CLIAMS:We Claim:
1. A method of operating a refrigerant recovery and recharge device (10) comprising the following steps:
- determining the specific pulse width for recharging oil from said refrigerant recovery and recharge device (10) to a refrigeration equipment (12); and
- determining the number of pulses of constant specific pulse width for recharging oil from said refrigerant recovery and recharge device (10) to a refrigeration equipment (12); and
- recharging oil from said refrigerant recovery and recharge device (10) to said refrigeration equipment (12) in dependence of the determined specific pulse width and number of pulses.

2. The method as claimed in claim 1, while determining specific pulse width, minimum and maximum pulse width for recharging a defined quantity of oil from said refrigerant recovery and recharge device (10) to said refrigeration equipment (12) is determined.
3. The method as claimed in claim 1, while determining specific pulse width, minimum and maximum size of the refrigeration equipment (12) is determined.
4. The method as claimed in claim 1, while determining specific pulse width, a power factor in dependence of said determined minimum and maximum pulse width and said determined minimum and maximum size of refrigeration equipment (12) is calculated.
5. The method as claimed in claim 1, while determining specific pulse width, a constant in dependence of a combination of minimum pulse width and minimum size of refrigeration equipment or maximum pulse width and maximum size of said refrigeration equipment (12).
6. The method as claimed in claim 1, calculating specific pulse width for recharging oil in dependence of size of the refrigeration equipment (12), said calculated power factor and said calculated constant for a quantity of oil to be recharged to said refrigeration equipment. ,TagSPECI:F O R M 2

THE PATENTS ACT, 1970
(39 of 1970)
COMPLETE SPECIFICATION
(See section 10; rule 13)

1. Title of the invention:

A METHOD OF OPERATING A REFRIGERANT RECOVERY AND RECHARGE DEVICE

2. Applicants:
a. Name: Robert Bosch GmbH
Nationality: A GERMAN Company
Address: Stuttgart, Feuerbach, Germany

b. Name: Bosch Limited
Nationality: An INDIAN Company
Address: Post Box No 3000, Hosur Road, Adugodi, Bangalore – 560 030, Karnataka, INDIA

Complete specification:
The following specification particularly describes the invention and the manner in which it is to be performed.

Field of the invention
[001] This invention relates to a method of operating a refrigerant recovery and recharge device.

Background of the invention
[002] Refrigerant recovery and recharge devices are well known in the state of the art. These devices are connected to a variety of refrigeration equipments for recovering used refrigerant and refilling pure refrigerant. While being connected to the refrigeration equipment the refrigerant recovery and recharge device performs three main functions viz., refrigerant recovery, vacuuming and refrigerant recharge.

[003] For the purposes of this invention we will focus on the refrigerant recharge process. In the vacuuming process which is done before the refrigerant recharge, the refrigeration equipment is evacuated in a manner such that a pressure difference exists between the refrigeration equipment and the refrigerant recovery and recharge device. The pressure in the refrigeration equipment is lower than the pressure in the refrigerant recovery and recharge device. Now when the refrigerant recharge process is started the refrigerant flows from the refrigerant recovery and recharge device to the refrigeration equipment due to the pressure difference.

[004] During the refrigerant recovery process liquids other than the refrigerant are recovered and which are recharged to the refrigeration equipment. During the refrigerant recovery process along with the refrigerant, oil is also recovered. During the refrigerant recharge process along with the refrigerant, oil and UV dye is recharged. This is important because based on the oil recovered an equivalent amount has to be recharged to the refrigeration equipment. The refrigerant recovery and recharge device can be operated in a fully automatic mode or manual mode. In the fully automatic mode the operator requires to key in the recovery and recharge parameters and the entire process of recovery, vacuuming and recharge is carried out step by step without intervention of the operator. In the manual mode the operator can select one or more processes out of recovery, vacuuming, oil, UV and refrigerant recharge processes for execution.
[005] For the purposes of this invention we will focus on the components of the refrigerant recovery and recharge device which are required for recharging oil to the refrigeration equipment. In conventional refrigerant recovery and recharge devices uses a load cell to measure the weight of the oil bottle and a solenoid valve to connect or disconnect the oil bottle to refrigerant device. In either mode of operation fully automatic or manual mode the operator would need to key in the amount of oil that needs to be recharged. Operator specified oil quantity is charge in to refrigerant device by measuring the difference of load cell value at start to the current.
[006] The disadvantage of oil recharge method implemented in the conventional refrigerant recovery and recharge device is that it is costly solution due to the requirement of accurate load sensor and if there is any error in load sensor then this error translates to the oil recharged to the refrigeration equipment. Also it is important to ensure that the oil recharge process is carried out in a short time and in an efficient manner.

Brief description of the accompanying drawings
[007] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:
[008] Figure 1 illustrates a refrigerant recovery and recharge device 10 in accordance with this invention.

Detailed description of the invention
[009] Figure 1 illustrates a refrigerant recovery and recharge device 10. The refrigerant recovery and recharge device 10 is connected to refrigeration equipment 12. The connection between the refrigerant recovery and recharge device 10 and the refrigeration equipment 12 is done by switching pluralities of valves in a valve block 14. The pluralities of valves in the valve block 14 are solenoid valves. Recovery, vacuuming and recharge operation is performed by the refrigerant recovery and recharge device 10 based on the operator selection. Pluralities of solenoid valves are provided in the valve block 14 are energized to connect or disconnect the pluralities of passage to various components inside the refrigerant recovery and recharge device 10 and also to refrigeration equipment.

[0010] In accordance with the method of operating the refrigerant recovery and recharge device 10 of this invention the focus is on the oil recharge process wherein oil is recharged from the refrigerant recovery and recharge device 10 to the refrigeration equipment 12 without using any load sensor measurement. Irrespective of the mode of operation of the refrigerant recovery and recharge device 10 i.e fully automatic mode or manual mode, the oil recharge is done as disclosed below.

[0011] From the oil recovery process the amount of oil that needs to be recharged into the refrigeration equipment 12 is already known and same needs to be checked by operator and keyed in for oil recharge. For initiation of the oil recharge from the refrigerant recovery and recharge device 10 to the refrigeration equipment 12, the specific pulse width and number of pulses are required to be calculated internally for recharging the operator specified amount of oil. After determining the specific pulse width and number of pulses the oil is recharged into the refrigeration equipment 12 from the refrigerant recovery and recharge device 10.

[0012] The method in which the specific pulse width and number of pulses required for charging oil for the current size of refrigeration equipment 12 is calculated is explained below. The current size of refrigeration equipment 12 is determined by the refrigerant recharge quantity keyed in to the current refrigerant recharge and recovery device 10 for the current refrigerant recharge which is mandatory along with selection of oil recharge. Specific pulse width for every refrigerant equipment 12 size is calculated based on the equation A as shown below:

…A

[0013] Values of constant and power factor corresponds to the internal design of the refrigerant recovery and recharge device 10 and these values are required to determined once during development phase by iterative experimentation on minimum and maximum size of refrigeration equipment 12 to achieve to desired oil recharge accuracy. Further these values of constant and power factor are used for calculating the specific pulse width and number of pulses inside the oil recharge algorithm every time the operator selects to perform the oil charge without the load sensor value.

[0014] Based on the determined minimum and maximum pulse width and the determined minimum and maximum size of the refrigeration equipment 12, the power factor is calculated using the equation B as shown below.

…. B

[0015] After calculating the power factor as shown in formula B, the constant required for calculating specific pulse width is calculated. The constant is calculated based on a first combination of minimum pulse width and minimum size of the refrigeration equipment 12 using the equation B as shown below

..C

[0016] The constant value may also be calculated using a second combination of maximum pulse width and maximum size of the refrigeration equipment 12 using the equation C as shown below.

..D

[0017] From the equations B, C and D, the power factor and the constant is known. Based on the refrigerant recharge quantity keyed in to the refrigerant recovery and recharge device 10 by the operator, size of the refrigeration equipment 12 into which the oil is to be recharged is determined. And specific pulse width required for recharging the oil into the refrigeration equipment 12 can be calculated using the equation A as already shown above.

[0018] For the initiation of oil recharge from refrigerant recovery and recharge device 10 to refrigeration equipment 12, number of pulses of constant specific pulse width is required to be determined as per the equation E as shown below.

…E

[0019] Once the specific pulse width and number of pulses required for recharging the quantity of oil required for efficient functioning of the refrigeration equipment is calculated, the solenoid valves in the valve block 14 in the refrigerant recovery and recharge device 10 are operated in a manner such that they are switched from a closed position to an open position.

[0020] Based on the operation of the solenoid valves in the valve block oil is recharged into the refrigeration equipment 12. The calculated specific pulse width is used for recharging oil irrespective of the mode of operation the refrigerant recovery and recharge device 10.

CLAIMS

We Claim:
1. A method of operating a refrigerant recovery and recharge device (10) comprising the following steps:
- determining the specific pulse width for recharging oil from said refrigerant recovery and recharge device (10) to a refrigeration equipment (12); and
- determining the number of pulses of constant specific pulse width for recharging oil from said refrigerant recovery and recharge device (10) to a refrigeration equipment (12); and
- recharging oil from said refrigerant recovery and recharge device (10) to said refrigeration equipment (12) in dependence of the determined specific pulse width and number of pulses.

2. The method as claimed in claim 1, while determining specific pulse width, minimum and maximum pulse width for recharging a defined quantity of oil from said refrigerant recovery and recharge device (10) to said refrigeration equipment (12) is determined.
3. The method as claimed in claim 1, while determining specific pulse width, minimum and maximum size of the refrigeration equipment (12) is determined.
4. The method as claimed in claim 1, while determining specific pulse width, a power factor in dependence of said determined minimum and maximum pulse width and said determined minimum and maximum size of refrigeration equipment (12) is calculated.
5. The method as claimed in claim 1, while determining specific pulse width, a constant in dependence of a combination of minimum pulse width and minimum size of refrigeration equipment or maximum pulse width and maximum size of said refrigeration equipment (12).
6. The method as claimed in claim 1, calculating specific pulse width for recharging oil in dependence of size of the refrigeration equipment (12), said calculated power factor and said calculated constant for a quantity of oil to be recharged to said refrigeration equipment.

ABSTRACT
A method of operating a refrigerant recovery and recharge device is disclosed. The method comprises the following steps: determining the specific pulse width for recharging oil from the refrigerant recovery and recharge device to a refrigeration equipment; determining the number of pulses of constant specific pulse width for recharging oil from the refrigerant recovery and recharge device to a refrigeration equipment and recharging oil from the refrigerant recovery and recharge device to refrigeration equipment in dependence of the determined specific pulse width and number of pulses.
Reference figure: Figure 1