Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Forming nonplanar surface
Reexamination Certificate
1998-06-26
2001-10-30
Huff, Mark F. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Forming nonplanar surface
C430S320000, C427S239000, C216S008000, C123S668000
Reexamination Certificate
active
06309806
ABSTRACT:
BACKGROUND TO THE INVENTION
This invention relates to a method of providing the inside surface of a hollow object with at least one microscopic feature such as a valley or pit. More particularly but not exclusively the invention relates to a method of providing a microscopic feature for the retention of lubricant, in the inside surface of a cylinder lining in which a piston operates.
Description of the Prior Art
Conventionally the inside surfaces of cylinder liners are honed by a mechanical honing tool to a specified roughness to provide microscopic features in the form of valleys, which in use retain oil.
Most commonly, such features have been provided by a mechanical tool comprising a plurality of diamond or other cutting elements and the tool being rotated in the hollow of the liner to cut the features in the honed inside surface. However although such diamond cutting tools are not expensive per boring operation, they usually require to be mounted on a machine head which is capable of movement about multiple axes, which is expensive. Also, with such a mechanical technique, one can achieve only limited control over the distribution and depth of features formed in the honed inside surface, and it is not convenient to provide any variation in the nature of microscopic features along the cylinder liner, as is desirable, so that those portions of the liner which are most prone to wear, can be lubricated more than less wear-prone portions.
Another proposal, e.g. as described in UK patent application 2278563 has involved the use of a laser beam which is manipulated to cut a predetermined pattern of features into the honed inside surface of the liner, but a very high power laser beam is required which is undesirable and the extent to which the beam can be conveniently manipulated is restricted. Also, because using such a method, the metal of the liner is essentially melted to provide the microscopic features, microscopic burs and regions of hard carbide tend to be formed at the edges and/or bases of the features which are undesirable as they may interfere with the efficiency of the features to retain a desired amount of lubricant. Loosely attached hard carbide can form abrasive particles that may damage an engine and a build up of material at the edges of the lubricant channels has to be removed by an additional mechanical honing stage after the laser “structuring” stage.
It has also been proposed, e.g. in U.S. Pat. No. 2,968,555 to provide microscopic features by chemical etching. The inside surface of the cylinder liner is coated with a photo-sensitive coating which is exposed to light through a mask and then the coating is developed to remove the exposed portions and leave openings therethrough. Etching substance is applied to etch the inside surface of the liner through the openings. Although such a method enables close control of the depths of the microscopic features, there is a problem in that it is necessary to insert a mask into the hollow of the liner and apply it to the coated inside surface of the liner. If one winds a mask into position in a helical form, it is difficult to join the edges of the mask to provide continuity along the liner, and thus it is difficult consistently to achieve a preselected pattern of microscopic features.
SUMMARY OF THE INVENTION
According to one aspect of the invention we provide a method of providing the inside surface of a hollow object with at least one microscopic feature comprising the steps of coating at least a part of the inside surface with photo-sensitive material, directing light onto the material to photo-expose a selected portion of the material, removing the exposed selected portion or the unexposed material thereby to leave an opening through the coating, applying an etching substance to etch the inside surface through the opening to form a microscopic feature in the inside surface, characterised in that the light which is directed onto the photo-sensitive material comprises a collimated beam and during exposure, the beam and the inside surface are relatively moved so that the beam impinges upon the selected portion of the photo-sensitive coating to be exposed.
Thus by utilising a method according to the invention it is possible to achieve consistently the provision of one or a pattern of microscopic features in the inside surface of e.g. a cylinder liner. By controlling the relative movement between the light beam and the inside surface during exposure an opening or openings may be provided in any desired position in the coating and to any desired pattern. Hence, the topography, of the microscopic feature or features formed during etching can accurately be controlled. Because the microscopic features are written on to the photo-sensitive material directly by the light beam, there is no need to insert a mask in the hollow through which the photo-sensitive material needs to be exposed.
Preferably the collimated beam is of laser light of a wavelength to which the photo-sensitive coating is sensitive, but unlike the prior art method described above which utilises a laser, the laser used to provide the light beam may be of low power.
With a suitable photo-sensitive material, possibly the low power laser light may itself remove selected portions of the photo-sensitive coating. Preferably though, subsequent to exposure, the coating is chemically treated, e.g. by dipping the object in a bath of the treating chemical, to remove the exposed portion of the coating or the unexposed coating, depending on the nature of the photo-sensitive coating. It will be appreciated that the photo-sensitive coating may be of the kind which is changed on exposure to light of a particular wavelength such that it may subsequently be chemically removed by developing, or the coating material may be of the kind which is changed on exposure to light of a particular wavelength such as to make it inert to a chemical which may be used to remove the unexposed photo-sensitive material.
The beam of laser or other light may conveniently be manipulated, e.g. by means of one or more mirrors at least one of which may be located in the hollow, relative to the inside surface, and in this way, the collimated beam may be directed to follow a predetermined path across the inside surface during exposure, thus to enable a predetermined pattern or patterns of openings to be provided through the photo-sensitive material, either when the exposed portions or unexposed material is removed, and hence so that a predetermined pattern or patterns of microscopic features may be provided in the inside surface during etching.
If desired, the pattern of microscopic features may be varied over the inside surface so as to provide a greater density or different pattern of microscopic features over one region of the inside surface when compared with another region of the inside surface.
Thus particularly in a cylinder lining, at the position where in use, a piston ring turns over as the direction of reciprocation of the piston in the liner is reversed, a greater density or different design of microscopic features may be provided to enable greater lubrication at that position.
The method of the invention may be preformed in conjunction with a conventional honing technique whereby prior to coating the inside surface, the inside surface may be honed to a roughness of for example, less that 2 &mgr;m preferably of about 1 &mgr;m maximum peak to valley height.
The coating of photo-sensitive material may be applied to the inside surface of the object by any desired means. However most conveniently the inside surface is coated by dipping the object in a bath of photo-sensitive material or by spraying.
The etching substance may be applied by dipping the object in a bath of etching substance from which the object is removed from after a predetermined time, and the etching substance may be removed or neutralised e.g. by washing after a predetermined period of time, so as to control the depth of the microscopic feature (or features) formed in the inside surface of the object. Alternatively the etching
Lenthall John Stanley
Marples Martin
Barreca Nicole
GKN Sheepbridge Stokes Limited
Huff Mark F.
Marshall Gerstein & Borun
LandOfFree
Method of providing microscopic features does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of providing microscopic features, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of providing microscopic features will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2569963