US3579933A - Method of manufacturing a cam for use in an ignition distributor - Google Patents

Method of manufacturing a cam for use in an ignition distributor Download PDF

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Publication number
US3579933A
US3579933A US789504A US3579933DA US3579933A US 3579933 A US3579933 A US 3579933A US 789504 A US789504 A US 789504A US 3579933D A US3579933D A US 3579933DA US 3579933 A US3579933 A US 3579933A
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US
United States
Prior art keywords
cam
asperities
sharp edges
container
grinding
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US789504A
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English (en)
Inventor
John Snell
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ZF International UK Ltd
Original Assignee
Lucas Industries Ltd
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Filing date
Publication date
Application filed by Lucas Industries Ltd filed Critical Lucas Industries Ltd
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Publication of US3579933A publication Critical patent/US3579933A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B31/00—Machines or devices designed for polishing or abrading surfaces on work by means of tumbling apparatus or other apparatus in which the work and/or the abrasive material is loose; Accessories therefor
    • B24B31/06—Machines or devices designed for polishing or abrading surfaces on work by means of tumbling apparatus or other apparatus in which the work and/or the abrasive material is loose; Accessories therefor involving oscillating or vibrating containers
    • B24B31/073—Machines or devices designed for polishing or abrading surfaces on work by means of tumbling apparatus or other apparatus in which the work and/or the abrasive material is loose; Accessories therefor involving oscillating or vibrating containers involving a bowl being ring- or spiral-shaped

Definitions

  • This invention relates to cams for ignition distributors of the kind including a shaft adapted to be driven by the engine of a vehicle with which the distributor is associated, the cam being rotatable with the shaft, and a cam follower which engages said cam to effect opening and closing of a pair of contacts.
  • a ground cam is inspected under a microscope, it is found to consist of a large number of sharp edged asperities of varying heights between which are defined channels. These channels store the lubricant in use, and if the cam is ground excessively, the channels; gradually become smaller, and so that amount of lubricant that can be stored is considerably reduced. Quite apart from these two points, it has been found that the major contributory factor to the wear of the cam follower is the sharp edges of the asperities, which act as cutting edges in a manner somewhat analogous to the action of a coal cutter pick. Grinding of the cam removes some asperities, but leaves other asperities with their sharp edges which can still cause damage. Moreover, the grinding operation at the same time reduces the volume of the channels, so that less lubricant is stored, which worsens the problem.
  • the present invention is based on the realization that in order to reduce the wear rate the sharp edges of the asperities must be removed without substantially reducing the total volume of the channels, and resides in a method of forming a cam, comprising grinding the cam to the desired profile, the grinding operation leaving the cam surface with sharp edged asperities defining therebetween channels which in use store lubricant, placing the cam in a container with abrasive particles, and moving the container so that the particles collide with the cam surface and round off the sharp edges of the asperities without removing the asperities.
  • FIGS. 2 and 3 respectively are micrographic representations of the surface of a cam, FIG. 2 showing the cam after it has been ground to the desired profile but before the finishing operation, and FIG. 3 showing the same cam after the finishing operation.
  • FIG. 1 does show the form of a suitable machine manufactured and sold by William Boulton Limited under the trade name Autoscroll.
  • This machine comprises a container in the form of an annular bowl ll of generally semicircular cross section which is filled with ceramic particles in the form of prisms.
  • the bowl is mounted on a plurality of springs (not shown) and is caused to vibrate in such a manner that the ceramic prisms, which surround the cams, progress around the bowl from the lower portion 12 thereof in a substantially toroidal helical path towards the outlet 13 from the bowl.
  • the motion of the ceramic prisms is not a smooth progression, but a series of short jumps so that the prisms are constantly colliding with the cam shafts.
  • a small amount of soapy water, sufficient only to wet all the ceramic prisms and the cam shafts, is added to the bowl to aid removal of particles of metal abraded from the cam shafts by the ceramic prisms.
  • the grinding process leaves the surface of the cam with numerous sharp edges asperities between which are defined channels in which lubricant will be stored in use. These asperities are clearly seen in FIG. 2.
  • the finishing operation does not remove the asperities, but rounds their sharp edges as can be seen in FIG. 3.
  • the finishing operation produces a cam the profile of which is substantially unchanged by the finishing operation, and in which the total volume of the channels is substantially unaltered. Nevertheless, all the sharp edges have been rounded, so that there will be considerably less wear on the cam follower when the cam is in use.
  • the surface finish which is produced by the original grinding operation can of course be controlled, and the exact finish will depend on the particular application and will be obvious to an expert.
  • the length of the finishing operation will depend on the nature of the cam required for a particular operation, but can readily be deduced by an expert given the knowledge imparted by the present invention, which is that is is necessary to round the sharp edges without substantially reducing the volume of the channels.
  • the life of the associated cam follower can be improved by subjecting the cam to the finishing operation described. Even if the cam is ground to a finish which would be regarded as totally unsatisfactory, the finishing operation will improve the cam so much that it may be satisfactory.
  • a cam for use with a conventional cam follower manufactured from the material sold under the trademark Tufnol is usually thought to be reasonably satisfactory with a surface finish between 5 microinches and 32 microinches, but a cam ground to only 8 microinches is satisfactory if subjected to the finishing operation described using the apparatus described above for a period of about 2 hours.
  • a method of manufacturing a cam for use in an ignition distributor comprising grinding the cam to the desired profile, the grinding operation leaving the cam surface with sharp edges asperities defining therebetween channels which in use store lubricant, placing the cam in a container with abrasive particles and moving the container so that the particles collide with the cam surface and round off the sharp edges of the asperities without removing the asperities.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Grinding And Polishing Of Tertiary Curved Surfaces And Surfaces With Complex Shapes (AREA)
  • Valve-Gear Or Valve Arrangements (AREA)
  • Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
  • Ignition Installations For Internal Combustion Engines (AREA)
  • Gears, Cams (AREA)
US789504A 1968-01-08 1969-01-07 Method of manufacturing a cam for use in an ignition distributor Expired - Lifetime US3579933A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB981/68A GB1240111A (en) 1968-01-08 1968-01-08 Ignition distributors

Publications (1)

Publication Number Publication Date
US3579933A true US3579933A (en) 1971-05-25

Family

ID=9713929

Family Applications (1)

Application Number Title Priority Date Filing Date
US789504A Expired - Lifetime US3579933A (en) 1968-01-08 1969-01-07 Method of manufacturing a cam for use in an ignition distributor

Country Status (6)

Country Link
US (1) US3579933A (US07202987-20070410-C00007.png)
JP (1) JPS4812015B1 (US07202987-20070410-C00007.png)
DE (1) DE1900662A1 (US07202987-20070410-C00007.png)
ES (1) ES362605A1 (US07202987-20070410-C00007.png)
FR (1) FR1600559A (US07202987-20070410-C00007.png)
GB (1) GB1240111A (US07202987-20070410-C00007.png)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5643054A (en) * 1995-04-07 1997-07-01 Ina Walzlager Schaeffler Kg Machine part with improved surface texture for rolling contact and/or sliding contact
US5829131A (en) * 1997-11-21 1998-11-03 Chrysler Corporation Method of making camshaft lobes
US20170259393A1 (en) * 2016-03-11 2017-09-14 Tipton Corp. Surface treatment method for metal parts

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ATE2878T1 (de) * 1979-11-17 1983-04-15 Carl Kurt Walther Gmbh & Co. Kg Ringtrogfoermiger vibrations-scheuerbehaelter.
EP0029897B1 (de) * 1979-11-17 1983-03-30 Carl Kurt Walther GmbH & Co. KG Ringtrogförmiger Vibrations-Scheuerbehälter
JPS62144909U (US07202987-20070410-C00007.png) * 1986-03-05 1987-09-12

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2548264A (en) * 1948-03-16 1951-04-10 Bendix Aviat Corp Tumbling process for bearing assemblies
US2932205A (en) * 1957-07-31 1960-04-12 C H Keesling Power operated tool attachment for electric drills and the like
US3482357A (en) * 1965-10-27 1969-12-09 Fujitsu Ltd Automatically controlled cam grinding system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2548264A (en) * 1948-03-16 1951-04-10 Bendix Aviat Corp Tumbling process for bearing assemblies
US2932205A (en) * 1957-07-31 1960-04-12 C H Keesling Power operated tool attachment for electric drills and the like
US3482357A (en) * 1965-10-27 1969-12-09 Fujitsu Ltd Automatically controlled cam grinding system

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5643054A (en) * 1995-04-07 1997-07-01 Ina Walzlager Schaeffler Kg Machine part with improved surface texture for rolling contact and/or sliding contact
US5829131A (en) * 1997-11-21 1998-11-03 Chrysler Corporation Method of making camshaft lobes
US20170259393A1 (en) * 2016-03-11 2017-09-14 Tipton Corp. Surface treatment method for metal parts
US10086490B2 (en) * 2016-03-11 2018-10-02 Tipton Corp. Surface treatment method for metal parts

Also Published As

Publication number Publication date
JPS4812015B1 (US07202987-20070410-C00007.png) 1973-04-17
GB1240111A (en) 1971-07-21
DE1900662A1 (de) 1969-09-04
ES362605A1 (es) 1970-09-16
FR1600559A (US07202987-20070410-C00007.png) 1970-07-27

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