US3128638A - Adjustable cam - Google Patents

Description

J. L. KING ADJUSTABLE CAM April 14, 1964 Filed Aug. 15, 1961 INVENTOR.

JAMES L. KING ATTORNEYS United States Patent 3,128,638 ADJUSTABLE CAM James .L. .K-ing, Sudbury, Mass, .assignor to Acton Lahoratories,lne., a. corporation of Massachusetts Filed Aug. 15, 19.61, Ser. No. 131,579 -7' Claims. '(Cl. 7.4-568) Thisinvention relates: to timing cams and more particularly to ,a new and improved adjustable timing cam assembly'for use in actuating electrical switches at precise time intervals.

The primary object of the present invention is to ,provide a new and improved timing cam for an electric switch which permits precision adjustment of the time -at which the switch is actuated.

Afurther primary object of'the present invention is to provide anadjustable timing cam for an electric switch which permits precisionvariation of the-length of time ;during which the switch is .held operative or inoperative by the cam.

:,Still another'primary object of the present invention is .to provide an-adjustable timing cam which will not shift ifrom its set position-under vibration and'yet may be reset easily by a simple conventional tool.

.Amorespecific object of the present invention is to provide a timing cam assembly which-comprises a first ihlll) unit adapted to be adjustably' mounted'on a rotating shaft, and a second cam memberretained by thehub .unitandselec'tively rotatable relative to the hub unit and .the shaft, the cam member being rotatable by means of .a worm which is rotatably'captivated within the'hub 'unit .in a manner such that it is substantially-free of axial movement.

Still a further objectof the present invention is to provide .a cam assembly-as described in the foregoing statement of object, which further includes a second cam'member .supportedbythe first cam member and rotatable rela- -tive to the hub-unit and the first cam member by-aseccation when considered together with theaccompanying "drawings wherein:

FIG. '1 is a perspective view of a cam assembly embodying-the present invention mounted -on a supporting rotatable shaft;

FIG. 2 is a perspective view of the same cam assembly and supporting shafttaken'fromanothertvantage point;

FIG. 3 is a longitudinalsectional view of the structure shown in FIGURES'l and 2;

FIG; 4 isa-cross-sectionai-View taken along line'44 of FIG. 3; and

FIG. 5 is an cxplodedvviewshowing the various components of the cam assembly.

The illustrated cam assembly comprises a hub unit which is made up of a hub member 2 and a surrounding sleeve 4. The hub member 2 is provided with a central bore to accommodate a supporting shaft 6 which is driven by motor means (not shown). The central bore of hub member 2 is enlarged as shown at 8 so as to accommodate one of the hubs 10 of a dual-hub cam member 12 having a central bore 14. The opposite hub portion of cam member 12 is illustrated at 16. Hub portion 10 is provided with a peripheral, helically threaded groove 18 sized to accept and mesh with a worm 20 which is captivated within bore 22 formed in the hub member 2. Preferably, worm 20 has an Allen type head as shown, but it may also have a kerfed head. It is to be noted that the bore 22' partially intersects the enlarged portion 3,128,638 Patented Apr. 14,1964

8 of the central bore of hub member 2 and .also that it is reduced in diameter as indicated at 24 so as to form a shoulder 26 against whichthehead of the worm can abut. Axial movement of the screw away from shoulder .26 is prevented by a plug 30 of a suitable plastic, or a metallic cement which is forced into the open end of bore 22. Plug 30 is retained in place by the surrounding sleeve 4 which is force fitted ontohub member 2. In this connection it is to be observed that the sleeve 4 has a hole 34 which is aligned with the restricted section 24 of the bore 22, so as to permit insertion of van Allen wrench or a screwdriver, asthe case may be, forrotating the worm. It is to be observed further that hub memberlZ' and its companionsleeve 4 are provided .with matching radial bores 36 and 38,to accommodate a set screw 40. .The latter is used to secure the hub unit to shaftf6.

The peripheral edge of cam member 12 is provided with-a camconfiguration. In the. present-case it is circular except for a depression 44. Alternatively, it may be ellipticalor have aseries of depressions orv projections,

depending uponthe requirements to be satisfied. The edges of the cam member may be varied in-width to the extent necessary to assure good contact with the actuatfling memberof the switch. In most cases the switch actuating member will bea button ora spring-biased lever. Preferably the cam element 12 is formed of nylon or some other strong,,hard.wearing, easilymachinable material which can be rotated relative adjacent members without any substantial friction.

Rotation of worm 20.will cause cam member 12 to rotate relative to the shaft 6. In this connection, it is to be observed that the center bore 14 .of cam. member 12 is slightly; larger than shaft 6rso as .to permit the cam to rotate freely on the shaft. Atthe same time, however,

the spacing between the bore, 14 and theshaft ,6 is sufiiciently small as to permit the shaft to provide support for the cam element.

Also supported by the cam element 12 is a second cam member 48 having anedge depressiont50. Cam member 48 has a hub 52 and a center hole 54 which is sized to accept hub16 ofcammember 12. I-Iub16 hasa peripheral, helically threaded .groove .56 which. is the-same as groove 18. Groove 56 accepts a second worm 58 which .ispositioned in a bore60 formed in .cam member. 48. Al-

though not shown in detail, it is .to. be understood that bore 60 is the same asbore 22 andworm58is captivated .by a plug the same as plug30. Surrounding hub 52 of primary function is to retainplug 3t) and its counterpart'for worm58 so to prevent axial movement of worms 20 and.5;8.

It is believed to be apparent that. rotation of. worm .53

will causecam member 48 to rotate relative tocam member 12in the same way that cam member 12 will rotate relative to hub member 2 and shaft 6 when worm 20 is turned. When depressions 44 and 50 are exactly in line, the two cam members will function as if only one of them were present. However, if one cam member is rotated slightly so that depressions 44 and 50 partially overlap, the dwell time will be changed according to the amount of overlap. In addition to permitting adjustment of the length of dwell time, the foregoing construction permits adjustment of the start of the dwell period by rotation of cam member 2. In other words, actuation of the switch associated with the cam assembly can be advanced or retarded by turning worm 20 and the duration of the period of actuation can be increased or decreased by turning worm 58.

A further advantage of the invention is that the second cam member 48 may be omitted without aifecting the function or design of cam member 12. However, if cam member 48 is omitted, it may be desirable to eliminate hub 16 of cam member 12'.

It is to be noted also that although cam members 12 and 48 are constructed so as to lie against one another so as to function as a single adjustable cam, it is possible also to form either cam member so that their edges are spaced axially a sufficient distance to function as two separate cams separately adjustable relative to shaft 6.

A most significant feature of the invention is the simplified manner of mounting the worms 20 and 58. Forming the bores 22 and 60 and their restricted extensions is easily accomplished using conventional tools. Also a simple matter is insertion of the plugs 30 and press-fitting of sleeves 4 and 62. Use of the sleeves assures that the plugs will not come out or shift under vibration, heat, or pressure. The plugs can be made to exert an axial force on the worms which not only prevents them from moving axially but also helps restrain them against rotation. Hence, the cam members will be held firm in their set positions and will not shift or chatter under vibration or sudden shock. Lack of chatter on the part of the cam members is important where precision timing is required, as, for example, in airborne telemetry and control systems.

Another feature of the invention is ease of assembly due to the fact that cam member 12 is made of a resilient plastic such as nylon. Cam member 12 is snapped into place in hub member 2, the former compressing sufficiently so as to snap over worm 20. Cam member 48 also is snapped over hub 16 of cam member 12. In the latter case hub 16 yields sufliciently to allow worm 58 to be snapped into groove 56. Once assembled, the members cannot be separated except by deliberately prying them apart with a sharp tool.

Obviously, many modifications and variations of the present invention are possible in the light of the foregoing teachings. It is to be understood, therefore, that the invention is not limited in its application to the details of construction and arrangement of parts specifically described or illustrated, and that within the scope of the appended claims it may be practiced otherwise than as specifically described or illustrated.

What is claimed is:

1. A timing cam assembly comprising a hub member, means for securing said hub member to a rotatable shaft, a first cam member rotatably supported by said hub member, means for controllably rotating and locking said first cam member relative to said hub member, a second cam member rotatably mounted on said first cam member, and means for controllably rotating and locking said second cam member relative to said first cam member.

2. A timing cam assembly as defined by claim 1 wherein said means for rotating and locking said first cam member comprises a helical gear on said first cam member and a worm carried by said hub member which meshes with said gear.

3. A timing cam assembly as defined by claim 1 wherein said means for rotating and locking said second cam member comprises a second helical gear on said first snugly within said first section, a transversely extending bore in said hub member, a worm rotatably disposed in said transversely extending bore, a sleeve surrounding said hub member for preventing axial movement of said worm, and a cam member having a hub disposed within said second section of said axial bore, said hub having a peripheral groove with a helical thread formed therein, said worm positioned in said groove in meshing engagement with said helical thread, whereby as said worm is rotated said cam member will rotate about its center axis relative to said hub member.

6. A timing cam assembly comprising a hub member having an axial bore, said axial bore having a first section of relatively small diameter for snugly receiving a shaft and a second section of relatively large diameter, means for securing said hub member to a shaft fitting snugly within said first section, a first transversely extending bore in said hub member, a first worm rotatably disposed in said first transversely extending bore, means preventing axial movement of said first Worm, a first cam member having a first hub disposed within said second section of said axial bore, a said first hub having a first peripheral groove with a helical thread formed therein, said first worm positioned in said first groove in meshing engagement with the helical thread therein, whereby as said first worm is rotated said first cam member will rotate about its center axis relative to said hub member, a second hub on said first cam member having a second peripheral groove with a helical thread formed therein, a second cam member rotatably mounted on said second hub, said second cam member having a second transverse- .ly extending bore, a second worm rotatably disposed in said second bore in meshing engagement with the helical thread in said second helical groove, and means preventing axial movement of said second worm, whereby as said second worm is rotated said second cam member ,will rotate relative to said first cam member.

7. A timing cam assembly as defined by claim 6 wherein said second cam member has a hub portion with said second worm located therein, and said means for preventing axial movement of said second worm comprises a sleeve surrounding said hub portion.

References Cited in the file of this patent UNITED STATES PATENTS 2,857,784 Brailsford Oct. 28, 1958 FOREIGN PATENTS 3,659 Netherlands Sept. 5, 1919

Claims (1)

1. A TIMING CAM ASSEMBLY COMPRISING A HUB MEMBER, MEANS FOR SECURING SAID HUB MEMBER TO A ROTATABLE SHAFT, A FIRST CAM MEMBER ROTATABLY SUPPORTED BY SAID HUB MEMBER, MEANS FOR CONTROLLABLY ROTATING AND LOCKING SAID FIRST CAM MEMBER RELATIVE TO SAID HUB MEMBER, A SECOND CAM MEMBER ROTATABLY MOUNTED ON SAID FIRST CAM MEMBER, AND MEANS FOR CONTROLLABLY ROTATING AND LOCKING SAID SECOND CAM MEMBER RELATIVE TO SAID FIRST CAM MEMBER.

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