Abrading – Rigid tool – Rotary cylinder
Reexamination Certificate
2001-01-19
2002-09-17
Rachuba, M. (Department: 3723)
Abrading
Rigid tool
Rotary cylinder
C451S540000, C451S541000, C451S544000, C451S546000, C451S548000, C051S295000, C051S296000, C051S297000, C051S298000, C051S307000
Reexamination Certificate
active
06450870
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a vitrified grindstone which has a vitrified abrasive structure impregnated with a cured resin, and a method of manufacturing such a vitrified grindstone.
2. Discussion of the Related Art
There is known a vitrified grindstone having a vitrified abrasive structure, in which abrasive grains and an optionally used aggregate are held together by a glassy inorganic vitrified bonding agent, and in which a multiplicity of pores or voids are formed between the abrasive grains. Owing to excellent properties of the vitrified grindstone, such as a relatively high degree of strength with which the bonding agent holds the abrasive grains together, and a relatively easy dressing operation, the vitrified grindstone is widely used for precision grinding operations. In recent years, there is a need for a vitrified grindstone capable of performing a grinding operation with improved efficiency, to meet a demand for shortening of the required grinding time.
On the other hand, there has been proposed for practical use a vitrified grindstone wherein the proportion or content of the inorganic bonding agent is made relatively high for increasing a grade of the vitrified grindstone and also a degree of strength with which the inorganic bonding agent holds the abrasive grains together. This vitrified grindstone has a relative high hardness, and can meet, to some extent, the above-indicated need for improving the grinding efficiency. However, this vitrified grindstone is not completely satisfactory. Namely, the use of the inorganic bonding agent in a relatively large proportion assures an increase in the strength of the vitrified grindstone, which contributes to an improvement in the grinding efficiency, but considerably reduces the porosity of the vitrified abrasive structure and results in difficult or insufficient fracturing and removal of the abrasive grains, leading to relatively easy glazing or clogging of the surface of the vitrified grindstone, relatively easy chipping of the abrasive structure, relatively difficult dressing operation of the vitrified grindstone, and other drawbacks encountered during use of the vitrified grindstone as a grinding tool. In addition, the use of the inorganic bonding agent in the relatively large proportion is likely to cause various drawbacks during the manufacture of the vitrified grindstone, such as cracking or deformation of the grindstone and insufficient removal or burn-out of the primary binder of the inorganic bonding agent, in the firing process. The insufficient removal of the binder may cause the manufactured vitrified grindstone to have some amount of residual carbon.
Such a vitrified grindstone with reduced porosity may be manufactured by hot-pressing of the materials of the grindstone, and may be used for performing a highly efficient grinding operation. However, this manner of manufacturing the vitrified grindstone requires special manufacturing equipment which usually suffers from low manufacturing efficiency, leading to a relatively high cost of manufacture of the vitrified grindstone, and a considerable limitation in the range of size of the vitrified grindstone that can be manufactured.
SUMMARY OF THE INVENTION
It is therefore a first object of the present invention to provide a vitrified grindstone which has a vitrified abrasive structure impregnated with a resin, and which is less likely to suffer from the above-indicated drawbacks relating to its use and manufacture and assures a high degree of grinding efficiency.
It is a second object of the present invention to provide a method of manufacturing such a vitrified grindstone.
The first object may be achieved according to a first aspect of this invention, which provides a vitrified grindstone having a vitrified abrasive structure which has pores and which includes abrasive grains and an inorganic bonding agent that holds the abrasive grains together, wherein 10-95% of a total volume of the pores is filled with a cured resin.
In the vitrified abrasive structure of the present vitrified grindstone, a suitable volumetric percentage of the total volume of the pores or voids is filled with the cured resin, so as to prevent filling of the pores with metal particles which are removed from the workpiece during a grinding operation using the present vitrified grindstone and which would otherwise be fused in the pores, causing clogging or glazing on the grinding surface of the vitrified grindstone. It is also noted that since the resin filling the pores is softer than the abrasive grains, the surface of the vitrified grindstone is comparatively recessed at local spots corresponding to the resin-filled pores, during the grinding operation on the workpiece, so that the abrasive grains adjacent to the surface of the abrasive structure gradually fracture or break down and are removed, making it possible to prevent an excessive rise of the temperature on the workpiece surface due to an excessive amount of heat of friction which would be generated between the workpiece surface and the abrasive grains that remain dull, and also prevent chipping of the vitrified grindstone while permitting easy dressing of the vitrified grindstone. The abrasive grains which are only loosely held together by the inorganic bonding agent can be tightly held together with an additional bonding force provided by the cured resin, so that the cured resin functions to avoid early removal of those abrasive grains, assuring a high grinding ratio.
It is further appreciated that the arrangement in which 10-95% of the total volume of the pores is filled with the cured resin is effective to prevent the hardness of the grindstone from being excessively hardened by the impregnation of the vitrified abrasive structure with the cured resin, while assuring a high grinding ratio. Since an excessive increase in the hardness of the vitrified grindstone is prevented, the present vitrified grindstone can be easily dressed as needed, making it possible to prevent a reduction in the service life of the vitrified grindstone. If the volumetric percentage of the pores that is filled with the cured resin is smaller than 10%, the effect of the impregnation of the abrasive structure with the cured resin cannot be expected. If the volumetric percentage of the pores that is filled with the cured resin is larger than 95%, the vitrified grindstone is excessively hardened, making it difficult to dress the vitrified grindstone.
It is to be understood that the vitrified abrasive structure of the vitrified grindstone may further include an aggregate such that the abrasive grains and the aggregate are held together by the inorganic bonding agent.
According to a first preferred form of the first aspect of the invention, 40-90% of the total volume of the pores is filled with the cured resin. In the vitrified grindstone of this first preferred form, an excessive increase in the hardness of the vitrified grindstone is more reliably prevented owing to the arrangement in which at least 10% of the total volume of the pores remains unfilled with the cured resin. Further, since at least 40% of the total volume of the pores is filled with the cured resin, it is possible to more reliably prevent the conventionally encountered drawbacks such as easy filling of the pores with metal particles, easy glazing or clogging of the surface of the vitrified grindstone, easy chipping of the abrasive structure, and easy removable of the abrasive grains. Thus, the present vitrified grindstone can be easily dressed without having to increase a load applied to the vitrified grindstone, leading to a further increased grinding ratio and providing a further improved surface smoothness of the workpiece.
According to a second preferred form of the first aspect of the invention, the cured resin consists of at least one thermosetting synthetic resin which is selected from a phenol resin and an epoxy resin, so that the vitrified grindstone has a higher degree of hardness than where the resin consists of a
McDonald Shantese
Noritake Co., Limited
Oliff & Berridg,e PLC
Rachuba M.
LandOfFree
Vitrified grindstone having pores partially filled with... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Vitrified grindstone having pores partially filled with..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Vitrified grindstone having pores partially filled with... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2889496