Counterweight hydraulic system and crane

Abstract

The present invention relates to the field of construction machinery, and discloses a counterweight hydraulic system and a crane. The counterweight hydraulic system includes a first counterweight oil cylinder, a second counterweight oil cylinder, and a balance oil circuit. The balance oil circuit is respectively connected to the first rodless cavity oil circuit of the first counterweight oil cylinder and the second rodless cavity oil circuit of the second counterweight oil cylinder, and is used to communicate with the one of the first rodless cavity oil circuit and the second rodless cavity oil circuit with a lower oil pressure to drain oil. During the lifting process of the first counterweight oil cylinder and the second counterweight oil cylinder, the balance oil circuit can partially drain the hydraulic oil input to the counterweight oil cylinder with a smaller load, so that the oil inlet flow rates of the rodless cavities of the first counterweight oil cylinder and the second counterweight oil cylinder are consistent, effectively reducing the synchronous error caused by the compensation characteristics, and enabling the synchronous accuracy to meet the requirements.

Description

Technical Field

[0001] The present invention belongs to the field of construction machinery, and specifically, relates to a counterweight hydraulic system and a crane applying the counterweight hydraulic system. Background Art

[0002] In order to improve the lifting capacity, a crane is usually equipped with movable counterweights. During the hoisting operation of the crane, the movable counterweights are lifted and positioned synchronously by two counterweight cylinders. When the synchronous error of the two counterweight cylinders is too large, it will cause problems such as damage to the counterweight cylinders by scratching and the inability to unload the counterweights, thus affecting the hoisting safety. Therefore, there are relatively high requirements for the synchronous accuracy of the two counterweight cylinders.

[0003] In the existing crane counterweight hydraulic system, when there are differences in the weights of the movable counterweights, resulting in differences in the loads of the two counterweight cylinders, during the lifting process of the two counterweight cylinders, due to the compensation characteristics, the rodless chamber of the counterweight cylinder with a smaller load will obtain a larger oil inflow within the same time, that is, the rodless chamber of the counterweight cylinder with a smaller load obtains a larger oil inflow rate, and the lifting speed of the counterweight cylinder with a smaller load is relatively faster. Thus, there is a large synchronous error between the two counterweight cylinders, and the synchronous accuracy cannot meet the requirements. Summary of the Invention

[0004] Aiming at the above deficiencies or defects in the prior art, the present invention provides a counterweight hydraulic system and a crane applying the counterweight hydraulic system, aiming to solve the technical problem that in the existing crane counterweight hydraulic system, there is a large synchronous error caused by the compensation characteristics during the lifting process of the two counterweight cylinders, and the synchronous accuracy cannot meet the requirements.

[0005] To achieve the above object, the present invention provides a counterweight hydraulic system, including:

[0006] A first counterweight cylinder and a second counterweight cylinder;

[0007] A balance oil circuit, which is respectively connected to the first rodless chamber oil circuit of the first counterweight cylinder and the second rodless chamber oil circuit of the second counterweight cylinder, and is used to conduct and drain oil with the one of the first rodless chamber oil circuit and the second rodless chamber oil circuit with a lower oil pressure.

[0008] Optionally, the balance oil circuit includes:

[0009] A first oil drainage branch, connected to the first rodless chamber oil circuit;

[0010] A second oil drainage branch, connected to the second rodless chamber oil circuit; and

[0011] The reversing valve includes an oil drain port, a first working oil port, and a second working oil port. The first working oil port is communicated with the first oil drain branch, the second working oil port is communicated with the second oil drain branch, and the oil drain port can be selectively communicated with the one of the first working oil port and the second working oil port with a lower oil pressure.

[0012] Optionally, the reversing valve is a three-position three-way hydraulically controlled reversing valve. The reversing valve further includes a first hydraulic control end and a second hydraulic control end respectively communicated with the first working oil port and the second working oil port. When the oil pressure at the first hydraulic control end is higher than the oil pressure at the second hydraulic control end, the reversing valve switches to the first valve position, and the oil drain port is communicated with the second working oil port. When the oil pressures at the first hydraulic control end and the second hydraulic control end are the same, the reversing valve switches to the second valve position, and the oil drain port is not communicated with either the first working oil port or the second working oil port. When the oil pressure at the first hydraulic control end is lower than the oil pressure at the second hydraulic control end, the reversing valve switches to the third valve position, and the oil drain port is communicated with the first working oil port.

[0013] Optionally, an oil drain oil circuit is connected to the oil drain port, and a throttle valve is provided on the oil drain oil circuit.

[0014] Optionally, the counterweight hydraulic system further includes a flow dividing and collecting valve. The inlet and outlet ends of the first rodless chamber oil circuit of the first counterweight cylinder and the inlet and outlet ends of the second rodless chamber oil circuit of the second counterweight cylinder are respectively communicated with two flow dividing ports of the flow dividing and collecting valve, and the first rodless chamber oil circuit and the second rodless chamber oil circuit are also communicated with each other through a throttle orifice.

[0015] Optionally, the throttle orifice is formed on the flow dividing and collecting valve.

[0016] Optionally, a balance valve is provided between the first rod chamber oil circuit and the first rodless chamber oil circuit and between the second rod chamber oil circuit and the second rodless chamber oil circuit.

[0017] Optionally, a two-way hydraulic lock is provided between the first rod chamber oil circuit and the first rodless chamber oil circuit and between the second rod chamber oil circuit and the second rodless chamber oil circuit.

[0018] Optionally, an accumulator is connected to the rod chamber of each of the first counterweight cylinder and the second counterweight cylinder.

[0019] The present invention also provides a crane, which includes the above-mentioned counterweight hydraulic system.

[0020] In the counterweight hydraulic system of the present invention, a balance oil circuit is added between the first rod chamber oil circuit of the first counterweight oil cylinder and the second rod chamber oil circuit of the second counterweight oil cylinder. The balance oil circuit can be communicated with the one of the first rod chamber oil circuit and the second rod chamber oil circuit with a lower oil pressure to drain oil. With such a setting, during the lifting process of the first counterweight oil cylinder and the second counterweight oil cylinder, the balance oil circuit can discharge part of the hydraulic oil input to the counterweight oil cylinder with a smaller load, so that the oil inlet flow rates of the rod chambers of the first counterweight oil cylinder and the second counterweight oil cylinder are consistent, effectively reducing the synchronous error caused by the compensation characteristics and enabling the synchronous accuracy to meet the requirements.

[0021] Other features and advantages of the present invention will be described in detail in the subsequent specific implementation section. Brief Description of the Drawings

[0022] The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. They are used together with the following specific implementation to explain the present invention, but do not constitute a limitation to the present invention. In the drawings:

[0023] Figure 1 It is a schematic structural diagram of the counterweight hydraulic system in an embodiment of the present invention;

[0024] Figure 2 It is a schematic structural diagram of the counterweight hydraulic system in another embodiment of the present invention.

[0025] Description of the Reference Numerals:

[0026] 1 First counterweight oil cylinder 2 Second counterweight oil cylinder

[0027] 3 Hydraulic oil tank 4 Directional control valve

[0028] 5 Flow control valve 6 Balance valve

[0029] 7 Double-check valve 8 Flow divider-combiner valve

[0030] 9 Throttle orifice 10 Main valve

[0031] 11 Main pump

[0032] L1 First rod chamber oil circuit L2 Second rod chamber oil circuit

[0033] L3 First rodless chamber oil circuit L4 Second rodless chamber oil circuit

[0034] L5 First oil drain branch L6 Second oil drain branch

[0035] L7 Oil drain circuit

[0036] P1 Oil port of the flow divider-combiner valve Detailed Description of the Invention

[0037] The following will describe in detail the specific embodiments of the present invention with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for explaining and understanding the present invention, and are not used to limit the present invention.

[0038] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0039] In the present invention, unless otherwise stated, the orientation words such as "upper, lower, top, bottom" are generally used in the direction shown in the accompanying drawings or for the mutual positional relationship description of each component in the vertical, perpendicular or gravitational direction.

[0040] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0041] The present invention first provides a counterweight hydraulic system.

[0042] Refer to the attached Figure 1 and the attached Figure 2 As shown, in one embodiment, the counterweight hydraulic system includes a first counterweight oil cylinder 1, a second counterweight oil cylinder 2, and a balance oil circuit. The balance oil circuit is respectively connected to the first rodless cavity oil circuit L1 of the first counterweight oil cylinder 1 and the second rodless cavity oil circuit L2 of the second counterweight oil cylinder 2, and is used to communicate with the one with the lower oil pressure in the first rodless cavity oil circuit L1 and the second rodless cavity oil circuit L2 to drain oil.

[0043] It can be understood that by adding a balance oil circuit between the first rodless cavity oil circuit L1 of the first counterweight oil cylinder 1 and the second rodless cavity oil circuit L2 of the second counterweight oil cylinder 2, the balance oil circuit can communicate with the one with the lower oil pressure in the first rodless cavity oil circuit L1 and the second rodless cavity oil circuit L2 to drain oil. In this way, during the lifting process of the first counterweight oil cylinder 1 and the second counterweight oil cylinder 2, the first rodless cavity oil circuit L1 and the second rodless cavity oil circuit L2 respectively input hydraulic oil into the rodless cavities of the first counterweight oil cylinder 1 and the second counterweight oil cylinder 2. The balance oil circuit drains oil by communicating with the one with the lower oil pressure in the first rodless cavity oil circuit L1 and the second rodless cavity oil circuit L2, so as to be able to discharge part of the hydraulic oil input to the counterweight oil cylinder with a smaller load, thereby making the oil inlet flow rates of the rodless cavities of the first counterweight oil cylinder 1 and the second counterweight oil cylinder 2 consistent, effectively reducing the synchronous error caused by the compensation characteristics, and enabling the synchronous accuracy to meet the requirements.

[0044] For example, when the load of the first counterweight oil cylinder 1 is greater than that of the second counterweight oil cylinder 2, during the process of synchronously lifting the counterweight by the first counterweight oil cylinder 1 and the second counterweight oil cylinder 2, the oil pressure in the first rod chamber oil circuit L1 will be higher than the oil pressure in the second rod chamber oil circuit L2. This will cause the amount of hydraulic oil distributed to the second rod chamber oil circuit L2 to be greater than that of the first rod chamber oil circuit L1. At this time, the balance oil circuit is communicated with the second rod chamber oil circuit L2 to be able to discharge part of the hydraulic oil in the second rod chamber oil circuit L2. In this way, the flow rate of the hydraulic oil entering the rod chambers of the first counterweight oil cylinder 1 and the second counterweight oil cylinder 2 is made consistent, achieving high-precision synchronous lifting.

[0045] In one embodiment, referring to the attached Figure 1 and the attached Figure 2 As shown, the balance oil circuit includes a first oil discharge branch L5, a second oil discharge branch L6, and a reversing valve 4. The first oil discharge branch L5 is connected to the first rod chamber oil circuit L1, the second oil discharge branch L6 is connected to the second rod chamber oil circuit L2. The reversing valve 4 includes an oil discharge port, a first working oil port, and a second working oil port. The first working oil port is communicated with the first oil discharge branch L5, the second working oil port is communicated with the second oil discharge branch L6, and the oil discharge port can be selectively communicated with the one having a lower oil pressure among the first working oil port and the second working oil port.

[0046] It can be understood that the first oil discharge branch L5 and the second oil discharge branch L6 are respectively used to be communicated with the first rod chamber oil circuit L1 and the second oil discharge branch L6 to lead out the corresponding hydraulic oil, and the reversing valve 4 is used to judge the oil pressure magnitudes of the first rod chamber oil circuit L1 and the second rod chamber oil circuit L2 through the first oil discharge branch L5 and the second oil discharge branch L6, and then select to be communicated with the one having a lower oil pressure, so as to discharge part of the hydraulic oil in the first rod chamber oil circuit L1 or the second rod chamber oil circuit L2 through the oil discharge port.

[0047] In one embodiment, referring to the attached Figure 1 and the attached Figure 2 As shown, the reversing valve 4 is a three-position three-way hydraulic control reversing valve. The reversing valve 4 further includes a first hydraulic control end and a second hydraulic control end respectively corresponding to and communicated with the first working oil port and the second working oil port. When the oil pressure at the first hydraulic control end is higher than the oil pressure at the second hydraulic control end, the reversing valve 4 switches to the first valve position, and the oil discharge port is communicated with the second working oil port. When the oil pressure magnitudes at the first hydraulic control end and the second hydraulic control end are the same, the reversing valve 4 switches to the second valve position, and the oil discharge port is not communicated with the first working oil port and the second working oil port. When the oil pressure at the first hydraulic control end is lower than the oil pressure at the second hydraulic control end, the reversing valve 4 switches to the third valve position, and the oil discharge port is communicated with the first working oil port.

[0048] In this embodiment, specifically, pressure springs are respectively arranged at the first hydraulic control end and the second hydraulic control end of the reversing valve 4. The pressure difference between the first hydraulic control end and the second hydraulic control end overcomes the spring force of the pressure spring, thereby causing the spool of the reversing valve 4 to move towards the first hydraulic control end or the second hydraulic control end, so that the reversing valve 4 can be switched among the first valve position, the second valve position, and the third valve position. In practical applications, when it is found that the synchronization error between the first counterweight oil cylinder 1 and the second counterweight oil cylinder 2 is relatively large, by adjusting the spring force of the pressure spring, that is, increasing the opening degree of the spool of the reversing valve 4, the oil discharge flow rate of the balance oil circuit is further increased, and then the synchronization error is reduced, and the synchronization accuracy is improved to meet the requirements.

[0049] For example, when the load of the first counterweight oil cylinder 1 is greater than the load of the second counterweight oil cylinder 2, during the process of synchronously lifting the counterweight by the first counterweight oil cylinder 1 and the second counterweight oil cylinder 2, the oil pressure of the first rod chamber oil circuit L1 will be higher than the oil pressure of the second rod chamber oil circuit L2, making the oil pressure of the first working oil port higher than the oil pressure of the second working oil port, and then making the oil pressure of the first hydraulic control end higher than the oil pressure of the second hydraulic control end. At this time, the reversing valve 4 is switched to the first valve position, and the oil discharge port is connected to the second working oil port, so that the oil discharge port is communicated with the second rod chamber oil circuit L2. In this way, part of the hydraulic oil in the second rod chamber oil circuit L2 can flow through the second oil discharge branch L6, the second working oil port, and the reversing valve 4, and finally be discharged from the oil discharge port, ultimately achieving the purpose of making the hydraulic oil flow rates entering the rod chambers of the first counterweight oil cylinder 1 and the second counterweight oil cylinder 2 consistent and realizing high-precision synchronous lifting.

[0050] It can be understood that by setting the reversing valve 4 as a hydraulically controlled reversing valve, and the first hydraulic control end and the second hydraulic control end are respectively communicated with the first working oil port and the second working oil port, the reversing valve 4 can independently select to conduct oil discharge with the one with the lower oil pressure in the first rod chamber oil circuit L1 and the second rod chamber oil circuit L2, without manual control or additional induction elements and control elements, which simplifies the structure and operation.

[0051] In one embodiment, referring to the attached Figure 1 and the attached Figure 2 as shown, an oil discharge oil circuit L7 is connected to the oil discharge port, and a speed control valve 5 is arranged on the oil discharge oil circuit L7.

[0052] It can be understood that the speed control valve 5 can adjust the flow rate of the oil discharge oil circuit L7, and further adjust the oil discharge flow rate of the balance oil circuit.

[0053] In practical applications, when it is found that the synchronization error between the first counterweight oil cylinder 1 and the second counterweight oil cylinder 2 is relatively large, in addition to the above method of adjusting the spring force of the pressure spring, the speed control valve 5 can also be adjusted to increase the oil discharge flow rate of the balance oil circuit, and then reduce the synchronization error, and improve the synchronization accuracy to meet the requirements.

[0054] In this embodiment, the oil inlet end of the oil drain oil path L7 is connected to the oil drain port, and the oil outlet end is connected to the hydraulic oil tank 3 of the counterweight hydraulic system, so that the hydraulic oil discharged from the oil drain port flows back into the hydraulic oil tank 3 for reuse.

[0055] In one embodiment, referring to the attached Figure 1 and the attached Figure 2 As shown, the counterweight hydraulic system further includes a flow dividing and collecting valve 8. The oil inlet and outlet ends of the first rodless cavity oil path L3 of the first counterweight cylinder 1 and the oil inlet and outlet ends of the second rodless cavity oil path L4 of the second counterweight cylinder 2 are respectively communicated with two flow dividing ports of the flow dividing and collecting valve 8, and the first rodless cavity oil path L3 and the second rodless cavity oil path L4 are also connected through a throttle hole 9.

[0056] It can be understood that during the process of the first counterweight cylinder 1 and the second counterweight cylinder 2 unloading the counterweight, the hydraulic oil is respectively input into the rodless cavities of the first counterweight cylinder 1 and the second counterweight cylinder 2 through the flow dividing and collecting valve 8 to achieve the synchronous movement of the first counterweight cylinder 1 and the second counterweight cylinder 2. When there is a large flow dividing error in the flow dividing and collecting valve 8, the hydraulic oil in the one with a larger oil inflow volume in the first rodless cavity oil path L3 and the second rodless cavity oil path L4 can flow into the one with a smaller oil inflow volume through the throttle hole 9, thereby balancing the oil inflow of the first rodless cavity oil path L3 and the second rodless cavity oil path L4, so that the synchronous accuracy of the first counterweight cylinder 1 and the second counterweight cylinder 2 unloading the counterweight can meet the requirements. In short, the throttle hole 9 has the function of balancing the oil inflow of the first rodless cavity oil path L3 and the second rodless cavity oil path L4.

[0057] In one embodiment, the throttle hole 9 is formed on the flow dividing and collecting valve 8. In this way, the structure of the counterweight hydraulic system is effectively simplified and the structure is more compact.

[0058] In another embodiment, the throttle hole 9 is formed by a throttle valve provided on the connecting oil path between the first rodless cavity oil path L3 and the second rodless cavity oil path L4.

[0059] In one embodiment, referring to the attached Figure 1 As shown, balance valves 6 are provided between the first rod cavity oil path L1 and the first rodless cavity oil path L3 and between the second rod cavity oil path L2 and the second rodless cavity oil path L4.

[0060] It can be understood that the balance valve 6 can keep the first counterweight cylinder 1 and the second counterweight cylinder 2 in any position when there is no hydraulic oil input to the first counterweight cylinder 1 and the second counterweight cylinder 2.

[0061] In another embodiment, referring to the attached Figure 2As shown, a two-way hydraulic lock 7 is provided between the first rod chamber oil circuit L1 and the first rodless chamber oil circuit L3, and between the second rod chamber oil circuit L2 and the second rodless chamber oil circuit L4.

[0062] Understandably, the two-way hydraulic lock 7 can keep the first counterweight cylinder 1 and the second counterweight cylinder 2 in any position when there is no hydraulic oil input to the first counterweight cylinder 1 and the second counterweight cylinder 2.

[0063] In one embodiment, accumulators are connected to the rod chambers of the first counterweight cylinder 1 and the second counterweight cylinder 2 respectively.

[0064] Understandably, when the accumulator is used in combination with the balance valve 6 or the two-way hydraulic lock 7, the first counterweight cylinder 1 and the second counterweight cylinder 2 can be kept in any position without sinking for a long time.

[0065] In one embodiment, the counterweight hydraulic system further includes a main valve 10 and a main pump 11 connected to the oil outlet of the hydraulic oil tank 3. The main valve 10 is respectively connected to the first rod chamber oil circuit L1, the second rod chamber oil circuit L2, the oil port P1 of the flow dividing and collecting valve 8, the pressure oil circuit of the main pump 11, and the return oil circuit of the hydraulic oil tank 3, and is used to control the flow direction of the hydraulic oil input to the first counterweight cylinder 1 and the second counterweight cylinder 2, so as to realize the actions of lifting and unloading the counterweight of the first counterweight cylinder 1 and the second counterweight cylinder 2.

[0066] Furthermore, an overflow valve is connected to the pressure oil circuit of the main pump 11 and the return oil circuit of the hydraulic oil tank 3 to control the system pressure of the counterweight hydraulic system through the overflow valve, and to avoid damage to devices such as the accumulator due to excessive pressure.

[0067] The present invention also provides a crane, and the crane includes the crane counterweight hydraulic system as described above. For the specific structure of this crane counterweight hydraulic system, refer to the above embodiments. Since this crane adopts all the technical solutions of the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, and will not be elaborated here one by one.

[0068] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0069] In addition, it should be noted that, in the various specific technical features described in the above specific embodiments, they can be combined in any appropriate manner without conflict. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0070] In addition, any combination can be made among various different embodiments of the present invention, as long as it does not violate the idea of the present invention, and it should equally be regarded as the content disclosed by the present invention.

Claims

1. A counterweight hydraulic system, characterized in that, Comprising: A first counterweight oil cylinder (1) and a second counterweight oil cylinder (2); A balance oil circuit, which is respectively connected to a first rodless cavity oil circuit (L1) of the first counterweight oil cylinder (1) and a second rodless cavity oil circuit (L2) of the second counterweight oil cylinder (2), and is used to conduct and drain oil with the one having a lower oil pressure in the first rodless cavity oil circuit (L1) and the second rodless cavity oil circuit (L2); The balance oil circuit includes: A first oil drainage branch (L5), which is connected to the first rodless cavity oil circuit (L1); A second oil drainage branch (L6), which is connected to the second rodless cavity oil circuit (L2); and A directional control valve (4), including an oil drainage port, a first working oil port and a second working oil port. The first working oil port is communicated with the first oil drainage branch (L5), the second working oil port is communicated with the second oil drainage branch (L6), and the oil drainage port can be selectively communicated with the one having a lower oil pressure in the first working oil port and the second working oil port; Wherein, the directional control valve (4) is a three-position three-way hydraulic control directional control valve. The directional control valve (4) further includes a first hydraulic control end and a second hydraulic control end respectively communicated with the first working oil port and the second working oil port. When the oil pressure at the first hydraulic control end is higher than the oil pressure at the second hydraulic control end, the directional control valve (4) switches to the first valve position, and the oil drainage port is communicated with the second working oil port. When the oil pressures at the first hydraulic control end and the second hydraulic control end are the same, the directional control valve (4) switches to the second valve position, and the oil drainage port is not communicated with the first working oil port and the second working oil port. When the oil pressure at the first hydraulic control end is lower than the oil pressure at the second hydraulic control end, the directional control valve (4) switches to the third valve position, and the oil drainage port is communicated with the first working oil port.

2. The counterweight hydraulic system according to claim 1, characterized in that, The oil drainage port is connected with an oil drainage oil circuit (L7), and a speed control valve (5) is arranged on the oil drainage oil circuit (L7).

3. The counterweight hydraulic system according to claim 1, characterized in that, The counterweight hydraulic system further includes a flow dividing and collecting valve (8). The inlet and outlet ends of a first rodless cavity oil circuit (L3) of the first counterweight oil cylinder (1) and the inlet and outlet ends of a second rodless cavity oil circuit (L4) of the second counterweight oil cylinder (2) are respectively communicated with two flow dividing ports of the flow dividing and collecting valve (8), and the first rodless cavity oil circuit (L3) and the second rodless cavity oil circuit (L4) are also communicated with each other through a throttle hole (9).

4. The counterweight hydraulic system according to claim 3, characterized in that, The throttle hole (9) is formed on the flow dividing and collecting valve (8).

5. The counterweight hydraulic system according to claim 3, characterized in that, Balance valves (6) are arranged between the first rodless cavity oil circuit (L1) and the first rodless cavity oil circuit (L3) and between the second rodless cavity oil circuit (L2) and the second rodless cavity oil circuit (L4).

6. The counterweight hydraulic system according to claim 3, characterized in that, Double-check valves (7) are arranged between the first rodless cavity oil circuit (L1) and the first rodless cavity oil circuit (L3) and between the second rodless cavity oil circuit (L2) and the second rodless cavity oil circuit (L4).

7. The counterweight hydraulic system according to claim 5 or 6, characterized in that, Accumulators are connected to the rodless cavities of the first counterweight oil cylinder (1) and the second counterweight oil cylinder (2) respectively.

8. A crane, characterized in that, The crane includes the counterweight hydraulic system according to any one of claims 1 to 7.

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