface and the lower stop surface on the rigid cam is a cam body, and the outer surface of the cam body is a cylindrical surface, and part of the cylindrical surface is a concave smooth surface.

4. The limiting device according to claim 2, characterized in that: The upper stop surface and the lower stop surface are conical surfaces.

5. The limit device according to claim 1, characterized in that: It includes a fixing element, and the rigid cam is mounted on the limiting post of the cam base through the fixing element.

6. The limit device according to claim 5, characterized in that: The limiting post is provided with a rigid cam positioning step surface, a fixing element mounting hole and a fixing element positioning surface. The lower end surface of the rigid cam coincides with the rigid cam positioning step surface on the limiting post. The fixing element is inserted and assembled onto the cam base from the fixing element mounting hole, and the disk head end surface of the fixing element is assembled together with the fixing element positioning surface at the upper end of the limiting post in coincidence.

7. The limiting device according to claim 6, characterized in that: There is a space between the disk head end surface of the fixing element and the rigid cam positioning step surface of the limiting post, and the rigid cam is installed in this space.

8. The limit device according to claim 6, wherein: A radial gap is provided between the inner hole surface of the rigid cam and the outer peripheral surface of the limiting post of the cam base, and an axial gap is provided between the upper end surface of the rigid cam and the disk head end surface of the fixing element.

9. The limit device according to claim 1, wherein: The rigid cam is coaxially mounted on the limiting post of the cam base, and a gap is provided between the rigid cam and the limiting post of the cam base to ensure that during the contact between the rigid cam and the blocking member on the piston of the beverage brewing unit, the rigid cam can adaptively rotate relative to the limiting post of the cam base.

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