Patent Application
20080199628
This application relates to a method of masking a part to control the portions of the part that are subject to high temperature spray coating, in which the masking element has a hook and loop type fastener to secure the masking element to the part.
Various types of high temperature spraying are utilized to coat or otherwise treat parts in industrial operations. One type of high temperature spraying is plasma spraying. In plasma spraying, a material is coated onto selected locations on a part. Other portions of the part are masked such that the coating will not occur on those parts.
A rubber mask has often been utilized to cover the portions that are not to be coated. The rubber mask has traditionally been a continuous band of rubber. This band must be stretched over the portions of the part which are to be masked. This requires the operators to stretch the mask over the part, and is somewhat difficult to perform.
In other known masking techniques, the rubber mask may be split. Tape has been utilized to hold ends together. The tape is time consuming to use, and a special pattern has been used to ensure the tape does not come undone during the treatment. The taping requires specific training and skill by the operator who is to assemble the mask.
Also, a rubber tape has been applied to the part. This is perhaps the most labor-intensive way to mask the part. This requires a skilled operator and a good deal of time even compared to other masking techniques. Furthermore, operators who routinely perform this technique are sometimes subject to carpel tunnel syndrome, and other potential injuries.
Hook and loop type fasteners are known, and have been utilized in many applications. There are hook and loop type fasteners that are resistant to high temperatures. However, such hook and loop type fasteners have never been applied in combination with masks for plasma spray operations, or other high temperature spray coatings.
In a disclosed embodiment of this invention, a mask for masking a portion of a part to be subject to a high temperature coating operation has two distinct ends. A hook fastener portion is formed at one end, and a loop fastener portion is formed at the other. The hook and loop fasteners are resistant to high temperatures. In one embodiment, they may be metallic. Other materials may also be used. By providing the hook and loop type fastener, the mask may be easily placed around the part to be covered. Furthermore, the hook and loop type fastener is resistant to the high temperatures that are involved in the coating, and can be re-utilized. In general, the hook and loop type fasteners will survive for about as many coating operations as the rubber masking itself is usable. Typically, this would mean 5 to 10 spray operations. The high temperature coating operation is disclosed as a plasma spray coating, however the mask can be used in any type coating where masks are utilized.
In one embodiment, a single long strip of rubber mask material is provided with the hook and loop type fasteners at two distinct ends. This long strip is wrapped around the part. In another embodiment, shorter strip pieces are provided, each having a hook portion at one end and a loop portion at the other end. These several pieces can then be assembled together to conform to the specific size and shape of the part to be covered. In general, the mask is formed of a silicone rubber, as has been utilized in the prior art.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.
A part 48 that is to be subject to plasma spray coating (shown schematically at 50) is shown in
Portion are covered by masks 54. As shown, there are several masks 54 assembled on the part 48. The part shown is exemplary only, and the masking technique of this application can extend to many distinct types of parts. Applicant believes the inventive mask will especially benefit gas turbine engine components such as rotors, shafts, etc., that are to be coated. Even so, other parts to be coated by any high temperature coating technique will benefit from this invention.
As shown in
As shown in
One commercially available hook and loop type fastener is that available under the trademark Hi-Garde® available from Velcro. This hook and loop type fastener is constructed with stainless steel and can be utilized up to 800° F. (approximately 426° C.). Another material that may be utilized is available from McMaster Carr. An acceptable hook material is identified by part number 96225K41, and an acceptable loop material is identified by part number 96225K61. Of course, other materials capable of withstanding the temperature ranges expected to be experienced in the plasma flame spray coating may be utilized.
When the coating is complete with the inventive methods, the next step taken is to remove the mask. With the inventive hook and loop type fasteners, the mask and its hook and loop type fasteners may be re-utilized to coat a second part. It is believed the hook and loop fasteners can be re-used for as many times as the masks (5-6 coatings).
In addition, the use of the hook and loop type fasteners allows for more convenient storage of the masking elements. The masking elements can be hung by the fastener vertically, which is more space-efficient than the storage techniques that have been utilized for the band of rubber masks known in the part art.
While embodiments of this invention have been disclosed, a worker of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
