Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C29/00—Bearings for parts moving only linearly
  • F16C29/04—Ball or roller bearings
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C29/00—Bearings for parts moving only linearly
  • F16C29/004—Fixing of a carriage or rail, e.g. rigid mounting to a support structure or a movable part
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C29/00—Bearings for parts moving only linearly
  • F16C29/005—Guide rails or tracks for a linear bearing, i.e. adapted for movement of a carriage or bearing body there along
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C29/00—Bearings for parts moving only linearly
  • F16C29/04—Ball or roller bearings
  • F16C29/06—Ball or roller bearings in which the rolling bodies circulate partly without carrying load
  • F16C29/063—Ball or roller bearings in which the rolling bodies circulate partly without carrying load with a bearing body, e.g. a carriage or part thereof, provided between the legs of a U-shaped guide rail or track
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
  • F16C33/30—Parts of ball or roller bearings
  • F16C33/58—Raceways; Race rings
  • F16C33/62—Selection of substances
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
  • F16C33/30—Parts of ball or roller bearings
  • F16C33/58—Raceways; Race rings
  • F16C33/64—Special methods of manufacture
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
  • F16C33/30—Parts of ball or roller bearings
  • F16C33/66—Special parts or details in view of lubrication
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T29/00—Metal working
  • Y10T29/49—Method of mechanical manufacture
  • Y10T29/49636—Process for making bearing or component thereof
  • Y10T29/49641—Linear bearing

Definitions

• the present invention relates to a linear guide rail and in particular relates to a guide rail suitable for the linear movement of loads.
• linear guide rails Different types are known.
• the known linear guide rails which are similar to those of the invention are commonly composed of a metal section which extends along the path along which the load is to be moved.
• a slider which is suitable for receiving the load mounted thereon, is free to move along the section.
• the contact between the slider and the guide rail is provided by means of rolling elements, such as wheels, balls, rollers or the like.
• the wheels in turn are preferably mounted on rolling bearings.
• the slider comprises a number of wheels and the guide rail comprises raceways suitable for contact with the wheels.
• the entire load is therefore transferred by the surfaces making contact between the wheels and the linear guide rail. Since such surfaces are usually fairly small and the movement of the slider along the guide rail is fairly frequent, it is required to harden superficially the raceways on which the wheels rest.
• the known method for manufacturing the guide rails is described below.
• the rough-formed guides are drawn sections with the desired cross-section and to a length of up to 4 metres.
• the rough-formed guides are made of steel, preferably C43, C50 or lOOCr6.
• a first step consists in increasing the surface hardness of the raceways of the rolling elements.
• This step normally consists in surface tempering by means of induction.
• the tempering step in addition to hardening the raceways, has the effect of bending, warping and/or twisting the guide rails.
• a second step therefore consists in first straightening of the guide rails.
• This straightening operation is usually performed by passing the guide rails through a series of rollers which are oriented in the various useful directions.
• a third step consists in washing the guide rails, this being necessary in order to remove the residual oil arising from the tempering step.
• a fourth step consists in sandblasting the guide rails.
• a fifth step consists in boring the guide rails, necessary for providing the securing points useful for operational assembly. During this step the holes break up the continuity of the fibres, thereby altering the internal stress conditions which kept the guide rails straight. A secondary effect of boring is therefore that of causing bending again of the guide rails.
• a sixth step consists in galvanization, i.e. zinc-plating, of the guide rails, which is required in order to ensure sufficient protection against corrosion.
• a seventh step then consists in further straightening of the guide rails.
• This straightening operation may be performed by means of two alternative methods: either by means of a manual operating machine or by means of an automatic operating machine. These machines act by applying suitable bending moments to the curved sections of the guide rails.
• An eighth step consists in grinding of the raceways. During this step the surface abrasion alters the internal stress conditions which kept the guide rails straight. A secondary effect of grinding is therefore again that of causing slight bending of the guide rails.
• a ninth and final step therefore consists in further manual straightening of the guide rails.
• the object of the present invention is therefore to overcome at least partly the drawbacks mentioned above with reference to the prior art.
• one task of the present invention is to provide a method for manufacturing linear guide rails which allows a substantial reduction in the amount of work and the outlay initially required for the machining of the guide rails.
• Another task of the present invention is to provide a linear guide rail which has mechanical characteristics comparable to or superior to those of guide rails of the known type and with a lower manufacturing cost.
• FIG. 1 shows a perspective view of an embodiment of the guide rail according to the invention and the associated slider slidably mounted thereon;
• FIG. 2 shows a view, similar to that of Figure 1 , in which the slider has been removed for greater clarity;
• Figure 3 shows a side view of the guide rail according to Figure 2;
• FIG. 4 shows a cross-sectional view along the line IV-IV of Figure 3;
• Figure 5 shows a front view of the guide rail according to Figure 2 and the associated slider
• FIG. 6 illustrates in schematic form by means of a block diagram the method for obtaining the linear guide rails according to the prior art
• FIG. 7 illustrates in schematic form by means of a block diagram the method for obtaining the linear guide rails according to the invention
• FIG. 8 shows in schematic form the progression of the hardness plotted against the thickness of a raceway according to the prior art and of a raceway according to the invention
• FIG. 9 shows a perspective view of another embodiment of the guide rail according to the invention and the associated slider slidably mounted thereon;
• FIG. 10 shows a cross-sectional view of the guide rail according to Figure 9;
• FIG. 11 show, partially sectioned, a further embodiment of the guide rail according to the invention and the associated slider slidably mounted thereon in three different configurations;
• FIG. 12 shows a side view of a further embodiment of the guide rail according to the invention and the associated slider slidably mounted thereon;
• FIG. 13 shows a cross-sectional view along the line XIII-XIII in Figure 12.
• 10 denotes in its entirety a linear guide rail for moving loads according to the invention.
• the guide rail 10 is suitable for co-operating with a slider 12.
• the contact between the guide rail 10 and the slider 12 is provided by means of rolling elements 14.
• the guide 10 which is made of drawn steel, comprises raceways 16 which are suitable for making contact with the rolling elements 14, and holes 18 for operational assembly of the said guide rail 10.
• the surface of the raceways 16 is smoothed by means of abrasive tools and the surface of the guide rail 10 is treated by means of a nitriding/oxidation process and a micro-lubrication process.
• the longitudinal direction is defined as being a direction parallel to the axis of the guide rail 10. This direction is indicated by "1" in Figure 1.
• the axial direction is defined as being a direction parallel to the axis of rotation of the rolling elements 14. This direction is indicated by "a” in Figure 1.
• the perpendicular direction is defined as being a direction perpendicular to the longitudinal direction and the axial direction. This direction is indicated by "p" in Figure 1.
• the linear guide rail 10 is made of drawn steel.
• a nitriding or a case-hardening steel with a carbon content of between about 0.15% and 0.24%, with a chromium content of between about 0.95% and 1.35% and with a manganese content of between about 1.04% and 1.64% is used.
• a steel which has proved to be particularly suitable for implementing the invention is that defined as 20MnCr5 according to the Standard UNI EN ISO
• the single guide rail 10 has an overall C-shaped cross-section; the slider 12 is designed to be seated inside the “C” and has wheels which rest on the two flanges of the "C".
• the wheeled slider 12 may perform a travel stroke along the guide rail 10, which is not predetermined in terms of length.
• the single guide rail 10 has an overall C-shaped cross-section; the slider 12 is designed to be seated inside the "C” and has two series of balls which are suitably constrained inside a cage 20 and which rest on the two flanges of the "C".
• the cage 20 and the balls move along the guide rail 10 together with the slider 12, travelling along half the distance travelled by the latter.
• the balls travel, in a manner known per se, along closed paths inside the slider 12.
• the ball-mounted slider 12 may perform a travel stroke along the guide rail 10, which is not predetermined in terms of length.
• the slider 12 also comprises raceways for the balls.
• raceways of the slider may be advantageously manufactured in accordance with the teachings of the method according to the invention.
• the single guide 10 has an overall L-shaped cross-section; the slider 12 is designed to rest on the bulb-like end of the "L” and has wheels.
• the shape of the guide rail 10 and the slider 12 must be such that the latter is free to move in the longitudinal direction, and is constrained in the axial direction and the perpendicular direction.
• this type of constraint is ensured by the C shape of the cross-section of the guide rail 10.
• this type of constraint may be ensured by suitably mounting two L-shaped guide rails.
• the slider 12 may in turn comprise a guide rail portion on which a further slider able to support the load is mounted. This therefore produces, in a known manner, a telescopic guide rail. Both the fixed guide rail and the guide rail mounted on the slider 12 are advantageously guide rails according to the invention.
• the wheels are preferably mounted on the sliders 12 by means of rolling bearings
• the guide rail 10 comprises raceways 16 along which contact between the rolling elements 14 and the guide rail 10 occurs.
• the raceways are smoothed using abrasive tools (for example a grinding wheel) in order to reduce the friction and ensure a uniform and smooth slider movement.
• the guide rail 10 also comprises holes for operational assembly of the said guide rail.
• the holes 18 preferably have dimensions and are spaced from each other on the basis of the nominal load P which must be supported by the guide rail 10 in the perpendicular direction (see in particular Figure 5).
• the outer surface of the guide rail 10 is treated using a combined nitriding and post-oxidation process. These thermochemical treatments of the surface influence in a manner known per se the surface hardness, the wear/friction behaviour, the fatigue strength and the corrosion resistance.
• Figure 8 also shows the progression
• the guide rail 10 following the combined nitriding and post-oxidation treatments, undergoes a micro-lubrication treatment, also described below, with reference to the method for production of the guide rail 10.
• the guide rail assumes a characteristic black colour and has an increased corrosion resistance.
• the surface of the guide rail 10 is treated by means of smoothing or polishing prior to the thermochemical nitriding and post-oxidation treatments. According to these embodiments, the surface of the guide rail 10 is extremely uniform and substantially without roughness.
• the drawing, boring, smoothing and straightening steps are steps which are performed in a manner widely known per se.
• the boring, smoothing and straightening steps are performed exactly as in the method of the prior art.
• the nitriding and post-oxidation treatments are known per se, but a short explanation is necessary in order to understand the invention more fully.
• Nitriding is a method for diffusing nitrogen atoms in the surface of the metal. Molecular nitrogen is very common in nature; it is chemically inert and has dimensions too large to penetrate the crystal lattice of the metal. For this reason the various nitriding techniques are targeted at the source of the nascent atomic nitrogen.
• nitriding is a process for diffusing the nitrogen in the metal and this diffusion, once the individual atoms have penetrated the surface, continues until the temperature is sufficiently high and until the nascent atomic nitrogen is supplied on the surface.
• a surface layer with a thickness of between about 15 ⁇ m and 30 ⁇ m and a deeper layer.
• the surface layer also called white layer
• the deeper layer is called the diffusion layer and is that where the nitrogen is diffused in the crystal lattice and gives the steel its most interesting properties.
• Various nitriding methods are known and used on an industrial scale:
• the gas nitriding method may be controlled conventionally by controlling the degree of dissociation of the ammonia or, preferably, by means of more efficient control of the nitriding potential (Kn).
• the nitriding treatment of the latter type is that which has proved to be most suitable for implementing the invention.
• a treatment of this type was developed and defined by Nitrex Metal Technologies Inc. of Burlington, Ontario, Canada. At present this treatment is commercially available under the name of Nitreg ® .
• the exact understanding and application of the principles correlating the nitriding potential (Kn), temperature and treatment time form the basis of the Nitreg ® technology.
• the progression of the value HRC Rockwell C-scale Hardness
• tempering does not have any effect on the skin and on the surface layers of the steel, owing to the dispersion of the carbon in the environment which occurs during drawing.
• the hardness provided by nitriding is instead greater on the skin and then gradually decreases across the diffusion layer.
• the effect of the two nitriding treatments is however comparable, because the optimum hardness for use considered here is about 55 HRC at a depth of about 0.25 mm.
• the nitriding treatment is followed by an oxidation treatment.
• Post-oxidation This treatment is referred to here as "post-oxidation", indicating that it is performed immediately after nitriding in accordance with parameters which are well defined in advance. The person skilled in the art will therefore understand that this treatment does not resemble in any way other spontaneous oxidation phenomena which may arise during the working life of any guide rail. Post-oxidation tends to convert the outermost part (3-5 microns of thickness) of the white layer resulting from nitriding into a complex spinel structure. This structure consists mainly of iron oxide of the type Fe 3 O 4 (also called magnetite). This post-oxidation treatment has the effect of improving the corrosion and wear resistance and decreasing the friction coefficient. Alongside these mechanical effects, a dark or black characteristic finish is obtained.
• a post-oxidation treatment which is suitable for implementing the invention is that developed and defined by Nitrex Metal Technologies Inc. of Burlington,
• a first combined nitriding and post-oxidation treatment suitable for the invention was developed and defined by Nitrex Metal Technologies Inc.; this treatment is commercially available under the name of Nitreg ® -ONC ® .
• a second combined nitriding and post-oxidation treatment suitable for the invention was developed and defined by TTN S.p.A. of Nerviano (MI), Italy; this treatment is commercially available under the name of Nipre .
• Nipre methods have an excellent behaviour during salt mist corrosion tests (for example, in accordance with the standard UNI EN ISO 9227 or the standard ASTM Bl 17). Samples of the guide rail 10 according to the invention took 320 hours (ISO test 9227) to develop the first rust spot. The protection provided by post-oxidation is therefore greater than that provided by other treatments such chrome-plating, nickel-plating or zinc-plating.
• the post-oxidation treatment does not alter significantly the characteristics imparted to the steel by the previous nitriding treatment.
• the ONC ® treatment does not alter significantly the characteristics imparted to the steel by the previous Nitreg ® nitriding treatment.
• the Nitreg ® , ONC ® and Nipre ® treatments are technologies which are cleaner than other comparable technologies such as salt-bath nitriding or chrome-plating.
• the method for manufacturing a linear guide rail 10 according to the invention also comprises a step involving micro-impregnation of the surface layers with a lubricating and anti-corrosive substance.
• This substance may be for example a mineral oil with anti-oxidant additives.
• the method also comprises, prior to the thermochemical nitriding and post-oxidation treatments, a step involving smoothing or polishing of the surface of the guide rail 10.
• This step may be completed using abrasive tools (for example a brush).
• thermochemical treatments are able to act on a surface which is extremely uniform and substantially free of roughness. It has in fact been noted that the corrosion preferably starts where there is even the slightest roughness on the surface. With this last step of the method it is therefore possible to obtain guide rails which are even more resistant to corrosion.
• samples of the guide rail 10 according to the invention which have undergone polishing prior to nitriding or post-oxidation, took more than 500 hours (ISO test 9227) to develop the first rust spot.
• the method according to the invention is able to obtain a linear guide rail 10 with characteristics which are superior to those of the guide rails of the known type. Moreover, with the method according to the invention, it is possible to produce the guide rail 10 very rapidly and at a lower initial outlay. In particular, the method according to the invention fully exploits the fact that the starting article (drawn product) is already sufficiently straight to be able to perform in an optimum manner the function of a linear guide rail. With the method according to the invention it is possible to exploit this characteristic feature of the drawn product such that all the intermediate straightening steps required in the known methods are avoided. The single final straightening operation is able to ensure an optimum quality of guide rail 10 according to the invention.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Heat Treatment Of Articles (AREA)
• Bearings For Parts Moving Linearly (AREA)
• Diaphragms For Electromechanical Transducers (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)

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• 2008
  • 2008-11-18 IT ITMI2008A002050A patent/IT1391946B1/it active
• 2009
  • 2009-11-12 EP EP09760609.9A patent/EP2347141B1/en active Active
  • 2009-11-12 WO PCT/IB2009/055036 patent/WO2010058331A1/en active Application Filing
  • 2009-11-12 JP JP2011536975A patent/JP2012509447A/ja active Pending
  • 2009-11-12 CN CN2009801449496A patent/CN102209855A/zh active Pending
  • 2009-11-12 US US13/126,930 patent/US20110200276A1/en not_active Abandoned
• 2014
  • 2014-02-28 JP JP2014001054U patent/JP3190672U/ja not_active Expired - Lifetime

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