US1294125A - Machine element. - Google Patents

Description

;n.r. LEPLEY.

MACHINE ELEMENT. APPLICATION FILED SEPT- 19. 1917.

1294,1125 Patented Feb. 11,1919.

Witnesses TTNTTE STA us rarnnr orrion 1 "DANIEL r. LEPLEY, or CONNELLSVILLE, PENNSYLVANIA.

MACHINE ELEMENT.

Specification of Letters Patent.

Patented Feb. 11, 191

Application filed September 19, 1917. Serial No. 192,165.

, and useful Machine Element, of which the following 'is a specification.

This invention relates to a machine element for converting rotary motion into intermittent right line movement, one of the objects of the invention being to provide means wherebya rack bar can be actuated intermittently in either direction by a rotating cam, which cam operates at all times to hold the rack againstany movement other than that imparted to it by the cam.

A further object is to provide a cam of novel construction combined with a rack having teeth'of novel form designed to cooperate with the cam.

Another object is to provide a machine element presenting at all times extensive, flat contacting surfaces between the two operating members, thereby to reduce wear and lost motion during the. operation of the device in either direction.

With the. foregoing and other objects in view which will appear as the description proceeds the invention resides in the combination and arrangement of parts and in the details of construction hereinafter described and claimed, it being understood that changes in the precise embodiment of the invention can be made within the scope of what is claimed without departing from the spirit of the invention.

In the accompanying drawings z- Figure 1 is a plan view of the mechanism constituting the present invention.

Fig. 2 is a section on line 22 Fig. 1, the rack being shown in elevation.

Fig. 3 is a section on line 33 Fig. 1.

Referring to the figures by characters of reference, 1 designates a rack bar provided, on one face, with a longitudinal series of similar diamond shaped teeth 2. These teeth are preferably formed by cutting transverse grooves in one face of the bar and then cutting oblique grooves which intersect the transverse grooves.

The cam which cooperates with the rack consists of a cylinder 3 having parallel annular grooves 4 in its periphery which communicate at one point through an obliquely opposed groove 5, the angle of which is the v the rack.

same as that of the oblique grooves cut in A metal strip 6 is seated in the grooves 4c and 5, the cndsof this metal strip being secured in the respective grooves 4:

and lapping to a slight extent. The ends of the strips can be held by rivets as shown at 7 in Figs. :2 and 3 and thus it is possible readily to form a cam the end portions of .which lie in parallel planes while the middle portion is olfset obliquely and pitched to correspond with the oblique faces of the teeth 2.

Obviously, the cam can be constructed in any other way desired although it has been found most practical to make it in the manner set forth.

When the cam is assembled with the rack, some portion of the thread formed by the projecting portion of the metal strip 6 will fit snugly between two of the teeth on the rack, thus holding the rack against longitudinal movement, The rack will be so held during the rotation of the cylinder 3 until the obliquely disposed portion of the thread comes between the teeth whereupon a longi- 'tudinal thrust will be transmitted by said obliquely disposed portion against the oblique face of one of the adjoining teeth 2, whereupon the rack bar will be shifted longitudinally for the distance of one tooth after which it again will be held against longitudinal movement in either direction until the completion of another revolution of the cam. By pitching the thread and teeth as shown, the same action will occur when the rotation of the cam is reversed. Thus by means of this mechanism continuous rotary motion can be converted into intermittent right line motion, it being possible to shift the rack bar in either direction depending on the direction of rotation of the cam. Furthermore, this mechanism is advantageous because the rack is held against movement except while being positively shifted by the oblique portion of the thread on the cam.

The mechanism herein described, while useful wherever it is desired to convert continuous rotary motion into intermittent right line movement, is especially designed for use in producing a step by step movement of a master electric controller of the drum type such as used, for example, in connection with hoisting apparatus for mines as disclosed in a copending application filed by me. The

mechanism described will produce the quick intermittent movement from point to point of a controller necessary to preventshort cir cuiting and burning out of the controller, it having been found impracticable to use, for the purpose of actuating an electric control ler, any mechanism which will shift the con troller gradually toward and from the neutral point. By providing mechanism such as described the quick intermittent movement can be produced in either direction, it thus being possibleto use the mechanism in connection with a reversible electric controller, in which event the same desirable results of quick step by step movement will be produced under both conditions of the controller. v

The present apparatus is also advantageous because it permits a very rapid movement of the parts, but as the thread of the cam fits snugly at all times between the teeth, the rack will not be impelled forwardly faster than it should go, as a result of the impulse imparted to it by the rapidly rotating cam, but will always be held under restraint and can only move a distance equal to the pitch of one tooth during each rotation of the cam. The cam and rack are locked together at all times and the rack is thus incapable of any right line movement unless the cam is rotating, and then only during a portion of such rotation. By providing the peculiarly shaped teeth on the rack the same are not only caused to fit snugly against the thread of the cam but likewise present the maximum bearing area thereto, thereby greatly increasing the strength and durability of the mechanism.

What is claimed is:

1, Mechanism for converting continuous rotary motion into intermittent right line movement, including a revoluble element having a thread extending once therearound, said thread having an obliquely disposed portion diametrically opposite the end portions,those portions of the thread between the oblique portion and the ends occupying parallel planes perpendicular to the axis of rotation of the revoluble' element, a bar mounted for reciprocation, and teeth upon the bar and constantly engaged by the thread, the shortest distance between the teeth being equal to the thickness of all portions ofthe thread.

2. The combination with a rack bar, of a cam including a cylinder having parallel annular grooves communicating through an oblique groove, a strip secured at its ends within the respective annular grooves, and having its middle portion seated in the oblique groove, the end portions of the strip lapping and all portions of said strip projecting beyond the face of the cylinder for engagement with the teeth of the rack bar.

In testimony that I claim the foregoing as my own, I have hereto aflixed my signature in the presence of two witnesses.

DANIEL F. LEPLEY.

Witnesses:

Ivy E. SIMPsO-N, P. A. RocKELLI.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

' Washington, D. G.

Images