Description:FIELD OF THE INVENTION
[001] The present invention relates to a spindle of a machine tool. Particularly, the present invention relates to a spindle of a computer numerical control (CNC) machine tool used for chamfering of tubes. More particularly the present invention relates to the design of spindle for semi-automatic heavy duty chamfering machine (west coast insert), which is being used for edge preparation of tube/pipe for coil and panel in power plant fabrication.
BACKGROUND OF THE INVENTION
[002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[003] Chamfering of tubes ends is a common procedure in mechanical industry such that the chamfered ends of the tubes are placed against each other and butt welding is performed therein to achieve the tubes of desired length. The tubes joined together in this procedure are typically of economizer, super heater, water walls etc., Chamfering operation is also carried out for panels in power plant fabrication.
[004] The tubes of the economizer, super heater, water walls etc., are typically made of steel and chamfered on a heavy duty chamfering machine capable of chamfering of tubes of outer diameter ranging from 38.1mm to 63.5mm and wall thickness up to 12.5mm. Different tool inserts are used in the machine tool to carry out chamfering operation on tubes of different sizes for accessibility of the machine tool. Chamfering operation can be carried out from outside/inside of the panel depending on the space constraints.
[005] Referring to the figure 1(a), there is provided a chamfering machine (100) comprising a FRL (Filter, Regulator and Lubricator) compressed air system unit (102), an air motor (104), a main gear assembly (106), a spindle (108), a clamping unit (110) and a feeding gear assembly (112).
[006] The FRL compressed air system unit (102) supplies clean compressed air to the air motor (104) and an air cylinder of the clamping unit (110) through a control valve. The air motor (104) converts the received compressed air at a pressure of 5 to 6 bar from the FRL compressed air system unit (102) in to mechanical energy. The mechanical energy from the air motor (104) transfers to the main gear assembly (106) and in turn converts into rotation and feed of the spindle (108). A tool is locked to the spindle 108 which rotates and moves along with the spindle (108) to perform chamfering operation on a workpiece.
[007] The workpiece is clamped in a workpiece holder (114) concentric to the spindle (108) by means of the compressed air from the air cylinder of the clamping unit (110). Feed is given to the workpiece against the tool of the spindle (108) through the feeding gear assembly (112).
[008] Referring to the figure 1(b), the spindle (108) is formed in three portions viz., a first portion (108(a)), a second portion (108(b)) and a third portion (108(c)). The diameter of the spindle (108) gradually decreases from the first portion (108(a)) to the third portion (108(c)). The third portion (108(c)) of the spindle (108) holds the tool. The second portion (108(b)) extends to a region generally indicated by a reference numeral (B-C). The third portion (108(c)) extends to a region generally indicated by a reference numeral (A-B).
[009] The chamfering machine (100) can handle workpieces of the following specification:
Minimum Diameter of the tube 38.1 mm
Maximum Diameter of the tube 63.5mm
Maximum thickness of the tube 12.5mm

[010] The design specification of the second portion (108(b)) and the third portion (108(c)) of the spindle (108) is as follows:
Spindle diameter of the second portion 108(b) indicated by a reference numeral A2 23mm
Spindle diameter of the third portion 108(c) indicated by a reference numeral A1 12mm
Length of the third portion 108(c) indicated by a reference numeral B1 37mm

[011] It can be observed from the above table that the diameter (A2) of the second portion (108(b)) of the spindle (108) is more than the diameter (A1) of the third portion (108(c)) of the spindle (108).
[012] The spindle (108) rotates at various speeds along with feed towards the workpiece. During chamfering operation, the following forces act on the spindle (108):
a) Compressive force due to feed provided to the spindle (108) against the workpiece during chamfering operation. Compressive stress is developed on the spindle (108) during chamfering of tubes of higher thickness and the third portion (108(c)) and the second portion (108(b)) of the spindle (108) typically called as
cutting end portion are under radial compressive load which may cause deformation in the spindle (108) ultimately resulting in the failure of the spindle (108).
b) Torque produced due to rotation of the spindle (108) for removing material from the work piece with the help of the tool causes bending in the spindle (108) which ultimately results in the failure of the spindle (108).
[013] The deformation or bend in the spindle (108) produces non-precise and low quality work piece.
[014] Also another reason for failure of the spindle (108) is concentration of load. Load concentration during chamfering operation is more at the sharp edges and geometry changes i.e. at portions of (B and C) when compared to the flat surfaces. So, most of the times, breaking occurs at the portions (B and C) of the spindle (108). More specifically, breakage takes place frequently at the portion (B) of the spindle (108) as the diameter at the portion (C) of the spindle (108) is higher than the thickness at the portion (B) of the spindle (108). The length (B1) of the third portion (108(c)) is more from the chamfering location which is also one of the reasons for the breakage of the spindle (108) at the portion (B).
[015] Therefore, there is felt a need for development of a spindle for a machine tool which can withstand loads from the chamfering operation more effectively, thereby addressing issues of prior art.
OBJECTS OF THE INVENTION
[016] An object of the present invention is to provide spindle for a machine tool, which is highly reliable.
[017] Another object of the present invention is to provide a spindle for a machine tool which produces precise and quality work pieces during chamfering operation.
[018] One more object of the present invention is to increase the mean time between failure of the spindle and thereby increase the availability of the chamfering machine.
[019] Still another object of the present invention is to provide a spindle which improves the accuracy of the machine tool.
[020] Further another object of the present invention is to provide a spindle that improves the productivity of the chamfering machine.
[021] These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.
SUMMARY OF THE INVENTION
[022] One or more drawbacks of conventional systems and process are overcome, and additional advantages are provided through the apparatus and a method as claimed in the present disclosure. Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered to be part of the claimed disclosure.
[023] In accordance with the present invention a spindle for a machine tool is provided. The spindle for a machine tool comprises a first portion, a second portion, a third portion and a fourth portion formed in sequence with gradual decrease in diameter from the first portion to the fourth portion. The fourth portion holds a tool for chamfering operation. The third portion and the fourth portion are developed to have a predetermined diameter and a predetermined length such that they can withstand the compressive force and torque arising from the chamfering operation of the tubes. As the fourth portion extending to the predetermined length is close to the area where chamfering operation is carried out, the moment of all the resultant forces on the fourth portion are minimum.
[024] The first portion of the spindle is locked to a spindle housing by means of a bearing provided there between i.e. in between the first portion of the spindle and the spindle housing.
[025] Fillets are provided at the mating location of the third portion with the second portion and at the mating location of the fourth portion with the third portion to minimize concentration of load at those locations.
[026] According to this invention, there is provided a spindle for a machine tool comprising a plurality of portions including a first portion and a second portion formed in sequence with gradual decrease in diameter from said first portion, characterized in that the plurality of portions comprise of the first portion, the second portion, a third portion and a fourth portion formed in sequence with gradual decrease in diameter from said first portion to said fourth portion forming a single structure, wherein
[027] said third portion extending to a region has predetermined diameter and a predetermined length; and
[028] said fourth portion extending to a region has a predetermined diameter and a predetermined length to hold a tool for chamfering, wherein said predetermined diameter and said predetermined length of said third portion are 17mm and 23mm respectively, wherein said predetermined diameter and said predetermined length of said fourth portion are 12mm and 14mm respectively.
[029] Said first portion of said spindle is locked to a spindle housing by means of inner diameter of a bearing encompassing said first portion and outer diameter of said bearing adapted to mate with inner diameter of said spindle housing.
[030] The bearing is fixed in position on the first portion of the spindle and its loosening is avoided by a space provided between the bearing and first portion of the spindle/spindle housing.
[031] The bearing includes double row angular contact ball bearing with increased width.
[032] A portion at the mating location of said third portion and said second portion and a portion at the mating location of said fourth portion and said third portion are filleted with a predetermined radius to minimize concentration of load.
[033] Said second portion extending to a region has a predetermined diameter of 23mm.
[034] The region D-B of the third portion is having two times more strength.
[035] The load carrying capacity at the point B is increased to double due to increase in diameter.
[036] At the fourth portion extending the region A-D, the moment of all the resultant forced produced during chamfering operation is minimum as the region A-D is close to the cutting area and hence, breaking at the region A-D is also minimized.
[037] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.
[038] It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.
[039] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
[040] The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and processes that are consistent with the subject matter as claimed herein, wherein: -
Figure 1(a) illustrates a perspective view of a chamfering machine according to the prior art;
Figure 1(b) illustrates an enlarged perspective view of a spindle of a machine tool of the chamfering machine of figure 1(a) of prior art;
Figure 2(a) illustrates a perspective view of a spindle of a machine tool in accordance with an embodiment of the present invention; and
Figure 2(b) illustrates a perspective view of assembling the spindle of figure 2(a) into a spindle housing.
[041] The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAIL DESCRIPTION OF THE PRESENT INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS OF PREFERRED EMBODIMENTS
[042] While the embodiments of the disclosure are subject to various modifications and alternative forms, specific embodiment thereof have been shown by way of example in the figures and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.
[043] A preferred embodiment will now be described in detail with reference to accompanying drawings. The preferred embodiment does not limit the scope and ambit of the invention. The description provided is purely by way of example and illustration.
[044] The present invention is based on a concept pertinent to a spindle for a machine tool.
[045] Referring to fig 2(a), in accordance with the present invention, there is provided a spindle (208) held in a spindle housing (210) and formed in four portions viz., first portion (208(a)), second portion (208(b)), third portion (208(c)) and fourth portion (208(d)). The diameter of the spindle (208) gradually decreases from the first portion (208(a)) to the fourth portion (208(d)). The fourth portion (208(d)) of the spindle (208) holds the tool.
[046] The first portion (208(a)) and the second portion (208(b)) of the spindle (208) remains unchanged in comparison to the spindle (108) of the prior art. The second portion (208(b)) extends to a region generally indicated by a reference numeral B-C and has the diameter of 23mm generally indicated by a reference numeral A2.
[047] The third portion (208(c)) and the fourth portion (208(d)) of the spindle (208) combined together extends to a region generally indicated by a reference numeral A-B. The length of the third portion (208(c)) and the fourth portion (208(d)) of the spindle (208) combined together is 37mm and is generally indicated by a reference numeral B1. The third portion (208(c)) extends to a region generally indicated by a reference numeral D-B. The fourth portion (208(d)) extends to a region generally indicated by a reference numeral A-D. The length of the third portion (208(c)) is 23mm and is generally indicated by a reference numeral B2. The length of the fourth portion (208(d)) is 14mm and is generally indicated by a reference numeral B3. The diameter of the third portion (208(c)) is 17mm and is generally indicated by a reference numeral A3. The diameter of the fourth portion (208(d)) is 12mm and is generally indicated by a reference numeral A1.
[048] The length B2 of the third portion (208(c)) is 62% of the combined length B1 of the third portion (208(c)) and the fourth portion (208(d)). The diameter A3 of the third portion (208(c)) is 5mm more than the diameter A1 of the fourth portion (208(d)). The region D-B of the third portion (208(c)) is having two times more strength than the region A-B of the third portion (108(c)) of the prior art. The load carrying capacity at the point B is increased to double due to increase in diameter. At the fourth portion (208(d)) extending the region A-D, the moment of all the resultant force produced during chamfering operation is minimum as the region A-D is close to the cutting area and hence, breaking at the region A-D is also minimized. The portion at the mating location of the third portion (208(c)) and the second portion (208(b)) is generally indicated by a reference numeral B. The portion at the mating location of the fourth portion (208(d)) and the third portion (208(c)) is generally indicated by a reference numeral D. Fillets of radius R1 (5 to 6 mm) are provided at the portions B and D to minimize concentration of load. In the present invention, the stiffness of the spindle (208) is increased and hence, the chances of deformation or bending of the spindle (208) are minimized.
[049] As the diameter A3 of the region D-B of the third portion (208(c)) is increased and in order to bear the load of the spindle (208) engaged into the spindle housing (210), the specification of the bearings used has been changed and the details are provided herein below Table 1.
Description Original brg details Selected brg details
Brg type Single row angular contact ball brg Double row angular contact ball brg
Brg no. 7001 3001-B-TVH
Make INA/FAG INA/FAG
Qty per m/c 2 1
ID 12 12
OD 28 28
Width 8 12
Dynamic Load rating 5050N 6200N
Static Load rating 2460N 3550 to 3750N

TABLE 1
[050] It can be inferred from the above table 1 that the width of the newly selected double row angular contact ball bearing has been increased by 4mm in comparison to the single row angular contact ball bearing keeping its inner diameter and the outer diameter same as the old bearing used in prior art.
[051] Referring to the figure 2(a) & 2(b), the first portion (208(a)) of the spindle (208) is locked to the spindle housing (210) by means of inner diameter of the bearing (212) encompassing the first portion (208(a)) of the spindle 208 and outer diameter of the bearing (212) adapted to mate with inner diameter of the spindle housing (210). The bearing (212) is fixed in position on the first portion (208(a)) of the spindle (208) and its loosening is avoided by means of a spacer (214) provided between the bearing (212) and the first portion (208(a)) of the spindle (208)/spindle housing (210).
[052] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases, it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.
[053] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.
[054] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particulars claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogues to “at least one of A, B and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B”.
[055] The above description does not provide specific details of manufacture or design of the various components. Those of skill in the art are familiar with such details, and unless departures from those techniques are set out, techniques, known, related art or later developed designs and materials should be employed. Those in the art are capable of choosing suitable manufacturing and design details.
[056] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.
[057] The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.
[058] While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Claims:1) A spindle (208) for a machine tool comprising a plurality of portions including a first portion (208(a)) and a second portion (208(b)) formed in sequence with gradual decrease in diameter from said first portion (208 (a)) characterized in that the plurality of portions comprise of the first portion (208(a)), the second portion (208(b)), a third portion (208(c)) and a fourth portion (208(d)) formed in sequence with gradual decrease in diameter from said first portion (208(a)) to said fourth portion (208(d)) forming a single structure, wherein
said third portion (208(c)) extending to a region (D-B) has predetermined diameter (A3) and a predetermined length (B2); and
said fourth portion (208(d)) extending to a region (A-D) has a predetermined diameter (A1) and a predetermined length (B3) to hold a tool for chamfering, wherein said predetermined diameter (A3) and said predetermined length (B2) of said third portion (208(c)) are 17mm and 23mm respectively, wherein said predetermined diameter (A1) and said predetermined length (B3) of said fourth portion (208(d)) are 12mm and 14mm respectively.
2) The spindle (208) as claimed in claim 1, wherein said first portion (208(a)) of said spindle (208) is locked to a spindle housing (210) by means of inner diameter of a bearing (212) encompassing said first portion (208(a)) and outer diameter of said bearing (212) adapted to mate with inner diameter of said spindle housing (210).
3) The spindle (208) as claimed in claim 1 or 2, wherein the bearing (212) is fixed in position on the first portion 208(a) of the spindle (208) and its loosening is avoided by a space (214) provided between the bearing (212) and first portion (208(a)) of the spindle (208)/ spindle housing (210).
4) The spindle (208) as claimed in the claims 1-3, wherein the bearing (212) includes double row angular contact ball bearing with increased width.
5) The spindle (208) as claimed in the claims 1-4, wherein a portion (B) at the mating location of said third portion (208(c)) and said second portion (208(b)) and a portion (D) at the mating location of said fourth portion (208(d)) and said third portion (208(c)) are filleted with a predetermined radius (R1) to minimize concentration of load.
6) The spindle (208) as claimed in the claims 1-5, wherein said second portion (208(b)) extending to a region (B-C) has a predetermined diameter (A2) of 23mm.
7) The spindle (208) as claimed in the claims 1-6, wherein the region D-B of the third portion (208(c)) is having two times more strength.
8) The spindle (208) as claimed in the claims 1-7, wherein the load carrying capacity at the point B is increased to double due to increase in diameter.
9) The spindle (208) as claimed in the claims 1-8, wherein at the fourth portion (208(d)) extending the region A-D, the moment of all the resultant forced produced during chamfering operation is minimum as the region A-D is close to the cutting area and hence, breaking at the region A-D is also minimized.