CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit ofU.S. Provisional Patent Application, Serial No. 63/389,545, filed on 15 July 2022. The co-pending provisional application is hereby incorporated by reference herein in its entirety and is made a part hereof, including but not limited to those portions which specifically appear hereinafter.

BACKGROUND OF THE INVENTION

This invention relates generally to filters for air/oxygen/nitrogen assist lines in cutting machines and, more particularly, to a modular filter panel with high filter efficiency for higher power lasers, which are much more susceptible to particle dust ingas lines.

Most laser cutting machines have little or no filtration for the assist gases (i.e., oxygen, nitrogen, and/or compressed air). Those including filtration typically have one small filter with a 1-10 micron filter element. With CO2 lasers this was adequate because even if the filters were saturated and allowed dust or hydrocarbons to get into the cutting head, the impurities would bum onto the ZeSe lens and the operator could clean the lens or replace it. Fiber laser beam wavelength is 10 times smaller than the CO2 lasers. This means they absorb ten times more power, and any dust inside the head will generally cause the unit to fail. The optics inside the cutting heads cannot be accessed as they are sealed units. So when the optics are damaged the complete cutting head requires replacement. Most heads are around $30,000 and they can be replace up to 3-4 times a year in particularly bad worksites.

With fiber lasers it is quite common to cut using high pressure air and nitrogen gas generators due to the much larger power compared to CO2. If these are not filtered properly, or if the boosters on the nitrogen generator were to fail, they will pass through oil and contaminate the whole gas system, which will mean replacing all the hoses, regulators, solenoid valves, proportional valves, cutting head, etc. This could cost in excess of $80,000, in addition to the downtime to obtain parts and do the repair work, which is also very costly.

Cutting head manufactures are in a losing battle. The larger the power the more susceptible the optics and cover windows are to contamination. It took CO2 lasers approximately 30 years to reach a maximum power of 7KW. By contrast in just about 10 years, fiber lasers are now up to 60KW in power. The cutting head suppliers tend to focus on better sealing to the heads, more protective windows, and better optical materials to stop head failures, but failures are becoming more frequent as the power increase is outpacing the cutting heads.

Thus there is a continuing need for improved delivery of clean assist gases for laser cutting devices.

SUMMARY OF THE INVENTION

A general object of the invention is to provide an improved filtration apparatus and method, particularly for laser cutting machines. A more specific objective of the invention is to overcome one or more of the problems described above.

The invention addresses the root cause of the problem, which are contaminants in the supply lines to the lasers. The invention increases the filtration by a factor of approximately 100 times finer than what is currently being supplied with laser systems, and helps ensure no particles and/or oil vapor gets through to the cutting head. The invention includes a multi-stage (e.g., 2-stage, 3-stage, or more) filtration using large high pressure filters to capture contaminants. This solution is cost effective and can save tens of thousands of dollars on expensive repairs and extensive downtime.

The general object of the invention can be attained, at least in part, through a filter system for a laser cutting machine, including a multi-stage filter panel connectable to the assist line, generally referred to as a gas assist line, of the laser cutting machine. In embodiments of the invention, the multi-stage filter panel includes at least a two-stage particulate filter panel. The two-stage particulate filter panel desirably includes a first stage including at least one filter above 0.5 micron, desirably between 0.5 and 1.5 microns, and preferably approximately 1 micron, and a second stage downstream of the first stage including at least one filter under 0.5 micron, desirably under 0.1 micron, more desirably under 0.05 microns, and preferably approximately 0.01 micron.

In embodiments of this invention, the multi-stage filter panel includes an oil vapor removal filter (i.e., forming a three-stage filter), preferably downstream of one or more of the particulate filters. The oil vapor removal filter is desirably used in gas assist lines to detect oil therein.

Embodiments of the invention further include a filter monitoring system configured to determine that the filters need to be replaced. The filter monitoring system monitors and determines a pressure drop across the multi-stage filter panel. Additionally or alternatively, an oil or oil vapor sensor can be used in combination with the filter monitor system to detect oil within the fluid line(s), such as due to mechanical failures of generator components upstream of the filters.

The invention further includes a method of filtering gas assist lines for a laser cutting machine. The method includes: filtering a gas assist line with a first filter having a first filter value; and filtering the fluid gas assist line with a second filter having a second filter value that is lower than the first filter value. The first and second filters are desirably particulate filters, and the method can further include a step of filtering the gas assist line for oil vapor. The method of embodiments also desirably includes determining that the filters need to be replaced by determining a pressure drop across the filters.

Other objects and advantages will be apparent to those skilled in the art from the following detailed description taken in conjunction with the appended claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic of a filter panel installation, according to one embodiment of this invention.

Fig. 2 is a schematic of a filter panel installation, according to one embodiment of this invention.

Fig. 3 is a schematic of a filter panel installation, according to one embodiment of this invention.

Fig. 4 is a schematic of a filter panel installation, according to one embodiment of this invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a filter system for a laser cutting machine.

The filter system includes a multi-stage filter panel connectable to a gas assist fluid line of the laser cutting machine. In embodiments of the invention, the multi-stage filter panel includes at least a two-stage particulate filter panel, including, in a direction of fluid flow, a first value, larger particulate size filter followed by a second value, smaller particulate size filer, and then preferably followed by vapor removal filter.

Fig. 1 shows gas assist lines for a laser cutting machine (not shown), such as metal laser cutting machines available from Trumpf™, Bystronic™, Amada™, or LVD Laser™. The gas assist lines include a nitrogen line 12 and an oxygen line 14. The nitrogen line can be sourced from any suitable nitrogen gas or liquid nitrogen source. Fig. 1 shows a filter installation 20 according to one embodiment of this invention. The filter installation 20 includes a one-stage filter 22 for oxygen line 14, preferably a 0.01 micron filter or equivalent, depending on need. The filter installation 20 further includes a three-stage filter panel 30 for the nitrogen line 12. The filter panel 30 includes a first stage filter 32 for a larger particulate size, which is upstream of a second stage filter 34 for a smaller particulate size. As an example, the first stage filter 32 can be a 0.5 to 2 micron particulate filter, preferably about a 1 micron filter, and the second stage filter 34 can be a 0.005 to 0.02 micron particulate filter, preferably about a 0.01 micron filter.

In embodiments of this invention, as shown in Fig. 1, The filter panel 30 includes an optional but generally preferred third stage vapor removal filter 36. The vapor removal filter is desirably an oil vapor removal filter, such as including activated carbon, to 0.003mg/m3.

Various and alternative filter sizes, shapes, ratings, and configurations are available for implementation of the invention, depending on need. As an example, the filter panels for one or both of the gas assist lines can be integrated into a common filter housing, or be separately attached filters for the lines. The oxygen line can further include a multi-stage filter such as shown and/or described for the nitrogen line, although the oil filter may not be needed as existing oxygen sources typically have additional safety measures to avoid contamination due to the ignition risk. The filter capacities can be changed, depending on need. For example, increasing the capacity and flow of the filters may be necessary for even higher power lasers (i.e., 20KW and 60KW). The nitrogen/mix/air flow requirements are also increasing up to <200m3/h whereas in the past 140m3/h was the maximum.

Fig. 2 shows a filter installation 120 according to anther embodiment of this invention, particularly suitable for single high pressure gas channel lasers. The oxygen and nitrogen assist lines 112 and 114, and the filter 122 and filter panel 130 of filters 132, 134, and 136, mirror Fig. 1. The system further includes a mixed/general air line 116 including a filter panel 140, including filters 142, 144, and 146 matching or similar in size and/or type to the filters 132, 134, and 136, respectively, of the nitrogen line 114. The general air line 116 and the nitrogen line 114 are alternatively connected by valves 160 and 162, thereby allowing switching between the two lines or other adjustment to the nitrogen assist. The valves 160 and 162 can be used to shut off the respective lines, such as each directly to the cutting machine. An additional high pressure line 165 and valve 166 can be used to connect and combine or alternative between the nitrogen line 114 and the mixed/general air line 116. A programmable logic controller 150 can be included to control and actuate the valves, such as from a computerized control panel.

Fig. 2 further shows a flow restriction 170 (e.g., 0.3-6 LPM) and regulator 172 (0-6 bars). The flow restrictor 170 provides a nitrogen purge line for the cutting head, especially if the same high pressure gas input is used for high pressure air cutting or mix gas. The purge on the cutting heads requires high purity nitrogen (i.e., >99.998%)

The above filter panel embodiments address contamination issues during normal conditions of dust and impurities in the gas supplies. The filters may be overpowered by catastrophic failures within the air and nitrogen boosters, or other contamination in the supply sources. If such failure were to occur the filters could be saturated within a short time and oil may be able to pass through and cause major damage. Also, the filters generally need to be replaced, such as every 6-12 months, depending on the quality of the gas. Negligence to do so can also saturate the filters over time, which will allow oil carry over and other contaminants to pass

To protect against these potential issues, embodiments of the invention, such as shown in Figs. 1 and 2, include a cost effective programmable logic controller (PLC), or equivalent controller, driven system that monitors the inlet and outlet pressure of the filters. As shown in Fig. 3, pressure sensors 52 and 54, placed on the opposing sides (i.e., upstream and downstream) of the filter panel 130 as described in Fig. 1, provide line pressure measurements for the PLC 50. The pressure drop through all three filters corresponds to a saturation of the filter elements. A warning can be sent to replace the filters at a predetermined pressure differential between the sensors, and if the pressure drop reaches a predetermine pressure value that is too high, the system gas supply can be automatically shut down via a high pressure solenoid valve 160 to protect the laser gas cutting system. The monitoring is real-time and 24/7 so as to protect against catastrophic failures of gas supply equipment.

In embodiments of this invention, the system further includes an oil sensor, preferably an oil vapor sensor, as an alternative or in addition to the pressure sensors of Fig. 3. Fig. 4 shows the system of Fig. 2, including an oil sensor 180 connected to, for example only, the nitrogen line 112, preferably via a further regulator 182. The oil sensor 180 is in communication with the controller 150. To protect against saturation of the filters due to excessive oil carry over, or hydrocarbons in liquid or vapor form, the oil sensor 180 and controller 150 will shut the nitrogen (and/or the air or mix gas supplies) upon detecting a predetermined amount of oil to protect the pipework and gas components in the laser including the laser cutting head.

The invention also protects the lasers against bad gas pipe installations, such as where the pipefitters have not used degreased copper pipes or have not flushed the silver solder joints properly.

Thus, the invention provides a cost-effective way to protect expensive high-end laser cutting machines.

The invention illustratively disclosed herein suitably may be practiced in the absence of any element, part, step, component, or ingredient which is not specifically disclosed herein.

While in the foregoing detailed description this invention has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purposes of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the invention.