GB2610292A

GB2610292A - Water circuit switch device and instant electric water heater

Info

Publication number: GB2610292A
Application number: GB2210059.8A
Authority: GB
Inventors: Li Yong; Liu Jianfang; Chen Changchun
Original assignee: Zhangzhou Perkins Kitchen And Bathroom Electric Appliances Co Ltd
Current assignee: Zhangzhou Perkins Kitchen And Bathroom Electric Appliances Co Ltd
Priority date: 2021-07-08
Filing date: 2022-07-08
Publication date: 2023-03-01
Also published as: GB202210059D0; CN113339993A

Abstract

A water circuit switch device including a valve body 1 with a cylindrical through hole, the through hole lined with a sleeve 2 fixed in an axial position and rotatable in a circumferential direction. An inner wall of the through hole has a plurality of water passing holes (12, fig. 5) in the circumferential direction. The outer surface of the sleeve is provided with an aperture (21, fig. 7) which may selectively connect one of the passing holes to a bore of the pipe sleeve and connect to an external pipeline 3. The sleeve bore may comprise a filter sleeve (6, fig. 8). Also disclosed is an instant electric water heater (fig. 9) adopting the water circuit switch device.

Description

WATER CIRCUIT SWITCH DEVICE AND INSTANT ELECTRIC WATER

HEATER

FIELD OF TECHNOLOGY

100011 The present invention relates to the technical field of manufacturing of electric water heaters, in particular to a water circuit switch device and an instant electric water heater.

BACKGROUND

100021 In the installation of instant electric water heaters, a water inlet direction is often perpendicular to a direction of the water inlet pipe of the electric water heater, and the position of the external water inlet pipe will be different, which requires water inlet parts of the electric water heater to be connected to the external water inlet pipes in different directions. In order to meet this technical requirement, the installation of the water inlet pipeline of the instant electric water heater is complicated, and multiple gate valves are needed, which not only complicates the structure, but also inconveniences the installation.

SUMMARY

[0003] The technical problem to be solved by the present invention is to provide a water circuit switch device, which has a simple structure, can achieve water circuit connection in different directions, and simplifies water circuit installation.

[0004] To achieve the above purpose, the technical solution of the present invention is: a water circuit switch device including a valve body with a cylindrical through hole disposed thereon, the cylindrical through hole of the valve body is sleeved with a cylindrical pipe sleeve, the cylindrical pipe sleeve being fixed in an axial position and rotatable in a circumferential direction, an inner wall of the cylindrical through hole of the valve body is provided with a plurality of water passing holes in the circumferential direction, the valve body is connected to a pipeline through each of the water passing holes; and an outer peripheral surface of the cylindrical pipe sleeve is embedded with a first sealing ring at a peripheral position corresponding to each of the water passing holes, the outer peripheral surface of the pipe sleeve at a middle position of at least one of the first sealing ring is provided with a water crossing hole, when the pipe sleeve is rotated, the water crossing hole selectively connects one of the water passing holes to a bore of the pipe sleeve, the pipe sleeve is connected to an external pipeline through the bore. Whilst the first sealing ring is specified, it will be appreciated that in some instances this may be omitted if so desired, or other sealing means considered.

[0005] In other words, the valve body has two holes for connection with first and second pipes. The two holes preferably oppose each other. The valve body has a bore for connection with a third pipe. The valve body is preferably configured so that the third pipe would extend perpendicularly or substantially perpendicularly to a direction of the first and second pipes. One of the preferably opposing holes can be blocked and one can be left open so that water from one of the first and second pipes can be communicated with a third pipe and not communicated with the other of the first and second pipes. Preferably the blocking or opening of the two holes is achieved by a sleeve which has a hole to allow water into the bore from one of the first and second pipes, and a wall to block the other of the first and second pipes.

[0006] Furthermore, the bore of the pipe sleeve is further equipped with a filter sleeve, a plurality of filter through holes are distributed on an outer peripheral surface of the filter sleeve, and the water crossing hole is connected to the bore of the pipe sleeve through the filter through holes. In this way, larger particles can be prevented from passing through and blockage of the pipeline can be avoided. Whilst described as filter sleeve, it will be appreciated that non-sleeve configurations may be considered, and therefore there may be generally a filter for filtering water which is to enter the bore.

[0007] Furthermore, one end of the filter sleeve is closed, an outer peripheral surface of the closed end of the filter sleeve is screwed with an inner peripheral surface of the pipe sleeve through a screw thread, the outer peripheral surface of the closed end of the filter sleeve is further sleeved with a second sealing ring, and the second sealing ring is in contact with the inner peripheral surface of the pipe sleeve. This is convenient to disassemble the filter sleeve and facilitate regular cleaning. However other methods of connection of the filter may be considered, including push-fit or integral formation.

[0008] Furthermore, the outer peripheral surface of the pipe sleeve is provided with a ring of shoulder and a toggle protrusion, and one end of the shoulder abuts against one end of the valve body. It is convenient to rotate the pipe sleeve and switch the water circuit by toggling the protrusion.

[0009] Furthermore, the toggle protrusion is further provided with a fixed through hole By fixing the toggle protrusion or plucking convex with screws through the fixing through hole, the pipe sleeve is prevented from shifting and the water circuit is ensured to be smooth in operation However, other methods of fixing may be considered such as clamping [0010] The water circuit switch device of the present invention can achieve the connection and disconnection between the axial water circuit and the radial water circuit of the pipe sleeve by rotating the pipe sleeve through the coordination of a valve body and the pipe sleeve, and the radial water circuit of the pipe sleeve can achieve the connection in multiple directions. In this way, the overall structure is simple, which not only achieves water circuit connection in different directions, but also simplifies water circuit installation.

[0011] The present invention also provides a technical solution that: an instant electric water heater including an inner container equipped with an electric heating pipe, a water inlet pipe and a water outlet pipe connected to the inner container, a control circuit board for controlling an operation of the electric heating pipe and a power terminal block, the instant electric water heater further includes a water circuit switch device preferably in accordance with the aforementioned technical solution, and the water inlet pipe is connected to the bore of the pipe sleeve. Whilst the container is described as an "inner" container, it will be appreciated that the term "inner" may be omitted.

[0012] Furthermore, a water inlet end of the water inlet pipe is sleeved with one end of the pipe sleeve, and a third sealing ring is disposed between the outer peripheral surface of the one end of the pipe sleeve and an inner peripheral surface of the water inlet end of the water inlet pipe, and the other end of the pipe sleeve is closed or sealed by a sealing piece It will be appreciated that the third sealing ring may be omitted and/or alternative sealing means may be considered.

[0013] Furthermore, the water inlet pipe is provided with a pressure maintaining valve and/or a flow valve, and/or the water outlet pipe is provided with an on-off valve.

[0014] Preferably, the pressure maintaining valve comprises a generally stepped cylinder and a barrel, the stepped cylinder is provided with a water inlet hole on an end face of a big end and a water outlet hole on a peripheral surface of a small end, the water inlet hole is connected to the water outlet hole, a portion of the small end of the stepped cylinder is plugged into the barrel, a plurality of flanges extend outward from one end of the barrel away from the stepped cylinder, the barrel is clamped in the bore of the water inlet pipe through the plurality of flanges, the stepped cylinder is further sleeved in the bore of the water inlet pipe, the small end of the stepped cylinder is further equipped with a compression spring between the small end of the stepped cylinder and the barrel, and the small end of the stepped cylinder and the barrel is movable relative to each other to change a size of a water outlet cross-sectional area of the water outlet hole; and a fourth sealing ring is disposed between the outer peripheral surface of the small end of the stepped cylinder and an inner peripheral surface of the barrel; an exhaust hole is disposed on an outer peripheral surface of the large end of the stepped cylinder, the exhaust hole is connected to a space between an end face of the small end of the stepped cylinder and the barrel, the outer peripheral surface of the large end of the stepped cylinder on either side of the exhaust hole and the inner peripheral surface of the water inlet pipe are provided with a fifth sealing ring, and an outer wall of the water inlet pipe is further provided with an exhaust channel, the exhaust channel is connected to the exhaust hole. The pressure maintaining valve has a simple structure, requires no external power regulation and is less expensive.

[0015] Whilst the aforementioned features of the pressure maintaining valve are described, it will be appreciated that some may be omitted. The pressure maintaining valve functions via an inner tube (the cylinder) being received within and biased relative to an outer tube, which preferably has a closed end (the barrel). At least one, preferably radially directed, hole in the inner tube allows water to flow from the inner tube to the outer tube. When the water pressure is high, a biasing force of a biasing means is overcome and therefore the inner tube is received further inside the outer tube, closing more of at least one hole and thereby reducing the flow and so water pressure. When the water pressure is low, the biasing force is not overcome and so more of the at least one hole is exposed increasing the flow and so water pressure. As such, at least any one of the features of the stepped shape and small and big ends of the cylinder, the flanges, the sealing ring, and the exhaust hole, may be omitted. It will be appreciated that such a design of pressure maintaining valve may be used in other scenarios and systems, and/or may be provided in isolation [0016] Furthermore, the power terminal block comprises an insulating base provided with three parallel mounting through holes, each of the mounting through holes is provided with a conducting bar, and both ends of the conducting bar are connected to external wires, the insulating base is further provided with three connecting through holes, each of the connecting through holes is connected to one of the mounting through holes, and one end of each connecting wire is electrically connected with a middle part of the conducting bar through one of the connecting through holes. This kind of power terminal block can be connected with external power supply in left and right directions When the water heater is replaced, it is convenient for the installation and connection of the external power line, and avoids the installation difficulty caused by the insufficient length of the original line. Whilst three mounting through holes and three connecting through holes are described, it will be appreciated that other numbers may be considered.

[0017] The instant electric water heater of the present invention adopts the water circuit switch device, the water inlet pipe can be connected to the bore of the pipe sleeve, that is, the water inlet pipe can be connected to the axial water circuit of the pipe sleeve, and then connected to different water circuits in the radial direction of the pipe sleeve by rotating the pipe sleeve. Therefore, it is beneficial for the instant electric water heater to connect to external pipelines in different directions, which greatly facilitates the installation of the instant electric water heater.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG 1 is a front view of a water circuit switch device of the present invention; [0019] FIG 2 is an A-A sectional view of FIG. 1; [0020] FIG 3 is a bottom view of FIG. 1; [0021] FIG 4 is a B-B sectional view of FIG. 3; [0022] FIG 5 is a perspective view of a valve body of the water circuit switch device of the present invention integrated with two pipes; [0023] FIG. 6 is another perspective view of the valve body of the water circuit switch device of the present invention integrated with two pipes; [0024] FIG. 7 is a perspective view of a pipe sleeve of the water circuit switch device of the present invention [0025] FIG. 8 is a perspective view of a filter sleeve of the water circuit switch device of the present invention; [0026] FIG. 9 is a perspective view of an instant electric water heater of the present invention; [0027] FIG. 10 is a perspective view of a hidden casing, a control circuit board and a power terminal block of the instant electric water heater of the present invention; [0028] FIG. 11 is a front view of the hidden case, the control circuit board and the power terminal block of the instant electric water heater of the present invention; [0029] FIG. 12 is a C-C sectional view of FIG. 11; [0030] FIG. 13 is an enlarged view at a part D of FIG. 12; [0031] FIG. 14 is a perspective view of a barrel in a pressure maintaining valve of the present invention; [0032] FIG. 15 is a perspective view of a stepped cylinder n the pressure maintaining valve of the present invention; [0033] FIG. 16 is an E-direction view of FIG. 15; [0034] FIG. 17 is an F-F sectional view of FIG. 16; [0035] FIG. 18 is a perspective view of a power terminal block of the present invention; [0036] FIG. 19 is a perspective view of hiding an insulating base of FIG. 18; and [0037] FIG. 20 is a perspective view of the insulating base in a power terminal block of the present invention.

DESCRIPTION OF THE EMBODIMENTS

[0038] The present invention will be further explained in conjunction with the drawings and the specific of embodiments.

[0039] As shown in FIGS. 1 to 8, there is provided a water circuit switch device, which includes a valve body 1 with a cylindrical through hole 11 disposed thereon. The cylindrical through hole 11 of the valve body 1 is sleeved with a cylindrical pipe sleeve 2, and the cylindrical pipe sleeve 2 is fixed in an axial position and rotatable in a circumferential direction. Although described as cylindrical, it will be appreciated that alternative geometries of through holes and pipe sleeves may be considered. An inner wall of the cylindrical through hole 11 of the valve body 1 is provided with two water passing or water through holes 12 in the circumferential direction. The water passing or water through holes may otherwise be referred to as valve holes or opening. The valve body 1 is connected to a pipeline 3 through each of the water passing holes 12. In this embodiment, the valve body 1 is integrated with two pipelines 3.

[00401 An outer peripheral surface of the cylindrical pipe sleeve 2 is embedded with a first sealing ring 4 at a peripheral position corresponding to each of the water passing holes 12. Whilst described as a sealing ring, it will be appreciated that the geometry of the seal may not necessarily be circular, and that other forms of sealing means may be considered. The outer peripheral surface of the pipe sleeve 2 at a middle position of one of the first sealing rings 4 is provided with a water crossing or water passage hole 21. A mounting slot 22 for the first sealing ring 4 is disposed on the outer peripheral surface of the pipe sleeve 2 around the water crossing hole 21. A further mounting slot 22 for the first sealing ring 4 is also disposed on the outer peripheral surface of the pipe sleeve 2 on a side opposite to this mounting slot 22. When the pipe sleeve 2 is rotated, the water crossing hole 21 can selectively connect one of the water passing holes 12 to a bore of the pipe sleeve. The pipe sleeve 2 is connected to an external pipeline 5 through the bore.

[0041] The bore of the pipe sleeve 2 is further equipped with a filter 6, in particular a filter sleeve 6. A plurality of filter through holes 61 are distributed on an outer peripheral surface of the filter sleeve 6. The water crossing hole 21 is connected to the bore of the pipe sleeve 2 through the filter through holes 61.

[0042] One end of the filter sleeve 6 is closed, an outer peripheral surface of the closed end of the filter sleeve 6 is screwed with an inner peripheral surface of the pipe sleeve 2 through a screw thread, the outer peripheral surface of the closed end of the filter sleeve 6 is further sleeved with a second sealing ring 62, and the second sealing ring 62 is in contact with the inner peripheral surface of the pipe sleeve 2. Whilst a screwed connection is described, it will be appreciated that non-screw connections between the filter sleeve and the pipe sleeve 2 may be considered.

[0043] The outer peripheral surface of the pipe sleeve 2 is provided with a ring of shoulder 23 and a toggle protrusion 24, and one end of the shoulder 23 abuts against one end of the valve body 1. The toggle protrusion 24 is further provided with a fixed through hole 241. After the rotational position of the pipe sleeve 2 is adjusted, the toggle protrusion 24 can be fixed by a bolt passing through the fixing through hole 2412 so that the pipe sleeve 2 will not rotate any more to ensure that the water circuit channel is stable and clear. Whilst a bolt through a fixing hole is preferred, it will be appreciated that other securing means for securing the rotational position of the pipe sleeve may be considered, such as clamps. It will be appreciated that the shoulder and toggle protrusion may be omitted if so desired.

[0044] By rotating the pipe sleeve 2, the water circuit switch device of the embodiment can conveniently switch the connection or disconnection between the axial water circuit of the pipe sleeve 2 and two different water circuits in the radial direction of the pipe sleeve 2, which features a simple structure and convenient operation. As can be further seen from FIG. 4, water can be input through the pipeline 3 on one side of the valve body 1, then enter the bore of the pipe sleeve 2 through the water crossing hole 21 on the outer peripheral surface of the pipe sleeve 2 and a plurality of filter through holes 61 distributed on the outer peripheral surface of the filter sleeve 6, and then axially output from the pipe sleeve 2. At this time, if the pipe sleeve 2 is rotated by 180 degrees, the bore of the pipe sleeve 2 can be connected to the pipeline 3 on the other side of the valve body 1.

[0045] By combining FIGS. 1 to 8, which illustrate the water circuit switch device, and FIGS. 9 to 20, there is provided an instant electric water heater. The instant electric water heater includes an inner container or tank 10, a water inlet pipe 20, a water outlet pipe 30, a control circuit board 40 and a power terminal block 50. The inner container 10 is equipped with an electric heating pipe 101, the water inlet pipe 20 and the water outlet pipe 30 are both connected to the inner container 10, the control circuit board 40 controls an operation of the electric heating pipe 101. The instant electric water heater further includes a water circuit switch device 60 illustrated in the above example. The water inlet pipe 20 is connected to the bore of the pipe sleeve 2 along the axial direction of the pipe sleeve 2.

100461 In particular, a water inlet end of the water inlet pipe 20 is sleeved with one end of the pipe sleeve 2, and a third sealing ring 201 is disposed between the outer peripheral surface of the one end of the pipe sleeve 2 and an inner peripheral surface of the water inlet end of the water inlet pipe 20; and the other end of the pipe sleeve 2 is closed or sealed by the above filter sleeve 6 and one second sealing ring 62.

100471 The water inlet pipe 20 is preferably provided with a pressure maintaining or pressure regulating valve 70 and/or a flow valve 80, and the water outlet pipe 30 is preferably provided with an on-off valve 90. The flow valve 80 is rotated by, preferably, a stepper motor 801 to adjust the flow rate into the inner container 10 to ensure that the water output from the water outlet pipe 30 is kept in a relatively constant temperature state.

[0048] The pressure maintaining valve 70 preferably includes a generally or substantially stepped cylinder 701 and a barrel 702. The stepped cylinder 701 is provided with a water inlet hole 7011 on an end face of a big or larger end and a water outlet hole 7012 on a peripheral surface of a small or smaller end. The water inlet hole 7011 is connected to the water outlet hole 7012. A portion of the small end of the stepped cylinder 701 is plugged into the barrel 702. Preferably, four flanges 7021 extend outward from one end of the barrel 702 away from the stepped cylinder 701. However, it will be appreciated that the flanges may be omitted or other numbers of a flanges, such as at least one flange or a plurality of flanges may be considered. The barrel 702 is clamped in the bore of the water inlet pipe 20 through the four flanges 7021. The stepped cylinder 701 is further sleeved in the bore of the water inlet pipe 20. The small end of the stepped cylinder 701 is further equipped with a compression spring 703 between the small end of the stepped cylinder 701 and the barrel 702. The small end of the stepped cylinder 701 and the barrel 702 move relative to each other to change a size of a water outlet cross-sectional area of the water outlet hole 7012. Whilst a small and large end is described, it will be appreciated that this size discrepancy may not necessarily be the case or may be reversed.

[0049] A fourth sealing ring 704 is disposed between the outer peripheral surface of the small end of the stepped cylinder 701 and an inner peripheral surface of the barrel 702. Preferably, an exhaust hole 7013 is disposed on an outer peripheral surface of the large end of the stepped cylinder 701. The exhaust hole 7013 is connected to a space between an end face of the small end of the stepped cylinder 701 and the barrel 702. The outer peripheral surface of the large end of the stepped cylinder 701 on either side of the exhaust hole 7013 and the inner peripheral surface of the water inlet pipe 20 are provided with a fifth sealing ring 705. An outer wall of the water inlet pipe 20 is further provided with an exhaust channel 202. The exhaust channel 202 is connected to the exhaust hole 7013. The working process of this regulator valve 70 is: when water entering the water inlet 7011 has a large pressure, the water pressure drives the stepped cylinder 701 to overcome the elastic force of the compression spring 703, so that the small end of the stepped cylinder 701 moves inward more into the barrel 702, so that the water outlet cross-sectional area of the water outlet 7012 becomes smaller, the water outlet flow rate decreases, and the pressure of water entering the water inlet pipe 2 becomes smaller. When the water entering the water inlet hole 7011 has a small pressure, the elastic force of the compression spring 703 drives the small end of the stepped cylinder 701 to move outward, so that the water outlet cross-sectional area of the outlet hole 7012 becomes larger, the water outlet flow rate increases, and the pressure of water entering the inlet pipe 2 becomes larger. By this adjustment, the pressure of the water in the inlet pipe 2 can be ensured to be relatively stable, and the pressure of water entering the inner container 10 can be ensured to be relatively stable.

[00501 The power terminal block 50 preferably includes an insulating base 501. The insulating base 501 is provided with three parallel mounting through holes 5011. However, it will be appreciated that other numbers of mounting through holes may be considered. Each of the mounting through holes 5011 is provided with a conducting bar 502. Both ends of the conducting bar 502 may be connected to external wires. The insulating base 501 is further provided with three connecting through holes 5012, although other numbers of connecting through holes may be considered. Each of the connecting through holes 5012 is connected to one of the mounting through holes 5011, and one end of each connecting wire 503 is electrically connected with a middle part of the conducting bar 502 through one of the connecting through holes 5012. This kind of power terminal block 50 can be wired in left and right directions, so that on the one hand, it is convenient to install wires, and on the other hand, it can prevent the length of external power supply wires from being insufficient when replacing water heaters. The specific wire connection mode of this embodiment is as follows: a neutral line introduced from the power terminal block 50 is connected to one end of the electric heating pipe 101, one end of a thermostat 103 is connected to a live wire introduced from the power terminal block 50, the other end of the thermostat 103 is electrically connected to the control circuit board 40, and the other end of the electric heating pipe 101 is electrically connected to the control circuit board 40, so that the control circuit board 40 can control the power supply of the electric heating pipe 101 to be on and off, so as to control the operation of the electric heating pipe 101. However, it will be appreciated that other wiring arrangements may be considered.

[0051] In the instant electric water heater of this embodiment, an electromagnetic gate valve 203 is also disposed on the water inlet pipe 2 to conveniently control the on-off of the inlet water. In the instant electric water heater of this embodiment, each component is installed on a housing 102. After the pipe sleeve 2 is adjusted in position, its toggle protrusion 24 is fixed on the housing 102 by screws, although other securing means may be considered.

[0052] As the pipe sleeve 2 is rotated, the connection direction of the water inlet pipeline can be changed, so the installation of the instant electric water heater is very convenient.

[0053] Although the present invention has been particularly shown and described in connection with preferred embodiments, it will be apparent to those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims, fall within the scope of protection of the present invention.

Claims

CLAIMS1 A water circuit switch device comprising a valve body with a cylindrical through hole disposed thereon, wherein: the cylindrical through hole of the valve body is sleeved with a cylindrical pipe sleeve, the cylindrical pipe sleeve being fixed in an axial position and rotatable in a circumferential direction, an inner wall of the cylindrical through hole of the valve body is provided with a plurality of water passing holes in the circumferential direction, and the valve body is for connecting to a pipeline through each of the water passing holes; and an outer peripheral surface of the cylindrical pipe sleeve is embedded with a first sealing ring at a peripheral position corresponding to each of the water passing holes, the outer peripheral surface of the pipe sleeve at a middle position of at least one of the first sealing rings is provided with a water crossing hole, when the pipe sleeve is rotated, the water crossing hole is configured to selectively connect one of the water passing holes to a bore of the pipe sleeve, the pipe sleeve is for connecting to an external pipeline through the bore.
2. A water circuit switch device according to claim 1, wherein: the bore of the pipe sleeve is further equipped with a filter sleeve, a plurality of filter through holes are distributed on an outer peripheral surface of the filter sleeve, and the water crossing hole is connected to the bore of the pipe sleeve through the filter through holes.
3. A water circuit switch device according to claim 1, wherein: one end of the filter sleeve is closed, an outer peripheral surface of the closed end of the filter sleeve is screwed with an inner peripheral surface of the pipe sleeve through a screw thread, the outer peripheral surface of the closed end of the filter sleeve is further sleeved with a second sealing ring, and the second sealing ring is in contact with the inner peripheral surface of the pipe sleeve.
4. A water circuit switch device according to any one of claims 1 to 3, wherein: the outer peripheral surface of the pipe sleeve is provided with a ring of shoulder and a toggle protrusion, and one end of the shoulder abuts against one end of the valve body.
5. A water circuit switch device according to claim 4, wherein: the toggle protrusion is further provided with a fixed through hole.
6. An instant electric water heater comprising an inner container equipped with an electric heating pipe, a water inlet pipe and a water outlet pipe both connected to the inner container, a control circuit board for controlling an operation of the electric heating pipe and a power terminal block, wherein: the instant electric water heater further comprises a water circuit switch device according to any one of claims 1 to 5, and the water inlet pipe is connected to the bore of the pipe sleeve.
7. An instant electric water heater according to claim 6, wherein: a water inlet end of the water inlet pipe is sleeved with one end of the pipe sleeve, and a third sealing ring is disposed between the outer peripheral surface of the one end of the pipe sleeve and an inner peripheral surface of the water inlet end of the water inlet pipe; and the other end of the pipe sleeve is closed or sealed by a sealing piece.
8. An instant electric water heater according to claim 6, wherein: the water inlet pipe is provided with a pressure maintaining valve and a flow valve, and the water outlet pipe is provided with an on-off valve.
9. An instant electric water heater according to claim 8, wherein: the pressure maintaining valve comprises a stepped cylinder and a barrel, the stepped cylinder is provided with a water inlet hole on an end face of a big end and a water outlet hole on a peripheral surface of a small end, the water inlet hole is connected to the water outlet hole, a portion of the small end of the stepped cylinder is plugged into the barrel, a plurality of flanges extend outward from one end of the barrel away from the stepped cylinder, the barrel is clamped in the bore of the water inlet pipe through the plurality of flanges, the stepped cylinder is further sleeved in the bore of the water inlet pipe, the small end of the stepped cylinder is further equipped with a compression spring between the small end of the stepped cylinder and the barrel, and the small end of the stepped cylinder and the barrel is movable relative to each other to change a size of a water outlet cross-sectional area of the water outlet hole; and a fourth sealing ring is disposed between the outer peripheral surface of the small end of the stepped cylinder and an inner peripheral surface of the barrel; an exhaust hole is disposed on an outer peripheral surface of the large end of the stepped cylinder, the exhaust hole is connected to a space between an end face of the small end of the stepped cylinder and the barrel, the outer peripheral surface of the large end of the stepped cylinder on either side of the exhaust hole and the inner peripheral surface of the water inlet pipe are provided with a fifth sealing ring, and an outer wall of the water inlet pipe is further provided with an exhaust channel, the exhaust channel is connected to the exhaust hole.
10. An instant electric water heater according to any one of claims 7 to 9,wherein: the power terminal block comprises an insulating base provided with three parallel mounting through holes, each of the mounting through holes is provided with a conducting bar, and two ends of the conducting bar are connected to external wires, the insulating base is further provided with three connecting through holes, each of the connecting through holes is connected to one of the mounting through holes, and one end of each connecting wire is electrically connected with a middle part of the conducting bar through one of the connecting through holes.